  (c) The Computer Language Company Inc. 1981-1995
   All rights reserved. Ver. 8.1, 1st Quarter 1995


       Updated Quarterly.  Look up Order Form.






             Be sure to look up Lessons.




  THIS SOFTWARE IS NOT SHAREWARE! ͻ
    It is licensed for use on a single machine.  
    For multiuser licenses, call 215/297-5999.   
 ͼ








A/D converter
(Analog to Digital Converter)  A device that
converts continuously varying analog signals from
instruments that monitor such conditions as
movement, temperature, sound, etc., into binary
code for the computer.  It may be contained on a
single chip or can be one circuit within a chip.
See modem and codec.  Contrast with D/A converter.



A/UX
Apple's version of UNIX for the Macintosh.  It is
based on AT&T's UNIX System V with Berkeley
extensions.



A20
The address line in a PC that points beyond one
megabyte.  For downward compatibility with
8086/8088s, this line is gated in 286s and up and
is controlled by circuitry on the motherboard.
When disabled, it keeps the machine in Real Mode
(under 1MB).  When enabled, the CPU can address
beyond 1MB (Protected Mode).

   The HMA (high memory area) can also be accessed
in Real Mode when this line is turned on.  There
are 32 address lines on a 386DX (A0-A31), 24 on a
386SX and 286 (A0-A23).



A:
The designation for the first floppy disk drive in
a PC.



AA
(Auto Answer)  See modem.



AAUI
(Apple AUI)  Apple's version of the Ethernet AUI
connector.



ABC
(Atanasoff-Berry Computer)  The first electronic
digital computer.  Completed in 1942 by Iowa State
Professor John Atanasoff and graduate student
Clifford Berry, it embodied the input, memory and
arithmetic unit of future computers.

   John Mauchly, cobuilder of the ENIAC, visited
Atanasoff in 1940 and corresponded with him.
Although Eckert and Mauchly are considered the
creators of the first electronic digital computer,
Atanasoff and Berry are acknowledged contributors.

   In 1990, nearly 50 years after his invention,
87-year-old Atanasoff was awarded the National
Medal of Technology.



ABCD
See CompTIA.



abend
(ABnormal END)  Also called a crash or bomb, it
occurs when the computer is presented with
instructions or data it cannot recognize or the
program is reaching beyond its protective boundary.
It is the result of erroneous software logic or
hardware failure.

   When the abend occurs, if the program is running
in a personal computer under a single-task (one
program at a time) operating system, such as DOS,
the computer locks up and has to be rebooted.
Multitasking operating systems with memory
protection halt the offending program allowing
remaining programs to continue.

   If you consider what goes on inside a computer,
you might wonder why it doesn't crash more often.
A large mainframe's memory can easily contain over
one billion storage cells (bits).  Within every
second, millions of these cells change their state
from uncharged to charged to uncharged.  If only
one cell fails, the computer can abend.



ABI
(Application Binary Interface)  A specification for
a particular hardware platform and operating
system.  It is one step beyond the application
program interface (API), which defines the calls
from the application to the operating system.  The
ABI defines the API plus the machine language for a
particular CPU family.  An API does not ensure
runtime compatibility, but an ABI does, because it
defines the machine language, or runtime, format.

   For example, the PowerOpen Environment is an ABI
that specifies the machine language of the PowerPC
CPU family and the function calls made by the
application to a PowerOpen-compliant operating
system.



abort
(1) To exit a function or application without
saving any data that has been changed.

(2) To stop a transmission.



Abort, Retry...
See DOS error messages.



About this database
In 1981, this lexicon started out in print as "The
Computer Glossary," a 330-term compendium to Alan
Freedman's computer literacy seminars.  By 1989,
the 4th edition contained 3,500 terms and 400
illustrations and won the "Best Reference Book of
the Year" award from Computer Book Review.  In
March of 1990, the Glossary was introduced for the
first time as software, with a DOS version for PCs
and a HyperCard version for Macs.  The Windows
version was introduced in July of 1991.

   The current book is the 480-page 7th edition
with more than 6,000 terms (copyright 1995).  An
expanded 900-page book with 800 illustrations,
entitled "Computer Desktop Encyclopedia," will be
available in late 1995.  Both are available at
major bookstores (AMACOM is the publisher) and
direct from The Computer Language Company (look up
Order Form).

   This disk version has more than 7,500 terms and
is updated quarterly.  If you have a single user
license, you can upgrade by mail (look up Order
Form) or call The Computer Language Company.  If
you are running under a multiple user license--
your screen says "Licensed to...", contact your
information systems department for upgrading.



            A Note from the Author
My goal is to keep this database informative,
interesting, accurate and timely.  I invite your
suggestions for enhancing existing terms as well as
for new terms or subjects.  Thanks for your help.

                  Alan Freedman
          THE COMPUTER LANGUAGE COMPANY
              5521 State Park Road
          Point Pleasant, PA 18950-0265
                Tel: 215/297-8082
                FAX: 215/297-8424
           Internet: 71020.1560@compuserve.com


                  Acknowledgments
It would be impossible to create this database
without the help of hundreds of technical engineers
and public relations people who work for the
hardware and software companies.  In addition, many
readers have contributed terms, suggestions and
comments.  To all of you, thank you for your
assistance.

   There are some people that have made important
contributions throughout the history of this
project, and I would like to acknowledge each of
them.  Many thanks to Joel Orr, Orr Associates,
Stephen C. Diascro, Jr., Tandy Corporation,
Margaret A. Herrick, Margann Associates, Leonard
Mikolajczak, DACOM, Paul T. Bergevin, IBM, Garry
Dawson, Hewlett-Packard, Jagdish Dalal, Unisys,
Pamela J. Brannan, Hayes Microcomputer Products,
Walter A. Levy, Edgewood Computer Associates, Mark
J. E. Shapiro, Network in a Box, Joan Zachary,
Cuttalossa Training Partners, Stephen Slade, Yale
University, Robert F. Williams, Cohasset
Associates, and the staff at Black Box Corporation,
including Pat Flanigan, Mark Bennett, Mike Ramos,
Larry Clark, Randy Morse and Bill Ihrig.

   There are some people, however, who have made
significant contributions, but more than that, they
just keep on helping.  Thank you all.  Your help is
really appreciated.

       Thom Drewke, Technical Directions
       James J. Farrell, III, VLSI Technology
       Max B. Fetzer, Envirotronics
       Lynn S. Frankel, Byrd Press
       Steve Gibson, Gibson Research
       Peter Hermsen, Apple Computer
       Terry O'Donnell, Adobe Systems
       Gary Saxer, Quarterdeck Office Systems
       Jim Stroh, LXD, Inc.
       Skip Vaccarello, The Saratoga Group
       David Wallace, Dun & Bradstreet Software
       Irving L. Wieselman, Computer Printer Corp.
       Paul and Jan Witte, Originetics

   I want to thank the staff at AMACOM for all
their help with the print versions.  Special thanks
to Weldon Rackley, director, who has faithfully
supported this project since the 4th edition of the
book.  Thanks for believing in me.  Also many
thanks to Tony Vlamis, my editor, who has spent
considerable time on this endeavor, and to Steve
Arkin, marketing director, for his assistance and
inspiration.

   Last and most important, I would like to thank
Irma Lee Morrison, my wife and partner, for the
countless hours of devotion she has made to this
project.  Thank you Irmalee.  I love you dearly.





above the line
See "IBM COBOLs" in COBOL.



ABR
(AutoBaud Rate detect)  The analysis of the first
characters of a message to determine its
transmission speed and number of start and stop
bits.



absolute
In programming, a mathematical function that always
returns a positive number.  For example, ABS(25-
100) yields 75, not -75.



absolute address
An explicit identification of a memory location,
peripheral device, or location within a device.
For example, memory byte 107,443, disk drive 2 and
sector 238 are absolute addresses.  The computer
uses absolute addresses to reference memory and
peripherals.  See base address and relative
address.



absolute path
Same as full path.



absolute vector
In computer graphics, a vector with end points
designated in absolute coordinates.  Contrast with
relative vector.



absolute zero
The theoretical temperature at which molecular
activity ceases (-273.15 C, -459.67 F).



abstract data type
A user-defined data type in object-oriented
programming.  See object-oriented programming.



AC
(Alternating Current)  The common form of
electricity from power plant to home/office.  Its
direction is reversed 60 times per second in the
U.S.; 50 times in Europe.  Contrast with DC.



accelerator
A key combination used to activate a task.  See
accelerator board and graphics accelerator.



accelerator board
An add-in board that replaces the existing CPU with
a higher performance CPU.  See graphics
accelerator.



ACCELL/SQL
A fourth-generation language from Unify
Corporation, Sacramento, CA, that runs on UNIX
platforms and supports Oracle, Ingres, Informix,
Sybase and Unify databases.  Introduced in 1985 as
the Interactive Development System, it was the
first database-independent 4GL for UNIX.



acceptance test
A test performed by the end user to determine if
the system is working according to the
specifications in the contract.



access
To store data on and retrieve data from a disk or
other peripheral device.   See access arm, access
method and Microsoft Access.



access arm
The mechanical arm that moves the read/write head
across the surface of a disk similar to a tone arm
on a phonograph.  The access arm is directed by
instructions in the operating system to move the
read/write head to a specific track on the disk.
The rotation of the disk positions the read/write
head over the required sector.



access charge
The charge imposed by a communications service or
telephone company for the use of its network.



access code
(1) An identification number and/or password used
to gain access into a computer system.

(2) The number used as a prefix to a calling number
in order to gain access to a particular telephone
service.



access denied
The system is unable to retrieve the file you are
requesting.  In DOS, this error message usually
means that the file you are deleting is protected.
See DOS Attrib.



access line
The line from a customer site to a telephone
company's central office.



access method
A software routine that is part of the operating
system or network control program which performs
the storing/retrieving or transmitting/receiving of
data.  It is also responsible for detecting a bad
transfer of data caused by hardware or network
malfunction and correcting it if possible.


                Tape Access Methods
With tapes, the sequential access method is always
used for storing data, which places the next block
of data after the previous one.


                Disk Access Methods
For disks, indexed access methods are widely used
to keep track of records and files.  The index is a
table of contents for each file or each record
within the file.  The sequential method is also
used when retrieval of individual records is not
required.  The indexed sequential method, or ISAM,
combines both methods by providing an index that is
kept in sequential order.  For fastest retrieval,
the direct access method uses a formula to convert
the record's identifying field, such as account
number, into a physical storage address.


           Communications Access Methods
Communications access methods, such as IBM's TCAM
and VTAM, transfer data between a host computer and
remote terminals.  These routines prepare the data
for transmission by placing the data into frames
with appropriate control codes.  These methods
reference layers 3, 4 and 5 of the OSI model.

   LAN access methods, such as CSMA/CD (Ethernet)
and token passing (Token Ring), transfer data to
and from connected computers on the network.  These
methods reference layers 1 and 2 of the OSI model.



access server
See communications server.



access time
(1) Memory access time is how long it takes for a
character in memory to be transferred to or from
the CPU.  In a personal computer, fast RAM chips
have an access time of 70 nanoseconds or less.

(2) Disk access time is an average of the time it
takes to position the read/write head over the
requested track.  Fast personal computer hard disks
have access times of 18 milliseconds or less.
Mainframe disks can be less than one millisecond.
This is a common speed measurement, but disk
performance is influenced by channel speed
(transfer rate), interleaving and caching.



ACCESS.bus
A serial bus that is expected to become popular in
the 1995 timeframe.  It allows multiple devices to
be daisy chained together using a four-wire cable
and connector similar to a phone jack.  It runs at
125Kbits/sec and is designed to hook up several
slower-speed peripherals such as a mouse, keyboard
and modem.



account number
The number assigned to an employee, customer,
vendor or product for identification.  Although it
may contain only numeric digits, it is often stored
as a character field, so that parts of the account
number can be searched independently.  For example,
the number could contain a territory code, and
records could be selected by state or region.



accounting machine
An early office machine used to compute and prepare
invoices and payroll, etc., using magnetic stripe
ledger cards or punched cards.



accumulator
A hardware register used to hold the results or
partial results of arithmetic and logical
operations.



ACD
(Automatic Call Distribution)  The routing of an
incoming telephone call to the next available
operator.



ACE
(Advanced Computing Environment)  An open standard
based on UNIX and Windows NT introduced in 1991 by
MIPS Computer Systems and others.  Although later
disbanded, it was designed to allow users to
migrate from x86 PCs to MIPS RISC machines.



ACF
(Advanced Communications Function)  An official
product line name for IBM SNA programs, such as
VTAM (ACF/VTAM), NCP (ACF/NCP), etc.



ACK
(ACKnowledgment code)  The communications code sent
from a receiving station to a transmitting station
to indicate that it is ready to accept data.  It is
also used to acknowlege the error-free receipt of
transmitted data.  Contrast with NAK.



acknowledgement code
See ACK.



Acknowledgements
See About this database.



ACM
(Association for Computing Machinery)  A membership
organization founded in 1947 dedicated to advancing
the arts and sciences of information processing.
In addition to awards and publications, ACM also
maintains special interest groups (SIGs) in the
computer field.  Address: 1515 Broadway, New York,
NY 10036, 212/869-7440.



acoustic coupler
A device that connects a terminal or computer to
the handset of a telephone.  It contains a shaped
foam bed that the handset is placed in, and it may
also contain the modem.



Acrobat
Document exchange software from Adobe Systems,
Inc., Mountain View, CA, that converts a DOS,
Windows, UNIX or Macintosh document into a
proprietary file format for viewing on other
machines.  Documents are converted to Acrobat's
Portable Document Format (PDF) format that are
displayed on the target machine with an Acrobat
viewer.  Acrobat Distiller converts PostScript
files into the PDF Format, and Acrobat Exchange
lets users add bookmarks and hypertext links to
their PDF files.



ACS
(Asynchronous Communications Server)  A
communications server that manages a pool of
modems.  It directs outgoing messages to the next
available modem and directs incoming messages to
the appropriate workstation.



active addressing
A technology that improves passive matrix LCD
screens.  Rather than having a transistor attached
to each pixel on the back of the screen, the
transistors are on chips on the motherboard.  The
resulting display looks almost as good as active
matrix without the high cost.  This emerging
technology is expected in 1994.  See LCD.



active hub
The central connecting device in a network that
regenerates signals.  Contrast with passive hub and
intelligent hub.  See hub.



active matrix
An LCD technology used in flat panel computer
displays.  Using a transistor for each pixel, it
produces a high quality display and eliminates the
submarining associated with passive matrix screens.
See LCD.



active star
See active hub.



ACTOR
An object-oriented programming language for PCs
from The Whitewater Group Inc., Evanston, IL.  It
runs under Windows and has a Pascal-like syntax to
ease the transition to object-oriented languages.



actuator
A mechanism that causes a device to be turned on or
off, adjusted or moved.  The component that moves
the head assembly on a disk drive or an arm of a
robot is called an actuator.



AD/Cycle
(Application Development/Cycle)  SAA-compliant
software from IBM that provides a system for
managing systems development.  It provides a
structure for storing information about all phases
of an information system including systems analysis
and design, database design and programming.



ad hoc query
A non-standardized inquiry.  An ad hoc query is
composed to answer a question when the need arises.



Ada
A high-level programming language developed by the
U.S. Department of Defense along with the European
Economic Community and many other organizations.
It was designed for embedded applications and
process control but is also used for logistics
applications.  Ada is a Pascal-based language that
is very comprehensive.

   Ada was named after Augusta Ada Byron (1815-
1852), Countess of Lovelace and daughter of Lord
Byron.  She was a mathematician and colleague of
Charles Babbage, who was developing his Analytical
Engine.  Some of her programming notes for the
machine have survived, giving her the distinction
of being the first documented programmer in the
world.

   The following Ada program converts Fahrenheit to
Celsius:

with Text_IO;
procedure Convert is
 package Int_IO is new Text_IO.Integer_IO(Integer);
 Fahrenheit : Integer;
begin
 Text_IO.Put_Line("Enter Fahrenheit");
 Int_IO.Get(Fahrenheit);
 Text_IO.Put("Celsius is ");
 Int_IO.Put((Fahrenheit-32) * 5 / 9);
 Text_IO.New_Line;
end Convert;





ADABAS
A DBMS from Software AG, Reston, VA, for IBM
mainframes, VAXes, various UNIX platforms and OS/2
PCs.  It is an inverted list DBMS with relational
capabilities.  A 4GL called NATURAL, text
retrieval, GIS processing, SQL and distributed
database functions are also available.  Introduced
in 1969, it was one of the first DBMSs.



ADAPSO
See ITAA.



adapter
A device that allows one system to connect to and
work with another.  Display adapters and network
adapters are really controllers, not adapters.  See
host adapter and expansion bus.



adaptive bridge
A network bridge that remembers destination
addresses in order to route subsequent packets more
quickly.  Most bridges are this type.



adaptive compression
A data compression technique that dynamically
adjusts the algorithm used based on the content of
the data being compressed.



adaptive equalization
A transmission technique that dynamically adjusts
its modulation method based on the quality of the
line.



adaptive routing
The ability to select a new communications path to
get around heavy traffic or a node or circuit
failure.



ADB
(Apple Desktop Bus)  The Macintosh communications
port for keyboards, mice, trackballs, graphics
tablets and other input devices.



ADC
See A/D converter.



ADCCP
(Advanced Data Communications Control Procedure)
An ANSI communications protocol that is similar to
the SDLC and HDLC protocols.



add-in, add-on
Refers to hardware modules, such as printed circuit
boards, that are designed to be plugged into a
socket within the computer.



adder
An elementary electronic circuit that adds the bits
of two numbers together.



address
(1) The number of a particular memory or peripheral
storage location.  Like post office boxes, each
byte of memory and each disk sector has its own
unique address.  Programs are compiled into machine
language, which references actual addresses in the
computer.

(2) As a verb, to manage or work with.  For
example, "the computer can address 2MB of memory."



address bus
An internal channel from the CPU to memory across
which the addresses of data (not the data) are
transmitted.  The number of lines (wires) in the
address bus determines the amount of memory that
can be directly addressed as each line carries one
bit of the address.  For example, the 8088 CPU has
20 address lines and can address 1,048,576 bytes.
The 68020 has 32 address lines and can address four
gigabytes.

   Various swapping and switching techniques can be
added to the hardware that allow a computer to use
more memory than is directly addressable by its
address bus.  See EMS.


     Ŀ           Ŀ
               1Ĵ          
        CPU    2Ĵ   RAM    
               4Ĵ          
               8Ĵ          
               16Ĵ          
               32Ĵ          
               64Ĵ          
               128Ĵ          

                 Address Bus




address mode
The method by which an instruction references
memory.  An indexed address is modified by the
contents of an index register before execution.  An
indirect address points to another address.
Ultimately, in order to do any actual processing,
the instruction must derive real, or absolute
addresses, where the required data is located.



address register
A high-speed circuit that holds the addresses of
data to be processed or of the next instruction to
be executed.



address resolution
Obtaining a physical address that is ultimately
needed to perform an operation.  All instructions
executing at the machine level require a physical
memory, storage or network node address when
referencing the actual hardware.  Machine addresses
are derived using table lookups and/or algorithms.

   In a network, a "where is?" request is broadcast
onto the network, and the logical address (name) is
turned into a physical address (machine number),
either by the recipient node or by a router that
maintains a list of address translations.



address resolution protocol
See ARP.



address space
The total amount of memory that can be used by a
program.  It may also refer to virtual memory,
which includes memory and disk.  For example, the
386 can address 4GB of physical memory and 64TB of
virtual memory.



address translation
Transforming one address into another.  For
example, assemblers and compilers translate
symbolic addresses into machine addresses.  Virtual
memory systems translate a virtual address into a
real address.



addressable cursor
A screen cursor that can be programmed to move to
any row or column on the screen.



ADE
(Application Development Environment)  An IBM
approach for developing applications that will run
in all SAA environments.  The development software
is client/server based, and the main functions
reside in the host.



ADF
(Application Development Facility)  An IBM
programmer-oriented mainframe application generator
that runs under IMS.



ADMD
(ADministrative Management Domain)  A public e-mail
service.  See X.400.



Adobe fonts
See PostScript.



Adobe Illustrator
A full-featured drawing program for Windows and
Macintosh from Adobe Systems, Inc.  It provides
sophisticated tracing and text manipulation
capabilities as well as color separations.
Included is Adobe Type Manager and a selection of
Type 1 fonts.  Illustrator was originally developed
for the Mac and includes more features.  The
Windows versions comes with Adobe Type Align and
Adobe Streamline, for tracing bitmaps.



Adobe Photoshop
A popular image editing program for the Macintosh
and Windows from Adobe Systems.  The original Mac
versions were the first to bring affordable image
editing down to the personal computer level in the
late 1980s.  Photoshop has become a standard in
image editing.



Adobe Type Align
Software from Adobe Systems, Inc., that is used to
align text to different shapes; for example,
wrapping text around a circle or along the borders
of an irregular or multi-sided object.



Adobe Type Manager
A PostScript font utility for the Macintosh and
Windows from Adobe Systems.  It scales Type 1 fonts
into screen fonts and prints them on non-PostScript
dot matrix and HP laser printers.  For printing
fonts, current versions of ATM download font
bitmaps to the printer.  Earlier versions sent a
bitmap of the entire page of text to the printer.

   ATM technology is built into OS/2 and NeXTstep,
and was originally developed to provide WYSIWYG
screen fonts for the Mac.  Since Windows does not
render PostScript fonts on screen, ATM is widely
used to do so.  Both work together.  Under Windows,
ATM scales Type 1 fonts, while Windows 3.1 scales
TrueType fonts.  See PostScript.



ADP
(1) (Automatic Data Processing)  Synonymous with
data processing (DP), electronic data processing
(EDP) and information processing.

(2) (Automatic Data Processing, Inc., Roseland, NJ)
A nationwide computer services organization that
specializes in payroll processing.



ADP system
(Automatic Data Processing system)  Same as
computer system.



ADPCM
(Adaptive Differential PCM)  An advanced PCM
technique that converts speech to 32 or 16
Kbits/sec.  Instead of coding an absolute
measurement at each sample point, it codes the
difference between samples and can dynamically
switch the coding scale to compensate for
variations in amplitude and frequency.



ADRS
(A Departmental Reporting System)  An IBM mainframe
report writer.



ADS
(AutoCAD Development System)  A facility that
allows C routines to be run from within AutoCAD.



ADSL
(Asymmetrical Digital Subscriber Lines)  A
communications technology used to transmit digital
data over telephone wires.  It is expected to
transmit up to six megabits per second and be used
for video-on-demand services to telephone company
customers.



ADT
(Asynchronous Data Transfer)  A transmission
technique used in ISDN PBXs that dynamically
allocates bandwidth.  See also abstract data type.



Advanced Revelation
An application development system for DOS and OS/2
from Revelation Technologies, Inc., Stamford, CT.
It provides strong text handling with the variable-
length structures of its DBMS.  It includes the
R/BASIC programming language and supports SQL, DB2,
Oracle and other databases.  The Windows
counterpart is called OpenInsight and uses the
BASIC+ language.



AdvanceNet
HP's early network strategy that included OSI, SNA
and various networking standards along with its
proprietary networking.  In the mid 1980s, HP moved
from proprietary networking to open standards.



ADW
(Application Development Workbench)  An integrated
CASE-based application development system from
Sterling Software, Atlanta, GA (formerly
KnowledgeWare).  It integrates a variety of PC-
based tools for designing and developing
client/server, AS/400 and IBM mainframe
applications.  In early 1994, KnowledgeWare
reported that it shipped its 100,000 unit of ADW.



AFE
(Apple File Exchange)  A Macintosh utility that
converts data files between Mac and PC formats.  It
also includes a file translator between IBM's DCA
format and MacWrite; however, MacLink Plus
Translators can be used for additional capability.



AFIPS
(American Federation of Information Processing
Societies Inc.)  An organization founded in 1961
dedicated to advancing information processing in
the U.S.  It was the U.S. representative of IFIP
and umbrella for 11 membership societies.
Dissolved in 1990 and superseded by FOCUS.



AFM file
(Adobe Font Metrics file)  A file that contains
font metric information for a Type 1 PostScript
font.  See PFA file, PFB file and PostScript.



AFP
(AppleTalk Filing Protocol)  A client/server
protocol used in AppleTalk communications networks.
In order for non-Apple networks to access data in
an AppleShare server, their protocols must
translate into the AFT language.



AFS
A distributed file system for large, widely-
dispersed UNIX networks from Transarc Corporation,
Pittsburgh, PA.  It is noted for its ease of
administration and expandability and stems from
Carnegie-Mellon's Andrew File System.



After Dark
A popular screen saver program for Macs and PCs
from Berkeley Systems, Inc., that allows the user
to develop custom animations.  After Dark
popularized the "flying toaster" display in 1989.



agent
A software routine that waits in the background and
performs an action when a specified event occurs.
For example, agents could transmit a summary file
on the first day of the month or monitor incoming
data and alert the user when a certain transaction
has arrived.  See workflow automation.



AI
(1) (Artificial Intelligence)
(2) (Application Interface)

(1) (Artificial Intelligence)  Devices and
applications that exhibit human intelligence and
behavior including robots, expert systems, voice
recognition, natural and foreign language
processing.  It also implies the ability to learn
or adapt through experience.

   In the future, everything we now know and think
about a computer will change.  By the turn of the
century, you should be able to converse with the
average computer.  Future systems will ask you what
help you need and automatically call in the
appropriate applications to aid you in solving your
problem.

   In the 1990s, the AI buzzword will be abused to
the hilt as it will refer to any and all
advancements.  However, the acid test of AI was
defined in the 1940s by the English scientist, Alan
Turing, who said, "A machine has artificial
intelligence when there is no discernible
difference between the conversation generated by
the machine and that of an intelligent person."

   Note: The term intelligence refers to processing
capability; therefore, every computer is
intelligent.  But, artificial intelligence implies
human-like intelligence.  An ironic twist in
terminology.

(2) (Application Interface)  The programming
interface for IBM's 8514/A.



AIIM
(Association for Information and Image Management)
A membership organization that promotes and
advances the development of systems that store,
retrieve, integrate and manage images of documents.
Founded in 1943, it provides periodicals, industry
studies, educational programs and expositions.
Address: 1100 Wayne Ave., Suite 1100, Silver
Spring, MD 20910, 301/587-8202.



AIM
(Apple/IBM/Motorola)  The alliance of Apple, IBM
and Motorola, which developed the PowerPC chip,
Taligent, Kaleida, etc.  See Apple.



AIX
(Advanced Interactive eXecutive)  IBM's version of
UNIX, which runs on PCs (386 and up), RS/6000
workstations and 390 mainframes.  It is based on
AT&T's UNIX System V with Berkeley extensions.  A
Workplace-enabled version of AIX is being developed
for the PowerPC and is expected in 1995.



alarm filtering
In network management, the ability to pinpoint the
device that has failed.  If one device in a network
fails, others may fail as a result and cause
alarms.  Without alarm filtering, the management
console reports all deteriorating devices with
equal attention.



ALC
(Assembly Language Coding)  A generic term for IBM
mainframe assembly languages.



Aldus FreeHand
A full-featured drawing program for Windows and
Macintosh from Aldus Corporation, Seattle, WA.  It
combines a wide range of drawing tools with special
effects.  FreeHand was first available on the Mac.
Also included is Adobe Type Manager and a small
selection of Type 1 fonts.



Aldus Persuasion
A desktop presentation program for the Mac from
Aldus Corporation, Seattle, WA.  It is used to
create output for overheads, handouts, speaker
notes and film recorders and provides sophisticated
transition features (fades, gravel, swipes, etc.).



algebraic expression
One or more characters or symbols associated with
algebra; for example, A+B=C or A/B.



ALGOL
(ALGOrithmic Language)  A high-level compiler
language that was developed as an international
language for the expression of algorithms between
people and between people and machines.  ALGOL-60
(1960) was simple and widely used in Europe.
ALGOL-68 (1968) was more complicated and scarcely
used, but was the inspiration for Pascal.

   The following example changes Fahrenheit to
Celsius:

 fahrenheit
 begin
   real fahr;
   print ("Enter Fahrenheit ");
   read (fahr);
   print ("Celsius is ", (fahr-32.0) * 5.0/9.0);
 end
 finish





algorithm
A set of ordered steps for solving a problem, such
as a mathematical formula or the instructions in a
program.  The terms algorithm and logic are
synonymous.  Both refer to a sequence of steps to
solve a problem.  However, an algorithm implies an
expression that solves a complex problem rather
than the overall input-process-output logic of
typical business programs.



alias
(1) An alternate name used for identification, such
as for naming a field or a file.

(2) A phony signal created under certain conditions
when digitizing voice.



aliasing
In computer graphics, the stair-stepped appearance
of diagonal lines.  See anti-aliasing.



ALL-IN-1
Office systems software from Digital for the VAX
series.  It provides a menu to all of Digital's
office systems programs, including word processing,
appointment calendars and e-mail systems.



all points addressable
See APA.



allocate
To reserve a resource such as memory or disk.  See
memory allocation.



ALM
See AppWare.



Alpha
A family of advanced RISC-based, 64-bit CPUs from
Digital.  The first model introduced in early 1992
was the 150MHz 21064-AA, considered equivalent to a
Cray-1 on a single chip.  Alpha AXP computer
systems use the Alpha CPU and run under Windows NT,
OpenVMS and Digital's OSF/1 operating systems.

   The Alpha 21164 CPU, introduced in 1994,
continues to blaze trails for high-speed
microprocessors.  The 21164 has 9.3 million
transistors and executes 1.2 BIPS.  It comes in
266MHz and 300MHz versions.  Digital is expected to
produce the chip with .035 micron technology some
time in 1995 (see micron).



alpha channel
The high-order eight bits in a 32-bit graphics
pixel used as a separate layer to mask an area for
editing or creating special effects (textures,
montages, etc.).



Alpha Four, Five
A database program from Alpha Software Corporation,
Burlington, MA, that is noted for its ease of use.
Alpha programs read and write dBASE files directly.
Alpha Four for DOS provides scripts for customizing
applications.  Alpha Five for Windows includes
Xbasic, a BASIC-like programming language that
incorporates database commands.



alpha test
The first test of newly developed hardware or
software in a laboratory setting.  The next step is
beta testing with actual users.



alphageometric
See alphamosaic.



alphamosaic
A very-low-resolution display technique that uses
elementary graphics characters as part of its
character set.



alphanumeric
The use of alphabetic letters mixed with numbers
and special characters as in name, address, city
and state.  The text you're reading is
alphanumeric.



alt key
A keyboard key that is pressed with a letter or
digit key to command the computer.  For example, in
Windows, holding down the alt key and pressing F
displays the File menu.  Pressing Alt-Tab toggles
between applications.



Altair 8800
A microcomputer kit introduced in 1974 from Micro
Instrumentation and Telemetry Systems.  It sold for
$400 and used an 8080 microprocessor.  In 1975, it
was packaged with Microsoft's MBASIC.  Although
computer kits were advertised earlier by others, an
estimated 10,000 Altairs were sold, making it the
first commercially successful microcomputer.



alternate routing
The ability to use another transmission line if the
regular line is busy.



alternating current
See AC.



AlterNet
See UUNET.



Alto
The personal computer from Xerox that pioneered the
mouse/icon/desktop environment.  Developed at PARC,
it was the progenitor of Xerox's Star and Apple's
Lisa and Mac.  Designed in 1973 with 128K RAM,
608x808 screen, 2.5MB removable hard disk and
built-in Ethernet.  About 1,000 Altos were in use
by 1979.



ALU
(Arithmetic Logic Unit)  The high-speed CPU circuit
that does calculating and comparing.  Numbers are
transferred from memory into the ALU for
calculation, and the results are sent back into
memory.  Alphanumeric data is sent from memory into
the ALU for comparing.  The results are tested by
GOTOs; for example, IF ITEMA EQUALS ITEMB GOTO
UPDATE ROUTINE.



AM
(Amplitude Modulation)  A transmission technique
that blends the data signal into a carrier by
varying (modulating) the amplitude of the carrier.
See modulate.



Am386, Am486
Low-power, 386- and 486-compatible CPU chips from
AMD (Advanced Micro Devices).



ambient
Surrounding.  For example, ambient temperature and
humidity are atmospheric conditions that exist at
the moment.



Ambra
(Ambra Computer Corporation, Raleigh, NC)  A
subsidiary of the IBM PC Company that sold PCs as
"IBM clones" via direct mail under the Ambra name.
Although only a year in business, in the summer of
1994, Ambra was shut down by IBM, claiming it
caused too much confusion in the marketplace.



AmCoEx
See used computers and computer exchange.



AMD
(Advanced Micro Devices, Inc., Sunnyvale, CA)  A
manufacturer of x86-compatible CPUs.  AMD has
become a competitor to Intel and its chips are used
by many PC makers, including Compaq.  Chips with
the Am386 and Am486 logo are made by AMD.



Amdahl
(Amdahl Corporation, Sunnyvale, CA)  A computer
manufacturer founded in 1970 by Gene Amdahl, chief
architect of the IBM System/360.  In 1975, Amdahl
installed its first IBM-compatible mainframe, the
470/V6.  Although not the first to make IBM-
compatible mainframes, it succeeded where others
failed.  Amdahl offers a full range of IBM-
compatible mainframes as well as application
development software and midrange UNIX servers.

   Dr. Amdahl left the company to form Trilogy in
1979 and later Andor Corporation, a manufacturer of
products for large IBM mainframe installations.



America Online
An online information service that provides
conferencing, news, e-mail, education, technical
support forums, more than 70,000 software files and
access to a large variety of databases, including
National Geographic and PC World magazine.
Software for DOS, Windows, Mac and Apple II
provides navigation through the system.  See online
services.



American Bell
An AT&T trade name used after divestiture.  Federal
court order later prohibited its use.



American Computer Exchange
See used computers and computer exchange.



American Federation of Information Processing
See AFIPS.



American National Standards Institute
See ANSI.



American Standard Code for Information Interchange
See ASCII.



AMI BIOS
A popular PC-compatible ROM BIOS from American
Megatrends, Inc., Norcross, GA.



Ami Pro
A windows word processing program from Lotus that
includes desktop publishing features.  It allows
for the creation of presentation-quality charts and
graphs.  Ami was one of the first full-featured
word processors for Windows and was originally
developed by Samna Corporation.



Amiga
A personal computer series from Commodore that runs
under the AmigaDOS operating system.  It uses the
68000 CPU family and features the Workbench
graphical user interface.

   The Amiga 500 is geared for home use and
includes built-in speech synthesis, stereo sound
and color graphics.  The Amiga 2000, designed for
office applications, CAD and desktop publishing,
has optional PC compatibility and NTSC video
processing.  The Amiga 3000 uses the 68030 CPU and
provides enhanced graphics and the Workbench
interface.  The Amiga 4000 improves performance
with the 68040 CPU.



amp
(AMPere)  A unit of electrical current in a
circuit.  Volts measure the force or pressure
behind the current.  Watts are a total measurement
of power derived from multiplying amps times volts.



amplitude
The strength or volume of a signal, usually
measured in decibels.



amplitude modulation
See AM.



analog
A representation of an object that resembles the
original.  Analog devices monitor conditions, such
as movement, temperature and sound, and convert
them into analogous electronic or mechanical
patterns.  For example, an analog watch represents
the planet's rotation with the rotating hands on
the watch face.  Telephones turn voice vibrations
into electrical vibrations of the same shape.
Analog implies continuous operation in contrast
with digital, which is broken up into numbers.


           Advantages and Disadvantages
               Of Analog Techniques
Traditionally, audio and video recording has been
analog.  Sound, which is continuously varying air
vibrations, is converted into analogous electrical
vibrations.  Video cameras scan their viewing area
a line at a time and convert the infinitely varying
intensities of light into analogous electrical
signals.

   The ability to capture the subtle nature of the
real world is the single advantage of analog
techniques.  However, once captured, modern
electronic equipment, no matter how advanced,
cannot copy analog signals perfectly.  Third and
fourth generations of audio and video recordings
show marked deterioration.

   By converting analog signals into digital, the
original audio or video data can be preserved
indefinitely and copied over and over without
deterioration.  Once continuously varying analog
signals are measured and converted into digital
form, they can be stored and transmitted without
loss of integrity due to the accuracy of digital
methods.

   The key to conversion is the amount of digital
data that is created from the analog signal.  The
shorter the time interval between samples and the
more data recorded from that sample, the more the
digital encoding reflects the original signal.



analog channel
In communications, a channel that carries voice or
video in analog form as a varying range of
electrical frequencies.  Contrast with digital
channel.



analog computer
A device that processes infinitely varying signals,
such as voltage or frequencies.  A thermometer is a
simple analog computer.  As the temperature varies,
the mercury moves correspondingly.  Although
special-purpose, complex analog computers are
built, almost all computers are digital.  Digital
methods provide programming flexibility.



analog monitor
A video monitor that accepts analog signals from
the computer (digital to analog conversion is
performed in the display adapter).  It may accept
only a narrow range of display resolutions; for
example, only VGA or VGA and Super VGA, or it may
accept a wide range of signals including TV.  See
multisync monitor and RGB monitor.  Contrast with
digital monitor.



analysis
See systems analysis & design.



analyst
See systems analyst and business analyst.



analytical database engine
Software that provides multiple views into a
database of numerical information.  The data is
maintained in a non-redundant database, and the
views are displayed in a traditional spreadsheet
interface.  See spreadsheet and TM/1.  See also
OLAP database.



Analytical Engine
A programmable calculator designed by British
scientist, Charles Babbage (mid 1830s).  Although
never completed due to lack of funds and constant
redesign, it was a major advance and contained the
principles of the stored program computer.

   Babbage's colleague, Augusta Ada Byron, daughter
of the poet Lord Byron, explained the machine's
concepts to the public.  See Ada.



AND, OR & NOT
The fundamental operations of Boolean logic.  AND
is true if both inputs are true, OR is true if any
input is true, and NOT is an inverter; the output
is always the opposite.  See Boolean search, chip
and gate.

       AND              OR              NOT
  Inputs  Output   Inputs  Output   Input  Output
 Ŀ  Ŀ  Ŀ
  0   0   0     0   0   0      0    1  
  0   1   0     0   1   1      1    0  
  1   0   0     1   0   1    
  1   1   1     1   1   1  
   




ANDF
(Architecture Neutral Distributed Format)  See OSF.



angstrom
A unit of measurement equal to .1 nanometer, which
is approximately 1/250 millionth of an inch.  Ten
angstroms equal one nanometer.  Angstroms are used
to measure the wavelengths of light and the
elements in a chip.



ANI
(Automatic Number Identification)  A telephone
service that provides the telephone number of the
incoming call.  ISDN supports ANI by carrying the
calling telephone number in the D channel.



animated graphics
Moving diagrams or cartoons.  Often found in
computer-based courseware, animated graphics take
up far less disk space than video images.



anisotropic
Refers to properties, such as transmission speed,
that vary depending on the direction of
measurement.  Contrast with isotropic.



anode
In electronics, a positively charged receiver of
electrons that flow from the negatively charged
cathode.



anomaly
Abnormality or deviation.  It is a favorite word
among computer people when complex systems produce
output that is inexplicable.



anonymous FTP
An FTP site on the Internet that contains files
that can be downloaded by anyone.  The anonymous
FTP directory is isolated from the rest of the
system and will generally not accept uploads from
users.



ANSI
(American National Standards Institute)  A
membership organization founded in 1918 that
coordinates the development of U.S. voluntary
national standards in both the private and public
sectors.  It is the U.S. member body to ISO and
IEC.  Information technology standards pertain to
programming languages, EDI, telecommunications and
physical properties of diskettes, cartridges and
magnetic tapes.  Address: 11 West 42 St., New York,
NY 10036, 212/642-4900.



ANSI character set
The ANSI-standard character set that defines 256
characters.  The first 128 are ASCII, and the
second 128 contain math and foreign language
symbols, which are different than those on the PC.
See extended ASCII.



ANSI terminal
A display terminal that follows commands in the
ANSI standard terminal language.  Uses escape
sequences to control the cursor, clear the screen
and set colors, for example.  Communications
programs often support the ANSI terminal.



ANSI.SYS
See DOS ANSI.SYS.



answer only modem
A modem capable of answering a call, but not
initiating one.



anti-aliasing
In computer graphics, a category of techniques that
is used to smooth the jagged appearance of diagonal
lines.  For example, the pixels that surround the
edges of the line are filled in with varying shades
of gray or color in order to blend the sharp edge
into the background.  See dithering.



Antifuse
A PLD technology from Actel Corporation that works
the opposite of typical programmable chip methods.
Instead of creating open circuits (blowing the
fuse), connections are made between elements.



antivirus
A program that detects and removes a virus.



ANVIL
A family of CADD/CAM software packages from
Manufacturing and Consulting Services Inc.,
Scottsdale, AZ.  ANVIL products include 2 1/2-D and
3-D mechanical engineering systems for PCs,
workstations, minis and mainframes.



any key
The message "press any key" means that you must
press a key on the keyboard to continue.  It
doesn't matter which one you press: a letter key,
return key, the space bar, etc.



AOCE
(Apple Open Collaboration Environment)  Extensions
to the Macintosh System 7 operating system from
Apple that provide a technology framework for
sharing services across a multiplatform enterprise.
PowerTalk and PowerShare are the first AOCE
products.



AOL
See America Online.



APA
(All Points Addressable)  Refers to an array
(bitmapped screen, matrix, etc.) in which all bits
or cells can be individually manipulated.



APCUG
(Association of Personal Computer User Groups) A
non-profit organization dedicated to fostering
communication among and between user groups and
between user groups and vendors.  Address: Suite
700, 1730 M St. N.W., Washington, DC 20036.



aperture card
A punched card that holds a frame of microfilm.



API
(Application Program Interface)  A language and
message format used by an application program to
communicate with another program that provides
services for it.  APIs are usually implemented by
writing function calls.  Examples of APIs are the
calls made by an application program to such
programs as an operating system, messaging system
or database management system (DBMS).  See
interface.



APIC
See PIC.



APL
(A Programming Language)  A high-level, interactive
scientific language noted for its brevity and
matrix generation capabilities.  Developed by
Kenneth Iverson in the mid 1960s, it runs on micros
to mainframes and is often used to develop
mathematical models.  It is primarily an
interpreted language, but compilers are available.

   APL uses unique character symbols and requires
special software or ROM chips to enable the
computer to display and print them.  APL is popular
in Europe.



APM
(Advanced Power Management)  An API from Intel and
Microsoft for battery-powered computers that lets
programs communicate power requirements to slow
down and speed up components.



Apollo
(Apollo Systems Div. of HP)  Formerly Apollo
Computer, Inc., this maker of high-performance
workstations became a division of HP in 1989.
Founded in 1980, it pioneered networked
workstations.



app
See application.



app code
(APPlication code)  Instructions in a program that
actually process data.



APPC
(Advanced Program-to-Program Communications)  A
high-level communications protocol from IBM that
allows a program to interact with another program.
It supports client/server and distributed computing
by providing a common programming interface across
all IBM platforms for communications over a variety
of transport protocols.  It provides commands for
managing a session, sending and receiving data and
transaction security and integrity (two-phase
commit).

   APPC software is either part of or optionally
available on all IBM and many non-IBM operating
systems.  Since APPC has only supported SNA,
utilizing SNA's LU 6.2 protocol for session
establishment, APPC and LU 6.2 have been considered
synonymous.  In time, APPC will support other
industry protocols, such as TCP/IP and OSI.

   APPC commands have differed across platforms.
Under SAA, the CPI-C interface defines a standard
set of APPC verbs.



append
To add to the end of an existing structure.



Apple
(Apple Computer, Inc., Cupertino, CA)  A
manufacturer of personal computers and the
industry's most fabled story.  Founded in a garage
by Steve Wozniak and Steve Jobs and guided by Mike
Markkula, Apple blazed the trails for the personal
computer industry.  Today, Apple makes more
personal computers than any other single company.

   Apple was formed on April Fool's Day in 1976.
After introducing the Apple I at the Palo Alto
Homebrew Computer Club, 10 retail stores were
selling them by the end of the year.

   In 1977, it introduced the Apple II, a fully-
assembled computer with 4K RAM for $1,298.  Its
open architecture encouraged third-party vendors to
build plug-in hardware enhancements.  This, plus
sound and color graphics, caused Apple IIs to
become the most widely used computer in the home
and classroom.  They were also used in business
primarily for the innovative VisiCalc software that
was launched on it.

   In 1983, Apple introduced the Lisa, the
forerunner of the Macintosh.  Lisa was aimed at the
corporate market, but was soon dropped in favor of
the Mac.  As a graphics-based machine, the Mac was
successful as a low-cost desktop publishing system.
Although praised for its ease of use, its slow
speed, small screen and closed architecture didn't
excite corporate buyers.

   Since the advent of the Mac II in 1987, that has
changed.  Macs offer large screens, open
architecture and color.  Numerous entry-level and
high-speed models have been added and widely
accepted.

   In 1991, Apple surprised the industry by
announcing an alliance with IBM to integrate Macs
into IBM enterprise networks and to develop new
hardware and software together.  For details, see
Apple-IBM alliance.

   The first product of this alliance was the
PowerMac, introduced by Apple in 1994.  The
PowerMac is the next generation of Macintoshes,
which uses the PowerPC chip and runs traditional
Mac applications as well as DOS and Windows
applications.  All Mac applications will eventually
be ported to the native PowerPC architecture.  The
PowerMacs offer a high-speed computing environment
for the 1990s.



Apple Desktop Bus
See ADB.



Apple File Exchange
See AFE.



Apple-IBM alliance
In 1991, Apple and IBM agreed to do the following:

(1) To better integrate Macs into IBM enterprise
networks.

(2) To develop the PowerPC, a single-chip version
of IBM's RS/6000 architecture, with IBM and
Motorola.

(3) To develop PowerOpen, an industry standard
operating system that runs AIX and Mac
applications on the PowerPC.

(4) To form Taligent, Inc., to develop and license
an object-oriented operating system for the
PowerPC, Motorola 68xxx and Intel x86 families with
compatibility with AIX, OS/2 and System 7.

(5) To form Kaleida Labs, Inc. to develop and
license multimedia software, tools and scripting
languages for a diverse variety of computers and
consumer electronic gear.


                    The Results
(1) More integration of Apple products into IBM
shops has taken place.  IBM routers now have the
option of running Apple's communications protocols
to connect to Apple networks.  IBM and Apple co-
designed a new Token Ring network adapter for the
Macintosh that makes it more compatible with IBM's
LAN technology.

(2) As of late 1994, over a million PowerPC chips
have been shipped in PowerMacs and certain models
of IBM's RS/6000 workstations.  The PowerPC appears
to be a formidable contender in the computer world,
causing Intel to speed up design and production of
its next-generation chips.

(3) PowerOpen is no longer an operating system, but
a specification for compliance for a UNIX-based
operating system on the PowerPC.  This is expected
to bring about shrink-wrapped UNIX software for the
PowerPC (see PowerOpen).

(4) Hewlett-Packard became part of the Apple-IBM
ownership of Taligent in 1994, and Taligent's
operating system is expected in 1996.  In the
meantime, it will deliver application frameworks
and development tools for AIX, OS/2, HP-UX and the
PowerMac (see Taligent).

(5) Kaleida is expected to introduce its ScriptX
multimedia technology in 1995.





Apple II
The personal computer family from Apple that
pioneered the microcomputer revolution and has been
widely used in schools and home.  It uses the 8-bit
6502 microprocessor running at 1MHz, an 8-bit bus
and runs under Apple's DOS or ProDOS operating
system.  AppleSoft BASIC is built into ROM and
always available.

   With a Z80 microprocessor board plugged in,
Apple IIs can run CP/M programs, such as dBASE II.

   As of the end of 1992, the Apple IIe and a IIe
card for the Mac LC are the only Apple II models
still in the product line.


APPLE II AND II+
Introduced in 1977, the Apple II came with 4K RAM
and hooked up to a TV and cassette tape recorder.
A floppy disk was available in 1978.  In 1979, an
enhanced II+ came with 48K of RAM.  Screen
resolution is 280x192x6.


APPLE IIe AND IIc
In 1983, the "e"nhanced Apple IIe was introduced
with four cursor keys (not two) and 128K of RAM.
In 1984, the IIc portable was launched with a sleek
design, but limited expandability.


APPLE IIGS
Introduced in 1986 and discontinued in 1992, the
IIGS is faster and adds enhanced graphics and sound
(GS).  It runs standard Apple II software, but
requires GS software to use its enhancements.
Specs: 2.8MHz 16-bit 65C816 CPU, 320x200x256
screen, 15 sounds, AppleTalk.


APPLE III
Yes, there was an Apple III, introduced in 1980 and
intended for business users.  It was not 100%
compatible with the II and never caught on.



Apple key
The original name of the Command key.



Apple menu
The menu at the top left side of a Macintosh screen
that is always available to provide access to desk
accessories.



AppleScript
A comprehensive command language used for
automating tasks that is part of the System 7
operating system from Apple, starting with System 7
Pro.  AppleScript provides a command line interface
to the Macintosh similar to the way DOS commands
are used in a PC.



AppleShare
Software from Apple that turns a Macintosh into a
file server.  It works in conjunction with the Mac
operating system and can coexist with other
Macintosh applications in a non-dedicated mode.



AppleShare PC
Software for PCs from Apple that allows a PC to
connect to an AppleTalk network.  It requires a
LocalTalk PC Card from Apple for ISA PCs, or a
LocalTalk Card from DayStar Communications for
Micro Channel PCs.



AppleSoft BASIC
Apple's version of BASIC that comes with Apple II
models.  It is installed in firmware and is always
available.



applet
A small application, such as a utility program or a
limited-function spreadsheet or word processor.



AppleTalk
Apple's local area network architecture introduced
in 1985.  It supports Apple's proprietary LocalTalk
access method as well as Ethernet and Token Ring.
The AppleTalk network manager and the LocalTalk
access method are built into all Macintoshes and
LaserWriters.

   With other products from Apple and third
parties, AppleTalk can run in PCs, VAXs and UNIX
workstations.  Since AppleTalk is patterned after
the OSI model, it is a routable protocol that
contains a network layer (OSI layer 3).



AppleTalk Filing Protocol
See AFP.



AppleWorks
An integrated software package for Apple IIs from
Claris Corporation.  Introduced in 1983 by Apple,
it combines word processing, file management,
spreadsheet, business graphics and communications.



application
(1) A specific use of the computer, such as for
payroll, inventory and billing.  For a list of
major application software categories, see
application software.

(2) Same as application program and software
package.



application binary interface
See ABI.



application developer
An individual that develops a business application
and usually performs the duties of a systems
analyst and application programmer.



application development environment
The combination of hardware and software used to
develop an application.  See application
development system and ADE.



application development language
Same as programming language.



application development system
A programming language and associated utility
programs that allow for the creation, development
and running of application programs.  Many database
management systems (DBMSs) include a complete
application development system along with a query
language, report writer and the capability to
interactively create and manage database files.

   An application development system may also
provide a full-scale application generator or
various degrees of automatic application
generation.  An application development system that
does not include its own database provides links to
other databases via SQL, ODBC and other interfaces.

   A client/server application development system
is one in which the end product runs on a local
area network.  A two-tiered system splits the
software between client and server.  A three-tiered
system splits the software between client,
application server and database server.  The
application server provides the business logic in
this case.  See client/server development system
and application generator.



Application Development Workbench
See ADW.



application framework
(1) The building blocks of an application.

(2) A class library that provides the foundation
for programming an object-oriented application.



application generator
Software that generates application programs from
descriptions of the problem rather than by
traditional programming.  It is at a higher level
and easier to use than a high-level programming
language.  One statement or descriptive line may
generate a huge routine or an entire program.
However, application generators always have limits
as to what they can be used for.  Generators used
for complex program development allow if-then-else
programming to be expressed along with the simpler
descriptive entries.

   The goal with application generators and
computer-aided software engineering (CASE) has
always been to create a program by describing it,
not programming it.  The problem with such high-
level systems is that either the resulting code is
too slow or certain functions simply cannot be
performed at all.  As a result, commercial programs
are rarely written in these languages; they are
used for business information systems and often
only for creating prototypes that are later
reprogrammed in COBOL or C.

   As computers run faster, they are capable of
absorbing the excess code generated by higher-level
products.  In time, it is expected that the machine
efficiency demanded of today's hardware may not be
as critical and higher-level development tools may
become the norm, relegating lower-level languages
to a handful of highly-skilled and very highly-paid
individuals.  See application development system.



application layer
In communications, the interaction at the user or
application program level.  It is the highest layer
within the protocol hierarchy.  See OSI model.



application notes
Instructions and recommendations from the vendor
provided in addition to the normal reference
manuals.



application package
A software package that is created for a specific
purpose or industry.



application partitioning
Separating an application into components that run
on clients and multiple servers in a client/server
environment.  Programming languages and development
systems that support this architecture, known as
three-tier client/server, may allow the program to
be developed as a whole and then separated into
pieces later.  Development systems are
differentiated by their ability to perform
partitioning as a mainstream function in a high-
level language or with visual programming (drag &
drop) versus having to write chunks of code in C.

   Application partitioning is an important
capability for migrating legacy systems onto
client/server environments.  In many business
applications, there is a lot of processing that
should be done centrally in a server and not in
each client machine.  Such programs are either too
demanding and process intensive for the client or
they represent proprietary business logic that
should not be replicated all over the enterprise.
The centralized mainframe has always made a lot of
sense for many applications.  Partitioning the
logic onto multiple servers emulates this approach
in a client/server environment.


                  Who's Doing It?
Application partitioning can always be accomplished
by writing 3GL code.  However, with today's push
for rapid application development (RAD), writing in
a traditional programming language takes time.
Newer client/server development systems such as
Forte and DYNASTY provide application partitioning
at the 4GL level, and it is being included in
upgrades to existing development systems.

   The OSF's Distributed Computing Environment
(DCE) standard is expected to become popular for
three-tier client/server, because it provides a
standard for accessing programs and databases no
matter where they are located.



application processor
A computer that processes data in contrast with one
that performs control functions, such as a front
end processor or database machine.



application program
Any data entry, update, query or report program
that processes data for the user.  It includes the
generic productivity software (spreadsheets, word
processors, database programs, etc.) as well as
custom and packaged programs for payroll, billing,
inventory and other accounting purposes.  For a
list of major application software categories, see
application software.  Also see program.  Contrast
with system program.



application program interface
See API.



application program library
Application programs used by an organization.



application programmer
An individual who writes application programs in a
user organization.  Most programmers are
application programmers.  Contrast with systems
programmer.



application server
(1) A server in a LAN that contains applications
shared by network clients.  It functions as a
remote disk drive for storing applications.

(2) A server in a LAN that contains the business
processing in a client/server environment.  In this
case, the client provides the user interface, and a
third machine may be used to store the data.  See
three-tiered client/server.



application software
Following are the major categories of application
software (software packages).  See system software
for a list of system software categories.

   Integrated software packages
   and application suites
   usually contain the following
   five applications:
  
  
     Database Programs (Data Management)
     Create and edit master and transaction
     records.  Interactive editing of data.  Ask
     questions, summarize, sort, print reports.
  
     Word Processing
     Create and edit text files.  Replaces all
     typewriter functions.  Some programs provide
     rudimentary desktop publishing.
  
     Spreadsheet
     Create and edit rows and columns of numbers
     for budgets and financial reports.  What if
     analysis?  Multidimensional spreadsheets
     provide different slices, or views, of data
     quickly.  Advanced financial planning systems
     provide goal seeking as well as statistical
     calculations.
  
     Presentation Graphics
     Create slide shows, do freehand drawing and
     turn numbers into 2-D and 3-D business
     graphics.
  
     Communications and Electronic Mail
     Send and receive data and mail via modem or
     over the network.
  
  
     Integrated package or suite
  


      Desktop Publishing
      Merge text and graphics and provide complete
      control over page layout for printing.  More
      precision than word processing programs.
      Disk output is accepted directly by many
      printers.

      PIM
      (Personal Information Manager)  Organize
      random information for fast retrieval.
      Includes such features as a telephone list
      with automatic dialing, calendar, scheduler
      and tickler.

      Project Management
      Keep track of a project and determine the
      impact of changes.  The "critical path" is
      computed, which monitors all tasks that will
      slow down the entire project if delayed.

      CAD (vector graphics)
      Create drawings for illustration and
      industrial design.

      Imaging (raster graphics)
      Scan documents and paint pictures into
      TV-like images.

      Diagramming Program
      Create drawings of interconnected symbols,
      such as network diagrams and organization
      charts.  When symbols are moved, the lines
      stay connected.

      Contact Manager
      Keep track of prospects, names, addresses,
      appointments.  Similar to a PIM, but
      specialized for sales activities.

      Infoware
      Online dictionaries, books and other
      references with hypertext links.  Your
      reading infoware right now.

      Mathematical
      Create, run and print complex mathematical
      equations.

      Scientific
      Analyze real-world events by simulating them
      mathematically.  Supercomputers are widely
      used for this.

      Vertical Markets
      Data entry, query, update and report programs
      custom tailored for an industry such as
      banking and insurance.  Either off-the-shelf
      or custom programmed, vertical market
      software is the most specialized type of
      information system available.

      Multimedia: Games & education
      Multimedia adds graphics, sound and video for
      interactive games, encyclopedias and other
      references and educational courseware of all
      kinds.


  See system software for a list of system software
categories.



application suite
A set of applications designed to work together.
In the Windows environment, the application suite
is the successor to the integrated package, except
that the individual applications are stand alone
and can be purchased separately.  Although Windows
provides integration features such as cut and paste
and compound document creation, the suites provide
additional tools to move data from one application
more easily into another.   In addition, common
functions such as spell checking can be installed
once and shared among all programs.



applications programmer
See application programmer.



APPN
(Advanced Peer-to-Peer Networking)  Extensions to
IBM's SNA communications that provide necessary
enhancements for routing data in a mainframe/LAN
environment.  It includes improved administration,
intermediate node routing and dynamic network
services.  APPN makes use of LU 6.2 protocols and
is implemented in an SNA Node Type 2.1.



Approach
A relational database from Lotus that is also part
of Lotus' SmartSuite set.  It provides the ability
to graphically create Windows applications using
industry standard database formats, such as dBASE
and Paradox.  It includes macros and the ability to
attach programming statements to data, providing a
way to automate many kinds of applications.



AppWare
A client/server development system from Novell that
supports Windows and Mac clients.  It includes
Novell's Visual AppBuilder visual programming tool,
which is used to create applications by linking
pre-built Application Loadable Modules (ALMs)
together.  Visual AppBuilder is expected to ship
with more than 70 ALMs.  ALMs communicate with each
other over a "software bus" known as the AppWare
Bus.

   Foundation libraries for Windows, Mac, OS/2, NT,
Solaris, HP and UnixWare were originally created to
provide cross-platform portabilty.  However, in
late 1994, Novell dropped the libraries, while
continuing with Visual AppBuilder for Windows and
Macintosh.



APT
(Automatic Programmed Tools)  A high-level
programming language used to generate instructions
for numerical control machines.



Arago
A dBASE IV-compatible DBMS and compiler (Arago
Quicksilver) originally developed by WordTech
Systems.  In 1992, the technology was acquired by
Borland.



arbitration
A set of rules for allocating machine resources,
such as memory or peripheral devices, to more than
one user or program.



ARC, ARC+Plus
(1) PC compression programs from System Enhancement
Associates, Inc., Clifton, NJ.  ARC was one of the
first compression utilities to become popular in
the early 1980s.  ARC+Plus provides enhanced
features and speed.

(2) The ARC extension was previously used by PKWARE
Inc. in its PKARC program.

(3) (Advanced RISC Computing)  An open system
specification based on the MIPS R3000 and R4000
CPUs.  It includes EISA and TURBOchannel buses.



Archie
(ARCHIvE)  An Internet utility used to search for
file names.  There are some 30 odd computer systems
throughout the Internet, called "Archie servers,"
that maintain catalogs of files available for
downloading from various FTP sites.  If you don't
have Archie, some Internet hosts let you log on via
Telnet as user "archie."  See Lessons Internet and
FTP.



architecture
See computer architecture, network architecture and
software architecture.



archive
(1) To copy data onto a different disk or tape for
backup.  Archived files are often compressed to
maximize storage media.

(2) To save data onto the disk.



archive attribute
A file classification that indicates whether the
file has been updated since the last backup.



ARCNET
(Attached Resource Computer NETwork)  The first
local area network (LAN) introduced in 1968 by
Datapoint Corporation.  It connects up to 255 nodes
in a star topology at 2.5 Mbits/sec over twisted
pair or coax.  A 20 Mbits/sec version was
introduced in 1989.  Although not as popular as
Ethernet and Token Ring, a lot of ARCNET networks
were sold due to their lower-cost adapters.
Gateways can connect ARCNET to mini and mainframe
networks.

   ARCNET is a data link protocol and functions at
the data link and physical levels of the OSI model
(1 and 2).  It uses the token passing access
method.  See data link protocol and OSI model.



Ardis
(Advanced National Radio Data Service)  A joint
venture of IBM and Motorola that provides wireless
data transmission in the 800MHz FM band.  It covers
most U.S. metropolitan areas with over 1,000 base
stations.



areal density
The bits per square inch of disk surface (BPI x
TPI).



arg
See argument.



argument
In programming, a value that is passed between
programs, subroutines or functions.  Arguments are
independent items, or variables, that contain data
or codes.  When an argument is used to customize a
program for a user, it is typically called a
parameter.



arithmetic coding
A statistical data compression method that converts
strings of data into single floating point numbers
between 0 and 1.



arithmetic expression
(1) In mathematics, one or more characters or
symbols associated with arithmetic, such as 1+2=3
or 86.

(2) In programming, a non-text expression.



arithmetic logic unit
See ALU.



arithmetic operators
Symbols for arithmetic functions: + add, -
subtract, * multiply, / divide.  See precedence.



arithmetic overflow
The result from an arithmetic calculation that
exceeds the space designated to hold it.



arithmetic underflow
The result from an arithmetic calculation that is
too small to be expressed properly.  For example,
in floating point, a negative exponent can be
generated that is too large (too small a number) to
be stored in its allotted space.



ARP
(Address Resolution Protocol)  A low-level TCP/IP
protocol used to obtain a node's physical address
when only its logical IP address is known.  An ARP
request with the IP address is broadcast onto the
network.  The node with that IP address sends back
its hardware address so that packets can be
transmitted.

   Reverse ARP, or RARP, is used by a diskless
workstation to obtain its logical IP address.
Responding to a RARP broadcast from the
workstation, a RARP server sends back the IP
address.



ARPANET
(Advanced Research Projects Agency NETwork)  The
research network funded by DARPA (originally ARPA)
and built by BBN, Inc., in 1969.  It pioneered
packet switching technology and was the original
backbone and testbed for the now-gigantic Internet.
In 1983, the military communications part of it was
split off into MILNET.



ARQ
(Automatic Repeat reQuest)  A method of handling
communications errors in which the receiving
station requests retransmission if an error occurs.



array
An ordered arrangement of data elements.  A vector
is a one dimensional array, a matrix is a two-
dimensional array.  Most programming languages have
the ability to store and manipulate arrays in one
or more dimensions.  Multi-dimensional arrays are
used extensively in scientific simulation and
mathematical processing; however, an array can be
as simple as a pricing table held in memory for
instant access by an order entry program.  See
subscript.



array element
One item in an array.



array processor
A computer, or extension to its arithmetic unit,
that is capable of performing simultaneous
computations on elements of an array of data in
some number of dimensions.  Common uses include
analysis of fluid dynamics and rotation of 3-D
objects, as well as data retrieval, in which
elements in a database are scanned simultaneously.
See vector processor and math coprocessor.



ART
(Automated Reasoning Tool)  A general expert system
written in LISP that is used with various AI
techniques for different applications.



ART-IM
An expert system from Inference Corporation, El
Segundo, CA.  Inference's CBR Express reasoning
shell sits on top of ART-IM.



artifact
Some distortion of an image or sound caused by a
limitation or malfunction in the graphics hardware
or software.



artificial intelligence
See AI.



artificial language
A language that has been predefined before it is
ever used.  Contrast with natural language.



AS
(Application System)  An IBM mainframe 4GL that
runs under MVS.  It was originally designed for
non-computer people and includes commands for
planning, budgeting and graphics.  However, a
programmer can also produce complex applications.
It also provides computer conferencing.



AS/400
(Application System/400)  An IBM minicomputer
series introduced in 1988 that runs under the
OS/400 operating system.  It is IBM's midrange
series of computer systems used primarily for
business applications, most of which are written in
RPG III.

   The AS/400 was designed to supersede the
System/36 and System/38, IBM's prior midrange
computers.  The AS/400 is an enhanced version of
the System/38, which includes an integrated
relational database management system.  Since
System/38 programs can be run without change in the
AS/400, System/38s were readily exchanged for
AS/400s.  However, in order to run System/36
applications, the programs have to be recompiled.
As a result, many System/36s still exist as of late
1994.

   In 1994, IBM introduced the AS/400 Advanced
System/36, a PowerPC-based version of the AS/400
that natively runs the System/36 SSP operating
system and its applications.  Future AS/400s are
expected to run both SSP and OS/400.

   The AS/400 serves in a variety of networking
configurations: as a host or intermediate node to
other AS/400s and System/3x machines, as a remote
system to mainframe-controlled networks and as a
network server to PCs.



ascender
The part of lowercase b, d, f, h, k, l, and t, that
extends above the body of the letters.



ASCII
(American Standard Code for Information
Interchange)  Pronounced "ask-ee."  A binary code
for text as well as communications and printer
control.  It is used for most communications and is
in the built-in character code in most
minicomputers and all personal computers.

   ASCII is a 7-bit code providing 128 character
combinations, the first 32 of which are control
characters.  Since the common storage unit is an 8-
bit byte (256 combinations) and ASCII uses only 7
bits, the extra bit is used differently depending
on the computer.

   For example, the PC uses the additional values
for foreign language and graphics symbols (see
ASCII chart below).  In the Macintosh, the
additional values can be user-defined.  In the Mac
version of this database, the PC symbols are
designed into the font used for the definitions.
See ASCII chart and hex chart.



ASCII chart

ͻ
         Standard ASCII         Extended ASCII  
  The first 32 characters are      (IBM PC)     
        control codes.                          
                                                
 0 Null             33 ! 81 Q128 174 220 ܺ
 1 Start of heading 34 " 82 R129 175 221 ݺ
 2 Start of text    35 # 83 S130 176 222 ޺
 3 End of text      36 $ 84 T131 177 223 ߺ
 4 End of transmit  37 % 85 U132 178 224 
 5 Enquiry          38 & 86 V133 179 225 
 6 Acknowledge      39 ' 87 W134 180 226 
 7 Audible bell     40 ( 88 X135 181 227 
 8 Backspace        41 ) 89 Y136 182 228 
 9 Horizontal tab   42 * 90 Z137 183 229 
10 Line feed        43 + 91 [138 184 230 
11 Vertical tab     44 , 92 \139 185 231 
12 Form feed        45 - 93 ]140 186 232 
13 Carriage return  46 . 94 ^141 187 233 
14 Shift out        47 / 95 _142 188 234 
15 Shift in         48 0 96 `143 189 235 
16 Data link escape 49 1 97 a144 190 236 
17 Device control 1 50 2 98 b145 191 237 
18 Device control 2 51 3 99 c146 192 238 
19 Device control 3 52 4100 d147 193 239 
20 Device control 4 53 5101 e148 194 ³240 
21 Neg. acknowledge 54 6102 f149 195 ó241 
22 Synchronous idle 55 7103 g150 196 ĳ242 
23 End trans. block 56 8104 h151 197 ų243 
24 Cancel           57 9105 i152 198 Ƴ244 
25 End of medium    58 :106 j153 199 ǳ245 
26 Substitution     59 ;107 k154 200 ȳ246 
27 Escape           60 <108 l155 201 ɳ247 
28 File separator   61 =109 m156 202 ʳ248 
29 Group separator  62 >110 n157 203 ˳249 
30 Record separator 63 ?111 o158 204 ̳250 
31 Unit separator   64 @112 p159 205 ͳ251 
32 Blank space      65 A113 q160 206 γ252 
                    66 B114 r161 207 ϳ253 
                    67 C115 s162 208 г254 
                    68 D116 t163 209 ѳ255  
                    69 E117 u164 210 ҳ     
                    70 F118 v165 211 ӳ     
                    71 G119 w166 212 Գ     
                    72 H120 x167 213 ճ     
                    73 I121 y168 214 ֳ     
                    74 J122 z169 215 ׳     
                    75 K123 {170 216 س     
                    76 L124 |171 217 ٳ     
                    77 M125 }172 218 ڳ     
                    78 N126 ~173 219 ۳     
                    79 O127                
                    80 P                    
ͼ




ASCII file
A file that contains data made up of ASCII
characters.  It is essentially raw text just like
the words you're reading now.  Each byte in the
file contains one character that conforms to the
standard ASCII code.  Program source code, DOS
batch files, macros and scripts are written as
straight text and stored as ASCII files.

   ASCII text files become a common denominator
between applications that do not import each
other's formats.  If both applications can import
and export ASCII files, you can transfer your files
between them.

   All text editors (Notepad, DOS Editor, Brief,
etc.) and a few word processors, such as XyWrite,
create ASCII files.  Every other application
generates its own format for storing data.  It may
use ASCII text for names and addresses, but it
contains proprietary codes that conflict with ASCII
control codes.

   For example, if you display a non-ASCII file in
an ASCII editor, you get garble on screen.
Sometimes it beeps or the characters seem to fly by
very fast.  It's because the ASCII editor is
picking up proprietary codes that are
coincidentally the same as ASCII returns, line
feeds and bells (see ASCII chart).

  ASCII file, ASCII text file, text file and TXT
file are synonymous.  Contrast with graphics file
and binary file.



ASCII protocol
The simplest communications protocol for text.  It
transmits only ASCII characters and uses ASCII
control codes.  It implies little or no error
checking.



ASCII sort
The sequential order of ASCII data.  In ASCII code,
lower case characters follow upper case.  True
ASCII order would put the words DATA, data and
SYSTEM into the following sequence:

           DATA   SYSTEM   data





Ashton-Tate
A software company founded in 1980 by Hal Lashlee
and George Tate to market dBASE II, which was
created by Wayne Ratliff (see dBASE).  The company
developed and acquired other products, including
Framework, MultiMate and dBASE Mac.  Borland
acquired Ashton-Tate in 1991 and dispensed with all
products except dBASE.



ASIC
(Application Specific Integrated Circuit)  A custom
chip designed for a specific application.  It is
designed by integrating standard cells from a
library.  ASIC design is faster than designing a
chip from scratch, and design changes can be made
more easily.



askSam
A text management system for PCs from askSam
Systems, Perry FL.  It holds unstructured text as
well as standard data fields.  The product is noted
for its flexible text retrieval and hypertext
capabilities.



ASM
(1) (Association for Systems Management)
An international membership organization founded in
1947 with over 10,000 administrative executives and
specialists in information systems.  It sponsors
conferences in all phases of administrative systems
and management and serves business, education,
government and the military.  Address: 24587 Bagley
Rd., Cleveland, OH 44138, 216/243-6900.

(2) File extension for assembly language source
programs.



ASMP
(ASymmetric MultiProcessing)  A multiprocessing
design in which each CPU is assigned a particular
program or part of a program that it executes for
the duration of the session.  Contrast with SMP, in
which all the CPUs function as a single resource
pool and take on whatever tasks need to processed
next.  See MPP.



ASN.1
(Abstract Syntax Notation.1)  The rules for
defining data structures transmitted over an OSI
network.



ASP
(Association of Shareware Professionals)  A trade
organization for shareware founded in 1987.  Author
members submit products to ASP, which are approved,
virus checked and distributed monthly via CD to
member vendors and BBSs.  CDs are periodically made
available to the public.  Address: 545 Grover Road,
Muskegon, MI 49422, 616/788-5131.



aspect ratio
The ratio of width to height of an object.



ASPI
(Advanced SCSI Programming Interface)  An interface
from Adaptec, Inc., Milpitas, CA, that provides a
common language between drivers and SCSI host
adapters.  See CAM and CorelSCSI.



assembler
Software that translates assembly language into
machine language.  Contrast with compiler, which is
used to translate a high-level language, such as
COBOL or C, into assembly language first and then
into machine language.



assembly language
A programming language that is one step away from
machine language.  Each assembly language statement
is translated into one machine instruction by the
assembler.  Programmers must be well versed in the
computer's architecture, and, undocumented assembly
language programs are difficult to maintain.  It is
hardware dependent; there is a different assembly
language for each CPU series.

   In the past, control programs (operating
systems, database managers, etc.) were written in
assembly language to maximize the machine's
performance.  Today, C is often used instead.  Like
assembly language, C can manipulate the bits at the
machine level, but it is also portable to different
computer platforms.  There are C compilers for most
computers.

   Although often used synonomously, assembly
language and machine language are not the same.
Assembly language is turned into machine language.
For example, the assembly instruction  COMPARE A,B
is translated into COMPARE contents of memory bytes
2340-2350 with 4567-4577 (where A and B happen to
be located).  The physical binary format of the
machine instruction is specific to the computer
it's running in.

   Assembly languages are quite different between
computers as is evident in the example below, which
takes 16 lines of code for the mini and 82 lines
for the micro.  The example changes Fahrenheit to
Celsius.


             HP 3000

  begin
  intrinsic  read,print,binary,ascii;
  array buffer(0:17);
  array string(0:3);
  byte array b'string(*) = string;
  integer ftemp, ctemp, len;
    move buffer:= "Enter Fahrenheit ";
    print (buffer,-30,%320);
    len:=read (string,-4);
    ftemp:= binary(b'string,len);
    ctemp:= (ftemp-32) * 5 / 9;
    len:= ascii(ctemp,1-,b'string);
    move buffer:= "Celsius is ";
    move buffer(14) := string, (-len);
    print (buffer,-32,%0);
  end



          PC (Intel x86)

  cseg    segment para public 'CODE'
          assume  cs:cseg,ds:cseg
  start:
          jmp     start1
  msgstr  db      'Enter Fahrenheit '
  crlf    db      13,10,'$'
  nine    db      9
  five    db      5
  outstr  db      'Centrigrade is $'
  start1: push    ds
          push    cs
          pop     ds
          mov     dx,offset cseg:msgstr
          mov     ah,9
          int     21h
  sloop:
  cent:   call    getnumb
          test    ax,ax
          je      exit
          push    ax
          mov     dx,offset cseg:outstr
          mov     ah,9
          int     21h
          pop     ax
          sub     ax,32
          jns     c1
          push    ax
          mov     dl,'-'
          mov     ah,6
          int     21h
          pop     ax
          neg     ax
  cl:     mul     five
          div     nine
          call    putval
          mov     dx,offset cseg:crlf
          mov     ah,9
          int     21h
          jmp     sloop
  exit:   pop     ds
          mov     ah,4ch
          int     21h
  getnumb:
          xor     bx,bx
  llp:    mov     dl,0ffh
          mov     ah,1
          int     21h
          cmp     al,0dh
          je      llr
          sub     al,'0'
          jb      llr
          cmp     al,'9'
          ja      llr
          xor     ah,ah
          shl     bx,1
          add     ax,bx
          shl     bx,1
          shl     bx,1
          add     bx,ax
          jmp     llp
  llr:    mov     dx,offset cseg:crlf
          mov     ah,9
          int     21h
          mov     ax,bx
          ret
  putval: xor     bx,bx
          push    bx
          mov     bx,10
  llg:    xor     dx,dx
          div     bx
          add     dx,'0'
          push    dx
          test    ax,ax
          jne     llg
  bloop:  pop     dx
          test    dx,dx
          je      endx
          mov     ah,6
          int     21h
          jmp     bloop
  endx:   ret
  cseg    ends
          end     start





assignment statement
In programming, a compiler directive that places a
value into a variable.  For example, COUNTER = 0
creates a variable named counter and fills it with
zeros.  The VARIABLE NAME = VALUE syntax is common
among programming languages.



Association for Computing Machinery
See ACM.



Association for Systems Management
See ASM.



Association of Shareware Professionals
See ASP.



associative storage
Storage that is accessed by comparing the content
of the data stored in it rather than by addressing
predetermined locations.



ASSP
(Application Specific Standard Part)  An ASIC chip
originally designed for one customer and then
released to the general public.



AST
(AST Research, Inc., Irvine, CA)  A PC manufacturer
founded in 1980 by Albert Wong, Safi Quershey and
Tom Yuen (A, S and T).  It offers a complete line
of PCs and sells through its dealer channel.  AST
was initially known for its line of add-in memory
boards for the PC, including the Rampage and SixPak
Plus boards.  Since then, it has become a major PC
player with revenues of nearly one and a half
billion in 1993.  In 1993, AST acquired Tandy
Corporation's PC manufacturing facilities.



asymmetric modem
A full-duplex modem that transmits data in one
direction at one speed and simultaneously in the
other direction at another speed.  For example,
data flows at high-speed in one direction while
acknowledgement is returned at low speed in the
other.  Contrast with ping pong.



asymmetric multiprocessing
See ASMP.



asymmetric system
(1) A system in which major components or
properties are different.

(2) In video compression, a system that requires
more equipment to compress the data than to
decompress it.



asynchronous
(1) Unsynchronized events, for example, the time
interval between event A and B is not the same as B
and C.

(2) Able to initiate a transmission at either end.

(3) In SNA, refers to independent events rather
than concurrent events.  For example, if one user
sends mail to a party who is not available, the
ability to forward the mail at a later time is
considered asynchronous.

(4) Starting the next I/O operation before the
current one is completed.

(5) In SCSI, the acknowledgment of each byte of
data transferred.

Contrast with synchronous.



asynchronous communications server
See ACS.



asynchronous I/O
Overlapping input and output with processing.  Both
the hardware and the software must be designed for
this capability.  The peripherals must be able to
run independent of the CPU, and the software must
be designed to manage it.



asynchronous protocol
A communications protocol that controls an
asynchronous transmission, for example, ASCII, TTY,
Kermit and Xmodem.  Contrast with synchronous
protocol.



asynchronous transfer mode
See ATM.



asynchronous transmission
The transmission of data in which each character is
a self-contained unit with its own start and stop
bits.  Intervals between characters may be uneven.
It is the common method of transmission between a
computer and a modem, although the modem may switch
to synchronous transmission to communicate with the
other modem.  Also called start/stop transmission.
Contrast with synchronous transmission.

  asynchronous
  transmission:  a bc   d    efg hi j kl    m

  synchronous
  transmission:  abcedefghijklm




AT
(Advanced Technology)  IBM's first 286-based PC,
introduced in 1984.  It was the most advanced
machine in the PC line and featured a new keyboard,
1.2MB floppy and 16-bit data bus.  AT-class
machines run considerably faster than XTs (8088-
based PCs).  See PC.



AT Attachment
See ATA.



AT bus
Refers to the 16-bit bus introduced with the IBM
AT.  It was the early term for what is today called
the "ISA bus."



AT class
Refers to second-generation PCs that use the 286
CPU and the 16-bit AT (ISA) bus.  In the mid 1980s,
AT class machines were the high-speed PCs of the
day.



AT command set
A series of machine instructions used to activate
features on an intelligent modem.  Developed by
Hayes Microcomputer Products, Inc., and formally
called the Hayes Standard AT Command Set, it is
used entirely or partially by most every modem
manufacturer.  AT is a mnemonic code for ATtention,
which is the prefix that initiates each command to
the modem.  See Hayes Smartmodem.



AT interface
See AT bus.  See also ATA.



AT keyboard
An 84-key keyboard provided with the PC AT.  It
corrected the non-standard placement of the PC's
return and left shift keys.  See PC keyboard and
Enhanced keyboard.



At Work
An operating environment from Microsoft designed
for office equipment such as telephones, copiers
and fax machines.  It comprises a realtime
operating system with a simple graphical user
interface for office machines, a communications
capability that provides secure transmission plus
the ability to print or display a document at a
remote device exactly the same as it was created.
At Work provides an interface for desktop Windows
applications in a PC to control At Work devices.



AT&T
(American Telephone & Telegraph Company)  The
largest long distance communications carrier in the
U.S.  Once the largest corporation in America, it
was relieved of its operating telephone companies
on January 1, 1984, by Federal court order.  It has
gone through a major change from the world's
largest monopoly to a competitive enterprise.  Its
early ventures into the PC market were modest, but
in 1991, AT&T acquired NCR, a seasoned computer
company, which is later renamed AT&T GIS.



AT&T GIS
(AT&T Global Information Solutions, Dayton, OH)
Formerly the NCR Corporation, AT&T GIS is a major
manufacturer of computers and financial terminals.
It was founded in 1884 when John Henry Patterson
purchased National Manufacturing Company of Dayton,
Ohio, and renamed it National Cash Register.  It
became the leading cash register company and, by
1911, had sold its one millionth machine.

   Starting in the 1930s, NCR made accounting
machines that posted customer accounts and became
successful in the banking and retail industries, in
which it has remained ever since.

   In 1957, it introduced the "304" transistorized
computer.  It accepted data from NCR cash registers
and banking terminals via paper tape.  The 304 was
very reliabile and widely accepted.

   NCR computer lines have included the Century
series (1960s), Criterion series (1970s) and the V
and I series (1980s).  Starting in 1982 with the
UNIX- and Motorola 68000-based Tower series, NCR
embraced open systems and industry standards.  In
1990, the x86-based System 3000 series was
introduced, a complete line from laptops to
massively parallel machines running DOS, Windows
and OS/2 at the low end and UNIX at the high end.

   In 1991, NCR was acquired by AT&T and operates
as a wholly-owned subsidiary.  It was renamed AT&T
GIS in January 1994.  The NCR name remains on ATM
and POS terminals as well as microelectronics and
business forms.  Computer systems use the AT&T
name.



ATA
(AT Attachment)  The interface specification for
IDE drives.  ATA is often not specified on
documents relating to IDE drives, but it is the
formal name for the IDE interface.  The ATA
interface is also used for PCMCIA solid state
disks.



Atari
(Atari Computer, Sunnyvale, CA)  A manufacturer of
personal computers founded in 1972 by Nolan
Bushnell and originally famous for its "Pong" video
games.  In 1976, it was sold to Time Warner, Inc.,
and in 1984 was acquired by Jack Tramiel and
investors.  Within six months, the 520ST was
introduced, the first personal computer designed
for MIDI applications.  Atari's product lines are
aimed at providing quality computing at affordable
prices.



ATE
(Automatic Test Equipment)  Machines that test
electronic systems, primarily chips.  See EDA and
DTA.



ATM
(1) (Asynchronous Transfer Mode)
(2) (Automatic Teller Machine)
(3) See Adobe Type Manager.

(1) (Asynchronous Transfer Mode)  A high-speed
cell-switching network technology for LANs and WANs
that handles data and realtime voice and video.  It
combines the high efficiency of packet switching
used in data networks, with the guaranteed
bandwidth of circuit switching used in voice
networks.  ATM is defined in the Broadband ISDN
(BISDN) standard.

   When implemented by the telephone companies, ATM
will provide "bandwidth on demand" by charging
customers for the amount of data they send rather
than fixed-cost digital lines (DS1, DS3, etc.) that
often go underutilized.  Unlike leased lines, which
are point to point, ATM can switch data to any ATM
node worldwide.

   ATM data rates are scalable starting as low as
1.5 Mbps with intermediate speeds of 25, 51 and 100
Mbps to high speeds of 155, 622 Mbps and up into
the gigabit range.

   ATM is currently used in LANs connecting high-
speed workstations, but adapters for personal
computers will be readily available in the 1994-
1995 time period.  It is envisioned that ATM will
become widely used for both LANs and WANs.

   ATM works by chopping all traffic into 53-byte
cells, or packets.  The fixed-length packet allows
very fast switches to be built, and the small
packet size ensures that voice and video frames can
be inserted into the stream often enough for
realtime transmission.

   ATM can also encompass frame relay traffic by
breaking up frame relay's variable-length frames
into ATM cells.  ATM provides network services at
the same level as Ethernet and Token Ring (OSI
layers 1 and 2).

   For an excellent booklet called "Asynchronous
Transfer Mode: Bandwidth for the Future," which
explains many technical details of ATM, contact
Advanstar Marketing Services, Cleveland, OH,
800/598-6008, fax 216/891-2726.  See ATM Forum.

(2) (Automatic Teller Machine)  A banking terminal
that accepts deposits and dispenses cash.  Stand
alone or online to a central computer, ATMs are
activated by inserting a cash or credit card that
contains the user's account number on a magnetic
stripe.



ATM Forum
A membership organization founded in 1991 to
promote ATM networking technology.  It works with
ANSI and ITU-TSS to set standards.  Its first
specification in 1992 defined the User-Network
Interface (UNI).  Technical committees work on
various projects in order to accelerate standards.
Address: 480 San Antonio Rd., Suite 100, Mountain
View, CA 94040, 415/962-2585 (fax 415/941-0849).



atom
In list processing languages, a single element in a
list.



atomic
Indivisible.  An atomic operation, or atomicity,
implies an operation that must be performed
entirely or not at all.  For example, if machine
failure prevents a transaction to be processed to
completion, the system will be rolled back to the
start of the transaction.  See two-phase commit.



attached processor
An additional CPU connected to the primary CPU in a
multiprocessing environment.  It operates as an
extension of the primary CPU and shares the system
software and peripheral devices.



attachment unit interface
See AUI.



attenuation
Loss of signal power in a transmission.



attribute
(1) In relational database management, a field
within a record.

(2) For printers and display screens, a
characteristic that changes a font, for example,
from normal to boldface or underlined, or from
normal to reverse video.

(3) See file attribute.



audio
The range of frequencies within human hearing
(approx. 20Hz at the low to a high of 20,000Hz).

   Traditional audio devices are analog, because
they handle sound waves in an analogous form.
Radios maintain the audio signal as rippling waves
from antenna to speaker.  Sound waves are "carved"
into plastic phonograph records, and audio tape
records sound as magnetic waves.

   Audio is processed in a computer by converting
the analog signal into a digital code using various
techniques, such as PCM.



audio adapter
Same as sound card.



audio board
Same as sound card.



audio CD
The music compact disc (CD) format that has
replaced the phonograph record.  Starting in the
early 1990s, certain stereo amplifiers and
receivers have come on the market without a phono
input, making the definitive statement that analog
phonograph records are history!  See CD and Red
Book.



audio response
See voice response.



audiotex
A voice response application that allows users to
enter and retrieve information over the telephone.
In response to a voice menu, users press the keys
or answer questions to select their way down a path
of choices.  It is used for obtaining the latest
financial quotes as well as for ordering products.
It is also built into interactive systems that
allows databases to be changed.  See VIS.



audiotext
Same as audiotex.



audiovisual
Audio and/or video capability.



audit
An examination of systems, programming and
datacenter procedures in order to determine the
efficiency of computer operations.



audit software
Specialized programs that perform a variety of
audit functions, such as sampling databases and
generating confirmation letters to customers.  It
can highlight exceptions to categories of data and
alert the examiner to possible error.  Audit
software often includes a non-procedural language
that lets the auditor describe the computer and
data environment without detailed programming.



audit trail
A record of transactions in an information system
that provides verification of the activity of the
system.  The simplest audit trail is the
transaction itself.  If a person's salary is
increased, the change transaction includes the
date, amount of raise and name of authorizing
manager.

   A more elaborate audit trail can be created when
the system is being verified for accuracy; for
example, samples of processing results can be
recorded at various stages.  Item counts and hash
totals are used to verify that all input has been
processed through the system.



AUI
(Attachment Unit Interface)  The network interface
used with standard Ethernet, which uses a thick
coaxial cable.  On the adapter card, it is a 15-pin
socket.  A transceiver, which taps into the
Ethernet cable, plugs into the socket.



authoring program
Software that allows for the development of
tutorials and CBT programs.



authorization code
An identification number or password that is used
to gain access to a local or remote computer
system.



Authorware Professional
A popular multimedia authoring program from
Macromedia that is widely used for creating
interactive learning programs on Windows and
Macintosh.  See Macromedia.



auto
(AUTOmatic)  Refers to a wide variety of devices
that perform unattended operation.



auto answer
A modem feature that accepts a telephone call and
establishes the connection.  See auto dial.



auto attendant
A voice store and forward system that replaces the
human operator and directs callers to the
appropriate extensions or voice mailboxes.



auto baud detect
A modem feature that detects the highest speed of
the called modem and switches to it.



auto bypass
The ability to bypass a terminal or other device in
a network if it fails, allowing the remaining
devices to continue functioning.



auto dial
A modem feature that opens the line and dials the
telephone number of another computer to establish
connection.  See auto answer.



auto line feed
A feature that moves the cursor or print head to
the next line when a CR (carriage return) is
sensed.  PCs put a LF (line feed) after the CR and
do not use this feature.  The Mac uses only a CR
for end of line and requires it.



auto logon
Performing the complete log-on sequence necessary
to gain entry into a computer system without user
intervention.



auto redial
A modem, fax or telephone feature that redials a
busy number a fixed number of times before giving
up.



auto reliable
A modem feature that enables it to send to a modem
with or without built-in error detection and
compression.



auto resume
A feature that lets you stop working on the
computer and take up where you left off at a later
date without having to reload applications.  Memory
contents are stored on disk or kept active by
battery and/or AC power.



autobaud rate
See ABR.



AutoCAD
A full-featured CAD program from AutoDesk Inc.,
Sausalito, CA, that runs on PCs, VAXs, Macs and
UNIX workstations.  Originally developed for CP/M
machines, it was one of the first major CAD
programs for personal computers and became an
industry standard.  There are countless third-party
add-on packages that are available for AutoCAD, and
many graphics applications import and export
AutoCAD's DXF file format.



autocoder
An IBM assembly language for 1960s-vintage 1400 and
7000 series computers.



AUTODIN
(AUTOmatic DIgital Network)  The worldwide
communications network of the U.S. Defense
Communications System.



AUTOEXEC.BAT
(AUTOmatic EXECute BATch)  A DOS batch file that
executes when the computer is started.  The OS/2
counterpart is STARTUP.CMD.  See DOS AUTOEXEC.BAT.



autoflow
Wrapping text around a graphic image or from one
page to the next.



AutoLISP
An AutoCAD language used to create customized menus
and routines.



automata theory
An open-ended computer science discipline that
concerns an abstract device called an "automaton,"
which performs a specific computational or
recognition function.  Networks of automata are
designed to mimic human behavior.



automatic call distribution
See ACD.



automatic data processing
Same as data processing.



automatic feature negotiation
The ability of a modem to determine and adjust to
the speed, error control and data compression
method of the modem at the other end of the line.



automatic number identification
See ANI.



automatic repeat request
See ARQ.



automatic teller machine
See ATM.



automatic test equipment
See ATE.



automation
The replacement of manual operations by
computerized methods.  Office automation refers to
integrating clerical tasks such as typing, filing
and appointment scheduling.  Factory automation
refers to computer-driven assembly lines.



automounting
Making remote files available to a client at the
time the file is accessed.  Remote directories are
associated with a local directory on the client
ahead of time, and the mounting takes places the
first time a remote file is opened by the client.



autosave
Saving data to the disk at periodic intervals
without user intervention.



autosizing
The ability of a monitor to maintain the same
rectangular image size when changing from one
resolution to another.



autostart routine
Instructions built into the computer and activated
when it is turned on.  The routine performs
diagnostic tests, such as checking the computer's
memory, and then loads the operating system and
passes control to it.



autotrace
A routine that converts a raster graphics image
into a vector graphics image.  It scans the bitmap
and turns the dark areas into vectors (lines).
Once a bitmap has been turned into vectors,
individual components of the drawing can be scaled
independently.

    This process usually creates many more vectors
than if the picture were drawn in a drawing program
in the first place.  In order to faithfully
reproduce the original, the conversion routine will
generate a vector for the slightest deviation in a
line.  However, extraneous vectors can be deleted
afterwards.



AUX
(AUXiliary)  The DOS name for the first connected
serial port.  See DOS device names.  See also A/UX.



auxiliary memory
A high-speed memory bank used in mainframes and
supercomputers.  It is not directly addressable by
the CPU, rather it functions like a disk.  Data is
transferred from auxiliary memory to main memory
over a high-bandwidth channel.  See auxiliary
storage.



auxiliary storage
External storage devices, such as disk and tape.



availability
See high availability.



AVC
(Audio Visual Connection)  Multimedia software from
IBM that works in conjunction with IBM's Audio
Capture and Video Capture boards for the PS/2.  It
allows users to integrate sound and pictures into
applications and includes an authoring language.



AVI
(Audio Video Interleaved)  A Windows multimedia
video format from Microsoft.  It interleaves
standard waveform audio and digital video frames
(bitmaps) to provide reduced animation at 15 fps at
160x120x8 resolution.  Audio is 11,025Hz, 8-bit
samples.



avionics
The electronic instrumentation and control
equipment used in airplanes and space vehicles.



Award BIOS
A PC-compatible ROM BIOS from Award Software, Inc.,
Los Gatos, CA.  By 1991, over 20 million Award
BIOS's have been installed.



awk
(Aho Weinberger Kernighan)  A UNIX programming
utility developed in 1977 by Aho, Weinberger and
Kernighan.  Due to its unique pattern-matching
syntax, it is often used in data retrieval and data
transformation.  DOS versions are also available.



Axiant
An application development system from Cognos for
client/server environments.  Built on Cognos'
PowerHouse 4GL, it supports Windows and Macintosh
clients and a variety of databases and UNIX
servers.  Cognos' Impromptu query language and
PowerPlay EIS/DSS system are components.  Also
included is the WATCOM/SQL database.



AXP
A family of computer systems from Digital that use
the Alpha CPU chip.  This series is expected to
take Digital throughout the 1990s and beyond.



azimuth
The trajectory of an angle measured in degrees
going clockwise from a base point.  A disk azimuth
alignment test checks for the correct positioning
of the read/write head to the track.



B/ISDN
(Broadband/ISDN)  See ISDN and ATM.



B protocol
A file transfer protocol from CompuServe.  Quick B
is a faster version only for downloading.  Later
versions of B will automatically select Quick B.



b-spline
In computer graphics, a curve that is generated
using a mathematical formula which assures
continuity with other b-splines.



B-tree
(Balanced-tree)  A technique for organizing
indexes.  In order to keep access time to a
minimum, it stores the data keys in a balanced
hierarchy that continually realigns itself as items
are inserted and deleted.  Thus, all nodes always
have a similar number of keys.

   B+tree is a version of B-tree that maintains a
hierarchy of indexes while also linking the data
sequentially, providing fast direct access and fast
sequential access.  IBM's VSAM uses this.



B1
The computer system security level required by the
Department of Defence (DOD).  See NCSC.



B:
The designation for the second floppy disk drive in
a PC.



Bachman tools
A variety of systems design, database
administration and system performance measurement
products from Bachman Information Systems, Inc.,
Burlington, MA.



back-end CASE
CASE tools that generate program code.  Contrast
with front-end CASE.



back end processor
Same as database machine.



back up
To make a copy of important data onto a different
storage medium for safety.



backbone
In communications, the part of a network that
handles the major traffic.  It often employs the
highest-speed transmission paths in the network and
may also run the longest distance.  Smaller
networks are attached to the backbone.

   A backbone can span a large geographic area or
be as small as a backplane in a single cabinet.
See collapsed backbone.



backdoor
See trapdoor.



backfilling
Assigning EMS memory to conventional memory in XTs
and ATs in order to let DESQview run more programs
concurrently.  Motherboard chips are disabled and
EMS chips are assigned the low memory addresses.



background
(1) Non-interactive processing in the computer.
See foreground/background.

(2) The base, or backdrop, color on screen.  For
example, in the DOS version of this database, the
text color is white on a blue background.



background ink
A highly reflective OCR ink used to print the parts
of the form not recognized by a scanner.



background noise
An extraneous signal that has crept into a line,
channel or circuit.



background processing
Processing in which the program is not visibly
interacting with the user.  Most personal computers
use operating systems that run background tasks
only when foreground tasks are idle, such as
between keystrokes.  Advanced multitasking
operating systems let background programs be given
any priority from low to high.



backing storage
Same as auxiliary storage.



backlit
An LCD screen that has its own light source from
the back of the screen, making the background
brighter and characters appear sharper.



BackOffice
A suite of network server software products from
Microsoft that includes Windows NT Server, SQL
Server, Systems Management Server (SMS), SNA Server
and Mail Server.



backplane
(1) The reverse side of a panel or board that
contains interconnecting wires.

(2) A printed circuit board, or device, containing
slots or sockets for plugging in boards or cables.
See bus.



backslash
See DOS backslash.



backsolver
See solver.



backspace
(1) To move the screen cursor one column to the
left, deleting the character that was in that
position.  A backspace to the printer moves the
print head one column to the left.

(2) To move to the previous block on a magnetic
tape.



backup
Additional resources or duplicate copies of data on
different storage media for emergency purposes.
See backup types.



backup & recovery
The combination of manual and machine procedures
that can restore lost data in the event of hardware
or software failure.  Routine backup of databases
and logs of computer activity are part of a backup
& recovery program.  See checkpoint/restart.



backup copy
A disk, tape or other machine readable copy of a
data or program file.  Making backup copies is a
discipline most computer users learn the hard way--
after a week's work is lost.



backup disk
A disk used to hold duplicate copies of important
files.  Floppy disks and disks cartridges are used
for backup disks.



backup power
An additional power source that can be used in the
event of power failure.  See UPS.



backup tape
See tape backup.



backup types
The selection of files for backup purposes.

   FULL BACKUP
   Backs up all selected files.

   DIFFERENTIAL BACKUP
   Backs up selected files that have been changed.
   This is used when only the latest version of a
   file is required.

   INCREMENTAL BACKUP
   Backs up selected files that have been changed,
   but if a file has been changed for the second or
   subsequent time since the last full backup, the
   file doesn't replace the already-backed-up file,
   rather it is appended to the backup medium. 
   This is used when each revision of a file must
   be maintained for backup.





Backus-Naur form
Also known as Backus normal form, it was the first
metalanguage to define programming languages,
developed by John Backus and Peter Naur in 1959.



backward chaining
In AI, a form of reasoning that starts with the
conclusion and works backward.  The goal is broken
into many subgoals or sub-subgoals which can be
solved more easily.  Known as top-down approach.
Contrast with forward chaining.



backward compatible
Same as downward compatible.



Bad command or file name
A DOS error message that means DOS does not
understand the command you entered, or it cannot
find the program you asked it to run.



bad sector
A segment of disk storage that cannot be read or
written due to a physical problem in the disk.  Bad
sectors on hard disks are marked by the operating
system and bypassed.  If data is recorded in a
sector that becomes bad, file recovery software,
and sometimes special hardware, must be used to
restore it.



BAK file
(BAcKup file)  A DOS and OS/2 file extension for
backup files.



BAL
(1) (Basic Assembly Language)  The assembly
language for the IBM 370/3000/4000 mainframe
series.

(2) (Branch And Link)  An instruction used to
transfer control to another part of the program.



ballistic gain
A trackball or mouse feature that changes cursor
travel relative to hand speed.  The faster the ball
is moved, the farther the cursor is moved.



baloon help
On-screen help displayed in a cartoon-style
dialogue box that appears when the pointer (cursor)
is placed over the object in question.



balun
(BALanced UNbalanced)  A device that connects a
balanced line to an unbalanced line; for example, a
twisted pair to a coaxial cable.  A balanced line
is one in which both wires are electrically equal.
In an unbalanced line, such as a coax, one line has
different properties than the other.



band
(1) The range of frequencies used for transmitting
a signal.  A band is identified by its lower and
upper limits; for example, a 10MHz band in the 100
to 110MHz range.

(2) A contiguous group of tracks that are treated
as a unit.

(3) The printing element in a band printer.



band pass filter
An electronic device that prohibits all but a
specific range of frequencies to pass through it.



band printer
A line printer that uses a metal band, or loop, of
type characters as its printing mechanism.  The
band spins horizontally around a set of hammers.
When the desired character is in front of the
selected print position, the corresponding hammer
hits the paper into the ribbon and onto the
character in the band.



bandwidth
The transmission capacity of a computer channel,
communications line or bus.  It is expressed in
cycles per second (Hertz), the bandwidth being the
difference between the lowest and highest
frequencies transmitted.  The frequency is equal to
or greater than the bits per second.  Bandwidth is
also often stated in bits or bytes per second.  See
video bandwidth.



bank
An arrangement of identical hardware components.



bank switching
Engaging and disengaging electronic circuits.  Bank
switching is used when the design of a system
prohibits all circuits from being addressed or
activated at the same time, requiring that one unit
be turned on while the others are turned off.



BAPC
(Business Applications Performance Corporation)  A
nonprofit organization founded in 1991 that
develops benchmarks for PC software.



bar chart
A graphical representation of information in the
form of bars.  See business graphics.



bar code
The printed code used for recognition by a scanner.
Traditional one-dimensional bar codes use the bar's
width as the code, but encode just an ID or account
number.  Two-dimensional systems, such as PDF 417
from Symbol Technology, hold 1,800 characters in an
area the size of a postage stamp.  See UPC.



barrel distortion
A screen distortion in which the sides bow out.
Contrast with pincushioning.



barrel printer
Same as drum printer.



base
(1) A starting or reference point.

(2) A component in a bipolar transistor that
activates the switch.  Same as gate in a MOS
transistor.

(3) A multiplier in a numbering system.  In a
decimal system, each digit position is worth 10x
the position to its right.  In binary, each digit
position is worth 2x the position to its right.



base address
The starting address (beginning point) of a program
or table.  See base/displacement and relative
address.



base alignment
The alignment of a variety of font sizes on a
baseline.



base/displacement
A machine architecture that runs programs no matter
where they reside in memory.  Addresses in a
machine language program are displacement
addresses, which are relative to the beginning of
the program.  At runtime, the hardware adds the
address of the current first byte of the program
(base address) to each displacement address and
derives an absolute address for execution.

   All modern computers use some form of
base/displacement or offset mechanism in order to
to run multiple programs in memory at the same
time.



base font
The default font used for printing if none other is
specified.



baseband
A communications technique in which digital signals
are placed onto the transmission line without
change in modulation.  It is usually limited to a
few miles and does not require the complex modems
used in broadband transmission.  Common baseband
LAN techniques are token passing ring (Token Ring)
and CSMA/CD (Ethernet).

   In baseband, the full bandwidth of the channel
is used, and simultaneous transmission of multiple
sets of data is accomplished by interleaving pulses
using TDM (time division multiplexing).  Contrast
with broadband transmission, which transmits data,
voice and video simultaneously by modulating each
signal onto a different frequency, using FDM
(frequency division multiplexing).

          Baseband (interleaves signals)
     
       data(1)  data(2)  data(3)  data(1)
     


           Broadband (true simultaneous)
     
       data(1)xxxxxxxxxxxxxxxxxxxxxxxxxxx
      
       voice(1)xxxxxxxxxxxxxxxxxxxxxxxxxx
      
       data(2)xxxxxxxxxxxxxxxxxxxxxxxxxxx
      
       data(3)xxxxxxxxxxxxxxxxxxxxxxxxxxx
     



baseline
The horizontal line to which the bottoms of
lowercase characters (without descenders) are
aligned.  See typeface.



baselining tool
A network monitor that analyzes communications
usage in order to establish routine traffic
patterns.



BASIC
(Beginners All purpose Symbolic Instruction Code)
A programming language developed by John Kemeny and
Thomas Kurtz in the mid 1960s at Dartmouth College.
Originally developed as an interactive, mainframe
timesharing language, it has become widely used on
small computers.

   BASIC is available in both compiler and
interpreter form.  As an interpreter, the language
is conversational and can be debugged a line at a
time.  BASIC is also used as a quick calculator.

   BASIC is considered one of the easiest
programming languages to learn.  Simple programs
can be quickly written on the fly.  However, BASIC
is not a structured language, such as Pascal, dBASE
or C, and it's easy to write spaghetti code that's
difficult to decipher later.

   The following BASIC example converts Fahrenheit
to Celsius:

   10 INPUT "Enter Fahrenheit "; FAHR
   20 PRINT "Celsius is ", (FAHR-32) * 5 / 9





basic encoding rules
See BER.



BASIC in ROM
A BASIC interpreter stored in a read only memory
chip that is available to the user at all times.



BAT file
(BATch file)  A file of DOS or OS/2 commands, which
are executed one after the other.  It has a .BAT
extension and is created with a text editor.  See
DOS batch file and DOS AUTOEXEC.BAT.



batch
A group, or collection, of items.



batch data entry
Entering a group of source documents into the
computer.



batch file
(1) A file containing data that is processed or
transmitted from beginning to end.

(2) A file containing instructions that are
executed one after the other.  See BAT file and
shell script.



batch file transfer
The consecutive transmission of two or more files.



batch job
Same as batch program.



batch operation
Some action performed on a group of items at one
time.



batch processing
Processing a group of transactions at one time.
Transactions are collected and processed against
the master files (master files updated) at the end
of the day or some other time period.  Contrast
with transaction processing.


         Batch and Transaction Processing
Information systems typically use both batch and
transaction processing methods.  For example, in an
order processing system, transaction processing is
the continuous updating of the customer and
inventory files as orders are entered.

   At the end of the day, batch processing programs
generate picking lists for the warehouse.  At the
end of some period, batch programs print invoices
and management reports.



batch program
A non-interactive (non-conversational) program such
as a report listing or sort.



batch session
Transmitting or updating an entire file.  Implies a
non-interactive or non-interruptible operation from
beginning to end.  Contrast with interactive
session.



batch stream
A collection of batch processing programs that are
scheduled to run in the computer.



batch system
See batch processing.



batch terminal
A terminal that is designed for transmitting or
receiving blocks of data, such as a card reader or
printer.



batch total
The sum of a particular field in a collection of
items used as a control total to ensure that all
data has been entered into the computer.  For
example, using account number as a batch total, all
account numbers would be summed manually before
entry into the computer.  After entry, the total is
checked with the computer's sum of the numbers.  If
it does not match, source documents are manually
checked against the computer's listing.



batteries
See lead acid, lithium ion, nickel cadmium, nickel
hydride and zinc air.



baud
(1) The signalling rate of a line.  It's the
switching speed, or number of transitions (voltage
or frequency changes) that are made per second.
Only at low speeds are bauds equal to bits per
second; for example, 300 baud is equal to 300 bps.
However, one baud can be made to represent more
than one bit per second.  For example, the V.22bis
modem generates 1200 bps at 600 baud.

(2) Commonly (and erroneously) used to specify bits
per second for modem speed; for example, 1200 baud
means 1200 bps.  See previous paragraph.



baud rate
A redundant reference to baud.  Baud is a rate.



baudot code
Pronounced "baw-doh."  One of the first standards
for international telegraphy developed in the late
19th century by Emile Baudot.  It uses five bits
per character.



Bay Networks
(Bay Networks, Inc., Santa Clara, CA)  A
communications products company that is the merger
in late 1994 of SynOptics Communications, Inc.,
Santa Clara, CA, and Wellfleet Communications,
Inc., Billerica, MA.  At the time of the merger,
SynOptics was number #1 in hubs, and Wellfleet was
number #2 in routers.

   The Bay name comes from Santa Clara being
located in the California Bay area and Billerica,
located in Massachusetts, which is known as the Bay
State.



BBS
(Bulletin Board System)  A computer system used as
an information source and message system for a
particular interest group.  Users dial into the
BBS, review and leave messages for other users as
well as communicate to other users on the system at
the same time.  BBSs are used to distribute
shareware and may provide access (doors) to other
application programs.

   Following is the national list of electronic
BBSs and online information services from
Boardwatch Magazine.


              BOARDWATCH MAGAZINE
               NATIONAL LIST OF
  ELECTRONIC BBSs AND ONLINE INFORMATION SERVICES
  (Copied with permission of Boardwatch Magazine),

              BOARDWATCH MAGAZINE
             5970 S. Vivian Street
              Littleton, CO 80127

           Information 303/973-6038
           Subscriptions 800/933-6038
           By modem (N81) 303/973-4222


           spt = technical support


ADA 9X Project (ADA programming)       800/232-9925
ADA Information Clearinghouse          703/614-0215
Advanced Data Services (6GB files)     301/695-9116
Albuquerque ROS (USA Today/tradewars)  505/299-5974
America's Suggestion Box (feedback)    516/471-8625

American Cybernetics (Multi-Edit spt)  602/968-1082
ANARC (World Radio/TV Handbook)        913/345-1978
APCUG (Association of PC User Groups)  408/439-9367
Applied Modeling Research (EPA models) 919/541-1325
Aquila (Fidonet/Interlink/Metronet)    708/820-8344

Argus Computerized Exchange (chat)     617/674-2345
AST Technical Services (product spt)   714/727-4723
AT&T Support (spt for AT&T PCs)        908/769-6397
ATI Support (modems & video cards)     416/756-4591
Atomic Cafe (Houston area BBS)         713/530-8875

Attention to Details (utilities/ASP)   714/681-6221
Audiophile Network (high end audio)    818/988-0452
Automobile Consumer Services (prices)  513/624-0552
AviTechnic (software/BBS)              301/252-0717
BBS America (DFW online newsletter)    214/680-3406

BCS BBS (LA's first Super BBS)         213/962-2902
BCS IBM (PC topics/TBBS software)      617/964-2540
BCS Info Center (general topics)       617/621-0882
BCS Mac (Mac topics/1stclass BBS)      617/864-0712
Beyond Eternity (EEEK! Bits magazine)  310/371-3734

Bird Info Network (exotic birds)       303/423-9775
BMUG (Mac support/files/conferences)   510/849-2684
Boardwatch Magazine Online Info        303/973-4222
Book BBS (info on 3K+ computer books)  215/657-6130
Book Stacks Unlimited (200K books)     216/694-5732

Borland Download BBS (utilies/examples)408/439-9096
Botnay Bay EIS (20GB files/adult/BBS)  603/431-7229
Boundary Waters (canoe/fishing/resorts)218/365-6907
Bruce's Bar & Grill (chat/games)       203/236-3761
C.A.R.L. Library Service (citations)   303/758-1551

CAD/Engineering Service                615/824-4938
Canada Remote Systems (23GB files)     416/798-4713
Capital PC User's Group BBS            301/738-9060
Castle Tabby (TABBY Fidonet for Mac)   908/988-0706
CBBS Chicago (BBS since 2/16/78)       312/545-8086

Celebration Station (games/children)   207/374-5161
Central Point Software (tech support)  503/690-6650
Channel 1 (70 lines/8GB files/Internet)617/354-8873
Chicago SysLink (Ferret/Pet/TRS80)     708/795-4442
chinet (Internet mail)                 312/283-0559

ClassiComputerFieds (classified ads)   317/359-5199
Classified Connection (nude GIF images)619/566-7347
Cleveland Freenet (city info/pub.libry)216/368-3888
Community News Service (news/entrtnmnt)719/520-5000
Community Link @DCWAS (DC tour info)   703/765-0501

Compact Audio Disk Exchange (buy/sell) 415/824-7603
Computer Business (book pub/Nick Anis) 714-396-0014
Computer Garden (treasure hunting)     301/546-1508
Computing Canada Online (PC newspaper) 416/497-5263
Corporate Data Exchange (PR Newswire)  609/683-4422

CrossTalk Technical Support            404/740-8428
Cul-de-Sac Bar & Grill (ham radio)     508/429-1784
CyberStore (CyberTools for BBSs)       604/526-3676
DAK Online Resource (mail order)       818/715-7153
Dark Side of the Moon (BBS software)   408/245-7726

Data Core (25 line major BBS)          310/842-6880
DataLink RBBS (satellite tracking)     214/394-7438
Dawg Byte (ANSI art club)              615/385-4268
Deep Cove (IBM/MAC/Amiga)              604/536-5885
Denver Exchange (gay/lesbian)          303/623-4965

Denver Free-Net (health info)          303/270-4865
DragonNet (4GB files/interactive games)409/765-5459
EarthArt (wildlife/conservation art)   803/552-4389
East Bay X-Change (XRS offline reader) 803/556-7485
Ed-Net (Vancouver education network)   604/732-8877

Electric Ideas Clearinghouse (energy)  206/586-6854
Electronic Publishers (news/finance)   503/624-4966
Electronic Zone (hypertext)            412/349-3504
Energy Info Admin (energy statistics)  202/586-8658
eSoft Product Support (Bread Board BBS)303/699-8222

Event Horizons (images/adult)          503/697-5100
Exchange BBS (gay/lesbian)             713/521-2191
EXEC-PC (largest U.S. BBS/280 lines)   414/789-4210
Executive Network (Interlink Netmail)  914/667-4567
Eye Contact (gay issues/chat)          415/255-5972

Falken Support (FALKEN software)       703/803-8000
Farwest (Western Canada Info System)   604/381-3934
FAX/Satellite (NOAA weather images)    619/224-3853
FCC Public Access (status advisory svc)301/725-1072
FEDLINK ALIX II (Federal libraries)    202/707-4888

Fido Software (Fido BBS 12s)           415/863-2739
Fido Tech Stand (Fidonet for Holland)  31-30-735900
FOG City 125/10 (AIDS info/DTP/Macs)   415/863-9697
Fred the Computer (Weirdnet Newswire)  508/872-8461
FreeBoard (desktop publishing)         804/744-0797

FSBBS Prototype System (FSUUCP & FSBBS)805/543-8227
Fun Connection (entertainment/news)    503/753-8431
Galacticomm Demo Sys (customer support)305/583-7808
Garbage Dump (chat/adventure games)    505/294-5675
Gateway Comm. (NetWare/TCP/IP utils.)  714/863-7097

Gateway On-line (chat/games/e-mail)    313/291-5571
GDP Technologies (PC shareware)        303/673-9470
General (files/GIF images)             619/281-8616
GISnet (GIS/mapping topics)            303/447-0927
GLIB (gay/lesbian info)                703/578-4542

GPO WINDO (EPA, DOE & State Dept info) 202/512-1387
Greenpeace Environet (ecological)      415/512-9108


           spt = technical support


Hayes Microcomputer (modem support)    800/874-2937
Heartland Free-net (community/Internet)309/674-1100
Herpnet/Satronics (reptile, amphibian) 215/698-1905
HH Info-Net (Windows, OS/2 files)      203/246-3747
HoloNet (Internet/Usenet/chat/GIF)     510/704-1058

Home Power Renewable Energy (magazine) 707/822-8640
HouseNet (home fixup/repairs/advice)   410/745-2037
Howard's Notebook (environment/peace)  816/331-5868
Hysterics (Amiga files)                613/231-7144
IBM National Support (PC users group)  404/835-5300

Inbound/Outbound/Teleconnect magazines 212/989-4675
Index Systems (Atlanta BBSs)           404/924-8414
Infinity World (text publications)     606/278-2002
InfoHost Demo (InfoHost BBS software)  201/335-2253
Infolink for Upper E. Tenn (space/chat)615/434-2551

Inns of Court (LAN related files)      214/458-2620
Intel PCEO Support (PC products spt)   503/645-6275
Invention Factory (shareware catalog)  212/274-8110
Investor's Online Data (stocks)        206/285-5359
JDR Microdevices (hardware catalog)    408/559-0253

JOBBS (technical job listings)         404/992-8937
Keith Graham Shareware (utilities)     914/623-0039
KIMBERELY (Fed Funds,T-bill data)      612/340-2489
King's Market (books/writers area)     303/665-6091
LANtastic technical support            602/293-8065

Late Night Software (UFGATE software)  415/695-0759
LegalEase (issues/forms)               509/326-3238
MAC-LINK (Macintosh support)           514/486-8959
Macalot (Second Sight BBS software spt)412/846-5312
MacCircles (Mac system software)       303/526-2219

Macinternational (largest Mac BBS)     803/798-3755
Magpie (Magpie BBS support)            212/420-0527
MaxiHost Support (Maxihost BBS)        209/836-2402
McAfee Associates (virus info)         408/988-4004
Meeting Works (convention planning)    212/737-6932

METRO Online (city info/ski/match/chat)212/831-9280
Micro Foundry, The (2GB files)         415/598-0398
Micro Message Service (news/files)     919/779-6674
Micro Tech (OSIRIS BBS support)        314/334-6359
Microrim Tech Support (R:Base spt)     206/649-9836

Microsoft Download (Windows support)   206/936-6735
Microsystems Software (for handicapped)508/875-8009
Mindvox (Internet/e-mail/FTP/TELNET)   212/988-5030
Minnesota Spacenet (NASA news)         612/920-5566
MOG-UR'S EMS (CD-ROMS, 2.8GB Hub Svcs) 818/366-1238

Mountain Air (adult)                   703/427-0226
Movie BBS (movie & TV reviews)         718/939-5462
N.A.C.D. (cave scuba diving)           912/246-3280
N8EMR Ham (ham radio)                  614/895-2553
NAPLPS Graphics (NAPLPS software)      613/727-5272

NASA Spacelink (flight data/history)   205/895-0028
Nashville Exchange (games/TDBS sftware)615/383-0727
National Genealogical (family history) 703/528-2612
Netcom Internet Guest System (lodging) 408/241-9760
Network World Bulletin Board (LAN/WAN) 508/620-1178

NIST ACTS (synchronize PC to NBS time) 303/494-4775
Nixpix (adult GIF images)              303/920-1263
NOAA Space Environment Lab(geomag data)303/497-5042
NoGate Consulting (PAK archive utility)616/530-3392
Numisnet (coin collecting)             301/498-8205


           spt = technical support


OAQPSTTN (air quality planning & stds) 919/541-5742
OASIS (Atlanta BBS list)               404/627-2662
Occupational Health/Safety (job safety)212/385-2034
Odyssey (adult chat/games/files)       818/358-6968
OERI (educational stats & data)        800/222-4922

Old Colorado City Comm. (political)    719/632-4111
Online Now (shareware)                 807/345-5522
Online With Hayes (conferences/SIGS)   404/446-6336
Oracle PC (South Australian TBBS)     6108 260-6222
Oracomm Support (Oracomm BBS software) 619/346-1608

Osprey's Nest (birdwatching/ecology)   301/989-9036
Ozone Hole (Boardwatch/USA Today/RIME) 504/891-3142
P.D.S.L.O. (national BBS list)         516/938-6722
PacComm (packet radio equipt. supplier)813/874-3078
PC Ohio (shareware)                    216/381-3320

Pennywise (office supply sales)        800/752-3012
PHYSICS Forum (physics/astronomical)   413/545-1959
Pinecliff (shareware)                  303/642-7463
Pinnacle Software (Sapphire BBS spt)   514/345-8654
PKWare (PKZIP technical support)       414/354-8670

Pleasure Dome (erotic/adult only)      804/490-5878
Practical Peripherals (modem support)  805/496-4445
ProComm Support                        314/875-0503
Promised Land (Windows files/chat)     715/387-1339
Public Brand Software (shareware sales)317/856-2087

Public Data Network ($2.50/hr access)  503/474-6662
QMail Deluxe Support (also 1stReader)  615/230-8822
Qualitas, Inc. (386MAX/BlueMAX spt)    301/907-8030
Quarterdeck (QEMM, DESQview support)   310/314-3227
QuickBBS technical support             407/896-0494

Random Access Info. Svc. (files/GIF)   503/695-3250
Ronin (file & message BBS)             214/938-2840
Rose Media (files/pubs/conferences)    416/733-2780
Rusty & Edies (NFL/tradewars)          216/726-0737
Sahara Club (land-use/off road/timber) 818/893-1899

Sailing IC (clubs/races/tall ships)    301/643-1466
Salt Air (PCBOARD BBS software)        801/261-8976
San Diego NeXt User's Group            619/456-2522
SBA Online (advice for small business) 800/697-4636
Science Resources Studies (fed budget) 202/634-1764

SDN Project, The (shareware)           203/634-0370
SEAboard! (ARC, SEADOG, AXE support)   804/442-6047
Seagate Technical Support (hard disks) 408/438-8771
Searchlight (Searchlight BBS support)  516/689-2566
SemWare Support (QEdit support)        404/641-8968

SENDIT (N. Dakota K-12 education)      701/237-3283
SIGCAT (CD-ROM-optical/Gov. CD data)   703/648-4168
Sistema Profesional Info (Mexico)      525 590-5988
Skeleton Closet (geneology programs)   804/671-8547
Society for Tech. Comm. (tech writers) 703/522-3299

Software Creations (Apogee software)   508/368-4137
Sonshine Express (Christian family)    510/651-2440
Sound Advice (files)                   816/436-4516
Source for Source (Clipper/XBase/etc)  516/968-7824
Spare Parts (Windows files)            817/540-3527

Star-Link Network (75K programs)       718/972-6099
Starlink (Predictive Maint. support)   915/235-4818
State and Local Emergency Management   202/646-2887
Superdemocracy Foundation (political)  305/370-9376
TAXACOM (botany/herbaria,online news)  716/896-7581

TEAMate Unix BBS (TEAMate BBS spt)     310/318-5302
Telebit Support (Telebit modems)       408/745-3229
Telegodzilla (home of ZModem)          503/621-3746
Telepath (Dr. Dobbs Journal online svc)415/358-8641
Telix Support (Telix comm. software)   919/481-9399

The Back Room (largest gay DB)         718/849-1614
The Business BBS (Windows support)     310/477-0408
The File Bank (radio/astronomy)        303/534-4646
The Ledge PCBoard (Textview Door)      818/896-4015
The Opowd Crowd (sports)               708/885-8865

The Other BBS (N.America Fidonet coord)717/657-2223
The Well (conferencing/hourly rate)    415/322-6106
Titan (adult/games/GIF images)         904/476-1270
Tool Shop (HS-Link)                    818/891-6780
Town Hall (conservative political)     800/648-6964

Trinity 1 (UK Distributor Boardwatch) 44 392 410210
TurBoard (NAPLPS graphics BBS system)  615/756-7810
U.S. Robotics (HST modem support)      708/982-5092
U.S. Naval Observatory (enter @TCO)    202/653-1079
USGS Quick Epicenter (earthquake data) 303/273-8672

USNO Time (sync your PC w/ atomic clk) 202/653-0351
UT Library Online Catalog (4M entries) 512/471-9420
Ventura Professional Forum (users grp) 408/227-4818
WeatherBank (forecast for any city)    800/827-2727
Western Digital Technical Support      714/753-1068

Westside (area's largest adult chat)   213/933-4050
Wildcat HQ (Wildcat BBS software spt)  805/395-0650
Windsor Manor (online adventure games) 203/688-4973
Wizard's Gate (free game/files/message)614/224-1635
WordPerfect Customer Support           801/225-4444

Worldview (Reformed Protestant topics) 510/676-2919
WWIV Support BBS (WWIV BBS software)   310/208-6689
XTree (support for XTree Pro Gold)     805/546-9150
XyQuest (XyWrite, Signature tech spt)  508/667-5669
Yellow Dream Machine (disability news) 512/451-3222





BCD
(Binary Coded Decimal)  The storage of numbers in
which each decimal digit is converted into binary
and is stored in a single character or byte.  For
example, a 12-digit number would take 12 bytes.
See numbers.



BCS
(1) (The Boston Computer Society)  A nonprofit
membership organization founded in 1977 by Jonathan
Rotenberg.  With over 28,000 members, it is the
world's largest personal computer association.
Services include user and special interest groups,
a subscription to BCS publications, access to the
Resource Center, public-domain software and
shareware.  Address: 101a 1st Avenue, Waltham, MA
02154, 617/252-0600.

(2) (Binary Compatibility Standard)  See ABI.

(3) (The British Computer Society)  Address: 13
Mansfield St., London, England W1M 0BP.



BDE
See Borland Database Engine.



BDOS error
See read error and write error.



beaconing
A continuous signalling of error conditions on a
LAN.



bead
(1) A small programming subroutine.  A sequence of
beads that are strung together is called a thread.

(2) The insulator surrounding the inner wire of a
coaxial cable.



BEL
See bell character.



Bell 103
An AT&T standard for asynchronous 300 bps full-
duplex modems using FSK modulation on dial-up
lines.



Bell 113
An AT&T standard for asynchronous 300 bps full-
duplex modems using FSK modulation on dial-up
lines.  The 113A can originate but not answer
calls, while the 113D can answer but not originate.



Bell 201
An AT&T standard for synchronous 2400 bps full-
duplex modems using DPSK modulation.  Bell 201B was
originally designed for dial-up lines and later for
leased lines.  Bell 201C was designed for half-
duplex operation over dial-up lines.



Bell 202
An AT&T standard for asynchronous 1800 bps full-
duplex modems using DPSK modulation over four-wire
leased lines as well as 1200 bps half-duplex
operation over dial-up lines.



Bell 208
An AT&T standard for synchronous 4800 bps modems.
Bell 208A is a full-duplex modem using DPSK
modulation over four-wire leased lines.  Bell 208B
was designed for half-duplex operation over dial-up
lines.



Bell 209
An AT&T standard for synchronous 9600 bps full-
duplex modems using QAM modulation over four-wire
leased lines or half-duplex operation over dial-up
lines.



Bell 212
An AT&T standard for asynchronous 1200 bps full-
duplex modems using DPSK modulation on dial-up
lines.



bell character
The control code used to sound an audible bell or
tone in order to alert the user (ASCII 7, EBCDIC
2F).



Bell compatible
A modem that is compatible with modems originally
introduced by the Bell Telephone System.



Bell Labs
The research and development center of AT&T and one
of the most renowned scientific laboratories in the
world.



Bell System
AT&T and the Bell Telephone Companies before
divestiture.  See divestiture and RBOC.



Bellcore
(BELL COmmunications REsearch)  The research and
development organization created at divestiture and
jointly owned by the regional Bell telephone
companies (RBOCs).  It is also involved in
communications issues of the U.S. government
regarding national security and emergency
preparedness.



benchmark
A test of performance of a computer or peripheral
device.  The best benchmark is the actual set of
application programs and data files that the
organization will use.  Running benchmarks on a
single user computer is reasonably effective;
however, benchmarking a multiuser system is
complicated.  Unless the user environment can be
duplicated closely, the benchmark may be
inaccurate.  See Linpack, Dhrystones, Whetstones,
Khornerstones and SPECmark.



BER
(1) (Basic Encoding Rules)  One method for encoding
information in the OSI environment.  For example,
it defines how Boolean data is coded.

(2) (Bit Error Rate)  The average number of bits
transmitted in error.



Berkeley extensions
See BSD UNIX.



Bernoulli Box
A removable disk system for personal computers from
Iomega Corporation, Roy, UT.  It uses a SCSI
interface.  Introduced in 1983, it used a 10MB, 8"
floppy disk cartridge.  In 1987, 20MB 5.25"
cartridges were introduced and later 44MB and 90MB.
The MultiDisk 150 (1992) accepts 35, 65, 90, 105
and 150MB cartridges.

   The name comes from 18th century Swiss
scientist, Daniel Bernoulli, who demonstrated fluid
dynamics principles.  Unlike a hard disk in which
the read/write head flies over a rigid disk, the
Bernoulli floppy is spun at high speed and bends up
close to the head.  Upon power failure, a hard disk
must retract the head to prevent a crash, whereas
the Bernoulli floppy naturally bends down.



Beta
The first home VCR format, which is now defunct.
Developed by Sony, it used 1/2" tape cassettes.
Beta Hi-fi added CD-quality audio, and SuperBeta
improved the image.  Today, VHS is the standard
1/2" VCR format.



beta test
A test of hardware or software that is performed by
users under normal operating conditions.  See alpha
test.



betaware
Software in beta test that has been provided to a
large number of users in advance of the formal
release.



Bezier
In computer graphics, a curve that is generated
using a mathematical formula which assures
continuity with other Bezier curves.  It is
mathematically simpler, but more difficult to blend
than a b-spline curve.  Within CAD and drawing
programs, Bezier curves are typically reshaped by
moving the handles that appear off of the curve.



BFT
(Binary File Transfer)  An extension to the fax
protocol that allows transmission of raw text
instead of an image of the text document.  The
ability to transfer actual data similar to a common
data modem provides a true e-mail capability via
fax boards.  A page of text (without graphics) is
also transmitted faster that a bitmap of the page
and is displayed at normal printer resolution at
the receiving side.



BI bus
A proprietary high-speed bus used in the VAX
series.



bi-endian
The ability to switch between big endian and little
endian ordering.  For example, the PowerPC is a bi-
endian CPU.



bias
The voltage used to control or stabilize an
electronic circuit.



BICSI
(Building Industry Consulting Services
International)  A membership organization devoted
to advancing its members in the field of
distributing low-level electronics within a
building.  It publishes the Telecommunications
Distribution Methods Manual and coordinates the
testing for the RCDD (Registered Communications
Distribution Designer), which is a certificate for
excellence in telecommunications distribution
design in commercial, campus and multi-family
buildings.



bidirectional
The ability to move, transfer or transmit in both
directions.



bidirectional printer
A printer that prints alternate lines from right to
left.



BIFF
(Binary Interchange File Format)  A spreadsheet
file format that holds data and charts, introduced
with Excel Version 2.2.



bifurcate
To divide into two.



Big Blue
Slang for IBM coined from the blue covers on most
of its earlier mainframes.



big endian
The order of bytes in a word in which the most
significant byte is first.  Little endian reverses
the order.  See bi-endian.

   16 bit number: 5A01h (23,041 decimal)
      Big endian: 5A01  (Motorola 68xxx)
   Little endian: 015A  (Intel x86)





bill of materials
The list of components that make up a system.  For
example, a bill of materials for a house would
include the cement block, lumber, shingles, doors,
windows, plumbing, electric, heating and so on.
Each subassembly also contains a bill of materials;
the heating system is made up of the furnace,
ducts, etc.  A bill of materials "implosion" links
component pieces to a major assembly, while a bill
of materials "explosion" breaks apart each assembly
or subassembly into its component parts.

   The first hierarchical databases were developed
for automating bills of materials for manufacturing
organizations in the early 1960s.



billion
One thousand times one million or 10 to the 9th
power.  See giga and nanosecond.



bin
(BINary)  A popular directory name for storing
executable programs, device drivers, etc. (binary
files).



binaries
Executable programs in machine language.



binary
Meaning two.  The principle behind digital
computers.  All input to the computer is converted
into binary numbers made up of the two digits 0 and
1 (bits).  For example, when you press the "A" key
on your personal computer, the keyboard generates
and transmits the number 01000001 to the computer's
memory as a series of pulses.  The 1 bits are
transmitted as high voltage; the 0 bits are
transmitted as low.  The bits are stored as charged
and uncharged memory cells in the computer.

   On magnetic disk and tape, the bits are stored
as positively and negatively charged spots.
Display screens and printers convert the binary
numbers into visual characters.

   The electronic circuits that process these
binary numbers are also binary in concept.  They
are made up of on/off switches (transistors) that
are electrically opened and closed.  The current
flowing through one switch turns on (or off)
another switch, and so on.  These switches open and
close in nanoseconds and picoseconds (billionths
and trillionths of a second).

   A computer's capability to do work is based on
its storage capacity (memory and disk) and internal
transmission speed.  Greater storage capacities are
achieved by making the memory cell or magnetic spot
smaller.  Faster transmission rates are achieved by
shortening the time it takes to open and close the
switch.  In order to increase computer performance,
we keep improving binary devices.


              How Binary Numbers Work
Binary numbers are actually simpler than decimal
numbers as they use only the digits 0 and 1 instead
of 0 through 9.

   In decimal, when you add 9 and 1, you get 10.
But, if you break down the steps you find that by
adding 9 and 1, what you get first is a result of 0
and a carry of 1.  The carry of 1 is added to the
digits in the next position on the left.  In the
following example, the carry becomes part of the
answer since there are no other digits in that
position.


    carry--1
            9
         +  1
         
           10

The following example adds 1 ten times in
succession.  Note that the binary method has more
carries than the decimal method.  In binary, 1 and
1 are 0 with a carry of 1.

  Binary   Decimal    Binary   Decimal
      0        0        101        5 
   +  1     +  1       +  1     +  1 
                    
      1        1        110        6 
   +  1     +  1       +  1     +  1 
                    
     10        2        111        7 
   +  1     +  1       +  1     +  1 
                    
     11        3       1000        8 
   +  1     +  1       +  1     +  1 
                    
    100        4       1001        9 
   +  1     +  1       +  1     +  1 
                    
    101        5       1010       10 





binary code
A coding system made up of binary digits.  See BCD,
data code and numbers.



binary compatible
Refers to any data, hardware or software structure
(data file, machine code, instruction set, etc.) in
binary form that is 100% identical to another.  It
most often refers to executable programs.



binary field
A field that contains binary numbers.  It may refer
to the storage of binary numbers for calculation
purposes, or to a field that is capable of holding
any information, including data, text, graphics
images, voice and video.  See BLOB.



binary file
(1) An executable program in machine language ready
to run.

(2) A file that contains binary numbers.



binary file transfer
See BFT.



binary format
(1) Numbers stored in pure binary form in contrast
with BCD form.  See binary numbers.

(2) Information stored in a binary coded form, such
as data, text, images, voice and video.  See binary
file, binary field and BLOB.

(3) A file transfer mode that transmits any type of
file without loss of data.



binary notation
The use of binary numbers to represent values.



binary numbers
Numbers stored in pure binary form.  Within one
byte (8 bits), the values 0 to 255 can be held.
Two contiguous bytes (16 bits) can hold values from
0 to 65,535.  See numbers and binary values.



binary search
A technique for quickly locating an item in a
sequential list.  The desired key is compared to
the data in the middle of the list.  The half that
contains the data is then compared in the middle,
and so on, either until the key is located or a
small enough group is isolated to be sequentially
searched.



binary synchronous
See bisync.



binary tree
A data structure in which each node contains one
parent and no more than two children.



binary values
The following table shows the maximum number of
numeric combinations in a binary structure with all
bits set to zero equivalent to one combination.
For example, in one bit, which can be 0 or 1, there
are two possible values.

 Bits       Total values
 1                 2
 2                 4
 3                 8
 4                16

 5                32
 6                64
 7               128
 8               256

 9               512
10             1,024   1K
11             2,048   2K
12             4,096   4K

13             8,192   8K
14            16,384  16K
15            32,768  32K
16            65,536  64K

17           131,072 128K
18           262,144 256K
19           524,288 512K
20         1,048,576   1M

21         2,097,152   2M
22         4,194,304   4M
23         8,388,608   8M
24        16,777,216  16M

25        33,554,432  32M
26        67,108,864  64M
27       134,217,728 128M
28       268,435,456 256M

29       536,870,912 512M
30     1,073,741,824   1G
31     2,147,483,648   2G
32     4,294,967,296   4G

33     8,589,934,592   8G
34    17,179,869,184  16G
35    34,359,738,368  32G
36    68,719,476,736  64G

37   137,438,953,472 128G
38   274,877,906,944 256G
39   549,755,813,888 512G
40 1,099,511,627,776   1T





bind
(1) To assign a machine address to a logical or
symbolic reference or address.

(2) To assign a type or value to a variable or
parameter.  See binding time.

(3) Bind may be used in place of terms such as link
or interface when referencing software that is made
to communicate with other software or with
hardware.  See linkage editor.



bindery
A NetWare file used for security and accounting in
NetWare 2.x and 3.x.  A bindery pertains only to
the server it resides in and contains the names and
passwords of users and groups of users authorized
to log in to that server.  It also holds
information about other services provided by the
server to the client (print, modem, gateway, etc.).

   NDS (NetWare Directory Service) is the bindery
counterpart in NetWare 4.x, but NDS is global
oriented, manages multiple servers and provides a
naming service, which the bindery does not.
Bindery emulation software enables NetWare 2.x and
3.x clients to access services on NetWare 4.x
servers.  See NDS.



binding time
(1) In program compilation, the point in time when
symbolic references to data are converted into
physical machine addresses.

(2) In programming languages, when a variable is
assigned its type (integer, string, etc.).
Traditional compilers and assemblers provide early
binding and assign types at compilation.  Object-
oriented languages provide late binding and assign
types at runtime when the variable receives a value
from the keyboard or other source.



biomechanics
The study of the anatomical principles of movement.
Biomechanical applications on the computer employ
stick modeling to analyze the movement of athletes
as well as racing horses.



bionic
A machine that is patterned after principles found
in humans or nature; for example, robots.  It also
refers to artificial devices implanted into humans
replacing or extending normal human functions.



BIOS
(Basic I/O System)  Detailed instructions that
activate peripheral devices.  Although BIOS's have
been around for more than 30 years, today, the term
generally refers to the ROM BIOS in a PC, which
holds certain parts of the operating system.  See
ROM BIOS.



bipolar
A category of high-speed microelectronic circuit
design, which was used to create the first
transistor and the first integrated circuit.  The
most common variety of bipolar chip is TTL
(transistor transistor logic).  Emitter coupled
logic (ECL) and integrated injection logic (I2L)
are also part of the bipolar family.

   Bipolar and MOS are the two major categories of
chip design.



bipolar transmission
A digital transmission technique that alternates
between positive and negative signals.  The 1s and
0s are determined by varying amplitudes at both
polarities while non-data is zero amplitude.



BIPS
(Billion Instructions Per Second)  See MIPS.



biquinary code
Meaning two-five code.  A system for storing
decimal digits in a four-bit binary number.



birefringence
Using a crystal to split light into two frequencies
that travel at different speeds and at right angles
to each other.  It's used to filter out a color in
an LCD display.



bis
Second version.  It means twice in Old Latin, or
encore in French.



BISDN
(Broadband ISDN)  See ISDN and ATM.



bison
The Free Software Foundation's version of yacc.



bistable circuit
Same as flip-flop.



bisync
(BInary SYNChronous)  A major category of
synchronous communications protocols used in
mainframe networks.  Bisync communications require
that both sending and receiving devices are
synchronized before transmission of data is
started.  Contrast with asynchronous transmission.



bisynchronous
See bisync.



bit
(BInary digiT)  A single digit in a binary number
(0 or 1).  Within the computer, a bit is physically
a transistor or capacitor in a memory cell, a
magnetic spot on disk or tape or a high or low
voltage pulsing through a circuit.  A bit is like a
light bulb: on or off.

   Groups of bits make up storage units in the
computer, called characters, bytes, or words, which
are manipulated as a group.  The most common is the
byte, made up of eight bits and equivalent to one
alphanumeric character.  See space/time.



bit cell
A boundary in which a single bit is recorded on a
tape or disk.



bit density
The number of bits that can be stored within a
given physical area.



bit depth
The number of bits used to represent an object.  It
typically refers to the number of colors that can
be displayed at one time, which is based on the
number of bits used to hold a pixel.  Digital video
requires at least 16 bits, while 24 bits produces
realistic TV-like colors.


   Color bit depth       Total number of colors

   4-bit (nibble)                16
   8-bit (one byte)             256
  16-bit (two bytes)         65,536
  24-bit (three bytes)   16,777,216
  32-bit (four bytes)    16,777,216 + alpha channel





bit error rate
See BER.



bit flipping
Same as bit manipulation.



bit level device
A device, such as a disk drive, that inputs and
outputs data bits.  Contrast with pulse level
device.



bit manipulation
Processing individual bits within a byte.  Bit-
level manipulation is very low-level programming,
often done in graphics and systems programming.



bit map
See bitmap.



bit-oriented protocol
A communications protocol that uses individual bits
within the byte as control codes, such as IBM's
SDLC.  Contrast with byte-oriented protocol.



bit parallel
The transmission of several bits at the same time,
each bit travelling over a different wire in the
cable.



bit pattern
A specific layout of binary digits.



bit plane
A segment of memory used to control an object, such
as a color, cursor or sprite.  Bit planes may be
reserved parts of a common memory or independent
memory banks each designed for one purpose.



bit rate
The transmission speed of binary coded data.  Same
as data rate.



bit serial
The transmission of one bit after the other on a
single line or wire.



bit slice processor
A logic chip that is used as an elementary building
block for the computer designer.  Bit slice
processors usually come in 4-bit increments and are
strung together to make larger processors (8 bit,
12 bit, etc.).



bit specifications
(1) The size of the computer's internal word, or
registers, which is the amount of data the CPU can
compute at the same time.  If the clock rates
(16MHz, 20MHz, etc.) and basic architecture are
equal, a 32-bit computer works twice as fast
internally as a 16-bit computer.

(2) The size of the computer's data bus, which is
the pathway over which data is transferred between
memory and the CPU and between memory and the
peripheral devices.  If the bus clock rates are
equal, a 16-bit bus transfers data twice as fast as
an 8-bit bus.

(3) The size of the address bus, which determines
how much memory the CPU can address directly.  Each
bit doubles the number, for example, 20-bits
addresses 1,048,576 bytes; 24-bits addresses
16,772,216 bytes.

(4) The number of colors that can be displayed at
one time.  Unless some of the memory is used for
cursor or sprite movement, an 8-bit graphics
adapter generates 256 colors; 16-bit, 64K colors;
24-bit, 16.8 million colors.  See alpha channel and
bit depth.

(5)  See binary values.



bit stream
The transmission of binary signals.



bit stuffing
Adding bits to a transmitted message in order to
round out a fixed frame or to break up a pattern of
data bits that could be misconstrued for control
codes.



bit twiddler
Same as hacker.



bit wise
See bitwise and bit manipulation.



bitblit
See bitblt.



bitblt
(BIT BLock Transfer)  In computer graphics, a
hardware feature that moves a rectangular block of
bits from main memory into display memory.  It
speeds the display of moving objects (animation,
scrolling) on screen.

   A hardware bitblt provides fastest speed, but
bitblts are also implemented in software even in
non-graphics systems.  For example, text scrolls
faster when it is copied as a contiguous block
(bitblt) to the next part of the window rather than
processing every character on every line.  See
stretch blt.



bite
See byte.



bitmap
A binary representation in which a bit or set of
bits corresponds to some part of an object such as
an image or font.  For example, in monochrome
systems, one bit in the bitmap represents one pixel
on screen.  For gray scale or color, several bits
in the bitmap represent one pixel or group of
pixels.  The term may also refer to the memory area
that holds the bitmap.

   A bitmap is usually associated with graphics
objects, in which the bits are a direct
representation of the picture image.  However,
bitmaps can be used to represent and keep track of
anything, where each bit location is assigned a
different value or condition.



bitmapped font
A set of dot patterns for each letter and digit in
a particular typeface (Times Roman, Helvetica,
etc.) for a specified type size (10 points, 12
points, etc.).  Bitmapped typefaces are either
purchased in groups of pre-generated point sizes,
or, for a wide supply of fonts, font generators
allow the user to create a variety of point sizes.
Bitmapped fonts take up disk space for each point
size.  Contrast with scalable font.  See font and
font generator.



bitmapped graphics
The raster graphics method for generating images.
Contrast with vector graphics and character
graphics.



BITNET
A worldwide communications network founded in 1981
that primarily serves higher education and
research.  It uses the NJE protocol for e-mail,
file transfers and short messages.  Well known for
its LISTSERV software for managing electronic
mailing lists, BITNET was for many years the
world's largest computer-based, higher-education
network.  It is gradually being supplanted by the
Internet.



bitwise
Dealing with bits rather than larger structures
such as a byte.  Bitwise operators are programming
commands or statements that work with individual
bits.  See bit manipulation.



BIX
(Byte Information eXchange)  An online database of
computer knowledge from BYTE magazine, designed to
help users fix problems and obtain info on hardware
and software products.  Address: 1030 Mass. Ave.,
Cambridge, MA 02138, 800/695-4775, 617/491-3393.
See online services.



bixie
See BICSI.



Black Apple
An early Apple II+ with a black case and external
audio controls.  Bell and Howell sold them in a
training kit.



black box
A custom-made electronic device, such as a protocol
converter or encryption system.  Yesterday's black
boxes often become today's off-the-shelf products.



Black Box Corporation
(Black Box Corporation, Pittsburgh, PA)  An
organization that specializes in communications and
LAN products.  It offers expert services, custom
solutions and hard-to-find products.



blank character
A space character that takes up one byte in the
computer just like a letter or digit.  When you
press the space bar on a personal computer
keyboard, the ASCII character with a numeric value
of 32 is created.



blank squash
The removal of blanks between items of data.  For
example, in the expression CITY + ", " + STATE, the
data is concatenated with a blank squash resulting
in  DALLAS, TX  rather than  DALLAS         TX.



bleed
Printing at the very edge of the paper.  Many laser
printers, including all LaserJets up the 11x17" 4V,
cannot print to the very edge, leaving a border of
approximately 1/4".  In commercial printing,
bleeding is generally more expensive, because wider
paper is often used, which is later cut to size.



Blenheim shows
The Blenheim Group PLC is a major producer of trade
shows and organizes more than 40 information
technology expositions around the world.  Annual
attendance is over 600,000 for all shows according
to Blenheim's news release in 1994.  PC EXPO is its
largest computer show.  Address: One Executive
Drive, Fort Lee, NJ 07024, 800/829-3976.


                 1994 Schedule

   NETWORKS EXPO '94 - Boston, Feb. 15-17
   NETWORKS EXPO '94 - San Francisco, Apr. 19-21
   NETWORKS EXPO '94 - Dallas, Sep. 20-22

   In Dallas, Networks Expo is combined with The
Interface Group's WINDOWS WORLD.


   PC EXPO - New York, June 28-30
   PC EXPO - Chicago, Oct. 19-21

   DB/EXPO '94 - San Francisco, May 24-26
   DB/EXPO '94 - New York, Dec. 6-8

   INTERACTIVE INFORMATION EXPO, New York, Dec. 6-8

   UNIX EXPO - New York, Oct. 4-6

   HRMS/EXPO '94 - San Jose, Oct. 24-25


                 1995 Schedule

   NETWORKS EXPO '95 - Boston, Feb. 14-16
   NETWORKS EXPO '95 - Dallas, Sep. 12-14

   In Dallas, Networks Expo is combined with The
Interface Group's WINDOWS WORLD.


   PC EXPO - New York, June 20-22
   PC EXPO - Chicago, Oct. 3-5

   DB/EXPO '95 - San Francisco, May 2-4
   DB/EXPO '95 - New York, Dec. 5-7

   UNIX EXPO - New York, Sep. 19-21

   HRMS/EXPO '95 - San Jose, Sep. 18-20





blip
A mark, line or spot on a medium, such as
microfilm, that is optically sensed and used for
timing or counting purposes.



blit
See bitblt.



blitting
Using a bitblt to transfer data.



BLOB
(Binary Large OBject)  A database field that holds
any digitized information.  This is one method of
storing multimedia objects (audio, video) in a
DBMS, since it holds any binary data.  However,
most relational DBMSs are better suited to small
fields typical of transaction data, such as name,
amount, etc.  The object-oriented DBMS is more
efficient for managing the storage of long, linear
amounts of data.  See object-oriented DBMS.



block
(1) A group of disk or tape records that is stored
and transferred as a single unit.

(2) A group of bits or characters that is
transmitted as a unit.

(3) A group of text characters that has been marked
for moving, copying, saving or other operation.



block device
A peripheral device that transfers a group of bytes
(block, sector, etc.) of data at a time such as a
disk.  Contrast with character device.



block diagram
A chart that contains squares and rectangles
connected with arrows to depict hardware and
software interconnections.  For program flow
charts, information system flow charts, circuit
diagrams and communications networks, more
elaborate graphical representations are usually
used.



block move
The ability to mark a contiguous segment of text or
data and move it.



blocking factor
The number of records in a block.



blow
To write code or data into a PROM chip by blowing
the fuses of the 0 bits.  The 1 bits are left
alone.



blow up
Same as crash, bomb or abend.



Blue Lightning
IBM's clock tripling version of the 486.  The first
model released at the end of 1993 is a 25MHz 486
with an internal speed of 75MHz.



BMP
(Bit MaP)  A Windows graphics format that may be
device dependent or independent.  Device
independent BMP files (DIB) are coded for
translation to a wide variety of displays and
printers.



BNC
(British Naval Connector)  A commonly used
connector for coaxial cable.  The plug looks like a
tiny tin can with the lid off and two short pins
sticking out on the upper edge on opposite sides.
After insertion, the plug is turned, tightening the
pins in the socket.



board
See printed circuit board and BBS.



board level
Electronic components that are mounted on a printed
circuit board instead of in a cabinet or finished
housing.



BOC
(Bell Operating Company)  One of 22 telephone
companies that was formerly part of AT&T and now
part of one of the seven regional Bell telephone
companies.



BOCOEX
(BOston COmputer EXchange)  See computer exchange.


body type
The typeface and size commonly used for text in
paragraph copy.  Typically 10 points.



BOF
(Beginning Of File)  The status of a file when it
is first opened or when an instruction or command
has reset the file pointer.



boilerplate
A common phrase or expression used over and over.
Boilerplate is stored on disk and copied into the
document as needed.



boldface
Characters that are heavier and darker on printed
output and brighter than normal on a display
screen.



boldface attribute
A code that turns normal characters into boldface
characters on a printer or display screen.



boldface font
A set of type characters that are darker and
heavier than normal type.  In a boldface font, all
characters have been designed as bold characters.



bomb
Same as abend and crash.



BOMP
(Bill Of Materials Processor)  One of the first
DBMSs used for bill of materials explosion in the
early 1960s from IBM.  A subsequent version, DBOMP,
was used in manufacturing during the 1970s.



books
See how to find a good computer book.



Boolean data
Yes/no or true/false data.



Boolean expression
A statement using Boolean operators that expresses
a condition which is either true or false.



Boolean logic
The "mathematics of logic," developed by English
mathematician George Boole in the mid 19th century.
Its rules govern logical functions (true/false).
As add, subtract, multiply and divide are the
primary operations of arithmetic, AND, OR and NOT
are the primary operations of Boolean logic.



Boolean operator
One of the Boolean logic operators such as AND, OR
and NOT.



Boolean search
A search for specific data.  It implies that any
condition can be searched for using the Boolean
operators AND, OR and NOT.  For example, the
English language request: "Search for all Spanish
and French speaking employees who have MBAs, but
don't work in Sales." is expressed in the following
dBASE command:

 list for degree = "MBA" .and.
   (language = "Spanish" .or. language = "French")
     .and. .not. department = "Sales"





boot
Causing the computer to start executing
instructions.  Personal computers contain built-in
instructions in a ROM chip that are automatically
executed on startup.  These instructions search for
the operating system, load it and pass control to
it.  Starting up a large computer may require more
button pushing and keyboard input.

   The term comes from "bootstrap," since
bootstraps help you get your boots on, booting the
computer helps it get its first instructions.  See
cold boot, warm boot and clean boot.



boot drive
A disk drive that contains the operating system.



boot failure
The inability to locate and/or read the operating
system from the designated disk.



boot record
See boot sector.



boot ROM
A memory chip that allows a workstation to be
booted from the server or other remote station.



boot sector
An area on disk (usually the first sectors in the
first disk partition) reserved for the operating
system.  On startup, the computer looks in the boot
sectors for the operating system, which must be
loaded first.



boot virus
A virus written into the boot sectors of a floppy
disk.  If the floppy is booted, it infects the
system.  For example, the Michelangelo virus, which
destroys data on March 6th, Michelangelo's
birthday, infects a computer if the virus diskette
is left in the drive and booted inadvertently when
the computer is turned back on.



bootable disk
A disk that contains the operating system in a form
ready to load into the computer.  It often refers
to a floppy disk that contains the operating system
in its boot sectors.  If a hard disk personal
computer does not find a bootable floppy disk in
the primary floppy drive at startup (A: in a PC),
it boots from the hard disk.

   It's a good idea to make a bootable disk for
your personal computer in case the hard disk
doesn't boot some day.  That way, you'll be able to
start the computer and access important data.  See
DOS Sys and DOS Format.



bootstrap
See boot.



Borland
(Borland International, Inc., Scotts Valley, CA)  A
leading PC software company founded in 1983 by
Philippe Kahn.  Its Turbo Pascal moved Pascal out
of the academic halls into a commercial product,
and its Turbo C has become an industry standard.
Borland C++ and Turbo Pascal for Windows are
committed to Windows and object-oriented
programming.

   In 1984, Borland's Sidekick was the first PC
desktop accessory program, which popularized TSRs
for DOS applications.

   With Borland's acquisition of Ansa's Paradox in
1987 and Ashton-Tate's dBASE in 1991, it has become
the leader in PC database software.  Using object-
oriented programming as the paradigm for the 1990s,
Borland plans to unify its applications and
languages into an interoperable family of products.
See Borland Database Engine.



Borland C++
An ANSI C and C++ compiler from Borland for DOS and
Windows applications.  It is Turbo C-compatible and
its debugger supports Windows programs written in
Microsoft C.  It includes application frameworks
for Windows (ObjectWindows) and DOS (Turbo Vision).
Borland C++ for OS/2 is also available.



Borland Database Engine
Software from Borland that runs on a Windows client
and unifies database access across multiple
platforms.  It is packaged separately as well as
with dBASE for Windows and Paradox for Windows.  It
allows dBASE and Paradox applications, as well as
C++ applications written to the IDAPI programming
interface, to access local dBASE and Paradox files
and to access remote Oracle, Sybase, Informix and
Interbase servers.  It also provides an ODBC socket
to connect an ODBC driver for remote access to any
ODBC-compliant database (DB2, Btrieve, etc.).



boss screen
A fake business-like screen that can be quickly
popped up over a game when the boss walks in.



Boston Computer Exchange
See computer exchange.



Boston Computer Society
See BCS.



Boundary Routing
3Com's trade name for remote office routing, which
it pioneered.  See remote-office router.



Bourne shell
See UNIX.



bpi
(Bits Per Inch)  The measurement of the number of
bits stored in a linear inch of a track on a
recording surface, such as on a disk or tape.



BPR
(Business Process Reengineering)  See
reengineering.



bps
(Bits Per Second)  The measurement of the speed of
data transfer in a communications system.



braces
Symbols used in programming and other technical
references to mark the beginning and end of a
contained area.  They are the { and } characters.



brains
A computer's "brains" are its central processing
unit.  See CPU.



branch
(1) Same as goto.

(2) A connection between two blocks in a flowchart
or two nodes in a network.



braze
To solder using metals with a very high melting
point, such as with an alloy of zinc and copper.



breadboard
A thin plastic board full of holes used to hold
components (transistors, chips, etc.) that are
wired together.  It is used to develop electronic
prototypes or one-of-a-kind systems.



break
To temporarily or permanently stop executing,
printing or transmitting.



break key
A keyboard key that is pressed to stop the
execution of the current program or transmission.



breakout box
A device inserted into a multiple-line cable for
testing purposes that provides an external
connecting point to each wire.  A small LED may be
attached to each line, which glows when a signal is
present.



breakpoint
The location in a program used to temporarily halt
the program for testing and debugging.  Lines of
code in a source program are marked for break
points.  When those instructions are about to be
executed, the program stops, allowing the
programmer to examine the status of the program
(registers, variables, etc.).  After inspection,
the programmer can step through the program one
line at a time or cause the program to continue
running either to the end or to the next break
point, whichever comes first.



BRI
See ISDN.



bridge
(1) To cross from one circuit, channel or element
over to another.

(2) A device that connects two LAN segments
together, which may be of similar or dissimilar
types, such as Ethernet and Token Ring.  Bridges
are inserted into a network to improve performance
by keeping traffic contained within smaller
segments.

   Bridges maintain address tables of the nodes on
the network through experience.  They learn which
addresses were successfully received through which
output ports by monitoring which station
acknowledged receipt of the address.

   Bridges work at the data link layer (OSI layer
2), whereas routers work at the network layer
(layer 3).  Bridges are protocol independent;
routers are protocol dependent.  Bridges are faster
than routers because they do not have to read the
protocol to glean routing information.  See
transparent bridge, repeater, router, gateway and
hub.



bridgeware
Hardware or software that converts data or
translates programs from one format into another.



Brief
A text editor for PC programming from Borland.  It
provides automatic indentation and the ability to
edit different parts of a source program at the
same time.



brightness
The light level on a display screen.  Contrast with
contrast.



British Telecom
A division of the British Post Office that manages
telecommunications throughout Great Britain and
Northern Ireland.



broadband
(1) A technique for transmitting data, voice and
video over long distances.  Using high frequency
transmission over coaxial cable or optical fibers,
broadband transmission requires modems for
connecting terminals and computers to the network.
Using the same FDM (frequency division
multiplexing) technique as cable TV, several
streams of data can be transmitted simultaneously.
Contrast with baseband.

(2) High-speed transmission.  Used in this manner,
the term generally refers to the highest-speed
technologies available or to ones just emerging.



broadband ISDN
See ISDN.



broadcast
To disseminate information to several recipients
simultaneously.



broadcast storm
Excessive tranmission of address resolution
requests in a network.  It can occur when multiple
routers come online or synchronize themselves
simultaneously, each trying to identify all the
connected nodes in the network.  Broadcast storms
can be lessened by properly designing and balancing
the number of nodes on each network segment.



Brooklyn Bridge
A PC file transfer program from Fifth Generation
Systems, Baton Rouge, LA, that transfers data
between laptops and desktop computers.



brouter
(Bridging ROUTER)  A communications device that is
part bridge and router.  Like a bridge, it
functions at the data link level (OSI layer 2) and
remains independent of higher protocols.  Like a
router, it manages multiple lines and routes
messages.  See router, gateway and hub.



browse
(1) To view the contents of a file or a group of
files.  Browser programs generally let you view
data by scrolling through the documents or
databases.  In a database program, the browse mode
often lets you edit the data.

(2) To view and edit the class hierarchy of the
objects in an object-oriented programming language.



BSC
(Binary Synchronous Communications)  See bisync.



BSD socket
A communications interface in UNIX first introduced
in BSD UNIX.  See UNIX socket.



BSD UNIX
(Berkeley Software Distribution UNIX)  A version of
UNIX developed by the Computer Systems Research
Group of the University of California at Berkeley
from 1979 to 1993.  BSD enhancements, known as the
"Berkeley Extensions," include networking, virtual
memory, task switching and large file names (up to
255 chars.).  BSD's UNIX was distributed free, with
a charge only for the media.  USL code is contained
in most BSD versions, and users require a valid USL
license in such cases.

   Bill Joy ran the group until 1982 when he co-
founded Sun Microsystems, bringing 4.2BSD with him
as the foundation of SunOS.  The last BSD version
released by BSD is 4.4BSD.

   BSDI (Berkeley Software Design, Inc.) a private
company founded in 1991 and headquartered in Falls
Church, VA, continues to develop BSD code.  In
1993, BSDI offers a complete version of BSD's NET 2
for x86 machines, which contains no USL code and
includes some GNU and other utilities.  Other
platforms are forthcoming.



BT
See British Telecom.



BT font
(BitsTream font)  Refers to fonts from Bitstream
Inc., Cambridge, MA.  See FaceLift and FontWare.



BTA
(Business Technology Association)  A membership
association of office equipment dealers founded in
1994.  It is a merger of NOMDA (National Office
Machine Dealers Association), founded in 1926, with
LANDA and AIMED (LAN Dealers Association and
Affiliated Independent Mailing Equipment Dealers).
Publications, training seminars and conferences are
provided for members.  Address: 12411 Wornall Rd.,
Kansas City, MO 64145, 816/941-3100.



BTAM
(Basic Telecommunications Access Method)  IBM
communications software used in bisynch, non-SNA
mainframe networks.  Application programs must
interface directly with the BTAM access method.



BTLZ
(British Telecom Lempel Ziv)  A data compression
algorithm based on the Lempel-Ziv method that can
achieve up to 4x the throughput of 2400 and 9600
bps modems.



BTOS
Burroughs' version of CTOS.



Btrieve
A file manager from Novell that accompanies its
NetWare operating systems.  It allows for the
creation of indexed files, using the b-tree
organization method.  Btrieve functions can be
called from within many common programming
languages.  See Xtrieve.



bubble
A bit in bubble memory or a symbol in a bubble
chart.



bubble chart
A chart that uses bubble-like symbols often used to
depict data flow diagrams.



Bubble Jet
Canon's ink jet printer technology.



bubble memory
A solid state semiconductor and magnetic storage
device suited for rugged applications.  It is about
as fast as a slow hard disk and holds its content
without power.

   It is conceptually a stationary disk with
spinning bits.  The unit, only a couple of square
inches in size, contains a thin film magnetic
recording layer.  Globular-shaped bubbles (bits)
are electromagnetically generated in circular
strings inside this layer.  In order to read or
write the bubbles, they are rotated past the
equivalent of a read/write head.



bubble sort
A multiple-pass sorting technique that starts by
sequencing the first two items, then the second
with the third, then the third with the fourth and
so on until the end of the set has been reached.
The process is repeated until all items are in the
correct sequence.



bucket
Another term for a variable.  It's just a place to
store something.



buckyballs
A type of carbon, identified in 1985, that has
potential as a superconductor.  It is one of a
group of "buckminsterfullerenes," named after R.
Buckminster Fuller, because of its molecular
similarity to his geodesic domes.



buffer
A reserved segment of memory used to hold data
while it is being processed.  In a program, buffers
are created to hold some amount of data from each
of the files that will be read or written.  A
buffer may also be a small hardware memory bank
used for special purposes.



buffer flush
The transfer of data from memory to disk.  Whenever
you command your application to save the document
you're working on, the program is actually flushing
its buffer (writing the contents of one or more
reserved areas of memory to the hard disk).

            Go Flush Your Cold Buffer!
Try this one out on your colleagues.  A cold buffer
is a reserved area of memory that contains data,
which hasn't been updated for a while.  Cold
buffers are flushed at periodic intervals.  More
importantly, this phrase sounds as strange as they
get.  Better yet, try "go flush your cold buffer
into your SCSI DASD" (pronounced scuzzy dazdy).  Be
sure to say this without cracking a smile, and
expect quite a grin from a systems professional.
If your friend doesn't understand this phrase, be
sure to recommend a good computer dictionary!



buffer pool
An area of memory reserved for buffers.



bug
A persistent error in software or hardware.  If the
bug is in software, it can be corrected by changing
the program.  If the bug is in hardware, new
circuits have to be designed.

   Although the derivation of bug is generally
attributed to the moth that was found squashed
between the points of an electromechanical relay in
a computer in the 1940s, the term was already in
use in the late 1800s.  See software bug.  Contrast
with glitch.


              A Note from the Author
On October 19, 1992, I found my first "real bug."
When I fired up my laser printer, it printed
blotchy pages.  Upon inspection, I found a bug
lying belly up in the trough below the corona wire.
The printer worked fine after removing it!



bug compatible
A hardware device that contains the same design
flaws as the original.



bulk storage
Storage that is not used for high-speed execution.
May refer to auxiliary memory, tape or disk.



Bull HN
(Bull HN Information Systems Inc., Billerica, MA)
The American subsidiary of the French company,
Compagnie des Machines Bull (CMB), founded in 1932.
The HN stands for Honeywell and NEC, which were
partners in joint development that had varying
amounts of ownership until 1991.

   CMB has been a major computer company in Europe
with partnerships and alliances throughout the
world.  Honeywell, a temperature control company
founded in 1927, became one of the first computer
companies in the U.S. when it created its computer
division in 1957.  It later acquired GE's computer
division.  When Honeywell withdrew from the
computer business, Bull took over the activities of
its American partner.

   Today, Bull offers networking and integration
services and a range of computer systems from
workstation to mainframe.  A complete line of PCs
is also available through the Zenith Data Systems
subsidiary, which CMB acquired in 1989.



bulletin board
See BBS.



bump mapping
In computer graphics, a technique for simulating
rough textures by creating irregularities in
shading.



BUNCH
(Burroughs, Univac, NCR, Control Data and
Honeywell)  IBM's competitors after RCA and GE got
out of the computer business.



bundle
To sell hardware and software as a single product
or to combine several software packages for sale as
a single unit.  Contrast with unbundle.



bunny suit
The protective clothing worn by an individual in a
clean room that keeps human bacteria from infecting
the chip-making process.  The outfit makes people
look like oversized rabbits.



burn in
To test a new electronic system by running it for
some length of time.  Weak components often fail
within the first few hours of use.



burst mode
A high-speed transmission mode in a communications
or computer channel.  Under certain conditions, the
system sends a burst of data at higher speed.  For
example, a multiplexor channel may suspend
transmitting several streams of data and send one
high-speed transmission using the entire bandwidth.



burster
A mechanical device that separates continuous paper
forms into cut sheets.  A burster can be attached
to the end of a collator, which separates multipart
forms into single parts.



bus
A common pathway, or channel, between multiple
devices.  A bus is always designed to attach
multiple devices, whereas channels such as the
serial port on a PC are used to connect only one
device.  Buses are generally hardware, although
software can be designed and linked via a so called
"software bus."

   A computer's internal bus is known as the local
bus, or processor bus, and connects the CPU to its
main memory and other bus controllers that connect
the peripheral devices.  If the peripheral buses
run at the high speeds of the CPU, such as the VL-
bus and the PCI bus, they are also called local
buses.  PC buses, such as ISA, EISA and Micro
Channel, run slower than the CPU and are not
referred to as local buses.  Examples of other
computer buses used in the industry are NuBus,
TURBOchannel, VMEbus, MULTIBUS and STD bus.

   Internal computer buses provide parallel data
transfer; for example, a 16-bit bus transfers two
bytes at a time over 16 wires, a 32-bit bus uses 32
wires, etc.  The bus is comprised of two parts: the
address bus and the data bus.  Addresses are sent
over the address bus to signal a memory location,
and the data is transferred over the data bus to
that location.

   Another common use of a bus is in a network.
For example, Ethernet is the most widely used
network topology and uses a serial bus.  Ethernet
is a common cable connecting all devices in the
network, and data is transmitted serially (one bit
after the other) over the cable.  A message, which
contains the address of the destination station, is
broadcast to all nodes at the same time, and the
destination station responds by accepting the
message.


         Computer Bus            Local Area Network
 Ŀ     Ŀ         Ŀ
           Ĵ   Main        Ĵ Client 
    CPU    LOCAL  Memory        Ĵ        
           ÿ   ڴ                 
 ٳ B      B Ŀ
 Ŀ U Ŀ     UĴ Client 
    VESA    S  PCI bus       SĴ        
 Controllerÿ   ڴController       
 ٳ          Ŀ
        Ŀ            Ĵ Server 
         ISA bus              Ĵ        
   VL   Controller  PCI        
   bus    bus        Ŀ
            ISA                Ĵ Client 
            bus               Ĵ        
                                 
                       
  The peripheral controller cards
  plug into slots on the ISA, PCI and VLbus buses
  (disk controller, display adapter (VGA),
  serial port, parallel port, SCSI controller,
  scanner card, CD-ROM card, sound card, etc.).



              Why Is It Called a Bus?
The term was coined after a real bus, because a bus
stops at all the bus stops on the route.  The same
goes for an electronic bus.  All signals on the bus
go to all stations or devices connected to it.





bus bridge
A device that connects two similar or dissimilar
busses together, such as two VMEbuses or a VMEbus
and a Futurebus.  This is not the same as a
communications bridge, which connects network
segments together.  See bridge.



bus card
An expansion board (card) that plugs into the
computer's expansion bus.



bus extender
(1) A board that pushes a printed circuit board out
of the way of surrounding boards for testing
purposes.  It plugs into an expansion slot, and the
expansion board plugs into the bus extender.

(2) A device that extends the physical distance of
a bus.  See repeater.

(3) A device that increases the number of expansion
slots.  It is either an expansion board containing
multiple expansion slots, or an expansion board
that cables to a separate housing that contains the
slots and its own power supply.



bus mastering
A bus design that allows add-in boards to process
independently of the CPU and to be able to access
the computer's memory and peripherals on their own.



bus mouse
A mouse that plugs into an expansion board.  It
takes up an expansion slot whereas a serial mouse
takes up a serial port.  The choice depends on how
many devices must be connected to each type of
socket.

   The connector on the mouse cable of a bus mouse
looks like the PS/2 mouse connector commonly used
to hook up an external mouse on a laptop, but the
pin configurations are different and not compatible
as shown in the diagram below.


              Pin Configurations

                            
                            
                            

      Bus connector     PS/2 connector





business analyst
An individual who analyzes the operations of a
department or functional unit with the purpose of
developing a general systems solution to the
problem that may or may not require automation.
The business analyst can provide insights into an
operation for an information systems analyst.



business graphics
Numeric data represented in graphic form.  While
line graphs, bar charts and pie charts are the
common forms of business graphics, there are dozens
of others types.  The ability to generate business
graphics is often included in spreadsheet and
presentation graphics programs.



business logic
The part of an application program that performs
the required data processing of the business.  It
refers to the routines that perform the data entry,
update, query and report processing, and more
specifically to the processing that takes place
behind the scenes.  A client application is made up
of a user interface and the business logic.  A
server application may be mostly business logic.

   Both client and server applications also require
communications links to the network, but they, like
the user interface, are not part of the business
logic.



business machine
Any office machine, such as a typewriter or
calculator, that is used in clerical and accounting
functions.  The term has traditionally excluded
computers and terminals.



business process reengineering
See reengineering.



Business Technology Association
See BTA.



Butterfly Switch
A parallel processing topology from BBN Advanced
Computers Inc., Cambridge, MA, that mimics a
crossbar and provides high-speed switching of data
between nodes.  It can also be used to create a
hypercube topology.



button
(1) A knob, such as on a printer or a mouse, which
is pushed with the finger to activate a function.

(2) A simulated button on screen that is "pushed"
by moving the cursor onto it and clicking the
mouse.



buy and sell
See used computers and computer exchange.



buying a personal computer
See how to select a personal computer.



bypass
In communications, to avoid the local telephone
company by using satellites and microwave systems.



byte
The common unit of computer storage from micro to
mainframe.  It is made up of eight binary digits
(bits).  A ninth bit may be used in the memory
circuits as a parity bit for error checking.

    A byte holds the equivalent of a single
character, such as the letter A, a dollar sign or
decimal point.  For numbers, a byte can hold a
single decimal digit (0 to 9), two numeric digits
(packed decimal) or a number from 0 to 255 (binary
numbers).

                Byte Specifications
The primary specifications of hardware are rated in
bytes; for example, a 40-megabyte (40M or 40MB)
disk holds 40 million characters of instructions
and data.  A one-megabyte (1M or 1MB) memory allows
one million characters of instructions and data to
be stored internally for processing.

   With database files and word processing
documents, the file size is slightly larger than
the number of data characters stored in it.  Word
processing files contain embedded codes for layout
settings (margins, tabs, boldface); therefore, a
100,000-byte document implies slightly less than
100,000 characters of text (approx. 30 pages).
Database files contain codes that describe the
structure of the records, thus, a 100,000-byte
database file holds somewhat less than 100,000
characters of data.

   Unlike data and text, a 100,000-byte graphics
file is not indicative of the size of the image
contained in it.  There are many graphics
standards, and the higher the image quality, the
more bytes are needed to represent it.  A low-
resolution graphics file can take as little as
8,000 bytes, while high-resolution files can take
100,000 or more bytes per picture.



byte addressable
A computer that can address each byte of memory
independently of the others.  In today's computers,
all of memory is usually byte addressable, which is
why memory is used for processing.  Units (fields)
of data can be worked on independently.  Contrast
with word addressable.



Byte Information Exchange
See BIX.



byte ordering
See big endian.



byte-oriented protocol
A communications protocol that uses control codes
made up of full bytes.  The bisynchronous protocols
used by IBM and other vendors are examples.
Contrast with bit-oriented protocol.



C
A high-level programming language developed at Bell
Labs that is able to manipulate the computer at a
low level like assembly language.  During the last
half of the 1980s, C has become the language of
choice for developing commercial software.

   C can be compiled into machine languages for
almost all computers.  For example, UNIX is written
in C and runs in a wide variety of micros, minis
and mainframes.

   C is programmed as a series of functions that
call each other for processing.  Even the body of
the program is a function named "main."  Functions
are very flexible, allowing programmers to choose
from the standard library that comes with the
compiler, to use third party functions from other C
suppliers, or to develop their own.

   Compared to other high-level programming
languages, C appears complicated.  Its intricate
appearance is due to its extreme flexibility.  C
was standardized by ANSI (X3J11 committee) and ISO
in 1989.  See Turbo C, Borland C++, Microsoft C and
Visual C++.


   The following C example converts fahrenheit to
centigrade:

     main()   {
     float fahr;
     printf("Enter Fahrenheit ");
     scanf("%f", &fahr);
     printf("Celsius is %f\n", (fahr-32)*5/9);
              }


   A C example used to create the DOS version of
this database follows the next paragraph.


                  The Origin of C
C was developed to allow UNIX to run on a variety
of computers.  After Bell Labs' Ken Thompson and
Dennis Ritchie created UNIX and got it running on
several PDP computers, they wanted a way to easily
port it to other machines without having to rewrite
it from scratch.  Thompson created a language
called B, a simpler version of a language called
BCPL, itself a version of CPL.  Later, in order to
improve B, Thompson and Ritchie created C.


               DOS Version Code in C
Following is the main event loop in the DOS engine
for this database, which is written in Turbo C.
The main loop of an interactive program repeats
continuously, testing all possible menu selections,
keystrokes and mouse clicks that the user may
enter.

   The WHILE (1) statement below creates a
continuous loop.  An instruction at the END OF
EVENT LOOP points to the beginning of the loop.

   The names with double parentheses are the names
of subroutines, for example, bookmark().  When
bookmark() is called, the instructions in the
bookmark function set the bookmark and control is
returned to the BREAK.  The BREAK ends the loop in
order to start over at the beginning.



  /*********** MAIN EVENT LOOP **********/

while (1)        /* BEGINNING OF LOOP */
 {

  while (!charwait())  if (mouse) testMOUSE();

  if (mouse)
   {
     if (mouseDOWNinText)
          {
     mouseDOWNinText=0;
     CLICK=1;
     unHighLightALL();
          }
   }


  key1=getch();   /* get keystroke from keyboard */
  if (key1==0)    /* if 0, a second character is */
  {               /*  required (key2)            */
   key2=getch();  /* get second character        */
   switch (key2)  {     /* test contents of key2 */
    case 59: HelpTopic=NO;
             HelpRoutine(); break;   /* F1*/
    case 68: main_menu();   break;   /*F10*/
    case 61: PrevHistory(); break;   /* F3*/
    case 62: NextHistory(); break;   /* F4*/
    case 63: bookmark();    break;   /* F5*/
    case 64: findmark();    break;   /* F6*/
    case 71: home_key();    break;
    case 79: end_key();     break;
    case 75: left_arrow();  break;
    case 77: left_arrow();  break;
    case 72: up_arrow();    break;
    case 80: down_arrow();  break;
    case 73: pageup();      break;
    case 81: pagedown();    break;
    case 132: ctrl_PgUp();  break;
    case 118: ctrl_PgDn();  break;
                  }
  }
 else
    {
   switch (key1)  {
    case 8:  backspace();    break;
    case 9:  left_arrow();   break;   /*Tab*/
    case 127: ctrl_bsp();    break;
    case 13: return_key();   break;
    case 27: escape_key();   break;
    case 2:  bookmark();     break;  /*Ctrl-B*/
    case 6:  findmark();     break;  /*Ctrl-F*/
    case 24: alldone();              /*Ctrl-X*/
    case 17: alldone();              /*Ctrl-Q*/
    default: dataentry();    break;
                  }
    }

 } /** END OF EVENT LOOP **/





c/s
See client/server.



C/S ELEMENTS
An object-oriented client/server development system
from Neuron Data, Palo Alto, CA, that is used to
develop applications for all the major GUIs,
including Windows, OS/2, Motif and Mac.  It
supports more than 40 platforms and provides links
to its rule-based NEXPERT expert system.



C shell
See UNIX.



C++
An object-oriented version of C created by Bjarne
Stroustrup.  C++ has become popular because it
combines traditional C programming with OOP
capability.  Smalltalk and other original OOP
languages did not provide the familiar structures
of conventional languages such as C and Pascal.
See Borland C++ and Visual C++.



C2
The minimum security level defined by the National
Computer Security Center.  See NCSC.



C:
A designation for the primary hard disk in a PC.



CA
(Computer Associates International, Inc., Islandia,
NY)  The world's largest diversified software
vendor offering more than 350 applications from
micro to mainframe.  Founded in 1976 by Charles
Wang and three associates, its first product was
CA-SORT, an IBM mainframe utility.  In personal
computers, it was originally known for SuperCalc,
one of the first spreadsheets.  With 1994 revenues
exceeding two billion dollars, CA is concentrating
heavily in the Windows market.  CA has acquired
several software companies with well-known
products, all of which are now titled with the CA-
designation.



CA-Clipper
An application development system from Computer
Associates.  Originally a dBASE compiler, it has
become a complete stand-alone development
environment with many unique features.  Clipper was
originally developed by Nantucket Corporation.



CA-Cricket Presents
A desktop presentation program for the Macintosh
from Computer Associates.  It provides the ability
to create output for overheads, handouts, speaker
notes and film recorders.



CA-DATACOM/DB
A relational database management system (DBMS) from
Computer Associates that runs on PCs, IBM minis and
mainframes.  There are many options and add-ons
that support the product all under the CA-DATACOM
umbrella, such as CA-DATACOM/CICS Services and CA-
DATACOM/SQL Option.



CA-dBFast
A dBASE-compatible application development system
from Computer Associates.  It provides over 200
language extensions to dBASE allowing dBASE or
xBASE programs to be converted to Windows
applications.



CA-Easytrieve
An application development system for IBM
mainframes, DOS and OS/2 from Computer Associates.
It includes 4GL query and reporting capabilities
and can access many IBM mainframe and PC database
formats.  UNIX and Windows versions forthcoming.
Easytrieve was originally developed by Pansophic
Systems.



CA-IDMS
A relational DBMS from Computer Associates that
runs on minis and mainframes.  IDMS (Integrated
Data Management System) was developed at GE in the
1960s and marketed by Cullinane, later renamed
Cullinet and then acquired by CA in 1989.  There
are a variety of CA-IDMS products, such as CA-
IDMS/R for the relational DBMS, CA-IDMS/DDS for its
distributed version and so on.



CA-Ingres
The original version of CA-OpenIngres from Computer
Associates.  See CA-OpenIngres.



CA-Librarian
A version control system for IBM mainframes from
Computer Associates.  Librarian's master files can
be simultaneously accessed on shared disks by
different operating systems.  Librarian was
originally developed by ADR, Inc.



CA-OpenIngres
A relational database management system (DBMS) from
Computer Associates that runs on Windows NT, OS/2,
VAXs and most UNIX platforms.  CA-OpenIngres is an
enhanced version of Ingres, one of the first
heavyweight DBMSs and noted for its advanced
features.  For example, Ingres was the first major
DBMS to include triggers and stored procedures.

   Ingres was originally developed by Relational
Technology, founded in 1980 to market a commercial
version of "INteractive Graphics and REtrieval
System," which was developed at the University of
California at Berkeley in the early 1970s.  The
company was renamed Ingres Corporation, then later
acquired by the Ask Group and eventually Computer
Associates.



CA-OpenRoad
A client/server development system from Computer
Associates that runs on Windows, X terminal and
OS/2 clients.  It supports the major SQL databases
including CA-OpenIngres.  CA-OpenRoad was
originally Windows 4GL from Ingres, but supported
only the Ingres database.



CA-Panvalet
A version control system for IBM mainframes from
Computer Associates that keeps track of source
code, JCL and object modules.  Panvalet was
originally developed by Pansophic Systems.  CA-
PAN/LCM is a similar product for PCs, which also
provides interfaces to mainframe systems, such as
CA-Panvalet and CA-Librarian.



CA-RAMIS
A fourth-generation retrieval language for IBM
mainframes and PCs from Computer Associates.
Originally developed by Mathematica, RAMIS was
later acquired by Martin Marietta Data Systems, On-
Line Software, then CA in 1991.  The earliest
version of RAMIS was one of the first database
packages with a non-procedural language for IBM
mainframes.



CA-Realizer
A Windows development software from Computer
Associates that uses a structured superset of
BASIC, has its own forms design utilities and
includes a runtime module.  Realizer was originally
developed by Within Technologies.



CA-Telon
An application generator from Computer Associates
that generates COBOL and PL/I code for IBM
mainframes and COBOL code for AS/400s.  Development
can be performed on mainframes or PCs.  Telon was
originally developed by Pansophic Systems.



cable
A flexible metal or glass wire or group of wires.
All cables used in electronics are insulated with a
material such as plastic or rubber.



cable categories
The following categories are based on their
transmission capacity.  The majority of new wiring
installations use Category 5 UTP wire in order to
be able to run or upgrade to the faster network
technologies that will require it.  Categories 1
through 5 are based on the EIA/TIA-568 standard.


  Category   Cable type     Application

    1      UTP           Analog voice
    2      UTP           Digital voice, 1 Mbps data
    3      UTP, STP      16 Mbps data
    4      UTP, STP      20 Mbps data
    5      UTP, STP      100 Mbps data
    6      Coax          100 Mbps+ data
    7      Fiber optic   100 Mbps+ data





cable matcher
Same as gender changer.



cable modem
A modem used to connect a computer to a cable TV
system that offers online services.



cable types
See cable categories.



cabletext
A videotex service that uses coaxial cable.  See
videotex.



cache
Pronounced "cash."  A dedicated bank of high-speed
memory or a reserved section of regular memory used
to improve performance.  The cache provides a
temporary storage area for instructions and data
that is closer to the CPU's speed.  The larger the
cache, the faster the performance, since there is a
greater chance that the instruction or data
required next is already in the cache.

                   Memory Caches
A memory cache, also called a CPU cache, is a high-
speed memory bank that sits between memory and the
CPU.  The cache is composed typically of SRAM
chips, which provide faster access to the memory
bits than the common DRAM chips used for most main
memories.

   Blocks of instructions and data are copied from
regular memory into the cache.  Instructions are
then read faster and data is read and written
faster, because it is in the higher-speed cache.

   A level 1 cache (L1 cache) is an internal cache
built into the CPU chip.  A level 2 cache (L2
cache) is an external cache of memory chips plugged
into the motherboard.  Both types are routinely
used together.

   The larger the L2 cache, the better.  However,
whether you will notice any significant improvement
in performance between a 128K and 256K cache for
example, depends on your applications.  The mix of
instructions within the program determines how
efficient the cache will be.  Since this is an
unknown, only comparing the same application on
identical machines with different caches will tell.
In addition, one motherboard manufacturer can
design its cache circuits better than another.


                    Disk Caches
A disk cache is a reserved section of normal memory
or an additional memory bank on the disk controller
board.  When the disk is read, a large block of
data is copied into the cache from the disk.  If
subsequent requests for data can be satisfied in
the cache, a slower disk access is not required.

   If the cache is used for writing, data is queued
up in the cache at high speed and then written to
the disk during idle machine cycles or on its own
power if the cache is built into the disk hardware.

   Disk caches that use regular memory are managed
by a disk caching program, such as SmartDrive,
which accompanies DOS and Windows.  Disk caches
built into the disk controller are managed by the
hardware on the board itself.  See write back
cache.


 Ŀ     Ŀ     Ŀ
     RAM    High-speed   CPU  
      Memory bank     
                   
               Memory cache (CPU cache)


        disk       Ŀ     Ŀ
    RAM    CPU  
        Cache      
                   
                      Disk cache





cache coherency
Managing a cache so that data is not lost or
overwritten.  For example, when data is updated in
a cache, but not yet transferred to its target
memory or disk, the chance of corruption is
greater.  Cache coherency is obtained by well-
designed algorithms that keep track of the cache.
It is even more critical in symmetric
multiprocessing (SMP) where memory is shared by
multiple processors.



caching controller
A disk controller with a built-in cache.  See
cache.



CAD
(Computer-Aided Design)  Using computers to design
products.  CAD systems are high-speed workstations
or personal computers using CAD software and input
devices such as graphic tablets and scanners.  CAD
output is a printed design or electronic input to
CAM systems (see CAD/CAM).

   CAD software is available for generic design or
specialized uses, such as architectural, electrical
and mechanical design.  CAD software may also be
highly specialized for creating products such as
printed circuits and integrated circuits.

   CAD systems are often turnkey systems which are
put together by vendors that may develop or
integrate software into standard or optimized
hardware.  Except in a few cases, CAD systems rely
extensively on graphics.  See graphics, CADD, and
CAE.



CAD/CAM
(Computer-Aided Design/Computer-Aided
Manufacturing)  The integration of CAD and CAM.
Products designed by CAD are direct input into the
CAM system.  For example, a device is designed and
its electronic image is translated into a numerical
control programming language, which generates the
instructions for the machine that makes it.



CADAM
A full-featured IBM mainframe CAD application,
which includes 3-D capability, solid modeling and
numerical control.  Originally developed by
Lockheed for internal use, it was distributed by
IBM starting in the late 1970s.  In 1989, IBM
purchased the Lockheed subsidiary, CADAM, Inc.



CADD
(Computer-Aided Design and Drafting)  CAD systems
with additional features for drafting, such as
dimensioning and text entry.



CADKEY
An integrated 2-D drafting and 3-D design system
for PCs from CADKEY, Inc., Manchester, CT.  It
offers a total design solution with solids creation
and built-in DXF and IGES translators.  Over 200
manufacturing systems link to CADKEY through its
CADL programming language.



CAE
(1) (Computer-Aided Engineering)  Software that
analyzes designs which have been created in the
computer or that have been created elsewhere and
entered into the computer.  Different kinds of
engineering analyses can be performed, such as
structural analysis and electronic circuit
analysis.

(2) (Common Application Environment)  Software
development platform that is specified by X/Open.



CAI
(1) (Computer-Assisted Instruction)  Same as CBT.

(2) See CA.



Cairo
The code name for an object-oriented version of
Windows NT to be released after Windows NT is
established.



CAL
(1) (Computer-Assisted Learning)  Same as CBT.

(2) (Conversational Algebraic Language)  A
timesharing language from the University of
California.



calculated field
A numeric or date field that derives its data from
the calculation of other fields.  Data is not
entered into a calculated field by the user.



calculator
A machine that provides arithmetic capabilities.
It accepts keypad input and displays results on a
readout and/or paper tape.  Unlike a computer, it
cannot handle alphabetic data.



call
(1) In programming, a statement that references an
independent subroutine or program.  The call is
turned into a branch instruction by the assembler,
compiler or interpreter.  The routine that is
called is responsible for returning to the calling
program after it has finished processing.

(2) In communications, the action taken by the
transmitting station to establish a connection with
the receiving station in a dial-up network.



call by reference
In programming, a call to a subroutine that passes
addresses of the parameters used in the subroutine.



call by value
In programming, a call to a subroutine that passes
the actual data of the parameters used in the
subroutine.



call control
Also called call processing, it is the controlling
of telephone and PBX functions.  It includes
connecting, disconnecting and transferring the
call, but it does not affect the content of the
call.  Contrast with media control.



call distributor
A PBX feature that routes incoming calls to the
next available agent or operator.



Call Level Interface
See CLI.



called routine
In programming, a program subroutine that performs
a task and is accessed by a call or branch
instruction in the program.



calling program
In programming, a program that initiates a call to
another program.



calling routine
In programming, a program subroutine that initiates
a call to another program routine.



CALS
(Computer-Aided Acquisition and Logistics Support)
A DOD initiative for electronically capturing
military documentation and linking related
information.



CAM
(1) (Computer-Aided Manufacturing)  The automation
of manufacturing systems and techniques, including
numerical control, process control, robotics and
materials requirements planning (MRP).  See
CAD/CAM.

(2) (Common Access Method)  An ANSI standard
interface that provides a common language between
drivers and SCSI host adapters.  It is primarily
supported by Future Domain and NCR.  See ASPI.

(3) (Content Addressable Memory)  Same as
associative storage.



Canadian Standards Association
See CSA.



candela
A unit of measurement of the intensity of light.
An ordinary wax candle generates one candela.  See
lumen.



canned program
A software package that provides a fixed solution
to a problem.  Canned business applications should
be analyzed carefully as they usually cannot be
changed much, if at all.



canned routine
A program subroutine that performs a specific
processing task.



canonical synthesis
The process of designing a model of a database
without redundant data items.  A canonical model,
or schema, is independent of the hardware and
software that will process the data.



capacitor
An electronic component that holds a charge.  It
comes in varying sizes for use in power supplies to
the tiny cells in dynamic RAM chips.



capstan
On magnetic tape drives, a motorized cylinder that
traps the tape against a free-wheeling roller and
moves it at a regulated speed.



capture buffer
A reserved memory area for holding an incoming
transmission.



CAR
(Computer-Assisted Retrieval)  Systems that use the
computer to keep track of text documents or records
stored on paper or on microform.  The computer is
used to derive the location of a requested item,
which must be manually retrieved from a shelf, bin,
or microform.



card
See printed circuit board, magnetic stripe, punched
card and HyperCard.



card cage
A cabinet or metal frame that holds printed circuit
cards.



card column
A vertical column that is used to represent a
single character of data by its pattern of punched
holes.  The common IBM card contains 80 card
columns.



card image
The representation of punched cards in which each
hole in the card is represented by a bit on tape or
disk.



card punch
(1) An early peripheral device that punches holes
into cards at 100 to 300 cards per minute.

(2) Same as keypunch machine.



card reader
(1) A peripheral device that reads magnetic stripes
on the back of a credit card.

(2) An early peripheral device that reads punched
cards at 500 to 2,000 cards/minute.  The code is
detected by light patterns created by the holes in
the card.



card services
Software that manages PCMCIA cards.  See PCMCIA.



cardinal number
The number that states how much or how many.  In
"record 43 has 7 fields," the 7 is cardinal.
Contrast with ordinal number.



caret
An up-arrow (^) symbol used to represent a decimal
point or the control key.  For example, ^Y means
Ctrl-Y.  It is Shift-6 on the keyboard.



carpal tunnel syndrome
The compression of the main nerve to the hand due
to scarring or swelling of the surrounding soft
tissue in the wrist (area formed by carpal bones on
top and muscle tendons below).  Caused by trauma,
arthritis and improper positioning of the wrist, it
can result in severe damage to the hands.  See RSI
and Wrist Pro.



carriage
A printer or typewriter mechanism that holds the
platen and controls paper feeding and movement.



carriage return
See return key.



carrier
An alternating current that vibrates at a fixed
frequency, used to establish a boundary, or
envelope, in which a signal is transmitted.
Carriers are commonly used in radio transmission
(AM, FM, TV, microwave, satellite, etc.) in order
to differentiate transmitting stations.  For
example, an FM station's channel number is actually
its carrier frequency.  The FM station merges
(modulates) its audio broadcast (data signal) onto
its carrier and transmits the combined signal over
the airwaves.  At the receiving end, the FM tuner
latches onto the carrier frequency, filters out the
audio signal, amplifies it and sends it to the
speaker.

   Carriers can be used to transmit several signals
simultaneously.  For example, multiple voice, data
and/or video signals can travel over the same line
with each residing in its own carrier vibrating at
a different frequency.



carrier based
A transmission system that generates a fixed
frequency (carrier) to contain the data being
transmitted.



carrier detect
A signal that indicates a connection has been made
by sensing a carrier frequency on the line.  See
RS-232 and modem.



carrier frequency
A unique frequency used to "carry" data within its
boundaries.  It is measured in cycles per second,
or Hertz.  See carrier and FDM.



Carterfone decision
The FCC decree in 1968 that permitted users to
connect their own telephone equipment to the public
telephone system.



cartridge
A self-contained, removable storage module that
contains disks, magnetic tape or memory chips.
Cartridges are inserted into slots in the drive,
printer or computer.  See font cartridge.



CAS
(Communications Application Specification)  Intel's
fax/modem protocol that allows personal computers
to exchange data with fax machines.  Introduced in
1988, Intel provides both the boards and the chips.



cascade
A connected series of devices or images.  It often
implies that the second and subsequent device takes
over after the previous one is used up.  For
example, cascading tapes in a dual-tape backup
system means the second tape is written after the
first one is full.  In a 286 or higher PC, a second
IRQ chip is cascaded to the first, doubling the
number of interrupts.  Cascaded windows look like
this:

      window 1Ŀ
        window 2Ŀ
          window 3Ŀ
                                     




CASE
(Computer-Aided Software Engineering or Computer-
Aided Systems Engineering)  Software that is used
in any and all phases of developing an information
system, including analysis, design and programming.
For example, data dictionaries and diagramming
tools aid in the analysis and design phases, while
application generators speed up the programming
phase.

   CASE tools provide automated methods for
designing and documenting traditional structured
programming techniques.  The ultimate goal of CASE
is to provide a language for describing the overall
system that is sufficient to generate all the
necessary programs.  See also case statement.



case-based reasoning
An AI problem solving technique that catalogs
experience into "cases" and matches the current
problem to the experience.  Such systems are easier
to maintain than rule-based expert systems, because
changes require adding new cases without the
complexity of adding new rules.  It is used in many
areas including pattern recognition, diagnosis,
troubleshooting and planning.



case cracker
A tool used to "crack" open the cases of various
laptop computers.  The early Macintosh cases and
many laptop cases are designed to snap together.
The spatula-like ends of the case cracker make it
easier to pry open the case without damaging it.



case sensitive
Distinguishing lower case from upper case.  In a
case sensitive language, "abc" is considered
different data than "ABC."



case statement
In programming, a variation of the if-then-else
statement that is used when several ifs are
required in a row.  The following C example tests
the variable KEY1 and performs functions based on
the results.

  switch (key1)   {
    case '+':  add();  break;
    case '-':  subtract();  break;
    case '*':  multiply();  break;
    case '/':  divide();  break;
                   }


   For a more extensive example of the case
statement, see the last example under "C."



cash memory
See cache.



cassette
A removable storage module that contains a supply
reel of magnetic tape and a takeup reel.  Data
cassettes look like audio cassettes, but are made
to higher tolerances.



casting
In programming, the conversion of one data type
into another.



cat
(conCATenate)  A UNIX command that displays the
contents of a file.



catalog
A directory of disk files or files used in an
application.  Also any map, list or directory of
storage space used by the computer.



Category 3, 5, etc.
See cable categories.



cathode
In electronics, a device that emits electrons,
which flow from the negatively charged cathode to
the positively charged anode.



cathode ray tube
See CRT.



CATV
(Community Antenna TV)  The original name for cable
TV, which used a single antenna at the highest
location in the community.  Now refers to cable TV.



CAU
(Controlled Access Unit)  An intelligent hub from
IBM for Token Ring networks.  Failed nodes are
identified by the hub and reported via IBM's LAN
Network Manager software.



CAV
(Constant Angular Velocity)  A disk technique that
spins the disk at a constant speed.  The number of
bits in each track is the same, but their density
varies because the inner tracks have smaller
circumferences than the outer tracks.  Contrast
with CLV.



CB
(Citizen's Band)  The frequency band for public
radio transmission in the 27 MHz range.



CB simulator
See teleconferencing (3).



CBEMA
(Computer and Business Equipment Manufacturers
Association)  A membership organization founded in
1916 composed of over 25 manufacturers and
suppliers.  It is concerned with the development of
standards for data processing and business
equipment in the U.S. and abroad.  Address: 311
First St., N.W., Washington, DC 20001, 202/737-
8888.



CBR
(1) (Computer-Based Reference)  Reference materials
accessible by computer in order to help people do
their jobs quicker.  For example, this database on
disk!

(2) (Constant Bit Rate)  A uniform transmission
rate.  For example, voice traffic requires a CBR.

(3) See case-based reasoning.



CBT
(Computer-Based Training)  Using the computer for
training and instruction.  CBT programs are called
courseware and provide interactive training
sessions for all disciplines.  It uses graphics
extensively, as well as CD-ROM and LaserDisc.

   CBT courseware is developed with authoring
languages, such as Adroit, PILOT and Demo II, which
allow for the creation of interactive sessions.



CBX
(Computerized Branch eXchange)  Same as PBX.



cc:Mail
A widely-used messaging system from Lotus that runs
on PC LANs.  Originally developed by cc:Mail, Inc.,
Mountain View, CA, Lotus acquired the company in
1991.  Mail-enabled applications that are written
to the VIM programming interface can use the
cc:Mail system.



CCA
(1) (Common Cryptographic Architecture)  IBM
encryption software for MVS and DOS applications.

(2) (Compatible Communications Architecture)  A
Network Equipment Technology protocol for
transmitting asynchronous data over X.25 networks.

(3) (Communications Control Architecture)  The U.S.
Navy network that includes an ISDN backbone called
BITS (Base Information Transfer System).



CCC/Harvest
A software configuration management (SCM) system
for client/server environments from Softool
Corporation, Goleta, CA.  It supports all the major
UNIX platforms and Windows, OS/2 and NT clients.
Other products from Softool include CCC/Manager for
VAXes and CCC/LCM for mainframes.



CCD
(Charge Coupled Device)  An electronic memory made
of a special type of MOS transistor that can store
patterns of charges in a sequential fashion.  CCDs
are used in TV and scanning devices since they can
be charged by light as well as by electricity.



CCFL
(Cold Cathode Flurorescent Lamp)  Same as CCFT.



CCFT
(Cold Cathode Fluorescent Tube)  A type of light
source for a backlit screen.  It weighs more and
uses more power than other backlights.



CCIA
(Computer and Communications Industry Association)
A membership organization composed of over 60
hardware and software vendors, service bureaus,
leasing and repair companies.  It represents their
interests in domestic and foreign trade, and,
working with the NIST, keeps members advised of
regulatory policy.  Address: 666 11th St., N.W.,
Washington, DC 20001, 202/783-0070.



CCIS
(Common Channel Interoffice Signaling)  A telephone
communications technique that transmits voice and
control signals over separate channels.  Control
signals are transmitted over a packet-switched
digital network, providing faster connects and
disconnects and allowing data, such as calling
number, to be included.  See CCS (2).



CCITT
See ITU-TSS.



CCP
(Certificate in Computer Programming)  The award
for successful completion of an examination in
computer programming offered by ICCP.



CCS
(1) (Common Communications Support)  SAA
specifications for communications, which includes
data streams (DCA, 3270), application services
(DIA, DDM), session services (LU 6.2) and data
links (X.25, Token Ring).

(2) (Common Channel Signaling)  An integral part of
ISDN known as "Signaling System 7," which advances
the CCIS method for transmitting control signals.
It allows call forwarding, call waiting, etc., to
be provided anywhere in the network.

(3) (Common Command Set)  The de facto instruction
set between a SCSI-1 adapter and a hard disk.

(4) (Continuous Composite Servo)  A magneto-optic
format that places the signal track between two
alignment tracks.

(5) (100 Call Seconds)  A unit of measurement equal
to 100 seconds of conversation.  One hour = 36 CCS.



CD
(1) (Compact Disc)
(2) See carrier detect.

(1) (Compact Disc)  A digital audio disc that
contains up to 72 minutes of hi-fi stereo sound.
The disc is a plastic platter 4.75" in diameter,
recorded on one side, with individual selections
playable in any sequence.  The CD was introduced in
1982.

   Sound is converted into digital code by sampling
the sound waves 44,056 times per second and
converting each sample into a 16-bit number.  It
requires approximately 1.5 million bits of storage
for each second of stereo hi-fi sound.

   Other forms of CDs (CD-ROM, CD-ROM XA, CD-I and
DVI) all stem from the audio CD.


                     The Books
Documentation for various CD formats are found in
books commonly known by the color of their covers.

      Red Book    - Audio CDs
      Yellow Book - CD-ROM
      Orange Book - Write-once (Photo CD, etc.)
      Green Book  - CD-I
      White Book  - Video CD


         What Happened to the Phonograph?
The audio CD was introduced in the U.S. in 1983.
Three years later, sales of CDs and CD players
exceeded sales of LPs and turntables.

   Unlike phonograph records, in which the platter
contains "carved sound waves," CDs are recorded in
digital form as microscopic pits (binary code)
covered by a clear, protective plastic layer.
Instead of a needle vibrating in the groove, a
laser shines onto the pits and the reflections are
decoded.

  Digital sound is so clear because the numbers are
turned into sound electronically.  There's no
needle pops and clicks as there are with phonograph
records (there's also no tape hiss if the original
recording was digital).  In addition, the CD can
handle a wider range of volume (dynamic range),
providing more realism.  A soft whisper can be
interrupted by a loud cannon blast.  If a
phonograph record were recorded with that much
dynamic range, the needle would literally jump out
of the groove.



CD audio
Same as CD and DAD.



CD caddy
A plastic container that holds a CD-ROM disc.  The
caddy is inserted into the disc drive.



CD-I
(Compact Disc-Interactive)  A compact disc format
developed by Philips and Sony that holds data,
audio, still video and animated graphics.  It
provides up to 144 minutes of CD-quality stereo,
9.5 hours of AM-radio-quality stereo or 19 hours of
monophonic audio.

   CD-I includes an operating system standard as
well as proprietary hardware methods for
compressing the data further in order to display
video images.  CD-I discs require a CD-I player and
will not play in a CD-ROM player.  See CD, CD-ROM,
DVI.



CD-R
(CD-Recordable)  A recordable CD-ROM technology
using a disc that can be written only once.  The
CD-R drives that write the CD-R discs are also
called one-off machines.  CD-R discs are used for
beta versions and original masters of CD-ROM
material as well as a means to distribute a large
amount of data to a small number of recipients.

   CD-R discs are also used for archiving data.
Their advantage over WORM drives is that the discs
can be read on any CD-ROM drive.  Most CD-R drives
can also be used as a regular CD-ROM reader.

   The recording process takes from 20 minutes to
an hour per disc depending on the speed of the
drive.  While this may be suitable for archiving or
small distributions, large numbers of CD-ROMs are
duplicated on a pressing machine from the original
CD-R master disk.



CD recorder
See CD-R.



CD-ROM
(Compact Disc Read Only Memory)  A compact disc
format used to hold text, graphics and hi-fi stereo
sound.  It's like an audio CD, but uses a different
track format for data.  The audio CD player cannot
play CD-ROMs, but CD-ROM players usually play audio
CDs and have output jacks for a headphone or
amplified speakers.

   A CD-ROM player connects to a controller card,
which is plugged into one of the computer's
expansion slots.  Most CD-ROMs use the SCSI
interface and can be daisy chained to an existing
SCSI controller.  Some come with their own
proprietary contoller and will not work with any
other.

   CD-ROMs hold in excess of 600MB of data, which
is equivalent to about 250,000 pages of text or
20,000 medium-resolution images.

   Earlier CD-ROM drives transfer data at 150KB per
second.  Double, triple and quad-spin drives
provide 2x, 3x and 4x the 150KB transfer rate.
Access times run from a slow half second to under
200 milliseconds.

   Audio and data reside on separate tracks and
cannot be heard and viewed together on earlier
drives that are not CD-ROM XA compliant.  See CD-
ROM XA, CD-I and DVI.



CD-ROM audio cable
The cable used to pass analog sound from a CD-ROM
drive to the sound card.  It is required when you
want to play audio CDs on your CD-ROM drive;
however, there are several implementations.
Connectors on sound cards use five or six-pins,
while connectors on the CD-ROM drive use from three
to six.  Earlier CD-ROM drives have none.

   In lieu of this connection, a stereo cable from
the headphones jack of the CD-ROM to the AUDIO IN
of the sound card can always be used.  This is one
reason for purchasing a multimedia upgrade kit,
which includes the sound card and CD-ROM drive.
The right audio cable is supplied!



CD-ROM changer
A CD-ROM player that houses several CD-ROMs,
although only one is playable at one time.  CD-ROM
changers, also called CD-ROM jukeboxes, come in as
many varieties just like audio CD players.  They
can hold from six to 200 or more discs.

   In order to have access to multiple CD-ROMs
simultaneously, it is necessary to have several CD-
ROM drives; for example, two or three SCSI drives
chained together.  In this case, each drive is
identified by its own drive letter or name and
multiple CD-ROMs can be open and active
simultaneously.



CD-ROM Extensions
The software required to use a CD-ROM drive on a PC
running DOS.  It allows the CD-ROM disc to be
addressed like a hard or floppy disk and take on
the next available drive letter.  For example, the
hard disk in the computer is C:, and if there are
no additional hard disks, then the CD-ROM becomes
the D: drive.

   The CD-ROM Extensions from Microsoft are
provided in a file named MSCDEX.EXE.  Corel has its
own CD-ROM Extensions contained in a file called
CORELCDX.COM.

   When you purchase a CD-ROM drive, a software
driver for that CD-ROM model is included.  An
installation program generally installs the driver
as well as the MSCDEX.EXE file onto your computer
automatically.



CD-ROM jukebox
See CD-ROM changer.



CD-ROM XA
(CD-ROM eXtended Architecture)  A CD-ROM
enhancement introduced in 1988 by Philips, Sony and
Microsoft that lets text and pictures be narrated
by allowing concurrent audio and video.  It
provides up to 9.5 hours of AM-quality stereo or 19
hours of monophonic audio.  CD-ROM XA drives are
required for Kodak's Photo CD discs.

   CD-ROM XA functions as a bridge between CD-ROM
and CD-I, since CD-ROM XA discs will play on a CD-I
player.  CD-ROM XA uses a standard CD-ROM player,
but requires a CD-ROM XA controller card in the
computer.  See CD-I and DVI.



CD32
A multimedia and video game technology from
Commodore that is the successor to CDTV.  CD32 is a
32-bit system that also plays Video CDs.



CDA
(Compound Document Architecture)  A compound
document format from Digital that creates hot links
between documents.



CDC
See Control Data.



CDDI
(Copper Distributed Data Interface)  A version of
FDDI that uses UTP (unshielded twisted pair) wires
rather than optical fiber.  The term is a trademark
of Crescendo Communications, Sunnyvale, CA.  ANSI's
standard for FDDI over UTP is officially TP-PMD
(Twisted Pair-Physical Media Dependent).



CDE
(1) (Common Desktop Environment)  A graphical user
interface for open systems.  It is based on Motif
with elements from HP, IBM and others.  Originally
developed by COSE, it is now governed by the X/Open
organization.

(2) (Cooperative Development Environment)  A
client/server application development system from
Oracle Corporation that includes BPR, CASE, 4GL,
3GL and end-user tools.  The core programs are
Oracle Forms for creating the user screens, Oracle
Reports for reporting, Oracle Graphics for
generating business graphics and Oracle Browser and
Oracle Data Query for queries.  Oracle Procedure
Builder provides drag and drop application
partitioning, and Oracle Transparent Gateway
provides access to non-Oracle databases.



cdev
(Control Panel DEVice)  Customizable settings in
the Macintosh Control Panel that pertain to a
particular program or device.  Cdevs for the mouse,
keyboard and startup disk, among others, come with
the Mac.  Others are provided with software
packages and utilities.



CDF
(Central Distribution Frame)  A connecting unit
(typically a hub) that acts a central distribution
point to all the nodes in a zone or domain.  See
MDF.



CDIF
(CASE Data Interchange Format)  An EIA standard for
exchanging data between CASE tools.  See PCTE.



CDIP
(Sidebrazed Ceramic DIP)  A high-qualty ceramic DIP
that typically uses gold-plated leads attached by
brazing.



CDMA
(Code Division Multiple Access)  A spread spectrum
technique that converts analog signals into digital
for transmission over the cellular network.  It
provides up to 35 times the capacity of the analog
network.  Qualcomm, Inc., San Diego, CA, has
several patents on products using its CDMA
implementation.  See FDMA, TDMA and CDPD.



CDP
(Certificate in Data Processing)  The award for the
successful completion of an examination in
hardware, software, systems analysis, programming,
management and accounting, offered by ICCP.



CDPD
(Cellular Digital Packet Data)  A type of digital
transmission using the cellular network.  Based on
IBM's CelluPlan II, it moves data at 19.2Kbps over
ever-changing unused intervals in the voice
channels.  It is being implemented by IBM, AT&T
(through McCaw Cellular) and most major telephone
companies.  See FDMA, TDMA and CDMA.



CDR
See CD-R.



CDRAM
(Cache DRAM)  A high-speed DRAM memory chip
developed by Mitsubishi that includes a small SRAM
cache.



CDROM
See CD-ROM.



CDTV
(Commodore Dynamic Total Vision)  A multimedia and
video game technology from Commodore that has been
superseded by the CD32 system.  It also plays audio
CDs.



CDV
(1) (Compressed Digital Video)  The compression of
full-motion video for high-speed, economical
transmission.

(2) (CD Video)  A small videodisc (5" diameter)
that provides five minutes of video with digital
sound plus an additional 20 minutes of audio.  Most
LaserDisc players can also play CDVs.



CEbus
(Consumer Electronics bus)  An EIA standard for a
control network.



Ceefax
A teletext service of the British Broadcasting
Corporation.



CEG
(Continous Edge Graphics)  A VGA RAMDAC chip from
Edsun Labs that adds anti-aliasing on the fly.  It
can also calculate intermediate shades, thus
providing thousands of colors on an 8-bit board
that normally generates only 256 colors.



cell
(1) An elementary unit of storage for data (bit) or
power (battery).

(2) In a spreadsheet, the intersection of a row and
column.



cell relay
A transmission technology that uses small fixed-
length packets (cells) that can be switched at high
speed.  It is easier to build a switch that
switches fixed-length packets than variable ones.
ATM uses a type of cell relay technology.



Cello
An Internet utility that lets you browse through
the Worldwide Web.



centering cone
A short plastic or metal cone used to align a 5.25"
floppy disk to the drive spindle.  It is inserted
into the diskette's center hole when the drive door
is closed.



centimeter
A unit of measurement that is 1/100th of a meter or
approximately 4/10ths of an inch (0.39 inch).



central office
The telephone switching facility that interconnects
subscribers' telephone lines to each other and to
intra and intercity trunk lines.



central processing unit
See CPU.



central processor
Same as CPU.



centralized processing
Processing performed in one or more computers in a
single location.  All terminals in the organization
are connected to the central computers.  Contrast
with distributed computing and decentralized
processing.



CENTREX
PBX services provided by a local telephone company.
Switching is done in the telephone company's
central office.  Some services do the switching at
the customer's site, but control it in the central
office.



Centronics
A standard 36-pin parallel interface for connecting
printers and other devices to a computer.  It
defines the plug, socket and signals used and
transfers data asynchronously up to 200 Kbytes/sec.

   The plug (1.5" wide, 1/8" thick) has 18 contacts
each on the top and bottom.  The socket contains
one opening with matching contacts.

   This de facto standard was developed by
Centronics Corporation, maker of the first
successful dot matrix printers.  The printer was
introduced in 1970, and the company was bought by
Genicom Corporation in 1987.  See printer cable.



CEO
(Comprehensive Electronic Office)  Office software
from Data General introduced in 1981.  It includes
word processing, e-mail, spreadsheets, business
graphics and desktop accessories.



CERDIP
(CERamic DIP)  A type of DIP that uses two ceramic
layers epoxied together.



Certificate in Computer Programming
See CCP.



certification
See CCP, NetWare certification, Microsoft Certified
Professional and CompTIA.



CGA
(Color/Graphics Adapter)  An IBM video display
standard that provided low-resolution text and
graphics.  It was the first graphics standard for
the IBM PC and has been superseded by EGA and VGA.
CGA requires a digital RGB Color Display monitor.
See PC display modes.



CGI
(Computer Graphics Interface)  A device independent
graphics language for display screens, printers and
plotters that stemmed from GKS.



CGM
(Computer Graphics Metafile)  A standard format for
interchanging graphics images.  CGM stores images
primarily in vector graphics, but also provides a
raster format.  Earlier GDM and VDM formats have
been merged into the CGM standard.



chad
A piece of paper that is punched out on a punched
card, paper tape or on the borders of continuous
forms.  A chadded form is when the holes are cut
completely through.  A chadless form is when the
chads are still attached to one edge of the hole.



chain printer
A line printer that uses character typefaces linked
together in a chain as its printing mechanism.  The
chain spins horizontally around a set of hammers.
When the desired character is in front of the
selected print position, the corresponding hammer
hits the paper into the ribbon and onto the
character in the chain.



chained list
A group of items in which each item contains the
location of the next item in sequence.



chaining
Linking items or records to form a chain.  Each
link in the chain points to the next item.



change control
See version control.



change file
A transaction file used to update a master file.



change management
See version control and configuration management.



channel
(1) A high-speed metal or optical fiber pathway
between the computer and the control units of the
peripheral devices.  Channels are used in
mainframes and high-end machines.  Each channel is
an independent unit that can transfer data
concurrently with other channels as well as the
CPU.  For example, in a 10-channel computer, 10
streams of data are being transmitted to and from
the CPU at the same time.  In contrast, the bus in
a personal computer serves as a common, shared
channel between all devices.  Each device must wait
for its turn on the bus.

(2) In communications, any pathway between two
computers or terminals.  It may refer to the
physical medium, such as coaxial cable, or to a
specific carrier frequency (subchannel) within a
larger channel or wireless medium.



channel bank
A multiplexor that merges several low-speed voice
or data lines into one high-speed (typically T1)
line and vice versa.



channel program
Instructions executed by a peripheral channel.  The
channel executes the channel program independently
of the CPU, allowing concurrent operations to take
place in the computer.



chaos
The science that deals with the underlying order of
the seemingly random nature of the universe.  See
fractals.



character
(1) A single alphabetic letter, numeric digit, or
special symbol such as a decimal point or comma.  A
character is equivalent to a byte; for example,
50,000 characters take up 50,000 bytes.

(2) The term character is also used to describe
command-driven systems.  For example, in the phrase
"it supports Mac, Windows and character
interfaces," character refers to the line-at-a-time
text entry used with dumb terminals.



character based
Same as text based.



character cell
A matrix of dots used to form a single character on
a display screen or printer.  For example, an 8x16
cell is made up of 16 rows each containing eight
dots.  Character cells are displayed and printed
contiguously; therefore the design of each letter,
digit or symbol within the cell must include
surrounding blank space.



character code
Same as data code.



character data
Alphanumeric data or text.  Contrast with numeric
data.



character device
A peripheral device that transfers data one byte at
a time at a time, such as a parallel or serial
port.  Contrast with block device.



character field
A data field that holds alphanumeric characters.
Contrast with numeric field.



character generator
(1) Circuitry that converts data characters into
dot patterns for a display screen.

(2) A device that creates text characters that are
superimposed onto video frames.



character graphics
A set of special symbols strung together like
letters of the alphabet to create elementary
graphics and forms, as in the following example:

                            
 ͸     
                          

             Character Graphics





Character Map
A Windows utility that displays all the characters
in a particular font.  See Win Typing special
characters.



character mode
Same as text mode.



character-oriented protocol
See byte-oriented protocol.



character pitch
The measurement of the number of characters per
inch.  See cpi.



character printer
A printer that prints one character at a time, such
as a daisy wheel or dot matrix printer.  See
printer.



character recognition
The ability of a machine to recognize printed text.
See OCR and MICR.



character set
(1) A group of unique symbols and codes.  For
example, the ASCII character set contains 128
characters numbered 0 to 127.  The English
character set is 26 symbols (A-Z).

(2) See symbol set.



character string
A group of alphanumeric characters.  Contrast with
numeric data.



character terminal
A display screen without graphics capability.



characteristic
In logarithms and floating point, the number that
indicates where the decimal point is placed.



charge coupled device
See CCD.



CHARGECARD
A hardware memory manager for 286 PCs from ALL
Computers Inc., Toronto, that turns extended memory
into EMS and uses unused high memory (640-1024K)
for drivers and TSRs.  The 286 chip is removed and
plugged into the CHARGECARD, which is plugged back
into the socket.



Charisma
A presentation graphics program for Windows from
Micrografx.  It includes a comprehensive media
manager that helps manage large libraries of image,
sound and video clips.



charting program
Software used to create business graphics, charts
and diagrams.  See business graphics and
diagramming program.



chat mode
A communications option that lets users type
messages back and forth to each other.  Each
keystroke is transmitted as it is pressed.



Cheapernet
See Ethernet.



check bits
A calculated number used for error checking.  The
number is derived by some formula from the binary
value of one or more bytes of data.  See parity
checking, checksum and CRC.



check box
A small box that displays an X or checkmark when
the associated option is selected.



check digit
A numeric digit used to ensure that account numbers
are correctly entered into the computer.  Using a
formula, a check digit is calculated for each new
account number, which then becomes part of the
number, often the last digit.

   When an account number is entered, the data
entry program recalculates the check digit and
compares it to the check digit entered.  If the
digits are not equal, the account number is
considered invalid.



check sum
See checksum.



checkpoint/restart
A method of recovering from a system failure.  A
checkpoint is a copy of the computer's memory that
is periodically saved on disk along with the
current register settings (last instruction
executed, etc.).  In the event of any failure, the
last checkpoint serves as a recovery point.

   When the problem has been fixed, the restart
program copies the last checkpoint into memory,
resets all the hardware registers and starts the
computer from that point.  Any transactions in
memory after the last checkpoint was taken until
the failure occurred will be lost.



checksum
A value used to ensure data is transmitted without
error.  It is created by adding the binary value of
each alphanumeric character in a block of data and
sending it with the data.  At the receiving end, a
new checksum is computed and matched against the
transmitted checksum.  A non-match indicates an
error.

   Just as a check digit tests the accuracy of a
single number, a checksum tests a block of data.
Checksums detect single bit errors and some
multiple bit errors, but are not as effective as
the CRC method.



Chicago
See Windows 95.



chicklet keyboard
A keyboard with small, square keys not suitable for
touch typing.



chief technical officer
See CTO.



child
In database management, the data that is dependent
on its parent.  See parent-child.



child program
A secondary or subprogram called for and loaded
into memory by the main program.  See parent
program.



chip
An integrated circuit.  Chips are squares or
rectangles that measure approximately from 1/16th
to 5/8th of an inch on a side.  They are about
1/30th of an inch thick, although only the top
1/1000th of an inch holds the actual circuits.
Chips contain from a few dozen to several million
electronic components (transistors, resistors,
etc.).  The terms chip, integrated circuit and
microelectronic are synonymous.


            TYPES OF CHIPS BY FUNCTION


                    Logic Chip
A single chip can perform some or all of the
functions of a processor.  A microprocessor is an
entire processor on a single chip.  Desktop and
portable computers use one microprocessor for their
CPU while larger computers may employ several types
of microprocessors as well as hundreds or thousands
of specialized logic chips.


                    Memory Chip
Random access memory (RAM) chips contain from a
couple of hundred thousand to several million
storage cells (bits).  They are the computer's
working storage and require constant power to keep
their bits charged.  Firmware chips, such as ROMs,
PROMs, EPROMs, and EEPROMs are permanent memory
chips that hold their content without power.


                Computer on a Chip
A single chip can contain the processor, RAM, ROM,
I/O control unit, and a timing clock.  It is used
in myriads of consumer and industrial products.


              Analog/Digital and DSP
A single chip can perform the conversion between
analog and digital signals.  A programmable CPU
called a DSP (digital signal processor) is also
used in many analog/digital conversions.  It
contains fast instructions sequences commonly used
in such applications.


               Special Purpose Chip
Chips used in low-cost consumer items (watches,
calculators, etc.) as well as higher-cost products
(video games, automobile control, etc.) may be
designed from scratch to obtain economical and
effective performance.  Today's ASIC chips can be
quickly created for any special purpose.


            Logic Array and Gate Array
These chips contain logic gates which have not been
tied together.  A final set of steps applies the
top metal layer onto the chip stringing the logic
gates together into the pattern required by the
customer.  This method eliminates much of the
design and fabrication time for producing a chip.


                Bit Slice Processor
Bit slice chips contain elementary electronic
circuits that serve as building blocks for the
computer architect.  They are used to custom-build
a processor for specialized purposes.



              HOW THE CHIP CAME ABOUT


                    Revolution
In late 1947, the semiconductor industry was born
at AT&T's Bell Labs with the invention of the
transistor by John Bardeen, Walter Brattain and
William Shockley.  The transistor, fabricated from
solid materials that could change their electrical
conductivity, would eventually replace all the
bulky, hot, glass vacuum tubes used as electronic
amplifiers in radio and TV and as on/off switches
in computers.  By the late 1950s, the giant first-
generation computers were giving way to smaller,
faster and more reliable transistorized machines.


                     Evolution
The original transistors were discrete components;
each one was soldered onto a circuit board to
connect to other individual transistors, resistors
and diodes.  Since hundreds of transistors were
made on one round silicon wafer and cut apart only
to be reconnected again, the idea of building them
in the required pattern to begin with was obvious.
In the late 1950s, Jack Kilby of TI and Robert
Noyce of Fairchild Semiconductor created the
integrated circuit, a set of interconnected
transistors and resistors on a single chip.

   Since then, the number of transistors that have
been put onto a single chip has increased
exponentially, from a handful in the early 1960s to
millions by the late 1980s.  Today, a million
transistors take up no more space than the first
transistor.

   A byproduct of miniaturization is speed.  The
shorter the distance a pulse travels, the faster it
gets there.  The smaller the components making up
the transistor, the faster the transistor switches.
Switch times of transistors are measured in
billionths and trillionths of a second.  In fact, a
Josephson junction transistor has been able to
switch in 50 quadrillionths of a second.


                 Logic and Memory
In first- and second-generation computers, internal
main memory was made of such materials as tubes
filled with liquid mercury, magnetic drums and
magnetic cores.  As integrated circuits began to
flourish in the 1960s, design breakthroughs allowed
memories to also be made of semiconductor
materials.  Thus, logic circuits, the "brains" of
the computer, and memory circuits, its internal
workspace, were moving along the same
miniaturization path.

   By the end of the 1970s, it was possible to put
a processor, working memory (RAM), permanent memory
(ROM), a control unit for handling input and output
and a timing clock on the same chip.

   Within 25 years, the transistor on a chip grew
into the computer on a chip.  When the awesome
UNIVAC I, which you could literally walk into, was
introduced in 1951, who would have believed that
the equivalent electronics would later be built
into a child's stuffed bear.


                  More Evolution
Just as integrated circuits eliminated cutting
apart the transistors only to be reconnected again,
eventually wafer scale integration will eliminate
cutting apart whole chips only to be reconnected
again.  In time, instead of adding more circuits
across the surface, the circuits will be built in
overlapping layers.  Within the next 10 to 15
years, it is conceivable that the electronics in
today's multi-million-dollar supercomputer can be
built within a cube one inch square!



               THE MAKING OF A CHIP

Computer circuits are pathways carrying electrical
pulses from one point to another.  The pulses flow
through on/off switches, called transistors, which
open or close when electrically activated.  The
current flowing through one switch effects the
opening or closing of another and so on.  Small
clusters of transistors form logic gates, which are
the building blocks behind all this magic, and a
specific combination of logic gates make up a
circuit.


              From Logic to Plumbing
Today, the majority of circuits being used have
already been designed and reside in circuit
libraries in a computer.  A computer designer
merely has to pick and choose ready-made modules
(standard cells) from a menu.  But they all had to
be invented at one point, and new circuits still
have to go through an elaborate process to convert
logical patterns on paper into an equivalent maze
of plumbing on the chip.

   Computers help make computers.  The logical
design is entered into the computer and converted
into transistors, diodes and resistors.  Then the
combination of electronic components is turned into
a plumber's nightmare that is displayed for human
inspection.  After corrections have been made, the
completed circuits are transferred to specialized
machinery that create lithographic plates made out
of glass, called photomasks.  The photomasks are
the actual size of the wafer and contain as many
copies of the design of the chip as will fit on the
wafer.  The transistors are built by creating
subterranean layers in the silicon, and a different
photomask is created to isolate each layer to be
worked on.  With each layer, the same part of every
transistor on every chip is constructed at the same
time.


               Chips Are Just Rocks
The base material of a chip is usually silicon,
although materials such as sapphire and gallium
arsenide are also used.  Silicon is found in quartz
rocks and is purified in a molten state.  It is
then chemically combined (doped) with other
materials to alter its electrical properties.  The
result is a silicon crystal ingot from three to
five inches in diameter that is either positively
(p-type) or negatively charged (n-type).  Wafers,
about 1/30th of an inch thick, are cut from this
"crystal salami."


                Building the Layers
Circuit building starts out by adhering a layer of
silicon dioxide insulation on the wafer's surface.
The insulation is coated with film and exposed to
light through the first photomask, hardening the
film and insulation below it.  The unhardened areas
are etched away exposing the silicon base below.
By shooting a gas under heat and pressure into the
exposed silicon (diffusion), a sublayer with
different electrical properties is created beneath
the surface.

   Through multiple stages of masking, etching, and
diffusion, the sublayers on the chip are created.
The final stage lays the top metal layer (usually
aluminum), which interconnects the transistors to
each other and to the outside world.

   Each chip is tested on the wafer, and bad chips
are marked for elimination.  The chips are sliced
out of the wafer, and the good ones are placed into
packages (DIPs, SIMMs, SIPs, etc.).  The chip is
connected to the package with tiny wires, then
sealed and tested as a complete unit.

   Chip making is extremely precise.  Operations
are performed in a "clean room," since air
particles can mix with the microscopic mixtures and
easily render a chip worthless.  Depending on the
design complexity, more chips can fail than
succeed.


                    The Future
In order to miniaturize elements of a transistor
even further, the photomasks have to be made with
x-rays or other beams which are narrower than
light.  Eventually, circuit patterns will be etched
directly onto the chip, eliminating the entire
photographic masking process.

   During the 1990s, multi-million-transistor chips
will be commonplace.  However, when wafer scale
integration becomes a reality, one wafer could hold
a gigabyte of memory and a processor five times as
large as the Pentium along with a quantum reduction
in cost.  If superconductor transistors take hold,
there will be a gigantic leap in performance.
Should both technologies arise at the same time,
hold on to your hats!



chip card
See smart card and memory card.



chip carrier
(1) The package that a chip is mounted in.

(2) A chip package with connectors on all sides.
See leaded chip carrier and leadless chip carrier.



chipset
A group of chips designed to work as a unit to
perform a function.  For example, a modem chipset
contains all the primary circuits for transmitting
and receiving.  A PC chipset contains the system,
memory and bus controllers.  Combine the chipset on
the motherboard with the clock, CPU and memory, and
you have a complete computer.  Today, an entire PC
chipset can be made to fit on a single chip.



Chkdsk
See DOS Chkdsk.



CHMOS
(High-density CMOS)  A chip with a high density of
CMOS transistors.



Chooser
A Macintosh desk accessory that allows the user to
select a printer, file server or network device,
such as a network modem.



chroma
Color.



chroma key
See color key.



chromatic dispersion
The spreading of light rays within an optical
fiber, which causes decreased bandwidth.



CICS
(Customer Information Control System)  A TP monitor
from IBM that was originally developed to provide
transaction processing for IBM mainframes.  It
controls the interaction between applications and
users and lets programmers develop screen displays
without detailed knowledge of the terminals used.
It provides terminal routing, password security,
transaction logging for error recovery and activity
journals for performance analysis.

   CICS has also been made available on non-
mainframe platforms including the RS/6000, AS/400
and OS/2-based PCs.

   CICS commands are written along with and into
the source code of the applications, typically
COBOL, although assembly language, PL/I and RPG are
also used.  CICS implements SNA layers 4, 5 and 6.



CICS programmer
A programmer versed in CICS commands as well as in
the programming language used to develop the
application.



CID
(Configuration, Installation and Distribution)  IBM
software for controlling software distribution
throughout a network from a central source.



cider
See CIDR.



CIDR
(Classless Inter-Domain Routing)  A method for
reducing the burden on routing tables in the
Internet.  It provides a subnetwork for Internet
service providers by combining a number of Class C
addresses into one.  See IP address.



CIF
(Common Intermediate Format)  A video format that
transmits 36.45 Mbits/sec at 30 frames/sec.  See
QCIF and H.261.



CIM
(1) (Computer-Integrated Manufacturing)
Integrating office/accounting functions with
automated factory systems.  Point of sale, billing,
machine tool scheduling and supply ordering are
part of CIM.

(2) (CompuServe Information Manager)  See
CompuServe.



cine-oriented
A film-image orientation like that of movie film,
which runs parallel to the outer edge of the
medium.  Contrast with comic-strip oriented.



Cinepak
A video compression/decompression algorithm from
SuperMac Technologies, Sunnyvale, CA, that is used
to compress movie files.



CIO
(Chief Information Officer)  The executive officer
in charge of all information processing in an
organization.



ciphertext
Data that has been coded (enciphered, encrypted,
encoded) for security purposes.



CIR
(Committed Information Rate)  In a frame relay
network, the minimum speed maintained between
nodes.



circuit
(1) A set of electronic components that perform a
particular function in an electronic system.

(2) Same as communications channel.



circuit analyzer
(1) A device that tests the validity of an
electronic circuit.

(2) In communications, same as data line monitor.



circuit board
Same as printed circuit board.



circuit breaker
A protective device that opens a circuit upon
sensing a current overload.  Unlike a fuse, it can
be reset.



circuit card
Same as printed circuit board.



circuit cellular
The transmission of data over the cellular network
using a voice channel and modem similar to using
land-based modems.  Contrast with packet cellular.
See wireless.



circuit switching
The temporary connection of two or more
communications channels.  Users have full use of
the circuit until the connection is terminated.
Contrast with message switching, which stores
messages and forwards them later, and contrast with
packet switching, which breaks up a message into
packets and routes each packet through the most
expedient path at that moment.

   Circuit switching is used by the telephone
company for its voice networks in order to
guarantee steady, consistent service for two people
engaged in a telephone conversation.



CIS
(1) (CompuServe Information Service)  See
CompuServe.

(2) (Card Information Structure)  A data structure
on a PCMCIA card that contains information about
the card's contents.  It allows the card to
describe its configuration requirements to its host
computer.



CIS B
(CompuServe Information Service B)  A proprietary
communications protocol from CompuServe that is
used for transferring files.  See B protocol.



CISC
(Complex Instruction Set Computer)  Pronounced
"sisk."  The traditional architecture of a computer
which uses microcode to execute very comprehensive
instructions.  Instructions may be variable in
length and use all addressing modes, requiring
complex circuitry to decode them.  Contrast with
RISC.



Cisco
(Cisco Systems, Inc., San Jose, CA)  Founded in
1984, Cisco is the major manufacturer of routers.



CL/1
(Connectivity Language/1)  A database language from
Apple that lets a Macintosh access an SQL-based
database in another computer.  CL/1 applications
communicate with the CL/1 client program in the
Mac, and the client program communicates with the
CL/1 server program in the host computer.



cladding
The plastic or glass sheath that is fused to and
surrounds the core of an optical fiber.  It keeps
the light waves inside the core and adds strength
to it.  The cladding is covered with a protective
outer jacket.



clamping ring
The part of a 5.25" floppy disk drive that presses
the disk onto the spindle.  It is usually part of
the centering cone.



Clarion
A family of application development systems for DOS
and Windows from TopSpeed Corporation, Pompano
Beach, FL.  It provides a comprehensive set of
tools for development, including a screen builder,
4GL and application generator.  It includes a
compiler that is known for generating fast
executables.  It also includes a data dictionary
and drivers for popular databases.  TopSpeed
Corporation was formerly Clarion Software
Corporation.



Claris
(Claris Corporation, Santa Clara, CA)  A software
subsidiary of Apple that was separated from the
corporation (although mostly owned by it) in 1988
and then bought back in 1990.



Claris CAD
A full-featured 2-D CAD program for the Macintosh
from Claris Corporation that is noted for its ease
of use.  It provides an easy-to-learn path into
CAD, while offering most features found in CAD
programs.



class
In object-oriented programming, a user-defined data
type that defines a collection of objects that
share the same characteristics.  A class member
(object) is an "instance" of the class.  Concrete
classes are designed to be "instantiated."
Abstract classes are designed to pass on
characteristics through inheritance.



Class A, B
See FCC Class.



class library
An object-oriented programming classes suplied by
third parties; for example, a GUI library.



Classic
See Macintosh.



CLCC
(Ceramic Leaded Chip Carrier)  See leaded chip
carrier.



clean boot
Booting the computer without loading anything but
the main part of the operating system.  See DOS
startup options.



clean room
A room in which the air is highly filtered in order
to keep out impurities.



clear memory
To reset all RAM and hardware registers to a zero
or blank condition.  Rebooting the computer may or
may not clear memory, but turning the computer off
and on again guarantees that memory is cleared.



clear to send
See CTS.



ClearCase
A software configuration management (SCM) system
for client/server environments from Atria Software,
Inc., Natick, MA.  It supports all the major UNIX
platforms as well as Windows NT.



CLI
(Call Level Interface)  A database programming
interface from the SQL Access Group, an SQL
membership organization.  SAG's CLI is an attempt
to standardize the SQL language for database
access.  Microsoft's ODBC conforms to the CLI, but
adds its own extensions.  Under CLI, SQL statements
are passed directly to the server without being
recompiled.



click
To select an object by pressing the mouse button
when the cursor is pointing to the required menu
option or icon.



client
(1) A workstation or personal computer in a
client/server environment.  See client/server and
fat client.

(2) One end of the spectrum in a request/supply
relationship between programs.  See X Window and
OLE.



client application
An application running in a workstation or personal
computer on a network.  See also OLE.



client-client-server
An Apple architecture that allows users with remote
devices, such as laptops and PDAs, to have easy
access to their desktop machines (clients) as well
as to the servers.



client/server
An architecture in which the client (personal
computer or workstation) is the requesting machine
and the server is the supplying machine.  Servers
can be high-speed microcomputers, minicomputers or
even mainframes.  The client provides the user
interface and may perform some or all of the
application processing.  A database server is a
computer that maintains the databases and processes
requests from the client to extract data from or
update the database.  An application server is a
computer that provides additional business
processing for the clients.

   Client/server architecture is the equivalent of
a mainframe system on a network of smaller
computers.  The network operating system (NOS)
together with the DBMS (database management system)
and TP monitor (transaction monitor) are
responsible for the integrity and security of the
system and must provide the same degree of
robustness as mainframes for mission critical
applications.

   Client/server architecture means that the server
is used for more than just a remote disk drive to
the client.  Simply downloading files from the
server to the client or sharing a database on the
server is not client/server architecture.
Client/server means that the processing is split
between the client and the server.  Take a look at
the following examples.



          NON-CLIENT/SERVER ARCHITECTURE
       (Server acts as a remote disk drive.)

The following diagram is a non-client/server
example.  The client uses the server as a remote
disk drive.  Thus, if a user wants to search for
data that meets certain criteria, all the records
in the database must be transmitted to the client
machine as the client software is doing the
searching.  If there are 10,000 1,000-byte records
in the database, 10 megabytes of data must be
passed over the network to the client for comparing
until the appropriate record is found.


    Query and get all records to compare.
    
  CLIENT                      SERVER
         <---10,000,000 bytes       
        ܳ      
                        
                                DATABASE
                             10,000 records



        TWO-TIER CLIENT/SERVER ARCHITECTURE
           (Processing in two machines.)

The following example is the way the query above
would be processed using client/server
architecture.  The request would generate an SQL
query that is transmitted from the client to the
DBMS in the server.  The DBMS would search the
database, passing back only matching records.  If
only three records met the criteria, 3,000 bytes
would be transferred over the net.  If 10 records
matched, 10,000 bytes would be sent.


   Query and get matching records.
   
  CLIENT                      SERVERĿ
          <--- 3,000 bytes                    
        ܳ      DBMS      
                        
                                     DATABASE
                                  10,000 records


The examples above demonstrate the dramatic
difference in network traffic depending on the
location of the database processing.  In a heavily-
used LAN, large file transfers degrade network
performance.

In summary, many personal computer database
programs placed in a network server function only
as a remote disk drive.  The client does all the
processing.  It accepts the request, searches the
database by retrieving all the records in the
database for comparison, and displays the results.
On the other hand, client/server architecture does
the processing in two machines.  The client accepts
the request, the server searches the database, and
the client displays the results.



       THREE-TIER CLIENT/SERVER ARCHITECTURE
      (Processing in three or more machines.)

The client/server example above is known as two-
tier client/server architecture, because the
processing is done in two machines.  Typically, the
server is doing database tasks, and the application
is doing all the remaining business processing.

   However, there are many business applications in
which various components of the operation lend
themselves to central processing in a server and
not in each client machine.  Such programs may be
too demanding on the resources of the user's PC, or
passing large amounts of data back and forth to the
client machines may bog down the network.  They may
also represent proprietary business logic that
should not be replicated all over the enterprise.

   Partitioning the application into three or more
machines is called three-tier client/server.  The
application partitioning is either done by
traditional programming methods or via newer
enterprise-wide client/server development systems.
The result is that the client machine provides the
user interface, the application server or servers
provide shared processing for the clients, and the
database server or servers process the queries and
updates to the database.


                     APPLICATION         DATABASE
 CLIENTĿ        SERVERĿ         SERVERĿ
                                             
 User             Business          Query,   
 interfaceܳLogic    ܳupdate   
                                    database 
                  


               The Development Tools
For a list of popular client/server development
tools, see client/server development system.





client/server architecture
A network and application design that divides
processing between clients and servers.  See
client/server.



client/server development system
An application development system used to create
applications for a client/server environment.  A
comprehensive system generally includes a GUI
builder for creating one or all of the major GUIs:
Windows, Mac and Motif, a fourth-generation
language for creating the business logic, an
interpreter and/or compiler and debugging tools.
It provides support for many of the major database
management systems (Oracle, Sybase, Informix,
etc.), and it may include its own DBMS.

   For enterprise-wide client/server development, a
system may allow for application partitioning,
which separates parts of the application onto
different machines.  Such systems support the major
server environments (UNIX, NetWare, etc.) in order
to accomodate the dispersion of business logic onto
multiple computers.  It may also include software
configuration management capabilities that provide
version control and bug tracking.

   Almost any language can be used to develop the
client front ends in a client/server application.
For example, Visual Basic is very popular for such
purposes.  However, a client/server system implies
that client-to-server connections and application
partitioning are written at a higher level than a
3GL programming language.  It implies that there is
little or no "tweaking" to make things happen.  See
client/server and application partitioning.

   Following is a list of client/server development
tools in alphabetical order.  PowerBuilder,
SQLWindows and Oracle's CDE are widely used.
DYNASTY and Forte are a new breed of enterprise-
wide tools, and dBASE and Paradox for Windows have
moved into client/server with the addition of the
Borland Database Engine, which is included.

    Application Development Workbench
    Axiant
    C/S ELEMENTS
    dBASE for Windows/Borland Database Engine
    DYNASTY
    Enfin/Object Studio
    ESL for Windows
    ESL Workbench
    Forte
    JAM
    ObjectView
    OMNIS
    Oracle CDE (Oracle Forms, Oracle Reports, etc.)
    Paradox for Windows/Borland Database Engine
    PowerBuilder
    Progress
    SQLWindows
    UNIFACE
    Unify VISION
    Visual Basic
    Windows 4GL/CA-OpenRoad





client/server environment
A networking environment that is made up of clients
and servers running applications designed for
client/server architecture.  See client/server.



client/server network
(1) A communications network that uses dedicated
servers.  In this context, the term is used to
contrast it with a peer-to-peer network, which
allows any client to also be a server.

(2) A network that is processing applications
designed for client/server architecture.  See
client/server.



client/server protocol
A communications protocol that provides a structure
for requests between client and server in a
network.  It refers to OSI layer 7.



clip art
A set of canned images used to illustrate word
processing and desktop publishing documents.



clipboard
Reserved memory used to hold data that has been
copied from one application in order to be inserted
into another.



Clipper
(1) See CA-Clipper.

(2) A family of 32-bit RISC microprocessors from
Intergraph Corporation, Huntsville, AL.

(3) An encryption chip endorsed by the U.S.
government for general use that would let
authorities unscramble the data if needed.



clipping
Cutting off the outer edges or boundaries of a
word, signal or image.  See scissoring.



clipping level
A disk's ability to maintain its magnetic
properties and hold its content.  A high-quality
level range is 65-70%; low quality is below 55%.



clock
An internal timing device.  Following are the
different varieties of clocks:

                     CPU Clock
Uses a quartz crystal to generate a uniform
electrical frequency from which digital pulses are
created and used.  See clock speed.


                  Realtime Clock
A time-of-day clock that keeps track of hours,
minutes and seconds and makes this data available
to the programs.


                 Timesharing Clock
A timer set to interrupt the CPU at regular
intervals in order to provide equal time to all the
users of the computer.


               Communications Clock
In a synchronous communications device, a clock
maintains the uniform transmission of data between
the sending and receiving terminals and computers.



clock/calendar
An internal time clock and month/year calendar that
is kept active with a battery.  Its output allows
software to remind users of appointments, to
determine the age of a transaction and to activate
tasks at specified times.



clock doubling
Doubling the internal processing speed of a CPU
while maintaining the original clock speed for I/O
(transfers in/out of the chip).  Intel popularized
the technique with its Speed Doubler chips.  See
486 and clock tripling.



clock pulse
A signal used to synchronize the operations of an
electronic system.  Clock pulses are continuous,
precisely spaced changes in voltage.  See clock
speed.



clock speed
The internal heartbeat of a computer.   The clock
circuit uses fixed vibrations generated from a
quartz crystal to deliver a steady stream of pulses
to the CPU.

   A faster clock will speed up internal processing
provided the computer's circuits can handle the
increased speed.  For example, the same processor
running at 20MHz is twice as fast internally as one
running at 10MHz.



clock tripling
Tripling the internal processing speed of a CPU
while maintaining the original clock speed for I/O
(transfers in/out of the chip).  See DX4.



clone
A device that works like the original, but does not
necessarily look like it.  It implies 100%
functional compatibility.



closed
With regard to a switch, closed is "on."  Open is
"off."


closed architecture
A system whose technical specifications are not
made public.  Contrast with open architecture.



closed shop
An environment in which only data processing staff
is allowed access to the computer.  Contrast with
open shop.



closed system
A system in which specficiations are kept
proprietary to prevent third-party hardware or
software from being used.  Contrast with open
system.



cloud
See network cloud.



cluster
Some number of disk sectors (typically two to 16)
treated as a unit.  The entire disk is divided into
clusters, each one a minimum unit of storage.
Thus, a 30-byte file may use up 2,048 bytes on disk
if the disk cluster is four 512-byte sectors.  See
lost cluster.



cluster controller
A control unit that manages several peripheral
devices, such as terminals or disk drives.

                         terminal
                          terminal
   Ŀ   terminal
   Computer    Cluster  terminal
   or FEP  ĴControllerterminal
      





CLUT
(Color Look Up Table)  A hardware or software table
that contains color mixing information (intensity
of red, green and blue) for each color in a palette
or series of palettes.



CLV
(Constant Linear Velocity)  A disk technique that
spins a disk at different speeds.  By varying the
speed depending on which track is being accessed,
the physical density of bits in each track can be
the same, thus allowing the outer tracks to hold
more data than the inner tracks.

   CLV mechanisms are used in CD-ROM players in
order to store larger amounts of data.  Contrast
with CAV.  See ZBR.



CM
See configuration management.



CM/2
(Communications Manager/2)  A communications
program for OS/2 from IBM that provides cross
platform connectivity.  It provides terminal
emulation to IBM mainframes, AS/400s and VAXes and
supports APPN and APPC protocols.



CMC
(Common Messaging Calls)  A programming interface
specified by the XAPIA as the standard messaging
API for X.400 and other messaging systems.  CMC is
intended to provide a common API for applications
that want to become mail enabled.



CMI
(Computer-Managed Instruction)  Using computers to
organize and manage an instructional program for
students.  It helps create test materials, tracks
the results and monitors student progress.



CMIP
(Common Management Information Protocol)
Pronounced "C-mip."  A network monitoring and
control standard from ISO.  CMOT (CMIP over TCP) is
a version that runs on TCP/IP networks, and CMOL
(CMIP over LLC) runs on IEEE 802 LANs (Ethernet,
Token Ring, etc.).



CMIS
(Common Management Information Services)
Pronounced "C-miss."  An OSI standard that defines
the functions for network monitoring and control.



CMM
See SEI.



CMOL
See CMIP.



CMOS
(Complementary MOS)  Pronounced "C moss."  A type
of integrated circuit widely used for processors
and memories.  It uses PMOS and NMOS transistors in
a complementary fashion that results in less power
to operate.  The term is used loosely to refer to
the CMOS RAM in a PC.



CMOS RAM
(1) A small, battery-backed memory bank in a
personal computer that is used to hold time, date
and system information such as drive types.  In a
PC, if disk drives are added, removed or changed,
the parameters in the CMOS memory must be updated
in order for the operating system to recognize the
new devices.

   To edit the data in the CMOS RAM, you have to
gain access to a built-in setup program, which is
done either immediately at boot time by pressing a
key such as DEL or F1, or by pressing some key
combination, such as Ctrl-Alt-Esc.  If there is no
on-screen message that tells you what key to press
when you reboot the computer, refer to your system
manual (RTFM!).  See hard disk configuration.

(2) Memory made of CMOS chips.  Due to their low
power requirement, they are increasingly being used
for main memory in portable computers.



CMOT
See CMIP.



CMS
(1) (Conversational Monitor System)  Software that
provides interactive communications for IBM's VM
operating system.  It allows a user or programmer
to launch an application from a terminal and
interactively work with it.  The CMS counterpart in
MVS is called TSO.  Contrast with RSCS, which
provides batch communications for VM.

(2) (Call Management System)  An AT&T call
accounting package for its PBXs.



CMYK
(Cyan Magenta Yellow blacK)  A color model used for
printing.  In theory, cyan, magenta and yellow
(CMY) can print all colors, but inks are not pure
and black comes out muddy.  Black ink is required
for quality printing.  See colors and RGB.



CNA
See NetWare certification.



CNC
(Computerized Numerical Control)  See numerical
control.



CNE
See NetWare certification.



CNI
See NetWare certification.



CO
(Central Office)  A local telephone company
switching station that covers a geographic area
such as a town or part of a city.



co-resident
A program or module that resides in memory along
with other programs.



coax
Same as coaxial cable.



coax adapter
Same as 3270 emulator.  The board is sometimes
called a coax adapter because of its coaxial cable
connection to the IBM cluster controller.



coaxial cable
A high-capacity cable used in communications and
video, commonly called co-ax.  It contains an
insulated solid or stranded wire surrounded by a
solid or braided metallic shield, wrapped in a
plastic cover.  Fire-safe teflon coating is
optional.

   Although similar in appearance, there are
several types of coaxial cable, each designed with
a different width and impedance for a particular
purpose (TV, baseband, broadband).  Coax provides a
higher bandwidth than twisted wire pair.  See cable
categories.



COBOL
(COmmon Business Oriented Language)  A high-level
programming language that has been the primary
business application language on mainframes and
minis.  It is a compiled language and was one of
the first high-level languages developed.  Formally
adopted in 1960, it stemmed from a language called
Flowmatic in the mid 1950s.

   COBOL is a very wordy language.  Although
mathematical expressions can also be written like
other programming languages (see example below),
its verbose mode is very readable for a novice.
For example, multiply hourly-rate by hours-worked
giving gross-pay is self-explanatory.  COBOL is
structured into the following divisions:

Division name    Contains
IDENTIFICATION   Program identification.
ENVIRONMENT      Types of computers used.
DATA             Buffers, constants and work areas.
PROCEDURE        The processing (program logic).

The following COBOL example converts a Fahrenheit
number to Celsius.  To keep the example simple, it
performs the operation on the operator's terminal
rather than a user terminal.

  IDENTIFICATION DIVISION.
  PROGRAM-ID.  EXAMPLE.

  ENVIRONMENT DIVISION.
  CONFIGURATION SECTION.
  SOURCE-COMPUTER.   IBM-370.
  OBJECT-COMPUTER.   IBM-370.

  DATA DIVISION.
  WORKING-STORAGE SECTION.
  77 FAHR  PICTURE 999.
  77 CENT  PICTURE 999.

  PROCEDURE DIVISION.
  DISPLAY 'Enter Fahrenheit ' UPON CONSOLE.
  ACCEPT FAHR FROM CONSOLE.
  COMPUTE CENT = (FAHR- 32) * 5 / 9.
  DISPLAY 'Celsius is ' CENT UPON CONSOLE.
  GOBACK.


                    IBM COBOLs
In 1994, IBM will drop support of OS/VS COBOL,
which conforms to ANSI 68 and ANSI 74 standards and
limits a program's address space to 16 bits.  IBM's
VS COBOL II (1984) and COBOL/370 (1991) conform to
ANSI 85 standards and provide 31-bit addressing,
which allows programs to run "above the line."

   COBOL/370 is more compliant with AD/Cycle, has
more string, math and date functions, including
four-digit years, allows development through a PC
window and provides enhanced runtime facilities.



COBOL Workbench
See Micro Focus.



CODASYL
(COnference on DAta SYstems Languages)  An
organization devoted to the development of computer
languages.  Founded in 1959, it is made up of
individuals and institutions that contribute their
own time and effort.  COBOL is a product of
CODASYL.  For information, contact Jan Prokop, 29
Hartwell Avenue, Lexington, MA 02173, 617/863-5100.



code
(1) A set of machine symbols that represents data
or instructions.  See data code and machine
language.

(2) Any representation of one set of data for
another.  For example, a parts code is an
abbreviated name of a product, product type or
category.  A discount code is a percentage.

(3) To write a program.  See source code and line
of code.

(4) To encode for security purposes.  See
encryption.



code generator
See application generator and macro recorder.



code page
In DOS 3.3 and higher, a table that sets up the
keyboard and display characters for various foreign
languages.



codec
(1) (COder-DECoder)  An electronic circuit that
converts audio or video into digital code (and vice
versa) using techniques such as pulse code
modulation and delta modulation.  A codec is an A/D
and D/A converter.

(2) (COmpression/DECompression)  A hardware circuit
or software routine (software codec) used to
compress and decompress digitized audio, video or
images.  A single codec may include the functions
of A/D and D/A conversion as well as compression
and decompression.  See video codec.



coder
(1) A junior, or trainee, programmer who writes
simple programs or writes the code for a larger
program that has been designed by someone else.

(2) Person who assigns special codes to data.



CodeView
A Microsoft debugger for programs written with
Microsoft C and CodeView-compatible compilers.
Like other modern debuggers, it links source and
object program letting the programmer step through
the source code as the program is executed.



COFF
(Common Object File Format)  A UNIX System V
machine language format.



Cognos
(Cognos Inc., Ottawa, Canada)  A software company
that specializes in application development and 4GL
tools.  Founded in 1969 as a consulting firm, its
PowerHouse 4GL was introduced in the late 1970s for
midrange systems.  Products include the PowerPlay
EIS/DSS system, Impromptu report and query language
and Axiant client/server development system.



COGO
(COordinate GeOmetry)  A programming language used
for solving civil engineering problems.



Coherent
A version of UNIX for 386s and up from Mark
Williams Co., Northbrook, IL, that supports a
variety of office applications off the shelf.  It
includes a C compiler, over 200 utilities and the
Bourne and Korn shells.  It uses minimal system
resources.



COLD
(Computer Output to LaserDisc)  Archiving large
volumes of transactions on optical media.  Instead
of printing large paper reports or producing
microfilm or microfiche, data is stored on optical
disks.  The advantage of COLD over COM (Computer
Output Microfilm) for high-volume, archival storage
is that optical disks can be directly accessed just
like a hard disk.



cold boot
Starting the computer by turning power on.  Turning
power off and then back on again clears memory and
many internal settings.  Some program failures will
lock up the computer and require a cold boot to use
the computer again.  In other cases, only a warm
boot is required.  See boot, warm boot and clean
boot.



cold start
Same as cold boot.



collapsed backbone
A network configuration in which a high-speed bus
within a single equipment cabinet is used as the
backbone.



collating sequence
The sequence, or order, of the character set built
into a computer.  See ASCII chart and EBCDIC chart.



collator
(1) A punched card machine that merges two decks of
cards into one or more stacks.

(2) A utility program that merges records from two
or more files into one file.



collector
The output side of a bipolar transistor.  Same as
drain in a MOS transistor.



collision detection
See CSMA/CD.



color bits
The number of bits associated with each pixel that
represent its color.  See bit depth.



color calibration
The matching of colors to a base color, such as a
Pantone color, or from one device to another; for
example, screen and printer output.



color cycling
In computer graphics, a technique that simulates
animation by continuously changing colors rather
than moving the objects.  Also called color lookup
table animation.



color depth
Same as bit depth.



color graphics
The ability to display graphic images in colors.



color key
A technique for superimposing a video image onto
another.  For example, to float a car on the ocean,
the car image is placed onto a blue background.
The car and ocean images are scanned together.  The
ocean is made to appear in the resulting image
wherever background (blue) exists in the car image.
The ocean is cancelled wherever the car appears (no
background).



color map
See CLUT.



color model
The method used to represent color for display and
printing.  See RGB, CMYK, HSV, HLS and YIQ.



color monitor
See monitor.



color printer
A printer that prints in color using dot matrix,
electrophotographic, Cycolor, electrostatic, ink
jet or thermal-transfer techniques.  See printer.



color separation
Separating a picture by colors in order to make
negatives and plates for color printing.  Full
color requires four separations: cyan, magenta,
yellow and black (CMYK).



colors
The perception of the different wavelengths of
light.  It is possible to create almost all visible
colors using two systems of primary colors.
Transmitted colors use red, green and blue (RGB),
and reflected colors use cyan (light blue), magenta
(purplish-red), yellow and black (CMYK).  Color
displays use RGB (colors are added to create white)
and color printing uses CMYK (colors are subtracted
to create white).



column
A vertical set of data or components.  Contrast
with row.



column move
Relocating a rectangular block of characters within
a text document or a column in a spreadsheet.



COM
(1) (Computer Output Microfilm)  Creating microfilm
or microfiche from computer output.  A COM machine
can be online or stand-alone (transfer via
tape/disk).  It receives print-image output from
the computer and creates a film image of each page.
Additional graphics (lines, logos, etc.) may be
added.

(2) (Common Object Model)  An object, or ORB,
standard from Digital and Microsoft announced in
late 1993.  It is based on Microsoft's OLE2 (second
generation of OLE), whose underlying structure is
called Component Object Model.  COM is not CORBA
compliant; however, interoperability between COM
and CORBA is expected.



COM 1
See COM1.



COM 2
See COM2.



COM file
(1) (COMmand file)  An executable DOS or OS/2
program that takes up less than 64K and fits within
one segment.  It is an exact replica of how it
looks in memory.  See EXE file.

(2) A VMS file containing commands to be excecuted.



COM port
A serial communications port on a PC.  See COM1 and
serial port.



COM1
In a PC, the logical name assigned to the first
serial port.  Two serial ports, or COM ports, are
provided on a PC to connect a mouse and modem.
Typically the mouse is on COM1, and the modem on
COM2, but this is not mandatory.  Any serial device
can be connected to either serial port.

   The COM1 and COM2 names are used to inform the
operating system of the physical connections that
have been made.  The term originated before the
days of the mouse, when the serial port was
primarily used for modem COMmunications.

   DOS versions up to 3.2 support COM1 and COM2.
Version 3.3 supports up to COM4, and OS/2 supports
eight COM ports.  Contrast with LPT1.



COM2
In a PC, the logical name assigned to the second
serial port.  See COM1.



COMDEX
(COMputer Dealers EXposition)  A trade show
originally intended for PC manufacturers,
developers, dealers and distributors.  However,
large numbers of end users attend.  Sponsored by
The Interface Group, COMDEX/Fall in Las Vegas is
the largest U.S. computer show.  It is housed in
both the Las Vegas and Sands convention centers as
well as Bally's Casino Resort and the Hilton,
Riviera and Tropicana hotels.  Shuttle buses escort
attendees between sites.  Address: The Interface
Group, 300 First Avenue, Needham, MA 02194,
617/449-6600.

   The first COMDEX/Fall in 1979 had 157 exhibitors
and drew 4,000 attendees.  In 1993, over 2,000
exhibitors drew 150,000 attendees.

   COMDEX/Spring has been held in Chicago and now
Atlanta at the World Congress Center.  It began in
1981 with 237 exhibitors and more than 11,000
attendees.  In 1993, 1,000 exhibitors drew more
than 75,000.

   COMDEX/Sucesu-SP '93 in Sao Paulo, Brazil, drew
135,000 attendees.


              Upcoming COMDEX Events

 COMDEX/Spring, Atlanta
  Apr. 24-27, 1995

 COMDEX/Fall, Las Vegas
  Nov. 13-17, 1995

 COMDEX/Canada, Toronto
  July 12-14, 1995

 COMDEX/ComExpo Mexico, Mexico City
  Mar. 7-10, 1995

 COMDEX/Sucesu-SP South America, Rio de Janeiro
  Apr. 4-7, 1995

 COMDEX/Sucesu-SP South America, Sao Paulo, Brazil
  Aug. 15-18, 1995

 COMDEX/PacRim, Vancouver, British Columbia
  Jan. 17-19, 1995

 COMDEX/Asia, Singapore Informatics, Singapore
  Oct. 26-29, 1995





Comensa
A datacenter control system from MAXM Systems
Corporation, Vienna, VA, used to monitor a variety
of minicomputers and mainframes.  It can set off
audio alarms if problems occur.



comic-strip oriented
A film-image orientation like a comic strip, which
runs perpendicular to the outer edge of the film.
Contrast with cine-oriented.



comm port
May refer to any serial communications port or
specifically to the serial ports on a PC.  See
COM1.



comm program
See communications program.



comma delimited
A record layout that separates data fields with a
comma and usually surrounds character data with
quotes, for example:

"Pat Smith","5 Main St.","New Hope","PA","18950"
"K. Jones","34 E. 88 Ave.","Syosset","NY","10024"




command
Instruction for the computer.  See command-driven,
menu-driven and function.



command-driven
A program that accepts commands as typed-in
phrases.  It is usually harder to learn, but may
offer more flexibility than a menu-driven program.
Once learned, command-driven programs may be faster
to use, because the user can state a request
succinctly.  Contrast with menu-driven.



command interpreter
Same as command processor.



Command key
On Apple keyboards, a key with the outline of an
Apple, a propeller, or both.  It is pressed along
with another key to command the computer.



command language
A special-purpose language that accepts a limited
number of commands, such as a query language, job
control language (JCL) or command processor. 
Contrast with programming language, which is a
general purpose language.



command line
In a command-driven system, the area on screen that
accepts typed-in commands.



command mode
An operating mode that causes the computer or modem
to accept commands for execution.



command processor
A system program that accepts a limited number of
user commands and converts them into the machine
commands required by the operating system or some
other control program or application.  COMMAND.COM
is the command processor that accompanies DOS.  See
4DOS.



command queuing
The ability to store multiple commands and execute
them one at a time.



command set
Same as instruction set.



command shell
Same as command processor.



COMMAND.COM
The command processor for DOS and OS/2 in Real
Mode.  See DOS COMMAND.COM.



comment
A descriptive statement in a source language
program that is used for documentation.



comment out
To disable lines of code in a program by
surrounding them with comment-start and comment-
stop characters.



commercial software
Software that is designed and developed for sale to
the general public.



Commodore
(Commodore Business Machines, Inc., West Chester,
PA)  In 1977, Commodore introduced the PET computer
and launched the personal computer industry along
with Apple and Radio Shack.  In 1982, it introduced
the Commodore 64 (64K RAM) and later the Commodore
128.  These were popular home computers, and over
10 million were sold.

   In 1985, the Amiga series was introduced, which
has continued to offer advanced imaging and video
capabilities at affordable prices.  A line of IBM-
compatible PCs were also introduced, but the Amiga
series was Commodore's mainstay until May of 1994,
when the company went into bankruptcy.  It is
expected that the company will be purchased by
another organization.



common carrier
A government-regulated organization that provides
telecommunications services for public use, such as
AT&T, the telephone companies, ITT, MCI and Western
Union.



Common Desktop Environment
See CDE.



Common Ground
Document exchange software from No Hands Software,
Inc., Belmont, CA, that converts a Windows or
Macintosh document into a proprietary file format
for viewing on other machines.  The viewer allows
multiple documents to be displayed at the same
time.



Common OS API
A specification for a standard UNIX programming
interface (API) which was defined in 1993 by all
major UNIX vendors, including Sun, HP, IBM, DEC,
Novell and SCO.  It led to Spec 1170, which is
governed by the X/Open consortium.



communications
The electronic transfer of information from one
location to another.  Data communications refers to
digital transmission, and telecommunications refers
to analog and digital transmission, including voice
and video.

                   The Protocol
The way communications systems "talk to" each other
is defined in a set of standards called protocols.
Protocols work in a hierarchy starting at the top
with the user's program and ending at the bottom
with the plugs, sockets and electrical signals.
See lessons communications, communications
protocol, OSI and OSI model.


         Personal Computer Communications
Personal computer communications takes several
forms.

VIA MODEM
Data can be transferred between two distant
personal computers by using modems, a telephone
line and a communications program in each computer.

BETWEEN TWO COMPUTERS
Data can be transferred between two local computers
by cabling them together with a null modem cable
and a file transfer program in each computer.

REMOTE TERMINAL
Personal computers can act like a remote terminal
to a mini or mainframe.  For example, a 3270
emulation board, such as DCA's Irma board, plugs
into a personal computer and turns it into an IBM
mainframe terminal.

NETWORK
Personal computers can be part of a local area
network (LAN), in which databases and printers are
shared among users.  If the LAN interconnects with
mini and mainframe networks, then personal
computers can communicate with larger computers.

   Increasingly, LANs of personal computers are
running applications previously delegated to minis
and mainframes.  These applications are designed as
"client/server" applications, which duplicate the
integrity, security and transaction processing
requirements of the larger computers.


            Minicomputer Communications
Minicomputer communications systems control as many
as several hundred terminals connected to a single
computer system.  They support a variety of low-
speed dial-up terminals and higher-speed local
terminals.  With larger minicomputers, the
communications processing is handled in separate
machines, called communications controllers.

   Minicomputers are designed with communications
in mind.  The communications programs and operating
systems are often integrated and provide simpler
operation than mainframes.

   Minicomputers can connect to a mainframe by
emulating a mainframe terminal, in which case, the
mainframe thinks it's talking to another user
terminal.  Minicomputers can connect directly to
some LANs, or to all LANs via a gateway, which
converts the protocols.


             Mainframe Communications
Mainframe systems can control several thousand
remote terminals.  They support a variety of low-
speed dial-up terminals and high-speed local
terminals.

   Large mainframes use separate machines, called
communications controllers or front end processors,
to handle the communications processing.  These
machines take the data from the mainframes and
package it for transmission over the network.  They
also strip the communications codes from the
incoming messages and send pure data to the
mainframes for processing.

   Mainframes set the standards for communications.
It's usually up to the mini and micro vendors to
provide compatibility with the mainframe systems.


         Analog vs Digital Communications
The most common form of long-distance
communications has been the telephone system,
which, up until a few years ago, transmitted only
voice frequencies.  This technique, known as analog
communications, has been error prone, because the
electronic frequencies get mixed together with
unwanted signals (noise) that are nearby.

   In analog telephone networks, amplifiers are
placed in the line every few miles to boost the
signal, but they cannot distinguish between signal
and noise.  Thus, the noise is amplified along with
the signal.  By the time the receiving person or
machine gets the signal, it may be impossible to
decipher it.

   In a digital network, only two (binary) distinct
frequencies or voltages are transmitted.  Instead
of amplifiers, repeaters are used, which analyze
the incoming signal and regenerate a new outgoing
signal.  Any noise on the line is filtered out at
the next repeater.  When data is made up of only
two signals (0 and 1), it can be more easily
distinguished from the garble.  Digital is simple!




Communications Act
The establishment of the Federal Communications
Commission (FCC) in 1934, the regulatory body for
interstate and foreign telecommunications.  Its
mission is to provide high-quality services at
reasonable cost to everyone in the U.S. on a
nondiscriminatory basis.



communications channel
Also called a circuit or line, it is a pathway over
which data is transferred between remote devices.
It may refer to the entire physical medium, such as
a telephone line, optical fiber, coaxial cable or
twisted wire pair, or, it may refer to one of
several carrier frequencies transmitted
simultaneously within the line as in broadband
transmission (see broadband).



communications controller
A peripheral control unit that connects several
communications lines to a computer and performs the
actual transmitting and receiving as well as
various message coding and decoding activities.

   Communications controllers are typically
nonprogrammable units designed for specific
protocols and communications tasks.  Contrast with
front end processor, which can be programmed for a
variety of protocols and network conditions.



communications network
The transmission channels interconnecting all
client and server stations as well as all
supporting hardware and software.



communications parameters
The basic settings for modem transmission, which
include bit rate (2400 bps, 9600 bps, etc.), parity
(none, even, odd), number of data bits (7 or 8) and
number of stop bits (typically 1).  See N-8-1.



communications program
Software that manages the transmission of data
between computers and terminals.  In personal
computers, it manages transmission to and from the
computer's serial port.  It includes several
communications protocols and can usually emulate
dumb terminals for hookup to minis and mainframes.

   In a file server, the communications program is
called the network operating system (NetWare,
LANtastic).  In mini and mainframe networks, the
programs that support communications are called
access methods, network control programs and TP
monitors.  See front end processor.



communications protocol
Hardware and software standards that govern
transmission between two stations.  On personal
computers, communications programs offer a variety
of protocols (Kermit, Xmodem, Zmodem, etc.) to
transfer files via modem.

   On LANs, data link protocols such as Ethernet,
Token Ring and FDDI provide the access method (OSI
layers 1 and 2) that moves packets from station to
station, and higher level protocols, such as
NetBIOS, IPX and TCP/IP (OSI layers 3, 4 and 5)
control and route the transmission.

   The following conceptual exchange is at the data
link level (Zmodem, Ethernet, etc.), which ensures
that a block of data is transferred between two
nodes without error.

              The Data Link Protocol
Are you there?  Yes, I am.  Are you ready to
receive?  Yes, I am.  Here comes the message--bla,
bla, bla-- did you get it?  Yes, I did.  Here comes
the next part--bla, bla, bla-- did you get it?  No,
I didn't.  Here it comes again-- bla, bla, bla--
did you get it?  Yes, I did.  There is no more.
Goodbye.  Goodbye.





communications satellite
A radio relay station in orbit 22,300 miles above
the equator.  It travels at the same rate of speed
as the earth (geosynchronous), so that it appears
stationary.  It contains many communications
channels that receive analog and digital signals
from earth stations.  All signals are transmitted
within a carrier frequency.

   The signals are amplified and transmitted back
to earth, covering either a small geographical area
(spot beam) or almost a third of the earth's
surface.  In the latter case, private data is often
encrypted.



communications server
A computer in a LAN that manages access to external
networks.  It controls a pool of modems allowing
remote users access to the network or allowing
network users access to outside lines.  Sometimes
gateways are called communications servers.



compact disc
See CD.



COMPACT II
A high-level numerical control programming language
used to generate instructions for numerical control
(machine tool) devices.



compandor
(COMpressor/exPANDOR)  A device that improves the
signal for AM radio transmission.  On outgoing
transmission, it raises the amplitude of weak
signals and lowers the amplitude of strong signals.
On incoming transmission, it restores the signal to
its original form.



companies
See hardware vendors, software vendors, vendors and
online services.



Compaq
(Compaq Computer Corporation, Houston, TX)  A
leading PC manufacturer founded in 1982 by Rod
Canion, Bill Murto and Jim Harris.  In 1983, it
shipped 53,000 PC-compatible COMPAQ Portables,
which resulted in $111 million in revenues and an
American business record.  The Portable's success
was due to its rugged construction, ability to run
all PC software and its semi-portability (it
weighed 30 pounds!).

   In 1984, it introduced its DESKPRO desktop
computers and achieved a computer-industry sales
record in its second year.  In 1986, it was the
first to offer a 386-based machine.  Throughout its
history, Compaq has been well respected for its
computer products.



comparator
A device that compares two quantities and
determines their equality.



compare
A fundamental computer capability.  By comparing
one set of data with another, the computer can
locate, analyze, select, reorder and make
decisions.  After comparing, the computer can
indicate whether the data were equal or which set
was numerically greater or less than the other.
See ASCII chart and "The 3 C's" in computer.



compatibility
See standards & compatibility.



compatibility mode
A feature of a computer or operating system that
allows it to run programs written for a different
system.  Programs often run slower in compatiblity
mode.



compilation
Compiling a program.  See compiler.



compile time
The time it takes to translate a program from
source language into machine language.  Link
editing time may also be included in compile time.



compiler
(1) Software that translates a high-level
programming language (COBOL, C, etc.) into machine
language.  A compiler usually generates assembly
language first and then translates the assembly
language into machine language.

   The following example compiles program
statements into machine language:

Source code   Assembly Language  Machine language
IF COUNT=10   Compare A to B     Compare 3477 2883
 GOTO DONE    If equal go to C   If = go to 23883
  ELSE        Go to D            Go to 23343
 GOTO AGAIN
ENDIF
              Actual machine code
            10010101001010001010100
            10101010010101001001010
            10100101010001010010010

(2) Software that converts a high-level language
into a lower-level representation.  For example, a
help compiler converts a text document embedded
with appropriate commands into an online help
system.  A dictionary compiler converts terms and
definitions into a dictionary lookup system.



compiler language
See high-level language and compiler.



complement
The number derived by subtracting a number from a
base number.  For example, the tens complement of 8
is 2.  In set theory, complement refers to all the
objects in one set that are not in another set.

   Complements are used in digital circuits,
because it's faster to subtract by adding
complements than by performing true subtraction.
The binary complement of a number is created by
reversing all bits and adding 1.  The carry from
the high-order position is eliminated.  The
following example subtracts 5 from 8.


   Decimal      Binary       Subtraction by
 Subtraction  Equivalent  Adding the complement
       8         1000          1000
      -5        -0101         +1011
                      
       3         0011          0011




component
One element of a larger system.  A hardware
component can be a device as small as a transistor
or as large as a disk drive as long as it is part
of a larger system.  Software components are
routines or modules within a larger system.



composite video
The video-only (no audio) part of a TV signal.
Used on early personal computers for TV hookup, it
mixes red, green, blue and sync signals like a
standard TV and is not as crisp as separate red,
green and blue cables (RGB).



compound document
A single document that contains a combination of
data structures such as text, graphics,
spreadsheets, sound and video clips.  OLE and
OpenDoc are examples of compound document
architectures for the desktop.  They allow the user
to edit each of the data objects by automatically
calling in the application that created them.



compress
To compact data to save space.  See data
compression.



compression
See data compression.



compression ratio
The measurement of compressed data.  For example, a
file compressed into 1/4th of its original size can
be expressed as 4:1, 25%, 75% or 2 bits per byte.



compressor
(1) A device that diminishes the range between the
strongest and weakest transmission signals.  See
compandor.

(2) A routine or program that compresses data.  See
data compression.



Compsurf
A NetWare utility that performs a high-level hard
disk format.  NetWare servers require their own
proprietary format.



CompTIA
(Computing Technology Industry Association)
Formerly ABCD:The Microcomputer Industry
Association, it is a membership organization of
resellers, distributors and manufacturers dedicated
to business ethics and professionalism, founded in
1982.  It sets voluntary guidelines and is involved
with many issues including product returns, frieght
and warranty claims and price protection.

   It also provides certification for computer
service technicians, known as A+, which is
administered by Drake testing centers throughout
the U.S. and Canada.  Address: 450 East 22nd St.,
Lombard, IL 60148, 708/268-1818.



CompuServe
An online information service that provides
conferencing, news, e-mail and access to a huge
number of technical support forums, software files
and databases.  The CompuServe Information Manager
(CIM) software makes it easier to navigate through
the system.  See online services.



compute
To perform mathematical operations or general
computer processing.  See computer (The 3 C's).



compute bound
Same as process bound.



computer
A general-purpose machine that processes data
according to a set of instructions that are stored
internally either temporarily or permanently.  The
computer and all equipment attached to it are
called hardware.  The instructions that tell it
what to do are called software.  A set of
instructions that perform a particular task is
called a program, or software program.


               WHAT A COMPUTER DOES
The instructions in the program direct the computer
to input, process and output as follows:


                   Input/Output
The computer can selectively retrieve data into its
main memory (RAM) from any peripheral device
(terminal, disk, tape, etc.) connected to it.
After processing the data internally, the computer
can send a copy of the results from its memory out
to any peripheral device.  The more memory it has,
the more programs and data it can work with at the
same time.


                      Storage
By outputting data onto a magnetic disk or tape,
the computer is able to store data permanently and
retrieve it when required.  A system's size is
based on how much disk storage it has.  The more
disk, the more data is immediately available.



                    PROCESSING
                   (The 3 C's*)
Once the data is in the computer's memory, the
computer can process it by calculating, comparing
and copying it.


                     Calculate
The computer can perform any mathematical operation
on data by adding, subtracting, multiplying and
dividing one set with another.


                      Compare
The computer can analyze and evaluate data by
matching it with sets of known data that are
included in the program or called in from storage.


                       Copy
The computer can move data around to create any
kind of report or listing in any order.

   By calculating, comparing and copying, the
computer accomplishes all forms of data processing.
For example, records are sorted into a new order by
comparing two records at a time and copying the
record with the lower value in front of the one
with the higher value.

   The computer finds one customer out of thousands
by comparing the requested account number to each
record in the file.  The dBASE query statement:
SUM SALARY FOR TITLE = "NURSE" causes the computer
to compare the title field in each record for NURSE
and then add (calculate) the salary field for each
match.

   In word processing, inserting and deleting text
is accomplished by copying characters from one
place to another.


                Remember The 3 C's*
If you wonder whether the computer can solve a
problem, identify your data on paper.  If it can be
calculated, compared and copied on paper, it can be
processed in the computer.

*(The 3 C's is a registered service mark of The
Computer Language Company Inc.)


            THE STORED PROGRAM CONCEPT
The computer's ability to call in instructions and
follow them is known as the stored program concept.

   Instructions are copied into memory from a disk,
tape or other source before any data can be
processed.  The computer is directed to start with
the first instruction in the program.  It copies
the instruction from memory into its control unit
circuit and matches it against its built-in set of
instructions.  If the instruction is valid, the
processor carries it out.  If not, the computer
comes to an abnormal end (abend, crash).

   The computer executes instructions sequentially
until it finds a GOTO instruction that tells it to
go to a different place in the program.  It can
execute millions of instructions per second tracing
the logic of the program over and over again on
each new set of data it brings in.

   As computers get faster, operations can be made
to overlap.  While one program is waiting for input
from one user, the operating system (master control
program) directs the computer to process data in
another program.  Large computers are designed to
allow inputs and outputs to occur simultaneously
with processing.  While one user's data is being
processed, data from the next user can be retrieved
into the computer.

   It can take hundreds of thousands of discrete
machine steps to perform very routine tasks.  Your
computer could easily execute a million
instructions to put a requested record on screen
for you.


             GENERATIONS OF COMPUTERS
First-generation computers, starting with the
UNIVAC I in 1951, used vacuum tubes, and their
memories were made of thin tubes of liquid mercury
and magnetic drums.

   Second-generation systems in the late 1950s
replaced tubes with transistors and used magnetic
cores for memories (IBM 1401, Honeywell 800).  Size
was reduced and reliability was significantly
improved.

   Third-generation computers, beginning in the mid
1960s, used the first integrated circuits (IBM 360,
CDC 6400) and the first operating systems and
DBMSs.  Online systems were widely developed,
although most processing was still batch oriented
using punched cards and magnetic tapes.

   Starting in the mid 1970s, the fourth generation
brought us computers made entirely of chips.  It
spawned the microprocessor and personal computer.
It introduced distributed processing and office
automation.  Query languages, report writers and
spreadsheets put large numbers of people in touch
with the computer for the first time.

   The fifth generation ought to become visible by
the mid 1990s with the more widespread use of voice
recognition, natural and foreign language
translation, optical disks and fiber optic
networks.  Higher-speed machines combined with more
sophisticated software will enable the average
computer to talk to us with reasonable intelligence
by the 21st century.


           COMPUTERS COME IN MANY SIZES
Computers are as small as a chip or as large as a
truck.  The difference is in the amount of work
they do within the same time frame.  Its power is
based on many factors, including word size and the
speed of its CPU, memory and peripherals.
Following is a rough guide to system cost:

Computer system type              Approximate price
(Bits show word size)                In 1993 $US
Computer on a chip  (chip only)
 (4, 8, 16-bit)                             $2 - 75
Microprocessor  (chip only)
 (4, 8, 16, 32, 64-bit)                   $5 - 1000
Personal computer (8, 16, 32, 64-bit) $500 - 15,000
Minicomputer  (16, 32, 64-bit)    $15,000 - 250,000
Supermini (32, 64-bit)           $200,000 - 750,000
Mini-supercomputer (64-bit)      $100,000 - 750,000
Mainframe  (32, 64-bit)        $150,000 - 3,000,000
Supercomputer (64-bit)      $1,000,000 - 20,000,000




computer-aided design
See CAD.



computer-aided engineering
See CAE.



computer-aided manufacturing
See CAM.



computer-aided software engineering
See CASE.



computer architecture
The design of a computer system.  It sets the
standard for all devices that connect to it and all
the software that runs on it.  It is based on the
type of programs that will run (business,
scientific) and the number of them run
concurrently.

   It specifies how much memory is needed and how
it is managed (memory protection, virtual memory,
virtual machine).  It specifies register size and
bus width (16-, 32-, 64-bit) and how concurrency is
handled (channels, bus mastering, parallel
processing).

   Its native language instruction set stipulates
what functions the computer performs and how
instructions are written to activate them.  This
determines how programs will communicate with it
forever after.

   The trend toward large, complicated instruction
sets has been reversed with RISC computers, which
use simpler instructions.  The result is a leaner,
faster computer, but requires that the compilers
generate more code for complex functions that used
to be handled in hardware.

   Fault tolerant operation influences every aspect
of computer architecture, and computers designed
for single purposes, such as array processors and
database machines, require special designs.



computer-assisted learning
See CBT.



computer-assisted retrieval
See CAR.



Computer Associates
See CA.



computer-based reference
See CBR.



computer-based training
See CBT.



computer books
See how to find a good computer book.



computer center
Same as datacenter.



computer cracker
A person who gains illegal entrance into a computer
system.



computer designer
A person who designs the electronic structure of a
computer.



computer exchange
A commodity exchange through which the public can
buy and sell used computers.  After a match, the
buyer sends a check to the exchange and the seller
sends the equipment to the buyer.  If the buyer
accepts it, the money is sent to the seller less
commission.  Commissions usually range from 10 to
20%.

   With the American Computer Exchange, equipment
is first sent to the exchange, which inspects it
and then sends it to the buyer.  For a list of used
computer prices from the American Computer
Exchange, see used computers.


    American Computer Exchange (AmCoEx)
     800/786-0717   FAX 404/250-1399

    Boston Computer Exchange (BoCoEx)
     617/542-4414   FAX 617/542-8849

    National Computer Exchange (NaComEx)
     212/614-0700   FAX 212/777-1290

    The Newman Group
     313/426-3200   FAX 313/426-0777





computer field
See industry topics.



computer graphics
See graphics.



computer industry
See industry topics.



computer language
A programming language, machine language or the
language of the computer industry.



Computer Library
A Ziff Communications Company division that
provides information services.  See Computer
Select.



computer literacy
Understanding computers and related systems.  It
includes a working vocabulary of computer and
information system components, the fundamental
principles of computer processing and a perspective
for how non-technical people interact with
technical people.

   It does not deal with how the computer works
(digital circuits), but does imply knowledge of how
the computer does its work (calculate, compare and
copy).  It requires a conceptual understanding of
systems analysis & design, application programming,
systems programming and datacenter operations.

   To be a computer literate manager, you must be
able to define information requirements effectively
and have an understanding of decision support
tools, such as query languages, report writers,
spreadsheets and financial planning systems.  To be
truly computer literate, you must understand
"standards & compatibility" in this database.  If
you can't sleep at night, it's a guaranteed cure
for insomnia!



Computer Museum
(The Computer Museum, Boston, MA)  A museum
dedicated to computers that provides an historical
display of computing devices as well as hands-on
exhibits of a wide variety of applications geared
to kids and adults.  You can run the world's
largest personal computer (as big as a house) and
literally walk through its components.

   The Computer Museum is funded by several
computer companies as well as private individuals.
The Museum Store sells a unique variety of computer
games, books, jewelry and artifacts.  Open daily in
the summer from 10am to 6pm.  Winter hours are 10am
to 5pm, Tuesday thru Sunday, except holidays and
Boston school vacations.  Address: 300 Congress
St., Boston, MA 02210, 617/423-6758.  Call 800/370-
CHIP for group rates and reservations.



computer on a chip
A single chip that contains the processor, RAM,
ROM, clock and I/O control unit.  It is used for
myriads of applications from automobiles to toys.



computer power
The effective performance of a computer.  It can be
expressed in MIPS (millions of instructions per
second), clock speed (10Mhz, 16Mhz) and in word or
bus size, (16-bit, 32-bit).  However, as with
automobile horsepower, valves and cylinders, such
specifications are only guidelines.  Real power is
whether it gets your job done quickly.

   A software package is "powerful" if it has a
large number of features.



Computer Press Association
See CPA.  Remember... use the acronym first!



computer readable
Same as machine readable.



computer science
The field of computer hardware and software.  It
includes systems analysis & design, application and
system software design and programming and
datacenter operations.  For young students, the
emphasis in typically on learning a programming
language or running a personal computer with little
attention to information science, the study of
information and its uses.

   If students were introduced to data
administration, DBMS concepts and transaction and
master files, they would have a better grasp of an
organization's typical information requirements.



Computer Security Act
The first step in improving the security and
privacy of information contained in federal
computer systems.  Signed January 8, 1988 by
President Reagan, the Act:

   Establishes a central authority for developing
guidelines for protecting unclassified, but
sensitive information stored in government
computers.

   Requires each agency to formulate a computer
security plan, tailored to its own circumstances
and based on the guidelines.

   Mandates that each agency provide training for
its computer employees on the threats and
vulnerabilities of its computer systems.

   Ensures that the National Security Agency and
other defense-related government agencies not
control computer security standards in civilian
agencies of government.



Computer Select
A CD-ROM service from Computer Library that
provides articles and abstracts from over 140
computer-related periodicals.  It includes over
67,000 hardware, software and communications
products and 11,000 manufacturer's profiles.
Subscribers receive a CD-ROM every month with
articles from the preceding 12 months.



computer services
Data processing (timesharing, batch processing),
software development and consulting services.  See
service bureau.



computer system
The complete computer made up of the CPU, memory
and related electronics (main cabinet), all the
peripheral devices connected to it and its
operating system.  Computer systems fall into
ranges called microcomputers (personal computers),
minicomputers and mainframes, roughly small, medium
and large.

   Computer systems are sized for the total user
workload based on (1) number of terminals required,
(2) type of work performed (interactive processing,
batch processing, CAD, engineering, scientific),
and (3) amount of online data required.

   Following are the components of a computer
system and their significance:

   Component              Significance
Machine language   Compatibility with future
                    hardware/software
Operating system   Performance and future
                    hardware/software compatibility
Clock speed        Performance
  (MIPS rate)
Number  of         Number of concurrent users
  terminals
Memory capacity    Performance
Disk capacity      Amount of available information
Communications     Access to inhouse and external
                    information
Programming        Compatibility with future
  languages         hardware
Fail-safe design   Reliability




computer telephone integration
See CTI.



computer trends
See hot topics.



computercruiter
Slang for a recruiter that specializes in computer
professionals.



computerized branch exchange
See PBX.



Computex
A Taiwanese trade show for PC manufacturers and PC
component buyers promoted by the China External
Trade Development Council.  For information, call
Taiwan 886-2-725-5200, FAX 886-2-757-6653.



Computing Technology Industry Association
See CompTIA.



COMSAT
(COMmunications SATellite Corporation)  A private
communications satellite company created by
Congress in 1962 that provides communications
capacity to carriers such as AT&T and MCI.  In
1965, it launched Early Bird, the first commercial
satellite to transmit signals from a geosynchronous
orbit.  See INTELSAT and INMARSAT.



Comspec
See DOS Comspec.



CON
(CONsole)  The DOS name for the keyboard and
screen.  See DOS device names and DOS Copy con.



concatenate
To link structures together.  Concatenating files
appends one file to another.  In speech synthesis,
units of speech called phonemes (k, sh, ch, etc.)
are concatenated to produce meaningful sounds.



concentrator
A device that joins several communications channels
together.  It is similar to a multiplexor except
that it does not spread the signals back out again
on the other end.  The receiving computer performs
that function.



conceptual view
See view.



concurrency control
In a DBMS, managing the simultaneous access to a
database.  It prevents two users from editing the
same record at the same time and is also concerned
with serializing transactions for backup and
recovery.



Concurrent DOS
An early multiuser DOS-compatible operating system
from Digital Research.  See Multiuser DOS.



concurrent operation
See multitasking, multiprocessing and parallel
processing.



concurrent processing
See multiprocessing.



conditional branch
In programming, an instruction that directs the
computer to another part of the program based on
the results of a compare.  In the following
(simulated) assembly language example, the second
line is the conditional branch.

       COMPARE FIELDA with FIELDB
       GOTO MATCHROUTINE if EQUAL.

   High-level language statements, such as IF THEN
ELSE and CASE, are used to express the compare and
conditional branch.



conditioning
Extra cost options in a private telephone line that
improve performance by reducing distortion and
amplifying weak signals.



conductor
A material that can carry electrical current.
Contrast with insulator.



conferencing
Conducting a communications session with three or
more users.  See teleconferencing.



CONFIG.SYS
A DOS and OS/2 configuration file.  It resides in
the root directory and is used to load drivers and
change settings at startup.  Install programs often
modify CONFIG.SYS in order to customize the
computer for their particular use.  See DOS
CONFIG.SYS.



configuration
The makeup of a system.  To "configure" is to
choose options in order to create a custom system.
"Configurability" is a system's ability to be
changed or customized.



configuration file
A file that contains information about a specific
user, program, computer or file.



configuration management
(1) In a network, a system for gathering current
configuration information from all nodes in a LAN.

(2) In software development, a system for keeping
track of large projects.  Although version control,
which maintains a database of revisions, is part of
the system, a full-blown software configuration
management system (SCM system or CM system)
automatically documents all components used to
build executable programs.  It is able to recreate
each build as well as to recreate earlier
environments in order to maintain previous versions
of a product.  It may also be used to prevent
unauthorized access to files or to alert the
appropriate users when a file has been altered.

   Increasingly, parts of version control and
configuration management are being added to
application development systems.

   Examples of stand-alone configuration management
systems are PVCS, the CCC products from Softool and
ClearCase.



configure
See configuration.



connect time
The amount of time a user at a terminal is logged
on to a computer system.  See online services and
service bureau.



Connection Machine
A family of parallel processing computers from
Thinking Machines Corporation, Cambridge, MA, that
contain from 4K to 64K processors.  They can be set
up as hypercubes or other topologies and require
another computer as a front end.  Used for such
applications as signal processing, simulation and
database retrieval.



connection oriented
In communications, requiring a direct connection or
established session or circuit between two nodes
for transmission.  Transmission within a wide area
network (WAN) is typically connection oriented.
Once established, the circuit, whether physical or
virtual, is dedicated to that single transmission
until the session is completed.  Contrast with
connectionless.



connectionless
In communications, the inclusion of source and
destination addresses within each packet so that a
direct connection or established session between
nodes is not required.  Transmission within a local
area network (LAN) is typically connectionless.
Each data packet sent contains the address of where
it is going.  Contrast with connection oriented.



connectivity
(1) Generally, the term refers to communications
networks or the act of communicating between
computers and terminals.

(2) Specifically, the term refers to devices such
as bridges, routers and gateways that link networks
together.



connector
(1) Any plug, socket or wire that links two devices
together.

(2) In database management, a link or pointer
between two data structures.

(3) In flowcharting, a symbol used to break a
sequence and resume the sequence elsewhere.  It is
often a small circle with a number in it.



console
(1) A terminal used to monitor and control a
computer or network.

(2) Any display terminal.



constant
In programming, a fixed value in a program.
Minimum and maximum amounts, dates, prices,
headlines and error messages are examples.



constant bit rate
See CBR.



constant ratio code
A code that always contains the same ratio of 0s to
1s.



consultant
An independent specialist that may act as an
advisor or perform detailed systems analysis and
design.  They often help users create functional
specifications from which hardware or software
vendors can respond.



contact
A metal strip in a switch or socket that touches a
corresponding strip in order to make a connection
for current to pass.  Contacts may be made of
precious metals to avoid corrosion.



contact manager
Software that keeps track of sales prospects.  It
holds names and addresses and is used for
appointments similar to a personal information
manager (PIM), but is specialized for sales reps
that make repetitive contact with a large number of
prospective customers.



contention
A condition that arises when two devices attempt to
use a single resource at the same time.  See
CSMA/CD.



contention resolution
Deciding which device gains access to a resource
first when more than one wants it at the same time.



context sensitive help
Help screens that provide specific information
about the condition or mode the program is in at
the time help is sought.



context switching
Switching between active applications.  It often
refers to a user jumping back and forth between
several programs in contrast with repeated task
switching performed by the operating system.
However, the terms context switching and task
switching are used synonymously.



contextual search
To search for records or documents based upon the
text contained in any part of the file as opposed
to searching on a pre-defined key field.



contiguous
Adjacent or touching.  Contrast with fragmentation.



continuity check
A test of a line, channel or circuit to determine
if the pathway exists from beginning to end and can
transmit signals.



continuous carrier
In communications, a carrier frequency that is
transmitted even when data is not being sent over
the line.



continuous forms
A roll of paper forms with perforations for
separation into individual sheets after printing.
See pin feed and burster.



contrast
The difference between the lightest and darkest
areas on a display screen.  Contrast with
brightness.



control ball
Same as trackball.



control block
A segment of disk or memory that contains a group
of codes used for identification and control
purposes.



control break
(1) A change of category used to trigger a
subtotal.   For example, if data is subtotalled by
state, a control break occurs when NJ changes to
NM.

(2) See Ctrl-Break.



control character
See control code.



control code
One or more characters used as a command to control
a device.  The first 32 characters in the ASCII
character set are control codes for communications
and printers.  There are countless codes used to
control electronic devices.  See escape character.



Control Data
(Control Data Systems, Inc., Arden Hills, MN)  One
of the first computer companies.  Founded in 1957,
Bill Norris was its first president and guiding
force.  Its first computer, the 1604, was
introduced in 1957 and delivered to the U.S. Navy
Bureau of Ships.

   For more than 30 years, the company was widely
respected for its high-speed computers used heavily
in government and scientific installations.  Using
the CYBER trade name, Control Data produced a
complete line from workstations to mainframes.  It
also manufactured supercomputers.

   In 1992, it spun off its military involvement
into an independent company called Ceridian
Corporation, and Control Data Corporation became
Control Data Systems.  Soon after, it ceased R&D of
its proprietary computers.  While providing
maintenance for its installed base, it currently
specializes in systems integration of UNIX-based
computers from HP, Sun and Silicon Graphics, which
includes custom software, consulting services and
facilities management.



control field
Same as key field.



control key
Abbreviated "ctrl" or "ctl."  A keyboard key that
is pressed with a letter or digit key to command
the computer; for example, holding down control and
pressing U, turns on underline in some word
processors.  The caret (shift-6) symbol represents
the control key: ^Y means control-Y.



control network
A network of sensors and actuators used for home
automation and industrial control.



Control Panel
A routine that changes the computer's environment
settings, such as keyboard and mouse sensitivity,
sounds, colors and communications and printer
access.  It is a desk accessory in the Macintosh
and a utility program in Windows.



control parallel
Same as MIMD.



control program
Software that controls the operation of and has
highest priority in a computer.  Operating systems,
network operating systems and network control
programs are examples.  Contrast with application
program.



Control Program Facility
See CPF.



control total
Same as hash total.



control unit
(1) Within the processor, the circuitry that
locates, analyzes and executes each instruction in
the program.

(2) Within the computer, a control unit, or
controller, is hardware that performs the physical
data transfers between memory and a peripheral
device, such as a disk or screen, or a network.

   Personal computer control units are contained on
a single plug-in expansion board, called a
controller or adapter (disk controller, display
adapter, network adapter, etc.).  In large
computers, they may be contained on one or more
boards or in a stand-alone cabinet.

   In single chip computers, a built-in control
unit accepts keyboard input and provides serial
output to a display.



control variable
In programming, a variable that keeps track of the
number of iterations of a process.  Its value is
incremented or decremented with each iteration, and
it is compared to a constant or other variable to
test the end of the process or loop.



controller
An electronic circuit board or system that controls
a peripheral device.  See control unit (2).



conventional memory
In a PC, the first 640K of memory.  The next 384K
is called the UMA (upper memory area).  The term
may also refer to the entire first megabyte (1024K)
of RAM, which is the memory that DOS can directly
manage without the use of additional memory
managers.  See DOS memory manager.



conventional programming
Writing a program in a traditional procedural
language, such as assembly language or a high-level
compiler language (C, Pascal, COBOL, FORTRAN,
etc.).



convergence
(1) The intersection of red, green and blue
electron beams on one CRT pixel.  Poor convergence
decreases resolution and muddies white pixels.

(2) See digital convergence.



conversational
An interactive dialogue between the user and the
computer.



conversion
(1) Data conversion is changing data from one file
or database format to another.  It may also require
code conversion between ASCII and EBCDIC.

(2) Media conversion is changing storage media such
as from tape to disk.

(3) Program conversion is changing the programming
source language from one dialect to another, or
changing application programs to link to a new
operating system or DBMS.

(4) Computer system conversion is changing the
computer model and peripheral devices.

(5) Information system conversion requires data
conversion and either program conversion or the
installation of newly purchased or created
application programs.



converter
(1) A device that changes one set of codes, modes,
sequences or frequencies to a different set.  See
A/D converter.

(2) A device that changes current from 60Hz to
50Hz, and vice versa.



cooperative multitasking
Same as non-preemtive multitasking.



cooperative processing
Sharing a job among two or more computers such as a
mainframe and a personal computer.  It implies
splitting the workload for the most efficiency.



coordinate
Belonging to a system of indexing by two or more
terms.  For example, points on a plane, cells in a
spreadsheet and bits in dynamic RAM chips are
identified by a pair of coordinates.  Points in
space are identified by sets of three coordinates.



copper
(Cu) A reddish-brown metal that is highly
conductive and widely used for electrical wire.
When a signal "runs over copper," it means that a
metal wire is used rather than a glass wire
(optical fiber).



coprocessor
A secondary processor used to speed up operations
by handling some of the workload of the main CPU.
See math coprocessor and graphics coprocessor.



copy
To make a duplicate of the original.  In digital
electronics, all copies are identical.

   The text in this database takes up about two
megabytes.  During the course of writing and
updating it, the text has been copied hundreds of
times, causing billions of bits to be transmitted
between disk and memory.  Just to show that things
aren't entirely perfect, a character does get
garbled every once in a while.  We'll have to
settle for 99.9999% instead of 100%!  See DOS Copy.



copy buster
A program that bypasses the copy protection scheme
in a software program and allows normal,
unprotected copies to be made.



copy protection
Resistance to unauthorized copying of software.
Copy protection was never a serious issue with
mainframes and minicomputers, since vendor support
has always been vital in those environments.

   In the early days of floppy-based personal
computers, many copy protection methods were used.
However, with each scheme introduced, a copy buster
program was developed to get around it.  When hard
disks became the norm, copy protection was
abolished.  In order to manage a hard disk, files
must be easily copied from one part of the disk to
another.

   This is a constant dilemma for software vendors
as well as the publishing and broadcasting
industries that transmit their content via digital
means.  Every recipient of a digitally-distributed
medium has the ability to reproduce a perfect copy
of the original.

   The only copy protection system that works is
the hardware key, which is a plug and socket that
is attached to the computer's parallel port with a
unique serial number that the software identifies.
Hardware keys are used to protect high-priced
software, but users are generally not fond of them,
because it requires unplugging the printer cable,
inserting the hardware key, and plugging back the
printer.

   A system similar to the hardware key designed
into the personal computer from day one should have
been established.  Perhaps some day a solid state
software capsule with a digital signature will plug
into the computer.  In the meantime, anyone who can
figure out an economical way to prevent
unauthorized duplication of digital material that
does not interfere with managing a hard disk or the
quality of the original transmission will become
the country's first trillionaire!



CORBA
(Common ORB Architecture)  An Object Request Broker
(ORB) standard endorsed by the Object Management
Group (OMG).  An ORB is software that handles the
communication of messages to and from objects in a
distributed, multi-platform environment.

   The concept behind CORBA is to eliminate the
need to program networking details between client
and server when developing programs in a
distributed environment.  A client makes a request
to the ORB, and the ORB directs it to the
appropriate server that can satsify the request and
redirects the results back to the client.


                 Ŀ
    Ŀ     Object      Ŀ
    Client߳Request߳Server
         Broker      
                 


   The first version of CORBA addressed portability
across platforms, and implementations such as IBM's
SOM/DSOM, Sun's DOE and HP's DOMF were designed to
this specification.  In late 1994, the CORBA 2
specification was introduced to support
interoperability between ORBs from different
vendors.





core
A round magnetic doughnut that represents one bit
in a core storage system.  A computer's main memory
used to be referred to as core.



core storage
A non-volatile memory that holds magnetic charges
in ferrite cores about 1/16th" diameter.  The
direction of the flux determines the 0 or 1.
Developed in the late 1940s by Jay W. Forrester and
Dr. An Wang, it was used extensively in the 1950s
and 1960s.  Since it holds its content without
power, it is still used in specialized applications
in the military and in space vehicles.

   In 1956, IBM paid Dr. Wang $500,000 for his
patent on core memories, which he used to expand
his company, Wang Laboratories.



Core System
The first proposed standard for computer graphics,
developed by the Graphics Standards Planning
Committee of SIGGRAPH and used in the late 1970s
and early 1980s.  Its objectives were portability
of programs between computers and the separation of
modeling graphics from viewing graphics.  Almost
all features of the Core System were incorporated
into the ANSI-endorsed GKS standard.



Corel VENTURA
A Windows desktop publishing program from Corel
Corporation, Ottawa, Ontario.  It is a high-end DTP
program that is noted for its sophisticated full-
scale pagination capabilities for long documents.
It is designed to import data from other graphics
and word processing programs and includes several
graphics functions from CorelDRAW.

   Corel VENTURA was formerly Ventura Publisher,
which was developed by a company that was acquired
by Xerox.  The early versions were available for
DOS, Windows, OS/2 and the Macintosh.  In 1993,
Corel acquired it, made substantial improvements to
it includes it in its CorelDRAW suite.  Corel
VENTURA is also available stand alone.



CorelDRAW
A suite of Windows graphics applications from Corel
Corporation, Ottawa, Ontario.  CorelDRAW was
originally a drawing program introduced in 1989,
which became popular due to its speed and ease of
use.  As of CorelDRAW 5, it is a complete suite of
applications for image editing, charting and
presentations as well as desktop publishing, with
the inclusion of Corel VENTURA.



CorelRAID
Software from Corel Systems Corporation, Ottawa,
Ontario, that creates RAID arrays on a Novel 3.11
server using an ASPI-compatible SCSI host adapter
and three or more SCSI disks.



CorelSCSI
A SCSI driver from Corel Systems Corporation,
Ottawa, Ontario, that supports a wide variety of
SCSI devices, including removable media, juke
boxes, digital cameras and WORM drives and
translates them into the ASPI standard.  See
PowerSCSI!.



corona wire
A charged wire in a laser printer that draws the
toner off the drum onto the paper.  It must be
cleaned when the toner cartridge is replaced.



Corporation for Open Systems
See COS.



corrupted file
A data or program file that has been altered
accidentally by hardware or software failure,
causing the bits to be rearranged and rendering it
unreadable.



corruption
Altering of data or programs due to viruses,
hardware or software failure or power failure.  See
data recovery.



CorStream
A network operating system from Artisoft, Inc.,
Tucson, AZ, makers of LANtastic.  CorStream is a
version of Novell's NetWare 4.x combined with an
Artisoft NLM, which turns a PC into a high-speed
LANtastic server.  LANtastic clients communicate
with CorStream as if it was another LANtastic
server.



COS
(Corporation for Open Systems International)  A not
for profit R&D consortium founded in 1986,
dedicated to assuring acceptance of a worldwide
open network architecture.  It is made up of
manufacturers and user organizations that provide
development, service, and support of systems that
conform to international standards, including OSI
and ISDN.  Address: 1750 Old Meadow Road, Suite
400, McLean, VA 22102, 703/883-2700.



COSE
(Common Open Software Environment)  Pronounced
"cozy."  An alliance of major UNIX vendors (IBM,
HP, Sun, Univel, USL and SCO) dedicated to
standardizing open systems.  In 1993, COSE's first
specification was the CDE (Common Desktop
Environment), a user interface based on Motif.

   COSE is expected to disband as soon as CDE
Version 1.0 is completed.  All future work will be
done by OSF.



cosine
See sine.



cost-based query optimizer
Software that optimizes an SQL query for the
fastest processing, based on the size of the file
and other variables.



cost/benefits analysis
The study that projects the costs and benefits of a
new information system.  Costs include people and
machine resources for development as well as
running the system.

   Tangible benefits are derived by estimating the
cost savings of both human and machine resources to
run the new system versus the old one.  Intangible
benefits, such as improved customer service and
employee relations, may ultimately provide the
largest payback, but are harder to quantify.



counter
(1) In programming, a variable that is used to keep
track of anything that must be counted.  The
programming language determines the number of
counters (variables) that are available to a
programmer.

(2) In electronics, a circuit that counts pulses
and generates an output at a specified time.



Courier
A monospaced typeface originating from the
typewriter that is commonly used for letters.  It
is still considered by many to be the "appropriate"
typeface for business correspondence.



courseware
Educational software.  See CBT.



covert channel
A transfer of information that violates a
computer's built-in security systems.  A covert
storage channel refers to depositing information in
a memory or storage location that can be accessed
by different security clearances.  A covert timing
channel is the manipulation of a system resource in
such a way that it can be detected by another
process.



cow
See CAU.



cozy
See COSE.



CP
(1) (Copy Protected)  See copy protection.

(2) (Central Processor)  See processor and CPU.

(3) See control program.



CP/M
(Control Program for Microprocessors)  A single
user operating system for the 8080 and Z80
microprocessors from Digital Research.  Created by
Gary Kildall, CP/M had its heyday in the early
1980s.

   CP/M was an unsophisticated program that didn't
instill confidence in users, yet it was a major
contributor to the personal computer revolution.
Because the industry never standardized on a CP/M
disk or video format, software publishers had to
support dozens of screen displays and floppy disk
formats.  This chaos helped IBM set the standard
with its PC.

   Although IBM asked Kildall to provide the
operating system for its new PC, he didn't agree to
certain demands.  IBM went to Microsoft, which
purchased an operating system from another company
and turned it into DOS.  DOS was modeled after
CP/M.



CPA
(Computer Press Association)  An organization
founded in 1983 that promotes excellence in
computer journalism.  Comprised of approximately
300 members (1992), its annual awards honor
outstanding journalism in print, broadcast and
electronic media.  Address is 529 18th Ave., San
Francisco, CA 94121, 415/750-9281.



CPE
(Customer Premises Equipment)  Communications
equipment that resides on the customer's premises.



CPF
(Control Program Facility)  The IBM System/38
operating system that included an integrated
relational DBMS.



CPGA
(Ceramic PGA)  See PGA.



cpi
(1) (Characters Per Inch)  The measurement of the
density of characters per inch on tape or paper.  A
printer's CPI button switches character pitch.

(2) (Counts Per Inch)  The measurement of the
resolution of a mouse/trackball as flywheel notches
per inch (horizontal and vertical flywheels rotate
as the ball is moved).  Notches are converted to
cursor movement.

(3) (CPI) (Common Programming Interface)  See SAA
and CPI-C.



CPI-C
(Common Programming Interface for Communications)
A general-purpose communications interface under
IBM's SAA.  Using APPC verbs as its foundation, it
provides a common programming interface across IBM
platforms.  See APPC.



CPM
(Critical Path Method)  A project management
planning and control technique implemented on
computers.  The critical path is the series of
activities and tasks in the project that have no
built-in slack time.  Any task in the critical path
that takes longer than expected will lengthen the
total time of the project.



cps
(1) (Characters Per Second)  The measurement of the
speed of a serial printer or the speed of a data
transfer between hardware devices or over a
communications channel.  CPS is equivalent to bytes
per second.

(2) (CPS) (Certified Product Specialist)  See
Microsoft Certified Professional.



CPU
(Central Processing Unit)  The computing part of
the computer.  Also called the processor, it is
made up of the control unit and ALU.

   A personal computer CPU is a single
microprocessor chip.  A minicomputer CPU is
contained on one or more printed circuit boards.  A
mainframe CPU is made up of several boards.

   The CPU, clock and main memory make up a
computer.  A complete computer system requires the
addition of control units, input, output and
storage devices and an operating system.


         From the Mainframe Point of View
Computer professionals involved with mainframes and
minicomputers often refer to the whole computer as
the CPU, in which case, CPU refers to the
processor, memory (RAM) and I/O architecture
(channels or buses).



CPU bound
Same as process bound.



CPU cache
See cache.



CPU chip
Same as microprocessor.



CPU time
The amount of time it takes for the CPU to execute
a set of instructions and explicitly excludes the
waiting time for input and output.



CR
(Carriage Return)  The return key or the actual
code that is generated when the key is pressed
(decimal 13, hex 0D).  See return key.



CR/LF
(Carriage Return/Line Feed)  The end of line
characters used in standard PC text files (ASCII 13
10).  In the Mac, only the CR is used; in UNIX, the
LF.



CRAM
(Card RAM)  A magnetic card mass storage device
made by NCR in the 1960s.  In order to read or
write data, a card was pulled out of the cartridge
and wrapped around a rotating drum.



crash
See abend and head crash.



crash recovery
The ability to automatically correct a hardware,
software or line failure.



Cray
(Cray Research, Inc., Eagan, MN)  A supercomputer
manufacturer founded in 1972 by Seymour Cray, a
leading designer of large-scale computers at
Control Data.  In 1976, it shipped its first
computer to Los Alamos National Laboratory.  The
CRAY-1 was a 75MHz, 64-bit machine with a peak
speed of 160 megaflops, making it the world's
fastest vector processor.

   The company has since launched the X-MP, Y-MP
and C-90 series.  Its YMP line ranges from entry-
level to midrange supercomputers used in industrial
and technical applications in commercial companies.
Cray's C-90 high-end multiprocessor line is used in
scientific applications with its fastest
configuration performing 16 gigaflops and costing
$30 million dollars.  In 1995, Cray is expected to
release its Triton line, which will be even four
times faster.

   Cray also incorporates its unique system
architecture into a line of SPARC and Alpha-based
machines.  All Cray computers use the UNIX
operating system.

   In 1989, the founder left Cray Research and
founded Cray Computer Corporation in Colorado
Springs, CO.  To date, the Cray-3 has been
developed, and the Cray-4 is in the offing.  Always
his purpose, Mr. Cray continues the quest for the
world's fastest computer.



CRC
(Cyclical Redundancy Checking)  An error checking
technique used to ensure the accuracy of
transmitting digital data.  The transmitted
messages are divided into predetermined lengths
which, used as dividends, are divided by a fixed
divisor.  The remainder of the calculation is
appended onto and sent with the message.  At the
receiving end, the computer recalculates the
remainder.  If it does not match the transmitted
remainder, an error is detected.



Creative Labs
(Creative Labs, Inc., Milpitas, CA)  A manufacturer
of sound cards and products that was founded in
1988 by Sim Wong Hoo.  It introduced the Game
Blaster stereo sound board in 1988, and in 1989,
the Sound Blaster card, which has become a de facto
standard.  In 1991, it launched the Sound Blaster
Multimedia Upgrade Kit.



Cricket Presents
See CA-Cricket Presents.



crippleware
Demonstration software with built-in limitations;
for example, a database package that lets only 50
records be entered.



Cristina Foundation
See National Cristina Foundation.



criteria range
Conditions for selecting records; for example,
"Illinois customers with balances over $10,000."



crop marks
Printed lines on paper used to cut the form into
its intended size.



cross assembler
An assembler that generates machine language for a
foreign computer.  It is used to develop programs
for computers on a chip or microprocessors used in
specialized applications, which are either too
small or are incapable of handling the development
software.



cross compiler
A compiler that generates machine language for a
foreign computer.  See cross assembler.



Cross System Product
See CSP.



cross tabulate
To analyze and summarize data.  A common example is
summarizing the details from database records and
placing them into a spreadsheet.  The following
example places the details of order records into
summary form.

     Transactions being cross tabbed
     Date      Customer    Quantity
     1- 7-93   Smith           7
     1-13-93   Jones          12
     2- 5-93   Gonzales        4
     2-11-93   Fetzer          6
     3-10-93   Smith          12
     3-22-93   Gonzales       15


     Results of cross tab
     Customer   Jan   Feb   Mar   Total
     Smith        7          12      19
     Jones       12                  12
     Gonzales           4    15      19
     Fetzer             6             6

     Total       19    10    27      56





crossbar switch
See crosspoint switch.



crossfoot
A numerical error checking technique that compares
the sum of the columns with the sum of the rows.



crosshatch
A criss-crossed pattern used to fill in sections of
a drawing to distinguish them from each other.



crossover cable
Same as null modem cable.



crosspoint switch
Also known as a crossbar or NxN switch, it is a
switching device that provides for a fixed number
of inputs and outputs.  For example, a 32x32 switch
is able to keep 32 nodes communicating at full
speed to 32 other nodes.



crosstalk
(1) In communications, interference from an
adjacent channel.

(2) (Crosstalk)  Communications programs for DOS
and Windows from DCA, Inc., Alpharetta, GA.
Crosstalk products were originally developed by
Microstuf, Inc., which was later merged with DCA.
It was one of the first personal computer
communications programs, originating in the CP/M
days.  Crosstalk includes user-definable menus and
a scripting language called CASL (Crosstalk
Application Script Language).



CRT
(Cathode Ray Tube)  A vacuum tube used as a display
screen in a video terminal or TV.  The term often
refers to the entire terminal.



crunch
(1) To process data.  See number crunching.

(2) To compress data.  See data compression.



cryogenics
Using materials that operate at very cold
temperatures.  See superconductor.



cryptography
Conversion of data into a secret code for security
purposes.  Same as encryption.



crystal
A solid material containing a uniform arrangement
of molecules.  See quartz crystal.



crystalline
The solid state of a crystal.  Contrast with
nematic.



CSA
(1) (Canadian Standards Association)  The Canadian
counterpart of U.S. Underwriters Laboratory.

(2) (Client Server Architecture)  See
client/server.

(3) (CallPath Services Architecture)  An IBM
standard that integrates applications with the
telephone system, designed for use with AT&T,
Northern Telecom and other PBX vendors.



CSE
(Certified Systems Engineer)  See Microsoft
Certified Professional.



CSIC
(Customer Specific Integrated Circuit)  Pronounced
"C-sick."  Custom-developed chips from Motorola.



CSMA/CD
(Carrier Sense Multiple Access/Collision Detection)
The LAN access method used in Ethernet.  When a
device wants to gain access to the network, it
checks to see if the network is free.  If it is
not, it waits a random amount of time before
retrying.  If the network is free and two devices
attempt access at exactly the same time, they both
back off to avoid a collision and each wait a
random amount of time before retrying.



CSP
(1) (Cross System Product)  An IBM application
generator that runs in all SAA environments.
CSP/AD (CSP/Application Development) programs
provide the interactive development environment and
generate a pseudo code that is interpreted by
CSP/AE (CSP/Application Execution) software in the
running computer.  For AS/400 applications, CSP/AD
generates compiled code.  For the PS/2, EZ-PREP and
EZ-RUN are the CSP/AD and CSP/AE counterparts.

(2) (Certified Systems Professional)  The award for
successful completion of an ICCP examination in
systems development.



CSTA
(Computer Supported Telephony Application)  An
international standard interface between a network
server and a telephone switch (PBX) established by
the European Computer Manufacturers Association
(ECMA).



CSU
See DSU/CSU.



CSV
(Comma Separated Value)  Same as comma delimited.



CT
(Certified Trainer)  See Microsoft Certified
Professional.



CTI
(Computer Telephone Integration)  Combining data
with voice systems in order to enhance telephone
services.  For example, automatic number
identification (ANI) allows a caller's records to
be retrieved from the database while the call is
routed to the appropriate party.  Automatic
telephone dialing from an address list is an
outbound example.



CTIA
(1) See CompTIA.

(2) (Cellular Telecommunications Industry
Association)  A membership organization founded in
1984 that is involved with regulatory and public
affairs issues in the cellular phone industry.
Address: 1250 Connecticut Ave., N.W., Washington,
DC 20036, 202/785-0081.



Ctl
See control key.



CTO
(Chief Technical Officer)  The executive
responsible for the technical direction of an
organization.



CTOS
An operating system that runs on Unisys' x86-based
SuperGen series (formerly the B-series).  It was
originally developed by Convergent Technologies,
which was acquired by Unisys.  Designed for network
use, its message-based approach allows program
requests to be directed to any station in the
network.



Ctrl
See control key.



Ctrl-Alt-Del
In a PC, holding down the CTRL and ALT keys and
pressing the DEL key reboots the system.



Ctrl-Break
In a PC, holding down the CTRL key and pressing the
BREAK key cancels the running program or batch
file.  Same as Ctrl-C.  See DOS Break.



Ctrl-C
In a PC, holding down the CTRL key and pressing the
C key cancels the running program or batch file.
Same as Ctrl-Break.  See DOS Break.



Ctrl-S
In a PC, holding down the CTRL key and pressing the
S key pauses and continues the running program.



CTS
(1) (Clear To Send)  The RS-232 signal sent from
the receiving station to the transmitting station
that indicates it is ready to accept data.
Contrast with RTS.

(2) See carpal tunnel syndrome.



CUA
(Common User Access)  SAA specifications for user
interfaces, which includes OS/2 PM and character-
based formats of 3270 terminals.  It is intended to
provide a consistent look and feel across platforms
and between applications.



CUI
(Character-based User Interface)  A user interface
that uses the character, or text, mode of the
computer and typically refers to typing in
commands.  Contrast with GUI.



Curie point
The temperature (150 C) at which certain elements
are susceptible to magnetism.  See magneto-optic.



current
(1) Present activities or the latest version or
model.

(2) The flow of electrons within a wire or circuit,
measured in amps.

(3) (Current)  A Windows PIM from IBM that includes
a calendar, address book, phone dialer, outliner,
word processor and Gantt charts for project
tracking.  It was revised by its developer, Jensen-
Jones Inc., Red Bank, NJ, into a new package called
Commence.



current directory
The disk directory the system is presently working
in.  Unless otherwise specified, commands that deal
with disk files refer to the current directory.



current loop
A serial transmission method originating with
teletype machines that transmits 20 milliAmperes of
current for a 1 bit and no current for a 0 bit.
Today's circuit boards can't handle 20mA current
and use optical isolators at the receiving end to
detect lower current.  Contrast with RS-232.



current trends
See hot topics.



cursive writing
Handwriting.



cursor
(1) A movable symbol on screen that is the contact
point between the user and the data.  In text
systems, it is a blinking rectangle or underline.
On graphic systems, it is also called a pointer,
and it usually changes shape (arrow, square,
paintbrush, etc.) when it moves into a different
part of the screen.  See also database cursor.

(2) A pen-like or puck-like device used with a
digitizer tablet.  As the tablet cursor is moved
across the tablet, the screen cursor moves
correspondingly.  See digitizer tablet.



cursor keys
The keys that move the cursor on screen, which
include the up, down, left and right arrow, home,
end, PgUp and PgDn keys.  In addition to cursor
keys, a mouse or tablet cursor also moves the
cursor.



custom control
The functionality in an application that differs
from the stock objects provided in the development
system.  For example, a custom control is the
creation of an animated cursor or a unique style of
dialog box or menu, which is not part of the
standard system.



customer premises equipment
See CPE.



customized software
Software designed for an individual customer.



customized toolbar
A toolbar that can be custom configured by the
user.  Buttons can be added and deleted as
required.



cut & paste
To move or copy a block of text or graphics from
one document to another.  To perform the operation,
do the following: (1) Highlight the text or
graphics with the mouse and select Cut or Copy from
the EDIT menu, (2) switch to the receiving
document, (3) click in the location you want the
information to go into, and (4) select Paste from
the EDIT menu.



CUT mode
(Control Unit Terminal mode)  A mode that allows a
3270 terminal to have a single session with the
mainframe.  Micro to mainframe software emulates
this mode to communicate with the mainframe.
Contrast with DFT mode.



cut-through switch
A switching device that begins to output an
incoming data packet before the packet is
completely received.  Contrast with store-and-
forward switch.



CVF
(Compressed Volume File)  See DOS DoubleSpace.



CYBER
A family of computers from Control Data that ranged
from workstations to supercomputers.



cybernetics
The comparative study of human and machine
processes in order to understand their similarities
and differences.  It often refers to machines that
imitate human behavior.  See AI and robot.



cyberpunk
Relating to futuristic delinquency: hackers
breaking into computer banks, survival based on
high-tech wits.  Stems from science fiction novels
such as "Neuromancer" and "Shockwave Rider."



cyberspace
The term coined by William Gibson in his novel
"Neuromancer," to refer to a futuristic computer
network that people use by plugging their minds
into it!  The term has come to represent the
electronic superhighway that increasingly
interconnects around the world.  See Internet and
virtual reality.



cycle
(1) A single event that is repeated.  For example,
in a carrier frequency, one cycle is one complete
wave.

(2) A set of events that is repeated.  For example,
in a polling system, all of the attached terminals
are tested in one cycle.  See machine cycle and
memory cycle.



cycle stealing
A CPU design technique that periodically "grabs"
machine cycles from the main processor usually by
some peripheral control unit, such as a DMA (direct
memory access) device.  In this way, processing and
peripheral operations can be performed concurrently
or with some degree of overlap.



cycle time
The time interval between the start of one cycle
and the start of the next cycle.



cycles per second
The number of times an event or set of events is
repeated in a second.  See Hertz.



cyclical redundancy checking
See CRC.



Cycolor
A printing process from Mead Imaging that prints
full tonal images like photographs.  It uses a
special film coated with light-sensitive
microcapsules, called cyliths, that contain leuco
dyes.  The film is exposed to the color image that
is being printed, resulting in a latent image of
hard and soft cyliths.  The latent image donor film
is transferred onto a special Cycolor paper by
being squeezed together through pressure rollers,
thus releasing the dyes from the film onto the
paper.  The paper is then briefly heated, and the
result is a full-color image that resembles a
photograph.



cylinder
The aggregate of all tracks that reside in the same
location on every disk surface.  On multiple-
platter disks, the cylinder is the sum total of
every track with the same track number on every
surface.  On a floppy disk, a cylinder comprises
the top and corresponding bottom track.

   When storing data, the operating system fills an
entire cylinder before moving to the next one.  The
access arm remains stationary until all the tracks
in the cylinder have been read or written.



cylinder skew
The offset distance from the start of the last
track of the previous cylinder so that the head has
time to seek from cylinder to cylinder and be at
the start of the first track of the new cylinder.
See head skew.



D/A converter
(Digital to Analog Converter)  A device that
converts digital pulses into analog signals.
Contrast with A/D converter.  See DSP and ladder
DAC.



D/CAS
(Data/CASsette)  A tape backup technology that uses
an upgraded version of the common audio tape
cassette.  It can hold as much as 600MB of data.



D/DAT
See DATA/DAT.



D-RAM
See dynamic RAM.



D&B Software
(Dun & Bradstreet Software, Atlanta; The Dun &
Bradstreet Corporation)  A software and consulting
organization formed in 1990 as a merger of
Management Science America (MSA) and McCormack &
Dodge.  It is one of the largest software companies
in the world.

   MSA was originally founded in 1963 to provide
textile consulting services.  Under the leadership
of John Imlay, who rejoined the company in 1970 as
Chairman and CEO, MSA grew rapidly in business
applications software and was the first to enter
the international marketplace in 1979.

   McCormack & Dodge began as a packaged financial
software firm in 1969 and later introduced the
first integrated environment for mainframe business
applications.  In 1983, it was acquired by The Dun
& Bradstreet Corporation.

   Imlay directed the merger and headed the new
company in the development of client-server
versions of its mainframe software until his
retirement in 1993.



D4
A framing format for T1 transmission that places 12
T1 frames into a superframe.  See ESF.



DA
See desk accessory and data administrator.



DAC
(1) See D/A converter.

(2) (Discretionary Access Control)  A security
control that does not require clearance levels.
See NCSC.



DAD
(1) (Database Action Diagram)  Documentation that
describes the processing performed on data in a
database.

(2) (Digital Audio Disc)  Same as CD.



daemon
Pronounced "demon."  A UNIX program that executes
in the background ready to perform an operation
when required.  It is usually an unattended process
initiated at startup.  Typical daemons are print
spoolers and e-mail handlers or a scheduler that
starts up another process at a designated time.
The term comes from Greek mythology meaning
"guardian spirit."  Same as agent.



daisy chain
Connected in series, one after the other.
Transmitted signals go to the first device, then to
the second and so on.

           ĿĿĿ
               

                 Daisy chain





daisy wheel
A print mechanism that uses a plastic or metal hub
with spokes like an old-fashioned wagon wheel minus
the outer rim.  At the end of each spoke is the
carved image of a type character.

   When the required character spins around to the
print hammer, the image is banged into a ribbon and
onto paper.  The mechanism is then moved to the
next location.  Daisy wheel printers print
typewriter-like quality from 10 to 75 cps and have
been superseded by dot matrix and laser printers.



DAL
(Data Access Language)  A database interface from
Apple that allows the Mac to access DAL-supported
databases on Macs or non-Apple computers.  It is a
superset of SQL.  Database vendors license the
specs and translate DAL calls to their database
engines.



damping
A technique for stabilizing an electronic or
mechanical device by eliminating unwanted or
excessive oscillations.



dark current
The current that flows in a photodetector when it
is not receiving any light.  It may increase as the
temperature rises.



dark fiber
Unused transmission capacity in a fiber optic
trunk.



Darlington circuit
An amplification circuit that uses two transistors
coupled together.



DARPA
(Defense Advanced Research Projects Agency)  See
ARPANET.



DAS
See FDDI.



DASD
(Direct Access Storage Device)  Pronounced
"dazdee."  A peripheral device that is directly
addressable, such as a disk or drum.  The term is
used in the mainframe world.



DAT
(1) (Digital Audio Tape)  A CD-quality, digital
recording technology for magnetic tape.  A 4mm
helical-scan DAT drive holds several gigabytes with
extended-length tapes when adapted for data storage
use.  See tape backup.

(2) (Dynamic Address Translator)  A hardware
circuit that converts a virtual memory address into
a real address.



data
(1) Technically, raw facts and figures, such as
orders and payments, which are processed into
information, such as balance due and quantity on
hand.  However, in common usage, the terms data and
information are used synonymously.

   The amount of data versus information kept in
the computer is a tradeoff.  Data can be processed
into different forms of information, but it takes
time to sort and sum transactions.  Up-to-date
information can provide instant answers.

   A common misconception is that software is also
data.  Software is executed, or run, by the
computer.  Data is "processed."  Software is "run."

(2) Any form of information whether in paper or
electronic form.  In electronic form, data refers
to files and databases, text documents, images and
digitally-encoded voice and video.

(3) The plural form of datum.



data abstraction
In object-oriented programming, creating user-
defined data types that contain their own data and
processing.  These data structures, or objects, are
unaware of each other's physical details and know
only what services each other performs.  This is
the basis for polymorphism and information hiding.



Data Access Language
See DAL.



data acquisition
(1) The automatic collection of data from sensors
and readers in a factory, laboratory, medical or
scientific environment.

(2) The gathering of source data for data entry
into the computer.



data administration
The analysis, classification and maintenance of an
organization's data and data relationships.  It
includes the development of data models and data
dictionaries, which, combined with transaction
volume, are the raw materials for database design.

   Database administration often falls within the
jurisdiction of data administration; however, data
administration functions provide the overall
management of data as an organizational resource.
Database administration is the technical design and
management of the database.


                  Data Is Complex
The flow of data/information within a company is
complex since the same data is viewed differently
as it moves from one department to the other.

   For example: When a customer places an order,
the order becomes a commission for sales, a
statistic for marketing, an order to keep track of
in order processing, an effect on cash flow for
financial officers, picking schedules for the
warehouse, and production scheduling for
manufacturing.

   Users have different requirements for
interrogating and updating data.  Operations people
need detail, management needs summaries.  Database
design must take this into consideration.



data administrator
A person who coordinates activities within the data
administration department.  Contrast with database
administrator.



data bank
Any electronic depository of data.



data base
See database.



data bases
See online services.



data bits
The number of bits used to represent one character
of data.  When transmitting ASCII text via modem,
either seven or eight bits may be used.  Most other
forms of data require eight bits.



data bus
An internal pathway across which data is
transferred to and from the processor.  The
expansion slots in personal computers are connected
to the data bus.



data carrier
(1) Any medium such as a disk or tape that can hold
machine readable data.

(2) A carrier frequency into which data is
modulated for transmission in a network.



data cartridge
A removable magnetic tape module driven by a wheel
inside the drive that presses against a passive
roller in the cartridge.  A tension belt is
attached to the roller that presses against the
supply and takeup reel.  See QIC.



data cassette
An audio cassette made to higher tolerances for
data storage.



Data Cell
An IBM mass storage device (1960s) that used tape
strips selected out of a cartridge and wrapped
around a rotating drum for reading.  See RACE and
CRAM.



data circuit-terminating equipment
See DCE.



data code
(1) A digital coding system for data in a computer.
See ASCII and EBCDIC.

(2) A coding system used to abbreviate data; for
example, codes for regions, classes, products and
status.



data collection
Acquiring source documents for the data entry
department.  It comes under the jurisdiction of the
data control or data entry department.  See data
acquisition.



data communications
Same as communications.



data communications equipment
See DCE.



data compression
Encoding data to take up less storage space.  For
example, short names in fixed length fields waste a
lot of space.  A simple method called run length
encoding converts the spaces into a code that
indicates how many blanks follow.

   There are two major methods used for data
compression: statistical and dictionary, and two
widely-used examples of each: Huffman coding and
LZW (Lempel-Ziv-Welch).

   Text files can be compressed the most; for
example, the text you're reading can be compressed
from 50 to 70% depending on method used.  Dense
machine language files compress about a third to a
half.  Some graphics files leave little room for
compaction, others compress well.  See Pkzip abc's.



data control department
The function responsible for collecting data for
input into a computer's batch processing operations
as well as the dissemination of the finished
reports.  The data entry department may be under
the jursidiction of the data control department or
vice versa.



DATA/DAT
(DATA/Digital Audio Tape)  A DAT format for data
backup that can be divided into as many as 254
partitions allowing for updating in place.  See
tape backup.



data declaration
Same as data definition (1).



data definition
(1) In a source language program, the definitions
of data structures (variables, arrays, fields,
records, etc.).

(2) A description of the record layout in a file
system or DBMS.



data description language
See DDL.



data dictionary
A database about data and databases.  It holds the
name, type, range of values, source, and
authorization for access for each data element in
the organization's files and databases.  It also
indicates which application programs use that data
so that when a change in a data structure is
contemplated, a list of affected programs can be
generated.

   The data dictionary may be a stand-alone system
or an integral part of the DBMS.  Data integrity
and accuracy is better ensured in the latter case.



data dipper
Software in a personal computer that queries a
mainframe database.



data division
The part of a COBOL program that defines the data
files and record layouts.



data element
The fundamental data structure in a data processing
system.  Any unit of data defined for processing is
a data element; for example, ACCOUNT NUMBER, NAME,
ADDRESS and CITY.  A data element is defined by
size (in characters) and type (alphanumeric,
numeric only, true/false, date, etc.).  A specific
set of values or range of values may also be part
of the definition.

   Technically, a data element is a logical
definition of data, whereas a field is the physical
unit of storage in a record.  For example, the data
element ACCOUNT NUMBER, which exists only once, is
stored in the ACCOUNT NUMBER field in the customer
record and in the ACCOUNT NUMBER field in the order
records.

   Data element, data item, field and variable all
describe the same unit of data and are used
interchangeably.



data encryption
See encryption, DES and RSA.



data entry
Entering data into the computer, which includes
keyboard entry, scanning and voice recognition.
When transactions are entered after the fact (batch
data entry), they are just stacks of source
documents to the keyboard operator.  Deciphering
poor handwriting from a source document is a
judgment call that is often error prone.  In online
data entry operations, in which the operator takes
information in person or by phone, there's
interaction and involvement with the transaction
and less chance for error.



data entry department
The part of the datacenter where the data entry
terminals and operators are located.



data entry operator
A person who enters data into the computer via
keyboard or other reading or scanning device.



data entry program
An application program that accepts data from the
keyboard or other input device and stores it in the
computer.  It may be part of an application that
also provides updating, querying and reporting.

   The data entry program establishes the data in
the database and should test for all possible input
errors.  See validity checking, table lookup, check
digit and intelligent database.



data error
A condition in which data on a digital medium has
been corrupted.  The error can be as little as one
bit.

   In DOS, the message "Data error on drive x"
means that an area of the disk is unreadable.
Press R to retry.  Most likely, you'll have to
press A to stop (abort).  If the data or program is
critical and there's no backup, use a utility
program to try to reconstruct the damaged area.
See DOS Recover.



data file
A collection of data records.  This term may refer
specifically to a database file that contains
records and fields in contrast to other files such
as a word processing document or spreadsheet.  Or,
it may refer to a file that contains any type of
information structure including documents and
spreadsheets in contrast to a program file.



data flow
(1) In computers, the path of data from source
document to data entry to processing to final
reports.  Data changes format and sequence (within
a file) as it moves from program to program.

(2) In communications, the path taken by a message
from origination to destination and includes all
nodes through which the data travels.



data flow diagram
A description of data and the manual and machine
processing performed on the data.



data fork
The part of a Macintosh file that contains data.
For example, in a HyperCard stack, text, graphics
and HyperTalk scripts reside in the data fork,
while fonts, sounds, control information and
external functions reside in the resource fork.



data format
Same as file format.



Data General
(Data General Corporation, Westboro, MA)  A
computer manufacturer founded in 1968 by Edson de
Castro.  In 1969, it introduced the Nova, the first
16-bit mini with four accumulators, a leading
technology at the time.  During its early years,
the company was successful in the scientific,
academic and OEM markets.  With its 32-bit ECLIPSE
family of computers and its Comprehensive
Electronic Office (CEO) software, Data General
gained entry into the commercial marketplace in the
early 1980s.

   In 1989, the company introduced its AViiON line
of UNIX-based servers that use the Motorola 88000
CPU, and more powerful models continue to be
introduced.  Data General's CLARiiON line of fault-
tolerant (RAID) storage systems, introduced in
1992, are available for UNIX-based IBM and Sun
computer systems.

   The "Eagle project," DG's development of its
ECLIPSE and first 32-bit computer, was chronicled
in Tracy Kidder's Pulitzer-prize winning novel,
"Soul of a New Machine," published by Little, Brown
and Company, ISBN 0-316-49170-5.



data glove
A glove used to report the position of a user's
hand and fingers to a computer.  See virtual
reality.



data independence
A DBMS technique that separates data from the
processing and allows the database to be
structurally changed without affecting most
existing programs.  Programs access data in a DBMS
by field and are concerned with only the data
fields they use, not the format of the complete
record.  Thus, when the record layout is updated
(fields added, deleted or changed in size), the
only programs that must be changed are those that
use those new fields.



data integrity
The process of preventing accidental erasure or
adulteration in a database.



Data Interchange Format
See DIF.



data item
A unit of data stored in a field.  See field.



data library
The section of the datacenter that houses offline
disks and tapes.  Data library personnel are
responsible for cataloging and maintaining the
media.



data line
An individual circuit, or line, that carries data
within a computer or communications channel.



data line monitor
In communications, a test instrument that analyzes
the signals and timing of a communications line.
It either visually displays the patterns or stores
the activity for further analysis.



data link
In communications, the physical interconnection
between two points (OSI layers 1 and 2).  It may
also refer to the modems, protocols and all
required hardware and software to perform the
transmission.



data link escape
A communications control character which indicates
that the following character is not data, but a
control code.



data link protocol
In communications, the transmission of a unit of
data from one node to another (OSI layer 2).  It is
responsible for ensuring that the bits received are
the same as the bits sent.  Following are the major
categories:

             Asynchronous Transmission
Originating from mechanical teletype machines,
asynchronous transmission treats each character as
a unit with start and stop bits appended to it.  It
is the common form of transmission between the
serial port of a personal computer or terminal and
a modem.  ASCII, or teletype, protocols provide
little or no error checking.  Zmodem and
CompuServe's B protocol are widely-used file
transfer protocols that provide error checking and
data link services.


             Synchronous Transmission
Developed for mainframe networks using higher
speeds than teletype terminals, synchronous
transmission sends contiguous blocks of data, with
both sending and receiving stations synchronized to
each other.  Synchronous protocols include error
checking.  Examples are IBM's SDLC, Digital's
DDCMP, and the international HDLC.


                       LANs
Developed for medium to high transmission speeds
between stations, LANs typically use collision
detection (CSMA/CD) or token passing methods for
transmitting data between nodes.  Examples are
IBM's Token Ring, Datapoint's ARCNET, Xerox's
Ethernet and AT&T's Starlan.

   The IEEE 802 specification for LANs breaks the
data link layer into two sublayers: the LLC
(Logical Link Control) and MAC (Media Access
Control).  The LLC provides a common interface
point to the MAC layers, which specify the access
method used.  The following compares the data link
layer in LANs to IBM's SNA and ISO's OSI model.


       Path       
       Control    Network 
  Ĵ  Ĵ  Ŀ
 Data                             LLC       
 Link   SDLC       HDLC     Ĵ
 Layer                       MAC (CSMA/CD,  
  Ĵ  Ĵ  Ŀ Token Bus,
                                 Token Ring
                                Ĵ
       Physical   Physical      Physical    
          
          SNA          OSI           IEEE 802





data management
Refers to several levels of managing data.  From
bottom to top, they are:

(1) The part of the operating system that manages
the physical storage and retrieval of data on a
disk or other device.  See access method.

(2) Software that allows for the creation, storage,
retrieval and manipulation of files interactively
at a terminal or personal computer.  See file
manager and DBMS.

(3) The function that manages data as an
organizational resource.  See data administration.

(4) The management of all data/information in an
organization.  It includes data administration, the
standards for defining data and the way in which
people perceive and use it.



data management system
See DBMS.



data manipulation
Processing data.



data manipulation language
A language that requests data from a DBMS.  It is
coded within the application program such as COBOL
or C.



data model
A description of the organization of a database.
It is often created as an entity relationship
diagram.  Modeling tools, such as Logic Works'
ERwin (Entity Relationship for Windows), are used
to graphically design the model and automatically
generate the SQL code that defines the data schema
in the database.



data modeling
Creating the description of the organization of the
database.



data modem
A modem used for sending data and not faxes.  See
modem and fax/modem.



data module
A sealed, removable storage module containing
magnetic disks and their associated access arms and
read/write heads.



data name
The name assigned to a field or variable.



data network
A communications network that transmits data.  See
communications.



data packet
One frame in a packet-switched message.  Most data
communications is based on dividing the transmitted
message into packets.  For example, an Ethernet
packet can be from 64 to 1518 bytes in length.



data parallel
Same as SIMD.



data processing
The capturing, storing, updating and retrieving
data and information.  It may refer to the industry
or to data processing tasks in contrast with other
operations, such as word processing.



Data Processing Management Association
See DPMA.



data processor
(1) A person who works in data processing.

(2) A computer that is processing data, in contrast
with a computer performing another task, such as
controlling a network.



data projector
A video machine that projects output from a
computer onto a remote screen.  It is bulkier than
a flat LCD panel, but is faster for displaying
high-speed animation.



Data Propagator
An IBM query language that maintains consistency
between DB2 and IMS/ESA DB databases.  When data is
changed in the IMS database, it is automatically
changed in the DB2 database.



data pump
A circuit that transmits pulses in a digital
device.  It typically refers to the chipset in a
modem that generates the bits based on the modem's
modulation techniques.



data rate
(1) The data transfer speed within the computer or
between a peripheral and computer.

(2) The data transmission speed in a network.



data recovery
Restoring data that has been physically damaged or
corrupted on a disk or tape.  Disks and tapes can
become corrupted due to viruses, bad software,
hardware failure as well as from power failures
that occur while the magnetic media is being
written.  See DOS data recovery.



data representation
How data types are structured; for example, how
signs are represented in numerical values or how
strings are formatted (enclosed in quotes,
terminated with a null, etc.).



data resource management
Same as data administration.



data set
(1) A data file or collection of interrelated data.

(2) The AT&T name for modem.



data set ready
See DSR.



data sheet
A page or two of detailed information about a
product.



data signal
Physical data as it travels over a line or channel
(pulses or vibrations of electricity or light).



data sink
A device or part of the computer that receives
data.



data source
A device or part of the computer in which data is
originated.



data stream
The continuous flow of data from one place to
another.



data striping
See disk striping.



data structure
The physical layout of data.  Data fields, memo
fields, fixed length fields, variable length
fields, records, word processing documents,
spreadsheets, data files, database files and
indexes are all examples of data structures.



data switch
A switch box that routes one line to another; for
example, to connect two computers to one printer.
Manual switches have dials or buttons.  Automatic
switches test for signals and provide first-come,
first-served switching.



data system
Same as information system.



data tablet
Same as digitizer tablet.



data terminal ready
See DTR.



data terminating equipment
See DTE.



data transfer
The movement of data within the computer system.
Typically, data is said to be transferred within
the computer, but it is "transmitted" over a
communications network.  A transfer is actually a
copy function since the data is not automatically
erased at the source.



data transfer rate
Same as data rate.



data transmission
Sending data over a communications network.



data transparency
The ability to easily access and work with data no
matter where it is located or what application
created it.



data type
A category of data.  Typical data types are
numeric, alphanumeric (character), dates and
logical (true/false).  Programming languages allow
for the creation of different data types.

   When data is assigned a type, it cannot be
treated like another type.  For example,
alphanumeric data cannot be calculated, and digits
within numeric data cannot be isolated.  Date types
can only contain valid dates.



data warehouse
A database designed to support decision making in
an organization.  It is batch updated and
structured for fast queries and summaries.  See
OLAP database, DSS and EIS.



data word
See word.



database
(1) A set of interrelated files that is created and
managed by a DBMS.

(2) Any electronically-stored collection of data.



DATABASE 2
See DB2.



database administrator
A person responsible for the physical design and
management of the database and for the evaluation,
selection and implementation of the DBMS.

   In small organizations, the database
administrator and data administrator are one in the
same; however, when the two responsibilities are
managed separately, the database administrator's
function is more technical.



database analyst
See data administrator and database administrator.



database cursor
A record pointer in a database.  When a database
file is selected and the cursor is opened, the
cursor points to the first record in the file.
Using various commands, the cursor can be moved
forward, backward, to top of file, bottom of file
and so forth.



database designer
See data administrator and database administrator.



database driver
A software routine that accesses a database.  It
allows an application or compiler to access a
particular database format.



database engine
Same as database manager.



database machine
A computer system designed for database access.
Database machines never caught on until the early
1990s when massively parallel processors (MPPs)
from companies such as Teradata, now part of AT&T,
nCube, Thinking Machines and Kendall Square
Research, proved the concept.  Using hundreds and
even thousands of microprocessors with database
software designed for parallelism, database
machines can scan large files much faster than a
mainframe.

   Dramatic performance increases have been
documented.  For example, a large financial
organization reduced 30 days worth of month-end
analysis and reporting to a single day.  In other
cases, queries have been speeded up by a factor of
100.  Database machines using MPP architecture are
expected to grow in popularity for decision support
systems in large organizations.



database management system
See DBMS.



database manager
(1) With personal computers, software that allows a
user to manage multiple data files (same as DBMS).
Contrast with file manager, which works with one
file at a time.

(2) Software that provides database management
capability for traditional programming languages,
such as COBOL, BASIC and C, but without the
interactive capabilities.

(3) The part of the DBMS that stores and retrieves
the data.



database program
A software application that allows for the
management of data and information structured as
fields, records and files.  Database programs
provide a way of creating and manipulating the
electronic equivalent of a name and address card
that can hold large amounts of information.

   Because all data is structured into a one record
per subject or transaction format, it allows for
powerful query capabilities, in which you can
select records based on any of their content.  A
database program is the heart of a business
information system and provides mainly file
creation, data entry, update, query and reporting
functions.

   The traditional term for a database program is a
database management system (DBMS).  It is also
called a data management system.  For more details
on the features of a DBMS, see DBMS.  Also see
application software for a breakdown of all major
software applications.


     User Interaction with a Database Program
The database programs available on personal
computers let you perform all the following tasks
interactively on one file at a time.  However, as
soon as you want data in one file to automatically
update another, programming has to be done.  That's
where the faint of heart take their leave, and the
hackers take over.  Following are the common tasks
you need to perform to create and work with a
database file.

CREATE A FILE AND SET THE INDEX ORDER
Each field in a record is defined by name, type and
length.  In order to keep the file in sequence, one
or more fields are defined as key fields, upon
which indexes are created and maintained.  The
index is updated whenever new records are added or
existing records are deleted or any data in a key
field changes.

CREATE DATA ENTRY FORMS
Data entry is accomplished by designing a form to
display each record.  Data entry forms contain
field validation.  You decide what data can go in
and what must stay out of these fields.

UPDATE/EDIT
In a single-user, one-file-at-a-time application,
there is nothing to predefine here.  Changing data
is just a matter of opening the file and selecting
the EDIT mode.  However, in a multiuser system,
security must be administered and audit trails must
be programmed.

VIEW/QUERY
You can browse an entire file or just selected
records.  Selected records are usually created as a
temporary file that can be saved or abandoned.  The
temporary file may be sorted into a new sequence if
desired.

   The ease with which a query can be composed
determines how much users will ask their own
questions or rely on their IS staff to create them.
Getting data from two files; for example, customers
and orders, or vendors and purchases, requires
knowledge of how to link the files for the query.
Most database programs have a JOIN function, which
creates a new file with data from two existing
files.  Once a query description has been composed,
it can be saved for use again.

REPORT
Reports provide details and summaries in a more
elaborate fashion than queries.  They have page and
column headers and can be sorted into order by
multiple fields; for example, county within city
within state.  Once a report description has been
composed, it can be saved for use again.

MODIFY STRUCTURE
From time to time, it is necessary to add or delete
fields, change their lengths or possibly their
names.  This function is similar to creating the
record structure in the first place, except that
you are editing the structure rather than defining
it from scratch.





database publishing
Using desktop publishing to produce reports of
database contents.



database server
A computer in a LAN dedicated to database storage
and retrieval.  The database server is a key
component in a client/server environment.  It holds
the database management system (DBMS) and the
databases.  Upon requests from the client machines,
it searches the database for selected records and
passes them back over the network.

   A database server and file server may be one in
the same, because a file server often provides
database services.  However, the term implies that
the system is dedicated for database use only and
not a central storage facility for applications and
files.  See client/server.



database trigger
See trigger.



databases
See online services.



datacenter
The department that houses the computer systems and
related equipment, including the data library. 
Data entry and systems programming may also come
under its jurisdiction.  A control section is
usually provided that accepts work from and
releases output to user departments.



datacom
(DATA COMmunications)  See communications and CA-
DATACOM/DB.



DataEase
A relational DBMS for PCs from DataEase
International, Inc., Trumbull, CT.  It provides a
menu-driven interface for developing applications
without programming and is noted for its ease of
use.



datagram
A TCP/IP message unit that contains internet source
and destination addresses and data.



DataPhone
An AT&T trade name for equipment and services.  See
DDS.



date math
Calculations made upon dates.  For example, March
30 + 5 yields April 4.



datum
The singular form of data; for example, one datum.
It is rarely used, and data, its plural form, is
commonly used for both singular and plural.



daughter board
A small printed circuit board that is attached to
or plugs into a removable printed circuit board.



dazdee
See DASD.



DB
See database and decibel.



DB-9, DB-15, DB-25..
(DB-9, DB-15, DB-25, DB-37, DB-50)  A category of
plugs and sockets with 9, 15, 25, 37 and 50 pins
respectively, used to hook up communications and
computer devices.  The DB refers to the physical
structure of the connector, not the purpose of each
line.

   DB-9 and DB-25 connectors are commonly used for
RS-232 interfaces.  The DB-25 is also used on the
computer end of the parallel printer cable for PCs
(the printer end is a Centronics 36-pin connector).

   A high-density DB-15 connector is used for the
VGA port on a PC, which has 15 pins in the same
shell as the DB-9 connector.



DB/DC
(DataBase/Data Communications)  Refers to software
that performs database and data communications
functions.



DB2
(DATABASE 2)  A relational DBMS from IBM that was
originally developed for its mainframes.  It is a
full-featured SQL language DBMS that has become
IBM's major database product.  Known for its
industrial strength reliability, IBM is making DB/2
available for all of its own platforms as well as
non-IBM platforms, including the HP 9000, Sun
Solaris and Windows NT.



DB2/2
The OS/2 version of DB2 from IBM.  It is a 32-bit
DBMS that is compatible with the mainframe DB2.  It
replaces OS/2's 16-bit Database Manager.

   DB2/400 is the AS/400 version, and DB2/6000 is
the RS/6000 version.



DBA
See database administrator.



dBASE
A relational database management (DBMS) and
application development system for DOS and Windows
from Borland.  dBASE is the most widely-used
database program, and its file formats have become
de facto standards.  With dBASE for Windows, dBASE
has become a client/server development system with
the inclusion of the Borland Database Engine.
dBASE has automatic links to the Engine's IDAPI
interface, allowing dBASE applications to access
remote database servers (see Borland Database
Engine).

   dBASE provides a Pascal-like, interpreted
programming language and fourth-generation commands
for interactive use.  The following dBASE 3GL
example converts Fahrenheit to Celsius:

    INPUT "Enter Fahrenheit  " TO FAHR
    ? "Celsius is ", (FAHR - 32) * 5 / 9


The following dBASE 4GL example opens the product
file and displays green items:

    use products
    list for color ='GREEN' 



                EVOLUTION OF dBASE
dBASE II was the first comprehensive relational
DBMS for personal computers.  Originally named
Vulcan, dBASE II was created by Wayne Ratliff to
manage a company football pool.  It was modeled
after JPLDIS, the DBMS at Jet Propulsion Labs in
Los Angeles.

   Renamed dBASE II when Hal Lashlee and George
Tate formed Ashton-Tate to market it (Ashton-Tate
was acquired by Borland in 1991), dBASE became a
huge success within a couple of years.

   dBASE spawned the "Xbase" industry, which
includes Clipper, FoxBase, FoxPro and other
products that provide a dBASE-like programming
language and support the dBASE file formats.

                     dBASE II
Introduced in 1981, it was the original command-
driven dBASE for CP/M machines and later for PCs.
dBASE II data formats and programs must be
converted to run under dBASE III.

             dBASE III/dBASE III PLUS
Introduced in 1984, dBASE III was a major upgrade
of dBASE II for PCs only.  It added menus, more
programming commands and handled larger databases.
A memo field was included.  In 1986, dBASE III PLUS
introduced new menus and features, including the
ability to store queries and relational views.

                     dBASE IV
Introduced in 1988, it is a major upgrade of dBASE
III PLUS with redesigned menus, screens and
reports.  It adds a QBE method for asking questions
as well as an SQL language interface.  Many new
programming commands and features are added,
including arrays and windows.

   Versions of dBASE IV are also available for UNIX
on 386s, Sun workstations and VAXs under VMS, and a
runtime version is available for the Macintosh.

                 dBASE for Windows
Introduced in 1994, dBASE 5.0 for Windows adds
objects and visual programming to dBASE and
provides connectivity to a variety of SQL databases
using the Borland Database Engine.  It runs dBASE
III and dBASE IV DOS applications in a
compatibility window, and its Component Builder
converts DOS screen and report formats into dBASE
for Windows files.  See Borland Database Engine.





dBASE compiler
Software that converts dBASE source language into
machine language.  The resulting programs execute
on their own like COBOL or C programs and do not
run under dBASE.  See CA-Clipper, Force and
Quicksilver.



dBASE Mac
A Macintosh DBMS from Ashton-Tate that never caught
on because it was incompatible with dBASE.



DBF file
The dBASE data file extension.  dBASE II and dBASE
III files both use DBF, but are not compatible.



DBMS
(DataBase Management System)  Software that
controls the organization, storage, retrieval,
security and integrity of data in a database.  It
accepts requests from the application and instructs
the operating system to transfer the appropriate
data.

   DBMSs may work with traditional programming
languages (COBOL, C, etc.) or they may include
their own programming language for application
development.

   DBMSs let information systems be changed more
easily as the organization's requirements change.
New categories of data can be added to the database
without disruption to the existing system.  Adding
a field to a record does not require changing any
of the programs that do not use the data in that
new field.


             MAJOR FEATURES OF A DBMS

                   Data Security
The DBMS can prevent unauthorized users from
viewing or updating the database.  Using passwords,
users are allowed access to the entire database or
subsets of it called subschemas.  For example, in
an employee database, some users may be able to
view salaries while others may view only work
history and medical data.

                  Data Integrity
The DBMS can ensure that no more than one user can
update the same record at the same time.  It can
keep duplicate records out of the database; for
example, no two customers with the same customer
number can be entered.

                 Interactive Query
Most DBMSs provide query languages and report
writers that let users interactively interrogate
the database and analyze its data.  This important
feature gives users access to all management
information as needed.

        Interactive Data Entry and Updating
Many DBMSs provide a way to interactively enter and
edit data, allowing you to manage your own files
and databases.  However, interactive operation does
not leave an audit trail and does not provide the
controls necessary in a large organization.  These
controls must be programmed into the data entry and
update programs of the application.

   This is a common misconception about personal
computer DBMSs.  Complex business systems can be
developed in dBASE and Paradox, etc., but not
without programming.  This is not the same as
creating lists of data for your own record keeping.

                 Data Independence
With DBMSs, the details of the data structure are
not stated in each application program.  The
program asks the DBMS for data by field name; for
example, a coded equivalent of "give me customer
name and balance due" would be sent to the DBMS.
Without a DBMS, the programmer must reserve space
for the full structure of the record in the
program.  Any change in data structure requires
changing all application programs.


                  DATABASE DESIGN
A business information system is made up of
subjects (customers, employees, vendors, etc.) and
activities (orders, payments, purchases, etc.).
Database design is the process of organizing this
data into related record types.  The DBMS that is
chosen is the one that can support the
organization's data structure while efficiently
processing the transaction volume.

   Organizations may use one kind of DBMS for daily
transaction processing and then move the detail to
another DBMS better suited for random inquiries and
analysis.

   Overall systems design decisions are performed
by data administrators and systems analysts.
Detailed database design is performed by database
administrators.


  HIERARCHICAL, NETWORK AND RELATIONAL DATABASES
Information systems are made up of related files:
customers and orders, vendors and purchases, etc.
A key DBMS feature is its ability to manage these
relationships.

   Hierarchical databases link records like an
organization chart.  A record type can be owned by
only one owner.  In the following example, orders
are owned by only one customer.  Hierarchical
structures were widely used with early mainframe
systems; however, they are often restrictive in
linking real-world structures.

     Ŀ
        Customer   
     
                 
               Ŀ
                   Order    
               


In network databases, a record type can have
multiple owners.  In the example below, orders are
owned by both customers and products, reflecting
their natural relationship in business.

     Ŀ   Ŀ
        Customer         Product   
        
                          
               Ŀ
                   Order    
               


Relational databases do not link records together
physically, but the design of the records must
provide a common field, such as account number, to
allow for matching.  Often, the fields used for
matching are indexed in order to speed up the
process.

   In the following example, customers, orders and
products are linked by comparing data fields and/or
indexes when information from more than one record
type is needed.  This method is more flexible for
ad hoc inquiries.  Many hierarchical and network
DBMSs also provide this capability.

Ŀ  Ŀ  Ŀ
  Customer        Order         Product   
    


               INTELLIGENT DATABASES
All DBMSs provide some data validation; for
example, they can reject invalid dates or
alphabetic data entered into money fields.  But
most validation is left up to the application
programs.

   Intelligent databases provide more validation;
for example, table lookups can reject bad spelling
or coding of items.  Common algorithms can also be
used such as one that computes sales tax for an
order based on zip code.

   When validation is left up to each application
program, one program could allow an item to be
entered while another program rejects it.  Data
integrity is better served when data validation is
done in only one place.  Mainframe DBMSs are
increasingly becoming intelligent.  Eventually all
DBMS will follow suit.


               MULTIMEDIA DATABASES
The world of information is made up of data, text,
pictures and voice.  Many DBMSs manage text as well
as data, but very few manage both with equal
proficiency.  Throughout the 1990s, DBMSs will
begin to integrate all forms of information.
Eventually, it will be common for a database to
handle data, text, graphics, voice and video with
the same ease as today's systems handle data.

   The relational DBMS is not suited to storing
multimedia data, because there are so many
different types of sound and video formats.
Although a relational DBMS may provide a BLOB
(binary large object) field that holds anything,
extensive use of this field can strain the
processing.

   An object-oriented database is often better
suited for multimedia.  Using the object model, an
object-oriented DBMS can store anything or refer to
anything.  For example, a video object can
reference a video file stored elsewhere on some
other hard disk and launch the video player
software necessary to play it.



  to/from terminals (RAM)ͻ
 Ŀ   Ŀ   
  Comm.      TP Monitor (Multiuser)      
  Access        
  Methods       Ŀ Ŀ 
 Ĵ      Application Application  
                in COBOL or in DBMS's    
                other lang. own language 
                  
    OS    -DBMS--DBMSĿ
          Ŀ   Ŀ 
          Interactive:     Interpreter 
          enter, edit,      
          query, reports                
 Ĵ                
  Disk      Ŀ
  Access         Database manager       
  Methods   ٳ
 -DBMS-DBMSٺ
  to/from disk ͼ

          System and Application Software
                Running in Memory

The diagram above shows the interaction of the DBMS
with other system and application software running
in memory.





DBOMP
(DataBase Organization and Maintenance Processor) 
An early DBMS that was derived from BOMP.



DBS
(Direct Broadcast Satellite)  A one-way TV
broadcast service direct from a satellite to a
small 18" dish antenna.  Although DBS service
exists in other countries, the first DBS satellite
for the United States was launched in December 1993
by Hughes Communications and Hubbard Broadcasting
with a combined investment of $1 billion.

   The Hughes DirecTv subsidiary will use 11 of the
16 transponders and Hubbard's U.S. Satellite
Broadcasting will use five.  Transmission is a
highly-compressed digital signal.



dBXL
A dBASE III PLUS-compatible DBMS from WordTech
Systems, Inc., Orinda, CA, that features a menu-
driven option for interactive use.  See Arago.



DC
(1) (Direct Current)  An electrical current that
travels in one direction and used within the
computer's electronic circuits.  Contrast with AC.

(2) (Data Communications)  See DB/DC.



DC/OSx
(DataCenter/OSx)  Pyramid Technology's UNIX
operating system that runs on its Nile series of
SMP machines.  DC/OSx is the first SMP
implementation on UNIX System V Release 4.



DC2000
See QIC.



DCA
(1) (Document Content Architecture)  IBM file
formats for text documents.  DCA/RFT (Revisable-
Form Text) is the primary format and can be edited.
DCA/FFT (Final-Form Text) has been formatted for a
particular output device and cannot be changed.
For example, page numbers, headers and footers are
placed on every page.

(2) (Distributed Communications Architecture)  A
network architecture from Unisys.

(3) (Digital Communications Associates, Inc.,
Alpharetta, GA)  Manufacturer of communications
products.  See Irma board.



DCC
(1) (Digital Compact Cassette)  A digital tape
format that uses a variation of the common analog
audio cassette.  DCC tape players also play analog
tape cassettes.

(2) (Distributed Call Center)  An automatic call
distribution (ACD) system from Teloquent
Communications, Billerica, MA, that runs on
standard PCs and uses public ISDN lines.



DCE
(1) (Data Communications Equipment or Data Circuit-
terminating Equipment)  A device that establishes,
maintains and terminates a session on a network.
It may also convert signals for transmission.  It
is typically the modem.  Contrast with DTE.

(2) (Distributed Computing Environment)  See OSF.



DCI
(Display Control Interface)  An Intel and Microsoft
standard for full-motion video in Windows.  It
improves performance by bypassing the Windows GDI
interface and addressing the display adapter
directly.  It requires updated drivers from the
adapter vendor and the DCI DLL from Microsoft.  DCI
is a revision of Intel's VDI specification.



DCL
(1) (Digital Command Language)  Digital's standard
command language for the VMS operating system on
its VAX series.

(2) (Data Compression Library)  A set of
compression routines that allow realtime
compression and decompression of data.  See PK
software.

(3) (Data Control Language)  A language used to
gain access to or manage a database.



DCS
(1) (Distributed Communications System)  A
telephone system that puts small switches close to
subscribers making local loops shorter and
maximizing long lines to the central office.

(2) (Distributed Control System)  A process control
system that uses disbursed computers throughout the
manufacturing line for control.

(3) (Digital Cross-connect System)  A high-speed
data channel switch that accepts separate
instructions for switching independently of the
data travelling through it.

(4) (Document Control Software)  A menu-driven
query system from Workgroup Technologies for Oracle
databases on PCs and Sun stations.

(5) (Desktop Color Separation)  The QuarkXpress
format for defining color separated output from a
personal computer.



DCT
(Discrete Cosine Transform)  An algorithm, similar
to Fast Fourier Transform, that converts data
(pixels, waveforms, etc.) into sets of frequencies.
The first frequencies in the set are the most
meaningful; the latter, the least.  For
compression, latter frequencies are stripped away
based on allowable resolution loss.  The DCT method
is used in the JPEG and MPEG compression.



DD
(Double Density)  The designation for low-density
diskettes, typically the 5.25" 360K and 3.5" 720K
floppies.  See double density.  Contrast with HD.



DDBMS
(Distributed Database Management System)  See
distributed database.



DDC
See VESA Display Data Channel.



DDCMP
(Digital Data Communications Message Protocol)
Digital's proprietary, synchronous data link
protocol used in DECnet.



DDE
(Dynamic Data Exchange)  A message protocol in
Windows that allows application programs to request
and exchange data between them automatically.



DDL
(1) (Data Description Language)  A language used to
define data and their relationships to other data.
It is used to create the data structure in a
database.  Major database management systems
(DBMSs) use a SQL data description language.

(2) (Document Description Language)  A printer
control language from Imagen that runs on the HP
LaserJet series.

(3) (Direct Data Link)  The ability of a supplier
to directly interrogate a customer's inventory
database in order to manage scheduling and shipping
more efficiently.  Pioneered by Ford Motor Co. in
1988, Ford lets suppliers check stock levels in
assembly plants throughout North America.



DDM
(Distributed Data Management)  Software in an IBM
SNA environment that allows users to access data in
remote files within the network.  DDM works with
IBM's LU 6.2 session to provide peer-to-peer
communications and file sharing.



DDP
(Distributed Data Processing)  See distributed
processing.



DDS
(1) (Dataphone Digital Service)  An AT&T private
line digital service with data rates from 2400 bps
to 56Kbps.  Private analog lines can be connected
to DDS lines.

(2) (Digital Data Service)  A private line digital
service from a non-AT&T carrier.

(3) (Digital Data Storage)  A DAT format for data
backup.  It is a sequential recording method; data
must be appended at the end of previous data.  See
tape backup.



de facto standard
A widely-used format or language not endorsed by a
standards organization.



de jure standard
A format or language endorsed by a standards
organization.



deadlock
See deadly embrace.



deadly embrace
A stalemate that occurs when two elements in a
process are each waiting for the other to respond.
For example, in a network, if one user is working
on file A and needs file B to continue, but another
user is working on file B and needs file A to
continue, each one waits for the other.  Both are
temporarily locked out.  The software must be able
to deal with this.



deallocate
To release a computer resource that is currently
assigned to a program or user, such as memory or a
peripheral device.



deblock
To separate records from a block.



debug
To correct a problem in hardware or software.
Debugging software is finding the errors in the
program logic.  Debugging hardware is finding the
errors in circuit design.



debugger
Software that helps a programmer debug a program by
stopping at certain breakpoints and displaying
various programming elements.  The programmer can
step through source code statements one at a time
while the corresponding machine instructions are
being executed.



DEC
(Digital Equipment Corporation)  The trade name for
Digital's products (DECmate, DECnet, etc.).  Many
people refer to the company as DEC.



decay
The reduction of strength of a signal or charge.



decentralized processing
Computer systems in different locations.  Although
data may be transmitted between the computers
periodically, it implies limited daily
communications.  Contrast with distributed
computing and centralized processing.



decibel
(dB)  The unit that measures loudness or strength
of a signal.  dBs are a relative measurement
derived from an initial reference level and a final
observed level.  A whisper is about 10 dB, a noisy
factory 90 dB, loud thunder 110 dB.  120 dB is
painful.



decimal
Meaning 10.  The universal numbering system that
uses 10 digits.  Computers use binary numbers
because it is easier to design electronic systems
that can maintain two states rather than 10.



decision box
A diamond-shaped symbol that is used to document a
decision point in a flowchart.  The decision is
written in the decision box, and the results of the
decision branch off from the points in the box.



decision instruction
In programming, an instruction that compares one
set of data with another and branches to a
different part of the program depending on the
results.



decision making
Making choices.  The proper balance of human and
machine decision making is an important part of a
system's design.

   It is easy to think of automating tasks
traditionally performed by people, but it is not
that easy to analyze how decisions are made by an
experienced, intuitive worker.  If an improper
analysis of human decision making is made, the
wrong decision making may be placed into the
machine, which can get buried in documentation that
is rarely reviewed.  This will become an important
issue as AI applications proliferate.

   From a programming point of view, decision
making is performed two ways: algorithmic, a
precise set of rules and conditions that never
change, or heuristic, a set of rules that may
change over time (self-modify) as conditions occur.
Heuristic techniques are employed in AI systems.



decision support system
See DSS and EIS.



decision table
A list of decisions and their criteria.  Designed
as a matrix, it lists criteria (inputs) and the
results (outputs) of all possible combinations of
the criteria.  It can be placed into a program to
direct its processing.  By changing the decision
table, the program is changed accordingly.



decision tree
A graphical representation of all alternatives in a
decision making process.



deck
The part of a magnetic tape unit that holds and
moves the tape reels.  See also DEC.



declaration
In programming, an instruction or statement that
defines data (fields, variables, arrays, etc.) and
resources, but does not create executable code.



DECmate
A family of computer systems from Digital
specialized for word processing.  Introduced in
1981, DECmates use the PDP-8 architecture.



DECmcc
(DEC Managment Control Center)  Digital's network
management software for DECnet and TCP/IP.  DECmcc
Management Stations for VMS and ULTRIX support X
Window and provide color-coded alarms.



DECnet
Digital's communications network, which supports
Ethernet-style LANs and baseband and broadband WANs
over private and public lines.  It interconnects
PDPs, VAXs, PCs, Macs and workstations.  In DECnet
philosophy, a node must be an intelligent machine
and not simply a terminal as in other systems.  See
DNA.

   DECnet/DOS allows DOS machines to function as
end nodes in DECnet networks, and DECnet/OSI is the
implementation of DECnet Phase V that supports OSI
and provides compatibility with DECnet Phase IV and
TCP/IP.



decoder
A hardware device or software program that converts
a coded signal back into its original form.



decollator
A device that separates multiple-part paper forms
while removing the carbon paper.



decompiler
A program that converts machine language back into
a high-level source language.  The resulting code
may be very difficult to maintain as variables and
routines are named generically: A0001, A0002, etc.
See disassembler.



decompress
To restore compressed data back to its original
size.



decrement
To subtract a number from another number.
Decrementing a counter means to subtract 1 or some
other number from its current value.



DECstation
(1) A series of RISC-based single-user workstations
from Digital, introduced in 1989, that run under
ULTRIX.

(2) A PC series from Digital introduced in 1989.

(3) A small computer system from Digital,
introduced in 1978, used primarily for word
processing (DECstation 78).



DECsystem
(1) A series of RISC-based, 32-bit computers from
Digital that run under ULTRIX.  Introduced in 1989,
the 5400 model is a Q-bus system; the 5800 model
uses the XMI bus.

(2) A series of mainframes from Digital that were
introduced from 1974 through 1980 and were the
successor to the 36-bit PDP-10 computers.



DECtalk
A voice synthesizing system from Digital that
accepts serial ASCII text and converts it into
audible speech.  It is used in Touch-tone telephone
response systems as well as for voice-output for
visually handicapped users.



DECwindows
Digital's windowing architecture, based on X
Window, Version 11.  It is compatible with X Window
while adding a variety of enhancements.



dedicated channel
A computer channel or communications line that is
used for one purpose.



dedicated service
A service that is not shared by other users or
organizations.



default
The current setting or action taken by hardware or
software if the user has not specified otherwise.



default directory
Same as current directory.



default drive
The disk drive used if no other drive is specified.



default font
The typeface and type size used if none other is
specified.



defragger
Also called an optimizer program, it is a software
utility that defragments a disk.



defragment
To reorganize the disk by putting files into
contiguous order.  Because the operating system
stores new data in whatever free space is
available, data files become spread out across the
disk if they are updated often.  This causes extra
read/write head movement to read them back.
Periodically, the hard disk should be defragmented
to put files back into order.  See DOS Defrag.



degausser
A device that removes unwanted magnetism from a
monitor or the read/write head in a disk or tape
drive.



DEL key
(DELete key)  The keyboard key used to delete the
character under the screen cursor or some other
currently-highlighted object.



delay line
A communications or electronic circuit that has a
built-in delay.  Acoustic delay lines were used to
create the earliest computer memories.  For
example, the UNIVAC I used tubes of liquid mercury
that would slow down the digital pulses long enough
(a fraction of a second) to serve as storage.



delete
To remove an item of data from a file or to remove
a file from the disk.  See undelete.



delimiter
A character or combination of characters used to
separate one item or set of data from another.  For
example, in comma delimited records, a comma is
used to separate each field of data.



deliverable
The measurable result or output of a process.



Dell
(Dell Computer Corporation, Austin, TX)  A PC
manufacturer founded in 1984 by Michael Dell.
Originally selling under the "PCs Limited" brand,
Dell was the first to legitimize mail-order PCs by
providing quality telephone support.  Dell made the
Fortune 500 in 1991, and its fiscal 1993 revenues
exceeded two billion dollars.



Delphi
An online information service that provides access
to a wide variety of databases, files and shopping.
It is the first major online service to provide
full Internet access, not just for electronic mail.
Internet tools such as Archie, Veronica, Gopher and
Worldwide Web browsers are available to the user
logged on to Delphi.  See online services.



Delphi95
Code name of a client/server development system
from Borland expected in 1995.  It is a visual
programming system based on Object Pascal that
generates source code that is compiled into
executable programs.  It includes the Borland
Database Engine.



delta modulation
A technique that is used to sample voice waves and
convert them into digital code.  Delta modulation
typically samples the wave 32,000 times per second,
but generates only one bit per sample.  See PCM.



DEMA
(Association for Input Technology and Management)
An organization devoted to the advancement of
managers in data entry technologies.  Founded in
1976 as the Data Entry Management Association, it
sponsors educational courses and conferences.
Address: 101 Merritt 7, Norwalk, CT 06851, 203/846-
3777.



demand paging
Copying a program page from disk into memory when
required by the program.



demand processing
Same as transaction processing.



Demo II
Officially "Dan Bricklin's Demo II," it is a
demonstration, authoring and prototyping program
for PCs from Lifeboat Software, Shrewsbury, NJ.  It
is used to create courseware and slide shows and
simulate interactive user interfaces for
prototyping.  Dan Bricklin designed the original
VisiCalc spreadsheet.



demodulate
To filter out the data signal from the carrier.
See modulate.



demon
See daemon.



demoware
Demonstration software that shows some or all of
the features of a commercial product.  See
crippleware.



demultiplex
To reconvert a transmission that contains several
intermixed signals back into its original separate
signals.



density
See packing density and bit density.



departmental computing
Processing a department's data with its own
computer system.  See distributed computing.



dependent segment
In database management, data that depends on data
in a higher level for its full meaning.



dequeue
Pronounced "d-q."  To remove items from a queue in
order to process or transmit them.



DES
(Data Encryption Standard)  A NIST-standard
encryption technique that scrambles data into an
unbreakable code for public transmission.  It uses
a binary number as an encryption key with 72
quadrillion possible combinations.  The key,
randomly chosen for each session, is used to create
the encryption pattern for transmission.  See RSA.



descenders
The parts of the lower case characters g, j, p, q
and y that fall below the line.  Sometimes these
characters are displayed and printed with shortened
descenders in order to fit into a smaller character
cell, making them difficult to read.



descending sort
Arranging data from high to low sequence (Z to A,
9 to 0).



descriptor
(1) A word or phrase that identifies a document in
an indexed information retrieval system.

(2) A category name used to identify data.



deserialize
To convert a serial stream of bits into parallel
streams of bits.



DesignCAD
A family of 2-D and 3-D CAD programs from American
Small Business Computers, Pryor, OK, for DOS,
Windows and Mac, noted for their ease of use.
DesignCAD 3-D for Windows includes such features as
texture mapping, reflection mapping with up to
eight light sources and keyframe animation.



Designer
A full-featured Windows drawing program from
Micrografx, Inc., Richardson, TX.  It creates its
own DRW (2.x and 3.x) and DS4 (4.x) file formats
and supports PIC files compatible with other
Micrografx products.  Designer is very
sophisticated, providing all of the features of a
CAD program except for a programming language to
automate drawing tasks.

   When introduced, it was the first Windows
program to provide almost all of the design tools
found in the Macintosh drawing programs of the
time.



desk accessory
In the Macintosh, a program that is always
available from the Apple menu no matter what
application is running.  With System 7, all
applications can be turned into desk accessories.



desk checking
Manually testing the logic of a program.



DeskJet
A family of popular desktop ink-jet printers for
PCs from HP.



DESKPRO
A Compaq trade name for its PCs.



desktop
(1) An on-screen representation of a desktop.  The
windowing capabilities built into graphical user
interfaces (GUIs) provide a "virtual desktop," in
which the user views an infinite desktop full of
documents.  Both the Macintosh and Windows use this
metaphor, but the Mac more closely simulates a real
desktop.

(2) A buzzword attached to applications
traditionally performed on more expensive machines
that are now on a personal computer (desktop
publishing, desktop mapping, etc.).



desktop accessory
Software that simulates an object normally found on
an office desktop, such as a calculator, notepad
and appointment calendar.  See TSR.



desktop application
See desktop accessory.



desktop computer
A computer that is small enough to reside on a
desktop.  It either refers to personal computers
(PCs, Macs, Amigas, PowerPCs, etc.) or to
workstations from Sun, IBM, HP, Digital and others.



Desktop Management Interface
See DMI.



desktop manager
The part of a GUI that displays the desktop and
icons, allows programs to be launched from the icon
and files to be visually dragged & dropped (copied,
deleted, etc.).  The desktop manager combined with
the window manager make up the GUI.  The desktop
manager is included with the Mac and Windows.  In
OSF/Motif and Open Look, products such as IXI's
X.desktop and Visix Software's Looking Glass add
this capability.



desktop mapping
Using a desktop computer to perform digital mapping
functions.



desktop media
The integration of desktop presentations, desktop
publishing and multimedia (coined by Apple).



desktop organizer
See desktop accessory.



desktop presentations
The creation of presentation materials on a
personal computer, which includes charts, graphs
and other graphics-oriented information.  It
implies a wide variety of special effects for both
text and graphics that will produce output for use
as handouts, overheads and slides as well as
sequences that can be viewed on screen.  Advanced
systems generate animation and control multimedia
devices.



desktop publishing
Abbreviated "DTP."  Using a personal computer to
produce high-quality printed output or camera-ready
output for commercial printing.  It requires a
desktop publishing program, high-speed personal
computer, large monitor and a laser printer.

   DTP packages provide the ultimate in page layout
capabilities, including magazine style columns,
rules and borders, page, chapter and caption
numbering as well as precise typographic aligment.
A key feature is its ability to manage text and
graphics on screen WYSIWYG style.  The program can
flow text around graphic objects in a variety of
ways.

   Text and graphics may be created in the DTP
program, but few of them have full-featured text
and graphics capability.  Usually, the work is
created in word processing, CAD, drawing and paint
programs and then imported into the publishing
system.

   A laser printer may be used for final text
output, but it cannot print line art and shaded
drawings respectably unless its resolution is 1000
dpi or greater.  Imagesetters, at resolutions of
1270 and 2540 dpi, can accept file formats from
popular DTP packages and generate high-quality
camera ready material.

   Since DTP has dramatically brought down the cost
of high-end page makeup, it is often thought of as
"the" way to produce inhouse newsletters and
brochures.  However, creating quality material
takes experience.  Desktop publishing is no
substitute for a graphics designer who knows which
fonts to use and how to lay out the page
artistically.



deskview
See DESQview.



DeskWriter
A family of popular desktop ink-jet printers for
the Macintosh from HP.  Color models are also
available.



DESQview
A multitasking, windows environment for DOS from
Quarterdeck Office Systems, Santa Monica, CA.  It
runs multiple DOS text and graphics programs in
resizable windows.  Calendar, notepad, calculator
and communications utilities are also available.

   DESQview 386 includes the widely-used QEMM-386
expanded memory manager and utilizes the virtual
machine capability of the 386.  DESQview was a very
popular switching environment for DOS before
Windows 3.0 became so widely used.



DESQview/X
A version of DESQview that runs DOS, Windows and X
Window applications locally or remotely on other
DESQview/X PCs or X workstations.  QEMM-386 and
Adobe Type Manager are included.  There are several
ways DESQview/X can be implemented.

   It adds X Windows to a PC network, allowing each
DOS machine to run multiple applications on
different PCs in the network.  As an integration
product, it allows DOS and Windows apps to run in
an X Window network under UNIX or any other X-based
environment.  In a stand-alone DOS machine, it adds
a graphical and customizable interface to DESQview.

   Optional DESQview/X Motif and X11 toolkits allow
Motif and X applications to be recompiled to a DOS
machine.



destructive memory
Memory that loses its content when it is read,
requiring that the circuitry regenerate the bits
after the read operation.



detail file
Same as transaction file.



developer's toolkit
A set of software routines and utilities used to
help programmers write an application.  In
graphical interfaces, it provides the tools for
creating resources, such as menus, dialog boxes,
fonts and icons.  It provides the means to link the
new application to its operating environment (OS,
DBMS, protocol, etc.).  See development system,
client/server development system and GUI builder.



development cycle
See system development cycle.



development system
(1) A programming language and related components.
It includes the compiler, text editor, debugger,
function library and any other supporting programs
that enable a programmer to write a program.  See
developer's toolkit and application development
system.  For a list of popular client/server
development tools, see client/server development
system.

(2) A computer and related software for developing
applications.



development tool
Software that assists in the creation of new
software.  Compilers, debuggers, visual programming
tools, GUI builders, application generators are
examples.  See developer's toolkit.  For a list of
popular client/server development tools, see
client/server development system.



device
(1) Any electronic or electromechanical machine or
component from a transistor to a disk drive.
Device always refers to hardware.

(2) In semiconductor design, it is an active
component, such as a transistor or diode, in
contrast to a passive component, such as a resistor
or capacitor.



device adapter
Same as interface adapter.



device address
See address, I/O address and port address.



device control character
A communications code that activates a function on
a terminal.  See ASCII chart (17-20).



device dependent
Refers to programs that address specific hardware
features and work with only one type of peripheral
device.  Contrast with device independent.  See
machine dependent.



device driver
See driver.



device independent
Refers to programs that work with a variety of
peripheral devices.  The hardware-specific
instructions are in some other program (OS, DBMS,
etc.).  Contrast with device dependent.  See
machine independent.



device level
(1) In circuit design, refers to working with
individual transistors rather than complete
circuits.

(2) Refers to communicating directly with the
hardware at a machine language level.



device name
A name assigned to a hardware device that
represents its physical address.  For example, LPT1
is a DOS device name for the parallel port.



DFT mode
(Distributed Function Terminal mode)  A mode that
allows a 3270 terminal to have five concurrent
sessions with the mainframe.  Contrast with CUT
mode.



DG
See Data General.



DG/UX
(Data General UNIX)  A UNIX-based operating system
developed by Data General.  It supports symmetric
multiprocessing and is generally used with the
Tuxedo TP monitor for transaction processing.



DGIS
(Direct Graphics Interface Standard)  A graphics
interface for PC display adapters from Graphic
Software Systems, Beaverton, OR.  It is primarily
used with TI's 340x0 graphics chip and custom
drivers are licensed to video board manufacturers.



Dhrystones
A benchmark program that tests a general mix of
instructions.  The results in Dhrystones per second
are the number of times the program can be executed
in one second.  See Whetstones.



DIA
(Document Interchange Architecture)  An IBM SNA
format used to exchange documents from dissimilar
machines within an LU 6.2 session.  It acts as an
envelope to hold the document and does not set any
standards for the content of the document, such as
layout settings or graphics standards.



Diablo emulation
A printer that accepts the same commands as the
Diablo printer.



diacritical
A small mark added to a letter that changes its
pronunciation, such as the French cedilla ().



diagnostic board
An expansion board with built-in diagnostic tests
that reports results via its own readout.  Boards
for PCs, such as Landmark's KickStart and UNICORE's
POSTcard, have their own POST system and can test a
malfunctioning computer that doesn't boot.



diagnostic tracks
The spare tracks on a disk used by the drive or
controller for testing purposes.



diagnostics
(1) Software routines that test hardware components
(memory, keyboard, disks, etc.).  In personal
computers, they are often stored in ROM and
activated on startup.

(2) Error messages in a programmer's source code
that refer to statements or syntax that the
compiler or assembler cannot understand.



diagramming program
Software that allows the user to create flow
charts, organization charts and other
interconnected diagrams.  It is similar to a
drawing program, but keeps the lines connected to
the blocks when the blocks are moved.  It may also
provide text annotation of the graphic items,
allowing an equipment list to be maintained with a
network diagram, for example.



dial-up line
A two-wire line as used in the dial-up telephone
network.  Contrast with leased line.



dial-up network
The switched telephone network regulated by
government and administered by common carriers.



dial-up services
See online services.



DIALOG
An online information service that contains the
world's largest collection of databases.  Address:
3460 Hillview Ave., Palo Alto CA 94304, 415/858-
2700.  See online services.



dialog box
A small, on-screen window displayed in response to
some request.  It provides the options currently
available to the user.



dialup
See dial-up.



diazo film
A film used to make microfilm or microfiche copies.
It is exposed to the original film under
ultraviolet light and is developed into identical
copies.  Copy color is typically blue, blue-black
or purple.



DIB
(1) (Directory Information Base)  Also called white
pages, a database of names in an X.500 system.

(2) (Device Independent Bit map)  See BMP.



dibit
Any one of four patterns from two consecutive bits:
00, 01, 10 and 11.  Using phase modulation, a dibit
can be modulated onto a carrier as a different
shift in the phase of the wave.



DIBOL
(DIgital coBOL)  A version of COBOL from Digital
that runs on the PDP and VAX series.



dice
See die.



dictionary method
See LZW.



DID
(Direct Inward Dialing)  The ability to make a
telephone call directly into an internal extension
within an organization, without having to go
through the operator.



die
The formal term for the square of silicon
containing an integrated circuit.  The popular term
is chip.



dielectric
An insulator (glass, rubber, plastic, etc.).
Dielectric materials can be made to hold an
electrostatic charge, but current cannot flow
through them.



DIF
(1) (Data Interchange Format)  A standard file
format for spreadsheet and other data structured in
row and column form.  Originally developed for
VisiCalc, DIF is now under Lotus' jurisdiction.

(2) (Display Information Facility)  An IBM
System/38 program that lets users build custom
programs for online access to data.

(3) (Document Interchange Format)  A file standard
developed by the U.S. Navy in 1982.

(4) (Dual In-line Flatpack)  A type of surface
mount DIP with pins extending horizontally outward.



Difference Engine
An early calculator designed by Charles Babbage
(1820s) and subsidized by the British government.
It used rods and wheels, which was tried before by
other designers.  Never completed, Babbage turned
his attention to the Analytical Engine.



Differential Analyzer
An analog computational device built to solve
differential equations by Vannevar Bush (MIT,
1930s).  Less than a dozen were built, but they
were effective in calculating ballistics tables in
World War II.  The machine took up an entire room
and was programmed by changing camshaft-like gears
with screwdriver and wrench.



differential backup
See backup types.



differential configuration
The use of individual wire pairs for each
electrical signal for high immunity to noise and
crosstalk.  Contrast with single-ended
configuration.



differential PCM
See DPCM.



diffusion
A semiconductor manufacturing process that infuses
tiny quantities of impurities into a base material,
such as silicon, to change its electrical
characteristics.



digit
A single character in a numbering system.  In
decimal, digits are 0 through 9.  In binary, digits
are 0 and 1.



digital
Traditionally, the use of numbers and comes from
digit, or finger.  Today, digital is synonymous
with computer.  See also Digital Equipment.



digital audio disc
Same as CD.



digital audio tape
See DAT.



digital camera
A video camera that records its images in digital
form.  Unlike traditional analog cameras that
convert light intensities into infinitely variable
signals, digital cameras convert light intensities
into discrete numbers.

   It breaks down the picture image into a fixed
number of pixels (dots), tests each pixel for light
intensity and converts the intensity into a number.
In a color digital camera, three numbers are
created, representing the amount of red, green and
blue in each pixel.

   Cameras used today for TV production are digital
in design and record their initial field of view as
a digital image, using charge coupled devices
(CCDs).  However, after a microprocessor processes
the image, it is converted into analog form for
recording on analog tape recorders.  The analog
method is still much more economical for routine
video recording and playback.

   However, some day, it is expected that TV
recording will be all digital from start to finish.



digital channel
A communications path that handles only digital
signals.  All voice and video signals have to be
converted from analog to digital in order to be
carried over a digital channel.  Contrast with
analog channel.



digital circuit
An electronic circuit that accepts and processes
binary data (on/off) according to the rules of
Boolean logic.


                 Digital Plumbing!
A digital circuit can be conceptualized as a mass
of plumbing: the circuit paths are the pipes, the
transistors are the valves, and the electricity is
the water.  Imagine opening a valve, and the water
that passes through it and down a pipe will
eventually reach a second valve, causing it to turn
on, allowing water in another pipe to flow through
the second valve, which will reach another valve,
and so on.

   A resistor can be viewed as a large pipe that
narrows into a pipe with a smaller diameter, a
capacitor as a storage tank, and a diode as a one-
way valve, allowing water to flow in only one
direction.



digital computer
A computer that accepts and processes data that has
been converted into binary numbers.  All common
computers are digital.  Contrast with analog
computer.



digital convergence
The integration of computers, communications and
consumer electronics.  Data and text were converted
into digital form for the very first computers
years ago, however since the advent of audio CDs
and, increasingly, digital video, it becomes
apparent that all forms of information, both for
business and entertainment, can be managed
together.

   With one coaxial cable or optical fiber into
everyone's home, music, movies, video games and all
sorts of interactive programs can be requested on
demand similar to the way people routinely select
news, files and information from online services,
such as CompuServe and PRODIGY, via modem.



Digital Darkroom
A Macintosh graphics editing program from Silicon
Beach Software, Inc., for enhancing black & white
photographs.  Version 2.0 supports color overlays
for colorizing gray scale images.



digital data
Data in digital form.  All data in the computer is
in digital form.



digital domain
The world of digital.  When something is done in
the digital domain, it implies that the original
data (images, sounds, video, etc.) has been
converted into a digital format and is manipulated
inside the computer's memory.



digital effects
Special sounds and animations that have been
created in the digital domain.  Synthetic sounds
and reverberation, morphing and transitions between
video frames (fades, wipes, dissolves, etc.) are
examples.



Digital Equipment
(Digital Equipment Corporation, Maynard, MA)  A
major computer manufacturer, commonly known as DEC
or Digital.  It was founded in 1957 by Kenneth
Olsen, who headed the company until he retired in
1992.  Digital pioneered the minicomputer industry
with its PDP series.

   Its early success came from the scientific,
process control and academic communities; however,
after the VAX was announced in 1977, Digital gained
a strong foothold in commercial data processing.
The VAX evolved into a complete line from desktop
to mainframe, using the same VMS operating system
in all models and causing Digital to achieve
substantial growth in the 1980s.

     Over the years, Digital has been widely
recognized for its high-quality systems.  Its
strategy for the 1990s and beyond is its powerful,
RISC-based Alpha architecture introduced in 1992,
which will evolve into a complete family of
systems.



digital mapping
Digitizing geographic information for a geographic
information system (GIS).



digital monitor
A video monitor that accepts a digital signal from
the computer and converts it into analog signals to
illuminate the screen.  Common examples are MDA,
CGA and EGA monitors.  Contrast with analog
monitor.



digital nonlinear editing
See nonlinear video editing.



digital PABX
See digital PBX.



Digital Paper
A non-erasable storage material from ICI
Electronics used for tape and disk archival
storage.  It uses a polyester film coated with a
reflective layer on top of which is adhered a dye
polymer layer that is sensitive to infrared light.
A laser burns pits into the film as close as half a
micron apart.  Capacities are about one Gbyte on a
5.25" disk and 600 GBytes on a 2,400 foot tape
reel.



digital PBX
(digital Private Branch Exchange)  A modern PBX
that uses digital methods for switching in contrast
to older PBXs that use analog methods.



digital radio
The microwave transmission of digital data via line
of sight transmitters.



digital recording
See digital video, digital nonlinear editing and
magnetic recording.



Digital Research
(Digital Research, Inc., Monterey, CA)  A software
company founded in 1976 by Gary Kildall that
spearheaded the microcomputer revolution with its
CP/M operating system.  DRI's products include the
GEM windows environment, FlexOS realtime operating
system and DR DOS, a DOS-compatible operating
system with advanced features.

   In 1991, DRI was acquired by Novell, Inc.,
Provo, UT, makers of the widely-used NetWare
operating systems.



digital signal
An electronic signal transmitted as binary code
either as on/off pulses or as high and low
voltages.  See also DS.



digital signal processing
See DSP.



digital signature
A coded message added to data transmitted over a
network that verifies to the recipient that the
sender is authentic.  Digital signatures ensure
that senders are who they say they are.  See RSA
and DSS (2).



digital video
Video recording in digital form.  In order to edit
video in the computer or to embed video clips into
multimedia documents, a video source must originate
as digital (digital camera) or be converted to
digital.  Frames from analog video cameras and VCRs
are converted into digital frames (bitmaps) using 
frame grabbers or similar devices attached to a
personal computer.

   Uncompressed digital video signals consume huge
amounts of storage and require large bandwidth for
transmission.  High-ratio realtime compression
schemes are essential for effective use.  See
digital nonlinear editing and HDTV.



digital video effects
Visual effects performed by computer that create a
more interesting transition from one scene to
another rather than just switching scenes.  They
include fading or dissolving the frame, wiping one
frame over another, flipping the frame and
simulating a camera lens opening and closing (iris
effect).



digitize
To convert an image or signal into digital code by
scanning, tracing on a graphics tablet or using an
analog to digital conversion device.  3-D objects
can be digitized by a device with a mechanical arm
that is moved onto all the corners.



digitizer tablet
A graphics drawing tablet used for sketching new
images or tracing old ones and for selecting from
menus.  The user makes contact with the tablet with
a pen-like or puck-like device called a cursor
(mistakenly called a mouse), which is connected to
the tablet by a wire.  For sketching, the user
draws with the tablet cursor and the screen cursor
"draws" a corresponding image.  When tracing an
image on the tablet, a series of x-y coordinates
(vector graphics) are created, either as a
continuous stream of coordinates, or as end points.

   Menu selection is accomplished by a tablet
overlay or by a screen display.  The tablet cursor
selects an item by making contact with it on the
overlay, or by controlling the screen cursor.  See
mouse.



dimension
One axis in an array.  In programming, a dimension
statement defines the array and sets up the number
of elements within the dimensions.



dimensioning
In CAD programs, the management and display of the
measurements of an object.  There are various
standards that determine such things as tolerances,
sizes of arrowheads and orientation on the paper.



DIN connector
(Deutsches Institut fr Normung - German Standards
Institute)  A plug and socket used to connect a
variety of devices; for example, the PC keyboard
uses a five-pin DIN.  DIN plugs look like an open
metal can about a half inch in diameter with pins
inside in a circular pattern.



dingbats
A group of typesetting and desktop publishing
symbols from International Typeface Corporation
that include arrows, pointing hands, stars and
circled numbers.  They are formally called ITC Zapf
Dingbats.



diode
An electronic component that acts primarily as a
one-way valve.  As a discrete component or built
into a chip, it is used in a variety of functions.
It is a key element in changing AC into DC.  They
are used as temperature and light sensors and light
emitters (LEDs).  In communications, they filter
out analog and digital signals from carriers and
modulate signals onto carriers.  In digital logic,
they're used as one-way valves and as switches
similar to transistors.



DIP
(Dual In-line Package)  A common rectangular chip
housing with leads (pins) on both long sides.  Tiny
wires bond the chip to metal leads that wind their
way down into spider-like feet that are inserted
into a socket or are soldered onto the board.



DIP switch
(Dual In-line Package switch)  A set of tiny toggle
switches built into a DIP, which is mounted
directly on a circuit board.  The tip of a pen or
pencil is required to flip the switch on or off.

   Remember!  Open is "off."  Closed is "on."



Dir
(DIRectory)  A CP/M, DOS and OS/2 command that
lists the file names on the disk.  See DOS Dir.



direct access
The ability to go directly to a specific storage
location without having to go through what's in
front of it.  Memories (RAMs, ROMs, PROMs, etc.)
and disks are the major direct access devices.



direct access method
A technique for finding data on a disk by deriving
its storage address from an identifying key in the
record, such as account number.  Using a formula,
the account number is converted into a sector
address.  This is faster than comparing entries in
an index, but it only works well when keys are
numerically close: 100, 101, 102, etc.



direct access storage device
See DASD.



direct broadcast satellite
See DBS.



direct-connect modem
A modem that connects to a telephone line without
the use of an acoustic coupler.



direct current
See DC.



direct inward dialing
See DID.



direct memory access
See DMA.



direct view storage tube
See DVST.



Director
A popular multimedia authoring program for Windows
and Macintosh from Macromedia.  Runtime versions
can be run, edited and switched between Windows and
Mac platforms.  Director was initially introduced
as MacroMind Director for the Mac in 1989, and it
has been the de facto standard for Macintosh
multimedia authoring.  Before the Windows authoring
version was introduced, a Windows player was
available to run the Mac programs.  See Macromedia.



directory
A simulated file drawer on disk.  Programs and data
for each application are typically kept in a
separate directory (spreadsheets, word processing,
etc.).  Directories create the illusion of
compartments, but are actually indexes to the files
which may be scattered all over the disk.



directory management
The maintenance and control of directories on a
hard disk.  Usually refers to menuing software that
is easier to use than entering commands.



Directory Server Agent
See DSA.



directory service
In a messaging system, it is a directory of names
and addresses of every mail recipient on the
network.  When sent a user name as a query, it
returns the logical mail address (mailbox) of that
user.  A directory service usually differs from a
network naming service in that a directory service
returns a logical address, whereas a naming service
returns the physical address of a node.  Sometimes,
either term refers to either function.



directory tree
A graphic representation of a hierarchical
directory as in the following example.  See DOS
Tree.

     DATABASE
             BUDGETS
             CLIENTS
     
     STORIES
            SHORT
            NOVELS





dirty power
A non-uniform AC power (voltage fluctuations, noise
and spikes), which comes from the electric utility
or from electronic equipment in the office.



disable
To turn off a function.  Disabled means turned off,
not broken.  Contrast with enable.



disassembler
Software that converts machine language back into
assembly language.  Since there is no way to easily
determine the human thinking behind the logic of
the instructions, the resulting assembly language
routines and variables are named and numbered
generically (A001, A002, etc.).  Disassembled code
can be very difficult to maintain.  See decompiler.



disc
An alternate spelling for disk.  Compact discs and
videodiscs are spelled with the "c."  Most computer
disks are spelled with a "k."



discrete
A component or device that is separate and distinct
and treated as a singular unit.



discrete component
An elementary electronic device constructed as a
single unit.  Before integrated circuits (chips),
all transistors, resistors and diodes were
discrete.  They are widely used in amplifiers and
other devices that use large amounts of current.
They are also still used on circuit boards
intermingled with the chips.



discrete cosine transform
See DCT.



discretionary hyphen
A user-designated place in a word for hyphenation.
If the word goes over the margin, it will split in
that location.



dish
A saucer-shaped antenna that receives, or transmits
and receives, signals from a satellite.



disk
A direct access storage device.  See floppy disk,
hard disk, magnetic disk, optical disk and
videodisc.


disk array
Two or more disk drives combined in a single unit
for increased capacity, speed and/or fault tolerant
operation.  See RAID.



disk based
(1) A computer system that uses disks as its
storage medium.

(2) An application that retrieves data from the
disk as required.  Contrast with memory based.



disk cache
See cache.



disk cartridge
A removable disk module that contains a single hard
disk platter or a floppy disk.



disk controller
A circuit that controls transmission to and from
the disk drive.  In a personal computer, it is an
expansion board that plugs into an expansion slot
in the bus.  See hard disk.



disk crash
See head crash.



disk drive
A peripheral storage device that holds, spins,
reads and writes magnetic or optical disks.  It may
be a receptacle for disk cartridges, disk packs or
floppy disks, or it may contain non-removable disk
platters like most personal computer hard disks.



disk dump
A printout of disk contents without report
formatting.



disk duplicator
A device that formats and makes identical copies of
floppy disks for software distribution.  Simple
units contain two floppy disks and require manual
loading, elaborate units have automatic loading and
may also attach the labels.



disk emulator
A solid state replication of a disk drive.



disk file
A set of instructions or data that is recorded,
cataloged and treated as a single unit on a disk.
Source language programs, machine language
programs, spreadsheets, data files, text documents,
graphics files and batch files are examples.



disk format
The storage layout of a disk as determined by its
physical medium and as initialized by a format
program.  For example, a 5.25" 360KB floppy vs a
3.5" 1.44MB floppy or a DOS disk vs a Mac disk.
See low-level format, high-level format, DOS format
and file format.



disk management
The maintenance and control of a hard disk.  Refers
to a variety of utilities that provide format,
copy, diagnostic, directory management and
defragmenting functions.



disk memory
Same as disk.  In this lexicon, disks and tapes are
called storage devices, not memory devices.



disk mirroring
The recording of redundant data for fault tolerant
operation.  Data is written on two partitions of
the same disk, on two separate disks within the
same system or on two separate computer systems.



disk operating system
See DOS.



disk optimizer
A utility program that defragments a hard disk.
See defragment.



disk pack
A removable hard disk module used in minis and
mainframes that contains two or more platters
housed in a dust-free container.  For mounting, the
bottom of the container is removed.  After
insertion, the top is removed.



disk parameters
See hard disk configuration.



disk partition
A subdivision of a hard disk.  The maximum size of
a disk partition depends on the operating system
used.  See DOS Fdisk.



disk striping
The spreading of data over multiple disk drives to
improve performance.  Data is interleaved by bytes
or by sectors across the drives.  For example, with
four drives and a controller designed to overlap
reads and writes, four sectors could be read in the
same time it normally takes to read one.  Disk
striping does not inherently provide fault
tolerance or error checking.  It is used in
conjunction with various other methods.  See RAID.



Diskcopy
A DOS and OS/2 utility used to copy entire floppy
disks track by track.  See DOS Diskcopy.



diskette
Same as floppy disk.



diskless workstation
A workstation without a disk.  Programs and data
are retrieved from the network server.



DISOSS
(DIStributed Office Support System)  An IBM
mainframe centralized document distribution and
filing application that runs under MVS.  Its
counterpart under VM is PROFS.  It allows for e-
mail and the exchange of documents between a
variety of IBM office devices, including word
processors and PCs.  DISOSS uses the SNADS
messaging protocol.



dispatcher
Same as scheduler.



dispersed intelligence
Same as distributed intelligence.



displacement
Same as offset.  See base/displacement.



display
(1) To show text and graphics on a video or flat
panel screen.

(2) A screen or monitor.



display adapter
An expansion board that plugs into a desktop
computer that converts the images created in the
computer to the electronic signals required by the
monitor.  It determines the maximum resolution,
maximum refresh rate and the number of colors that
can be sent to the monitor.  The monitor must be
equally capable of handling its highest resolution
and refresh.  The VGA card is the common display
adapter for the PC.

   The display adapter converts the characters or
graphic patterns (bitmaps) within the computer's
memory into signals used to refresh the display
screen.  Display adapters also contain their own
memory, which is used to build the images before
they are displayed.

   In earlier digital systems (CGA, EGA, etc.), the
display adapters generated digital signals for the
monitor.  The monitor then did the conversion from
digital to analog.  In today's analog systems (VGA,
Macintosh, etc.), the display adapter creates the
analog signals that are sent to the monitor.

             It's Real Straightforward
Graphics adapter, graphics board, graphics card,
graphics controller, video display adapter, video
display board, video display card, video display
controller, video adapter, video board, video card,
video controller, display board, display card,
display controller, VGA adapter, VGA board, VGA
card and VGA controller are other terms for the
display adapter.

  By the way, a video graphics board is something
different.  It is a video capture board that
accepts analog NTSC video from a videotape player
(VCR) or camera.  Increasingly, NTSC video is being
integrated with computers, so the terminology might
even get a tad more confusing!



display attribute
See attribute.



display board
Same as display adapter.



display card
Same as display adapter.



display cycle
In computer graphics, the series of operations
required to display an image.



display device
See display screen and display adapter.



display element
(1) In graphics, a basic graphic arts component,
such as background, foreground, text or graphics
image.

(2) In computer graphics, any component of an
image.



display entity
In computer graphics, a collection of display
elements that can be manipulated as a unit.



display font
Same as screen font.



display frame
In computer graphics, a single frame in a series of
animation frames.



display list
In computer graphics, a collection of vectors that
make up an image stored in vector graphics format.



display list processor
In computer graphics, an engine that generates
graphic geometry (draws lines, circles, etc.)
directly from the display list and independently of
the CPU.



display modes
See PC display modes.



Display PostScript
The screen counterpart of the PostScript printer
language that translates elementary commands in an
application to graphics and text elements on
screen.  It is designed for inclusion in an
operating system to provide a standard, device-
independent display language.



display screen
A surface area upon which text and graphics are
temporarily made to appear for human viewing.  It
is typically a CRT or flat panel technology.



display terminal
See video terminal.



DisplayWrite
A full-featured IBM word processing program for PCs
that stems from the typewriter-oriented
DisplayWriter word processing system first
introduced in 1980.  See XyWrite.



distributed computing
The use of multiple computers in an organization
rather than one centralized system.  Most all large
organizations have computers dedicated to
departmental use.  Distributed computing implies
that they are networked together, not just
decentralized systems without any communications
between them.  In addition, client/server
applications continue to disburse more and more
computers througout the enterprise.  Distributed
computing used to be called distributed processing.
See client/server.



Distributed Computing Environment
See OSF.



distributed data processing
See distributed processing.



distributed database
A database physically stored in two or more
computer systems.  Although geographically
dispersed, a distributed database system manages
and controls the entire database as a single
collection of data.  If redundant data is stored in
separate databases due to performance requirements,
updates to one set of data will automatically
update the additional sets in a timely manner.



distributed file system
Software that keeps track of files stored across
multiple networks.  It converts file names into
physical locations.



distributed function
The distribution of processing functions throughout
the organization.



distributed intelligence
The placing processing capability in terminals and
other peripheral devices.  Intelligent terminals
handle screen layouts, data entry validation and
other pre-processing steps.  Intelligence placed
into disk drives and other peripherals relieves the
central computer from routine tasks.



distributed logic
See distributed intelligence.



Distributed Management Environment
See DME.



distributed processing
The first term used to describe the distribution of
multiple computers throughout an organization in
contrast to a centralized system.  It started with
the first minicomputers.  Today, distributed
processing is called distributed computing.  See
also client/server.



dithering
In computer graphics, the creation of additional
colors and shades from an existing palette.  In
monochrome displays, shades of grays are created by
varying the density and patterns of the dots.  In
color displays, colors and patterns are created by
mixing and varying the dots of existing colors.

   Dithering is used to create a wide variety of
patterns for use as backgrounds, fills and shading,
as well as for creating halftones for printing.  It
is also used in anti-aliasing.



divestiture
The breakup of AT&T.  By federal court order, AT&T
divested itself on January 1, 1984 of its 23
operating companies.  Bell Labs was renamed AT&T
Bell Labs, and its Western Electric manufacturing
division became AT&T Technologies.  See RBOC and
Bellcore.



divide overflow
A program error in which a number is accidentally
divided by zero or by a number that creates a
result too large for the computer to handle.



DIX standard
(DEC-Intel-Xerox standard)  An earlier Ethernet
standard which has been superseded by IEEE 802.3.
Network protocols often use the Ethernet frame from
this specification.



DL/1
(Data Language 1)  The database language in IMS.



DLC
(1) (Data Link Control)  See data link and OSI.

(2) (Data Link Control)  The protocol used in IBM's
Token Ring networks.

(3) (Digital Loop Carrier)  See loop carrier.



DLC chip
Any one of several Intel-compatible CPUs from Cyrix
Corporation.  See 486DLC.



DLL
See dynamic link library.



DMA
(Direct Memory Access)  Specialized circuitry or a
dedicated microprocessor that transfers data from
memory to memory without using the CPU.  Although
DMA may periodically steal cycles from the CPU,
data is transferred much faster than using the CPU
for every byte of transfer.

   On PCs, there are eight DMA channels commonly
used as follows.  Most sound cards are set to use
DMA channel 1.

         DMA channel     Used for
              0        8-bit transfer
              1        8-bit transfer
              2        Floppy disk controller
              3        8-bit transfer
              4        Cascaded from 0-3
              5        16-bit transfer
              6        16-bit transfer
              7        16-bit transfer





DME
(Distributed Managment Environment)  A network
monitoring and control protocol defined by the Open
Software Foundation.  See OSF.



DMI
(Desktop Managment Interface)  A management system
for PCs developed by the Desktop Management Task
Force (initiated by Intel).  DMI provides a bi-
directional path to interrogate all the hardware
and software components within a PC.  When PCs are
DMI-enabled, their hardware and software
configurations can be monitored from a central
station in the network.

   A memory-resident agent resides in the
background.  When queries are made to the agent, it
responds by sending back data contained in MIFs
(Management Information Files) and/or activating
MIF routines.  Static data in a MIF would contain
items such as model ID, serial number, memory and
port addresses.  A MIF routine could report errors
to the management console as they occur, or it
could read ROM or RAM chips and report their
contents, as well.

   DMI is a complete management system but can co-
exist with SNMP and other management protocols.
For example, when an SNMP query arrives, DMI can
fill out the SNMP MIB with data from its MIF.  A
single workstation or server can serve as a proxy
agent that would contain the SNMP module and
service an entire LAN segment of DMI machines.

   Data-only MIFs can be created by anyone using a
text editor, but it is envisioned that all hardware
and software vendors will eventually include at
least a data-only MIF with their products.



     DMI LAYERS
  Ŀ
    Management    Calls to DMI from console
    Interface     software, such as Intel's
      (API)       LANdesk and Novell's NMS.
  Ĵ
     Service      Actual DMI agent in each
      Layer       client machine (TSR, DLL, etc.)
  Ĵ
    Component     Accesses the MIF and provides
    Interface     calls from component back
    to the console.





DMPL
(Digital Microprocessor Plotter Language)  A vector
graphics file format from Houston Instruments that
was developed for plotters.  Most plotters support
the DMPL or HPGL standards.



DMTF
(Desktop Management Task Force)  Initiated by Intel
in 1992, it created the DMI interface.  See DMI.



DNA
(Digital Network Architecture)  Introduced in 1978,
DNA defines Digital's protocols, formats and
control of message exchange over a network.  DECnet
is the implementation of this architecture.



DNS
(Domain Naming System)  An e-mail addressing system
used in networks such as the Internet and BITNET.
It converts an e-mail address, such as joe@clc.com
to the internet address (IP) for transmission.



do loop
A high-level programming language structure that
repeats instructions based on the results of a
comparison.  In a DO WHILE loop, the instructions
within the loop are performed if the comparison is
true.  In a DO UNTIL loop, the instructions are
bypassed if the comparison is true.  The following
DO WHILE loop prints 1 through 10 and stops.

   COUNTER = 0
   DO WHILE COUNTER < 10
     COUNTER = COUNTER + 1
     ? COUNTER
   ENDDO





do nothing instruction
Same as no-op.



docking station
A base station for a laptop that includes a power
supply and expansion slots as well as monitor and
keyboard connectors.  See port replicator.



docs
Short for documents or documentation.



document
(1) Any paper form that has been filled in.

(2) A word processing text file.

(3) In the Macintosh, any text, data or graphics
file created in the computer.



document exchange software
Software that allows document files to be viewed on
other computers that do not have the original
application that created it.  The software comes in
two parts.  The first component converts the
document into a proprietary format for
distribution.  The second is a viewer program that
displays the files, and viewers are generally free.

   Unlike file viewers that rely on the fonts
installed in the computer to display file contents
accurately, document exchange systems carry the
fonts over within the file format to the viewing
machine.  The fonts are only used for displaying
the document, however, not for general use by the
system.  The viewers may allow sections of the
document to be copied to the clipboard.

   The three major products to date are Adobe's
Acrobat, Farallon's Replica and No Hands Software's
Common Ground.



document handling
A procedure for transporting and handling paper
documents for data entry and scanning.



document image management
See document imaging.



document image processing
See document imaging.



document imaging
The online storage, retrieval and management of
electronic images of documents.  The main method of
capturing images is by scanning paper documents.

   Document imaging systems replace large paper-
intensive operations.  Documents can be shared by
all users on a network and document routing can be
controlled by the computer (workflow automation).
The systems are often simpler to develop and
implement than traditional data processing systems,
because users are already familiar with the paper
documents that appear on screen.

   Document images are created in raster graphics
format, and although a small amount of text (key
words) may be associated with the document in order
to index it, the meaning of the document content is
known only to the human viewer, not the computer.
Like microfilm, signatures and other original
markings remain intact.



document management
Keeping track of stored documents that have been
scanned into the computer or created via word
processing, spreadsheet or other applications.  A
document management system may be an integral part
of a document imaging system.



document mark
In micrographics, a small optical blip on each
frame on a roll of microfilm that is used to
automatically count the frames.



document processing
Processing text documents, which includes indexing
methods for text retrieval based on content.  See
document imaging.



document publishing software
See document exchange software and desktop
publishing.



document viewer
See file viewer and document exchange software.



documentation
The narrative and graphical description of a
system.  Documentation for an information system
includes:


               Operating Procedures
 1. Instructions for turning the system on and
    getting the programs initiated (loaded).

 2. Instructions for obtaining source documents for
    data entry.

 3. Instructions for entering data at the terminal,
    which includes a picture of each screen layout
    the user will encounter.

 4. A description of error messages that can occur
    and the alternative methods for handling them.

 5. A description of the defaults taken in the
    programs and the instructions for changing
    them.

 6. Instructions for distributing the computer's
    output, which includes sample pages for each
    type of report.


               System Documentation
 1. Data dictionary - Description of the files and
    databases.

 2. System flow chart - Description of the data as
    it flows from source document to report.

 3. Application program documentation - Description
    of the inputs, processing and outputs for each
    data entry, query, update and report program in
    the system.


              Technical Documentation
 1. File structures and access methods

 2. Program flow charts

 3. Program source code listings

 4. Machine procedures (JCL)





docuterm
A word or phrase in a text document that is used to
identify the contents of the document.



domain
(1) In database management, all possible values
contained in a particular field for every record in
the file.

(2) In communications, all resources under control
of a single computer system.  In a LAN, a domain is
a subnetwork comprised of a group of clients and
servers under the control of one security database.
Dividing LANs into domains improves performance and
security.

(3) In magnetic storage devices, a group of
molecules that makes up one bit.

(4) In a hierarchy, a named group that has control
over the groups under it, which may be domains
themselves.



domain naming system
See DNS.



dominant carrier
A telecommunications services provider that has
control over a large segment of a particular
market.



donating old equipment
See National Cristina Foundation.



dongle
Same as hardware key.



door
(1) In a BBS system, a programming interface that
lets an online user run an application program in
the BBS.

(2) See drive door.



doorway mode
In a communications program, a mode that passes
function, cursor, ctrl and alt keystrokes to the
BBS computer in order to use the remote application
as if it were on the local machine.



dopant
An element diffused into pure silicon in order to
alter its electrical characteristics.



doping
Altering the electrical conductivity of a
semiconductor material, such as silicon, by
chemically combining it with foreign elements.  It
results in an excess of electrons (n-type) or a
lack of electrons (p-type) in the silicon.



DOS
(1) (Disk Operating System)  Pronounced "dahss."  A
generic term for operating system.

(2) (Disk Operating System)  A single-user
operating system for the PC.  It is the most widely
used operating system in the world.  The version
provided by IBM is called PC-DOS to distinguish it
from MS-DOS, the version for non-IBM PCs.  All
versions of DOS and MS-DOS have been developed by
Microsoft with IBM participating in varying
degrees.  The more recent versions of DOS are
developed independently.

   Except for DOS 6, both versions are almost
identical.  Microsoft's MS-DOS 6 and IBM's PC-DOS 6
provide different versions of the utilities,
although all commands and primary functions are the
same.  See DOS 6.

   In this lexicon, DOS refers to both PC-DOS and
MS-DOS.  See DOS abc's.



DOS /
Slashes are used to identify switches, or
parameters, in a DOS command.  They precede letters
or numbers and their meaning is pertinent only to
the command they are used with.  See DOS backslash
(\).



DOS %
Percent signs are used in DOS batch files to define
user input.  The following batch file example would
copy a file and then delete it:

   copy %1 %2
   del %1

   If the above file were named MOVEIT.BAT, the
following example moves file ABC into the \HOLD
directory and then deletes it from the current
directory:

   moveit abc \hold





DOS .
The single dot in a DOS command refers to all files
in the current directory.  For example, del . is
the same as del *.*, which deletes all files.



DOS ..
The double dots refer to the directory one level
above the current directory.  The command cd ..
switches you to the higher directory.  Double
clicking on a [..] in a file menu does the same
thing.



DOS 5
A major DOS upgrade in 1991 that includes an
enhanced DOS shell with task swapping, undelete
commands, a full-screen text editor and online
help.  It includes memory managers that support
extended and expanded memory and allow part of DOS
to be loaded into the high memory area (HMA).  It
supports 2GB hard disks and 2.88MB floppies.

   DOS 5 includes Microsoft's QBasic language,
which supersedes GW-BASIC in the MS-DOS version and
accompanies BASICA in the IBM version.  Major DOS 5
features covered in this database are:

           DOS Dos
           DOS Doskey
           DOS Editor
           DOS EMM386.EXE
           DOS Loadhigh
           DOS Mirror
           DOS online help
           DOS Setver
           DOS Task Swapper
           DOS Undelete
           DOS Unformat


   An excellent, comprehensive book on DOS 5 that
includes handy utilities on disk, is "DOS 5" by
Alfred Glossbrenner, ISBN 0-679-73925-4.

   For a thorough understanding of DOS memory
management, read "DOS Beyond 640K" by James S.
Forney, ISBN 0-8306-3744-3.



DOS 6
An upgrade introduced in 1993 that includes built-
in realtime compression and new utilities for
memory management, backup, file transfer, disk
optimization, antivirus and for managing multiple
startup configurations.  Following is a list of
major DOS 6 features in this database.  To review
them sequentially, go into Search Definitions and
search on DOS 6.

           DOS Defrag
           DOS Deltree
           DOS DoubleSpace
           DOS Interlink
           DOS Memmaker
           DOS Move
           DOS MSAV
           DOS MSbackup
           DOS MSD
           DOS startup options


                    IBM's DOS 6
IBM's DOS 6, which was formally introduced as
PC-DOS 6.1, is somewhat different than Microsoft's
DOS 6.  All the fundamental DOS commands are the
same, but PC-DOS 6.1 includes direct support for
pen-based computing and the PCMCIA card.  For the
first time, PC-DOS is available as a retail
product, not just for IBM systems.

   Several utilities are different than MS-DOS 6.
For example, PC-DOS 6.1 includes an enhanced text
editor with split screens and macros, an unattended
program scheduler, an antivirus monitor that takes
only 5K and claims fewer false alarms, a more
comprehensive backup utility that includes tape and
backup scheduling, and a full-screen Undelete for
both DOS and Windows that lets you preview your
files before you delete them.

   For years, the terms MS-DOS and PC-DOS
differentiated Microsoft's version from IBM's
version, but the term DOS is generally used for
both.  Up until DOS 6, they have been identical for
all practical purposes.  For DOS 6, the terms
MS-DOS and PC-DOS once again will differentiate the
two products.



DOS 7
The next version of DOS from Microsoft is expected
to be a 32-bit operating system that will run in
only 386s and up and may be a significant change to
DOS.  However, this industry moves like a speeding
bullet, so stay tuned.  Depending on the popularity
of Windows 95, DOS 7 may or may not happen.

   The first release of a "DOS 7" is Novell's DOS
7.  See Novell DOS.



DOS ::
Double colons are used to make a comment in a DOS
batch file.  For example, the following line will
not be processed by DOS or displayed on screen:

  :: sbl.exe is the screen blanker program





DOS abc's
The DOS abc's are a tutorial for users that want to
learn some basic disk concepts and know how to run
a program and copy files.  The advantage of knowing
DOS commands is that you can manage any PC.  DOS
commands are the common denominator.

   The DOS abc's should be read in sequence the
first time through.

     DOS abc's - How a disk is organized
     DOS abc's - How to enter a command
     DOS abc's - How to run a program
     DOS abc's - What else you need to know


                   WHAT IS DOS?
DOS (pronounced "dahss") stands for disk operating
system.  It is a master control program that is
automatically run when you start your PC.  DOS
stays in the computer all the time letting you

    run a program   and   manage files.


To use DOS, you must know

    where your programs and data are stored

             and

                how to talk to DOS.





DOS abc's -  How a disk is organized
The DOS abc's tutorials are in sequence.  Be sure
to read this one first.


                      A, B, C
DOS disks are identified by a letter and colon.
Floppy disks are A: and B:.  The hard drive is C:
Additional hard drives, CD-ROM or optical drives
are named D:, E: and so on.

   The default drive is the drive DOS works on
unless you tell it otherwise.  It is usually drive
C: since your hard disk contains most everything.


                          Hard disks
  Floppy     DOS versionsĿ
  Disks         2.x, 3.x      4.01       5 & 6
 Ŀ    Ŀ  Ŀ  Ŀ
   A:       C: (32M)    C:      C:       
     Ĵ                    
              D: (32M)   (512M)     (2G)   
 Ŀ    Ĵ                    
   B:       E: (32M)                     
         

           DOS 2.x and 3.x
           only handle disks
           up to 32MB.  The
           drive is broken up
           into "logical" drives
           of 32MB each.




                    DIRECTORIES
Disks are further divided into simulated file
drawers, called "directories," the size of which is
limited only by the unused space left on the disk.

          Ŀ Ŀ Ŀ
           Data    Words  Numbers
            ͸     ͸     ͸  
            

   Your software package's install program usually
creates the directory for you and copies the
appropriate files into it.  But there are times
when you'll want to create your own directories and
move files among them.  Suppose you'd like to
transfer office work to your home computer.  DOS
lets you copy files into the appropriate
directories on each machine.


                  Root Directory
The current directory is the file drawer you're in
on each disk.  When you start the computer, the
current directory is the "root" directory.  All
other directories stem from the root.

   You can store anything in the root directory,
but typically the hard disk's root directory is
used for utility programs and batch files, not
applications.  Applications are stored in their own
directories, one for database, one for word
processing, etc.:

                 Ŀ
                  Root  
                   ͸  
                 
           Ŀ
       Ŀ Ŀ Ŀ
        Data    Words  Numbers
         ͸     ͸     ͸  
         


   When you start DOS, the default drive is C and
the current directory is the root.  When you first
switch to another drive, the current directory is
the root directory of that disk.

   Every disk has a root directory as is noted in
the following illustration (each rectangle
represents a directory or subdirectory).


  Floppy         Hard disk           Hard disk
  Disks      DOS 2.x and 3.x      DOS 4.01 and up
    A:               C:                  C:
 Ŀ   Ŀ  Ŀ
  root    root            root          
          Ĵ  Ĵ
      Ĵ    
    B:               D:                     
 Ŀ   Ŀ  Ĵ
  root    root                         
          Ĵ  Ĵ      
                     
                     E:         
            Ŀ
            root          
                          
            


                       Note!
On a floppy, everything is typically stored in the
root directory, because floppies are usually
dedicated to one purpose.



                     Remember!
DOS's reference point is the default drive and
current directory.  You can think of them as the

        "current" drive and directory, or

        "working" drive and directory, or

        "default" drive and directory.





DOS abc's - How to enter a command
These tutorials are in sequence.  Be sure you
understand the content of

     DOS abc's - How a disk is organized.


                  THE DOS PROMPT
You type in a command, and DOS carries it out.

   DOS tells you when it is ready to accept a
command by displaying its "prompt" on screen.  The
DOS prompt also informs you which drive and
directory you're currently in.  The following
prompt means C drive and root directory:

                   C:\>


   The C: means drive C.  The backslash \ means
root directory.  The > is an end symbol.

   If you switched to the DATA directory, your
prompt would change to:

                C:\DATA>.

              C:    C drive
              \     root directory
              DATA  data directory
              >     end of prompt


                  Are We in Sync?
Does your on-screen prompt look like the examples
above?  If it doesn't, and all you see is C> or D>
no matter which directory you're in, you're missing
an important command in your AUTOEXEC.BAT file.

   For now, type the following command at the DOS
prompt:
                 prompt $p$g


   Later on, you will want to set this prompt
permanently.  See DOS prompt and DOS AUTOEXEC.BAT.


             Can't Get the DOS Prompt?
All DOS commands in this tutorial are run from the
DOS prompt.  If your computer starts up with a menu
of programs to run, you'll have to exit this
menuing system (also called a shell) first.

   Usually there's a "To DOS," "DOS prompt" or
"Command Prompt" option in the menu.  Select it to
get your DOS prompt.



        Pressing Enter Executes the Command
After you type in your command, pressing the Enter
key causes DOS to begin the action.  The following
command renames a file from RED to BLUE.  The
action is taken when you press the Enter key:

             C:\>rename red blue(ENTER)


   You must have a space between the command verb
Rename and the next word.

   In further examples, you won't see the (ENTER)
notation.  It is however always implied.  Nothing
happens until you press Enter!



               Switching Directories
Assume you have the following directories on your
hard disk:

                    C:\>
                 Ŀ
                  Root  
                   ͸  
                 
                     
          Ŀ
      C:\DATA>   C:\WORDS>  C:\NUMBERS>
      Ŀ  Ŀ  Ŀ
       Data     Words   Numbers
        ͸      ͸      ͸  
          


   If you're in the C:\DATA> directory now, and you
want to go to the C:\NUMBERS> directory, you would
type:

                             Explanation
    C:\DATA>cd \numbers    change to NUMBERS
    C:\NUMBERS>            prompt has changed


               cd \numbers means

CHANGE DIRECTORY TO   ROOT  then  NUMBERS DIRECTORY
           cd           \             numbers


   Switch back to the root directory by typing:

                               Explanation
      C:\NUMBERS>cd \     change to root directory
      C:\>                prompt has changed


         CHANGE DIRECTORY TO   ROOT
                 cd              \



                  Subdirectories
Subdirectories are directories subordinate to your
main directories.  The following example organizes
files separately for two writers:

                      Ŀ
    Directory          Words 
                             
                      
                     Ŀ
                 Ŀ Ŀ
 Subdirectories  Joseph  Helene 
                   ͸     ͸  
                  


   For more on directories and subdirectories, look
up DOS directories.



                 Switching Drives
To switch from one drive to another, type the drive
letter and colon as in the following examples:

                 Explanation
   C:\>d:     change from C to D
   D:\>       prompt has changed to show new drive

   Switch to A:

   D:\>a:     change from D to A
   A:\>       prompt has changed



                     Remember!
Don't forget the colon.  The letter A by itself
would be a file name, not a drive ID.  The a:
identifies the A drive.




To review...

  DOS is a master control program that lets you
  run a program and manage files.





DOS abc's - How to run a program
These tutorials are in sequence.  Be sure you
understand the content of

     DOS abc's - How a disk is organized and
     DOS abc's - How to enter a command.


                 RUNNING A PROGRAM
To run a program, go to the directory the program
is in and simply type in the program's name.  For
example, to go to the LOTUS directory and run the
123.EXE program, you would type:

    C:\>cd \lotus    go to directory
    C:\LOTUS>123     run 123.EXE program


   The .EXE is a file extension for a program that
is ready to run (EXEcute).  You'll learn about file
extensions in DOS file names.

   You can usually (but not always) run a program
in a different directory or even a different disk
by naming the path to it.

   Suppose you're in the ANYWHERE directory on
drive C, you could run PARADOX3.EXE in directory
DATA on E by typing:

    C:\ANYWHERE>e:\data\paradox3


   Note: You don't enter the .EXE extension when
naming a program to run.

   Also note:  The "ANYWHERE" above is a prompt
used in examples to indicate that the command will
work no matter which directory you're currently in.


                   Command Sytax
Most programs are run by typing in their name.  For
example, the DOS version of this database is loaded
and run by typing gloss at the DOS prompt.

   Sometimes, additional information can be given
to the program when it is run.  For example, in the
Windows version of this database, adding the word
mono to the program name changes the display for a
laptop; for example:

               wingloss mono


   When managing your files with DOS, the commands
often require additional input; for example, the
Format command must be typed with the name of the
disk you want to format:

                 format a:





DOS abc's - What else you need to know


                   OTHER TOPICS

Be sure you understand the content of the previous
DOS abc's tutorials, including

     DOS abc's - How a disk is organized
     DOS abc's - How to enter a command
     DOS abc's - How to run a program

   To learn how to create directories, copy files
and perform other routine operations, look up the
following topics:

      DOS file names
      Learn about names and extensions.

      DOS wild cards
      Learn how to select groups of files.

      DOS directories
      More examples on switching directories.

      DOS Dozen
      12 commands that do everything.

      DOS batch file
      How to automate procedures.

      DOS AUTOEXEC.BAT
      How to automatically set up your
      computer each time you turn it on.

      DOS CONFIG.SYS
      How to configure the computer.



      Ŀ
              End of the ABC's.         
                                        
       The rest of the DOS commands are 
       in A-Z order under DOS xxxx.     
      





DOS Abort, Retry
See DOS error messages.



DOS ANSI.SYS
ANSI.SYS is a driver used for screen control
(cursor movement, clearing the screen, etc.) and as
a keyboard macro processor to assign commands to a
function key or reassign awkwardly placed keys.
Some early applications require ANSI.SYS, but
generally new applications do not.  See DOS
CONFIG.SYS.



DOS antivirus
See DOS MSAV.



DOS Append
An external command as of DOS 3.3 that lets
programs open data files as if they were in the
current directory.  It is used only with older
programs that cannot access different directories.

   append          display appended paths
   append e:\abc   append E:\ABC
   append;         cancel appends


              Want to Combine Files?
If you want to append one file to another, look up
DOS combining files.



DOS archive files
See DOS Xcopy and DOS Attrib.



DOS Assign
An external command used to reassign drives when
programs work only with specific drives.  In DOS 6,
this command is no longer installed, although it
still resides on the DOS 6 Supplemental Disk.

   The following example allows an install program
that requires the floppy to be in drive A: to run
from drive B:.

              assign a=b

   To cancel assignments, type:

              assign


   If your program is ancient and works only with
drive A:, you can fake it into accessing the hard
disk with:

              assign a=c


                    Important!
Cancel assignments before using Backup, Diskcopy,
Format, Join, Label, Print, Restore or Subst.



DOS Attrib
An external command that displays and changes file
attributes, which are settings in every DOS file.
The file attributes are bits that are turned on
(set to 1) or turned off (set to 0).

             FILE ATTRIBUTES

             A - Archive
             H - Hidden file
             R - Read only
             S - System file


  To display the current attributes in all files in
the current directory, type:

      attrib *.*     files only
      attrib *.* /s  files & subdirectories
                      (DOS 3.3 and up)

READ ONLY STATUS
When a file is read-only, it can't be changed or
deleted.  To set and reset VITAL.TXT, type:

   attrib vital.txt +r   set to read-only
   attrib vital.txt -r   reset to read/write


ARCHIVE ATTRIBUTE
As of DOS 3.3, all files are set to archive status
(archive bit on), which assists in making backups.
When files are copied by the Xcopy or Backup
commands, the archive bit is turned off (0) on the
original file and not turned on again (1) until the
file has been modified by some application.  The
following example removes and restores the archive
status in XYZ.TXT.

   attrib xyz.txt -a   turn off
   attrib xyz.txt +a   turn back on


   To back up only modified files (archive bit on),
use the /m switch with the Xcopy and Backup
commands.  After copying, the archive bit on the
original file is turned off (set to zero).  For
example, to Xcopy only modified files (archive bit
on) to the B drive, type:

           xcopy *.* b: /m


   For more archive examples, see DOS Xcopy and DOS
Backup/Restore.



SYSTEM AND HIDDEN ATTRIBUTE (as of DOS 5)
These attributes are assigned to important DOS
files and other files that your applications may
generate.  As a rule, you should not tamper with
them unless you know what you are doing.  Prior to
DOS 5, you needed a third-party utility to do this.
As of DOS 5, you can reset these attributes in
most, but not all files, in which case you may
still need a third-party program.

   attrib xyz +s   make XYZ a system file
   attrib xyz -s   clear system file status

   attrib xyz +h   make XYZ a hidden file
   attrib xyz -h   clear hidden status





DOS AUTOEXEC.BAT
AUTOEXEC.BAT is a special DOS batch file that is
automatically executed whenever the computer is
started or restarted.  It must be stored in the
root directory.

   It is used to load TSR (Terminate and Stay
Resident) programs that stay in memory and "pop up"
whenever you call them.  It's also used to start an
application when the computer is turned on, perhaps
a menu program that launches a variety of
applications.

   Two common commands in AUTOEXEC.BAT are:

   PROMPT - Usually prompt $p$g.
   PATH   - The Path line contains the
            directories you want access to
            no matter which directory you're in.

   To load or run a program, enter the program name
on a separate line.  Any DOS commands in
AUTOEXEC.BAT will be executed like a normal DOS
batch file.

   The following example sets the prompt and path,
loads the Doskey program in the DOS directory
switches to the LOTUS directory and runs the 123
program:

         prompt $p$g
         path c:\data;d:\words;e:\budget
         c:\dos\doskey
         cd \lotus
         123



   Manual changes to AUTOEXEC.BAT are done with a
text editor such as the DOS Edit and the Windows
Notepad utilities.  Any word processor that can
import and export ASCII files can also be used.  To
use the DOS Edit program to edit the AUTOEXEC.BAT
file, type:

   cd \               switch to root directory
   edit autoexec.bat  open AUTOEXEC.BAT for editing
       To quit after making changes,
             press Alt F, then X and Enter.


                     Remember!
AUTOEXEC.BAT must be stored in the root directory.


    Your Configuration Files Get Tampered With
Install programs may edit your AUTOEXEC.BAT and
CONFIG.SYS files during installation.  For example,
they may want to add the new directory to the path
or to set an environment variable (see DOS Set).
They made also need to add a new driver.  You are
generally informed that this is being done and
often shown the changes as they are made.  The
original files are usually renamed with a different
extension and left on the disk.

   If you want to delete the application soon after
it was installed, you can rename these files back
to AUTOEXEC.BAT and CONFIG.SYS (after deleting the
current ones).  However, after several software
installations, you may not remember which is which,
and all these previous configuration files may have
little value unless carefully inspected.



DOS backslash (\)
Backslashes are used to represent the root
directory when it precedes the first directory of
file name in a path.  Used elsewhere in the path,
it is a symbol that separates file and directory
names.  See DOS abc's.



DOS Backup/Restore
(For DOS 6 users, see DOS MSbackup.)  Backup and
Restore are external commands that let you back up
your hard disk onto as many floppies as required.
Backup and Restore are not widely used, because you
cannot Restore files onto a different PC that you
backed up from a previous DOS version.  Most people
use the DOS Copy and Xcopy commands or use third-
party backup programs for making backups.


USING THE BACKUP AND RESTORE COMMANDS
To back up all the files in directory WORK on drive
C onto floppies in drive A, type:

          backup c:\work a:


BACK UP AND FORMAT
If you don't have a lot of formatted floppies, you
can format them at the same time you're backing up.
In DOS 3.3 and lower, add /f:

          backup c:\work a: /f

   As of DOS 4.01, Backup automatically runs the
Format program if it finds an unformatted disk.


BACK UP ONLY UPDATED FILES
To back up only those files that have been changed
since the last update, add /m (see Archive
Attribute in DOS Attrib):

          backup c:\work a: /m


BACK UP SUBDIRECTORY FILES TOO
To back up the files in WORK as well as all files
in subdirectories attached to WORK, add /s:

          backup c:\work a: /s


ADDING FILES
When running Backup, existing files on the floppies
are erased.  To add to the disks (keep existing
files), use /a:

          backup c:\work a: /a


   You can mix any of the switches (/s, /m, /f,
etc.); such as:

          backup c:\work a: /m /s


CREATE A BACKUP LOG
Starting with DOS 3.3, the /l switch lets you
create a file containing the names of each file
backed up along with its backup disk number.  If
you don't name the file, BACKUP.LOG will be created
in the root directory of the current drive.  If the
log file exists, file names will be added to the
list.  The following example creates MYLOG in MYDIR
on drive E:

   backup c:\work a: /m /s /l:e:\mydir\mylog



RESTORING FILES
To restore files, you must explicitly state which
files.  To restore all files back into the C:\WORK
directory from the A drive, type:

         restore a: c:\work\*.*

   To restore only EXE files, type:

         restore a: c:\work\*.exe

   To restore all files, including the subdirectory
files, add the /s:

         restore a: c:\work\*.* /s





DOS batch file
A batch file is a file of DOS commands that are
"batch" processed.  That is, each command in a
batch file is executed by DOS until the end of the
file is reached.

   To create a batch file, use Copy Con, a text
editor such as Edlin or Edit or a word processor.
If using a word processor, save your batch file as
an ASCII text file, not as a standard document.
Always include a .BAT extension with your batch
file name.

   The following batch file switches to the E
drive, goes to the PAT directory and runs the
MYPROG program:

         e:
         cd \pat
         myprog


   If the file above was named PAT.BAT in the BATCH
directory on drive C, you would execute it by
typing:

        C:\BATCH>pat


                       Tip!
If you use batch files to launch applications such
as in the example above, make a hard disk directory
called BATCH or BAT and put all your batch files in
it.  Also make sure that the batch files directory
is named in the Path command in your AUTOEXEC.BAT
file (see DOS Path) so that you can execute your
batch files from whichever directory you're
currently in; for example:

          C:\BATCH>pat
          D:\XYZ>pat
          E:\BUDGETS>pat


   If you create a batch file that works with files
in only one directory, then place the batch file in
that directory.  When you want to run it, go to
that directory.


               Stopping a Batch File
To stop a batch file in operation, press Ctrl-C or
Ctrl-Break.


  Ŀ
    The following commands are here for quick   
    reference only.  If you are not an          
    experienced batch file programmer, consult  
    a good book on the subject, such as Kris    
    Jamsa's "DOS Batch File Power" published    
    by SAMS.                                    
  


             Additional Batch Commands
  cls        Clear the screen
  rem        Remarks (documentation)
  ::         Non-displayable remarks (see DOS ::)
  echo off   Turn off display.
  @echo off  Turn off display (3.3 and up).
  echo on    Turn on display.
  echo       Display message; for example,
              echo Press any key to continue.
  call       Call other batch file.
  pause      Stop (wait for keystroke).
  choice     (in DOS 6) more organized method for
              getting user input


             Advanced Batch Commands
  For reference only.  Refer to your DOS manual.
  if not exist filename goto :line
  if not string1==string2 goto :line
  if not errorlevel 0 goto :line
  for %%varname in (files) do command
  %0        - Batch file name.
  %1 - %9   - Input variables.
  %varname% - Variable used with Set.

   Following is an example of the choice batch file
command in DOS 6.  It loads three different
programs depending on receiving A, B or C from the
user.  If A is entered, errorlevel is 1, B is 2 and
C is 3.  IF ERRORLEVEL always tests for >=, which
is why the largest number is tested first.

   choice /c:abc  Run A.  Run B.  Run C.
   if errorlevel 3 goto runC
   if errorlevel 2 goto runB
   :runA
   run program A
   goto end
   :runB
   run program B
   goto end
   :runC
   run program C
   :end





DOS box
The DOS compatibility mode.  When a DOS application
is running under Windows or OS/2, it is running in
a DOS box.  The "box" is actually one instance of
the Intel x86 Virtual 8086 Mode, which simulates an
independent, fully functional PC environment.  See
Virtual 8086 Mode.



DOS Break
Ctrl-C and Ctrl-Break are key commands that stop
the current operation; however, certain functions
such as disk I/O cannot normally be halted.  Break
is a CONFIG.SYS setting that tests the keyboard
more frequently for Ctrl-C and Ctrl-Break.  To
extend Ctrl-C checking, add the following to your
CONFIG.SYS file:

          break=on

   Note that applications can be programmed to
ignore Ctrl-C and Ctrl-Break regardless of the
Break setting.



DOS buffers=
See DOS CONFIG.SYS.



DOS cache
See DOS SmartDrive.



DOS Cd
An internal command that changes the current
directory.  Chdir is an alternate form.  To change
to the DATA directory type:

     C:\ANYWHERE>cd \data

         or type:

     C:\ANYWHERE>chdir \data


   See DOS directories and DOS abc's.



DOS changing directories
See DOS Cd and DOS directories.



DOS Chdir
See DOS Cd.



DOS Chkdsk
An external command that reports free memory and
disk space.  To display memory and disk status,
type:

         chkdsk

   Improperly closed files, caused by rebooting
from a frozen application for example, generate
lost clusters, which are unidentifiable files.
Most of the time, these are temporary files not
worth recovering.  To reclaim these lost clusters,
run Chkdsk with the /f switch.  When you're asked
"Convert lost chains to files?", answering Y for
yes will convert lost clusters to FILE0000.CHK
files, which you can examine.  Answering N will
remove them.  For example:

         chkdsk /f

   To list recovered files, type:

         dir *.chk


                    Important!
Don't go to the DOS prompt (shell out) from within
Windows or any other program and then run the
Chkdsk utility.  You may get invalid results and
possibly destroy data.  See also DOS ScanDisk.



DOS CHKSTATE.SYS
CHKSTATE.SYS is a software driver used by Memmaker
exclusively during its optimization process.  The
line is placed into CONFIG.SYS and then removed
when Memmaker is finished.  See DOS SIZER.EXE.



DOS Choice
An external command starting with DOS 6 that is
used to provide user interaction in a batch file.
It lets you ask a question and obtain a single
character as an answer.

   For example, if you create a batch file to do
three things, you can use Choice to ask which one.
Examine the following:

       choice /c:abc  /n  Do you want A, B or C?
       if errorlevel 3 goto thingc
       if errorlevel 2 goto thingb
       "do thing A here"

       :thingb
       "do thing B here"

       :thingc
       "do thing C here"


   The choices follow the /c: switch.  The answers
are stored in the error level (A in 1, B in 2,
etc.), which is then tested.  If any other
character is entered, the computer beeps and waits.

   The /n supresses the message that would be
displayed following your prompt.  In the above
case, it would be [A,B,C]?

   Note that the error levels must be tested from
high to low order.  The CHOICE.COM file provides
this functionality.



DOS clean boot
See DOS startup options.



DOS Cls
An internal command that clears the screen.  To
clear the screen, type:

           cls





DOS combining files
To combine text files, use the Copy command.  For
example, to combine the files FIRST and SECOND,
creating a new file named COMBINED, type:

         copy first+second combined


   To append SECOND to the end of FIRST, type:

         copy first+second

   After the copy, SECOND still exists as a single
file, and it has also been appended to FIRST.



DOS command history
See DOS Doskey.



DOS COMMAND.COM
COMMAND.COM is the DOS software that displays the
DOS prompt and accepts and executes your typed-in
commands.  If a command interpreter other than
COMMAND.COM is used, it is specified with the Shell
command (see DOS Shell).

   DOS loads COMMAND.COM from the disk at startup.
Part of COMMAND.COM is always resident in memory.
The rest of it, or transient part, may be
overwritten when a program is executed.  When the
program is done, the transient portion is reloaded
into memory.  See DOS Sys.



DOS Comp
An external command that compares two files for
identical content and reports up to 10 mismatches.
In DOS 6, this command is no longer installed,
although it still resides on the DOS 6 Supplemental
Disk.  To compare file RED with GREEN, type:

           comp red green


   Mismatches are reported as follows:

     Compare error at OFFSET AA
     File 1 = BB
     File 2 = BB

  AA = location of characters
  BB = characters (in hex)


   As of DOS 5, these optional switches can be
added to the command:

    /a   Show ASCII characters (not hex)
    /l   Display line numbers (not offset)
    /c   Non case-sensitive compare

   See also DOS FC.





DOS comparing files
See DOS FC and DOS Comp.



DOS compressing files
See DOS DoubleSpace.



DOS compression ratios
To see the compression ratios of your DoubleSpace
files, use the /c switch with the Dir command to
list each file's ratio and an average for the
selected group.  The following example displays
ratios for all .EXE files:

             dir *.exe /c





DOS Comspec
A DOS environment variable that holds the path to
COMMAND.COM.  See DOS COMMAND.COM and DOS Set.



DOS CONFIG.SYS
CONFIG.SYS is a configuration file made up of DOS
commands that DOS looks for in the root directory
upon startup.  It is used to load drivers and
change system settings.  Adding a new peripheral to
a DOS computer usually requires installing the
driver program to make it operate.  The install
program that comes with the peripheral often does
this for you by copying the driver to your hard
disk and modifying the CONFIG.SYS file to activate
it upon startup.

   Manual changes to CONFIG.SYS are done with a
text editor such as the DOS Edit and the Windows
Notepad utilities.  Any word processor that can
import and export ASCII files can also be used.  To
use the DOS Edit program to edit the CONFIG.SYS
file, type:

   cd \               switch to root directory
   edit config.sys    open CONFIG.SYS for editing
       To quit after making changes,
             press Alt F, then X and Enter.


   Besides activating drivers, there are several
DOS commands that can be executed in CONFIG.SYS
(see below).  CONFIG.SYS gets more complicated as
the number of devices in your computer increases.
Most users never have to touch the file, but power
users are always tweaking it, as much for curiosity
as for performance increases, which may or may not
be all that significant.  To become a master at
configuring the DOS configuration files CONFIG.SYS
and AUTOEXEC.BAT, you will need to read several
good books on DOS and be willing to go through
trial and error.


 Common
 Commands            Purpose
 DEVICE    Names a driver to be loaded.
 FILES     Files open at one time (8-255).  Default
            is 8, but this is often set to 20-40.
            Some apps open a lot of files.
 BUFFERS   528-byte areas of RAM reserved for input
            and output (1-99).  Default is usually
            15, but this is often set to 20 or 30.
            The more buffers, the faster the I/O.
            /x switch in 4.01 puts buffers in EMS.
 LASTDRIVE Last drive letter (see DOS Subst).

   Look up DOS Loadhigh for storing drivers in high
memory in DOS 5 and up.

   Following is an example of the contents of a
CONFIG.SYS file for a 386 and higher PC:

    device=c:\dos\himem.sys
    device=c:\dos\emm386.exe ram
    device=c:\dos\ansi.sys
    device=c:\mouse\mouse.sys
    files=30
    buffers=40
    dos=high,umb


  Common
  Drivers              Purpose
 ansi.sys      Screen and keyboard control.
 display.sys   Supports code-page switching.
 driver.sys    Identifies 3rd & 4th floppy and
                allows copying from/to same drive.
 mouse.sys     Mouse driver.
 printer.sys   Code-page support for printers.
 himem.sys     Extended memory (XMS) manager.
 emm386.exe    386 EMS manager.
 qemm386.sys   Quarterdeck's 386 EMS manager.
 ramdrive.sys  RAM disk (extended or EMS memory).
 smartdrv.sys  Disk cache (extended or EMS memory).





DOS Copy
An internal command for making duplicate disk
files.  The command format is:

               COPY  FROM  TO


COPY TO/FROM FLOPPIES
  copy a:*.* b:     all A files to B
  copy b:*.* a:     all B files to A
  copy b:sales a:   SALES file in B to A


COPY FROM FLOPPY TO CURRENT HARD DISK DIRECTORY
  copy a:sales      SALES file on A
  copy a:*.*        all A files


COPY FROM CURRENT HARD DISK DIRECTORY TO FLOPPY
  copy sales b:     SALES file in  to B
  copy *.* b:       all files to B
  copy . b:         shortcut of above


COPY FROM CURRENT DIRECTORY TO ANOTHER DIRECTORY
  copy filex \text copy FILEX to TEXT directory

  copy *.* \text   all files to TEXT directory
  copy . \text     shortcut of above


COPY FROM ANOTHER DIRECTORY INTO CURRENT DIRECTORY
  copy \abc\x.bat   X.BAT from ABC directory

  copy \abc\*.*     all files from ABC
  copy \abc         shortcut of above


COPY AND RENAME AT THE SAME TIME
The following example duplicates and renames a PC
Paintbrush file within the same directory:

      copy logo.pcx logo2.pcx


YOU CAN VERIFY YOUR COPY
To be extra sure that the copy is correct, add the
/v switch to compare the new file with the old
file; for example:

      copy *.* a: /v


                     Remember!
There's less typing if you're in the directory you
want to copy to.  For example, from any directory,
you could issue:

   D:\ANYWHERE>copy a:*.* c:\budgets\1992


   But, if you're already in C:\BUDGETS\1992, the
TO is implicit:

        C:\BUDGETS\1992>copy a:*.*



            LOOK UP THESE COPY COMMANDS
COPY only copies files, but XCOPY copies both files
and subdirectories and creates the directory names
on the target disk.

DISKCOPY makes exact copies of floppy disks and
formats them at the same time.

REPLACE is great for backup and copies only files
that have been changed.





DOS Copy con
An internal command for creating a quick batch
file.  For example, to create the WRITE batch file,
type:

            copy con write.bat

   After pressing Enter, you'll get a blank line.
Type your text and press Enter to end the line.
When done, press F6 (ctrl-Z), then press Enter.

   Copy Con works a line at a time.  You can't go
back and change lines, but you can use backspace to
delete characters on the same line.



DOS Ctty
An internal command that redirects the keyboard and
screen to the serial port.  This is used to connect
a remote keyboard to a PC.

      ctty aux     change to serial port
      ctty con     restore keyboard and screen





DOS data recovery
See DOS Recover, DOS Unformat, DOS Undelete and
"There's More to Mirror" in DOS Mirror.



DOS Date
See DOS Time/Date.



DOS Debug
An external command that performs a variety of
machine language functions.  Debug is used to edit
memory, executable files, input/output ports,
assemble small programs and perform hex arithmetic.
To load Debug, type:

          C:\>debug      load Debug
          -              Debug prompt (-)

   Some simple Debug commands follow for reference
only.  See your DOS manual for details.

 Commands             Purpose
   ?            Online help (as of DOS 5).
   q            Quit.

   d cs: 100    Display 128 bytes of RAM at 100h in
                 the CS segment (current program).
   d            Display next 128 bytes.

   h xxxx yyyy  Hex math.  X and y are hex numbers.
                 Results are x+y  x-y.
   g=C800:5     Go to address C800:5





DOS Defrag
Starting with DOS 6, Defrag is a utility that
defragments the hard disk.  Some users run a
defragmenter every day, others every couple of
months.  It's up to you.  Defragmenting will
improve the performance of applications in which
you continuously update the data.  If done
routinely, it will help reduce wear and tear on the
hard disk.  Follow this procedure to defragment
your hard disk:

  1. Delete all unnecessary files on the disk.
  2. Quit all running programs, including Windows.
  3. Check for lost clusters by typing chkdsk /f.
     If prompted "Convert lost chains to files?",
       answer Y.
  4. Run Defrag by typing defrag.



DOS Del
An internal command that erases a file from the
disk.  DOS doesn't actually remove the file, so
after you delete a file, you may be able to
undelete it if you have DOS 5 or later or if you
have an undelete utility program.  See DOS
Undelete.


DELETING FROM THE CURRENT DIRECTORY
To delete a file named OLD.TXT in your current
directory, type:

        del old.txt   or   erase old.txt


DELETING ALL FILES IN YOUR CURRENT DIRECTORY
To delete ALL files in your current directory, type
the following command.  You'll be prompted with
"Are you sure?"  Type y to perform the operation.

           del *.*   or   erase *.*


DELETING SELECTED FILES IN YOUR CURRENT DIRECTORY
To delete all DOC files in your current directory,
type:

          del *.doc  or   erase *.doc


DELETING A FILE FROM A FLOPPY DISK
To delete the SALES.DBF file on your floppy disk,
type:

      del a:sales.dbf      on disk A:

      del b:sales.dbf      on disk B:


DELETING ALL FILES FROM YOUR FLOPPY
To delete all files on a floppy disk, type the
following commands and when prompted "Are you
sure?" type y to confirm:

     del a:*.*     ALL files on A:

     del b:*.*     ALL files on B:


         A Shortcut for Blanking Floppies!
If you delete all files on floppies often as many
people do, you can create a batch file that saves
you a little time.  After entering del a:*.*, it
takes a few seconds to get the "Are you sure?"
confirmation, because it takes time to get the
drive spinning.

   You can create a batch file that deletes all
files and confirms at the same time.  For example,
using a text editor, create a file called
DELETEA.BAT or some similar name.  Don't be cute
and make this file name short.  Typing this name
should always be deliberate.

   Enter the following in the file and save it.
The | is the shift-backslash key.

             echo y | del a:*.*


   When you type deletea to run the batch file, all
files will be erased on floppy drive A: without
your having to confirm it.  You can then create a
DELETEB.BAT file for drive B:.  What you're
actually doing here is piping the "yes"
confirmation to the delete command.  For more on
this, see DOS filters & pipes.

   It's not a good idea to create this kind of
batch file to delete files on your hard disk.  Type
in the  del *.*  and confirm it.  The prompt makes
you think one last time.  While you can undelete
files in DOS 5 and later versions, you can just as
well forego the pleasure.  For more on batch files,
see DOS batch file.


                       Oops!
If you ever delete a file by mistake, and you must
recover it, do the following:

   In DOS 3.x and 4.01:

   1. Stop!
   2. Turn the computer off.  If you must save
       what you're working on, save it to a
       different disk drive.
   3. Get a file recovery program and follow its
       instructions.


   In DOS 5 and 6:

   Just type the following and follow the prompts:

                     undelete


   See DOS Undelete.





DOS Deltree
Starting with DOS 6, an external command that
removes directories.  It differs from the Rd
command in that the directories do not have to be
empty.  All files contained in the directory and
all subdirectories attached to that directory as
well as any files contained in them will be
deleted.  Like the Rd command, you must not
currently be in the directory that you want to
delete.  For example, to delete the C:\BUDGETS
directory, you could type:

   C:\>deltree budgets      from the root
   C:\WORK>deltree budgets  from a non-related
                             directory

   If BUDGETS contained subdirectories; for
example, \BUDGETS\1992 and \BUDGETS\1993, those
subdirectories and files will also be deleted.

   To delete everything on your hard disk, go to
the root directory and type:

      C:\>deltree *.*


   Note: Unlike most DOS commands, Deltree can be
used with previous versions of DOS.



DOS device names
DOS device names are reserved names for common
input and output devices.  See DOS redirection, DOS
Sort and DOS Dir.

  Reserved name   Device
  AUX             First connected serial port
  PRN             First connected parallel port
  COM1 thru COM4  Serial ports (modem, mouse, etc.)
  LPT1 thru LPT3  Parallel ports (printer)
  CON             Keyboard and screen
  NUL             Dummy (testing purposes)





DOS device=
See DOS CONFIG.SYS.



DOS Devicehigh
See DOS Loadhigh.



DOS Dir
An internal command for displaying the names of
files within a single directory.  To list all file
names in the current directory, type:

                   dir


   To display only files with an .EXE extension,
type:

         dir *.exe  or   dir .exe


   See DOS wild cards for more on selecting file
names.

   A Dir list contains the following information
(see example below):

 Line 1  Drive name.  "Has no label" means
          it hasn't been named.
 Line 2  Drive serial no. (DOS 4.01 and up)
 Line 3  Current directory name.
 Line 4  The "." line represents the entire current
  directory and shows the creation date.  Let it
  remind you of the shortcut for "*.*".
 Line 5  The ".." line means the directory is
  attached to a higher level (they all are except
  for the root).
 Lines 6, 7 & 9  Name, extension, size, creation
  date/time of each file selected.
 Line 8  Name of subdirectory attached to this
  directory.


Volume in drive C has no label         Line 1
Volume Serial Number is NNNNNNNNN      Line 2
Directory of D:\DIRNAME                Line 3

.             <DIR>     MM-DD-YY  H:MM Line 4
..            <DIR>     MM-DD-YY  H:MM Line 5
NAME     EXT     SIZE   MM-DD-YY  H:MM Line 6
NAME     EXT     SIZE   MM-DD-YY  H:MM Line 7
NAME          <DIR>     MM-DD-YY  H:MM Line 8
NAME     EXT     SIZE   MM-DD-YY  H:MM Line 9


              Important Variations

LIST ONLY DIRECTORIES
To display subdirectory names attached to the
directory you're in, type:

                   dir *.


   Starting with DOS 5, use the /ad switch to list
directories.  Only directories will be displayed,
whereas with the DIR *. example above, depending on
DOS version, you may also get file names that do
not have extensions.

                  dir /ad


WIDE DISPLAY
To display names across the full width of the
screen rather than in one column, add /w:

                   dir /w


PRINT THE LIST
To print a Dir list, redirect the output to the
printer.  The following example prints the list
rather than displaying it.  Add the > prn to any of
these examples to print instead of display.

                  dir > prn


ONE SCREENFUL AT A TIME
To display a screenful at a time and pause, add the
/p switch:

                   dir /p


LIST FILES ALPHABETICALLY (Before DOS 5)
To list file names alphabetically no matter what
DOS version is installed in your machine (DOS 2.0
and up), you can pipe the output to the Sort
external command as follows:

              dir *.exe | sort


LIST FILES ALPHABETICALLY (As of DOS 5)
To list file and directory names alphabetically,
type:

   dir /o    all subdirectories 1st, files 2nd
   dir /on   subdirectory and file names mixed


   Alphabetically by extension:

     dir /oe   from A to Z
     dir /o-e  from Z to A


   Numerically by file size:

     dir /os    from smallest to largest
     dir /o-s   from largest to smallest


   In chronological order:

     dir /od    from earliest to latest date
     dir /o-d   from latest to earliest date



SEARCH FOR DUPLICATE FILE NAMES (As of DOS 5)
You can use Dir to find duplicate file names on the
hard disk.  For example, to list all directories in
which the file X.BAT is located, go to the root
directory and type:

         C:\>dir x.bat /s


LOWER CASE OPTION (As of DOS 5)
To display all names in lower case, add /l:

        dir /l


DISPLAY FILE ATTRIBUTES (As of DOS 5)
Use the /a switch to display the various attributes
that can be assigned to a file:

    dir /ar    read only files
    dir /ah    hidden files
    dir /aa    files ready for archiving
    dir /as    system files


CHANGE DIR COMMAND DEFAULTS (As of DOS 5)
Use can change the defaults for the Dir command by
setting the DIRCMD environment variable.  The
following example sets alpha order and a screenful
at a time:

     set dircmd=/o /p    change defaults
     set                 view current settings
     set dircmd=         restore defaults

   Add the set dircmd= line in your AUTOEXEC.BAT
file to change defaults each time you start.


SHOW COMPRESSION RATIOS (As of DOS 6)
To see how effective your DoubleSpace compression
is, see DOS compression ratios.





DOS Dircmd
An environment variable that lets you set the
default options for the Dir command so you can
always get directory lists to display and print the
way you want them.  The explanation is at the end
of the DOS Dir definition (the definition before
this one).



DOS directories
Directories are simulated file drawers on a disk.
To understand directory basics, look up DOS abc's.


         Directories and Subdirectories
DOS directories are hierarchical in structure.  The
starting point is the root directory.  In fact,
when several people use the same computer, the
"directory tree" looks like an organization chart:

                    root
       Ŀ
     karen    sam         pat    robin
       
   Ŀ
  budget  text

   A subdirectory is a directory that is
subordinate to (below, or attached to) another
directory like BUDGET and TEXT above.  Since all
directories are below the root directory, all
directories are technically subdirectories.  The
two terms become intertwined.  Don't worry about
this.

   More importantly, don't set up too many levels
in the hierarchy or you'll drive yourself nuts
trying to manage them at the DOS prompt.  However,
if you have a menu system that let's you point to
the directory you want, you can manage several
levels of directories more easily.


                 A Real Bummer
The hardest thing about DOS commands is creating
the proper path name to the files you want to work
with.

   It's tricky because the structure for naming the
path isn't clearcut.  The culprit is the backslash
symbol (\), which means two entirely different
things depending on its position in the path.

   The first time it's used, it stands for root
directory.  The second and subsequent times it's
used, it's a symbol that separates file and
directory names.

   The following commands for creating, removing
and changing directories will show you many ways
path names are used.  There are plenty of examples
that follow:


         Creating a Stand-alone Directory
A stand-alone directory is one attached to the
root.  To create stand-alone directory KAREN, type:

   C:\ANYWHERE>cd \    go to the root
   C:\>md karen        make directory off the root
   C:\>                you're still in the root

   To go to that directory, type:

   C:\>cd karen       change directories
   C:\KAREN>          prompt changed to Karen


                       Note!
Directories are named the same as files, with a
name up to eight characters and an optional
extension of up to three.  See DOS file names.


              Creating a Subdirectory
To create a subdirectory called BUDGET that is
located within the KAREN directory, type:

 *     C:\ANYWHERE>cd \karen    go to KAREN
       C:\KAREN>md budget       make subdirectory
 **    C:\KAREN>cd budget       go to budget
       C:\KAREN\BUDGET>         prompt has changed

   * Going to KAREN requires a backslash in front
of KAREN, because the first backslash means ROOT
directory, and KAREN is off the root.
** Going to BUDGET does not use the backslash,
because BUDGET is off KAREN, not off the root.
More on this in a moment.


                    Also Note!
The above methods were chosen for demonstration,
because the syntax is the same for creating both
stand-alone directories and subdirectories.
However, you should know that you can create both
types of directories no matter which directory
you're in.  For example, from the ANYWHERE
directory, you could have created KAREN by typing
md \karen  being sure you have the backslash in
front of KAREN.  You could then attach the BUDGET
subdirectory to KAREN with md \karen\budget.


               Removing a Directory
First, be sure all files in the directory have been
erased.  Second, move back a level to the directory
before it.

   The following example switches to the KAREN
directory, deletes all files, moves back one level
and removes the KAREN directory:

      C:\>cd karen      go to KAREN
      C:\KAREN>del *.*  delete all files
      C:\KAREN>cd ..    move back one level
      C:\>rd karen      remove KAREN directory


                     Remember!
1. You can't be in the directory you're deleting.
   Go to the level before it.

2. If you're using DOS 5 or an earlier version, you
   can't delete a directory that's not empty.  In
   DOS 6, you can with the use of the Deltree
   command.



               Switching Directories
The CD (change directory) command means go to
another directory.  What actually changes is the
DOS prompt, which displays the name of the
directory you've switched to.

   Suppose you have three subdirectories under the
PLANS directory:

              C:\PLANS\1991
              C:\PLANS\1992
              C:\PLANS\1993

   If you're in the 1991 directory and you want to
go to the 1992 directory, you have to state the
path starting at the root:

      C:\PLANS\1991>cd \plans\1992
      C:\PLANS\1992>


   Another way is to type:

       C:\PLANS\1991>cd ..    back up one level
**     C:\PLANS>cd 1992       go to 1992
       C:\PLANS\1992>

**Note: When going from PLANS to 1992, you don't
use the backslash (\), because 1992 is subordinate
to PLANS, not the root.


   Let's examine this some more.  In the command:

              cd \plans\1991

   The first \ means ROOT.  The second \ separates
one directory name from another.  Therefore, if
you're in PLANS already, you cannot type:

           C:\PLANS>cd \1991

   You'll get an "Invalid directory" message,
because 1991 is not off the root.

           \1991 means root 1991

   Using the PLANS directories again:

              C:\PLANS\1991
              C:\PLANS\1992
              C:\PLANS\1993

   Only the first example below is correct:

 correct   C:\PLANS>cd 1991   1991 is off PLANS
 no good   C:\>cd 1991        You're in the root
 no good   C:\>cd \1991       1991 is not off root



             Switching Between Drives
When switching between directories on different
drives, you must switch drives first.

   For example, to switch from C:\PLANS\1991> to
D:\BUDGETS>, you would type:

     C:\PLANS\1991>d:   switch drives first
     D:\>cd budgets     then change directories
     D:\BUDGETS>        prompt has changed


   Think of drives as buildings and directories as
floors.  You can't get to the 3rd floor of the
college if you're on the 2nd floor of the high
school by simply switching floors.  You have to
leave the college and go to the high school first.


          Using Paths with Other Commands
Drive letters ARE NOT used with the CD command.

   Drive letters ARE used with all other commands
whenever the drives are not implicit.  For example,
to copy the SALES worksheet from C:\PLANS to
D:\BUDGETS, you would type:

 E:\ANYWHERE>copy c:\plans\sales.wk1 d:\budgets


   In the above example, notice that, because
you're in drive E, both FROM and TO drive letters
must be used (C: and D:).

   Also notice that the SALES file name is simply
added to the end of the path, separated by a
backslash.

   If you were already in C:\PLANS, you would only
need to reference the file name:

      C:\PLANS>copy sales.wk1 d:\budgets






DOS directory rules


               DIRECTORY RULE #1
When going to a directory on a different drive,
change drives first, then change directories.


               DIRECTORY RULE #2
The backslash represents the root directory.  It is
also used as a separator symbol between directory
and file names.


               DIRECTORY RULE #3
When using the CD command to go to a directory on
the same or previous level, the path name must
begin with the root (\).





DOS disk cache
See DOS SmartDrive.



DOS disk recovery
See DOS Recover, DOS Unformat, DOS Undelete and
"There's More to Mirror" in DOS Mirror.



DOS Diskcomp
An external command that compares two floppy disks
track by track and reports the side and track
number if it finds a mismatch.

      diskcomp a: b:   two identical drives
      diskcomp a:      one drive


   On one-drive compares, you'll be prompted to
insert the source and target diskettes a few times.



DOS Diskcopy
An external command that makes an exact copy of a
floppy disk.  Disk types MUST BE THE SAME.  You
can't Diskcopy a 720KB disk onto a 1.44MB disk.

   If the target disk is unformatted, Diskcopy will
format it.

      diskcopy a: b:    two identical drives
      diskcopy a: a:    one-drive

   On one-drive copies, you'll be prompted to
insert the source and target diskettes a few times.



DOS Dos
A CONFIG.SYS setting as of DOS 5 that (1) allows
part of DOS to be loaded into the HMA area (1024-
1088K), and (2) allows drivers and TSRs to be
loaded into the UMA (640-1024K) region.

   To load part of DOS into the HMA, HIMEM.SYS (or
some other XMS driver) must precede the dos=
command in CONFIG.SYS, for example:

    device=himem.sys     XMS driver
    dos=high             load DOS high


   To allow drivers and TSRs to be loaded into
unused memory blocks (UMBs) in the UMA, both
HIMEM.SYS (or some other XMS driver) and EMM386.EXE
(or some other upper memory provider) must precede
the dos= command, for example:

  device=himem.sys           XMS driver
  device=emm386.exe noems    UMA provider
  dos=umb                    allow UMA to be used


   Both functions can be activated on the same line
with
               dos=high,umb


   See DOS Loadhigh, DOS HIMEM.SYS and DOS
EMM386.EXE.





DOS Doskey
An external command starting with DOS 5 that
provides command history and macros (typed-in
commands stored for later use).  The command buffer
(reserved space) is 512 bytes long unless you
specify otherwise.  Three examples for loading
Doskey follow:

    doskey                 512 byte buffer
    doskey /bufsize=1000   1K buffer
    doskey /bufsize=256    minimum size

   Use Up and Down Arrow to move through command
history, and press Page Up and Page Down for the
oldest and most recent command.  Doskey uses these
additional key commands:

       Key       Function
        F7  Display command history
    Alt-F7  Clear command history
   Alt-F10  Clear macros
        F9  Recall command by number
  Ctrl <--  --> Cursor previous/next word
  Home/End  Cursor beginning/end line
       Esc  Clear line
       Ins  Insert mode for this line
F1, F3 and F6 work as usual.  See DOS key commands.


CREATING MACROS
Doskey macros are useful for shortening phrases
that are hard to type; for example, suppose you
often copy the file D:\PKWARE\PKUNZIP.EXE to
different directories or disks.  You could create a
macro named PK as follows:

   doskey pk = copy d:\pkware\pkunzip.exe $1

   The $1 creates a blank field for data entry.
Now that the macro is created, to copy PKUNZIP.EXE
to the B drive, you would type:

            pk b:


   Entering the command above converts the macro
into the following command (the b: replaces the
$1):

    pk = copy d:\pkware\pkunzip.exe  b:


   To see the macros you've created, type:

            doskey /macros


   Doskey macros last for only the current session.
If you save them in a batch file and add the word
DOSKEY in front of each one, you can execute the
batch file and recreate the macros in the next
session.  To store your macros in MYMACRO.BAT,
type:

       doskey /macros > mymacro.bat

   In order to make the resulting file a command
file, you have to type the word DOSKEY at the
beginning of each line.



DOS DoubleSpace
DoubleSpace is a realtime compression capability
built into DOS 6 (but removed in DOS 6.2) that
increases the disk's storage capacity generally by
a factor of two.  The actual compression obtainable
depends on the data being stored.  DOS 6 does not
compress your drives automatically.  You must run
the DoubleSpace program to do it.

   To compress your hard disk, type dblespace.  The
first time you run DoubleSpace, you'll have a
choice of Express or Custom Setup.  To compress
your C: drive including all existing files, select
Express Setup.  To compress another drive or to
compress part of your C: drive leaving your
existing files uncompressed, select Custom Setup.

   The compressed drives that DoubleSpace creates
are actually files with names such as DBLSPACE.000
and DBLSPACE.001 that reside on an uncompressed
drive as hidden "compressed volume files" or CVFs.
The uncompressed drive, known as the host drive, is
either the C: drive if you did not compress all of
it or some other drive that DoubleSpace creates.

   If you're curious, you can view the hidden CVFs
in the uncompressed host drive by typing dir /ah.
However, do not restore them to normal status or
tamper with them in any manner!  When viewing them,
you will notice DBLSPACE.BIN.  This program file is
loaded at startup and gives DOS access to the
compressed DoubleSpace disks.

   To review the status of your compressed drives,
to change them or to make new ones, type dblspace
and select the appropriate menu options.

   You can see how effective the DoubleSpace
compression is on your files by using the Dir
command (see DOS compression ratios).


             DoubleSpace Was Fleeting!
Due to a patent infringement lawsuit won by Stac
Electronics, publisher of the Stacker compression
product, Microsoft is no longer offering this
feature in DOS.  As of MS-DOS Version 6.21,
DoubleSpace is not included.  As of MS-DOS 6.22, a
different compression technology called DriveSpace
is included.



DOS Dozen
Following are the 12 DOS commands that let you do
almost everything.

           The DOS Dozen (tm)
   format  Initialize a floppy
   dir     List file names
   del     Remove a file
   rename  Change names
   type    Display a text file
   xcopy   Copy files and directories
   copy    Copy files
   md      Make directory
   cd      Go to a directory
   rd      Remove directory
   chkdsk  Test for corrupted files
   cls     Clear screen






DOS drive identification
DOS drives are identified with a letter and colon.

       A: First floppy
       B: Second floppy
       C: Main hard drive
       D: Second hard drive, second partition
           within the main hard disk or some
           other device such as a CD-ROM drive.
           Drive letters E: through Z: also used.

   To switch drives, type drive letter and colon;
for example, to go to drive D, type:

            C:\>d:    switch drives
            D:\>      prompt has changed





DOS DRIVER.SYS
DRIVER.SYS is a driver used to add newer devices
(typically floppy disks) to older PCs that did not
originally support them.  It's also used to assign
a second drive letter to a single drive to allow
you to copy to and from the same drive.  The
following codes are used to define drives and drive
types:


 Drive /d:     Factor /f:      Switches     Default

 0 - First     0 -  360KB   /h: Heads (1-99)    (2)
 1 - Second    1 -  1.2MB   /s: Sectors (1-99)  (9)
 2 - Third     2 -  720KB   /t: Tracks (1-999) (80)
 3 - Fourth    7 - 1.44MB   /c  Change line support
 etc.          9 - 2.88MB   /n  Nonremovable device

   The following lines in CONFIG.SYS add support
for a third floppy disk:

 device=driver.sys /d:2 /f:0 /t:40     360KB
 device=driver.sys /d:2 /f:1 /s:15     1.2MB
 device=driver.sys /d:2 /f:2           720KB
 device=driver.sys /d:2 /f:7 /s:18    1.44MB
 device=driver.sys /d:2 /f:9 /s:36    2.88MB


   The following line creates a second "logical"
drive for a 1.2MB A: drive.  If drive C was the
last drive letter, this CONFIG.SYS line will create
drive D:, which references A:.

  device=driver.sys /d:0 /f:1 s:15


  If you type:

              copy a:*.* d:


   DOS will inform you when to switch disks, and
you can Copy or Diskcopy to and from the same
drive.


                       Note!
DRIVER.SYS differs from Drivparm as it will always
make the device the highest drive letter.  For
example, if a 3.5" drive is added to a PC with an
A: and C: drive, DRIVER.SYS will assign it drive D:
rather than B:.



DOS Drivparm
A CONFIG.SYS command that redefines the current
settings for a device and maintains the same drive
letter.  The following codes are used:


 Drive /d:     Factor /f:     Switches

 0 - First    0 -  360KB    /h: Heads (1-99)
 1 - Second   1 -  1.2MB    /s: Sectors (1-99)
 2 - Third    2 -  720KB    /t: Tracks (1-999)
 3 - Fourth   5 - Hard disk /c  Change line support
 etc.         6 - Tape      /n  Nonremovable device
              7 - 1.44MB
              8 - Read/write optical disk
              9 - 2.88MB floppy


   The following line in CONFIG.SYS would define a
tape unit on drive B: that writes 10 tracks with
128 sectors per track:

     drivparm=/d:1 /f:6 /h:1 /s:128 /t:10


                       Note!
To add a device and create a new drive letter, see
DOS DRIVER.SYS.  Also, Drivparm should not be used
experimentally.  Get the right specs before you
proceed.



DOS duplicate file names
If you have DOS 5 or later, you can use the Dir
command with the /s switch to find duplicate file
names on the hard disk.  For example, to list all
directories in which the file X.BAT is located, go
to the root directory and type:

         C:\>dir x.bat /s


   If you have a version of DOS previous to 5, you
have to use a third-party program such as Norton's
File Find (FF.EXE) utility.



DOS Editor
The DOS Edit program is a full-screen text editor
starting with DOS 5 for creating ASCII text files
(batch files).  To create or edit a file, type edit
followed by the name of the file.  For example, to
edit AUTOEXEC.BAT, type:

             edit autoexec.bat


   DOS Editor is easy to use and help is online.
Use the Arrow keys to move around.  Press Alt-F for
the File menu and select Exit when you're done.


                       Note!
You must have the QBASIC.EXE program in your DOS
directory to run the DOS Editor (EDIT.COM).

   For DOS versions previous to 5, see DOS Edlin.



DOS Edlin
A very archaic text editor that comes with every
version of DOS.  However, as of DOS 6, it is no
longer installed, although it resides on the DOS 6
Supplemental Disk.  It allows only one line to be
edited at a time.  Starting with DOS 5, use the
full-screen editor program (see DOS Editor).

   To create or edit a file, type edlin followed by
the name of the file.  For example, to edit
AUTOEXEC.BAT, type:

         edlin autoexec.bat


   The screen will display "End of input file"
followed by the Edlin asterisk prompt ("*").
Press L and Enter to list the file's contents.

TO EDIT A LINE
Type the line number and press Enter.  Press Right
Arrow to bring one character at a time into view,
or press F3 to restore the whole line.  When you're
done editing the line, press Enter for the "*"
prompt.  Press Enter again for the next line.
Ctrl-C cancels changes to the current line.

TO INSERT TEXT
Type i to insert text in front of the current line,
which is marked with an asterisk; for example: 3:*.
To change to a different line, type the line number
and press Enter.  After typing new text, press
Enter to end the line.  Then press Ctrl-C to end
insert mode or keep typing more text.

TO QUIT
At the "*" prompt, press e and Enter.


               Basic Edlin commands
 L   List contents (for specific lines, type:
      start,stop L; for example: 5,25 L).
 i   Insert at current line. Ctrl-C ends
 #i  Insert at end of file.  insert mode
 n   Line number to edit.
 nd  Delete line (for example, 5d deletes line 5).
 q   Abandon edit.
 e   End Edlin.
 r   Search/replace. (start,stoprsearch<F6>replace)
      For example:  1,20rBlue<F6>Red  changes
      all Blue to Red in lines 1 to 20.
      F6 enters a Ctrl-Z.

Ctrl-V[ Insert an escape character.





DOS EMM386.EXE
Starting with DOS 5 and Windows 3.0, EMM386.EXE is
an expanded memory manager (EMM) for 386s and up,
which is software that converts extended memory
into EMS memory.  It also allows TSRs and drivers
to be stored in the upper memory area (UMA) between
640K and 1M.  It is activated with a statement in
the CONFIG.SYS file.  The HIMEM.SYS driver must
also be activated before EMM386.EXE:

        device=himem.sys
        device=emm386.exe


   To provide access to the UMA, either the RAM or
NOEMS parameters must be added:

      device=emm386.exe ram      UMA and EMS
      device=emm386.exe noems    UMA only


   The default amount of memory used is 256K, but
you can allocate from 16 to 32768K, for example:

     device=emm386.exe 1300 ram


   For DOS 6 Users: The EMM386.EXE that comes with
DOS 6 can dynamically convert extended memory into
EMS memory when an application requires it.  To
free up all of extended memory until some of it is
required for your EMS application, type:

     device=emm386.exe min=0 ram



   EMM386.EXE is an executable program, which can
be run after it has been initialized in order to
change settings.  For example, you can turn off EMS
memory management off by typing:

           emm386 off

           emm386 on      turn it back on





DOS environment
The DOS environment is a reserved area in DOS for
holding values used by DOS and other applications.
The values stored in this area are called
"environment variables" and are created with the
Set command (see DOS Set).



DOS Erase
See DOS del.



DOS error messages
There are hundreds of error messages in DOS.
Messages that generally occur more frequently are
explained below:


  Access denied
The file you are deleting is protected.  See DOS
Attrib.


  Bad command or file name
Means that DOS does not understand the command you
entered, or it cannot find the program you asked it
to run.


  Data error reading drive X
Means that an area of the disk is unreadable.
Press R to retry.  Most likely, you'll have to
press A to stop (abort).  If the data or program is
critical and there's no backup, use a utility
program to try to reconstruct the damaged area.
See DOS Recover.


  Duplicate file name or file not found
Means that you are referencing a file that does not
exist or that you are renaming a file to a file
name that already does exist.


  Exception error 12
Means that DOS does not have enough room to handle
hardware interrupts.  Increase the number of stacks
in the STACKS= command in the CONFIG.SYS file (see
DOS Stacks).


  File Not Found
Means DOS cannot locate the file you have
specified.  Use the Dir command to check its
spelling.  It may be also be in another directory.


  General failure reading drive X
  Abort, Retry, Fail?
Usually means that an unformatted floppy is being
used.  Press A to Abort, format the floppy and try
again.  You'll also get this if you try to read a
high-density disk in a low-density drive.  High-
density disks require high-density drives.


  Incorrect DOS Version
Means that the command you are using belongs to
another version of DOS.  Somehow an earlier or
later version of a command is on your hard disk.
Commands from one DOS version often do not work in
other versions.


  Internal Stack Failure
Means that DOS has gotten completely confused.
Turn off the computer and restart.


  Invalid directory
Means that you entered the name of a directory that
does not exist.


  Invalid drive specification
If you get this message on a valid drive such as
C:, it may mean that your hard disk has become
corrupted.  See DOS Mirror.


  Invalid file name or file not found
You have probably used an invalid character in a
DOS file name, or you have used wild cards when
they are not applicable.  For example, type *.*
will produce this error, because you cannot Type
more than one file at a time.


  Invalid media type
DOS doesn't recognize the format of the drive being
referenced.  This means that the disk has been
corrupted in some manner and is not readable.  You
will also get this message if you low-level
formatted a new disk, performed the Fdisk
procedure, but forgot to high-level format it with
the Format command.


  Invalid parameter
Means DOS doesn't understand the command line.  It
indicates that a switch is used incorrectly.  If
you're typing path names, be sure to use a
backslash (\), not a forward slash (/).  The
forward slash is used to enter parameters (see DOS
switch and DOS abc's).


  Non-system disk or disk error
  Replace and press any key when ready
Usually means there's a non-bootable floppy in
drive A.  The computer looks for DOS on a floppy
before it looks for DOS on the hard disk.  If an
ordinary floppy is in drive A at startup, it causes
this error.  Remove the disk and press any key.


  Not ready reading drive X
  Abort, Retry, Fail?
Means the drive door is left open, or the floppy
disk is not in the drive.  Either put the
appropriate floppy disk in the drive or close the
drive door (turn lever) and press R.

   To switch to another drive, press F, and type in
the drive letter you want to go back to when you
get the "Current drive is no longer valid>"
message.  In DOS versions prior to 4.0, type I for
Ignore rather than F for Fail.


  Not ready writing device PRN
  Abort, Retry, Fail?
Means the printer is turned off or unavailable.
Press A to cancel, or turn the printer on and press
R.  You might also check the cable connection to
the printer.


  Packed file is corrupt
See DOS Loadfix.


  Path not found
Means that you entered an invalid path name.  See
DOS Path.


  Stack overflow
Means that DOS does not have enough room to handle
hardware interrupts.  Increase the number of stacks
in the STACKS= command in the CONFIG.SYS file (see
DOS Stacks).

   You can also get this message when other things
go haywire; for example, a bad expansion board or
one that isn't seated properly in the slot can
cause erratic signals eventually leading to this
message.


  Write protect error
Means that the floppy disk has been protected and
data cannot be recorded on it.  Either unprotect it
or use another disk.  See file protection.



          End of DOS error messages





DOS Exit
An internal command that returns control from DOS
to the previous level.  Many applications can
"shell out" to DOS, letting you run DOS commands
and then return to the application.  Simply type
exit to return.



DOS extender
Software that is combined with a DOS application to
allow it to run in extended memory (beyond 1MB).
Some DOS extenders work with 286s and up, others
require a 386 minimum.  To gain access to extended
memory, it runs the application in Protected Mode.
When the application requests DOS services, the DOS
extender either handles them itself or, with
functions such as disk accesses, resets the machine
to Real Mode, lets DOS service the request and then
switches back into Protected Mode.

   DOS-extended programs can run by themselves in a
DOS machine, but the VCPI specification was
developed to enable them to run cooperatively with
DESQview and other VCPI-compliant applications.
The DPMI spec was developed for compliance with
Windows 3.0.

   If an XMS driver is present, DOS extenders will
use XMS to allocate memory.



DOS extensions
Names used to identify DOS file types.  See
extension and DOS file names.



DOS external command
A separate utility program that comes with DOS,
such as Format, Diskcopy, XCopy, Tree, Backup and
Restore, but is not resident within DOS, such as
Copy and Dir.

   The directory that contains these programs
should be on the path so that you can run them no
matter which directory you're in.  Contrast with
DOS internal command.



DOS Fastopen
An external command starting in DOS 3.3 that
reopens hard disk files quickly.  If a drive is
specified with Fastopen, the locations of the files
opened are stored in memory.  When opened again
within the same session, their exact location is
known.

   Fastopen is put in the AUTOEXEC.BAT file with
the number of files you want to hold in memory:

 fastopen c:=50        hold 50 file names on C:
 fastopen c:=50 d:=75  50 on C:, 75 on D:


   DOS 4.01 can optionally keep track of all the
file fragments.  This second number is usually four
times greater than the number of names:

            fastopen c:=(50,200)


                     Caution!
Fastopen cannot be used on network drives, and it
can be used only once per computer session.



DOS FAT
(DOS File Allocation Table)  The part of the DOS
and OS/2 file system that keeps track of where data
is stored on disk.  When the disk is high-level
formatted, the FAT is recorded twice and contains a
table with an entry for each disk cluster.

   The directory list, which contains file name,
extension, date, etc., points to the FAT entry
where the file starts.  If a file is larger than
one cluster, the first FAT entry points to the next
FAT entry where the second cluster of the file is
stored and so on to the end of the file.  If a
cluster becomes damaged, its FAT entry is marked as
such and that cluster is not used again.



DOS FC
An external command that compares two files for
content.  .EXE, .COM, .SYS, .OBJ, .LIB and .BIN
files are compared byte for byte, otherwise,
comparison is line by line.  To compare text files
FILE1 and FILE2, type:

 fc file1 file2        blank areas must match
                        character for character
 fc file1 file2 /w     blank areas can be of
                        different sizes
 fc file1 file2 /a     show only start and end
                        text on mismatches

   Mismatches in ASCII files show as:

  ***** first file
  start
  ...
  ...
  end
  ***** second file
  start
  ...
  ...
  end
  *****

   To compare program files ABC.EXE and XYZ.EXE,
type:

         fc abc.exe xyz.exe

   Mismatches in binary files show as:

         AAAAAAAA BB BB

 A = Hex location from start of file.
 B = Hex characters in first and second files.





DOS FCB
(DOS File Control Block)  A method of handling
files in DOS 1.0.  Applications still exist that
remain compatible with 1.0 and use this method.
See DOS Share.



DOS Fdisk
An external command used to partition a hard disk,
which is necessary before high-level formatting.
For the procedure, see "How to Format a Hard Disk"
under DOS Format.



DOS file
(1) Any computer file created under DOS.

(2) An ASCII text file.  See DOS batch file.



DOS file names
On a disk, every independent collection of
instructions or data is a "file."  Programs,
databases, word procesing documents, spreadsheets
and graphics images are examples of files.

   All files have a file name, and most files have
an extension.  Extensions are attached to the name
with a period (no spaces in between).  For example,
the following files make up the DOS and Windows
versions of this database:

        Name  Extension   Purpose

      WINGLOSS.EXE       Windows software
      WINGLOSS.HLP       Help file

        GLOSS.EXE        DOS software
        GLOSS.HLP        Help file

        GLOSS.ABC        Configuration data
        GLOSS.TXT        Text file
        GLOSS.NDX        Index


   The name can be from one to eight characters in
length.  The extension, if used, can be from one to
three characters long.

   All runnable programs in DOS have either a BAT,
COM or EXE extension (look up "extension" for a
list of over 100 common DOS extensions).

   Valid characters in names and extensions are:
A-Z,  a-z,  0-9  ! @ # $ % & ( ) ' ` -  { } ~


                 The Dot is Sacred
If an extension is used, it is added to the file
name with a period, for example, GLOSS.TXT.
As a result, the dot can't be used in a file name.
For example, GL.OSS.TXT isn't valid.


              Your Own Filing System.
Most applications use proprietary extensions for
the data files that they create.  However, several
word processors do not, and if you can organize
your documents with your own filing system.  For
example, the NOV extension could be a novel with
chapters INTRO.NOV, MAIN.NOV and END.NOV.


                       Note!
Directories are named just like files with a name
and optional extension.



DOS file transfer
See DOS Interlink.



DOS files=
See DOS CONFIG.SYS.



DOS filters & pipes
Filters are external commands that change data in
some manner.  The filters are:

   FIND - Searches for text
   SORT - Rearranges data in alpha order
   MORE - Displays data a screenful at a time

   Pipes let you direct the output of one command
as input to another.  The pipe symbol is the
vertical bar "|" above the "\" (press shift-
backslash).  Pipes are used with filters as
follows.

   To get a Dir list of all the files that have
"ZIP" somewhere in their names, you would type:

    C:\>dir | find "ZIP"    command
    PKUNZIP   EXE           results displayed
    PKZIP     EXE
    C:\>

   The pipe redirects the Dir list output to the
find command, which looks for ZIP and filters only
lines with "ZIP" in them through to output.  See
DOS Find, DOS Sort, DOS Type and DOS Dir.



DOS Find
An external command used to search for a particular
string of text in a text file.  The following
example will display the line numbers of the lines
that contain c: in the RUNJOB.BAT batch file:

           find "c:" runjob.bat

   Find is case sensitive.  "C:" will not find
"c:".  See DOS filters & pipes.



DOS Format
The DOS format is the file structure used by DOS to
keep track of data on a disk.  All floppy disks and
hard disks must be initialized with this format
before use.  The format process creates the sectors
on the disk (low-level format) that are later
filled with data and also generates the tables that
DOS uses (high-level format) to keep track of the
data.

   Hard disks are regularly formatted at the
factory, but floppies are usually not.

   The Format external command creates both low-
and high-level format on floppies, but only a high-
level format on hard disks.


              How to Format a Floppy
To format an unformatted floppy fresh from the box,
put it into drive A or B and type:

         format a:   or   format b:

   and answer the prompts.


FLOPPY DISK SIZES
There are five floppy disk capacities:

 Diameter  Capacity    Name
   5.25"     1.2MB   High density
   5.25"     360KB   Low density (Double Density)
    3.5"    2.88MB   Extra high density
    3.5"    1.44MB   High density
    3.5"     720KB   Low density (Double Density)

   Higher-density drives can read and write low-
density disks.  But to format a low-density disk in
a high-density drive, you must modify the command
as follows.


FORMATTING 5.25" DISKS
To format a 360K disk in a 1.2M drive, type:

    format a: /4         All versions
    format a: /f:360     DOS 4.01 and up


                     Caution!
360K disks formatted on very early 1.2MB drives may
cause reading problems.


FORMATTING 3.5" DISKS
To format a 720KB disk in a 1.44MB drive, type:

    format a: /n:9 /t:80  All versions
    format a: /f:720      DOS 4.01 and up


   To format a 1.44M disk in a 2.88M drive, type:

             format a: /f:1.44


REFORMATTING A FLOPPY (As of DOS 5)
The /q switch causes Format to bypass checking for
bad sectors.  To quickly reformat a formatted disk
that you know is OK, type:

             format a: /q


   Previous to DOS 5, the format program completely
formatted a floppy losing all data if previously
formatted.  As of DOS 5, Format creates a "safe
format" by saving additional data on the disk.
This takes a bit longer but allows the disk to be
unformatted.  Since you will not have to unformat
blank disks, you can format "unconditional" and
speed up the format process with the /u switch:

             format a: /u

   Also previous to DOS 5, any bad sector on a
diskette eliminated the entire track.  As of 5,
only that sector is marked as bad.


CREATING A BOOTABLE FLOPPY
To format a floppy and make it "bootable" by
copying DOS from the hard disk onto it, type:

             format a: /s

   The DOS COMMAND.COM file is also necessary on
the bootable floppy.  Starting with DOS 5, the
Format command copies COMMAND.COM to the floppy
automatically.  In DOS 4.01 and earlier, you have
to copy COMMAND.COM manually.


       Formatting a Hard Disk Is Three Steps

         WHAT YOU DO         WHAT YOU USE
   1. Low-level format    Low-level format program
   2. Create partitions   FDISK.EXE program
   3. High-level format   FORMAT.COM program


LOW-LEVEL FORMAT
If your hard drive is not already low-level
formatted from the factory (most are), it must be
low-level formatted once, using a utility program
that comes with the disk.  The utility may also be
resident in the BIOS of the disk controller card,
which you can get into by pressing a certain key at
startup.  Look for instructions on screen when you
boot your computer.  Other low-level formatting
programs are available, which may be compatible
with your drive.


CREATE PARTITIONS WITH FDISK
Every hard disk must be partitioned after it is
low-level formatted.  Even if one drive letter
serves the entire disk, you must use the Fdisk
utility to create a primary partition for that
disk.  If your DOS version cannot support the full
size of the disk, or if you want to divide up your
disk for your own storage reasons, you first make a
primary partition and then an extended partition
for the logical drives to reside in.

                         Disk size
          DOS Version    Supported
          up to 3.3         32MB
                4.0        512MB
                5.0          2GB


   To Fdisk your C: drive, boot the computer with a
bootable floppy in drive A:, which also contains
the FDISK.EXE program.  At the A: prompt, type:

               A:\>fdisk

   Select from the options.  In Fdisk, drives are
not letters, they are numbered (1, 2, etc.).  In
Fdisk, the active partition is the one you boot
from and is assumed to be the C: drive.  If it is
not, you can change that in Fdisk.

   If you want to Fdisk a second or subsequent hard
disk, load Fdisk from the C: drive:


               C:\>fdisk


HIGH-LEVEL FORMAT
The final step is to run the Format command for
each logical drive (C:, D:, etc.).  This step
creates the directory structure and FAT tables and
places startup data in the boot sector.

   To format your C: drive, boot the computer with
a bootable floppy in drive A:, which also contains
the FORMAT.COM program.  Use the /s switch to
transfer DOS to the hard disk as soon as the
formatting is completed.  To format drive C, type:

             A:\>format c: /s


   To format a second or subsequent hard drive,
load Format from your C: drive.  For example, to
format drive D:, type:

             C:\>format d:





DOS hidden file
A DOS file with a status that prevents it from
being altered, erased or normally recognized.  DOS
system files, such as IO.SYS and MSDOS.SYS, are
hidden files.  See DOS Attrib.



DOS high
See DOS Dos.



DOS high memory
The area between 640K and 1024K reserved for system
use.  Also may refer to the area between 1024K and
1088K (HMA).  See PC memory map.



DOS HIMEM.SYS
Starting with DOS 5 and Windows 3.0, HIMEM.SYS is
an XMS driver, which is software that manages
extended memory in the PC.  It allows part of DOS
to be loaded into the high memory area (HMA) to
free up more conventional memory.  HIMEM.SYS is
required if you use EMM386.EXE to load TSRs and
drivers in the upper memory area (UMA) or to turn
extended memory into expanded memory.  HIMEM.SYS is
activated in the CONFIG.SYS file and must precede
all drivers that use extended memory; for example:

     device=himem.sys
     device=emm386.exe       EMS memory manager
     device=smartdrv.sys     disk cache
     device=ramdrive.sys /e  RAM disk


   Only one program can reside in the HMA at one
time.  In order to reserve it for the largest
program, you can specify the minimum size the
program must be with the HMAMIN switch.  In the
following example, a program must be at least 50K
to use the HMA:

     device=himem.sys /hmamin=50


Note: Windows requires extended memory and comes
with its own HIMEM.SYS driver that is automatically
installed.  However, DOS 5's HIMEM.SYS supersedes
the HIMEM.SYS from Windows 3.0, and DOS 6's
HIMEM.SYS supersedes the HIMEM.SYS from Windows
3.1.  Thus, if you install Windows 3.1 on a DOS 6
machine, the installation will reference the
HIMEM.SYS that it put in the Windows directory.
For better operation, change the line in CONFIG.SYS
to reference the more current HIMEM.SYS in the DOS
directory, rather than the Windows directory.  See
DOS Dos and DOS EMM386.EXE.



DOS history
See DOS Doskey.



DOS installing from drive B:
See DOS Assign.



DOS Interlink
Starting with DOS 6, the Interlink utility lets you
transfer files between two PCs connected via their
serial or parallel ports.  It is an elementary
utility and only establishes the connection between
the two machines.  You must use standard DOS
commands such as Copy and Xcopy to do the actual
file transfers.

   The cable used for the serial port can be a 3-
wire file transfer cable or a 7-wire null modem
cable.  The parallel cable must be a bidirectional
parallel cable.

   The PC with DOS 6 and the INTERLNK.EXE program
is the controlling computer and is identified as
the client PC.  The second machine (DOS 3.0 and up)
is considered the server PC and functions like a
remote disk drive to the client.  The program
INTERSVR.EXE must be transferred to the server PC
via floppy or by remote copy (see below).

   Once the link is established, the disks on the
server are assigned drive letters on the client.
For example, if the client has an A:, B: and C:
drive, drive A: on the server becomes drive D: on
the client as in the following example:

                              Client
                           (controlling
          Server             computer)

                                 A:
                                 B:
                                 C:
            A:  -- becomes -->   D:
            B:  -- becomes -->   E:
            C:  -- becomes -->   F:


   Using standard DOS commands, you can copy and
move files between the client and server, and you
can even delete and run programs on the server as
if they were on the client by using the drive
letters assigned by Interlink.


SETTING UP THE CLIENT
Add up the total number of drives on both PCs and
add the following line to the bottom of your
CONFIG.SYS file (see DOS CONFIG.SYS).  Reboot the
computer.  The following example assumes five total
drives:

   device=c:\dos\interlnk.exe  /drives:5


SETTING UP THE SERVER
Transfer the INTERSVR.EXE program from the client
to the server via floppy disk or use the following
procedure for a remote transfer:

  1. Cable PCs together via the serial ports.
  2. If you are using other than COM1 on the
     server machine, be sure that the SHARE
     command is not loaded (rem it out in
     AUTOEXEC.BAT and reboot.)
  3. Switch to the directory on the server
     machine you want the file to go in.
  4. Type interlnk /rcopy on the client.
  5. Follow instructions.


ESTABLISHING THE LINK
  1. Cable PCs together via parallel or
     serial ports.
  2. Type intersvr on the server.
  3. Type interlnk on the client.

   The server will display a status screen during
the link, but the client will return to the DOS
prompt so you can use the Copy, Xcopy and other DOS
commands to transfer files.  If during copying, you
forget the new drive assignments on the server,
type interlnk on the client once again to review
them.

   Note that the INTERLNK.EXE driver loaded by
CONFIG.SYS will take up memory each time you start
up the computer unless you remove that line.



DOS internal command
A command capability within DOS at all times, such
as Dir, Copy, Del, Ren, Type and Cls.  The internal
commands are part of DOS' COMMAND.COM file.  If you
delete COMMAND.COM, you can no longer command DOS
to do anything at the command line.

   The other kind of commands DOS can execute are
external commands.  Each external command, such as
Format, Xcopy and Backup, resides in its own file
in the DOS directory.  If any of those files are
deleted accidentally or purposefully, you can still
execute all of DOS' internal commands and any
external commands that are still left on disk.



DOS Join
An external command that assigns a drive to a
directory.  For example, if a program accesses
files on C only, but you want it to use files on B,
you can make the B drive appear to be a directory
of C.  Join creates the directory, but it must be
off the root.

    join b: c:\bdrive  join B to C:\BDRIVE
    join b: /d         unjoin B
    join               display join status


   Don't use Join with Assign, Subst, Backup,
Chkdsk, Diskcomp, Diskcopy, Fdisk, Format, Label,
Recover, Restore or Sys commands on a joined drive.



DOS key commands
The following keyboard keys can be used:

Ctrl-Alt-Del  Reset computer
 Ctrl-C or
  Ctrl-Break  Cancel operation
      Ctrl-S  Stop scrolling
      Ctrl-P  Print what's displayed (on/off)
 Shift-PrtSc  Print current screen
   F1 or -->  Redisplay last DOS entry a
               character at a time
          F3  Redisplay last DOS entry
          F6  Enter Ctrl-Z (end-of-file character)
   Alt-Digit  Enter ASCII character by value (use
               numeric keypad)





DOS Label
An external command that names a disk (volume
label).  The name can be up to 11 characters long,
and it can contain spaces.  To name the disk in A
1992 BUDGET, type:

             label a:1992 budget


                    Important!
Don't use Label on a network drive, or one that has
been ASSIGNed, JOINed or SUBSTituted.



DOS laplink
See DOS Interlink and LapLink.



DOS Lastdrive
Used in the CONFIG.SYS file, this command specifies
the maximum number of drives that can be accessed.
The following line in CONFIG.SYS sets the last
drive letter to M:

            lastdrive=m





DOS Loadfix
An external command starting with DOS 5 that loads
a program beyond the first 64K of RAM, solving a
problem with some earlier programs.  As of DOS 5,
part of DOS can be loaded into high memory, thus
freeing up more lower memory.  Some programs cannot
run in this lower RAM and generate a "Packed file
corrupt" error.  "Packed" refers to an older method
for compressing EXE files, and this method had a
bug in it that prevents it from running in lower
RAM.

   The following example loads the program ABC
beyond the first 64K:

              loadfix abc





DOS Loadhigh
An internal command starting with DOS 5 that loads
a program into the UMA (upper memory area: 640K-1M)
in 386s and up.  It requires that the HIMEM.SYS and
EMM386.EXE memory managers be loaded and the
dos=umb command be present.

   If you have programs that need expanded memory
(EMS), the following three lines in CONFIG.SYS are
required to use Loadhigh.  The RAM parameter
informs EMM386 to manage both the UMA and expanded
memory:

   device=\dos\himem.sys
   device=\dos\emm386.exe ram
   dos=umb

   The following example uses the NOEMS parameter
to inform EMM386 to manage only the UMA and not
expanded memory:

   device=\dos\himem.sys
   device=\dos\emm386.exe noems
   dos=umb


   If the lines above are in your CONFIG.SYS file,
you can load programs into upper memory.  The
following example, which can be run from the DOS
prompt or in your AUTOEXEC.BAT file, loads POPUP
into the UMA.  If POPUP is too big to fit into an
available, contiguous memory block, it will load
below 640K.

   loadhigh popup  or  lh popup


   To load a device driver into upper memory, use
the Devicehigh command in CONFIG.SYS instead of
Device; for example:

    device=ansi.sys      below 640K
    devicehigh=ansi.sys  above 640K


   See DOS Dos and DOS Mem.



DOS Md
An internal command that makes a new directory.
Mkdir is an alternate form.  To create the HARRY
directory off the root, type:

        C:\>md harry

           or type:

        C:\>mkdir harry


   See DOS directories and DOS abc's.





DOS Mem
An external command starting with DOS 4.01 that
displays the amount of memory currently used and
free.  Type:

                 mem


   Starting with DOS 5, to display the contents of
memory by program name and show the available free
memory blocks (UMBs) in upper memory (UMA), type:

                 mem /c


   To pause after a screenful so the information
doesn't roll of the screen, type:

         mem /c | more    in DOS 5
         mem /c /p        in DOS 6





DOS Memmaker
Starting with DOS 6, Memmaker is a utility that
optimizes memory on 386s and up by determining the
best order to load TSRs and drivers in the upper
memory area (UMA).  Memmaker may change device=
statements to devicehigh= in your CONFIG.SYS file
in order to load drivers in the UMA.  It may add
the loadhigh command to TSRs loaded in your
AUTOEXEC.BAT file to load them "high" as well.  To
run Memmaker, type memmaker.

   Choosing Express Setup will configure your
system automatically.  If certain TSRs and drivers
placed in the upper memory area cause conflicts,
you can exclude them by running Memmaker and
choosing Custom Setup or by adding their names to
the MEMMAKER.INF file.  Use the DOS Editor to open
MEMMAKER.INF and read the instructions.

   Choosing Custom Setup lets you specify further
optimization.  For example, if you use an EGA or
VGA monitor and not Super VGA, answer Yes to "Use
monochrome region for running programs."  If you
run only Windows applications, choose "No" to
"Optimize upper memory under Windows?"  See DOS
CHKSTATE.SYS and DOS SIZER.EXE.



DOS memory manager
A memory manager is software that expands DOS'
ability to manage more than one megabyte of memory
or to manage its first megabyte more effectively.
Since the early days of DOS, third party memory
managers, such as QEMM and 386MAX, have used every
trick in the book to move TSRs and drivers out of
the lower 640K and into the 384K upper memory area
(UMA).

   Starting with DOS 5, DOS includes its own memory
managers.  HIMEM.SYS manages extended memory, and
EMM386.EXE manages expanded memory.  See DOS
HIMEM.SYS, DOS EMM386.EXE, DOS Memmaker, memory
allocation, PC memory map, EMS, XMS, VCPI and DPMI.
Also see PC operating environments.

               DOS Memory Areas
   Conventional memory        0-640K
   Upper memory area (UMA)  640-1024K
   High memory area (HMA)  1024-1088K
   Extended memory         1024 and up
   Expanded memory         Bank switched memory


   Popular non-Microsoft memory managers for DOS
are QEMM, 386MAX and NETROOM.



DOS Mirror
An external command in DOS 5 that loads the Delete
Tracker memory-resident program (TSR).  It takes 6K
of RAM and monitors the files you delete.  It adds
a greater level of protection in case you have to
undelete a file later.

   In DOS 6, the Undelete command is used to
activate Delete Tracker.  Also, Delete Sentry
provides even greater protection (see DOS
Undelete).  In DOS 6, Mirror is not installed, but
still resides on the DOS 6 Supplemental Disk.  See
"There's More to Mirror" below.

   Mirror creates and uses a MIRROR.FIL file and
also creates hidden MIRORSAV.FIL and PCTRACKR.DEL
files.  To automatically load it each time you
start up, place the command in your AUTOEXEC.BAT
file.  The following example tracks drives C and D:

          mirror c: d: /tc /td


   If you must unload Delete Tracker from memory,
type:

             mirror /u


   Use the Undelete command to undelete a file.
For example, to undelete SALES.DBF, type:

          undelete sales.dbf



              There's More to Mirror
Mirror is also used to save information about your
hard disk partition, directories and FAT table,
which could get corrupted in the event of a power
failure while writing to the hard disk.  This
command, initiated in DOS 5, has been relegated to
the DOS 6 Supplemental Disk.  Most DOS 6 books
don't even mention Mirror, no doubt because data
recovery is not an exact science.  In addition,
Mirror cannot take a snapshot of drives compressed
under DOS 6's DoubleSpace.

   One DOS 6 book that does elaborate on Mirror is
"MS-DOS 6, The Ultimate Guide for Experienced DOS
Users" by Minasi, Camarda, Stang and Ashton, ISBN
1-56205-132-6.

   Nevertheless, if you want to provide more
protection, you can run Mirror in both DOS 5 and
DOS 6 as follows.


SNAPSHOT YOUR PARTITION TABLE
To save vital data about your hard disk partition
in a file called PARTNSAV.FIL on a floppy disk,
type:

          mirror /partn


   Put the floppy in a safe place.  If you ever get
an "Invalid drive specification" on your valid
drive, the partition table may be corrupted.  To
restore your partion, find your PARTNSAV.FIL
floppy, and type (see warning below):

          unformat /partn


SNAPSHOT YOUR UNCOMPRESSED DRIVES DAILY
Take a snapshot of your hard disk directories and
FAT table every time you start up by placing the
Mirror command in your AUTOEXEC.BAT file.  A
MIRROR.FIL and a hidden MIRORSAV.FIL file will be
created.  For example, to snapshot drives C and D,
type:

             mirror c: d:


   In DOS 5, the above command can be combined with
starting Delete Tracker.  See the example in the
beginning of this definition.


   The following procedure is used to restore your
C drive, providing you take daily snapshots that
have not become corrupted (see warning below):

RESTORE PARTITION
 1. type unformat /partn
 2. insert PARTNSAV.FIL floppy disk
 3. insert bootable floppy to reboot

RESTORE FAT AND DIRECTORIES (if necessary)
 4. type unformat c: /j  test outcome first
 5. type unformat c: /u  do the restore


                 ! W A R N I N G !
You can try the above procedure if you absolutely
cannot get to your data at all, but there is no
guarantee you will succeed.  The success ratio of
users trying to do their own data recovery on badly
corrupted disks is most likely the reason Microsoft
has all but abandoned Mirror in DOS 6.

   Keep in mind that if you do snapshot your drives
routinely and one day you have a problem, one of
the worst things you can do is to keep rebooting.
Mirror keeps a previous and current snapshot, but
rebooting over and over can cause you to take new
snapshots of bad disks.  It is better to reboot
from a bootable floppy.

   Even better is to get help from an experienced
data recovery expert, such as the tech support rep
from your hardware supplier or the software company
that you purchased data recovery utilities from,
such as Symantec or Fifth Generation.

   BETTER THAN ALL OF THIS IS TO MAKE BACKUPS OF
YOUR DATA REGULARLY.  Your vital data takes up less
room than you think.  Even if you have a 200MB
drive, you may be surprised to find out that most
of it is software, which you can re-install, even
if it takes several hours and is a royal pain.

   You may be able to store all your vital data on
less than a dozen floppies if you compress it with
PKZIP or some other backup or compression utility.
If you have DOS 6, see DOS MSbackup.


                    Important!
Don't run Mirror on any drive that has been
redirected with Join or Subst.  If using the Assign
command, do the Assign before executing Mirror.



DOS Mkdir
See DOS Md.



DOS Mode
An external command that allows changes to a
variety of settings.  Following are common
examples:


SET THE SERIAL PORT FOR COMMUNICATIONS
To set the first serial port to 9600 baud, No
parity, 8 bits and 1 stop bit, type:

         mode com1:9600,n,8,1


SET THE SERIAL PORT FOR THE PRINTER
To set the first serial port to 4800 baud and even
parity for a printer, type:

         mode com1:4800,e,,,p


REDIRECT THE PRINTER PORT
To redirect printing from the parallel port to
serial port #1, type:

     mode lpt1:=com1:      reroute data
     mode lpt1             cancel rerouting


CHANGE KEYBOARD SPEED (TYPEMATIC RATE)
As of DOS 4.01, the Mode command can be used to
change the keyboard repeat rate and the amount of
delay before repeating.  For example, to change the
rate to 20 and the delay to .5 sec, type:

        mode con rate=20 delay=2

Rates: 1-32  Delays: 1-4 (.25 .50 .75 1.0 sec.)


LEFT HANGING IN 40-COLUMN MODE?
If a program leaves you in 40-column mode (extra
wide text characters on screen), you can switch
back to 80 column mode with

              mode 80





DOS More
More is a filter that accepts output from a command
and pauses.  It waits for a keystroke to continue.
See DOS filters & pipes and DOS Type.



DOS Move
An external command starting with DOS 6 that moves
a file to a new location (it copies first, then
deletes the source file).  The syntax is like the
Copy command; however, you must always enter a
target destination.  That means even though you are
already in the directory you want to move the file
into, you still have to state it.  For example, to
move file ABC from the B: drive into the UTILITY
directory, type:

      C:\UTILITY>move b:abc \utility

   Note: The C: drive is implicit, but the \UTILITY
directory is not and must be explicitly stated even
though you are already in it.



DOS MSAV
(DOS MicroSoft AntiVirus)  Starting with DOS 6,
MSAV is a menu-driven utility that scans memory and
disk for viruses.  To run it, type msav.  To run
the program automatically each time you start the
computer, add one of the following lines in your
AUTOEXEC.BAT file:

     msav /p     scan memory and drives
     msav /p /l  limit scan to local drives
                  if network drives are used

   A memory resident antivirus utility is also
included that will continually check for viruses.
To load it, type vsafe.  To unload it, press Alt-V
and Alt-U.

                 For Windows Users
A Windows version of MSAV.EXE is included with DOS
6 called MWAV.EXE.  This is run from an icon in
Windows, which is installed in the Microsoft Tools
Program Group.



DOS MSbackup
Starting with DOS 6, the MSbackup program provides
a menu-driven backup and restore utility for floppy
disks that contains its own help.  To run it, type
msbackup.  The first time you run it, it will ask
you to perform a compatibility test to adjust to
your computer's hardware configuration.  See backup
types.

                 For Windows Users
A Windows version of MSBACKUP.EXE is included with
DOS 6 called MWBACKUP.EXE.  This is run from an
icon in Windows, which is installed in the
Microsoft Tools Program Group.



DOS MSD
(DOS MicroSoft Diagnostics)  Starting with DOS 6,
MSD is a diagnostic utility that reports the
current hardware and software configuration of your
system.  Type msd to load the program.



DOS multiple startups
See DOS startup options.



DOS online help
Starting with DOS 5, online help is available from
the DOS prompt.  For example, in DOS 5, to see a
summary of syntax and switches for the Xcopy
command, type:

         help xcopy  or  xcopy /?

   To display a list of all DOS commands, type help
by itself.

   Starting with DOS 6, there are two kinds of
help.  Typing help loads a help system with
hypertext links to related commands.  To load the
system and immediately go to a specific command,
type the name of the command; for example, help
xcopy.  Typing xcopy /? will generate a summary
help screen as it does in DOS 5.



DOS optimizing memory
See DOS memory manager and DOS Memmaker.



DOS Path
A "DOS Path" means two different things.  First,
the Path command as described in this definition is
an internal command that sets up a search path to
one or more directories.  If you type in a program
name on the DOS command line, and that program is
not found in the current directory, DOS looks for
the "path environment variable."  If the path
variable is present, it searches for the program
you specified in all the directories named in that
path.

   Second, a "DOS path" is the naming convention
used to describe a file on a DOS disk.  The path,
in this case, is the route to the file starting
with the drive letter followed by the names of all
the directories that lead up to that file.  For
more on this routing method, look up DOS path name
below.  Also read DOS abc's and DOS directories.

   The Path command is placed into the AUTOEXEC.BAT
file, which is executed on startup.  The following
example sets up a search path to C:\(root), C:\DOS
and E:\UTILITY.  Directory names are separated with
a semicolon (;):

           path c:\;c:\dos;e:\utility


   To add the C:\123 directory to the example
above, you would add  ;c:\123  to the end of the
line, resulting in:


     path c:\;c:\dos;e:\utility;c:\123


                What Goes in the Path?
The directories typically named in the path are the
DOS directory, so that all DOS external commands
(Format, Xcopy, etc.) can be executed no matter
what directory you are in and directories that
contain utilities or batch files that perform some
function on files no matter where they are located.
See DOS AUTOEXEC.BAT.



DOS path name
The route to a file on a DOS disk.  The path name
is used whenever it is necessary to explicitly
state the location of a file.  Whenever you are
required to enter the "path," it means you have to
describe this entire route from start to finish.
The path starts with the drive letter followed by
the directory hierarchy and ends with the file name
itself.  For example:

      DRIVE     DIRECTORIES     FILE NAME


   This is often called the "full path name," which
means it defines the entire route, or path, to a
specific file.

   If you are not familiar with the use of the
drive letters, colons and backslashes used in the
following examples, this is all described in detail
in DOS abc's and DOS directories.

   The following example is the full path name to
the SALES.DBF file that resides in the DBASE
directory on the C: drive:

         c:\dbase\sales.dbf


   The full path to a file named BUDGET.WK1 in the
root directory on the D: drive looks like this:

         d:\budget.wk1


   Sometimes, you can't tell whether a path name is
a directory path or a full path name to a file.
The following example could be both.  LETTER could
be a subdirectory attached to the WP directory, or
it could be a document within the WP directory.

          c:\wp\letter


   If LETTER was a document in the LETTER
directory, its full path name would be:

          c:\letter\letter


             Some Things are Implicit!
If you only have a C: drive, the C: is implicit.
You can often omit the C: from the path name,
especially if you are entering a path to call up a
program or file in the current session only.
However, for path names that are saved with an
application, you are better off entering the full
path name starting with the drive letter.  If you
subsequently add a D: drive, previously-saved path
references may conflict.

   See DOS directories, DOS Path, DOS AUTOEXEC.BAT
and DOS abc's.





DOS pipes
See DOS filters & pipes.



DOS Print
An external command that prints text files or pre-
formatted word processing files in the background
allowing you to continue work on something else.
To print files ABC and XYZ, type:

                print abc xyz


   To print all files with a .TXT extension, type:

                 print *.txt


   Specified files are placed in a queue and
printed one after the other.  Print queue commands
are:

       print      display status
       print /t   cancel all printing

   To increase the number of files allowable in the
queue from 10 (default) to 20 (max 32), type:

            print *.txt /q:20


                Other Print Options
You can also print text files with DOS's Type
command (see DOS Type).  To display the current
text screen, press Shift-Print Screen.  In
addition, to print directory lists, press Ctrl-P
before typing the Dir command.  The text on screen
will be sent to the printer.  Press Ctrl-P again
when you're done.



DOS prompt
The message DOS displays when ready to accept user
input.  The default prompt (C>, D>...) displays the
current drive and doesn't say which directory
you're in.  Since this can be changed, PCs are
usually configured with the following line in the
AUTOEXEC.BAT file, which creates the prompt used in
our examples:
                  prompt $p$g

 Prompt
  Code      Displays
   $p   Current drive/directory
   $g   >
   $l   <
   $b   |
   $$   $
   $n   Default drive
   $t   Time
   $d   Date
   $v   DOS version
   $_   Go to next line

   The command, prompt XYZ Company$_$d  $p$b
would generate the following DOS prompt:

          XYZ Company
          Tue 04-30-1993  C:\|





DOS RAM disks
RAM disks simulate a disk drive in memory and
provide fast retrieval of programs and data.  If
operations are disk intensive, they can be speeded
up using RAM disks; for example, copying files
within a RAM disk is almost instantaneous.
However, some operations may benefit only slightly.
You'll have to try it to find out.

   RAM disk contents are lost if the power fails or
the computer is turned off, thus, data updated in
RAM disks should be periodically copied to real
disks.  RAM disks take on the next available drive
letter.

   To copy files into RAM disks on startup, put
Copy commands in your AUTOEXEC.BAT file.

   RAM disks are activated by adding a line in
CONFIG.SYS.  The following examples assume that
VDISK.SYS and RAMDRIVE.SYS are in the root
directory.

 Number of directory entries 
 Sector size (128-256-512)Ŀ 
 RAM disk size (KBytes)           Install
                                  RAM disk in
                                  this memory:
   DOS 3.x
   device=vdisk.sys  100 512 5       conventional
   device=vdisk.sys 2000 512 150 /e  extEnded
   device=vdisk.sys 1000 512 50 /a   expAnded (EMS)

   DOS 4.01 and up:
device=ramdrive.sys  100 512 5       conventional
device=ramdrive.sys 2000 512 150 /e  extEnded
device=ramdrive.sys 1000 512 50 /a   expAnded (EMS)

   Starting with DOS 5, 4096K is the maximum disk
size for one RAMDRIVE.SYS disk.  For multiple RAM
disks, use multiple DEVICE= lines.

   Use 128 sector size for small files; 512 for
large ones.  The default is 128 in VDISK and 512 in
RAMDRIVE.  If you leave this out, you can't include
a directory entry number.

   Number of directory entries is 2 to 512 for
VDISK; 2 to 1024 for RAMDRIVE.  The default is 64.


                       Note!
In order to use extended or expanded (EMS) memory
for your RAM disk, you must load the extended
memory or EMS driver from CONFIG.SYS before loading
your RAM disk driver.  See DOS HIMEM.SYS and DOS
EMM386.EXE.



DOS RAMDRIVE.SYS
See DOS RAM disks.



DOS Rd
An internal command that removes a directory.
Rmdir is an alternate form.  Directories must be
empty first, and the command must be entered from
the previous level or from a non-related directory.
To remove the HARRY directory directly off the
root, type:

       C:\>rd harry

          or type:

       C:\>rmdir harry

   HARRY can also be removed while in another
directory by stating the full path to it; for
example:

       C:\WORK>rd \harry


   For DOS 6 Users: See DOS Deltree to remove
directories that contain files and subdirectories.

   See DOS directories and DOS abc's.



DOS Recover
An external command up to but not including DOS 6
that reads data on disks that are physically
damaged.  It reads files a sector at a time
recovering whatever data it can and puts the
recovered files into the root directory.  You can
recover an entire disk by specifying only the drive
letter, but recovered files are renamed starting
with FILE0001.REC, and you won't know which is
which.  It is best to recover one file at a time;
for example:

         recover a:sales.dbf





DOS redirection
Redirecting keyboard input and screen output (see
DOS Mode to redirect the printer port).  Normally,
DOS gets input from the keyboard and displays
output on screen.  However, you can redirect input
from the keyboard to another file and redirect
output from the screen to the printer or a disk
file.  The symbols are:

   <   Redirect input
   >   Redirect output to a new file
   >>  Redirect output to an existing file

   For example, to redirect the output of a Dir
list to the printer, type:

                 dir > prn


   PRN is the name of the parallel port (see DOS
device names).

   The following example redirects input to sort a
text file named FIRST into alphabetical order and
display it on screen:

               sort < first


   Using both input and output redirection, the
sorted file can be copied into a new file called
SECOND.  Think of < as "input from," and > as
"output to."

            sort < first > second


   Redirection can be used with the Pipe command,
which funnels output of one command into another.
The following example, using the pipe's vertical
bar symbol, funnels output of the Dir list to the
Sort filter before redirecting it to a disk file
called NEWLIST:

            dir | sort > newlist

   Since the pipe and redirection symbols act as
word separators, you could type the above command
as:

            dir|sort>newlist


   See DOS Sort.





DOS Rem
A Rem statement is used to place comments in a DOS
batch file or the CONFIG.SYS file to remind the
user of something.  For example, the following line
is for documentation purposes only:

  rem   the following driver activates the mouse
  device=mouse.sys


   You can bypass any command in the file by adding
REM at the beginning of the line.  In the following
example, MOUSE.SYS will not be loaded:

         device=mouse.sys   command activated
  rem    device=mouse.sys   command not activated





DOS Rename
An internal command that changes the name of one
file at a time.  To change from ABC.DOC to XYZ.DOC,
type:

          rename file.abc file.xyz  or
             ren file.abc file.xyz

   Put a space between words and names.





DOS Replace
An external command (DOS 3.3 and up) that copies
files that have been updated.   The /u checks time
and date and copies only files from the source
directory that are newer than the files in the
target directory.  To update .TXT files on drive B,
type:

           replace *.txt b: /u





DOS restoring disks
See DOS Recover, DOS Unformat, DOS Undelete, DOS
Backup/Restore and "There's More to Mirror" in DOS
Mirror.



DOS Rmdir
See DOS Rd.



DOS root
The first directory on a disk.  See DOS abc's and
root directory.



DOS ScanDisk
Starting with MS-DOS 6.2, an external command that
detects and repairs errors on disk.  It is easier
to use and more thorough than the Chkdsk command.
Following are syntax examples:

        scandisk       check default drive
        scandisk d:    check drive d:


   If ScanDisk finds any areas on the disk
unreadable, it will try to recover the data stored
there by moving it to other clusters.  It will then
mark the clusters as "bad" so they cannot be used
again.  ScanDisk prompts you through all of its
actions and is fairly straightforward.

   For good disk maintenance, if you are running
DOS 6 or higher, periodically run ScanDisk and then
Defrag (see DOS Defrag).  Some people are extreme
about this and run them every week.  Some wait
months.

   To learn more about ScanDisk from MS-DOS 6.2's
online help, type help scandisk at the DOS prompt.
Then press Alt-C, click on "What's New in MS-DOS
6.2?"  Then click on "An Introduction to ScanDisk."



DOS Set
An internal command that sets environment
variables, which are stored values used by DOS as
well as many applications.  PATH, APPEND, COMSPEC
and PROMPT are actually environment variables too.

   An environment variable is often used to
indicate where temporary files are stored, such as
in the following example:

               set temp=c:\dos


   To display the current values for all the
environment variables, type:

                     set



                    Important!
In other DOS commands, spaces after the equals sign
don't matter.  With Set, they do.  The command set
state = IL would make the first character of the
STATE variable a blank (" IL"). 



DOS Setver
An external command starting with DOS 5 that
updates a version table containing names of
programs and the DOS version number they need to
run under.  Programs may test version numbers and
function differently as a result (all DOS's are not
the same), but some programs didn't plan on 5 as a
future number.  This command "fakes them out" by
supplying them with the version number they need.

   A list of known programs in the version table is
included, and the DOS install program puts a
device=setver.exe line in the CONFIG.SYS file,
which loads the version table.

   To see the current list, type:

             setver


   You can add and delete programs to the list.  To
set the program OLDPROG.EXE to Version 3.3, type:

          setver oldprog.exe 3.30


   To remove it from the list, type:

          setver oldprog.exe /delete



DOS Share
An external command that provides file sharing and
file locking in a network environment.  To load
Share, type:

                 share


Starting with DOS 5, load SHARE.EXE in the
CONFIG.SYS file with the Install command:

           install=\dos\share.exe


           Important for DOS 4.01 Users!
In DOS 4.01, which increased disk handling from
32MB to 512MB, Share lets applications written for
compatibility with DOS 1.0 work properly with disks
over 32MB.  You'll never know if you've got such an
application, so if you're running large disks under
DOS 4.01, be sure to put Share in your
AUTOEXEC.BAT.  Note: Share is not used this way as
of DOS 5.  See DOS AUTOEXEC.BAT and DOS FCBs.



DOS shell
Shells provide the user interface in DOS, or the
way you interact with the system.  COMMAND.COM is
the program that provides the command-driven user
interface described in this tutorial.  Other shells
can be substituted for COMMAND.COM, by adding the
Shell command in the Config.sys file; for example:

            shell=xyzmenu.com


   As of DOS 4.01, an optional user interface
called DOSSHELL is provided that lets you command
DOS with menus.  The 4.01 install program (Select)
creates the DOSSHELL.BAT batch file, which loads
DOSSHELL when executed.  Type:

            dosshell


   As of DOS 5, the menu-driven user interface has
been completely revised, and the DOSSHELL.COM is
used to start it.  Run it by typing:

      dosshell /t    text (character) mode
      dosshell /g    graphics mode
      dosshell /bw   black & white (laptops)





DOS SIZER.EXE
A utility used by Memmaker exclusively during its
optimization process that checks the size of each
program loaded.  The command is placed into
CONFIG.SYS and AUTOEXEC.BAT and then removed when
Memmaker is finished.  See DOS CHKSTATE.SYS.



DOS SmartDrive
SmartDrive is disk cache software included with DOS
and Windows starting with DOS 4.01 and Windows 3.0.
SmartDrive speeds up hard disk performance by
reserving a block of memory and reading and writing
larger chunks from the disk (see cache).  There are
two versions of SmartDrive depending on DOS and
Windows version.

       File name        DOS     Windows
     SMARTDRV.SYS    4.01, 5      3.0
     SMARTDRV.EXE        6        3.1


           DOS 4.01 & 5 and Windows 3.0
The SMARTDRV.SYS driver is loaded from CONFIG.SYS,
and its default setting uses 256K of extended
memory, for example:

     device=c:\dos\smartdrv.sys


   You can reserve more memory by adding the number
of K's to the line; for example, to reserve two
megabytes, type:

 device=smartdrv.sys 2048     extended memory
 device=smartdrv.sys 2048 /a  expAnded memory


                       Note!
In order to use extended or expanded (EMS) memory
for your disk cache, you must load the extended
memory or EMS driver from CONFIG.SYS before loading
SMARTDRV.SYS.  See DOS HIMEM.SYS, DOS EMM386.EXE
and cache.


               DOS 6 and Windows 3.1
The SMARTDRV.EXE program is loaded from the
AUTOEXEC.BAT file.  If a SCSI drive was detected on
installation, SMARTDRV.EXE is also loaded from
CONFIG.SYS as in the following example:

             No SCSI drive detected
    c:\dos\smartdrv        in AUTOEXEC.BAT

              SCSI drive detected
    c:\dos\smartdrv        in AUTOEXEC.BAT
    CONFIG.SYS:
    device=c:\dos\smartdrv.exe /double_buffer


   To determine if the device= line can be removed
from CONFIG.SYS, type smartdrv (after SMARTDRV has
been loaded in AUTOEXEC.BAT).  If every line under
the column "buffering" reads NO, you can remove the
line.

   SmartDrive's default setting uses 1 to 2MB of
extended memory depending on the amount of RAM
installed.  You can reserve more memory by adding
the number of K's to the line.  The following
AUTOEXEC.BAT example reserves 4MB (4096KB) of
extended memory for DOS applications.  The second
number (2048KB) limits Windows to reducing the
cache size to 2MB.  After Windows is exited, the
cache is restored to 4096K.

        c:\dos\smartdrv 4096 2048


                       Note!
In order to use extended memory for your disk
cache, you must load the extended memory driver
from CONFIG.SYS before loading SMARTDRV.SYS.  See
DOS HIMEM.SYS.



DOS Sort
An external command that sorts a text file or Dir
list into alphabetical order.  Lines in the text
files must be uniform and columns (fields) must
line up, such as the text within the BBS definition
in this database.

   The following example sorts the text file ABC
(starting at column 1), creating ABC2.  The < means
"input from," and the > means "output to."

              sort < abc > abc2


   Let's assume that the text in our BBS definition
is stored in a file called BBS.  The following
examples create a new file in telephone number
sequence.  They use the /+ switch to indicate that
the telephone numbers begin in column 40 (character
position 40):

  sort /+40 < bbs > bbs2     a-z order
  sort /+40 /r <bbs> bbs2    z-a order (reverse)


   To sort the file and print it without saving the
results, type:

       sort /+40 < bbs > prn


   To display a sorted Dir list, type:


                dir | sort


   You can sort Dir lists by file characteristics.
Use the /+ switch to begin the sort on other than
column one of the line:

      dir | sort /+10   by extension
      dir | sort /+14   by file size
      dir | sort /+23   by month
      dir | sort /+29   by year


   To write the sorted Dir list to a disk file,
type:

     dir | sort > xyz   create new XYZ file
     dir | sort >> xyz  add to existing XYZ file


   To append the current sorted directory list to
the end of a file called XYZ, type:

              dir | sort >> xyz


                       Note!
As of DOS 5, additional sorting options for Dir are
provided (see DOS Dir).



DOS Stacks
A CONFIG.SYS command that reserves memory for
hardware interrupts.  The Stacks command has become
more of an issue with Windows, as mouse interrupts
must be stored until Windows finishes its current
operation and can service them.  The stacks=9,256
line is placed in the CONFIG.SYS file by Windows
3.1's install program.  This allocates nine stacks
of 256 bytes taking up 2,304 bytes of conventional
memory.

   Some computers save memory for this function and
can operate without additional stacks (stacks=0,0);
however, Microsoft recommends that if your PC hangs
up when you move your mouse, try the following
entries in CONFIG.SYS, one at a time:

           stacks=12,128
           stacks=9,256
           stacks=12,256
           stacks=0,0


   The first number in the command allocates the
number of stacks from 8 to 64.  The second number
is the size of the stack in bytes from 32 to 512.
The stacks=0,0 command allocates no stacks.



DOS startup options
Starting with DOS 6, there are multiple startup
options for the CONFIG.SYS and AUTOEXEC.BAT files.
You can bypass them, decide which lines to execute
or set up multiple configurations for selection at
startup.


                    Clean Boot
You can "boot the computer clean" by bypassing the
CONFIG.SYS and AUTOEXEC.BAT files.  This is useful
if you want to test something without any TSRs or
drivers loaded.  In addition, if you changed
CONFIG.SYS or AUTOEXEC.BAT and the computer locks
up, you can still boot from the hard disk rather
than having to boot from a floppy.

   To clean boot, press and release F5 as soon as
the "Starting MS-DOS..." message appears on screen.


             Execute a Line at a Time
If a new driver or TSR causes problems, you have
the option of bypassing it at startup.  This is
helpful for testing purposes until you change the
CONFIG.SYS file permanently.  To select this
option, press and release F8 as soon as the
"Starting MS-DOS..." message appears.  Each line in
CONFIG.SYS will be displayed for confirmation.
Press Y to execute or N to bypass.  After
CONFIG.SYS is read, you will be prompted to run
AUTOEXEC.BAT in its entirety or to bypass it.


              Multiple Configurations
You can create multiple configurations within the
same CONFIG.SYS and AUTOEXEC.BAT files.  If there
isn't enough memory to load the TSRs and drivers
for all the applications in a PC, or if one TSR or
driver conflicts with another, users typically set
up separate CONFIG.SYS and AUTOEXEC.BAT files to
run different sets of software.  In order to
activate them before DOS 6, the current CONFIG.SYS
and AUTOEXEC.BAT are renamed and the required set
is given those names.  DOS 6 lets you place
multiple configurations in CONFIG.SYS and in
AUTOEXEC.BAT and prompts you for your choice at
startup.

   To do this, create a menu in CONFIG.SYS that
defines two or more configuration blocks.  The
following example simulates stand-alone and network
versions of CONFIG.SYS.  The optional text "Select
this for..." next to the MENUITEM= lines is used by
DOS as the menu option at startup.  If no text is
placed to the right of the line, then the name of
the configuration block is used as the menu option.

   The menu and configuration block headers must be
enclosed in left and right brackets ([ ]).

 [menu]
 menuitem=nonet   Select this for no network.
 menuitem=net     Select this for network.
 menudefault=nonet,5  <- default to "nonet" in 5
                         seconds if no choice made

 [nonet]             <- configuration block "nonet"
 device=c:\driver1.sys  <-statements that pertain
 device=c:\driver2.sys  <-to "nonet"

 [net]               <- configuration block "net"
 device=c:\netdrivr.sys

 [common]            <- common configuration block
 files=40               <-statements that pertain
 buffers=20             <-to all configurations
 etc.

   You may use an include= line in a configuration
block that includes all the items in another
configuration block.

   Important!  Be sure to put the [common]
configuration block last as many install programs
add lines to the CONFIG.SYS file.


CONFIGURING AUTOEXEC.BAT
You can create multiple configurations in
AUTOEXEC.BAT, but they must correspond to the
CONFIG.SYS configuration blocks.  To do this, add
the goto %config% line at the end of all common
statements in AUTOEXEC.BAT; for example:

   all common lines in AUTOEXEC.BAT
   goto %config%

   :nonet             <- be sure to use colon
   all statements for "nonet"
   goto end

   :net
   all statements for "net"
   goto end

   :end               <- last line in AUTOEXEC.BAT





DOS Subst
An external command that creates a virtual drive
and provides a shortcut for referencing long path
names.  For example, to reference C:\KAREN\BUDGETS
with drive K:, type:

       subst k: c:\karen\budgets


   If you were in the root, you could display
MYFILE by typing:

           C:\>type k:myfile

   instead of

     C:\>type c:\karen\budgets\myfile


   To cancel the K disk, type:

            subst k: /d


                    Important!
The last drive letter is normally E.  See DOS
Lastdrive.  Do not use Assign, Backup, Chkdsk,
Diskcomp, Diskcopy, Fdisk, Format, Join, Label,
Recover, Restore and Sys on a virtual drive.



DOS switch
A switch is a code, or parameter, that modifies a
command.  DOS switches use a forward slash (not a
backslash) followed by some letter, digit or code.
For example, the /w changes the Dir command to list
"wide" across the screen instead of in a column:

            dir      list in columns
            dir /w   list across the screen





DOS switching directories
See DOS Cd and DOS directories.



DOS Sys
An external command that transfers hidden DOS
system files.  To make a bootable diskette, copy
DOS from the hard disk to a floppy with the Sys
command.  The COMMAND.COM file must also be copied,
which, previous to DOS 5, must be done manually.
Starting with DOS 5, COMMAND.COM is copied
automatically by the Sys command.

 Previous to DOS 5
  C:\>sys a:               copy system

 Starting with DOS 5
  C:\>sys a:               copy system
  C:\>copy command.com a:  copy COMMAND.COM


   DOS is made up of IBMBIO.COM and IBMDOS.COM or
IO.SYS and MSDOS.SYS hidden system files along with
COMMAND.COM.  Hidden files can be listed with the
Attrib command starting with DOS 5 or a utility
such as Norton's File Attribute program.



DOS Sys files
SYS if the file extension commonly used for drivers
that are installed in DOS; for example, MOUSE.SYS,
COUNTRY.SYS and ASPI.SYS.

   The CONFIG.SYS file is the file in which all the
.SYS files are specified.



DOS system file
A DOS file that contains the fundamental part of
DOS (the kernel).  See DOS Sys.



DOS Task Swapper
Starting with DOS 5, you can run multiple
applications and switch between them.  Do the
following:

  1. Load DOSSHELL.COM by typing dosshell.

  2. To see your active tasks on screen, select
     Program/File Lists from the View menu
     (Alt V F).

  3. Select Enable Task Swapper from the
     Options menu (Alt O E).  Note: This will
     stay in effect for future sessions.

  4. Run the first program either by selecting Run
     from the File menu (Alt F R) and typing in
     the program's name, or by selecting it
     from the directory list on screen (double
     click it or highlight and press Enter).
     After the program is running, press Ctrl-Esc
     to return to the Shell.

     You can alternatively put the program into
     the Active Task List without running it, by
     selecting the program name from the on-screen
     directory list and pressing Shift-Enter.

  5. Repeat step 4 for each program.

  6. To switch between active programs, hold down
     the Alt key and press Tab until you see the
     name of the program you want at the top of
     the screen.  Then release Alt.  To switch
     between the two last programs, press Alt-Tab.

     You can also select a program from the Active
     Task List at the bottom of the Shell screen.

   There are a variety of ways to switch between
active tasks.  Look up Keyboard, Active Task List
Keys from the Shell's Help menu.



DOS text file
A text file that does not contain any proprietary
coding schemes.  Batch files and source language
programs are examples.  It contains only ASCII
characters and has a CR/LF (carriage return/line
feed) code at the end of each line.  Text files are
read by text editors as well as word processors
with "ASCII" or "text" input options.



DOS Time/Date
An internal commands that set the system time and
date and update the internal battery-powered clock.
Versions previous to 3.3 do not set the internal
clock.  A separate setup program is used.

       time           display time
       time 14:30     set to 2:30pm

       date           display date
       date 12-11-92  set to 12-11-92


TO UPDATE A FILE'S TIME AND DATE
To give a file a current time and date without
changing it, use the Copy command.  For example, to
update XYZ.BAT, type:

      copy /b xyz.bat+,,

   Be sure to add the plus, comma, comma after the
file name.  The /b ensures that no change is made
to the file.



DOS Tree
An external command that displays a list of the
subdirectories in the current directory.  To
display a directory tree, type:

                tree


   To display files names and subdirectories, type:

                tree /f





DOS tutorial
See DOS abc's.



DOS Type
An internal command that displays the contents of
text files and batch files.  For example, to
display the contents of your AUTOEXEC.BAT file,
type:

             type autoexec.bat


   To display the contents of a text file one
screenful at a time, use | more.  For example,
to display ABC.TXT one screenful at a time, type:

            type abc.txt | more


   The vertical bar is a pipe symbol and MORE is a
filter.  A pipe passes output from one function to
another.  Thus, you are piping the output of the
Type command to the MORE filter, which does nothing
more than pause after receiving a screenful of data
and waits for you to press a key.


   To print the file, redirect Type's output to the
printer:

            type xyz.bat > prn


      Do Wierd Characters Display On Screen?
The Type command lets you view only text files and
batch files that normally have a .TXT or .BAT
extension.  If you use Type with another file, such
as one with an .EXE, .DOC, or .DBF extension, you
will get a combination of strange characters on
screen, hear beeps and see lines flip around in a
rather jerky fashion.  Non-text files have formats
that trigger all sorts of screen functions because
their formats randomly match these characters (see
the first 32 characters in ASCII chart).



DOS UMA, UMB
See DOS Dos.



DOS Undelete
Prior to DOS 5, bringing a file back that has just
been deleted requires an undelete utility such as
found in Symantec's Norton Utilities and PC Tools
or Fifth Generation's Mace Utilities.

   Starting with DOS 5, an undelete command is
provided.  For example, to restore VITAL.TXT after
having deleted it, type the following and follow
the prompts:

             undelete vital.txt


   If you don't mention a file name, Undelete will
undelete all deleted files, prompting you one at a
time.


DELETE TRACKER
Starting with DOS 5, the Delete Tracker option
provides an extra level of protection in case you
have to undelete a file.  This is activated with
the Mirror command.  If you use DOS 5, see DOS
Mirror.  If you use DOS 6, read the following.

   In DOS 6, Delete Tracker is activated with the
Undelete command.  It's not as much protection as
Delete Sentry (see below), but you would use this
if you have little room left on your hard disk.

   Tracker takes up 13K of RAM and creates hidden
MIRORSAV.FIL and PCTRACKR.DEL files.  To
automatically load Tracker on startup, place the
command in your AUTOEXEC.BAT file.  The following
example tracks drives C and D:

          undelete /tc /td


USE DELETE SENTRY FOR MAXIMUM PROTECTION
In DOS 6, the Delete Sentry intercepts the files
you delete and actually moves them to a hidden
\SENTRY directory, renaming them with coded file
names.  Sentry will purge (really remove) the files
after seven days or when 20% of the hard disk is
used up with deleted files and it needs room for
more newly-deleted files.  Sentry also creates a
hidden CONTROL.FIL file in the \SENTRY directory.

   Like Tracker, Sentry will take up 13K or RAM.
To automatically load Sentry on startup, place the
command in your AUTOEXEC.BAT file.  The following
example activates Sentry for drives C and D:

         undelete /sc /sd


   If you must remove Tracker or Sentry from
memory, type:

         undelete /u


EDITING UNDELETE.INI
The first time Sentry is loaded, it creates an
UNDELETE.INI configuration file in the \DOS
directory that can be edited with a text editor.

   To change the drives Sentry intercepts, you can
add or delete DRIVELETTER= lines.  For example, to
bypass protection on floppy drives, delete the A=
or B= lines.

   To change when Sentry purges deleted files from
seven to four days, change days=7 to days=4.

   To change the maximum amount of space Sentry
uses to hold deleted files from 20% to 10%, change
percentage=20 to percentage=10.

   UNDELETE.INI excludes certain types of files
from being intercepted, such as temporary files.
It also excludes .IMG files.  If you work with .IMG
files and want protection for them, remove -*.IMG,
from the sentry.files= line.  You may wish to
exclude other types of files; for example, .BAK
files.  To exclude .BAK files, add ,-*.BAK to the
end of the sentry-files= line.

   Once UNDELETE.INI is created, you can also load
Sentry with undelete /s or undelete /load.


                 For Windows Users
A Windows version of Undelete is included with DOS
6 called MWUNDEL.EXE.  This is run from an icon in
Windows, which is installed in the Microsoft Tools
Program Group.

   If you're in Windows, use MWUNDEL.EXE first.  It
also lets you undelete directories, which you
cannot do with Undelete for DOS.  However, if you
cannot undelete a file with MWUNDEL.EXE under
Windows, go to the DOS prompt and try to undelete
it with Undelete.



DOS Unformat
An external command starting with DOS 5 that
restores a formatted disk to its previous contents,
providing it was formatted under DOS 5 without the
/S switch.  The /S switch bypasses saving unformat
information during the format process (see DOS
Format).

   Unformatting is not guaranteed.  However, you
can find out if you can unformat the disk before
doing it.  For example, to test the disk in drive
A, type:

             unformat a: /test


   To unformat the disk in drive A, type:

               unformat a: /u


   Also see DOS Mirror for additional ways Unformat
is used in data recovery.



DOS upgrading
Starting with DOS 5, Microsoft provides upgrade
packages that make it easy to upgrade a PC that has
a previous version of DOS installed on it.  The
install program records data on "uninstall" disks
during the conversion.  If the new version doesn't
work properly, you can revert to the previous one.
To install the DOS 5 or DOS 6 upgrade:

  1. Start computer as usual.
  2. Have one blank high-density floppy or two
      blank low-density floppies handy (formatted
      or unformatted).
  3. Insert disk 1 into drive A or B.
  4. Type a:setup or b:setup.





DOS upper memory
See UMA and UMB.



DOS/V
A Japanese version of DOS that supports two-byte-
long characters for handling the Kanji character
set.  It can switch between English and Japanese
and is geared for 286s and up with VGA graphics.
Backed by IBM Japan and the OADG.  In Japan, NEC is
the major personal computer vendor with its PC-9801
series.



DOS VDISK.SYS
See DOS RAM disks.



DOS Ver
An internal command that displays the DOS version.
Type:

                   ver





DOS Verify
An internal command that tests each write operation
by reading it back.

      verify on     turn on
      verify off    turn off
      verify        display status





DOS versions
Following is a list of DOS versions since its
inception in 1981:


Version      Major new features
  1.0  1981  8-sector 160KB floppy (SS).
  1.05       Bug fix.
  1.1  1982  8-sector 320KB floppy (DS).
  2.0  1983  10M hard disk, 9-sector 360KB floppy,
              directories, more batch commands.
  2.1  1983  PCjr cartridge support and bug fixes.
  3.0  1984  20MB hard disk, 1.2MB floppy, VDISK,
              PATH, new commands.
  3.1  1985  Network support, bug fixes.
  3.2  1986  720KB floppy, new commands.
  3.3  1987  1.44MB floppy, FDISK partitions.
  4.0  1988  Menu and mouse support (DOS shell),
              improved commands, EMS support,
              512MB hard disks.
  4.01 1988  Bug fix (4.0 rarely used).
  5.0  1991  Major upgrade: new DOS shell, ability
              to use high memory, task swapping,
              online help, new text editor,
              2GB hard disks, 2.88MB floppies,
              enhanced commands.
  5.02 1992  IBM version (PC-DOS 5.02), includes
              ISO fonts for European compatibility,
              power management and file transfer
  6.0  1993  Includes built in disk compression
              and various utilities for antivirus,
              backup, undelete and file transfer.
  6.1  1993  IBM version (PC-DOS 6.1), includes
              different utilities than MS-DOS 6.0.
  6.2  1993  MS version (MS-DOS 6.2), 6.0 bug fix.
  6.21 1994  MS version (without DoubleSpace)
  6.3  1994  IBM version (PC-DOS 6.3), upgrade.
  6.22 1994  MS version with Microsoft's own
              DriveSpace compression.





DOS Vol
An internal command that displays the name of the
current drive (volume).  Type:

                   vol





DOS Vsafe
See DOS MSAV.



DOS/VSE
See VSE.



DOS wild cards
Wild cards are symbols that let you reference
groups of related files.  As in card games, wild
cards take on any value.  DOS wild cards are the
"*" and "?."


                 The Asterisk (*)
The asterisk takes the value of any number of
characters; for example, if you typed in:

                  dir gloss*

   GLOSS1, GLOSS10 and GLOSSARY files would be
selected:



   To delete all files with a TXT extension, type:

                  del *.txt


   To delete all the files in the current
directory, type:

                  del *.*



               The Question Mark (?)
The question mark matches any single character.
For example, ?GLOSS would find 1GLOSS, 2GLOSS and
XGLOSS.  Note that *GLOSS is not valid for this.


   To copy CHP files that begin with CO, type:

              copy CO*.CHP a:


   To list files that begin with CO and have an
extension that begins with D, type:

              dir CO*.D*



                       Tip!
The dot is a shortcut for *.*.  The following
commands both copy all files to the B drive:

              copy *.* b:

              copy . b:





DOS Xcopy
An external command starting with DOS 3.2 that
copies files and subdirectories.  The following
examples copy from the root directory on C to the D
drive:

 C:\>xcopy *.* d:      all files in the root

 C:\>xcopy *.* d: /s   all files and subdirectories
                        that contain files

 C:\>xcopy *.* d: /s /e   all files and all
                           subdirectories (whether
                           empty or not)


   To be prompted each time Xcopy copies a source
file, add /p:

          xcopy *.* d: /s /e /p


   To be extra sure the copy is correct, add the /v
switch, which compares the new file with the old
one; for example:

          xcopy *.* d: /v


   Xcopy can copy files and create a new directory
at the same time.  The following example creates
the NEW directory and copies all the files from the
OLD directory:

       C:\OLD>xcopy *.* \new


ARCHIVING FILES
Use Xcopy's /m switch to back up only files that
have been changed since the last time they were
Xcopied.  This works only on files that have been
Xcopied at least once before and will not work on
un-Xcopied files.

   When Xcopy copies a file, it resets the original
file's archive bit from 1 to 0.  For more on
archive bits, see DOS Attrib.  Whenever you update
a file, the archive bit is set to 1.  When you use
the /m switch, Xcopy copies only files with the
archive bit set to 1.

   The following example backs up all files onto
the B disk:

             xcopy *.* b: /m


ARCHIVE ONTO MULTIPLE FLOPPIES
You can use the Xcopy and Attrib commands to copy
files onto multiple diskettes, providing no single
file is larger than the total size of the diskette.
In that case, you have to use the Backup command or
other Backup utility.

   The Attrib command is used to set all archive
bits on.  When a file is copied, the bit is turned
off.  Each time Xcopy doesn't have enough room to
copy the next file, you will get a "Disk Full"
message.  Put in another blank disk and repeat the
Xcopy command.  The archive bit keeps the
previously-copied files from being copied again.

   For example, to copy all the files in the DOCS
directory onto floppies, type:

    C:\DOCS>attrib +a *.*      do this once
    C:\DOCS>xcopy *.* b: /m    repeat until done



ARCHIVE ONE HARD DISK TO ANOTHER
The following example copies everything from the C:
drive to the D: drive that has changed since the
last time the files on C: were Xcopied.  This
includes the root and all subdirectories.  The /s
switch is used here in order to include all
subdirectories.

         xcopy c:\*.* d:\  /s /m


                       Note!
In versions previous to DOS 5, Xcopy copies hidden
and system files.  Starting with DOS 5, you must
remove the hidden and system attributes with Attrib
first.



DOS \
See DOS backslash.



DOSmark
A unit of performance based on Ziff-Davis' PC Labs
tests.  It rates a PC's ability to run DOS
applications, which is a composite of CPU, memory,
disk and video tests.  See Winmark.



Dosshell
See DOS shell.



dot
(1) A tiny round, rectangular or square spot that
is one element in a matrix, which is used to
display or print a graphics or text image.  See dot
matrix.

(2) A period; for example, V dot 22 is the same as
V.22.



dot addressable
The ability to program each individual dot on a
video display, dot matrix printer or laser printer.



dot chart
Same as scatter diagram.



dot com
Refers to a commercial Internet address, which ends
with a period and the word "com" (.com).  See
Internet address.



dot gain
An increase in size of each dot of ink when printed
due to temperature, ink and paper type.



dot matrix
The pattern of dots that form character and graphic
images on video screens and printers.  Display
screens use a matrix (rows and columns) of dots
just like TVs.  Serial printers use one or two
columns of dot hammers that are moved across the
paper.  Laser printers "paint" dots of light a line
at a time onto a light-sensitive photographic drum.

   The more dots per square inch, the higher the
resolution of the characters and graphics.



dot matrix printer
A printer that uses hammers and a ribbon to form
images out of dots.  The common desktop dot matrix
printer uses one or two columns of dot hammers that
are moved serially across the paper.  The more dot
hammers used, the higher the resolution of the
printed image.  24-pin dot matrix printers produce
typewriter-like output.

   Dot matrix printers are still widely used to
print name and address labels, diskette labels and
multiple-part forms.  Unlike sheet-fed laser and
ink jet printers, the tractor and sproket mechanism
of a dot matrix printer accepts thicker material
than plain paper.



dot pitch
The distance between a red (or green or blue) dot
and the closest red (or green or blue) dot on a
color monitor (typically from .28 to .51mm; large
presentation monitors may go up to 1.0mm).  The
smaller the dot pitch, the crisper the image.  A
.28 dot pitch means dots are 28/100ths of a
millimeter apart.  A dot pitch of .31 or less
provides a sharp image, especially on text.

   Dot pitch measurements between conventional
tubes and Sony's Trinitron tubes are roughly, but
not exactly equivalent.  Sony's CRTs use vertical
stripes, not dots, and its measurement is the
distance between stripes, not the diagonal distance
between dots.



double buffering
A programming technique that uses two buffers to
speed up a computer that can overlap I/O with
processing.  For example, data in one buffer is
being processed while the next set of data is read
into the second buffer.



double click
To press the mouse button twice in rapid
succession.



double density
Twice the capacity of the prior format.
Yesterday's double density can be today's low
density (see DD).



double dots
See DOS ...



double precision
Using two computer words instead of one to hold a
number used for calculations, thus allowing twice
as large a number for more arithmetic precision.
Contrast with single precision.



double scan CGA
A hardware circuit that improves CGA resolution.



double sided disk
A floppy disk that is recorded on both of its
sides.  See DS/DD and DS/HD.



double strike
Printing a character twice in order to darken the
image.



double twist
Same as supertwist.



double word
Twice the length of a single computer word.  A
double word is typically 32 bits long.  See word.



DoubleSpace
A realtime compression technique built into DOS 6
and removed in 6.21.  See DOS DoubleSpace.



down
Refers to a computer that fails to operate due to
hardware or software failure.  A communications
line is down when it is unable to transfer data.



downlink
A communications channel from a satellite to an
earth station.  Contrast with uplink.



download
To transmit a file from one computer to another.
When conducting the session, download means
receive, upload means transmit.  It implies sending
a file rather than interacting in a conversational
mode.

   Downloading a file from a personal computer that
has a modem is accomplished by (1) using a
communications program to dial up another computer
or online service, and (2) by selecting a file
transfer protocol common to both systems.

   Once you connect to an online service, you will
be prompted through a variety of options.  You have
to select a file to download and then select a 
protocol to use, such as Zmodem, Ymodem or CIS B,
for example.  You have to choose one that your
communications program supports.  Zmodem is usually
the best choice.

   If you are on a LAN, downloading a file from a
network server to your local machine is
accomplished by performing standard copy procedures
in the Mac or on a Windows PC or by using the DOS
copy command.  You would reference the network hard
disk as the source and your local hard disk as the
destination.  On a PC, network drives are usually
identified as K:, L: or with some other letter
higher up in the alphabet.  In UNIX, you would use
the UUCP or FTP utilities.  See DOS Copy.



downloadable font
Same as soft font.



downsizing
Converting mainframe and mini-based systems to
personal computer LANs.



downtime
The time during which a computer is not functioning
due to hardware or system software failure.  That's
when you truly understand how important it is to
have reliable hardware.



downward compatible
Also called backward compatible.  Refers to
hardware or software that is compatible with
earlier versions.  Contrast with upward compatible.



DP
See data processing and dot pitch.



DPCM
(Differential PCM)  An audio digitization technique
that codes the difference between samples rather
than coding an absolute measurement at each sample
point.  See ADPCM.



dpi
(Dots Per Inch)  The measurement of printer
resolution.  A 300 dpi printer means 90,000 dots
are printable in one square inch (300x300).  400
dpi generates 160,000 dots; 500 dpi yields 250,000
dots.



DPMA
(Data Processing Management Association)  A
membership organization founded in 1951 with over
40,000 managers of DP installations, programmers,
systems analysts and research specialists.  It
founded the CDP examinations, now administrated by
the ICCP.  Offers many educational programs and
seminars, in addition to sponsoring student
organizations around the country interested in DP.
Address: 505 Busse Highway, Park Ridge, IL 60068,
708/825-8124.



DPMI
(DOS Protected Mode Interface)  A DOS extender
specification for 286s and up that allows DOS
extended programs to cooperatively run under
Windows 3.x.  Developed by Microsoft, it keeps a
DOS-extended application from crashing the computer
and usurping Windows' control.  It is not
compatible with VCPI, the first DOS extender
standard, but Windows 3.1 is more tolerant of VCPI
applications than Windows 3.0.

               XMS Versus VCPI/DPMI
XMS, VCPI and DPMI all deal with extended memory.
However, XMS allows data and programs to be stored
in and retrieved from extended memory, whereas the
VCPI and DPMI interfaces allow programs to "run" in
extended memory.



DPPX
(Distributed Processing Programming EXecutive)  An
operating system for the 8100, now defunct.
DPPX/370 is a version allowing users to migrate to
9370s.



DPS
Minicomputer series from Bull HN.



DPSK
(Differential Phase Shift Keying)  A common form of
phase modulation used in modems.  It does not
require complex demodulation circuitry and is not
susceptible to random phase changes in the
transmitted waveform.  Contrast with FSK.



DQDB
(Distributed Queue Dual Bus)  An IEEE 802.6 packet
switching network technology for MANs.  The first
SMDS services offered by the local telephone
companies use DQDB.



DR DOS
(Digital Research DOS)  A DOS-compatible operating
system from Novell noted for its many features.
Version 5.0 includes built-in help, passwords, disk
cache, file transfer, the ability to store itself
and drivers in high memory and an optional
graphical interface.  Version 6.0 includes file
compression that doubles hard disk space.  See
Novell DOS.



Drafix
A 2-D and 3-D CAD packages for PCs and Atari STs
from Foresight Resources Corporation, Kansas City,
MO.  It features professional functions and
provides constant on-screen information during
drawing.



draft mode
The highest-speed, lowest-quality printing mode.



drag
To move an object on screen in which its complete
movement is visible from starting location to
destination.  The movement may be activated with a
stylus, mouse or keyboard keys.

   To drag an object with the mouse, point to it.
Press the mouse button and hold the button down
while moving the mouse.  When the object is at its
new location, release the mouse button.



drag & drop
The ability to execute a function graphically
without typing in a command.  For example, in the
Macintosh, selecting a floppy disk icon and
dragging it onto the trashcan icon causes the
floppy to be ejected.



drag lock
The ability to lock onto a screen object so that it
can be dragged with the mouse without continuously
holding down the mouse (or trackball) button.



drain
The output (receiving) side of the bridge in a
field effect transistor.  When the gate is charged,
current flows from the source to the drain.  Same
as collector in a bipolar transistor.



DRAM
See dynamic RAM.



DRAW
(Direct Read After Write)  Reading data immediately
after it has been written to check for recording
errors.



drawing program
A graphics program used for creating illustrations.
It maintains an image in vector graphics format,
which allows all elements of the picture to be
isolated, moved and scaled independently from the
others.

   Drawing programs and CAD programs are similar;
however, drawing programs usually provide a large
number of special effects for fancy illustrations,
while CAD programs provide precise dimensioning and
positioning of each graphic element in order that
the objects can be transferred to other systems for
engineering analysis and manufacturing.

   Examples of popular drawing programs for Windows
are Adobe Illustrator, Aldus Freehand, Designer and
CorelDRAW.  Adobe Illustrator and Aldus Freehand
are also available for the Macintosh.  Contrast
with paint program.  See diagramming program.



DRDA
(Distributed Relational Database Architecture)  An
IBM architecture for distributing data across
multiple heterogeneous platforms.  It also serves
as a protocol for access to these databases from
IBM and non-IBM platforms.  DRDA uses LU 6.2 as its
transport protocol.



DRDBMS
(Distributed Relational DBMS)  A relational DBMS
that manages distributed databases.  See
distributed database.



DRI
See Digital Research.



dribbleware
Software that is publicly displayed and previewed
well in advance of its actual release.  Dribbleware
is one stage beyond vaporware.



drift
Change in frequency or time synchronization of a
signal that occurs slowly.



drill down
To move from summary information to the detailed
data that created it.



drive
(1) An electromechanical device that spins disks
and tapes at a specified speed.  Also refers to the
entire peripheral unit such as disk drive or tape
drive.

(2) To provide power and signals to a device.  For
example, "this control unit can drive up to 15
terminals."



drive bay
A cavity for a disk drive in a computer cabinet.



drive door
A panel, gate or lever used to lock a disk in a
disk drive.  In a 5.25" floppy drive, the drive
door is the lever that is turned down over the slot
after inserting the disk.



drive type
See hard disk.



driver
(1) Also called a device driver, a program routine
that links a peripheral device to the operating
system.  It contains the precise machine language
necessary to activate the device and uses detailed
knowledge of the device's characteristics, such as
sectors per track and screen resolution, to perform
the functions that are requested by the
application.

   Basic drivers come with the operating system,
and drivers are added when new peripheral devices
are installed.  For example, if you add a mouse or
CD-ROM player to your computer, you have to install
the appropriate driver so that the operating system
knows how to handle it.  Drivers are also installed
to manage memory and other internal functions.

   In the DOS world, applications provide their own
screen and printer drivers in order to provide
complete control over the display and printing of a
document.  In Windows, screen and printer drivers
are installed and managed within Windows, not the
individual applications.

   Memory managers, RAM disks and disk caches are
also activated by drivers.  See DOS CONFIG.SYS.

(2) A device that provides signals or electrical
current to activate a transmission line or display
screen.  See line driver.



DriveSpace
Microsoft's disk compression that replaces the
DoubleSpace technology previously used.  It is
included starting with MS-DOS 6.22.



drop cap
In typography, a large first letter that drops
below the first line, for example:

          his is an example
            of a drop cap in 
            printing.



drop-down menu
See pull-down menu.



drop in
An extraneous bit on a magnetic medium that was not
intentionally written, due to a surface defect or
recording malfunction.



drop out
(1) On magnetic media, a bit that has lost its
strength due to a surface defect or recording
malfunction.

(2) In data transmission, a momentary loss of
signal that is due to system malfunction or
excessive noise.



droupie
(Data gROUPIE)  A person who likes to spend time in
the company of programmers and data processing
professionals.



drum
See magnetic drum.



drum plotter
A graphics plotter that wraps the paper around a
drum.  The drum turns to produce one direction of
the plot; the pen moves to provide the other.



drum printer
A line printer that uses formed character images
around a cylindrical drum as its printing
mechanism.  There is a band of characters for each
print position.  When the desired character for the
selected print position has rotated around to the
hammer line, the hammer hits the paper from behind
and pushes it into the ribbon and onto the
character.



drum scanner
A type of scanner used to capture the highest
resolution from an image.  Photographs and slides
are taped onto a clear cylinder that is rotated
during scanning.  For transparencies, light is
directed from the center of the cylinder.  For
opaque items, a reflective light source is used.

   The drum scanner's photomultiplier tube is more
sensitive than the CCDs used in flatbed and sheet-
fed scanners and can produce resolutions exceeding
8,000 dpi.  Contrast with flatbed scanner, sheet-
fed scanner and hand-held scanner.



dry plasma etching
A method for inscribing a pattern on a wafer by
shooting hot ions through a mask to evaporate the
silicon dioxide insulation layer.  Dry plasma
etching replaces the wet processing method that
uses film and acid for developing the pattern.



drystone
See Dhrystones.



DS
(Digital Signal)  A classification of digital
circuits.  The DS technically refers to the rate
and format of the signal, while the T designation
refers to the equipment providing the signals.  In
practice, "DS" and "T" are used synonymously; for
example, DS1 and T1, DS3 and T3.


   NORTH AMERICA, JAPAN, KOREA, ETC.

               Voice
    Service  Channels    Speed
     DS0        1        64 Kbps
     DS1       24     1.544 Mbps  (T1)
     DS1C      48     3.152 Mbps  (T1C)
     DS2       96     6.312 Mbps  (T2)
     DS3      672    44.736 Mbps  (T3)
     DS4     4032   274.176 Mbps  (T4)


          EUROPE (ITU-TSS)

              Voice
   Service  Channels  Speed (Mbps)
     E1        30        2.048
     E2       120        8.448
     E3       480       34.368
     E4      1920      139.264
     E5      7680      565.148


           SONET CIRCUITS

    Service          Speed (Mbps)
   STS-1   OC1      51.84 (28 DS1s or 1 DS3)
   STS-3   OC3     155.52 (3 STS-1s)
   STS-3c  OC3c    155.52 (concatenated)
   STS-12  OC12    622.08 (12 STS-1s, 4 STS-3s)
   STS-12c OC12c   622.08 (12 STS-1s, 4 STS-3c's)
   STS-48  OC48   2488.32 (48 STS-1s, 16 STS-3s)





DS/DD
(Double Sided/Double Density)  Refers to floppy
disks, such as the 5.25" 360KB PC format and 3.5"
720KB PC and 800KB Mac formats.



DS/HD
(Double Sided/High Density)  Refers to floppy
disks, such as the 5.25" 1.2MB PC format and 3.5"
1.44MB PC and Mac formats.



DS1
See DS.



DSA
(1) (Directory Server Agent)  An X.500 program that
looks up the address of a recipient in a Directory
Information Base (DIB), also known as white pages.
It accepts requests from the Directory User Agent
(DUA) counterpart in the workstation.

(2) (Digital Signature Algorithm)  The algorithm
used in the Digital Signature Standard (DSS).

(3) (Digital Storage Architecture)  A disk
controller standard from Digital.

(4) (Digital Signal Analyzer)  A Tektronix
oscilloscope that samples high-frequency signals.

(5) (Distributed Systems Architecture)   A Bull HN
network architecture.




DSOM
See SOM.



DSP
(1) (Digital Signal Processor)  A special-purpose
CPU used for digital signal processing (see below).
It provides extra fast instruction sequences, such
as shift and add and multiply and add, commonly
used in math-intensive signal processing
applications.

(2) (Digital Signal Processing)  A category of
techniques that analyze signals from sources such
as sound, weather satellites and earthquake
monitors.  Signals are converted into digital data
and analyzed using various algorithms such as Fast
Fourier Transform.

   Once a signal has been reduced to numbers, its
components can be isolated, analyzed and rearranged
more easily than in analog form.  DSP is used in
many fields including biomedicine, sonar, radar,
seismology, speech and music processing, imaging
and communications.

   In sound cards, DSP chips are used to compress
and decompress audio formats as well as to assist
with recording and playback and speech synthesis.
Other audio uses are the DSP chips in stereo
amplifiers, which are programmed to simulate
concert hall and cinema effects for home theater
and music listening.



DSR
(Data Set Ready)  An RS-232 signal sent from the
modem to the computer or terminal indicating that
it is able to accept data.  Contrast with DTR.



DSS
(1) (Decision Support System)
(2) (Digital Signature Standard)

(1) (Decision Support System)  An information and
planning system that provides the ability to
interrogate computers on an ad hoc basis, analyze
information and predict the impact of decisions
before they are made.

   DBMSs let you select data and derive information
for reporting and analysis.  Spreadsheets and
modeling programs provide both analysis and "what
if?" planning.  However, any single application
that supports decision making is not a DSS.  A DSS
is a cohesive and integrated set of programs that
share data and information.  A DSS might also
retrieve industry data from external sources that
can be compared and used for historical and
statistical purposes.

   An integrated DSS directly impacts management's
decision-making process and can be a very cost-
beneficial computer application.  See EIS.

(2) (Digital Signature Standard)  A National
Security Administration standard for authenticating
an electronic message.  See RSA and digital
signature.



DSTN
(Double SuperTwisted Nematic)  An LCD display that
uses an extra display layer (compensating layer)
between the main display and the rear polarizer,
resulting in an almost-pure black and white display
with little color tinge.



DSU/CSU
(Digital (or Data) Service Unit/Channel Service
Unit)  A pair of communications devices that
connect an inhouse line to an external digital
circuit (T1, DDS, etc.).  It is similar to a modem,
but connects a digital circuit rather than an
analog one.

   The CSU terminates the external line at the
customer's premises.  It also provides diagnostics
and allows for remote testing.  If the customer's
communications devices are T1 ready and have the
proper interface, then the CSU is not required,
only the DSU.

   The DSU does the actual transmission and
receiving of the signal and provides buffering and
flow control.  The DSU and CSU are often in the
same unit.  The DSU may also be built into the
multiplexor, commonly used to combine digital
signals for high-speed lines.


                  Customer side   T1 provider
                                 
 Multiplexor <> DSU <> CSU <> T1 line

      Multiplexor <> DSU/CSU <> T1 line

      Multiplexor/DSU <> CSU <> T1 line





DSX-1
(Digital Signal Cross-connect Level 1)  A standard
that defines the voltage, pulse width and plug and
socket for connecting DS-1 (T1) signals.



DTA
(Design and Test Alliance)  A group of ATE and EDA
vendors, chip makers and systems houses dedicated
to improving testing of complicated electronic
systems.



DTD
See SGML.



DTE
(Data Terminating Equipment)  A communications
device that is the source or destination of signals
on a network.  It is typically a terminal or
computer.  Contrast with DCE.



DTMF
(Dual Tone Multi Frequency)  The formal name of
touch tone (pushbutton) technology found on
telephone keypads.



DTP
See desktop publishing.



DTR
(Data Terminal Ready)  An RS-232 signal sent from
the computer or terminal to the modem indicating
that it is able to accept data.  Contrast with DSR.



DTS
(1) (Digital Termination Service)  A microwave-
based, line-of-sight communications provided
directly to the end user.

(2) (DeskTop Server)  A motorola 68000-based
network server from Banyan.

(3) (Developer Technical Support)  The tech-support
group for developers at Apple.



DUA
(Directory User Agent)  An X.500 routine that sends
a request to the Directory Server Agent (DSA) to
look up the location of a user on the network.



dual boot
A computer configuration that allows it to be
started with either one of two different operating
systems.  The dual boot feature is contained in one
of the operating systems.



dual in-line package
See DIP.



dual-scan LCD
A technique used to improve passive matrix color
screens.  The screen is divided into halves, and
each half is scanned simultaneously, thereby
doubling the number of lines refreshed per second.
It provides a sharper appearance, but still does
not approach the richness of active matrix.



dumb terminal
A display terminal without processing capability.
It is entirely dependent on the main computer for
processing.  Contrast with smart terminal and
intelligent terminal.



dump
To print the contents of memory, disk or tape
without any report formatting.  See memory dump.



Dun & Bradstreet Software
(Dun & Bradstreet Software Services, Inc., Atlanta,
GA)  A software and consulting organization formed
in 1990 as a merger of Management Science America
(MSA) and McCormack & Dodge.

   MSA was originally founded in 1963 to provide
textile consulting services.  Under the leadership
of John Imlay, who rejoined the company in 1970 as
Chairman and CEO, MSA grew rapidly in business
applications software and was the first to enter
the international marketplace in 1979.

   McCormack & Dodge was originally founded in 1969
as a packaged financial software firm and later
introduced the first integrated environment for
mainframe business applications.  In 1983, it was
acquired by The Dun & Bradstreet Corporation.

   Imlay directed the merger and headed the new
company in the development of client/server
versions of its mainframe software until his
retirement.



duplex channel
See full-duplex.



duplexed system
Two systems that are functionally identical.  They
both may perform the same functions, or one may be
standby, ready to take over if the other fails.



Duplicate file name or file not found
A DOS error message that means you are referencing
a file that does not exist or that you are renaming
a file to a file name that already does exist.



duplicate keys
Identical key data in a file.  Primary keys, such
as account number cannot be duplicated, since no
two customers or employees should be assigned the
same number.  Secondary keys, such as date, product
and city, may be duplicated in the file or
database.



DVE
See digital video effects.



DVI
(Digital Video Interactive)   An Intel compression
technique for data, audio and full-motion video.
On a CD-ROM, it provides up to 72 minutes of full-
screen video, 2 hours of half-screen video, 40,000
medium-resolution or 7,000 high-resolution images.
It compresses full-motion video at ratios greater
than 100 to 1 and still images at 10 to 1.

   Split screen capabilities allow still and moving
images side by side.  For example, a training
course could show an operation taking place along
with pictures of the components being used.

   DVI uses standard storage devices, but requires
a DVI controller board in the personal computer.
Developed by RCA's Sarnoff Research labs in
Princeton, Intel acquired it in 1988.

   Software-only versions of DVI are also
forthcoming.  See CD, CD-ROM, CD-I.



Dvorak keyboard
A keyboard layout designed in the 1930s by August
Dvorak, University of Washington, and his brother-
in-law, William Dealey.  70% of words are typed on
the home row compared to 32% with qwerty, and, more
words are typed using both hands.  In eight hours,
fingers of a qwerty typist travel 16 miles, but
only one for the Dvorak typist.

              Qwerty

   52%   Q W E R T Y U I O P
   32%    A S D F G H J K L ; '
   16%     Z X C V B N M , . /

              Dvorak

   22%   ' , . P Y F G C R L ?
   70%    A O E U I D H T N S -
    8%     ; Q J K X B M W V Z





DVST
(Direct View Storage Tube)  An early graphics
screen that maintained an image without refreshing.
The entire screen had to be redrawn for any change.



DWCFGMG.SYS
The software driver that adds Plug and Play
capability to older DOS machines.



dweeb
Slang for a very technical person.  Dweebs
sometimes call sales people "slime," anybody
interested in technology for profit rather than the
art of it.



DX
In an Intel 386 CPU, DX, or 386DX, refers to the
full 386, which contains a 32-bit data path, in
contrast to the slower 386SX, which uses a 16-bit
data path.  In an Intel 486 CPU, DX, or 486DX,
refers to the full 486, which contains the math
coprocessor, in contrast to the 486SX, which does
not have the coprocessor.

   This is a prime example of the careless naming
so common in this industry.  People have been
thoroughly confused by the DX and SX designations,
because they have entirely different meanings
depending on whether they refer to a 386 or a 486.
See 386 and 486.



DX2
A 486 with a clock-doubled CPU.  Clock doubling
doubles the internal speed of the CPU without
requiring any changes in the chip's external
connections.  For example, the 486DX2/66 has an
internal speed of 66MHz, while its external bus
from the CPU to RAM runs at 33MHz.  The 486DX2/50
has an internal speed of 50MHz and 25MHz
externally.  Intel calls the DX2 a "Speed Doubler"
chip.

   Note that the 486DX2/66 is often tagged as
simply a 486/66.  Since there is no full DX 66MHz
486, the DX2 designation is often dropped.  This is
not true of the 486/50.  The 486DX/50 is a true
50MHz machine internally and externally, while the
486DX2 is only 50MHz internally.  See iCOMP.

      DX2 CPU       Internal    External
     486DX2/66       66MHz       33MHz
     486DX2/50       50MHz       25MHz
     486DX/50        50MHz       50MHz

      DX4 CPU       Internal    External
     486DX4/75        75MHz      25MHz
     486DX4/100      100MHz      33MHz





DX4
A 486 with a clock-tripled CPU.  Clock tripling
triples the internal speed of the CPU without
requiring any changes in the chip's external
connections.  DX4s come in 75MHz and 100MHz
versions that access RAM at 25MHz and 33MHz
respectively.  See DX2 and iCOMP for speed
comparisons.



DXF
An AutoCAD 2-D graphics file format.  Many CAD
systems import and export the DXF format for
graphics interchange.



dyadic
Two.  Refers to two components being used.



dye diffusion
See thermal dye diffusion.



dye polymer recording
An optical recording technique that uses dyed
plastic layers as the recording medium.  WORM disks
typically use a single layer, and erasable disks
use two layers: a top retention layer and a bottom
expansion layer.  A bit is written by shining a
laser through the retention layer onto the
expansion layer, which heats the area and forms a
bump that expands into the retention layer.  The
retention layer bumps are the actual bits read by
the unit.  To erase a bit, another laser (different
wavelength) strikes the retention layer and the
bump subsides.



dye sublimation
See thermal dye transfer.



dynamic
Refers to operations performed while the program is
running.  The expression, "buffers are dynamically
created," means that space was created when
actually needed, not reserved beforehand.



dynamic address translation
In a virtual memory system, the ability to
determine what the real address is at the time of
execution.



dynamic binding
Linking a routine or object at runtime based on the
conditions at that moment.  See polymorphism.



dynamic compression
The ability to compress and decompress data in
realtime; for example, as it's being written to or
read from the disk.



Dynamic Data Exchange
See DDE.



dynamic link
The connection established at runtime from one
program to another.



dynamic link library
A set of program routines that can be called at
runtime as needed.  A dynamic link is the
communications mechanism that lets one program
launch and execute another on the fly.  It lets
feature-laden software run in minimal amounts of
memory by building functions as separate routines
that are called into memory when required.

   A dynamic link library is often written in
reentrant code so the routines can be shared by
several applications at the same time.

   In the DOS world, there was never a solid way to
dynamically link routines.  ISRs and TSRs were
created for this purpose, but they were not
formally sanctioned by Microsoft and often caused
conflict.

   Windows, on the other hand, uses the dynamic
link library as a standard way of linking and
sharing functionality.  In Windows, each program
module is called a DLL.  DLLs cannot be launched
directly by the user.  The user launches an
application by loading the .EXE program, which in
turn, calls for and loads one or more .DLL modules.



dynamic network services
Realtime networking capabilities, such as adaptive
routing, automatically reconfiguring the network
when a node is added or deleted and the ability to
locate any user on the network.



dynamic node addressing
A network technology that dynamically assigns
machine addresses to nodes upon startup.  For
example, when a station is turned on in an
AppleTalk network, it identifies itself to the
network.  If its number has been taken in the
meantime by another node, it creates a new one
using a random number generator.



dynamic RAM
The most common type of computer memory, also
called D-RAM ("dee-RAM") and DRAM.  It usually uses
one transistor and a capacitor to represent a bit.
The capacitors must be energized hundreds of times
per second in order to maintain the charges.
Unlike firmware chips (ROMs, PROMs, etc.) both
major varieties of RAM (dynamic and static) lose
their content when the power is turned off.
Contrast with static RAM.

   In memory advertising, dynamic RAM is often
erroneously stated as a package type; for example,
"DRAMs, SIMMs and SIPs on sale."  It should be
"DIPs, SIMMs and SIPs," as all three packages
typically hold dynamic RAM chips.



dynamic range
A range of signals from the weakest to the
strongest.



dynamic SQL
See embedded SQL.



DYNASTY
An application development system for enterprise
client/server environments from Dynasty
Technologies, Inc., Naperville, IL.  Introduced in
1993, it is a repository-driven system that
supports Windows, Mac and Motif clients and NT,
OS/2 and major UNIX servers and databases.  It
provides partitioning for creating three-tier
applications.  DYNASTY generates C and SQL code.



DYNIX/ptx
Sequent Computer's UNIX-based operating system that
runs on its Symmetry series of x86 symmetric
multiprocessing (SMP) servers.



dynlink
See dynamic link.



E
See exponent.



e-beam
See electron beam.



e-disk
(Emulated-disk)  Same as RAM disk.



e-forms
(Electronic-FORMS)  See forms software.



e-mail
See electronic mail.



E-time
See execution time.



E1
The European counterpart to T1, which transmits at
2.048 Mbits/sec.  See DS for chart.



EAM
(Electronic Accounting Machine)  Same as tabulating
equipment.



early binding
Assigning types in the compilation phase.  See
binding time.



EAROM
(Electrically Alterable ROM)  Same as EEPROM.



earth station
A transmitting/receiving station for satellite
communications.  It uses a dish-shaped antenna for
microwave transmission.



Easel
(Easel Corporation, Burlington, MA)  A software
tools company founded in 1981.  Easel has two lines
of client/server tools: one based on its ESL
technology which includes ESL Workbench for OS/2
and ESL for Windows.  The other is its object-
oriented Object Studio based on Smalltalk.
Sometimes, the name Easel, by itself, is used to
refer to the Easel Renovator screen scraper, now
called ESL Renovator.



Easel Workbench
See ESL Workbench.



Easter Egg
An undocumented function hidden in a program.
Easter Eggs are secret "goodies" that are found by
accident or word of mouth.  For example, in Windows
3.1, to see the names of the people who worked on
the project, open the About Program Manager dialog
box (Help, About) and double click on the Windows
icon at the upper left while holding down Ctrl and
Shift.  Click OK, then open the box again.  Ctrl-
Shift Double click again and note the dedication.
Click OK and repeat once more.



easy to learn and use
Easy to learn refers to software that is well
designed and capable of being used right away.  If
you make the program work with little problem, it's
easy to learn.

   Easy to learn implies easy to use right away,
but it does not imply easy to use after you're
familiar with it.  The menus that coddled you in
the beginning can become tiresome when used
constantly.  Advanced programs have a macro
recorder that lets you store a series of menu
selections and execute them automatically.



EasyCAD 2
A full-featured PC CAD program from Evolution
Computing, Tempe, AZ, that is known for its ease of
use.  EasyCAD users can migrate to FastCAD, which
looks almost identical on screen, but provides
multiple windows and is designed for high-speed
operations.



Easytrieve
See CA-Easytrieve.



EBCDIC
(Extended Binary Coded Decimal Interchange Code)
Pronounced "eb-suh-dick."  The binary code for text
as well as communications and printer control from
IBM.  This data code originated with the System/360
and is still used in IBM mainframes and most IBM
midrange computers.  It is an 8-bit code (256
combinations) that stores one alphanumeric
character or two decimal digits in a byte.

   EBCDIC and ASCII are the two codes most widely
used to represent data.



EBCDIC chart

ͻ
                     EBCDIC                     
 Extended Binary Coded Decimal Interchange Code 
                                                
 00 Null              40 (3)  80      C0 {   
 01 Start of heading  41 (4)  81  a   C1 A   
 02 Start of text     42      82  b   C2 B   
 03 End of text       43      83  c   C3 C   
 04 Select            44      84  d   C4 D   
 05 Horizontal Tab    45      85  e   C5 E   
 06 Required New Line 46      86  f   C6 F   
 07 Delete            47      87  g   C7 G   
 08 Graphic Escape    48      88  h   C8 H   
 09 Superscript       49      89  i   C9 I   
 0A Repeat            4A     8A      CA (5) 
 0B Vertical Tab      4B .    8B      CB     
 0C Form Feed         4C <    8C      CC     
 0D Carriage return   4D (    8D      CD     
 0E Shift out         4E +    8E      CE     
 0F Shift in          4F     8F      CF     
 10 Data link escape  50 &    90      D0 }   
 11 Device control 1  51      91  j   D1 J   
 12 Device control 2  52      92  k   D2 K   
 13 Device control 3  53      93  l   D3 L   
 14 Rest/Enable Pres  54      94  m   D4 M   
 15 New Line          55      95  n   D5 N   
 16 Backspace         56      96  o   D6 O   
 17 Prog/Oper Comm    57      97  p   D7 P   
 18 Cancel            58      98  q   D8 Q   
 19 End of medium     59      99  r   D9 R   
 1A Unit Backspace    5A !    9A      DA     
 1B Customer Use 1    5B $    9B      DB     
 1C File Separator    5C     9C      DC     
 1D Group Separator   5D )    9D      DD     
 1E Record Separator  5E ;    9E      DE     
 1F (1)               5F Ŀ   9F      DF     
 20 Digit Select      60 -    A0      E0 \   
 21 SOS               61 /    A1  ~   E1 (6) 
 22 Field Separator   62      A2  s   E2 S   
 23 Word Underscore   63      A3  t   E3 T   
 24 (2)               64      A4  u   E4 U   
 25 Line Feed         65      A5  v   E5 V   
 26 End Trans Block   66      A6  w   E6 W   
 27 Escape            67      A7  x   E7 X   
 28 Set Attribute     68      A8  y   E8 Y   
 29 Start Field Ext.  69      A9  z   E9 Z   
 2A Set Mode/Switch   6A |    AA      EA     
 2B Ctrl Seq Prefix   6B ,    AB      EB     
 2C Modify Field Atr  6C %    AC      EC     
 2D Enquiry           6D -    AD      ED     
 2E Acknowledge       6E >    AE      EE     
 2F Bell              6F ?    AF      EF     
 30                   70      B0      F0 0   
 31                   71      B1      F1 1   
 32 Synchronous Idle  72      B2      F2 2   
 33 Index Return      73      B3      F3 3   
 34 Pres Position     74      B4      F4 4   
 35 Transparent       75      B5      F5 5   
 36 Numeric Backspace 76      B6      F6 6   
 37 End of Trans      77      B7      F7 7   
 38 Subscript         78      B8      F8 8   
 39 Indent Tab        79 `    B9      F9 9   
 3A Required Frm Feed 7A :    BA      FA     
 3B Customer Use 3    7B #    BB      FB     
 3C Device Ctrl 4     7C @    BC      FC     
 3D Negative Ack      7D '    BD      FD     
 3E                   7E =    BE      FE     
 3F Substitute        7F "    BF      FF (7) 
ͼ
  (1) Bypass/Inhibit Presentation
  (2) Intermediate Trans Block/
       Interchange Unit Separator
  (3) Space
  (4) Required Space
  (5) Syllable Hyphen
  (6) Numeric Space
  (7) Eight Ones





EBL
(Extended Batch Language)  A shareware programming
language by Frank Canova that allows for more
complex programming in DOS batch files.



ECC memory
(Error-Correcting Code memory)  A memory system
that tests for and corrects errors on the fly.  It
uses circuitry that generates checksums to correct
errors greater than one bit.



ECCO
A Windows PIM from Arabesque Software, Bellevue,
WA.  ECCO provides a phone book, calendar, to-do
list, outlining and notetaking.  It is noted for
its tightly integrated and sophisticated functions.



ECF
(Enhanced Connectivity Facilities)  IBM software
that allows DOS PCs to query and download data from
mainframes as well as issue mainframe commands.  It
also allows printer output to be directed from the
PC to the mainframe.  It uses the SRPI interface
and resides in the PC (client) and mainframe
(server).  Applications issue SRPI commands to
request services.



echo
(1) Same as echoplex.

(2) A DOS and OS/2 screen command that displays
messages and turns off/on screen responses.  See
DOS batch file.



echo cancellation
A high-speed modem technique that isolates and
filters out unwanted signals caused by echoes from
the main transmitted signal.  This permits full-
duplex modems to send and receive on the same
frequency.

   Telephone networks often use echo cancellers in
addition to or in place of echo suppressors.
Network-based echo cancellation can interfere with
modems that do their own, such as V.32, so a method
is provided for those modems to disable network
echo cancellers.



echo check
In communications, an error checking method that
retransmits the data back to the sending device for
comparison with the original.



echo suppressor
A communications technique that turns off reverse
transmission in a telephone line, thus effectively
making the circuit one way.  It is used to reduce
the annoying effects of echoes in telephone
connections, especially in satellite circuits.



echoplex
A communications protocol that transmits the
received data back to the sending station allowing
the user to visually inspect what was received.



ECL
(Emitter-Coupled Logic)  A variety of bipolar
transistor that is noted for its extremely fast
switching speeds.



ECLIPSE
A series of 32-bit minicomputers from Data General.
The development of the initial 32-bit ECLIPSE
MV/8000 was the subject of Tracy Kidders' best-
selling book, "Soul of a New Machine" published in
1981 by Little, Brown and Company.



ECMA
(European Computer Manufacturers Association)  An
organization devoted to international standards.
Address: Rue du Rhone 114, CH-1204 Geneva,
Switzerland.



ECNE
See NetWare certification.



ECP
(Enhanced Capabilities Port)  See IEEE 1284.



ED
(1) (Extra High Density)  Refers to 2.88M floppy
disks.

(2) (EDitor)  An early UNIX line editor that
contained functionality later incorporated into vi.



EDA
(1) (Electronic Design Automation)  Using the
computer to design and simulate the performance of
electronic circuits on a chip.  See ATE.

(2) (Electronic Document Authorization)
Authorizing certificates used to identify public
keys for encrypting data under the RSA method.



EDA/SQL
(Enterprise Data Access/SQL)  Software from
Information Builders, Inc., New York, that provides
a common interface between a wide variety of SQL
programs and SQL databases.  It also allows queries
on data from different types of databases at the
same time.



edge connector
The protruding part of an expansion board that is
inserted into an expansion slot.  It contains a
series of printed lines that go to and come from
the circuits on the board.  The number of lines
(pins) and the width and depth of the lines are
different on the various interfaces (ISA, EISA,
PCI, Micro Channel, etc.).



edge path adapter
See EPA.



EDI
(Electronic Data Interchange)  The electronic
communication of business transactions, such as
orders, confirmations and invoices, between
organizations.  Third parties provide EDI services
that enable organizations with different equipment
to connect.  See X12, Tradacoms and EDIFACT.



EDIFACT
(Electronic Data Interchange For Administration
Commerce and Transport)  An ISO standard for EDI
that is proposed to supersede both X12 and
Tradacoms standards to become the worldwide
standard.



edit
To make a change to existing data.  See update.



edit checking
Same as validity checking.



edit instruction
A computer instruction that formats a field for
display or printing.  Using an edit mask, it
inserts decimal points, commas and dollar signs
into the data.



edit key
A key combination or function key that changes the
program into edit mode when pressed.



edit mask
A pattern of characters that represent formatting
codes through which data is filtered for display or
printing.  See picture.



edit mode
An operational state in a program that allows
existing data to be changed.



edit program
(1) A data entry program that validates user input
and stores the newly created records in the file.

(2) A program that allows users to change data that
already exists in a file.  See update.



edit routine
A routine in a program that tests for valid data.
See validity checking.



editable PostScript
A file of PostScript commands that can be edited by
a word processor or other program.  This allows
PostScript documents to be changed without
requiring the use of the application that
originally created it.



editor
See text editor and linkage editor.



EDL
See nonlinear video editing.



Edlin
An archaic text editor used in DOS.  The OS/2
counterpart is SSE.  See DOS Edlin.



EDP
(Electronic Data Processing)  The first name used
for the computer field.



EDRAM
(Enhanced DRAM)  A high-speed DRAM chip developed
by Ramtron International Corporation, Colorado
Springs, CO.  It allows overlap of a read at the
trailing end of a write operation to obtain its
speed.



education
Teaching concepts and perspectives.  Computer
education includes computer systems and information
systems.  Contrast with training.



edutainment
Educational material that is also entertaining.



EE
See Extended Edition.



EEMS
See EMS.



EEPROM
(Electrically Erasable Programmable Read Only
Memory)  A memory chip that holds its content
without power.  It can be erased, either within the
computer or externally and usually requires more
voltage for erasure than the common +5 volts used
in logic circuits.  It functions like non-volatile
RAM, but writing to EEPROM is slower than writing
to RAM.

   EEPROMs are used in devices that must keep data
up-to-date without power.  For example, a price
list could be maintained in EEPROM chips in a point
of sale terminal that is turned off at night.  When
prices change, the EEPROMs can be updated from a
central computer during the day.  EEPROMs have a
lifespan of between 10K and 100K write cycles.  See
flash memory.



eesa
See EISA and ESA/370.



EFF
(Electronic Frontier Foundation)  An organization
founded in 1990 by Mitchell Kapor and John Perry
Barlow dedicated to raising public awareness of the
opportunities and challenges posed by computing and
telecommunications.  Address: 155 Second St.,
Cambridge, MA 02141, 617/864-0665.



EFT
(Electronic Funds Transfer)  The transfer of money
from one account to another by computer.



EGA
(Enhanced Graphics Adapter)  An IBM video display
standard that provides medium-resolution text and
graphics.  It supports previous display modes and
requires a digital RGB Enhanced Color Display or
equivalent monitor.  EGA was superseded by VGA.
See PC display modes.



EGP
(Exterior Gateway Protocol)  A protocol that
broadcasts TCP/IP addresses to the gateway in
another network.



EHLLAPI
See HLLAPI.



EIA
(Electronic Industries Association)  A membership
organization founded in 1924 as the Radio
Manufacturing Association.  It sets standards for
consumer products and electronic components.  In
1988, it spun off its Information &
Telecommunications Technology Group into a separate
organization called the TIA.  Address: 2001
Pennsylvania Ave., N.W., Washington, DC 20006,
202/457-4900.



EIA-232
See RS-232.



EIA-422, 423, 449
See RS-422, 423, 449


EIA-485
See RS-485.



EIA-568
An EIA standard for telecommunications wiring in a
commercial building.  See cable categories.



Eiffel
An object-oriented programming language developed
by Bertrand Meyer, Interactive Software Engineering
Inc., Goleta, CA.  It runs on DOS, OS/2 and most
UNIX platforms.  The Eiffel compiler generates C
code, which can be modified and recompiled with a C
compiler.



EIS
(Executive Information System)  An information
system that consolidates and summarizes ongoing
transactions within the organization.  It should
provide management with all the information it
requires at all times from internal as well as
external sources.  Increasingly, EISs are providing
some of the "what if?" manipulation functions of a
DSS (decision support system); however, a DSS
provides true modeling capabilities. See DSS.



EISA
(Extended ISA)  Pronounced "ee-suh."  A PC bus
standard that extends the 16-bit ISA bus (AT bus)
to 32 bits and provides bus mastering.  ISA cards
can plug into an EISA slot.  It was announced in
1988 as a 32-bit alternative to the Micro Channel
that would preserve investment in existing boards.
EISA is also used in various workstations from HP
and others.

   EISA still runs at the slow 8MHz speed of the
ISA bus in order to accomodate all the ISA cards
that may be plugged into it.  PCI and VL-bus local
buses provide independent data paths and higher
speeds than EISA.



EL
See electroluminescent.



electricity
The flow of electrons in a circuit.  The speed of
electricity is the speed of light (approximately
186,000 miles per second).  In a wire, it is slowed
due to the resistance in the material.

   Its pressure, or force, is measured in volts and
its flow, or current, is measured in amperes.  The
amount of work it produces is measured in watts
(amps X volts).



electrode
A device that emits or controls the flow of
electricity.



electroluminescent
A flat panel display that provides a sharp, clear
image and wide viewing angle.  It contains a
powdered or thin film phosphor layer sandwiched
between an x-axis and a y-axis panel.  When an x-y
coordinate is charged, the phosphor in that
vicinity emits visible light.  Phosphors are
typically amber, but green is also used.



electrolyte
In a rechargeable battery, the material that allows
electricity to flow from one plate to another by
conducting ions.



electromagnet
A magnet that is energized by electricity.  A coil
of wire is wrapped around an iron core.  When
current flows in the wire, the core generates an
energy called magnetic flux.



electromagnetic interference
See EMI.



electromagnetic radiation
The energy that exists in all things, including
humans, which incorporates cosmic rays, gamma rays,
x-rays, ultraviolet light, visible light, infrared
light and radar.



electromagnetic spectrum
The range of electromagnetic radiation in our known
universe, which includes visible light as outlined
below.  Parts of the radio spectrum are still
unasigned, but will eventually be used for some
commercial communications purpose.


          cosmic rays           higher
                 frequencies
          gamma rays
                 smaller
          x-rays                wavelengths
        
          ultraviolet
        
          VISIBLE LIGHT
        
          infrared
        
          microwaves
  
   radio  amateur radio,        larger
   waves   aeronautical,        wavelengths
           cellular phone,
           taxis, aircraft,     lower
           TV, FM, AM           frequencies
  
          long waves





electromechanical
The use of electricity to run moving parts.  Disk
drives, printers and motors are examples.
Electromechanical systems must be designed for the
eventual deterioration of moving parts.



electromotive force
The pressure in an electric circuit measured in
volts.



electron
An elementary particle that circles the nucleus of
an atom.  Electrons are considered to be negatively
charged.



electron beam
A stream of electrons, or electricity, that is
directed towards a receiving object.



electron gun
A device which creates a fine beam of electrons
that is focused on a phosphor screen in a CRT.



electron tube
Same as vacuum tube.



electronic
The use of electricity in intelligence-bearing
devices, such as radios, TVs, instruments,
computers and telecommunications.  Electricity used
as raw power for heat, light and motors is
considered electrical, not electronic.

   Although coined earlier, "Electronics" magazine
(1930) popularized the term.  The magazine
subheading read "Electron Tubes - Their Radio,
Audio, Visio and Industrial Applications."  The
term was derived from the electron (vacuum) tube.



electronic circuit
See circuit and digital circuit.



electronic data interchange
See EDI.



electronic data processing
See EDP.



electronic design automation
See EDA.



electronic forms
See forms software.



Electronic Frontier Foundation
See EFF.



electronic funds transfer
See EFT.



Electronic Industries Association
See EIA.



electronic mail
Also called e-mail, it is the transmission of memos
and messages over a network.  Users can send mail
to a single recipient or broadcast it to multiple
users.  Sophisticated systems prompt recipients for
a reply if they haven't responded within a certain
time frame.  With multitasking workstations, mail
can be delivered and announced while the user is
working in an application.  Otherwise, mail is sent
to a simulated mailbox in the network server or
host computer, which must be interrogated.

   An electronic mail system requires a messaging
system, which provides the store and forward
capability, and a mail program that provides the
user interface with its send and receive functions.

   The fax machine has become the most universal
electronic mail today, showing the power of a
common standard.  However, it is not technically
e-mail because the text cannot be edited at the
other end without scanning it and using text
recognition (OCR) software.  See messaging system
and EDI.



Electronic Mail Association
See EMA.   Remember... try the acronymn first!



Electronic Message Service
See EMS (2).



electronic messaging
See electronic mail and messaging system.



electronic performance support system
See EPSS.



electronic printer
A printer that uses electronics to control the
printing mechanism, such as a laser printer and
certain line printers.



electronic publishing
Providing information in electronic form to readers
or subscribers of the service.  See information
utility.



electronic software distribution
See ESD.



electronic software licensing
See ESL.



electronic switch
An on/off switch activated by electrical current.



electronic typewriter
See memory typewriter and word processing.



electrophotographic
The printing technique used in copy machines and
laser printers.  A negative image made of dots of
light is painted onto a photosensitive drum or belt
that has been electrically charged.  The light
comes from a laser, LEDs or liquid crystals that
shutter a light source.

   Wherever light is applied, the drum becomes
uncharged.  A toner (dry ink) is applied and
adheres to the charged areas of the drum.  The drum
transfers the toner to the paper, and pressure and
heat fuse the toner and paper permanently.

   Some electrophotographic systems use a positive
approach in which the toner is attracted to the
laser-produced latent image.



electrosensitive printer
A dot matrix printer that burns away dots on the
outer silver coating of a special black paper.



electrostatic
Stationary electrical charges in which no current
flows.



electrostatic plotter
A plotter that uses a special paper that is charged
as it passes by a line of electrodes.  Toner is
then applied to the charged paper.  Models print in
in black and white or color, and some handle paper
up to six feet wide.



electrostatic printer
Same as electrostatic plotter.



elegant program
A program that is simple in design and uses the
least amount of computer resources (memory, disk,
etc.).



elevator
Also called a thumb, it is a square box that slides
within a scroll bar.  The elevator is dragged up
and down to position the text or image on screen.



elevator seeking
A disk access technique that processes multiple
requests in a priority based upon which ones are
closest to the current position of the read/write
head.



ELF
(Extemely Low Frequency)  See low radiation.



elite
A typeface that prints 12 cpi.



em
In typography, a unit of measure equal to the width
of the capital letter M in a particular font.



EMA
(1) (Enterprise Management Architecture)  Digital's
stategic plan for integrating network, system and
application management.  It provides the operating
environment for managing a multi-vendor network.

(2) (Electronic Mail Association)  A membership
organization founded in 1983 with over 250 vendor
and user companies involved in electronic messaging
and information exchange.  Concerns include
marketing e-mail within the corporation, privacy,
security, interconnection and standards.  Address:
1555 Wilson Blvd., Suite 300, Arlington, VA 22209,
703/875-8620.



EMACS
(Editor MACroS)  A UNIX text editor developed at
MIT that is used for writing programs.  It provides
a wide variety of editing features including
multiple windows.



email
See electronic mail.



EMBARC
(EMBARC Communications Service, Boyton Beach, FL)
A Motorola subsidiary that provides wireless
broadcasting of mail and news to mobile computers
that have a Motorola NewStream, SkyTel SkyStream,
PCMCIA NewsCard or similar receiver.  EMBARC stands
for Electronic Mail Broadcast to a Roaming
Computer.  It uses a 930-931MHz channel licensed to
Motorola and can handle long messages of 30,000
characters and more.



embedded command
(1) A command inserted within text or other codes.

(2) In word processing, a command within the text
that directs the printer to change fonts, print
underline, boldface, etc.  The command is inserted
when the user selects a layout change.  Commands
are often invisible on screen, but can be revealed
if required.



embedded controller
Controller circuitry built into a device or on the
main system board in contrast with a removable card
or module.



embedded SQL
SQL statements that are written into a high-level
programming language such as C or Pascal.  In a
preprocessing stage, the SQL code is converted into
function calls, which may be optimized to provide
the fastest results.  If the programmer knows
exactly what the query is going to do, and the
query does not change, it is called static SQL.  If
the query requires user input at runtime, it is
called dynamic SQL.  If the client program passes
the SQL statements directly to the database server
without any intermediate step, it is called
passthrough SQL.



embedded system
A specialized computer used to control a device
such as an automobile, appliance or space vehicle.
Operating system and application functions are
often combined in the same program.



Emerald Bay
A PC database engine from Ratliff Software
Productions, Inc., Montrose, CA, designed to hold
all forms of information, including voice.
Introduced in 1988, it was written by Wayne
Ratliff, creator of dBASE II.



EMI
(ElectroMagnetic Interference)  Electromagnetic
waves that eminate from an electrical device.  It
often refers to both low-frequency waves from
electromechanical devices and high-frequency waves
(RFI) from chips and other electronic devices.
Allowable limits are governed by the FCC.



emitter
The supply of current in a bipolar transistor.
Same as source in a MOS transistor.



emitter-coupled logic
See ECL.



EMM
(Expanded Memory Manager)  Software that manages
expanded memory (EMS).  In XTs and ATs, expanded
memory boards must also be used.  In 386s and up,
the EMM converts extended memory into EMS.



EMM386
See DOS EMM386.EXE.



emoticon
(EMOTional ICON)  An expression of emotion in a
typed message using character combinations.  The
following examples are viewed sideways.

  :)    original smiley face
  :-)   smile
  :-(   frown
  ;-)   wink
  :-D   big smile
  :-O   mouth open in amazement
  :-Q   tounge hanging out in nausea
  :-{)  smile (user has moustache)
  :-{)} moustache and beard
  8-)   smile (user wears glasses)
  (-:   smile (user left handed or Australian)
  :*)   red nosed smile, suggesting inebriation
  *<|:{)}  Santa Claus!
  @:{)===  sikh with turban and long beard


   For an extensive list of more than 650
emoticons, read "Smileys" by David Sanderson,
published by O'Reilly & Associates, Inc., ISBN 1-
56592-041-4.





EMS
(1) (Expanded Memory Specification)
(2) (Electronic Message Service)
(3) (Enterprise Messaging Server)

(1) (Expanded Memory Specification)  A technique
for increasing memory in DOS PCs.  It allows DOS to
work with up to 32MB of extra memory by bank
switching segments of EMS memory into conventional
memory.  A 64KB chunk of upper memory (UMA) must be
reserved for the EMS page frame, the tunnel through
which the CPU accesses the EMS memory.

   In older XTs and ATs, EMS is installed by
plugging in an EMS memory board and adding an EMS
driver.  In 386s and up, extended memory is turned
into EMS memory by a software memory manager.  All
modern memory managers, such as EMM386 (DOS 5 and
up), QEMM and 386MAX, can dynamically allocate
expanded memory as needed, but the 64KB page frame
must be reserved at startup if EMS is to be used at
any time during the session.

   In order to use EMS, the application is either
written to use it directly (Lotus 1-2-3 Ver. 2.x,
AutoCAD, etc.) or the application is run in an
environment that uses it, such as DESQview.
Windows does not use EMS, but supports it for DOS
applications that require it.



             
               Extended  
                Memory   
                         
  -----1024KĴ
       (1M)  UMA (upper 
            memory area)
                           Ŀ
            Ŀ    EMS memory  
             page frame                  
                          
                                          
        640KĴ    Circuits on   
                            the EMS board 
                            remap the     
            Conventional    requested EMS 
  Normal        Memory       area into the 
  Range                      page frame,   
   of                        which DOS     
   DOS                       can address.  
                           
  -----   0K



             Expanded versus Extended
Expanded memory (EMS) and extended memory are not
the same.  EMS can be installed in XT-class
machines and up, whereas extended memory requires
at least a 286.  EMS broke the 1MB memory barrier
in the early days, but since Windows and DOS-
extended applications also break the 1MB barrier
and use regular contiguous memory beyond 1MB
(extended memory), EMS is only used for older DOS
applications.

   For an excellent, detailed book on EMS, extended
memory and more, read "DOS Beyond 640K," 2nd Ed.,
by James Forney, ISBN 0-8306-3744-3.


             EMS History and Versions
   In 1984, Lotus, Intel and Microsoft introduced
EMS (LIM EMS), which added up to 8MB of RAM.  By
Version 3.2, it was widely-supported, but limited
to one 64K page frame (four 16K pages) only in
upper memory (UMA).

   AST, Quadram and Ashton-Tate later introduced
Enhanced EMS (EEMS), letting the page frame take
the full 1M address space (64 16K pages), allowing
programs such as DESQview to multitask large
applications within conventional memory.

   In 1987, Lotus, Intel and Microsoft introduced
Version 4.0, increasing memory to 32MB and
incorporating the EEMS standard.

(2) (Electronic Message Service)  The part of the
radio spectrum assigned to electronic messaging
over digital satellite circuits.

(3) (Enterprise Messaging Server)  Original name
for Microsoft's Exchange Server.



EMS emulator
Before the 386, it referred to software for
8086/88s and 286s that simulated EMS memory in
extended memory or disk.  It was a low-cost
alternative to an EMS board, but was slower.

   Starting with the 386, it refers to a memory
manager (EMM) that creates EMS out of extended
memory.  Technically, the 386 is really not
emulating anything.  The 386 can map any memory to
any other memory, thus it is merely mapping memory
according to the EMS specification.



EMS memory manager
See EMM and EMS emulator.



emulation mode
An operational state of a computer when it is
running a foreign program under emulation.



emulator
A device that is built to work like another.  A
computer can be designed to emulate another model
and execute software that was written to run in the
other machine.  A terminal can be designed to
emulate various communications protocols and
connect to different networks.  The emulator can be
hardware, software or both.



en
In typography, a unit of measure equal to one half
the width of an em.  An en is typically the width
of one numeric digit.



enable
To turn on.  Contrast with disable.



Enable/OA
An integrated software package for PCs from Enable
Software, Inc., Ballston Lake, NY.  It is noted for
being a very comprehensive package rivaling many
stand-alone programs.  Version 4.0 also runs under
UNIX.



Encapsulated PostScript
A PostScript file format that contains PostScript
code for the document as well as optional preview
images in TIFF, Windows Metafile or Macintosh PICT
formats.  The PostScript code drives a PostScript
printer directly, and the preview formats allow the
image to be manipulated on screen.  DOS and OS/2
files use an EPS extension.



encapsulation
(1) In object-oriented programming, making the data
and processing private within an object, which
allows it to be modified without causing problems
elsewhere in the program.

(2) In communications, inserting the frame header
and data from a higher level protocol into the data
frame of a lower level protocol.



Encina
A UNIX-based TP monitor from Transarc Corporation,
Pittsburgh, PA, that is layered over OSF's
Distributed Computing Environment (DCE).  IBM's
CICS/6000 TP monitor is based on Encina, and IBM
acquired Transarc in 1994.  Encina and Novell's
Tuxedo are the major TP monitors in the UNIX
client/server environment.



encipher
To encode data for security purposes.  See
encryption.



encode
(1) To assign a code to represent data, such as a
parts code.

(2) Same as encipher or encrypt.  See encryption.



Encore
(Encore Computer Corporation, Ft. Lauderdale, FL)
A computer company founded in 1983 that specializes
in multiprocessing and realtime systems.  Its
Motorola 88110-based Infinity line provides SMP
systems and massively parallel systems scalable to
2,048 CPUs running UMAX V, Encore's version of UNIX
System V.

   Encore uses mainframe-like channels and
architecture for high I/O speed between processors.
Its realtime computers stem from Gould's computer
division that it acquired in 1989.  Also from Gould
comes Reflective Memory technology, a high-speed
bus that allows multiple memories to be read and
written simultaneously.



encryption
Using cryptography to encode data for security
purposes for transmission over a public network.
The original text, or plaintext, is converted into
a coded equivalent called ciphertext via an
encryption algorithm.  The ciphertext is decoded
(decrypted) at the receiving end with the use of a
decryption key.

             Secret versus Public Key
There are two methods of encrypting data.  The
traditional method uses a secret key, such as the
DES standard.  Both sender and receiver use the
same key.  This is the fastest method, but
transmitting the secret key to the recipient in the
first place is not secure.

   The second method is public-key cryptography,
such as RSA, which uses both a private and a public
key.  Each recipient has a private key that is kept
secret and a public key that is published for
everyone.  The sender looks up the recipient's
public key and uses it to encrypt the message.  The
recipient uses the private key to decrypt the
message.

   If speed is an issue, the public-key method can
be used to send the secret key followed by the
message encrypted with the secret key.  See DES and
RSA.



end key
A keyboard key commonly used to move the cursor to
the bottom of the screen or file or to the next
word or end of line.



end points
In vector graphics, the two ends of a line
(vector).  In 2-D graphics, each end point is
typically two numbers representing coordinates on x
and y axes.  In 3-D, each end point is made up of
three numbers representing coordinates on x, y and
z axes.



end user
Same as user.



end user computing
Using personal computers.



endian
See big endian.



endless loop
A series of instructions that are constantly
repeated.  It can be caused by an error in the
program or it can be intentional; for example, a
screen demo on continuous replay.



endnote
See footnote.



Energy Star
Power conservation requirements set forth by the
Environmental Protection Agency of the U.S.
Government.  In order to display the Energy Star
logo, devices (PCs, monitors, printers, etc.) must
use less than 30 watts of power when inactive.



Enfin
A client/server development system based on the
Smalltalk language.  It is now part of the Object
Studio environment.  See Object Studio.



engine
(1) A specialized processor, such as a graphics
processor.  Like any engine, the faster it runs,
the quicker the job gets done.  See graphics engine
and printer engine.

(2) Software that performs a primary and highly
repetitive function such as a database engine,
graphics engine or dictionary engine.

(3) Slang for processor.



engineering cylinder
See diagnostic tracks.



engineering drawing sizes

     A - 8 1/2 x 11
     B - 11 x 17
     C - 17 x 22
     D - 22 x 34
     E - 34 x 44





Enhanced Connectivity Facilities
See ECF.



Enhanced IDE
A hard disk and CD-ROM interface that supports up
to four hard disks rather than only two.  It also
increases the data transfer rate up to 13MB.  See
hard disk.



Enhanced keyboard
An IBM 101-key keyboard that superseded the PC and
AT keyboards.  It has a separate cursor key cluster
located between the original numeric/cursor keypad
and the letter keys.



enhanced parallel port
See EPP.



enhanced service provider
See ESP.



enhancement
Any improvement made to a software package or
hardware device.



ENIAC
(Electronic Numerical Integrator And Calculator)
The first operational electronic digital computer
developed for the U.S. Army by John Eckert and John
Mauchly at the University of Pennsylvania.
Completed in 1946, it was decimal-based, used
18,000 vacuum tubes, took up 1,800 square feet and
performed 5,000 additions/second.  Today, the
equivalent technology is used in a watch.



enquiry character
In communications, a control character that
requests a response from the receiving station.



ENS
(Enterprise Networking Services)  A variety of
networking services from Banyan that have been
separated from its VINES network operating system
and made available on other platforms such as
NetWare, Windows NT and AIX.  They include the
VINES Streettalk directory, network management and
electronic mail services.



enter key
See return key.



enterprise
The entire organization.  See enterprise
networking.



enterprise data
Centralized data that is shared by many users
throughout the organization.



enterprise model
A model of how an organization does business.
Information systems are designed from this model.



enterprise network
A geographically-dispersed network under the
jurisdiction of one organization.  It often
includes several different types of networks and
computer systems from different vendors.



enterprise networking
The networking infrastructure in a large enterprise
with multiple computer systems and networks of
different types is extraordinarily complex.  Due to
the myriads of interfaces that are required, much
of what goes on has little to do with the real data
processing of the payroll and orders.  An enormous
amount of effort goes into planning the integration
of disparate networks and systems and managing
them, and, planning again for yet more interfaces
as marketing pressures force vendors to develop new
techniques that routinely change the ground rules.


              Application Development
           And Configuration Management
There are a large number of programming languages
and development tools for writing today's
client/server applications.  Each development
system has its own visual programming interface for
building GUI front ends and its own fourth-
generation language (4GLs) for doing the business
logic.  Programmers are always learning new
languages to meet the next generation.

   Traditional programming has given way to
programming for graphical user interfaces and
object-oriented methods, two technologies with
steep learning curves for the traditional
programmer.

   Programming managers are responsible for
maintaining legacy systems in traditional languages
while developing new ones in newer languages and
tools for the client/server environment.  They must
also find ways to keep track of all the program
modules and ancillary files that make up an
application when several programmers work on a
project.  Stand-alone version control and
configuration management programs handle this, and
parts of these systems are increasingly being built
into the development systems themselves (see
configuration management).


                Database Management
Like all software, a database management system
(DBMS) must support the hardware platform and
operating system it runs in.  In order to move a
DBMS to another platform, a version must be
available for the new hardware and operating
system.  The common database language between
client and server is SQL, but each DBMS vendor
implements its own rendition of SQL, requiring a
special SQL interface to most every DBMS.

   For certain kinds of applications, relational
databases (RDBMSs) are giving way to object-
oriented databases (OODBMSs) or unified databases
that are both relational and object oriented.  This
puts a new slant on learning about data structures
and the way they are processed.

   Database administrators must select the DBMS or
DBMSs that efficiently process the daily
transactions and also provide sufficient horsepower
for decision support.  They must decide when and
how to split the operation into different
databases, one for daily work, the other for ad hoc
queries.  They must also create the structure of
the database by designing the record layouts and
their relationships to each other.


    Operating Systems/Network Operating Systems
Operating systems are the master control programs
that run the computer system.  Single-user
operating systems, such as DOS, Windows and Mac,
are used in the clients, and multiuser network
operating systems, such as NetWare, Windows NT and
all the variations of UNIX, are used in the
servers.

   The operating system sets the standard for the
programs that run under it.  The choice of
operating system combined with the hardware
platform determines which ready-made applications
can be purchased to work on it.

   On the Intel x86 platform, there are more
choices for operating environments than ever
before.  However, just as the PC begins to mature
into manageable bedlam, the PowerPC emerges to
challenge the sacrosanct standard and offer us even
more choices.

   Systems programmers and IS managers must
determine when newer operating systems make sense
and plan how to integrate them into existing
environments.


             Communications Protocols
Communications protocols determine the format and
rules for how the transmitted data is framed and
managed from the sending station to the receiving
station.  IBM's SNA, Digital's DECnet, Apple's
AppleTalk, Novell's IPX/SPX, UNIX's TCP/IP and
Microsoft's NetBEUI are the major ones.  Exchanging
data and messages between Macs, PCs, minis,
mainframes and UNIX workstations means that network
managers increasingly are designing networks for a
multiprotocol environment.


                       LANs
Transmission from station to station within a LAN
is performed by the LAN access method, or data link
protocol, such as Ethernet and Token Ring.  As
traffic expands within an organization, higher
bandwidth is required, causing organizations to
plan for Fast Ethernet, switched Ethernet, FDDI and
CDDI.  At the same time, ATM continues to make
inroads as the be-all-end-all networking topology.

   Repeaters, bridges, routers, gateways, hubs and
swtiches are the devices used to extend, convert,
route and manage traffic in an enterprise network.
Increasingly, one device takes on the job of
another (a router does bridging, a hub does
routing).  Vendor offerings are dizzying.

   Network traffic is becoming as jammed as the Los
Angeles freeways.  Network administrators have to
analyze current network traffic in light of future
business plans and increasing deployment of
multimedia image, sound and video files.  They have
to determine when to increase network bandwidth
while maintaining existing networks, which today
have become the technical lifeblood of an
enterprise.


                       WANs
Transmitting data to remote locations requires the
use of private lines or public switched services
offered by local and long distance carriers.
Connections can be as simple as dialing up via
modem or by leasing private lines, such as T1 and
T3.  Switched 56, frame relay, ISDN, SMDS and ATM
offer a variety of switched services in which you
pay for the digital traffic you use.

   Laptop use has created a tremendous need for
remote access to LANs.  Network administrators have
to design LANs with a combination of remote access
and remote control capability to allow mobile
workers access to their databases and processing
functions.


                Network Management
Network management is the monitoring and control of
LANs and WANs from a central management console.
It requires network management software, such as
IBM's NetView and HP's OpenView.  The Internet's
SNMP has become the de facto standard management
protocol, but there are many network management
programs and options.  For example, there are over
30 third-party add-ons for HP's popular OpenView
software.


                Systems Management
Systems management includes a variety of functions
for managing computers in a networked environment,
including software distribution, version control,
backup & recovery, printer spooling, job
scheduling, virus protection and performance and
capacity planning.  Network management may also
fall under the systems management umbrella.


                  Electronic Mail
Electronic mail requires a store and forward system
so that mail can be safely kept in a "mailbox"
until it is retrieved.  Although messages and
attached files are transmitted using standard
transport protocols, the mail system is a high-
level application with its own messaging protocols.
The major ones are IBM's SNADS, the international
X.400, Novell's MHS, the Internet's SMTP, Lotus'
cc:mail and Microsoft Mail.


                      Formats
Word processors, DBMSs, spreadsheets, drawing and
paint programs generate files in their own
proprietary data format.  For example, there are
more than 75 graphics formats alone.  Moving files
from one application to another requires conversion
(exporting and importing) from one format to
another.  Dealing with multiple formats and
multimedia is why object-oriented databases are
being evaluated.  They can support any kind of
text, picture, sound and video format that exists
today or that comes tomorrow.


                      Summary


                  Happy Computing!





Enterprise Networking Services
See ENS.



entity
In a database, anything about which information can
be stored; for example, a person, concept, physical
object or event.  Typically refers to a record
structure.



entity relationship model
A database model that describes the attributes of
entities and the relationships among them.  An
entity is a file (table).



entity type
In a database, a particular kind of file; for
example, a customer or product file.



entropy
In data compression, a measure of the amount of
non-redundant, non-compressible information in an
object.



entry
The input of an item or set of items at a terminal.
See data entry.



entry point
In programming, the starting point of the
instructions in a subroutine.



enumerate
To count or list one by one.  For example, an
enumerated data type defines a list of all possible
values for a variable, and no other value can then
be placed into it.



envelope
(1) A range of frequencies for a particular
operation.

(2) A group of bits or items that is packaged and
treated as a single unit.



environment
A particular configuration of hardware or software.
"The environment" refers to a hardware platform and
the operating system that is used in it.  A
programming environment would include the compiler
and associated development tools.

   Environment is used in other ways to express a
type of configuration, such as a networking
environment, database environment, transaction
processing environment, batch environment,
interactive environment and so on.  See platform.



environment variable
See DOS Set.



EOF
(End Of File)  The status of a file when its end
has been reached or when an instruction or command
resets the file pointer to the end.



EOL
(End Of Line)



EOM
(End Of Message)



EOT
(End Of Transmission)



EPA
(Edge Path Adapter)  A device that converts packets
from an Ethernet or Token Ring LAN to the cell
structure of an ATM network and vice versa.



epitaxial layer
In chip making, a semiconductor layer that is
created on top of the silicon base rather than
below it.  See molecular beam epitaxy.



epoch date
The starting point from which time is measured as
the number of days, minutes, etc., from that time.



EPP
(1) (Enhanced Parallel Port)  See IEEE 1284.

(2) (Ethernet Packet Processor)  A chip from
Kalpana, Inc., Santa, Clara, CA, that doubles speed
of Ethernet transmission to 20Mbits/sec.



EPROM
(Erasable Programmable ROM)  A programmable and
reusable chip that holds its content until erased
under ultraviolet light.  EPROMS have a lifespan of
a few hundred write cycles.  EPROMS are expected to
eventually give way to flash memory.  See EPROM
programmer.



EPROM programmer
A device that writes instructions and data into
EPROM chips.  Some earlier units were capable of
programming both PROMs and EPROMs.



EPS
See Encapsulated PostScript.



Epson emulation
Compatible with Epson dot matrix printers.  The
command set in the Epson MX, RX and FX printers has
become an industry standard.  Useful codes are:


  ASCII VALUE  COMMAND

          12  Form feed
       27 48  8 LPI
       27 50  6 LPI
          15  Condensed on
          18  Condensed off
     27 81 1  Double width on
     27 81 0  Double width off
       27 69  Emphasized on
       27 70  Emphasized off
     27 83 1  Subscript on
     27 83 0  Superscript on
       27 84  Sub/super off
     27 45 1  Underline on
     27 45 0  Underline off





EPSS
(Electronic Performance Support System)  A computer
system that provides quick assistance and
information without requiring prior training to use
it.  It may incorporate all forms of multimedia
delivery as well as AI techniques such as expert
systems and natural language recognition.



EQ
(EQual to)  See relational operator.



equalization
In communications, techniques used to reduce
distortion and compensate for signal loss
(attenuation) over long distances.



equation
An arithmetic expression that equates one set of
conditions to another; for example, A = B + C.  In
a programming language, assignment statements take
the form of an equation.  The above example would
assign the sum of B and C to the variable A.



ER model
See entity relationship model.



ERA
(Electrically Reconfigurable Array)  A programmable
logic chip (PLD) technology from Plessey
Semiconductor that allows the chip to be
reprogrammed electrically.



erase
See delete.



erase head
In a magnetic tape drive, the device that erases
the tape before a new block of data is recorded.



ergonomics
The science of people-machine relationships.  An
ergonomically-designed product implies that the
device blends smoothly with a person's body or
actions.



Erlang
A unit of traffic use that specifies the total
capacity or average use of a telephone system.  One
Erlang is equivalent to the continuous usage of a
telephone line.  Traffic in Erlangs is the sum of
the holding times of all lines divided by the
period of measurement.



error checking
(1) Testing for accurate transmission of data over
a communications network or internally within the
computer system.  See parity checking and CRC.

(2) Same as validity checking.



error control
Same as error checking.



error detection & correction
See error checking and validity checking.



error-free channel
An interface (wire, cable, etc.) between devices
that is not subject to external interference;
specifically not the dial-up telephone system.



error handling
Routines in a program that respond to errors.  The
measurement of quality in error handling is based
on how the system informs the user of such
conditions and what alternatives it provides for
dealing with them.



error rate
The measurement of the effectiveness of a
communications channel.  It is the ratio of the
number of erroneous units of data to the total
number of units of data transmitted.



ES
See expert system.



ES/3090
A high-end IBM mainframe that incorporates the
ESA/370 enhancements.



ES/9000
The IBM System/390 computer line introduced in late
1990 that uses 31-bit addressing with maximum
memory capacities from 256MB to 9GB.  It's 18
models (Model 120 to Model 960) offered the widest
range of power in a single introduction at one time
with prices ranging from $70K to $23M.  Vector
processing is optional on high-end water-cooled and
certain air-cooled models.  See System/390.



ESA/370
(Enterprise System Architecture/370)  IBM
enhancements that increase the performance of high-
end 4381 and 3090 mainframes.  Introduced in 1988,
it increases virtual memory from 2GB to 16TB and
adds techniques for managing it more effectively.
This architecture is built into System/390 ES/9000
computers.



ESA/390
(Enterprise System Architecture/390)  Extensions to
ESA/370 for the System/390 series.  It includes
MVS/ESA, VM/ESA and VSE/ESA operating systems.



Esc
See escape character and escape key.



escape character
A control character often used to precede other
characters to control a printer or other device.
For example, escape, followed by &l10, sets the
LaserJet to landscape mode.  In ASCII, escape is
decimal 27, hex 1B; in EBCDIC, it is hex 27.



escape key
A keyboard key commonly used to exit a mode or
routine, or cancel some function.



escape sequence
(1) A machine command that starts with an escape
character.  Printers are often commanded by escape
sequences.  See escape character.

(2) In a modem, a unique sequence of characters
that precedes a command.  It allows modem commands
(dial, hang up, etc.) to be transmitted with the
data.  See TIES and Hayes Smartmodem.



ESCON
(Enterprise Systems CONnection)  An IBM System/390
fiber optic channel that transfers 10 Mbytes/sec up
to 5.6 miles.  An ESCON Director is the coupling
device that provides 8-16 ports (Model 1) or 28-60
ports (Model 2).



ESD
(1) (Electronic Software Distribution)
Distributing new software and upgrades via the
network rather than individual installations on
each machine.  See ESL.

(2) (ElectroStatic Discharge)  Sparks (electrons)
that jump from an electrically-charged object to an
approaching conductive object.

(3) (Entry Systems Division)  The IBM division that
conceived and developed the original IBM PC.



ESDI
(Enhanced Small Device Interface)  A hard disk
interface that transfers data in the one to three
MByte/sec range.  ESDI was the high-speed interface
for small computers for a while, but has been
superseded by IDE and SCSI drives.  See hard disk.



ESDL
(Electronic Software Distribution and Licensing)
The combination of ESD and ESL.



ESDS
(Entry Sequence DataSet)  A VSAM structure that
stores records one after the other without regard
to content.  Records are retrieved by address.
Contrast with KSDS.



ESF
(1) (Extended SuperFrame)  An enhanced T1 format
that allows a line to be monitored during normal
operation.  It uses 24 frames grouped together
(instead of the 12-frame D4 superframe) and
provides room for CRC bits and other diagnostic
commands.

(2) (External Source Format)  A specification
language for defining an application in IBM's
CSP/AD application generator.



ESL
(Electronic Software Licensing)  Software that
keeps track of the number of active users per
application in order to comply with the multiuser
licensing contracts that have been purchased.



ESL for Windows
A client/server development system for Windows from
Easel Corporation.  It is a native Windows version
of Easel's Workbench product which is primarily an
OS/2 development system with Windows runtime
support.  ESL for Windows includes ESL QuickStep, a
source code project manager.



ESL Renovator
A screen scraper from Easel Corporation that is
used to turn character-based mainframe and mini
screens into Windows front ends.



ESL Workbench
A client/server development system for OS/2 from
Easel Corporation that also provides Windows
runtime capability.  ESL Workbench is geared for
developing very large applications.  Subsequently,
Easel introduced a native Windows development
system, called ESL for Windows.  Starting with
Version 4.0, ESL Workbench provides international
language capability, which instantly switches menus
and messages to Spanish, German, etc.



ESP
(1) (Enhanced Service Provider)  An organization
that adds value to basic telephone service by
offering such features as call-forwarding, call-
detailing and protocol conversion.

(2) (E-tech Speedy Protocol)  A proprietary
protocol of E-Tech Research used in its modems.

(3) (Electronic Still Photography)  Digitizing and
transmitting images over a telephone line.

(4) (Emulex SCSI Processor)  A proprietary chip
used in Emulex's SCSI disk controller.



ESS
(1) (Electronic Switching System)  A large-scale
computer used to switch telephone conversations in
a central office.

(2) (Executive Support System)  See EIS.

(3) (Electronic SpreadSheet)  See spreadsheet.



ET3000, ET4000
See Tseng Labs.



Ethernet
A local area network (LAN) developed by Xerox,
Digital and Intel.  It is the most widely used LAN
access method (Token Ring is next).  Ethernet
connects up to 1,024 nodes at 10 Mbits per second
over twisted pair, coax and optical fiber.  Faster
Ethernets are emerging: switched Ethernet gives
each user a dedicated 10 Mbps channel; Fast
Ethernet (100BaseT, 100BaseVG) runs at 100 Mbps
shared.

   Ethernet uses the broadcast method.  When a
station is ready to send, it transmits its data
packets onto the network, which is common to all
nodes.  All stations "hear" the data.  The station
that matches the destination address in the packet
is the one that responds, while the others do
nothing.

   Standard Ethernet, or "Thick Ethernet" requires
a thick coax cable, but can run as far as 1,640
feet without using repeaters.  Attachment is made
by clamping a transceiver, which is cabled to the
adapter card, onto the main bus cable.

   Thin Ethernet, also "ThinNet" and "CheaperNet"
uses a thinner, less-expensive coax that is easier
to connect.  It uses T-type BNC connectors, and the
transceivers are built into the adapter cards.

   Twisted pair Ethernet allows the most economical
wiring to be used, often taking advantage of
installed telephone wires.  Fiber Optic Ethernet is
impervious to external radiation.  Both use a star
topology and connect to a central hub.

   Ethernet is a data link protocol and functions
at the data link and physical levels of the OSI
model (1 and 2).  It uses the CSMA/CD access method
and conforms to the IEEE 802.3 standard.  See data
link protocol and OSI model.


                        Maximum devices per segment
            Maximum segment length     
     Ethernet type                      Topology

 10Base5 Standard "Thick"  1,640 ft.  100   bus
 10Base2 Thin, "ThinNet",
            "CheaperNet"     607 ft.   30   bus
 10BaseT Twisted pair        328 ft.    2   star
 10BaseF Fiber Optic         1.2 mi.    2   star





Ethernet adapter
An Ethernet network adapter.  See network adapter.



Ethernet address
A unique number assigned to each Ethernet network
adapter.  It is a 48-bit number maintained by the
IEEE.  Hardware vendors obtain blocks of numbers
that they can build into their cards.



EtherTalk
Macintosh software from Apple that accompanies its
Ethernet Interface NB Card and adapts the Mac to
Ethernet networks.



EtherWave
An Ethernet system from Farallon Computing, Inc.,
Alameda, CA, that provides network adapters that
daisy chain 10BaseT wire from machine to machine.
Regular 10BaseT systems require a central hub that
connects all machines.  To add a station to the
network when a hub is out of ports requires adding
a hub.  EtherWave allows connecting seven daisy-
chained EtherWave PCs to a single hub port.



Eurocard
A family of European-designed printed circuit
boards that uses a 96-pin plug rather than edge
connectors.  The 3U is a 4x6" board with one plug;
the 6U is a 6x12" board with two plugs; the 9U is a
14x18" board with three plugs.



European Computer Manufacturers Association
See ECMA.



even parity
See parity checking.



event driven
An application that responds to input from the user
or other application at unregulated times.  It's
driven by choices that the user makes (select menu,
press button, etc.).  Contrast with procedure
oriented.



EVGA
(Extended VGA)  See VGA.



eWorld
Online service from Apple aimed at the consumer
market.  Introduced in 1994 initially for
Macintoshes, Windows capability is expected in
1995.



Exabyte
(Exabyte Corporation, Boulder, CO)  A maker of
high-capacity, proprietary 8mm tape backup systems.
Single-tape units are in the 2 to 25GB range, and
multi-tape library units can hold terabytes.



examinations
See CCP, NetWare certification and Microsoft
Certified Professional.



Excel
A full-featured spreadsheet for PCs and the
Macintosh from Microsoft.  It can link many
spreadsheets for consolidation and provides a wide
variety of business graphics and charts for
creating presentation materials.



Exception error 12
A DOS error message that means DOS does not have
enough room to handle hardware interrupts.
Increase the number of stacks in the STACKS=
command in the CONFIG.SYS file (see DOS Stacks).



exception report
A listing of abnormal items or items that fall
outside of a specified range.



Exchange Server
An enterprise-wide messaging and mail system from
Microsoft that runs under Windows NT.  It is
expected in late 1994 or early 1995.



exclusive NOR
See NOR.



exclusive OR
See OR.



EXE file
(EXEcutable file)  A runnable program in DOS, OS/2
and VMS.  In DOS, if a program fits within 64K, it
may be a COM file.



executable
A program in machine language that is ready to run
in a particular computer environment.



execute
To follow instructions in a program.  Same as run.



execution time
The time in which a single instruction is executed.
It makes up the last half of the instruction cycle.



executive
Refers to an operating system or only to the
operating system's kernel.



executive information system
See EIS.



exit
(1) To get out of the current mode or quit the
program.

(2) In programming, to get out of the loop, routine
or function that the computer is currently in.



expanded memory
See EMS, EMM and expanded storage.



expanded memory emulator
A memory manager for 386s and up that converts
extended memory into EMS memory.  See EMM.



expanded storage
Auxiliary memory in IBM mainframes.  Data is
usually transferred in 4K chunks from expanded
storage to central storage (main memory).



expansion board
(1) A printed circuit board that plugs into an
expansion slot.  All the boards (cards) that plug
into a personal computer's bus are expansion
boards, such as display adapters, disk controllers
and sound cards.

(2) See bus extender.



expansion bus
(1) The computer's bus comprised of a series of
receptacles or slots into which expansion boards
(video display, disk controller, etc.) are plugged.

(2) Sometimes refers to bus extender (3).



expansion card
Same as expansion board.



expansion slot
A receptacle inside a computer or other electronic
system that accepts printed circuit boards.  The
number of slots determines future expansion.  In
personal computers, expansion slots are connected
to the bus.



ExperLogo
A Macintosh version of Logo from ExperTelligence,
Inc., Goleta, CA.  It contains more functions
similar to LISP than most versions of Logo.



expert system
An AI application that uses a knowledge base of
human expertise for problem solving.  Its success
is based on the quality of the data and rules
obtained from the human expert.  In practice,
expert systems perform both below and above that of
a human.

   It derives its answers by running the knowledge
base through an inference engine, which is software
that interacts with the user and processes the
results from the rules and data in the knowledge
base.

   Examples of uses are medical diagnosis,
equipment repair, investment analysis, financial,
estate and insurance planning, vehicle routing,
contract bidding, production control and training.
See EPSS.


Ŀ     Ŀ     Ŀ
Knowledge     Inference       User   
  Base    Engine  Interface
          
If-then-else   Forward chain   Ability to ask
   rules       Backward chain  questions, get
                               input and explain
                               rationale for answer

                Expert System





expireware
Software with a built-in expiration date, either by
date or number of uses.



explode
(1) To break down an assembly into its component
pieces.  Contrast with implode.

(2) To decompress data back to its original form.



exponent
The number written above the line and to the right
of a number that indicates the power of a number,
or how many zeros there are in it.  For example 10
to the 3rd power indicates three zeros.  The number
467,000 can be stated as 467 x 10 to the 3rd.  On a
screen or printout, the number is expressed as
467E3.  See floating point.



exponential growth
Extremely fast growth.  On a chart, the line curves
up rather than being straight.  Contrast with
linear.



exponential smoothing
A widely-used technique in forecasting trends,
seasonality and level change.  Works well with data
that has a lot of randomness.



export
To convert a data file in the current application
program into the format required by another
application program.



expression
In programming, a statement that describes data and
processing.  For example, VALUE=2*COST and
PRODUCT="HAT" AND COLOR="GRAY".



extended application
A DOS application that runs in extended memory
under the control of a DOS extender.



extended ASCII
The second half of the ASCII character set (128
through 255).  The symbols are defined by ANSI, by
IBM for the PC (see ASCII chart or hex chart) and
by other vendors for proprietary uses.  It is non-
standard ASCII.



Extended Edition
The IBM version of OS/2 that includes
communications and database management.  The
Communications Manager has built-in LU 6.2 and X.25
protocols.  The Database Manager uses IBM's SQL.



extended maintenance
On-call service that is ordered for periods in
addition to the primary period of maintenance.



extended memory
In Intel 286s and up, it is standard memory above
one megabyte.  Extended memory is used directly by
Windows and OS/2 as well as DOS applications that
run with DOS extenders.  It is also used under DOS
for RAM disks and disk caches.  Contrast with
expanded memory (EMS), which is specialized memory
above one megabyte.  Memory boards can usually be
set up as a mix of the two.  See EMS, XMS and DOS
extender.

                
                Extended
                 Memory 
                 1MB and
                   up   
   Ŀ- - -Ĵ- - - - - - -
    8088        286    Conventional
    8086        386       Memory
    (XT)        486     Up to 1MB
              Pentium 
        
                   
   
      Expanded memory (EMS)
   

          CPUs AND MEMORY TYPES





extender
See bus extender.



extensible
Capable of being expanded or customized.  For
example, with extensible programming languages,
programmers can add new control structures,
statements or data types.



extension
(1) A DOS and OS/2 file category.
(2) See Macintosh extension.

(1) Extensions are file types, or file categories,
that are added to the end of DOS and OS/2 file
names.  The extension is separated from the file
name with a dot such as LETTER.DOC.

   An extension can have up to three letters or
digits.  Executable files use .EXE, .COM and .BAT
extensions; for example, GLOSS.EXE is the software
program for the DOS version of this database.

   All programs and most data files use extensions.
However, some word processing files do not, in
which case you could create your own filing system;
for example, CHAP1.NOV and CHAP2.NOV could be
chapters in a novel.  See graphics formats.


  File extension
         Type of file

906  Calcomp plotter

ABC  Glossary configuration
AD   After Dark image
AFM  Type 1 font metrics
AG4  Access G4 document imaging
AI   Adobe Illustrator graphics,
     Encapsulated PostScript header
ARC  ARC, ARC+ compressed

ASC  ASCII file
ASM  Assembly source code
ATT  AT&T Group IV fax
AVI  Microsoft movie format

BAK  Backup
BAS  BASIC source code
BAT  DOS, OS/2 batch file
BIN  Driver, overlay
BMP  Windows & OS/2 bitmap

C    C source code
CAL  Windows calendar,
     SuperCalc spreadsheet,
     CALS raster and vector formats
CAP  Ventura Pub. captions
CAL  CALS raster and vector formats
CDR  Corel Draw vector graphics

CFG  Configuration
CGM  CGM vector graphics
CHP  Ventura Pub. chapter
CHK  DOS Chkdsk chained file
CIF  Ventura Pub. chapter info.

CIT  Intergraph scanned image
COB  COBOL source code
CLP  Windows clipboard
COM  Executable program
CPI  DOS code page

CPP  C++ source code
CPR  Knowledge Access raster graphics
CSV  Comma delimited
CUT  Dr. Halo raster graphics

DAT  Data
DB   Paradox table
DBF  dBASE database
DBT  dBASE text
DBX  DATABEAM raster graphics

DCA  IBM text
DCT  Dictionary
DG   Autotrol vector graphics
DGN  Intergraph vector graphics
DIB  Windows DIB raster graphics

DIC  Dictionary
DIF  Spreadsheet
DLL  Dynamic link library
DOC  Document (Multimate, Word...)
DOX  MultiMate V4.0 document

DPI  Pointline raster graphics
DRV  Driver
DRW  Designer vector graphics (2.x, 3.x)
DS4  Designer vector graphics (4.x)
DWG & DXF  AutoCAD vector formats
DX   Autotrol document imaging

ED5  EDMICS raster graphics (DOD)
EPS  Encapsulated PostScript
ESI  Esri plot file (vector)
EXE  Executable program

FAX  Various fax formats
FDX  Force index
FLC, FLI  AutoDesk animation
FLD  Hijaak thumbnail folder
FMT  dBASE Screen format
FNT  Windows font

FON  Font or telephone no.
FOR  FORTRAN source code
FOT  Windows TrueType font info.
FOX  FoxBase compiled program
FM3  Format info for 1-2-3 Version 3
FRM  dBASE report layout

G4   GTX RasterCAD (raster into vector)
GCA  IBM MO:DCA - GOCA vector graphics
GED  Arts & Letters graphics
GEM  GEM vector graphics
GIF  CompuServe raster graphics

GP4  CALS Group IV - ITU-TSS Group IV
GRF  Micrografx Charisma vector graphics
GRP  Windows ProgMan Group
GX1 & GX2  Show Partner raster graphics

HLP  Help text
HPL  HP Graphics language
HYC  WordPerfect hypen list

ICA  IBM MO:DCA - IOCA raster graphics
ICO  Windows icon
IDE  Development environment configuration
IDX  FoxBase index
IFF  Amiga

IGF  Inset Systems (Hijaak)
       raster & vector graphics
IL   Icon library (hDC Computer)
IMG  GEM Paint raster graphics
INF  Information
INI  Initialization

JPG  JPEG (JFIF) raster graphics
JT   JT Fax

KFX  Kofax Group IV fax

LBL  dBASE label
LBM  Deluxe Paint graphics
LIB  Function library
LZH  LHARC compressed

MAC  MacPaint raster graphics
MAP  Linkage editor map
MCS  MathCAD format
MDB  Access database
MET  OS/2 Metafile

MEU  Menu items
MDX  dBASE IV multi-index
MID  MIDI sound file
MIL  Same as GP4
MMM  Macromind animation format

MOV  QuickTime for Windows movie
MRK  Informative Graphics markup file
MSG  Message file
MSP  Microsoft Paint raster graphics

NDX  dBASE index
NG   Norton Guides text
NLM  NetWare NLM program

OAZ  OAZ Fax
OBJ  Object module
OVL  Overlay module
OVR  Overlay module
OZM  Sharp Organizer memo bank
OZP  Sharp Organizer telephone bank

PAS  Pascal source code
PCL  HP LaserJet series
PCD  Photo CD raster graphics
PCM  LaserJet cartridge info.
PCT  PC Paint raster graphics,
     Macintosh PICT raster & vector graphics

PCW  PC Write document
PCX  PC Paintbrush raster graphics
PDF  Portable Document Format (Acrobat)
     Printer driver
PDV  PC Paintbrush printer driver
PFA  Type 1 font (ASCII)

PFB  Type 1 font (encrypted)
PFM  Windows Type 1 font metrics
PGL  HPGL 7475A plotter (vector graphics)
PIC  Various vector formats:
     Lotus 1-2-3,
     Micrografx Draw,
     Mac PICT format,
     IBM Storyboard raster graphics
PIF  Windows info. for DOS programs,
     IBM Picture Interchange

PIX  Inset Systems raster & vector graphics
PM   PageMaker graphics/text
PMx  PageMaker document (x=ver.)
PTx  PageMaker template (x=ver.)
PRD  Microsoft Word printer driver

PRG  dBASE source code
PRN  XyWrite printer driver
PRN  Temporary print file
PRS  WordPerfect printer driver
PRT  Formatted text

PS   PostScript page description
P10  Tektronix Plot10 plotter (vector graphics)

QLC  ATM font info.

RAS  Sun raster graphics
RIA  Alpharel Group IV raster graphics
RIB  Renderman graphics
RIC  Roch FaxNet
RIX  RIX virtual screen
RLC  CAD Overlay ESP (Image Systems)

RLE  Compressed (run length encoded)
RND  AutoShade format
RNL  GTX Runlength raster graphics
RTF  Microsoft text/graphics
R8P  LaserJet portrait font
R8L  LaserJet landscape font

SAM  Ami Pro document
SBP  IBM Storyboard graphics/Superbase text
SC   Paradox source code
SCx  ColoRIX raster (x=res.)
SCM  ScreenCam movie
SCR  dBASE screen layout

SCR  Script
SCR  Windows screen saver
SCT  Lotus Manuscript screen capture text
SET  Setup parameters
SFP  LaserJet portrait font
SFL  LaserJet landscape font

SFS  PCL 5 scalable font
SLD  AutoCAD slide
SND  Aristosoft sound
SPD  Speedo scalable font
STY  Ventura Pub. style sheet
SYL  SYLK format (spreadsheets)
SYS  DOS, OS/2 driver

TAL  Adobe Type Align shaped text
TDF  Speedo typeface definition
TFM  Intellifont font metrics
TGA  TARGA raster graphics
TIF  TIFF raster graphics

TMP  Temporary
TTC  TrueType font compressed
TTF  TrueType font
TXT  ASCII text

USP  LaserJet portrait font
USL  LaserJet landscape font

VGR  Ventura Pub. chapter info.
VOC  Sound Blaster sound
VUE  dBASE relational view

WAV  Windows sound
WKQ  Quattro spreadsheet
WKS  Lotus 1-2-3 ver. 1a spreadsheet
WK1  Lotus ver. 2.x
WK3  Lotus ver. 3.x & Windows
WK4  Lotus ver. 4.x

WMF  Windows Metafile
WPG  WordPerfect raster & vector graphics
WPM  WordPerfect macro
WPS  Microsoft Works document
WRI  Windows Write document
WRK  Sympohony spreadsheet

XFX  JetFax
XLC  Excel chart
XLS  Excel spreadsheet

ZIP  PKZIP compressed
ZOO  Zoo compressed

$$$  Temporary





extent
Contiguous space on a disk reserved for a file or
application.



external command
(1) In DOS and OS/2, a function performed by a
separate utility program that accompanies the
operating system.  Contrast with internal command.
See DOS external command.

(2) A user-developed HyperCard command.  See XCMD.



external function
A subroutine that is created separately from the
main program.  See XFCN.



external interrupt
An interrupt caused by an external source such as
the computer operator, external sensor or
monitoring device, or another computer.



external modem
A self-contained modem that is connected via cable
to the serial port of a computer.  It draws power
from a wall outlet.  The advantage of an external
modem is that a series of status lights on the
outside of the case display the changing states of
the modem (off-hook, carrier detect, transmitting,
etc.).  In varying degrees, the communications
program informs the user as well.  However, having
the status indicators directly visible on the unit
may be more helpful if a problem occurs.  Contrast
with internal modem.



external reference
In programming, a call to a program or function
that resides in a separate, independent library.



external sort
A sort program that uses disk or tape as temporary
workspace.  Contrast with internal sort.



external storage
Storage outside of the CPU, such as disk and tape.



EXTRA!
Terminal emulation software from Attachmate
Corporation, Bellevue, WA.  It is used with 3270
and 5250 emulators to gain access to a mainframe or
mini from a personal computer.  Versions for
Windows and Mac are available.



extremely low frequency
See low radiation.



f
See farad and femto.



F connector
A coaxial cable connector used to connect antennas,
TVs and VCRs.  It is easily recognized: the plug's
inner wire is stripped bare and sticks out of the
connector looking very unfinished.



F keys
See function keys.



F1 key
Function key number one.  There are 12 function
keys on a PC keyboard.  F1 is used for retrieving
help in Windows and in most DOS applications.



FaceLift
A font scaler for Windows and WordPerfect from
Bitstream Inc., Cambridge, MA, that provides on-
the-fly font scaling for Bitstream's own Speedo
fonts.  FaceLift for Windows also supports Type 1
fonts.  FaceLift for WordPerfect lets users create
a wide variety of custom fonts, including outlines,
shadows and fill scaling, for the DOS version of
WordPerfect.



facilities management
The management of a user's computer installation by
an outside organization.  All operations including
systems, programming and the datacenter can be
performed by the facilities management organization
on the user's premises.



facsimile
See fax.



factorial
The number of sequences that can exist with a set
of items, derived by multiplying the number of
items by the next lowest number until 1 is reached.
For example, three items have six sequences
(3x2x1=6): 123, 132, 231, 213, 312 and 321.



fail safe
Same as fault tolerant.



fail soft
The ability to fail with minimum destruction.  For
example, a disk drive can be built to automatically
park the heads when power fails.  Although it
doesn't correct the problem, it minimizes
destruction.



FAMOS
(Floating gate Avalanche-injection Metal Oxide
Semiconductor)  A type of EPROM.



fan
A device that uses motor-driven blades to circulate
the air in a computer or other electronic system.
Today's CPUs run extremely hot, and large computer
cabinets use two and three fans to reduce
temperature.  See FanCard.



fan-fold paper
Same as continous forms.



fan in
To direct multiple signals into one receiver.



fan out
To direct one signal into multiple receivers.  See
port multiplier.



FanCard
An expansion card for PCs and Macs from T. S.
Microtech, Inc, Torrance, CA, that contains twin,
counter rotating fans to reduce heat in a fully-
loaded computer.



FAQ file
(Frequently Asked Questions file)  A documentation
file that contains the most commonly asked
questions about a subject.  FAQ files are widely
used on the Internet.



far pointer
In an Intel x86 segmented address, a memory address
that includes both segment and offset.  Contrast
with near pointer.



farad
A unit of electrical charge that is used to measure
the storage capacity of a capacitor.  In
microelectronics, measurements are usually in
microfarads or picofarads.



Fast
An asynchronous communications protocol used to
quickly transmit files over high-quality lines.
Error checking is done after the entire file has
been transmitted.



Fast Ethernet
High-speed Ethernet at 100 Mbps (regular Ethernet
is 10 Mbps).  There are two competing technologies
emerging from the IEEE.  The first method is the
IEEE 802.3 100BaseT, which uses the CSMA/CD access
method with some modification.

   The second method is the IEEE 802.12 100BaseVG,
adapted from HP's 100VG-AnyLAN.  100BaseVG uses a
demand-priority access method instead of CSMA/CD,
which allows priorities to be given.  For example,
realtime voice and video could be given higher
priority than other types of data.

   Like regular Ethernet, Fast Ethernet is a shared
media LAN.  All nodes share the 100 Mbps bandwidth.
Standards are expected to be ironed out in late
1994 or early 1995.



Fast Fourier Transform
See FFT.



FastCAD
A full-featured PC CAD program from Evolution
Computing, Tempe, AZ, known for its well-designed
user interface.  It requires a math coprocessor.
Users with less sophisticated requirements can
start out with FastCAD's baby brother, EasyCAD.



FastDisk
A Windows 3.1 driver in 386 Enhanced Mode that
speeds up disk accesses by running in 32-bit mode,
bypassing DOS and the BIOS and communicating
directly with the disk controller.  It works on
Western Digital and compatible controllers or on
other controllers with upgraded drivers from the
manufacturer.  To turn this feature on and off,
select 386 Enhanced in Control Panel, then click
Virtual Memory, Change, Use 32-Bit Disk Access.
See WinDisk.



FAT
See DOS FAT and VFAT.



fat binary
A Macintosh executable program that contains
machine language in one file for both the Macintosh
and PowerMac machines (680x0 and PowerPC CPUs).
Software distributed in this format will run native
on whichever Mac architecture it is loaded on.



fat client
In a client/server environment, it refers to the
client performing most or all of the application
processing with little or none performed in the
server.  Contrast with fat server.  See two-tier
client/server.



fat server
In a client/server environment, it refers to the
server performing most or all of the application
processing with little or none performed in the
client.  Contrast with fat client.  See two-tier
client/server.



fatal error
A condition that halts processing due to read
errors, program bugs or anomalies.



FatBits
A MacPaint option in the "Goodies" menu that lets a
user edit an image a pixel at a time.



father file
See grandfather, father, son.



fault resilient
See high availability.



fault tolerant
The ability to continue non stop when a hardware
failure occurs.  A fault tolerant system is
designed from the ground up for reliability by
building multiples of all critical components, such
as CPUs, memories, disks and power supplies into
the same computer.  In the event one component
fails, another takes over without skipping a beat.

   Many systems are designed to recover from a
failure by detecting the failed component and
switching to another computer system.  These
systems, although sometimes called fault tolerant,
are more widely known as high availability systems,
requiring that the software resubmits the when the
second system is available.

   True fault tolerant systems are the most costly,
because redundant hardware is wasted if there is no
failure in the system.  On the other hand, fault
tolerant systems provide the same processing
capacity after a failure as before, whereas high
availability systems often provide reduced
capacity.

   Tandem and Stratus are the two major
manufacturers of fault-tolerant computer systems
for the transaction processing (OLTP) market.
Stratus computers are used by long distance
carriers for 800 routing and other out-of-band
services.



fax
(FACSimile)  Originally called telecopying, it is
the communication of a printed page between remote
locations.  Fax machines scan a paper form and
transmit a coded image over the telephone system.
The receiving machine prints a facsimile of the
original.  A fax machine is made up of a scanner,
printer and modem with fax signalling.

   Groups 1 and 2, used in the 1970s and 1980s,
transmit at six and three minutes per page
respectively.  Group 3 transmits up to 9,600 baud
using data compression at less than one minute per
page.  This speed increase led to the extraordinary
rise in usage in the late 1980s, resulting in
today's most universal form of electronic mail.

  Group 3 resolution is 203x98 dpi in standard mode
and 203x196 dpi in fine mode.  Higher-speed Group 4
machines rely on all-digital (ISDN) networks which
may not be prevalent until the mid 1990s.



fax board
Fax transmission on an expansion board.  It uses
software that generates fax signals directly from
disk files or the screen and transmits a sharper
image than a fax machine, which gets its image by
scanning.  Incoming faxes are printed on the
computer's printer.



fax/modem
A combination fax board and data modem available as
an external unit or expansion board.  It includes a
fax switch that routes the call to the fax or the
data modem.



fax switch
A device that tests a phone line for a fax signal
and routes the call to the fax machine.  When a fax
machine dials a number and the line answers, it
emits an 1,100Hz tone to identify itself.  Some
devices handle voice, fax and data modem switching
and may require keying in an extension number to
switch to the modem.



FCB
See DOS FCB.



FCC
(Federal Communications Commission)  The regulatory
body for U.S. interstate telecommunications
services as well as international service
originating in the U.S.  It was created under the
U.S. Communications Act of 1934, and its board of
commissioners is appointed by the President.



FCC Class
An FCC certification of radiation limits on digital
devices.  Class A certification is for business
use.  Class B, for residential use, is more
stringent in order to avoid interference with TV
and other home reception.  See Part 15, Subpart B,
of the Federal Register (CFR 47, Parts 0-19).



FCFS
First come, first served.



fci
(Flux Changes per Inch) The measurement of polarity
reversals on a magnetic surface.  In MFM, each flux
change is equal to one bit.  In RLL, a flux change
generates more than one bit.



FD
(Floppy Disk)  For example, FD/HD refers to a
floppy disk/hard disk device.



FD:OCA
(Formatted Data:Object Content Architecture)  An
SAA-compliant (CCS) specification for formatting
data in fields.



FDDI
(Fiber Distributed Data Interface)   An ANSI
standard token passing network that uses optical
fiber cabling and transmits at 100 Mbits/sec up to
two kilometers.  FDDI is used for MANs and LANs and
includes its own network management standard called
STM (Station Management).  The TP-PMD (CDDI)
version will run over copper (UTP), although
limited to distances of typically 50 to 100 meters.

   FDDI provides network services at the same level
as Ethernet and Token Ring (OSI layers 1 and 2).

   FDDI provides an optional "dual counter-rotating
ring" topology that contains primary and secondary
rings with data flowing in opposite directions.  If
the line breaks, the secondary ring is used to
bypass the fault.


    P     P
    S     S
                                 
                                 
                                 
             
             

    Normal Operation         Rerouted


   Stations can be configured as Single Attached
Stations (SAS) connected to concentrators, or as
Dual Attached Stations (DAS), connected to both
rings.  Groups of stations are typically wired to
concentrators connected in a hierarchical tree to
the main ring.  Large networks may be configured as
a "dual ring of trees," in which the dual ring
provides the backbone to which multiple hierarchies
of concentrators are attached.

   FDDI provides a quantum jump in speed over 10
Mbps Ethernet and 16Mpbs Token Ring and allows
high-resolution images to be quickly transmitted.
See TP-PMD and CDDI.

   For a complimentary copy of a 456-page book on
FDDI called "The Fiber Optic LAN HANDBOOK," contact
Codenoll Corporation, 1086 N. Broadway, Yonkers, NY
10701, 914/965-6300.



FDISK
See DOS Fdisk.



FDM
(Frequency Division Multiplexing)  A method used to
transmit multiple signals over a single channel.
Each signal (data, voice, etc.) modulates a carrier
with a different frequency and all signals travel
simultaneously over the channel.  Contrast with
TDM.  See baseband.



FDMA
(Frequency Division Multiple Access)  The
technology used in the analog cellular telephone
network that divides the spectrum into 30KHz
channels.  See TDMA, CDMA and CDPD.



FDSE
(Full-Duplex Switched Ethernet)  A type of switched
Ethenet that uses full-duplexed network adapters
and provides a 20 Mbps bi-directional transmission
between nodes.  It is expected that by 1995, most
network adapters will have built-in full duplex
capability and can be used in a switched
environment.

   FDSE improves network throughput from server to
server as well as in video conferencing, both of
which benefit from full-duplexed, bi-directional
transmission.



FDX
See full-duplex.



FEA
(Finite Element Analysis)  A mathematical technique
for analyzing stress, which breaks down a physical
structure into substructures, called finite
elements.  The finite elements and their
interrelationships are converted into equation form
and solved mathematically.

   Graphics-based FEA software can display the
model on screen as it is being built and, after
analysis, display the object's reactions under load
conditions.  Models created in popular CAD packages
can often be accepted by FEA software.



feasibility study
The analysis of a problem to determine if it can be
solved effectively.  The operational (will it
work?), economical (costs and benefits) and
technical (can it be built?) aspects are part of
the study.  Results of the study determine whether
the solution should be implemented.



feature connector
See VGA feature connector.



feature negotiation
See automatic feature negotiation.



FEC
See forward error correction.



Federal Communications Commission
See FCC.



federal regulations
See NCSC and Computer Security Act.



female connector
A receptacle into which the male counterpart of the
connector is plugged.



femto
One quadrillionth or 10 to the -15th power.



femtosecond
One quadrillionth of a second.  See space/time.



FEP
See front end processor.



ferric oxide
(Fe2O3)  An oxidation of iron used in the coating
of magnetic disks and tapes.



ferromagnetic
The capability of a material, such as iron and
nickel, to be highly magnetized.  See FRAM.



ferromagnetic RAM
See FRAM.



FET
(Field Effect Transistor)  A type of transistor
used in MOS integrated circuits.



fetch
To locate the next instruction in memory for
execution by the CPU.



FF
See form feed.



FFT
(Fast Fourier Transform)  A class of algorithms
used in digital signal processing that break down
complex signals into elementary components.



fiber bundle
A set of adjacent optical fibers running in
parallel and adhered together.  It is used for
transmitting light to brighten an area as well as
transmitting whole images, but is not used for
modern digital communications.



Fiber Channel
A type of transmission path used as an internal
computer channel as well as a network medium.  It
works with existing interfaces, such as IPI, SCSI
and HiPPI.  In a LAN, it can be used as a high-
speed backbone.   Speeds range up to 100 MBytes/sec
using optical fiber.



Fiber Distributed Data Interface
See FDDI.



fiber loss
The amount of attenuation of signal in an optical
fiber transmission.



fiber optic
Communications systems that use optical fibers for
transmission.  Fiber-optic transmission became
widely used in the 1980s when the long-distance
carriers created nationwide systems for carrying
voice conversations digitally over optical fibers.

   Eventually, all transmission systems may become
fiber optic-based.  Also, in time, the internals of
computers may be partially or even fully made of
light circuits rather than electrical circuits.
See FDDI, Fiber Channel and optical fiber.



Fibonacci numbers
A series of whole numbers in which each number is
the sum of the two preceding ones: 1, 1, 2, 3, 5,
8, 13, etc.  It is used to speed up binary searches
by dividing the search into the two lower numbers;
for example, 13 items would be divided into 5 and 8
items; 8 items would be divided into 5 and 3.



fiche
Same as microfiche.



fiddy
See FDDI.



FidoNet
An E-mail protocol that originated from the Fido
BBS created by Tom Jennings in 1984.  Over 10,000
FidoNet nodes are in use.  Users must have their
networks active for one universal hour in the early
morning, and the software must adhere to the FTSC-
001 specification.  The FidoNet address format is
zone:local net/node; for example, Boardwatch
Magazine's address is 1:104/555.



field
A physical unit of data that is one or more bytes
in size.  A collection of fields make up a record.
A field also defines a unit of data on a source
document, screen or report.  Examples of fields are
NAME, ADDRESS, QUANTITY and AMOUNT DUE.

   The field is the common denominator between the
user and the computer.  When you interactively
query and update your database, you reference your
data by field name.

   There are several terms that refer to the same
unit of storage as a field.  A data element is the
logical definition of the field, and a data item is
the actual data stored in the field.  For each data
element, there are many fields in the database that
hold the data items.

   In the following example, for the DATA ELEMENTS
"product description" and "product no.", there are
FIELDS in the database that hold the DATA ITEMS
"manilla folder, pencil, rubber band, etc."


         DATA ELEMENTS
         Product description    Product no.
     
                FIELD            FIELD  
     
         DATA ITEMS  manilla folder
                     pencil
                     rubber band
                     copy paper
                     paper clip
                     envelope





field effect transistor
See FET.



field engineer
A person who is responsible for hardware
installation, maintentance and repair.  Formal
training is in electronics, although many people
have learned on the job.



field name
An assigned name for a field (NAME, ADDRESS, CITY,
STATE, etc.) that will be the same in every record.



field separator
A character used to mark the separation of fields
in a record.  See comma delimited and tab
delimited.



field service
See field engineer.



field squeeze
In a mail merge, a function that eliminates extra
blank spaces between words when fixed-length fields
are inserted into the document text.  See line
squeeze.



field template
See picture.



FIF
(Fractal Image Format)  A graphics file format from
Iterated Systems, Inc., Norcross, GA, that stores
fractal images with compression ratios as high as
2,500:1.



FIFO
(First In-First Out)  A storage method that
retrieves the item stored for the longest time.
Contrast with LIFO.



fifth-generation computer
A computer designed for AI applications.  Appearing
in the late 1990s, these systems will represent the
next technology leap.



file
A collection of bytes stored as an individual
entity.   All data on disk is stored as a file with
an assigned file name that is unique within the
directory it resides in.

   To the computer, a file is nothing more than a
series of bytes.  The structure of a file is known
to the software that manipulates it.  For example,
database files are made up of a series of records.
Word processing files, also called documents,
contain a continuous flow of text.

   Following are the major types of files stored in
a computer system.  Except for ASCII text files,
all files contain proprietary information contained
in a header or interspersed throughout the file.

        Type               Contents
     data file         data records
     document          text
     spreadsheet       rows and columns of cells
     image             rows and columns of bits
     drawing           list of vectors
     audio             digitized sound waves
     MIDI              MIDI instructions
     video             digital video frames
     batch file        text
     source program    text
     object program    machine language





file and record locking
A first-come, first-served technique for managing
data in a multiuser environment.  The first user to
access the file or record prevents, or locks out,
other users from accessing it.  After the file or
record is updated, it is unlocked and available.



file attribute
A file access classification that allows a file to
be retrieved or erased.  Typical attributes are
read/write, read only, archive and hidden.



file compression
See data compression.



file conversion
See conversion.



file extension
See extension.



file extent
See extent.



file find
A utility that searches all directories for
matching file names.  See how to find a file.



file format
The structure of a file.  There are hundreds of
proprietary formats for database, word processing
and graphics files.  See record layout.



file grooming
Cleaning up the files on a computer system.  It
includes deleting temporary and backup files as
well as defragmenting the disk.



file handle
A temporary reference assigned by the operating
system to a file that has been opened.  The handle
is used to access the file throughout the session.



file layout
Same as record layout.



file maintenance
(1) The periodic updating of master files.  For
example, adding/deleting employees and customers,
making address changes and changing product prices.
It does not refer to daily transaction processing
and batch processing (order processing, billing,
etc.).

(2) The periodic reorganization of the disk drives.
Data that is continuously updated becomes
physically fragmented over the disk space and
requires regrouping.  An optimizing program is run
(daily, weekly, etc.) that rewrites all files
contiguously.



file manager
(1) Software that manages data files.  Often
erroneously called database managers, file managers
provide the ability to create, enter, change, query
and produce reports on one file at a time.  They
have no relational capabilty and usually don't
include a programming language.

(2) Software used to manage files on a disk.  It
provides functions to delete, copy, move, rename
and view files as well as create and manage
directories.  The file manager in Windows is aptly
named "File Manager."



file name
A name assigned by the user or programmer that is
used to identify a file.



file net
See FileNet.



File Not Found
A DOS error message that means DOS cannot locate
the file you have specified.  Use the Dir command
to check its spelling.  It may be also be in
another directory.



file protect ring
A plastic ring inserted into a reel of magnetic
tape for file protection.



file protection
Preventing accidental erasing of data.  Physical
file protection is provided on the storage medium
by turning a switch, moving a lever or covering a
notch.  On 1/2" tape, a plastic ring in the center
of the reel is removed (no ring-no write).  In
these cases, writing is prohibited even if the
software directs the computer to do so.

   Logical file protection is provided by the
operating system, which can designate a single file
as read only.  This method allows both regular
(read/write) and read only files to be stored on
the same disk volume.  Files can also be designated
as hidden files, which makes them invisible to most
software programs.


              Protecting Floppies

   In order to prevent a floppy disk from being
erased or written over by the program or user when
it's in the machine, do the following:

                3.5" Diskettes
Looking at the back of the disk with the metal
circle in the middle and the metal door at the top,
slide the square, plastic window (bottom right)
downward uncovering a hole through the disk.

               5.25" Diskettes
Cover the small, square side notch with a label.
If you don't have the reflective, self-adhesive
label that came with the disk, use any Avery or
similar type of stick-on label.

           It's Just the Opposite
The method is exactly the opposite for both disks:
uncover the 3.5", cover the 5.25".  Why make it
simple?  And people say we don't have our act
together!





file recovery program
Software that recovers disk files that have been
accidentally deleted or damaged.



file server
A high-speed computer in a LAN that stores the
programs and data files shared by users on the
network.  Also called a network server, it acts
like a remote disk drive.  See database server.



file sharing protocol
A communications protocol that provides a structure
for file requests (open, read, write, close, etc.)
between stations in a network.  If file sharing is
strictly between workstation and server, it is also
called a client/server protocol.  It refers to
layer 7 of the OSI model.



file size
The length of a file in bytes.  See "Byte
Specifications" in the term byte.



file spec
(file SPECification)  A reference to the location
of a file on a disk, which includes disk drive,
directory name and file name.  For example, in DOS
and OS/2, c:\wordstar\books\chapter is a file spec
for the file CHAPTER in the BOOKS subdirectory in
the WORDSTAR directory on drive C.



file system
(1) A method for cataloging files in a computer
system.  See hierarchical file system.

(2) A data processing application that manages
individual files.  Files are related by customized
programming.  Contrast with relational database.



file transfer program
A program that transmits files from one computer to
another.  Such programs; for example, Travelling
Software's LapLink and the Interlink utility that
comes with DOS 6, allow the user to control both
computers from one machine.  See FTP.



file transfer protocol
A communications protocol used to transmit files
without loss of data.  A file transfer protocol can
handle all types of files including binary files
and ASCII text files.  Common examples are Xmodem,
Ymodem, Zmodem and Kermit.



file viewer
Software that displays the contents of a file as it
would be normally displayed by the application that
created it.  A single file viewer program is
generally capable of displaying a wide variety of
document, database and spreadsheet formats.
Examples of file viewers for Windows are Symantec's
Norton File Viewer, Phoenix Technologies' Eclipse
Find and Systems Compatibility's Outside In.  See
document exchange software.



FileMaker II
A Macintosh file manager from Claris.  It is a
popular program for general data management and
provides a variety of statistical functions, fast
search capabilities and extensive reporting
features.



FileMan
(1) Public-domain MUMPS software that provides a
stand-alone, interactive DBMS as well as a set of
utilities for the MUMPS programmer.

(2) Slang for Windows' file manager, which is
precisely named "File Manager."



FileNet
A document imaging system from FileNet Corporation,
Costa Mesa, CA.  Introduced in 1985, FileNet is the
most widely-used, high-end workflow automation
system.  It runs on PCs, Sun and Digital
workstations and also offers an RS/6000 document
server running UNIX and Oracle.



filespec
See file spec.



fill
(1) In a paint program, to change the color of a
bordered area.

(2) In a spreadsheet, to enter common or repetitive
values into a group of cells.



fill pattern
(1) A color, shade or pattern used to fill an area
of an image.

(2) Signals transmitted by a LAN station when not
receiving or transmitting data in order to maintain
synchronization.



fill scaling
The ability to change a fill pattern from light to
dense.  For example, if polka dots were used, the
fill pattern could range from thick dots widely
separated to very thin dots tightly packed
together.



film recorder
A device that takes a 35mm slide picture from a
graphics file, which has been created in a CAD,
paint or business graphics package.  It generates
very high resolution, generally from 2,000 to 4,000
lines.

   It typically works by recreating the image on a
built-in CRT that shines through a color wheel onto
the film in a standard 35mm camera.  Some units
provide optional Polaroid camera backs for instant
previewing.  Film recorders can be connected to
personal computers by plugging in a controller
board cabled to the recorder.



filter
(1) A process that changes data, such as a sort
routine that changes the sequence of items or a
conversion routine (import or export filter) that
changes one data, text or graphics format into
another.  See also image filter.

(2) A pattern or mask through which only selected
data is passed.  For example, certain e-mail
systems can be programmed to filter out important
messages and alert the user.  In dBASE, set filter
to file overdue, compares all data to the matching
conditions stored in OVERDUE.



financial planning language
A language used to create data models and command a
financial planning system.



financial planning system
Software that helps the user evaluate alternatives.
It allows for the creation of a data model, which
is a series of data elements in equation form; for
example, gross profit = gross sales - cost of goods
sold.  Different values can be plugged into the
elements, and the impact of various options can be
assessed (what if?).

   A financial planning system is a step above a
spreadsheet by providing additional analysis tools;
however, increasingly, these capabilities are being
built into spreadsheets.  For example, sensitivity
analysis assigns a range of values to a data
element, which causes that data to be highlighted
if it ever exceeds that range.

   Goal seeking provides automatic calculation.
For example, by entering gross margin = 50% as well
as the minimums and maximums of the various inputs,
the program will calculate an optimum mix of inputs
to achieve the goal (output).



find file
See file find and how to find a file.



Finder
The part of early Macintosh operating systems that
keeps track of icons, controls the Clipboard and
Scrapbook and allows files to be copied.  Finder
manages one application at a time.  MultiFinder,
the successor to Finder, manages multiple
applications and is now an inherent part of the Mac
operating system.



finger
An UNIX command widely used on the Internet to find
out if a particular user is currently logged on.
Some systems provide additional information such as
voice number and the last time the user logged on.
The person being "fingered" must have placed his or
her profile on the system.



fingerprint reader
A scanner used to identify a person's fingerprint
for security purposes.  After a sample is taken,
access to a computer or other system is granted if
the fingerprint matches the stored sample.  A PIN
may also be used with the fingerprint sample.



finite element
See FEA.



firewall
A network node set up as a boundary to prevent
traffic from one segment to cross over into
another.  See router and bridge.



FireWire
A serial bus developed by Apple and Texas
Instruments that allows for the connection of 63
devices at speeds ranging from 100 to 400
Mbits/sec.  Up to 1022 FireWire buses can be
bridged together providing enormous capacity.  It
is envisioned as a replacement for serial, parallel
and SCSI ports.



firmware
A category of memory chips that hold their content
without electrical power and include ROM, PROM,
EPROM and EEPROM technologies.  Firmware becomes
"hard software" when holding program code.



first-generation computer
A computer that used vacuum tubes as switching
elements; for example, the UNIVAC I.



fixed disk
A non-removable hard disk such as is found in most
personal computers.  Programs and data are copied
to and from the fixed disk.



fixed-frequency monitor
A monitor that accepts one type of video signal,
such as VGA only.  Contrast with multiscan monitor.



fixed head disk
A direct access storage device, such as a disk or
drum, that has a read/write head for each track.
Since there is no access arm movement, access times
are significantly improved.



fixed length field
A constant field size; for example, a 25-byte name
field takes up 25 bytes in each record.  It is
easier to program, but wastes disk space and
restricts file design.  Description and comment
fields are always a dilemma.  Short fields allow
only abbreviated remarks, while long fields waste
space if lengthy comments are not required in every
record.  Contrast with variable length field.



fixed length record
A data record that contains fixed length fields.



fixed point
A method for storing and calculating numbers in
which the decimal point is always in the same
location.  Contrast with floating point.



FK
See foreign key.



Fkey
(Function key)  A Macintosh command sequence using
command, shift and option key combinations.  For
example, Fkey 1 (command-shift 1) ejects the
internal floppy.



flag
(1) In communications, a code in the transmitted
message which indicates that the following
characters are a control code and not data.

(2) In programming, a "yes/no" indicator built into
certain hardware or created and controlled by the
programmer.

(3) A UNIX command line argument.  The symbol is a
dash.  For example, in the command head -15 filex,
which prints the first 15 lines of the file FILEX,
the -15 flag modifies the Head command.



flame
Slang for communicating emotionally and/or
excessively via electronic mail.  See netiquette.



flash BIOS
A PC BIOS that is stored in flash memory rather
than in a ROM.  Flash BIOSs can be upgraded in
place, whereas ROM BIOSs must be replaced with a
newer chip.  See ROM BIOS.



flash disk
A solid state disk made of flash memory.  It
emulates a standard disk drive in contrast with
flash memory cards, which require proprietary
software to make them function.



flash memory
A memory chip that holds its content without power,
but must be erased in fixed blocks rather than
single bytes.  Block sizes typically range from 512
bytes up to 256KB.  The term was coined by Toshiba
for its ability to be erased "in a flash."  Derived
from EEPROMs, flash chips are less expensive and
provide higher bit densities.  Flash is also
becoming an alternative to EPROMS, because it can
be easily updated.

   Flash memory is used in PCMCIA memory cards,
PCMCIA flash disks and other types of solid state
disks, embedded controllers and smart cards.  It
typically has a lifespan of 100K write cycles, but
newer chips can be written a million times.

   If flash memory or a derivative technology can
be made to erase one byte at a time, it may lead to
a non-volatile RAM some day.

   To receive the "Focus On Flash" newsletter on
the flash memory market, contact M-Systems, 556
Mowry Avenue, Suite 103, Fremont, CA 94536,
510/505-9081 (fax 9084).



Flashpoint
A screen scraper from Sterling Software, Atlanta,
GA (formerly KnowledgeWare), that is used to turn a
character-based mainframe screen into a Windows
front end.



flat address space
A memory that is addressed starting with 0.  Each
susequent byte is referenced by the next sequential
number (0, 1, 2, 3, 4, etc.) all the way to the end
of memory.  This is normal addressing in contrast
to segmented addressing, which addresses memory in
blocks.  Contrast with segmented address space.



flat file
A stand-alone data file that does not have any pre-
defined linkages or pointers to locations of data
in other files.  This is the type of file used in a
relational database; however, the term is often
used to refer to a type of file that has no
relational capability, exactly the opposite.  This
business can drive you nuts!



flat panel display
A thin display screen that uses any of a number of
technologies, such as LCD, electroluminscent or
plasma.  Used today in laptops to reduce size and
weight, they will eventually supersede CRTs.



flat screen
(1) A display screen in which the CRT viewing
surface is flatter than most CRTs, which are
slightly rounded.  The flat screen provides less
distortion at the edges.

(2) See flat panel display.



flat shading
In computer graphics, a technique for computing a
one-tone shaded surface to simulate simple
lighting.



flatbed plotter
A graphics plotter that draws on sheets of paper
that have been placed in a bed.  The size of the
bed determines the maximum size sheet that can be
drawn.



flatbed scanner
A scanner that provides a flat, glass surface to
hold pages of paper, books and other objects for
scanning.  The scan head is moved under the glass
across the page.  Sheet feeders are usually
optionally available that allow multiple sheets to
be fed automatically.  Contrast with sheet-fed
scanner, hand-held scanner and drum scanner.



flexible disk
Same as floppy disk and diskette.



flick file
A file format for animation from AutoDesk, Inc.  It
uses the .FLI file extension.



flicker
A fluctuating image on a video screen.  See
interlaced.



flip-flop
An electronic circuit that alternates between two
states.  When current is applied, it changes to its
opposite state (0 to 1 or 1 to 0).  Made of several
transistors, it is used in the design of static
memories and hardware registers.



flippy board
A PC expansion board that connects to both ISA/EISA
and Micro Channel buses.  ISA/EISA connectors are
on one edge of the board; MCA on the other.



flippy-floppy
A single-sided 5.25" floppy converted to double-
sided use by punching a second notch into the disk
so that it can be flipped over and inserted upside
down.  This is not recommended as the disk's
rotation is alternated.



float
In programming, a declaration of a floating point
number.



floating point
A method for storing and calculating numbers in
which the decimal points do not line up as in fixed
point numbers.  The significant digits are stored
as a unit called the mantissa, and the location of
the radix point (decimal point in base 10) is
stored in a separate unit called the exponent.
Floating point methods are used for calculating a
large range of numbers quickly.

   Floating point operations can be implemented in
hardware (math coprocessor), or they can be done in
software.  They can also be performed in a separate
floating point processor that is connected to the
main processor via a channel.

         Mantissa Exponent    Value
        Ŀ
          6508      0      6508   
          6508      1     65080   
          6508     -1       650.8  
        

               Floating Point





floating point processor
An arithmetic unit designed to perform floating
point operations.  It may be a coprocessor chip in
a personal computer, a CPU designed with built-in
floating point capabilities or a separate machine,
often called an array processor, which is connected
to the main computer.



floppy disk
A reusable magnetic storage medium.  It is the
primary method for distributing personal computer
software.  It's also used to transfer data between
users, although local area networks can eliminate
much of this "sneakernet."

   Also called a diskette, the floppy is a flexible
disk, similar to tape, with both surfaces used for
magnetic recording.  The disk drive grabs the
floppy's center and spins it inside its housing,
and the read/write head makes contact with the
surface through an opening in the floppy's
envelope, case or cartridge.

   Floppies are much slower than hard disks,
because they spin at 300 rpm, a tenth the rotation
of a hard disk, and they are at rest until a data
transfer is requested.  In order of first to last
developed, the major types are:

 Creator   External format          Capacity
 IBM       8" flexible envelope     100 - 500KB
 Shugart   5.25" flexible envelope  100KB - 1.2MB
 Sony      3.5" rigid case          400KB - 4MB +

   Although floppy disks look the same, what's
recorded on them determines their capacity and
compatibility.  Each new floppy must be
"formatted," which records the sectors on the disk
that will hold the data.  PC, Mac, Apple II, Amiga
and Atari formats are different, although most can
read and write PC (DOS) diskettes.  See format
program, Floptical and magnetic disk.



FLOPS
(FLoating point Operations Per Second)  A unit of
measurement of floating point calculations.  For
example, 100 megaflops is 100 million floating
point operations per second.



Floptical
A type of floppy disk from Insite Peripherals,
Inc., San Jose, CA, that records data magnetically,
but uses grooves in the disk to optically align the
head over the tracks.  The first 3.5" Floptical
drive uses 21MB diskettes and can also read and
write 720KB and 1.44MB diskettes.



flow chart
See flowchart.



flow control
(1) In communications, the management of
transmission between two devices.  It is concerned
with the timing of signals and enables slower-speed
devices to communicate with higher-speed ones.
There are various techniques, but all are designed
to ensure that the receiving station is able to
accept the next block of data before the sending
station sends it.  See xon-xoff.

(2) In programming, the if-then and loop statements
that make up the program's logic.



flowchart
A graphical representation of the sequence of
operations in an information system or program.
Information system flow charts show how data flows
from source documents through the computer to final
distribution to users.  Program flow charts show
the sequence of instructions in a single program or
subroutine.  Different symbols are used to draw
each type of flow chart.



flush
To empty the contents of a memory buffer onto disk.



flush center
               The centering,
              of text uniformly
       between the left and right margins.



flush left
The alignment of text uniformly to the left margin.
All text is typically set flush left as is this
paragraph.



flush right
The alignment of text uniformly to the right
              margin while the left margin is
                             set ragged left.



flux
The energy field generated by a magnet.



FM
(1) (Frequency Modulation)  A transmission
technique that blends the data signal into a
carrier by varying (modulating) the frequency of
the carrier.  See modulate.

(2) (Frequency Modulation)  An earlier magnetic
disk encoding method that places clock bits onto
the medium along with the data bits.  It has been
superseded by MFM and RLL.



FM synthesis
A MIDI technique that simulates the sound of
musical instruments.  It uses operators, typically
four of them, which create wave forms or modulate
the wave forms.  FM synthesis does not create sound
as faithfully as wave table synthesis, which uses
actual samples of the instruments.



Fn key
(FuNction key)  A keyboard key that works like a
shift key to activate the second function on a
dual-purpose key, typically found on laptops to
reduce keyboard size.  It is different than the
function keys F1, F2, etc.



FOCA
(Font Object Content Architecture)  See MO:DCA.



FOCUS
(1) A DBMS from Information Builders, Inc., New
York, that runs on PCs, mainframes and minis.  It
allows relational, hierarchical and network data
structures and can access a variety of databases,
including standard IBM mainframe files, DB2, IMS,
IDMS and others.  It includes a fourth-generation
language and a variety of decision support
facilities.

(2) (Federation On Computing in the U.S.)  The U.S.
representative of IFIP.  Address: IEEE Computer
Society, 1730 Mass. Ave. N.W., Washington, DC
20036, 202/371-0101.



FOIA
(Freedom Of Information Act)  A U.S. Government
rule that states that public information shall be
delivered within 10 days of request.



FOIRL
(Fiber Optic Inter Repeater Link)  An IEEE standard
for fiber optic Ethernet.  FOIRL and 10BaseF are
compatible, but FOIRL is an earlier standard
generally used to extend a backbone beyond the 328
foot limitation of 10BaseT.  FOIRL is limited to .6
miles distance per segment, whereas 10BaseF
segments can extend to 1.2 miles.  10BaseF is a
more comprehensive standard for complete fiber-
based installations.



folder
In the Macintosh, a simulated file folder that
holds documents (text, data or graphics),
applications and other folders.  A folder is like a
DOS directory.  A folder within a folder is like a
DOS subdirectory.

   Foldering is implemented in various Windows and
UNIX shells in order to simplify file management.



foldering
Using folders to store and manipulate documents on
screen.



Folio
(1) Text management software for PCs from Folio
Corporation, Provo, UT, that provides storage,
retrieval and hypertext capability for text
databases.  It can import text from over 40 file
formats.  Folio files are called "Infobases."

(2) (folio) In typography, a printed page number.
For example, folio 3 could be the 27th physical
page in a book.



font
A set of type characters of a particular typeface
design and size.  Usually, each typeface (Times
Roman, Helvetica, Arial, etc.) is made available in
four variations: normal weight, bold, italic and
bold italic.  Thus, for bitmapped fonts, which are
fully generated ahead of time, four fonts would be
required for each point size used in each typeface.
For scalable fonts, which are generated in any
point size on the fly, only four fonts would be
required for each typeface.

   Fonts come built into the printer, as plug-in
cartridges or as soft fonts, which reside on the
computer's hard disk or a hard disk built into the
printer.  See bitmapped font and scalable font.



font cartridge
A set of bitmapped or outline fonts for one or more
typefaces contained in a plug-in module for the
printer.  The fonts are stored in a ROM chip within
the cartridge.  Contrast with soft font and
internal font.



font characteristics
Font selection in an HP LaserJet is made by sending
a coded command to the printer with the following
criteria:

  Code               Characteristic

Typeface     Design (Courier, Times Roman, etc.)
Orientation  Portrait or landscape
Symbol set   Country or special characters
Spacing      Proportional or fixed spacing (width)
Pitch        Characters per inch (if fixed spacing)
Point size   Height of characters
Style        Upright or italic
Stroke       Light, medium or bold appearance
 weight





font compiler
Same as font generator.



font editor
Software that allows fonts to be designed and
modified.



font family
A set of fonts of the same typeface in assorted
sizes, including bold, italic and bold italic
variations.



font generator
Software that converts an outline font into a
bitmap (dot pattern required for a particular font
size).  Font generation is not linear, simply
expanding a letter to any size.  As fonts get
bigger, their characteristics must change in order
to make them attractive.

   Font generation is used to create bitmapped
fonts, which are fully generated and stored on disk
before use.  Contrast with font scaler, which
generates the font in any point size the instant it
is needed for display or printing.



font manager
See font scaler.



font metric
Typographic information (width, height, kerning)
for each character in a font.



font number
An identification number assigned to a font.  A
program references the font by this number.



font rasterizer
See font scaler.



font scaler
Software that converts scalable fonts into bitmaps
on the fly as required for display or printing.
Examples are TrueType, Adobe Type Manager and
Bitstream's Facelift.  See scalable font and font
generator.



font style
A typeface variation (normal, bold, italic, bold
italic).



font utility
Software that provides functions for managing
fonts, including the ability to download, install,
design and modify fonts.



font weight
The thickness of characters (light, medium or
bold).



Fontware
A font generator for various DOS applications from
Bitstream Inc., Cambridge, MA, which includes a
library of typeface outlines in normal, italic,
bold and bold italic weights.  FontWare has been
discontinued in favor of newer scalable font
technogies.  See font scaler.



foo
A popular name for a temporary file, function or
variable, or example of same.  Often used in
conjunction with "bar," from "fubar" (Fouled Up
Beyond All Recognition).



footer
In a document or report, common text that appears
at the bottom of every page.  It usually contains
the page number.



footnote
Text that appears at the bottom of a page, which
adds explanation.  It is often used to give credit
to the source of information.  When accumulated and
printed at the end of a document, they are called
endnotes.



footprint
The amount of geographic space covered by an
object.  A computer footprint is the desk or floor
surface it occupies.  A satellite's footprint is
the earth area covered by its downlink.



for statement
A high-level programming language structure that
repeats a series of instructions a specified number
of times.  It creates a loop that includes its own
control information.  The following examples print
"Hello" 10 times:

     BASIC                       C
  for x = 1 to 10     for (x = 0;  x < 10;  x++)
   print "hello"       printf ("hello\n");
  next x





Force
A dBASE compiler from Sophco, Inc., Boulder, CO,
that combines C and dBASE structures.  It is noted
for generating very small executable programs.



Fore Systems
(Fore Systems, Inc., Warrendale, PA)  A
manufacturer of ATM switches and network adapters.
Fore is the pioneer in ATM adapters for LANs and is
a market leader in ATM products.



foreground/background
The priority assigned to programs running in a
multitasking environment.  In a multiuser
environment, foreground programs have highest
priority, and background programs have lowest.
Online users are given the foreground, and batch
processing activities (sorts, updates, etc.) are
given the background.  If batch activities are
given a higher priority, terminal response times
may slow down considerably.

   In a personal computer, the foreground program
is the one the user is currently working with, and
the background program might be a print spooler or
communications program.



foreign key
In relational database, it is a field in one table
that is indexed in another.  Foreign keys provide
the building blocks for relating tables.  For
example, in a customer order table, the salesperson
field might contain an employee number.  That field
would be a foreign key in the table, because the
employee table would be indexed on employee number.


    CUSTOMER ORDER TABLE
    order no.  (primary key)
    salesperson (foreign key) Ŀ
    etc.                       
                               
            
             EMPLOYEE TABLE
             employee no. (primary key)
              employee name
              etc.





ForeRunner
A family of ATM adapters from Fore Systems,
Warrendale, PA.



Forest & Trees
A data analysis program for PCs from Trinzic
Corporation, Portsmouth, NH, that integrates data
from a variety of applications.  It provides a
control room interface that lets users monitor
important business information.



fork
(1) In UNIX, to make a copy of a process for
execution.

(2) In the Macintosh, a part of a file.  See data
fork and resource fork.



form
(1) A paper form used for printing.

(2) A screen display designed for a particular
application.



form factor
The physical size of a device.



form feed
Advancing a printer form to the top of the next
page.  It is done by pressing the printer's form
feed (FF) button or by sending the form feed code
(ASCII 12) to the printer from the computer.



form view
A screen display showing one item or record
arranged like a preprinted form.  Contrast with
table view.



format
The structure, or layout, of an item.

   Screen formats are the layout of fields on the
screen.

   Report formats are the columns, headers and
footers on a page.

   Record formats are the fields within a record.

   File formats are the structure of data and
program files, word processing documents and
graphics files (display lists and bitmaps) with all
their proprietary headers and codes.  See format
program, disk format, DOS Format and style sheet.



format program
Software that initializes a disk.  There are two
formatting levels.  The low-level initializes the
disk surface by creating the physical tracks and
storing sector identification in them.  Low-level
format programs lay out the sectors as required by
the particular drive technology used (IDE, SCSI,
etc.).

   The high-level format creates the indexes used
by the operating system (Mac, DOS, etc.) to keep
track of data stored in the sectors.

   Floppy disk format programs perform both levels
on a diskette.  See DOS Format.



forms software
(1) Workflow automation software used to create on-
screen data entry forms and provide e-mail routing
and tracking of the resulting electronic documents.

(2) Program development tools that build
applications by designing the on-screen forms for
data entry, update and so on.  The forms are
generally designed with visual programming tools
that allow fields, buttons and logos to be drawn
directly on screen.  The business logic is either
selected via menus and/or written in behind each
field or button with lines of 4GL or 3GL
programming code.



formula
(1) An arithmetic expression that solves a problem.
For example, (fahrenheit-32)*5/9 is the formula for
converting Fahrenheit to Celsius.

(2) In spreadsheets, an algorithm that identifies
how the data in a specific number of cells is to be
calculated.  For example, +C3*D8 means that the
contents of cell C3 are to be multipled by the
contents of cell D8 and the results are to be
placed where the formula is located.



Forte
An application development system for enterprise
client/server environments from Forte Software,
Inc., Oakland, CA.  Introduced in 1994, it is a
repository-driven system that supports Windows, Mac
and Motif clients and all the major UNIX servers as
well as VMS.  It supports Oracle, Sybase and Rdb
databases and provides partitioning for creating
three-tier applications.  Testing and debugging is
done in an interpreted mode while production
programs are compiled into C++ code.



FORTH
(FOuRTH-generation language)  A high-level
programming language created by Charles Moore in
the late 1960s as a way of providing direct control
of the computer.  Its syntax resembles LISP, it
uses reverse polish notation for calculations, and
it is noted for its extensibility.

   It is both compiler and interpreter.  The source
program is compiled first and then executed by its
operating system/interpreter.  It is used in
process control applications that must quickly
process data acquired from instruments and sensors.
It is also used in arcade game programming as well
as robotics and other AI applications.  The
following polyFORTH example converts Fahrenheit to
Celsius:

   : CONV ( n) 32 - 5 9 * / . ." Celsius
   : USER_INPUT  ." Enter Fahrenheit " CONV ;





FORTRAN
(FORmula TRANslator)  The first high-level
programming language and compiler, developed in
1954 by IBM.  It was originally designed to express
mathematical formulas, and although it is used
occasionally for business applications, it is still
the most widely used language for scientific,
engineering and mathematical problems.

   FORTRAN IV is an ANSI standard, but FORTRAN V
has various proprietary versions.
   The following example converts Fahrenheit to
Celsius:

   WRITE(6,*) 'Enter Fahrenheit '
   READ(5,*) XFAHR
   XCENT = (XFAHR - 32) * 5 / 9
   WRITE(6,*) 'Celsius is ',XCENT
   STOP
   END





forum
An information interchange regarding a specific
topic or product that is hosted on an online
service or BBS.  It can include the latest news on
the subject, a conferencing capability for
questions and answers by participants as well as
files for downloading fixes, demos and other
related material.



forward chaining
In AI, a form of reasoning that starts with what is
known and works toward a solution.  Known as
bottom-up approach.  Contrast with backward
chaining.



forward compatible
Same as upward compatible.



forward error correction
A communications technique that can correct bad
data on the receiving end.  Before transmission,
the data is processed through an algorithm that
adds extra bits for error correction.  If the
transmitted message is received in error, the
correction bits are used to repair it.



fountain fill
In computer graphics, a painted area that smoothly
changes its color or pattern density.  A radial
fountain fill starts at the center of an area and
radiates outward.



fourth-generation computer
A computer made up almost entirely of chips with
limited amounts of discrete components.  We are
currently in the fourth generation.



fourth-generation language
Also known as a 4GL, it is a computer language that
is more advanced than traditional high-level
programming languages.  For example, in dBASE, the
command List displays all the records in a data
file.  In second- and third-generation languages,
instructions would have to be written to read each
record, test for end of file, place each item of
data on screen and go back and repeat the operation
until there are no more records to process.

   First-generation languages are machine
languages; second-generation are machine dependent
assembly languages; third-generation are high-level
programming languages, such as FORTRAN, COBOL,
BASIC, Pascal, and C.

   Although many languages, such as dBASE, are
called fourth-generation languages, they are
actually a mix of third and fourth.  The dBASE List
command is a fourth-generation command, but
applications programmed in dBASE are third-
generation.  The following example shows the
difference between dBASE third- and fourth-
generation syntax to open a customer file and
display all names and addresses on screen.

       dBASE 3GL                dBASE 4GL

    use customer             use customer
    do while .not. eof       list name, address
      ? name, address
      skip
    enddo


   Query language and report writers are also
fourth-generation languages.  Any computer language
with English-like commands that doesn't require
traditional input-process-output logic falls into
this category.





FoxBASE+
A dBASE III PLUS-compatible DBMS for the Macintosh
from Microsoft.  Originally developed by Fox
Software for the PC, FoxBASE gained a reputation
for its speed and compatibility.



FoxPro
A dBASE IV-compatible DBMS from Microsoft for PCs.
An enhanced version of FoxBASE, FoxPro includes
windowing, SQL and QBE interfaces and "Rushmore"
technology for fast queries on large databases.



FPGA
(Field Programmable Gate Array)  A programmable
logic chip with a high density of gates.



fps
(1) (Frames Per Second)  See frame.

(2) (FPS) (Floating Point Systems, Inc., Beaverton,
OR)  A supercomputer manufacturer.



FPU
(Floating Point Unit)  A computer circuit that
handles floating point operations.



Fractal Design Painter
See Painter.



fractals
A technique for describing and greatly compressing
images, especially natural objects, such as trees,
clouds and rivers.  It turns an image into a set of
data and an algorithm for expanding it back to the
original.

   The term comes from "fractus," which is Latin
for broken or fragmented.  It was coined by IBM
Fellow and doctor of mathematics Benoit Mandelbrot,
who expanded on ideas from earlier mathematicians
and discovered similarities in chaotic and random
events and shapes.



fractional T1
A service that provides less than full T1 capacity.
One or more 64 Kbits/sec channels are provided.



FRAD
(Frame Relay Assembler/Dissassembler)  A
communications device that formats outgoing data
into the format required by a frame relay network.
It strips the data back out at the other end.  It
is the frame relay counterpart to the X.25 PAD.



fragmentation
The non-contiguous storage of data on disk.  As
files are updated, new data is stored in available
free space, which may not be contiguous.
Fragmented files cause extra head movement, slowing
disk accesses.  A disk maintenance, or optimizer,
program is used to rewrite and reorder all the
files.



FRAM
(1) (Ferroelectronic RAM)  A non-volatile
semiconductor memory that retains its content
without power for up to 10 years.

(2) (Ferromagnetic RAM)  A non-volatile memory that
records microscopic bits on a magnetic surface.



frame
(1) In computer graphics, one screenful of data or
its equivalent storage space.

(2) In communications, a fixed block of data
transmitted as a single entity.  Also called a
packet.

(3) In desktop publishing, a movable, resizable box
that holds a graphic image.

(4) In AI, a data structure that holds a general
description of an object, which is derived from
basic concepts and experience.



frame buffer
A separate memory bank used to hold a graphic
image.  It can be built with one plane of memory
for each bit in the pixel.  For example, if eight
bits are used per pixel, eight memory planes are
used.



frame grabber
A device that accepts standard TV signals and
digitizes the current video frame into a bitmap
image.



frame relay
A high-speed packet switching protocol used for
wide area networks (WANs).  It is faster than
traditional X.25 networks, because it was designed
for today's reliable circuits and performs less
rigorous error detection.  It provides for a
granular service up to DS1 rates of 1.544 Mbps and
is suited for data and image transfer.  Because of
its variable-length packet architecture, it is not
the most efficient technology for realtime voice
and video.



FrameMaker
A desktop publishing program from Frame Technology
Corporation, San Jose, CA, that runs on UNIX
platforms, Macintosh and Windows.  It is noted for
its large number of advanced features, including
full text and graphics editing capabilities.
Optional viewers let documents run on machines
without FrameMaker, providing a way to distribute
hypertext-based help systems.



framework
(1) In object-oriented programming, a generalized
subsystem design for building applications.  It
consists of abstract classes and their object
collaboration as well as concrete classes.  While
object-oriented programming supports software
reuse, frameworks support design reuse.

(2) (FrameWork)  One of the first integrated
software packages for PCs that included a
programming language.  It was developed by Ashton-
Tate, later acquired by Borland.



framing bit
Same as start bit and stop bit.



free-form database
A database system that allows entry of text without
regard to length or order.  Although it accepts
data as does a word processor, it differs by
providing better methods for searching, retrieving
and organizing the data.



free-form language
A language in which statements can reside anywhere
on a line or even cross over lines.  It does not
imply less syntax structure, just more freedom in
placing statements.  For example, any number of
blank spaces are allowed between symbols.  Most
high-level programming languages are free-form.



Free Software Foundation
A non-profit organization founded in 1985 by
Richard Stallman, dedicated to eliminating
restrictions on copying and modifying programs by
promoting the development and use of freely
redistributable software.  Its GNU computing
environment, X Windows and other programs are
available for a transaction charge.  Address: 675
Mass. Ave., Cambridge, MA 02139, 617/876-3296,
Internet: gnu@prep.ai.mit.edu.  See League for
Programming Freedom.



FreeHand
See Aldus FreeHand.



Freelance Graphics
A presentation graphics program for Windows from
Lotus that is also part of Lotus' SmartSuite set of
applications.



freeware
Software distributed without charge.  Ownership is
retained by the developer who has control over its
redistribution, including the ability to change the
next release of the freeware to payware.  See
shareware and public domain software.



freeze-frame video
Video transmission in which the image is changed
once every couple of seconds rather than 30 times
per second as is required in full-motion video.



frequency
The number of oscillations (vibrations) in an
alternating current within one second.  See
carrier.



frequency division multiplexing
See FDM.



frequency modulation
See FM.



frequency shift
See FSK.



friction feed
A mechanism that allows cut paper forms to be used
in a printer.  The paper is passed between the
platen and a roller that presses tightly against
it.  Contrast with tractor feed.



frob
Slang for manipulating and adjusting dials and
buttons for fun.  From "frobnicate."



front-end CASE
CASE tools that aid in systems analysis and design.
Contrast with back-end CASE.



front end processor
A computer that handles communications processing
for a mainframe.  It connects to the communications
lines on one end and the mainframe on the other.
It transmits and receives messages, assembles and
disassembles packets and detects and corrects
errors.  It is sometimes synonymous with a
communications controller, although the latter is
usually not as flexible.



frontware
Same as screen scraper.



FSK
(Frequency Shift Keying)  A simple modulation
technique that merges binary data into a carrier.
It creates only two changes in frequency: one for
0, another for 1.



FSN
(Full-Service Network)  A communications network
that provides shopping, movies on demand and access
to databases and a variety of online, interactive
services.  Telephone, cable and TV companies are
positioning themselves to provide FSN services that
are expected to evolve throughout the 1990s.



FSR
(Free System Resource)  In Windows, the amount of
unused memory in a 64K block (128K for Version 3.1)
reserved for managing current applications.  Every
open window takes some space in this area.  See
Windows memory limitation.



FT-1
See fractional T1.



FT1
See fractional T1.



FTAM
(File Transfer Access and Management)  A
communications protocol for the transfer of files
between systems of different vendors.



FTP
(File Transfer Protocol/File Transfer Program)  In
a TCP/IP network (Internet, UNIX, etc.), a set of
commands used to log onto the network, list
directories and copy files.  It can also convert
between the ASCII and EBCDIC character codes.  See
anonymous FTP and TFTP.



FTP site
A computer system on the Internet that maintains
files for downloading.  See anonymous FTP.



FTS 2000
(Federal Telecommunications System 2000)  A digital
fiber-optic network providing voice, video, e-mail
and high-speed data communications for the U.S.
government.  AT&T and Sprint are the major
equipment providers.



FTX
(Fault Tolerant UNIX)  Stratus Computer's version
of UNIX System V for its XA/R fault tolerant
computer systems.



FUD factor
(Fear Uncertainty Doubt factor)  A marketing
strategy used by a dominant or privileged
organization that restrains competition by not
revealing future plans.



full backup
See backup types.



full bleed
See bleed.



full-duplex
Transmitting and receiving simultaneously.  In pure
digital networks, this is achieved with two pairs
of wires.  In analog networks or in digital
networks using carriers, it is achieved by dividing
the bandwidth of the line into two frequencies, one
for sending, the other for receiving.



full-duplex Ethernet
See FDSE.



full featured
Hardware or software that provides capabilities and
functions comparable to the most advanced models or
programs of that category.



full-motion video
Video transmission that changes the image 30 frames
per second (30 fps).  Motion pictures are run at 24
fps, which is the minimum frequency required to
eliminate the perception of moving frames and make
the images appear visually fluid to the eye.

   TV video generates 30 interlaced frames per
second, which is actually transmitted as 60 half
frames per second.

   Video that has been digitized and stored in the
computer can be displayed at varying frame rates,
depending on the speed of the computer.  The slower
the computer, the more jerky the movement.
Contrast with freeze-frame video.



full path
A path name that includes the drive (if required),
starting or root directory, all attached
subdirectories and ending with the file or object
name.  Contrast with relative path.  See path.



full project life cycle
A project from inception to completion.



full-screen mode
A programming capability that allows data to be
displayed in any row, column or pixel location on
screen.  Contrast with teletype mode.



full-service network
See FSN.



fully populated
A circuit board whose sockets are completely filled
with chips.



function
In programming, a self-contained software routine
that peforms a job for the program it is written in
or for some other program.  The function performs
the operation and returns control to the
instruction following the calling instruction or to
the calling program.  Programming languages provide
a set of standard functions and may allow
programmers to define others.  For example, the C
language is built entirely of functions.



function call
A request by a program to use a function within the
program itself or within another program.  The
request is made by stating the name of the function
followed by any values (parameters, arguments) that
may have to be passed to it.  Values which are
results from the operation performed by the
function may be returned back to the calling
program.

   The function may be written within the program,
be part of an external library that is combined
with the program when it is compiled or be
contained in another program, such as the operating
system or DBMS.



function keys
A set of keyboard keys used to command the computer
(F1, F2, etc.).  F1 is often the help key, but the
purpose of any function key is determined by the
software currently running.



function library
A collection of program routines.  See function.



function overloading
In programming, using the same name for two or more
functions.  The compiler determines which function
to use based on the type of function, arguments
passed to it and type of values returned.



function prototyping
In programming, formally defining each function in
the program with the number and types of parameters
passed to it and its return values.  The compiler
can then report an error if a function is not
written to conform to the prototype.



functional decomposition
Breaking down a process into non-redundant
operations.



functional specification
The blueprint for the design of an information
system.  It provides documentation for the
database, human and machine procedures, and all the
input, processing and output detail for each data
entry, query, update and report program in the
system.



fuse
(1) A protective device that is designed to melt,
or blow, when a specified amount of current is
passed through it.  PROM chips are created as a
series of fuses that are selectively blown in order
to create the binary patterns of the data or
machine language.

(2) To bond together.



fusible link
A circuit line in a PROM chip or similar device
that is designed to be blown apart.  See PROM
programmer.



Futurebus+
An IEEE standard multisegment bus that can transfer
data at 32, 64, 128 and 256-bits and can address up
to 64 bits.  Clock speeeds range from 25 to 100MHz.
At 100MHz and 256 bits, it transfers 3.2
Gbytes/sec.



fuzzy computer
A specially-designed computer that employs fuzzy
logic.  Using such architectural components as
analog circuits and parallel processing, fuzzy
computers are designed for AI applications.



fuzzy logic
A mathematical technique for dealing with imprecise
data and problems that have many solutions rather
than one.  Although it is implemented in digital
computers which ultimately make only yes-no
decisions, fuzzy logic works with ranges of values,
solving problems in a way that more resembles human
logic.

   Fuzzy logic is used for solving problems with
expert systems and realtime systems that must react
to an imperfect environment of highly variable,
volatile or unpredictable conditions.  It "smoothes
the edges" so to speak, circumventing abrupt
changes in operation that could result from relying
on traditional either-or and all-or-nothing logic.

   Fuzzy logic was conceived by Lotfi Zadeh, former
chairman of the electrical engineering and computer
science department at the University of California
at Berkeley.  In 1964, while contemplating how
computers could be programmed for handwriting
recognition, Zadeh expanded on traditional set
theory by making membership in a set a matter of
degree rather than a yes-no situation.



fuzzy logician
An individual who is involved in developing fuzzy
logic algorithms.



fuzzy search
An inexact search for data that finds answers that
come close to the desired data.  It can get results
when the exact spelling is not known or help users
obtain information that is loosely related to a
topic.



G
See giga.



G-byte
See gigabyte.



gain
The amount of increase that an amplifier provides
on the output side of the circuit.



GAL
(Generic Array Logic)  A programmable logic chip
(PLD) technology from Lattice Semiconductor.



gallium arsenide
An alloy of gallium and arsenic compound (GaAs)
that is used as the base material for chips.  It is
several times faster than silicon.



game port
An I/O connector used to attach a joy stick.  It is
typically a 15-pin socket on the back of a PC.  See
serial port.



gamma correction
In computer graphics, using a formula to provide a
range of intensities that appear uniform to the
human eye.


3
gang punch
To punch an identical set of holes into a deck of
punched cards.



Gantt chart
A form of floating bar chart usually used in
project management to show resources or tasks over
time.



gap
(1) The space between blocks of data on magnetic
tape.

(2) The space in a read/write head over which
magnetic flux (energy) flows causing the underlying
magnetic tape or disk surface to become magnetized
in the corresponding direction.



gapless
A magnetic tape that is recorded in a continuous
stream without interblock gaps.



garbage collection
A routine that searches memory for program segments
or data that are no longer active in order to
reclaim that space.



garbage in...
See GIGO.



GAS
See gallium arsenide.



gas discharge display
See plasma display.



gas plasma
See plasma display.



gate
(1) An open/closed switch.

(2) A pattern of transistors that makes up an AND,
OR or NOT Boolean logic gate.  See gate array.

(3) In a MOS transistor, the line that triggers the
switch.



gate array
A type of chip that contains unconnected logic
elements, typically two-input NAND gates.  NAND
gates can be interconnected to provide all the
Boolean operations required for digital logic.  The
chip is completed by designing and adhering the top
metal layer that provides the pathways between
them.  This final masking stage is less costly than
designing the chip from scratch.



gated
Switched "on" or capable of being switched on and
off.



gateway
(1) A computer that performs protocol conversion
between different types of networks or
applications.  For example, a gateway can connect a
personal computer LAN to a mainframe network.  An
electronic mail, or messaging, gateway converts
messages between two different messaging protocols.
See bridge.

(2) (Gateway) (Gateway 2000, N. Sioux City, SD)  A
PC manufacturer founded in 1985 by Ted Waitt and
Mike Hammond.  With fiscal 1993 revenues of 1.7
billion dollars, it is one of the largest direct
marketers of PCs in the U.S.  Gateway first sold
peripherals to owners of Texas Instrument
computers.  In 1987, it began to offer complete
systems and has continued to drive down the cost of
quality PCs by mail.



gather write
To output data from two or more noncontiguous
memory locations with one write operation.  See
scatter read.



GatorBox
A gateway from Cayman Systems, Inc., Cambridge, MA,
that interconnects LocalTalk and Ethernet networks
and supports TCP/IP and NFS protocols.  It also
functions as a router to connect AppleTalk-based
computers on a LAN with remote AppleTalk devices.



gauss
A unit of measurement of magnetic energy.



Gaussian distribution
A random distribution of events that is often
graphed as a bell-shaped curve.  It is used to
represent a normal or statistically probable
outcome.



Gaussian noise
In communications, a random interference generated
by the movement of electricity in the line.  Also
called white noise.



GB, Gb
See gigabyte and gigabit.



Gbit
See gigabit.



Gbits/sec
(GigaBITS per SECond)  Billion bits per second.



GBps, Gbps
(GigaBytes Per Second, GigaBits Per Second)
Billion bytes per second.  Billion bits per second.



Gbs
(GigaBits per Second)  Same as Gbps.



GByte
See gigabyte.



Gbytes/sec
(GigaBYTES per SECond)  Billion bytes per second.



GCOS
A Bull HN operating system used in its minis and
mainframes (formerly Honeywell's product).



GCR
(1) (Group Code Recording)  An encoding method used
on magnetic tapes and Apple II and Mac 400K and
800K floppy disks.

(2) (Gray Component Replacement)  A method for
reducing the amount of printing ink used.  It
substitutes black for the amount of gray contained
in a color, thus black ink is used instead of the
three CMY inks.  See UCR and dot gain.



GDDM
(Graphical Data Display Manager)  Software that
generates graphics images in the IBM mainframe
environment.  It contains routines to generate
graphics on terminals, printers and plotters as
well as accepting input from scanners.  Programmers
use it for creating graphics, but users can employ
its Interactive Chart Utility (ICU) to create
business graphics without programming.

   GDDM/graPHIGS is a programming environment that
combines graphics capability with a user interface
similar to the Presentation Manager in OS/2.



GDI
(Graphics Device Interface)  The Windows graphics
language used to provide output to the screen and
printer.  Applications call the GDI functions in
Windows to display and print.  GDI in turn calls
the screen and printer drivers to produce the final
output.



GDM
See CGM.



GE
(Greater than or Equal to)  See relational
operators.



GEM
(Graphics Environment Manager)  A graphical user
interface from Digital Research similar to the
Mac/Windows environment.  It is built into ROM in
several Atari computers.  The DOS version of
Ventura Publisher came with a runtime version.



gender changer
A coupler that reverses the gender of one of the
connectors in order that two male connectors or two
female connectors can be joined together.



General failure error reading drive x
A DOS error message.  The full message is

    General failure reading drive X
    Abort, Retry, Fail?

This usually means that an unformatted floppy is
being used.  Press A to Abort, format the floppy
and try again.

   You'll also get this if you try to read a high-
density disk in a low-density drive.  High-density
disks require high-density drives.



General Magic
(General Magic, Inc., Sunnyvale, CA)  A spinoff of
Apple Computer in 1990.  Its mission is to create
new personal intelligent communications products
and services by developing and licensing technology
to a wide variety of manufacturers and service
providers.  It has formed an alliance with large
organizations such as AT&T, Sony, Philips and
Motorola in order to reach the widest possible
audience.  See Telescript and Magic Cap.



General MIDI
A standard set of 128 sounds for MIDI sound cards
and devices (synthesizers, sound modules, etc.).
By assigning instruments to specific MIDI patch
locations, General MIDI provides a standard way of
communicating MIDI sound.

   MIDI's small storage requirement makes it very
desirable as a musical sound source for multimedia
applications compared to digitizing actual music.
For example, a three-minute MIDI file may take only
20 to 30K, whereas a WAV file (digital audio) could
consume up to several megabytes depending on sound
quality.



General Protection Fault
See GPF.



general-purpose computer
Refers to computers that follow instructions, thus
virtually all computers from micro to mainframe are
general purpose.  Even computers in toys, games and
single-function devices follow instructions in
their built-in program.  In contrast, computational
devices can be designed from scratch for special
purposes (see ASIC).



general-purpose controller
A peripheral control unit that can service more
than one type of peripheral device; for example, a
printer and a communications line.



general-purpose language
A programming language used to solve a wide variety
of problems.  All common programming languages
(FORTRAN, COBOL, BASIC, C, Pascal, etc.) are
examples.  Contrast with special-purpose language.



generalized program
Software that serves a changing environment.  By
allowing variable data to be introduced, the
program can solve the same problem for different
users or situations.  For example, the electronic
versions of this database could be programmed to
read in a different title and thus be used for any
type of dictionary.



generator
(1) Software that creates software.  See
application generator and macro generator.

(2) A device that creates electrical power or
synchonization signals.



Generic CADD
A full-featured CADD package for DOS from AutoDesk,
Inc., Sausalito, CA, that offers levels for
beginner, intermediate and advanced users.  It was
originally developed by Generic Software of
Bothell, WA.



GEnie
(General Electric Network for Information Exchange)
An online information service from GE Information
Services that provides business information, news
and access to special interest groups.  See online
services.



Genifer
A dBASE application generator from Bytel
Corporation, Berkeley, CA, that creates dBASE
source code.



genlock
(generator lock)  Circuitry that synchronizes video
signals for mixing.  In personal computers, a
genlock display adapter converts screen output into
an NTSC video signal, which it synchronizes with an
external video source.



GEO
See geosynchronous.



geographic information system
See GIS.



geostationary
Same as geosynchronous.



geosynchronous
Earth aligned.  Refers to communications satellites
that are placed 22,282 miles above the equator and
travel at the same speed as the earth's rotation,
thus appearing stationary.  Contrast with LEO.



GeoWorks Ensemble
A graphical operating environment for DOS from
GeoWorks, Inc., Berkeley, CA, that includes word
processing, drawing, communications, card file and
calendar applications.  It provides complete DOS
file management and simulates file folders like the
Macintosh.  Users can launch all applications from
within Ensemble.  GeoWorks Pro includes the Quattro
Pro spreadsheet.



germanium
(Ge) The material used in making the first
transistors.  Although still used in very limited
applications, germanium was replaced by silicon
years ago.



gesture recognition
The ability to interpret simple hand-written
symbols such as check marks and slashes.



get
(1) In programming, a request for the next record
in an input file.  Contrast with put.

(2) An FTP command to copy a file or to display the
contents of a text file.



Gflops
See gigaflops.



ghost
(1) A faint second image that appears close to the
primary image on a display or printout.  In
transmission, it is a result of secondary signals
that arrive ahead of or later than the primary
signal.  On a printout, it is caused by bouncing
print elements as the paper passes by.

(2) To display a menu option in a dimmed, fuzzy
typeface, indicating it is not selectable at this
time.



GHz
(GigaHertZ)  One billion cycles per second.



GIF
(Graphics Interchange Format)  A popular raster
graphics file format developed by CompuServe that
handles 8-bit color (256 colors) and uses the LZW
method to achieve compression ratios of
approximately 1.5:1 to 2:1.



giga
Billion.  Abreviated "G."  It often refers to the
precise value 1,073,741,824 since computer
specifications are usually binary numbers.  See
binary values and space/time.



gigabit
One billion bits.  Also Gb, Gbit and G-bit.  See
giga and space/time.



gigabyte
One billion bytes.  Also GB, Gbyte and G-byte.  See
giga and space/time.



gigaflops
(GIGA FLoating point OPerations per Second)  One
billion floating point operations per second.



GIGO
(Garbage In Garbage Out)  "Bad input produces bad
output."  Data entry is critical.  All possible
tests should be made on data entered into a
computer.

   GIGO also means "Garbage In, Gospel Out."
People put too much faith in computer output!



GIS
(1) (Geographic Information System)  A digital
mapping system used for exploration, demographics,
dispatching and tracking.

(2) (Generalized Information System)  An early IBM
mainframe query and data manipulation language.



GKS
(Graphical Kernel System)  A device-independent
graphics language for 2-D, 3-D and raster graphics
images.  It allows graphics applications to be
developed on one system and easily moved to another
with minimal or no change.  It was the first true
standard for graphics applications programmers and
has been adopted by both ANSI and ISO.



glare filter
A fine mesh screen that is placed over a CRT screen
to reduce glare from overhead and ambient light.



glitch
A temporary or random hardware malfunction.  It is
possible that a bug in a program may cause the
hardware to appear as if it had a glitch in it and
vice versa.  At times it can be extremely difficult
to determine whether a problem lies within the
hardware or the software.



global
Pertaining to an entire file, database, volume,
program or system.



global variable
In programming, a variable that is used by all
modules in a program.



Global Virtual Private Network
See GVPN.



glossary
A term used by Microsoft Word and adopted by other
word processors for the list of shorthand, keyboard
macros created by a particular user.  See also
About this database.



glue chip
A support chip that adds functionality to a
microprocessor, for example, an I/O processor or
extra memory.



GM
See General MIDI.



GNU
(Gnu's Not UNIX)  A project sponsored by the Free
Software Foundation that is developing a complete
software environment including operating system
kernel and utilities, editor, compiler and
debugger.  Many consultants and organizations
provide support for GNU software.



go
A command used on a BBS or online service to switch
the user to a particular forum or section.  For
example, typing go macintosh might switch you to a
section that specializes in Macintosh computers or
software.  Like any command language, you have to
know what words to enter.



goal seeking
The ability to calculate a formula backward to
obtain a desired input.  For example, given the
goal gross margin = 50% as well as the range of
possible inputs, goal seeking attempts to obtain
the optimum input.



GOCA
(Graphics Object Content Architecture)  See MO:DCA.



gooey
See GUI.



gooey builder
See GUI builder.



Gopher
A program that searches for file names and
resources on the Internet and presents hierarchical
menus to the user.  As users select options, they
are moved to different Gopher servers on the
Internet.  Where links have been established,
USENET news and other information can be read
directly from Gopher.  See Veronica, Archie and
WAIS.



GOSIP
(Government Open Systems Interconnection Profile) A
U.S. government mandate that after August 15, 1990,
all new network procurements must comply with OSI.
Testing is performed at the NIST, which maintains a
database of OSI-compliant commercial products.
GOSIP also allows TCP/IP protocols to be used.

   Since broad adoption of OSI standards never came
to fruition, GOSIP evolved into POSIT (Profiles for
Open Systems Internetworking Technologies), which
is a set of non-mandatory standards that
acknowledge the widespread use of TCP/IP.



goto
(1) In a high-level programming language, a
statement that directs the computer to go to some
other part of the program.  Low-level language
equivalents are branch and jump.

(2) In dBASE, a command that directs the user to a
specific record in the file.

(3) In word processing, a command that directs the
user to a specific page number.



goto-less programming
Writing a program without using goto instructions,
an important rule in structured programming.  A
goto instruction points to a different part of the
program without a guarantee of returning.  Instead
of using goto's, structures called subroutines or
functions are used, which automatically return to
the next instruction after the calling instruction
when completed.



Gouraud shading
In computer graphics, a technique developed by
Henri Gouraud that computes a shaded surface based
on the color and illumination at the corners of
polygonal facets.



GPCmark
See PLB.



GPF
(1) (General Protection Fault)  An application
program abend in Windows 3.1.  See UAE.

(2) (GUI Programming Facility)  An OS/2 application
generator from GPF Systems, Inc., Moodus, CT.



GPI
(Graphical Programming Interface)  A graphics
language in OS/2 Presentation Manager.  It is a
derivative of the GDDM mainframe interface and
includes Bezier curves.



GPIB
(General Purpose Interface Bus)  An IEEE 488
standard parallel interface used for attaching
sensors and programmable instruments to a computer.
It uses a 24-pin connector.  HP's version is the
HPIB.



GPS
(Global Positioning System)  A series of
continuously-transmitting satellites used for
identifying earth locations.  By triangulation from
three satellites, a hand-held receiving unit can
pinpoint wherever you are on earth.



GPSS
(General Purpose Simulation System)  A programming
language for discrete event simulation, which is
used to build models of operations such as
manufacturing environments, communications systems
and traffic patterns.  Originally developed by IBM
for mainframes, PC versions are available, such as
GPSS/PC by Minuteman Software and GPSS/H by
Wolverine Software.



grabber hand
A pointer in the shape of a hand that is moved by a
mouse to "grab" and relocate objects on screen.



graceful degradation
A system that continues to perform at some reduced
level of performance after one of its components
fails.



graceful exit
The ability to get out of a problem situation in a
program without having to turn the computer off.



grade
The transmission capacity of a line.  It refers to
a range or class of frequencies that it can handle;
for example, telegraph grade, voice grade and
broadband.



gradient
A color spread from light to dark to shade an
object or give it a sense of depth.  It is also
used to create a colorful background.



GRAFCET
(GRAPHe de Commande Etape-Transition - stage
transition command graph)  A PLC specification and
programming language.



GrafPort
See graphics port (2).



grammar checker
Software that checks the grammar of a sentence.  It
can check for and highlight incomplete sentences,
awkward phrases, wordiness and poor grammar.



Grammatik
A popular grammar checking program for DOS,
Windows, Macintosh and UNIX from WordPerfect
Corporation, Orem, Utah.  U.S. Government versions
check for usage according to the Government
Printing Office and other military and civilian
guides.  In 1993, WordPerfect acquired Reference
Software of San Francisco, developers of Grammatik.



grandfather, father, son
A method for storing previous generations of master
file data that are continuously updated.  The son
is the current file, the father is a copy of the
file from the previous cycle, and the grandfather
is a copy of the file from the cycle before that
one.



granularity
The degree of modularity of a system.  The more
granularity (grains or granules), the more
customizable or flexible the system.



graph
A pictorial representation of information.  See
business graphics.



graphic character
A printable symbol that includes digits and
letters.



graphical interface
See GUI.



graphical user interface
See GUI.



graphics
Called computer graphics, it is the creation and
manipulation of picture images in the computer.  It
is defined here as graphics, to keep it next to the
other entries that begin with "graphics."

   A graphics computer system requires a graphics
display screen, a graphics input device (tablet,
mouse, scanner, camera, etc.), a graphics output
device (dot matrix printer, laser printer, plotter,
etc.) and a graphics software package; for example,
a CAD, drawing or paint program.


        Vector Graphics and Raster Graphics
Two methods are used for storing and maintaining
pictures in a computer.  The first method, called
vector graphics (also known as object-oriented
graphics), maintains the image as a series of
points, lines, arcs and other geometric shapes.

   The second method, called raster graphics,
resembles television, where the picture image is
made up of dots.

   Understanding these two methods and how they
intertwine in today's graphics systems is essential
for mastering computer graphics.  When you create
an image on the computer, you may not know which
method is used, but when you try to manipulate that
image, it will become obvious.


        Vector Graphics for CAD and Drawing
Vector graphics is the method employed by CAD
(computer-aided design) and drawing packages.  As
you draw, each line of the image is stored as a
vector (two end points on an x-y matrix).  For
example, a square becomes four vectors, one for
each side.  A circle is turned into dozens or
hundreds of tiny straight lines, the number of
which is determined by the resolution of the
drawing.  The entire image is commonly stored in
the computer as a list of vectors, called a display
list.

  Older CAD systems used vector display screens
that "drew" the image directly from the vectors.
Today, most screens are raster graphics displays
(made up of dots), and the vectors are "rasterized"
into the required dot patterns by hardware or
software.

   Vector graphics is used when you need geometric
knowledge about the object created.  Geometric
shapes keep their integrity: a line can always be
picked, extended or erased.  It never turns into
just a string of dots in the database.

   Vector graphics can be transmitted directly to
x-y plotters that "draw" the images from the list
of vectors.


     Raster Graphics for Imaging and Painting
Raster graphics is the TV-like method that uses
dots to display an image on screen.  Raster
graphics images are created by scanners and cameras
and are also generated by paint packages.  A
picture frame is divided into hundreds of
horizontal rows, with each row containing hundreds
of dots, called pixels.

   Unlike TV, which uses one standard (NTSC) for
the country, there are dozens of raster graphics
standards.  Also, unlike TV, which records and
displays the dots as infinitely variable shades and
colors (analog), computer graphics have a finite
number of shades and colors (digital).

   When you scan an image or paint an object into
the computer, the image is created in a reserved
area of memory called a bitmap, with some number of
bits corresponding to each dot (pixel).  The
simplest monochrome bitmap uses one bit (on/off)
for each dot.  Gray scale bitmaps (monochrome
shades) hold a number for each dot large enough to
hold all the gray levels.  Color bitmaps require
three times as much storage in order to hold the
intensity of red, green and blue.

   The image in the bitmap is continuously
transmitted to the video screen, dot for dot, a
line at a time, over and over again.  Any changes
made to the bitmap are instantly reflected on the
screen.

   Since colors are designated with numbers,
changing red to green is simply searching for the
red number and replacing it with the green number.
Animation is accomplished by continuously copying
new sequences from other areas in memory into the
bitmap, one after the other.

   Raster graphics images may take up more space on
disk than their vector graphics counterpart,
because storage for each pixel is required even if
it's part of the background.  A small object in
vector graphics format will take up only a few
vectors in the display list file.



graphics accelerator
A high-performance display adapter for graphical
user interfaces that has line drawing and pixel
block move functions (bitblt) built into hardware.
For example, in Windows, such boards speed up the
display of fonts and images and provide faster
scrolling.

   Windows applications will display and scroll
faster on a slower PC with a graphics accelerator
than on a faster PC without one.  See Winmark.



graphics adapter
Same as display adapter.



graphics based
The display of text and pictures as graphics
images; typically bitmapped images.  Contrast with
text based.



graphics card
Same as display adapter.



graphics coprocessor
A programmable chip that performs much of the
processing required to display graphics on a video
screen.  It frees the computer from such tasks as
drawing dots, circles, lines and rectangles by
accepting commands to perform these operations and
executing them on the video adapter's coprocessor
rather than the computer's CPU.

   As technology changes, what is true today is not
true tomorrow.  As CPUs get faster, offloading
graphics operations to the coprocessor becomes less
and less important.


            Coprocessor vs Accelerator
A graphics coprocessor is good for CAD work,
especially if not running under Windows.  On the
other hand, a graphics accelerator is good for
Windows and other GUIs, which require a lot of
blitting and text drawing.

   An advantage of a graphics coprocessor is that
it is programmable and can be updated as required
with new graphics operations, whereas the graphics
accelerator is fixed and cannot be changed.  This
is not a disadvantage in Windows, since Windows
requires limited functions to draw the screen.



Graphics Device Interface
See GDI.



graphics engine
(1) Hardware that performs graphics processing
tasks independently of the computer's CPU.  See
graphics accelerator and graphics coprocessor.

(2) Software that accepts commands from an
application and builds images and text that are
directed to the graphics driver and hardware.
Macintosh's QuickDraw and Windows' GDI are
examples.



graphics file
A file that contains only graphics data.  Contrast
with text file and binary file.



graphics formats
There is a wide variety of graphics formats in use
today.  The following list contains most of them.
The formats are in order by extension name under
raster or vector category.  Some formats appear in
both categories because they can hold both raster
and vector images.


      RASTER GRAPHICS FORMATS

AI    Adobe Illustrator
AG4   Access G4 document imaging
ATT   AT&T Group IV
BMP   Windows & OS/2
CAL   CALS Group IV

CIT   Intergraph scanned images
CLP   Windows Clipboard
CMP   Photomatrix G3/G4 scanner format
CPR   Knowledge Access
CUT   Dr. Halo

DBX   DATABEAM
DX    Autotrol document imaging
ED5   EDMICS (U.S. DOD)
EPS   Encapsulated PostScript
FAX   Fax

GED   Arts & Letters
GIF   CompuServe
GP4   CALS Group IV - ITU-TSS Group IV
GX1, GX2  Show Partner
ICA   IBM IOCA (see MO:DCA)

ICO   Windows icon
IFF   Amiga ILBM
IGF   Inset Systems (HiJaak)
IMG   GEM Paint
JPG   JPEG JFIF

KFX   Kofax Group IV
MAC   MacPaint
MIL   Same as GP4 extension
MSP   Microsoft Paint
PCD   PhotoCD
PCL   HP LaserJet

PCX   PC Paintbrush
PIX   Inset Systems (HiJaak)
RAS   Sun
RIA   Alpharel Group IV document imaging
RLE   Various RLE-compressed formats

RNL   GTX Runlength
SBP   IBM StoryBoard
TGA   Targa
TIF   TIFF
WPG   WordPerfect image


      VECTOR GRAPHICS FORMATS

906   Calcomp plotter
CAL   CALS subset of CGM
CGM   Computer Graphics Metafile
CLP   Windows clipboard
DG    Autotrol

DGN   Intergraph drawing format
DRW   Micrografx Designer 2.x, 3.x
DS4   Designer 4.x
DXF   AutoCAD
DWG   AutoCAD
EPS   Encapsulated PostScript

ESI   Esri plot file (GIS mapping)
GCA   IBM GOCA (see MO:DCA)
GEM   GEM proprietary
G4    GTX RasterCAD - scanned images into vectors
        for AutoCAD
IGF   Inset Systems (HiJaak)

MCS   MathCAD
MET   OS/2 metafile
MRK   Informative Graphics markup file
P10   Tektronix plotter (PLOT10)
PCT   Macintosh PICT drawings

PGL   HP plotter
PIC   Variety of picture formats (see PIC)
PIX   Inset Systems (HiJaak)
PLT   HPGL Plot File  (HPGL2 has raster capability)
RLC   Image Systems "CAD Overlay ESP" vector files
        overlaid onto raster images

WMF   Windows Metafile
WPG   WordPerfect graphics





graphics interface
See graphics language and GUI.



graphics language
A high-level language used to create graphics
images.  The language is translated into images by
software or specialized hardware.  See graphics
engine.



graphics mode
A screen display mode that displays graphics.
Contrast with text mode and character mode.



graphics port
(1) A socket on the computer for connecting a
graphics monitor.

(2) Also called GrafPort, it is a Macintosh
graphics structure that defines all the
characteristics of a graphics window.



graphics primitive
An elementary graphics building block, such as a
point, line or arc.  In a solid modeling system, a
cylinder, cube and sphere are examples.



graphics processor
Same as graphics engine.



graphics program
See paint program, drawing program, presentation
graphics, image editing program and image
processing.



graphics tablet
Same as digitizer tablet.



graphics terminal
A terminal or personal computer that displays
graphics.



graPHIGS
See GDDM.



gray scale
A series of shades from white to black.  The more
shades, or levels, the more realistic an image can
be recorded and displayed, especially a scanned
photo.  Scanners differentiate typically from 16 to
256 gray levels.

   Although compression techiques help reduce the
size of graphics files, high-resolution gray scale
requires huge amounts of storage.  At a printer
resolution of 300 dpi, each square inch is made up
of 90,000 pixels.  At 256 levels, it takes one byte
per pixel, or 90,000 bytes per square inch of
image.  See halftone.



greek
To display text in a representative form in which
the actual letters are not discernible, because the
screen resolution isn't high enough to display them
properly.  Desktop publishing programs let you set
which font sizes should be greeked.



green PC
An energy-saving personal computer or peripheral
device.  Green computers, printers and monitors go
into a low-voltage "suspend mode" if not used after
a certain period of time.  Many contemporary CPUs
can run at variable clock rates and can idle at
very low speeds, to save current.  When input is
detected, they revert to full-power.

   The green concept includes using less packaging
materials, recycling toner cartridges, providing a
return location for used batteries, distributing
multi-disk software on a CD-ROM and sending e-mail
rather than paper mail.



grep
(Global Regular Expression and Print)  A UNIX
pattern matching utility that searches for a string
of text and outputs any line that contains the
pattern.



ground
An electrically conductive body, such as the earth,
which maintains a zero potential (not positively or
negatively charged) for connecting to an electrical
circuit.



ground current
The current found in a ground line.  It may be
caused by imbalanced electrical sources; for
example, the ground line in a communications
channel between two computers deriving power
separately.



ground fault
The temporary current in the ground line, caused by
a failing electrical component or interference from
an external electrical source such as a
thunderstorm.



ground loop
An unwanted ground current flowing back and forth
between two devices that are grounded at two or
more points.



ground noise injection
An intentional insertion of unwanted noise by a
power supply into the ground line.



groupware
Software designed for use in a network that serves
a group of users working on a related project.



GroupWise
Formerly WordPerfect Office, it is a groupware
package from Novell that provides e-mail and group
calendar and scheduler for a variety of client
platforms.  It also includes a text-to-speech
converter that lets users listen to their mail
remotely via telephone.



GSOS
(GS Operating System)  A graphical operating system
for the Apple IIGS that also accepts ProDOS
applications.



GT
(Greater Than)  See relational operator.



guard band
A frequency that insulates one signal from another.
In an analog telephone line, the low band is 0-300;
the high band is 3300-4000Hz.



GUI
(Graphical User Interface)  A graphics-based user
interface that incorporates icons, pull-down menus
and a mouse.  The GUI has become the standard way
users interact with a computer.  The three major
GUIs are Windows, Macintosh and Motif.  In a
client/server environment, the GUI resides in the
user's client machine.  See desktop manager, window
manager and Star.  Contrast with CUI.



GUI accelerator
See graphics accelerator.



GUI builder
Visual programming software that lets a user build
a graphical user interface by dragging and dropping
elements from a toolbar onto the screen.  It may be
a stand-alone program or part of an application
development system or client/server development
system.  See application development system and
client/server development system.



GUI painter
Same as GUI builder.



gulp
Some number of bytes!


gutter
In typography, the space between two columns.



GVPN
(Global Virtual Private Network)  A service from
cooperating carriers that provides international
digital communications for multinational companies.



GW-BASIC
(Gee Whiz-BASIC)  A BASIC interpreter that
accompanied MS-DOS in versions prior to 5.0.  See
QBasic.



h
(Hexadecimal)  A symbol that refers to a hex
number.  For example, 09h has a numeric value of 9,
whereas 0Ah has a value of 10.  See hex chart.



h/w
See hardware.



H&J
(Hyphenation and Justification)  The alignment of
the right margin in a document.  Hyphenation breaks
up words that exceed the margin.  Justification
aligns text uniformly at the right margin while
spacing text evenly between both margins.



H.261
An ITU-TSS standard for a video codec that uses
intraframe and interframe compression and transmits
over Px64 ISDN lines.



H.320
An ITU-TSS standard for video teleconferencing.  It
uses the H.261 compression method.



hack
Program source code.  You might hear a phrase like
"nobody has a package to do that, so it must be
done through some sort of hack."  This means
someone has to write some code to solve the
problem.  There's no pre-written package to do it.

   The purist would say that doing a hack means
writing in languages such as assembly language and
C, which are low level and highly detailed.  The
more liberal person would say that writing any
programming language counts as hacking.



hacker
A person who writes programs in assembly language
or in system-level languages, such as C.  Although
it may refer to any programmer, it implies very
tedious "hacking away" at the bits and bytes.

   The term has become widely used for people that
gain illegal entrance into a computer system.  This
use of the term is not appreciated by the vast
majority of honest hackers.  See hack and computer
cracker.



HAL
(1) (Hardware Abstraction Layer)  The translation
layer in Windows NT that resides between the NT
kernel and I/O system and the hardware itself.  Its
purpose is to be able to port NT to another
platform only by designing a new HAL layer for that
platform.  In practice, parts of the kernel may
also have to be changed to optimize NT to a new
platform.

(2) (Heuristic/ALgorithmic)  The computer in the
film "2001," which takes over command of the
spaceship.  Each of the letters in H-A-L
coincidentally precede the letters I-B-M.



half-adder
An elementary electronic circuit in the ALU that
adds one bit to another, deriving a result bit and
a carry bit.



half-duplex
The transmission of data in both directions, but
only one direction at a time.  Two-way radio was
the first to use half-duplex, for example, while
one party spoke, the other party listened.
Contrast with full-duplex.



half height drive
A 5.25" disk drive that takes up half the vertical
space of first-generation drives.  Measuring 1 5/8"
in height, it is the common 5.25" drive in use
today.



halftone
In printing, the simulation of a continuous-tone
image (shaded drawing, photograph) with dots.  All
printing processes, except for Cycolor, print dots.
In photographically-generated halftones, a camera
shoots the image through a halftone screen,
creating smaller dots for lighter areas and larger
dots for darker areas.  Digitally-composed printing
prints only one size of dot.

   In order to simulate varying size halftone dots
in computer printers, dithering is used, which
creates clusters of dots in a "halftone cell."  The
more dots printed in the cell, the darker the gray.
As the screen frequency gets higher (more lines per
inch), there is less room for dots in the cell,
reducing the number of gray levels that can be
generated.

   This tradeoff is a compromise in a 300 dpi
printer, since realistic gray-scale printing
reduces the resolution; for example, the 8x8
halftone cell required to create 64 grays results
in a coarse 38 lpi resolution (300 dpi/8).  In
high-resolution imagesetters, the highest screen
frequencies can be used with ample gray scale.

        cells
    
     ۳۳    This simplistic example uses
lpi   a 2x2 halftone cell
     ߳      allowing only white (no dots),
        black (all four dots) and three
                 interim shades (1, 2 and 3 dots).
      In a 300 dpi printer, this would allow for a
      150 lpi resolution (300/2).  A 4x4 cell would
      provide 16 shades and 75 lpi.

                   Halftone Cell





hammer
In a printer, the mechanism that pushes the
typeface onto the ribbon and paper or pushes the
paper into the ribbon and typeface.



Hamming code
A communications error correction method that
intersperses three check bits at the end of each
four data bits.  At the receiving station, the
check bits are used to detect and correct one-bit
errors automatically.



hand coding
Writing in a programming language.  Hand coding in
assembly language or in a third-generation
language, such as COBOL or C, is the traditional
way programs have been developed.  In contrast,
visual programming tools allow full applications or
parts of an application to be developed without
writing lines of programming code.



hand-held scanner
A scanner that is moved across the image to be
scanned by hand.  Hand-held scanners are small and
less expensive than their desktop counterparts, but
rely on the dexterity of the user to move the unit
across the paper.  Trays are available that keep
the scanner moving in a straight line.  Contrast
with flatbed scanner, sheet-fed scanner and drum
scanner.



handle
(1) In computer graphics, a location on an image
that can be grabbed for reshaping.  It is usually a
tiny square.

(2) A temporary name or number assigned to a file,
font or other object.  For example, an operating
system may assign a sequential number to each file
that it opens as a way of identifying and keeping
track of it.

(3) A nickname used when teleconferencing on a
bulletin board, like a "CB handle" used between
truck drivers.



handler
A software routine that performs a particular task.
For example, upon detection of an error, an error
handler is called to recover from the error
condition.



handoff
Switching a cellular phone transmission from one
cell to another as a mobile user moves into a new
cellular area.  The switch takes place in about a
quarter of a second so that the caller is generally
unaware of it.



handset
The part of the telephone that contains the speaker
and the microphone.



handshaking
Signals transmitted back and forth over a
communications network that establish a valid
connection between two stations.



hang
To have the computer freeze or lock up.  When a
personal computer hangs, there is often no
indication of what caused the problem.  The
computer could have crashed, or it could be
something simple such as the printer running out of
paper.



hanging paragraph
A paragraph in which the first line starts at the
    left margin, but subsequent lines are indented
    as is this paragraph.



hard boot
Same as cold boot.



hard coded
Software that performs a fixed number of tasks or
works with only a fixed number of devices.  For
example, a program could be written to work with
only two types of printers.  Hard coded solutions
to problems are usually the fastest to program and
often run the fastest, but are not as easy to
change.



hard copy
Printed output.  Contrast with soft copy.



hard disk
The primary computer storage medium, which is made
of one or more aluminum or glass platters.  Each
side of the platter is coated with a ferromagnetic
material.  Older hard disks held as little as five
megabytes.  Today's hard disks can hold several
gigabytes.

  Desktop computers use disks from 1.5" to 5" in
diameter.  Minicomputer and mainframe disks range
up to 12" in diameter, but are increasingly
becoming as compact as the desktop drives.

   Hard disks provide fast retrieval because they
rotate constantly at high speed, from 3,000 to over
7,000 rpm.  In laptops however, the disks can be
optionally turned off to preserve battery life
after not being used for a specified period of
time.

   Fixed hard disks are permanently sealed in the
drive.  Removable hard disks are encased in disk
pack or disk cartridge modules that can be moved
between computers with the same kinds of drives.

   Hard disks are usually low-level formatted from
the factory, which records the original sector
identification on them.  See floppy disk, magnetic
disk and format program.

   To understand more about the parameters you have
to enter into your PC when you add a new hard disk,
see hard disk confuration.


              TYPES OF HARD DISKS

                                       Typical
Interface   Encoding  Transfer Rate    Storage
  Type       Method*   (Bytes/sec)    Capacities

  ST506         MFM       625K        5M - 100M
  ST506 RLL     RLL       937K       30M - 200M
  IDE           RLL     .625-2M      40M - 1G
  Enhanced IDE  RLL      10-13M     100M - 8G
  ESDI          RLL       1-3M       80M - 2G
  SCSI-1        RLL       1-5M       20M - 1.5G
  SCSI-2        RLL      1-40M       40M - 9G
  SMD           RLL       1-4M      200M - 2G
  IPI           RLL     10-25M      200M - 3G

*(Most disks use RLL, but the encoding method is
not prescribed by all interfaces.)


              Hard Disk Measurements
Capacity is measured in bytes, and speed is
measured in bytes per second (transfer rate) and in
milliseconds (access time).  Fast personal computer
hard disk access times range from 9 to 14ms; in
larger computers as fast as 1ms.



hard disk configuration
Following are the parameters stored in a PC's CMOS
RAM that describe the configuration of the hard
disks in the system.  SCSI hard disks are usually
not identified in the CMOS RAM.

    TYPE  There are 46 hard disk types, numbered 1
          to 46, that include all the required
          parameters below.  Since they cover
          earlier drives that only go up to 152MB,
          the user-configurable Type 47 is usually
          chosen and the remaining parameters are
          entered manually.

    CYLINDERS  Number of cylinders.
    HEADS      Number of read/write heads.
    WPCOM      Write precomensation starting track.
    LANDING
       ZONE    Cylinder used for parking heads.
    SECTORS    Number of sectors per track.
    CAPACITY   Total capacity derived from above
               parameters:
               (heads X cylinders X sectors X 512)


   For sources of hard disk parameters, see hard
disk references.





hard disk interfaces
See hard disk.



hard disk parameters
See hard disk configuration.



hard disk references
Following are some sources for obtaining hard disk
parameters.  Most new drives have the number of
cylinders, heads and sectors printed directly on
their housing.  Many earlier drives do not.
Listings of hard drive parameters are available
from many bulletin boards as well.

   "Pocket PCRef" is a handy pocket reference that
also contains DOS commands, printer commands and
other useful references and specifications for the
support person.


   "Pocket PCRef" by Thomas Glover & Millie Young
    Sequoia Publishing, Inc., Littleton, CO
    ISBN 0-9622359-7-0

   "Hard Drive Bible"
   Corporate Systems Center, Sunnyvale, CA
   408/737-7312

   "Hard Disk Technical Guide"
   "Hard Disk Encyclopedia" (3 volumes)
   Micro House, Boulder, CO, 800/926-8299

   "DrivePro"
   Hard disk installation and setup utility
   includes hard disk and controller info.
   Micro House, Boulder, CO, 800/926-8299





hard error
(1) A permanent, unrecoverable error such as a disk
read error.  Contrast with soft error.

(2) A group of errors that requires user
intervention and includes disk read errors, disk
not ready (no disk in drive) and printer not ready
(out of paper).



hard hyphen
A hyphen that always prints.  Contrast with soft
hyphen.



hard return
A code entered into a text document by pressing the
return (enter) key.  DOS and OS/2 text files use a
CR/LF (carriage return/line feed) pair, but this is
not standard (WordPerfect uses only an LF).  The
Macintosh uses a CR and UNIX uses an LF.

   A hard return is sometimes represented by a
symbol on screen, such as the < in WordStar, but it
usually remains invisible until revealed in an
expanded screen mode.  Contrast with soft return.



hard sectored
A sector identification technique that uses a
physical mark.  For example, hard sectored floppy
disks have a hole in the disk that marks the
beginning of each sector.  Contrast with soft
sectored.



hard space
A special space character that acts like a letter
or digit, used to prevent multiple-word, proper
names from breaking between lines.



Hardcard
A family of hard disks from Plus Development
Corporation, Milpitas, CA, that house the disk
drive and the controller electronics on an
expansion board that plugs into a PC.  It allows
for a simple installation and does not use up a
drive bay.



hardware
Machinery and equipment (CPU, disks, tapes, modem,
cables, etc.).  In operation, a computer is both
hardware and software.  One is useless without the
other.  The hardware design specifies the commands
it can follow, and the instructions tell it what to
do.  See instruction set.


                    Hardware Is
            "Storage and Transmission"
The more memory and disk storage a computer has,
the more work it can do.  The faster the memory and
disks transmit data and instructions to the CPU,
the faster it gets done.  A hardware requirement is
based on the size of the databases that will be
created and the number of users or applications
that will be served at the same time.  How much?
How fast?


                    Software Is
               "Logic and Language"
Software deals with the details of an ever-changing
business and must process transactions in a logical
fashion.  Languages are used to program the
software.  The "logic and language" involved in
analysis and programming is generally far more
complicated than specifying a storage and
transmission requirement.





hardware failure
A malfunction within the electronic circuits or
electromechanical components (disks, tapes) of a
computer system.  Contrast with software failure.



hardware interface
An architecture used to interconnect two pieces of
equipment.  It includes the design of the plug and
socket, the type, number and purpose of the wires
and the electrical signals that are passed across
them.  See bus, local bus, ISA, VL-bus, RS-232,
PCI, IDE, SCSI and channel.



hardware interrupt
An interrupt caused by some action of a hardware
device, such as the depression of a key or mouse
movement.  See IRQ and interrupt.



hardware key
A copy protection device supplied with software
that plugs into a computer port.  The software
interrogates the key's serial number during
execution to verify its presence.  The hardware key
acts as a pass-through, but tests for a special
code that reads the serial number.



hardware monitor
A device attached to the hardware circuits of a
computer that reads electronic signals directly in
order to analyze system performance.



hardware platforms
Each hardware platform, or CPU family, has a unique
machine language.  All software presented to the
computer for execution must be in the binary coded
machine language of that platform.  The major
hardware platforms in existence today are:

     x86     (Intel 386, 486, Pentium and clones)
     68K     (Motorola 68000, mostly Apple Mac)
    88K     (Motorola 88000, Data General, Encore)
  R MIPS    (SGI, Pyramid, Tandem, NEC, Siemens)
  I SPARC   (Sun and SPARC-licened clones)
  S PA-RISC (Hewlett-Packard workstations, minis)
  C Alpha   (Digital's newest series)
    PowerPC (Apple, IBM, Motorola, newest major)
     VAX     (Digital's mini series, VMS)
     S/370   (IBM 370, 390 MVS and VM mainframes)
     AS/400  (IBM midrange, OS/400, formerly S/38)
     S/36    (old IBM mini, System/36, still used)
     Tandem  (fault tolerant systems, Non-Stop)
     i860    (Stratus fault tolerant systems)
     Unisys  (mainframes)
     CDC     (mainframe and midrange series)
     Wang    (VS midrange series)
     PDP/11  (PDP was Digital's 1st mini series,
               PDP/11 chips still sold)





hardware vendors
Following are the major hardware manufacturers in
the computer industry and their past two year's
performance.  See also software vendors.


     REVENUES FROM MAJOR HARDWARE VENDORS
                         Sales  Profit Employees
Year  Company              (000,000)     (000)

        Computer System Manufacturers

1993 IBM                 62,716  (8,101)  267
1992 IBM                 65,096  (4,965)  308

1993 HP                  20,317   1,177    96
1992 HP                  16,427     549    93

1993 DEC                 14,371    (251)   94
1992 DEC                 14,027  (2,796)  114

1993 Apple                7,977      87    15
1992 Apple                7,087     530    15

1993 Unisys               7,743     565    49
1992 Unisys               8,422    (361)   54

1993 Compaq               7,191     462    11
1992 Compaq               4,132     213    10

1993 Sun                  4,309     157    13
1992 Sun                  3,628     173    13

1993 Tandem               2,031    (518)   10
1992 Tandem               2,058     (41)   11

1993 Dell                 2,014     102     5
1992 Dell                   890      51     3

1993 Gateway              1,732      66     4
1992 Gateway              1,107      70    18

1993 Amdahl               1,681    (580)    6
1992 Amdahl               2,554     (7)     9

1993 AST                  1,412     (54)    5
1992 AST                    951      69     4

1993 Wang                 1,247    (197)    4
1992 Wang                 1,910    (357)   13

1993 Silicon Graphics     1,091      95     4
1992 Silicon Graphics       867    (118)    4

1993 Data General         1,078     (60)    7
1992 Data General         1,127     (63)    7

1993 Intergraph           1,050    (116)   10
1992 Intergraph           1,182       8    10

1993 Cray Research          895      61     5
1992 Cray Research          798     (15)    5


             Drive Manufacturers

1993 Seagate              3,044     195    43
1992 Seagate              2,889      63    43

1993 Conner               2,152   (445)     9
1992 Conner               2,273     121    13

1993 Quantum              1,697      94     2
1992 Quantum              1,128      47    18

1993 Maxtor               1,443      46     9
1992 Maxtor               1,039       7     8

1993 Storage Technology   1,405     (78)   10
1992 Storage Technology   1,521      15    10

1993 Western Digital      1,225     (25)    7
1992 Western Digital        940     (73)    7


         Semiconductor Manufacturers

1993 Motorola            16,983   1,022    120
1992 Motorola            13,341     453    107

1993 Rockwell Int'l.     10,840     562     77
1992 Rockwell Int'l.     10,995  (1,036)    79

1993 Intel                8,782   2,295     30
1992 Intel                5,922   1,067     26

1993 Texas Instruments    8,523     472     59
1992 Texas Instruments    7,470     247     61

1993 Nat'l. Semiconductor 2,014     130     23
1992 Nat'l. Semiconductor 1,726    (120)    27

1993 Advanced Micro Dev.  1,648     229     12
1992 Advanced Micro Dev.  1,531     245     12





hardware virtual memory
Virtual memory management built into a chip.
Although virtual memory can be performed by
software only, it is far more efficient to do it in
hardware.  See DAT and PMMU.



hardwired
(1) Electronic circuitry that is designed to
perform a specific task.  See hard coded.

(2) Devices that are closely or tightly coupled.
For example, a hardwired terminal is directly
connected to a computer without going through a
switched network.



harmonic distortion
In communications, frequencies that are generated
as multiples of the original frequency due to
irregularities in the transmission line.



Harvard Graphics
Popular presentation graphics programs for DOS and
Windows from Software Publishing Corporation,
Mountain View, CA.  Its DOS version was one of the
first business graphics packages to allow for the
creation of columnar and free form text charts.



hash total
A method for ensuring the accuracy of processed
data.  It is a total of several fields of data in a
file, including fields not normally used in
calculations, such as account number.  At various
stages in the processing, the hash total is
recalculated and compared with the original.  If
any data has been lost or changed, a mismatch
signals an error.



hash value
Same as hash total.



HASP
(Houston Automatic Spooling Program)  A mainframe
spooling program that provides task, job and data
management functions.



Hayes compatible
Refers to modems controlled by the Hayes command
language.  See AT command set.



Hayes Smartmodem
A family of intelligent modems for personal
computers from Hayes Microcomputer Products, Inc.,
Atlanta, GA.  Hayes developed the intelligent modem
for first-generation personal computers in 1978,
and its command language (Hayes Standard AT Command
Set) for modem control has become an industry-
standard.

               The Intelligent Modem
An intelligent modem has a command state and an
online state.  In the command state, it accepts
instructions.  In the online state, it dials,
answers, transmits and receives.

   Once connected, it performs the handshaking with
the remote modem, which is similar to the opening
exchange of a telephone call.  The called party
says "hello," the calling party says "hello, this
is..."  After this, the real conversation begins.
If the modem's speaker is on, you can hear the
whistles and tones used in the handshake.

   Once the handshake is completed, you are online
with the other computer, and data can be
transmitted back and forth.

   An important part of the Hayes standard is the
escape sequence, which tells the modem to switch
from online to the command state.  It usually
consists of three plus signs in sequence (+++) with
a Hayes-patented, one-second guard time interval
before and after it, which prevents the modem from
mistaking a random occurrence of the escape
sequence.  The escape sequence and guard time
interval can be programmed in the modem's Status
registers.

   To issue an escape sequence, hold down the shift
key and press + + +.  Pause one second before and
after the sequence.  The modem will return the OK
result code, indicating it is ready to accept
commands.



HC
See high color.



HD
(1) (High Density)  The designation for high-
density diskettes; for example, the 5.25" 1.2MB and
3.5" 1.44MB floppies.  Contrast with DD.

(2) (Hard Disk)  For example, FD/HD refers to a
floppy disk/hard disk device such as a controller.



HDA
(Head Disk Assembly)  The mechanical components of
a disk drive (minus the electronics), which
includes the actuators, access arms, read/write
heads and platters.



HDD
(Hard Disk Drive)  See hard disk.



HDLC
(High-level Data Link Control)  An ISO
communications protocol used in X.25 packet
switching networks.  It provides error correction
at the data link layer.  SDLC, LAP and LAPB are
subsets of HDLC.



HDTV
(High Definition TV)  A high-resolution TV
standard.  Japan was the first to develop HDTV and
currently broadcasts an 1125-line signal picked up
on 36" to 50" TV sets that cost about $10,000.
Both Japan and Europe's HDTV use traditional analog
signalling.

   The U.S. is currently developing a single HDTV
standard from specifications by various proponents,
and the goal is to have it working by the 1996
Olympics.  The technology will be all-digital with
a resolution anywhere from 787 to 1200 lines.  The
refresh rate will be similar to the current NTSC 60
half-frames per second, or perhaps 60 full frames.

   The current TV standard (NTSC) is a 525-line
analog signal.  HDTV will be transmitted on
separate channels concurrently with the NTSC
signals.



HDX
See half-duplex.



head
See read/write head and HDA.



head crash
The physical destruction of a hard disk.
Misalignment or contamination with dust can cause
the read/write head to collide with the disk's
recording surface.  The data is destroyed, and both
the disk platter and head have to be replaced.

   The read/write head touches the surface of a
floppy disk, but on a hard disk, it hovers above
its surface at a distance that is less than the
diameter of a human hair.  It has been said that
the read/write head flying over the disk surface is
like trying to fly a jet plane six inches above the
earth's surface.



head disk assembly
See HDA.



head end
The originating point in a communications system.
In cable TV, the head end is where the cable
company has its satellite dish and TV antenna for
receiving incoming programming.  In online
services, the head end is the service company's
computer system and databases.



head-per-track disk
Same as fixed head disk.



head skew
The offset distance from the start of the previous
track so that the head has time to switch from top
of platter to bottom of platter and be at the start
of the new track.  See cylinder skew.



header
(1) The first record in a disk or tape file.  It
may be used for identification only (name, date of
last update, etc.), or it may describe the
structural layout of the contents, as is common
with many document and database formats.

(2) In a document or report, common text printed at
the top of every page.

(3) In communications, the first part of the
message, which contains controlling data, such as
originating and destination stations, message type
and priority level.

(4) Any caption or description used as a headline.



header label
A record used for file identification that is
recorded at the beginning of the file.



heap
In programming, the common pool of free memory
available to the program.



heartbeat
See MHz.



heat sink
A material that absorbs heat.



helical scan
A recording method used on videotape and digital
audio tape (DAT) that runs the tracks diagonally
from top to bottom in order to increase the storage
capacity.



help
On-screen instruction regarding the use of a
program.  On PCs, pressing F1 is the de facto
standard for getting help.  With graphics-based
interfaces (Mac, Windows, etc.), clicking a "?" or
HELP button gets help.  See context sensitive help.



help compiler
Software that translates text and compiler
instructions into an online help system.



help desk
A source of technical support for hardware or
software.  Help desks are staffed by people that
can either solve the problem directly or forward
the problem to someone else.  Help desk software
provides the means to log in problems and track
them until solved.  It also provides the management
information regarding support activities.



Hercules Graphics
A video display standard for PCs from Hercules
Computer Technology Inc., Berkeley, CA, that
provides monochrome graphics and text with a
resolution of 720x348 pixels.  IBM's first PC
monochrome display did not provide graphics, and
Hercules introduced its display adapter to fill the
void in 1982.  It quickly became a de facto
standard incorporated into all monochrome display
boards.



Hermes
Code name for Microsoft's SMS.  See SMS.



Hertz
The frequency of electrical vibrations (cycles) per
second.  Abbreviated "Hz," one Hz is equal to one
cycle per second.  In 1883, Heinrich Hertz detected
electromagnetic waves.



heterogeneous
Not the same.  Contrast with homogeneous.



heterogeneous environment
Hardware and system software from different
vendors.  Increasingly, organizations use
computers, operating systems and databases from a
variety of vendors.  Contrast with homogeneous
environment.



heuristic
A method of problem solving using exploration and
trial and error methods.  Heuristic program design
provides a framework for solving the problem in
contrast with a fixed set of rules (algorithmic)
that cannot vary.



Hewlett-Packard
See HP.



hex
(HEXadecimal)  Hexadecimal means 16.  The base 16
numbering system is used as a shorthand for
representing binary numbers.  Each half byte (four
bits) is assigned a hex digit as follows:

 Dec Hex Binary   Dec Hex Binary  Dec Hex Binary
  0   0  0000      6   6  0110     10  A  1010
  1   1  0001      7   7  0111     11  B  1011
  2   2  0010      8   8  1000     12  C  1100
  3   3  0011      9   9  1001     13  D  1101
  4   4  0100                      14  E  1110
  5   5  0101                      15  F  1111


   In a hex number, each digit position has a value
16 times greater than the one to its right.  Two
hex digits make up one byte; for example, A7h (h
means hex) is equivalent to decimal 167 (10x16 +
7x1).  See hex chart.

                         A    7
            Ŀ
            4096 256 16   1 
            


   The hex number A000 (pronounced "A thousand") is
equivalent to 40,960 in decimal (4096x10); however,
for PC addressing, hex addresses are interpreted
uniquely (see paragraph).

                    $, h and H
Sometimes a $ is used to represent hex values as
well as upper and lower-case H; for example, $3E0,
3E0h and 3E0H are the same hex number.



hex chart
The following chart is ASCII code in hexadecimal.

ͻ
         Standard ASCII         Extended ASCII  
  The first 32 characters are      (IBM PC)     
        control codes.                          
                                                
00 Null             21 ! 51 Q 80  AE  DC ܺ
01 Start of heading 22 " 52 R 81  AF  DD ݺ
02 Start of text    23 # 53 S 82  B0  DE ޺
03 End of text      24 $ 54 T 83  B1  DF ߺ
04 End of transmit  25 % 55 U 84  B2  E0 
05 Enquiry          26 & 56 V 85  B3  E1 
06 Acknowledge      27 ' 57 W 86  B4  E2 
07 Audible bell     28 ( 58 X 87  B5  E3 
08 Backspace        29 ) 59 Y 88  B6  E4 
09 Horizontal tab   2A * 5A Z 89  B7  E5 
0A Line feed        2B + 5B [ 8A  B8  E6 
0B Vertical tab     2C , 5C \ 8B  B9  E7 
0C Form feed        2D - 5D ] 8C  BA  E8 
0D Carriage return  2E . 5E ^ 8D  BB  E9 
0E Shift out        2F / 5F _ 8E  BC  EA 
0F Shift in         30 0 60 ` 8F  BD  EB 
10 Data link escape 31 1 61 a 90  BE  EC 
11 Device control 1 32 2 62 b 91  BF  ED 
12 Device control 2 33 3 63 c 92  C0  EE 
13 Device control 3 34 4 64 d 93  C1  EF 
14 Device control 4 35 5 65 e 94  C2 ³ F0 
15 Neg. acknowledge 36 6 66 f 95  C3 ó F1 
16 Synchronous idle 37 7 67 g 96  C4 ĳ F2 
17 End trans. block 38 8 68 h 97  C5 ų F3 
18 Cancel           39 9 69 i 98  C6 Ƴ F4 
19 End of medium    3A : 6A j 99  C7 ǳ F5 
1A Substitution     3B ; 6B k 9A  C8 ȳ F6 
1B Escape           3C < 6C l 9B  C9 ɳ F7 
1C Figures shift    3D = 6D m 9C  CA ʳ F8 
1D Group separator  3E > 6E n 9D  CB ˳ F9 
1E Record separator 3F ? 6F o 9E  CC ̳ FA 
1F Unit separator   40 @ 70 p 9F  CD ͳ FB 
20 Blank space      41 A 71 q A0  CE γ FC 
                    42 B 72 r A1  CF ϳ FD 
                    43 C 73 s A2  D0 г FE 
                    44 D 74 t A3  D1 ѳ FF  
                    45 E 75 u A4  D2 ҳ     
                    46 F 76 v A5  D3 ӳ     
                    47 G 77 w A6  D4 Գ     
                    48 H 78 x A7  D5 ճ     
                    49 I 79 y A8  D6 ֳ     
                    4A J 7A z A9  D7 ׳     
                    4B K 7B { AA  D8 س     
                    4C L 7C | AB  D9 ٳ     
                    4D M 7D } AC  DA ڳ     
                    4E N 7E ~ AD  DB ۳     
                    4F O 7F                
                    50 P                    
ͼ




hexadecimal
See hex.



HFS
See hierarchical file system.



HGC
See Hercules Graphics.



hi res
Same as high resolution.



hidden file
A file classification that prevents a file from
being accessed.  It is usually an operating system
file; however, utility programs let users hide
files to prevent unauthorized access.



hierarchical
A structure made up of different levels like a
company organization chart.  The higher levels have
control or precedence over the lower levels.
Hierarchical structures are a one to many
relationship; each item having one or more items
below it.



hierarchical communications
A network controlled by a host computer that is
responsible for managing all connections.  Contrast
with peer-to-peer communications.



hierarchical file system
A file organization method that stores data in a
top-to-bottom organization structure.  All access
to the data starts at the top and proceeds
throughout the levels of the hierarchy.

   In DOS and OS/2, the root directory is the
starting point.  Files can be stored in the root
directory, or directories can be created off the
root that hold files and subdirectories.

   In the Macintosh, the disk window is the
starting point.  Files can be stored in the disk
window, or folders can be created that can hold
files and additional folders.



hierarchical storage management
See HSM.



high availability
Also called RAS (reliability, availability,
serviceability) or fault resilient, it refers to a
multiprocessing system that can quickly recover
from a failure.  It also implies servicing a
component in the system without shutting down the
entire operation.  This is not the same as fault
tolerant, in which redundant components are
designed for continuous processing without skipping
a heartbeat.  See hot fix.



high color
The ability to generate 32,768 colors (15 bits) or
65,536 colors (16-bit).  15-bit color uses five
bits for each red, green and blue pixel.  The 16th
bit may be a color, such as XGA with 5-red, 6-green
and 5-blue, or be an overlay bit that selects
pixels to display over video input.  See true
color.



high definition TV
See HDTV.



high density
Refers to increased storage capacity of bits and/or
tracks per square inch.  See HD.



high DOS memory
Same as UMA.



high-level format
A set of indexes on the disk that the operating
system uses to keep track of the data stored on the
disk.  See format program.



high-level language
A machine-independent programming language, such as
FORTRAN, COBOL, BASIC, Pascal and C.  It lets the
programmer concentrate on the logic of the problem
to be solved rather than the intricacies of the
machine architecture such as is required with low-
level assembly languages.

   There are dramatic differences between high-
level languages.  Look up the terms C, BASIC and
COBOL, and review the sample code.  What is
considered high level depends on the era.  There
were assembly languages thirty years ago that were
easier to understand than C.



high memory
(1) The uppermost end of memory.

(2) In PCs, it refers to either memory in the upper
part of the first megabyte (between 640K and 1M),
called the Upper Memory Area, or UMA, or to memory
above 1M, called extended memory.  It may also
refer to the 64K area between 1024K and 1088K,
called the High Memory Area, or HMA.   Real
straightforward, isn't it?  See PC memory, UMA, HMA
and extended memory.



High Memory Area
See HMA.



High-Performance Computing
A federal initiative to enhance U.S. computing
capability that includes a T3-speed network linking
agencies, private companies and schools to
supercomputer centers.



high resolution
A high-quality image on a display screen or printed
form.  The more dots used per square inch, the
higher the quality.  To display totally realistic
images including the shades of human skin requires
about 1,000x1,000 pixels on a 12" diagonal screen.
Desktop laser printers print respectable text and
graphics at 300 dpi, but typesetting machines print
1,270 and 2,540 dpi.



High Sierra
The first CD-ROM standard named for an area near
Lake Tahoe where it was conceived in 1985.  Later
evolved into the ISO 9660 standard.



high tech
Refers to the latest advancements in computers and
electronics as well as to the social and political
environment and consequences created by such
machines.



highlight
To identify an area on screen in order to select,
move, delete or change it in some manner.



highlight bar
The currently-highlighted menu item.  Choice is
made by moving the bar to the desired item and
pressing enter or clicking the mouse.  The bar is a
different color on color screens or reverse video
on monochrome screens.



HiJaak
A graphics file conversion and screen capture
program for PCs from Inset Systems Inc.,
Brookfield, CT.  It supports a wide variety of
raster and vector graphics formats as well as fax
boards.  It also handles conversion between PC and
Mac formats.



Himalaya
See Tandem.



HIMEM.SYS
An extended memory manager that is included with
DOS and Windows, starting with DOS 5 and Windows
3.0.  It allows programs to cooperatively allocate
extended memory in 286 and higher PCs.  HIMEM.SYS
is an XMS driver.  See XMS and DOS HIMEM.SYS.



hints
Font instructions that make a character uniform and
legible at small point sizes and lower resolutions.
They also ensure that serifs and accents appear in
proper proportion.  When there are not enough
pixels in the print or display image, smaller fonts
can sometimes translate into patterns that are not
recognizable as the characters they represent.
Hints ensure that both sides of an H, for example,
must be of uniform width and that certain elements
of the character cannot be left out.

   Hints are not necessary when printing at 600 dpi
or more, but are required when printing characters
13 points or less at 300 dpi.  When displaying
those same characters on a screen with a 96 dpi or
lower resolution, hints are also needed.



HIPO
(Hierarchy plus Input-Process-Output)  Pronounced
"hy-po."  An IBM flow-charting technique that
provides a graphical method for designing and
documenting programs.



HiPPI
(HIgh Performance Parallel Interface channel)  An
ANSI-standard high-speed communications channel
that uses a 32-bit or 64-bit cable and transmits at
100 or 200 Mbytes/sec.  It is used as a point-to-
point supercomputer channel or, with a crosspoint
switch, as a high-speed LAN.



histogram
A chart displaying horizontal or vertical bars.
The length of the bars are in proportion to the
values of the data items they represent.



history
A user's input and keystrokes entered within the
current session.  A history feature keeps track of
user commands and/or retrieved items so that they
can be quickly reused or reviewed.  See DOS Doskey.



HLLAPI
(High Level Language Application Program Interface)
An IBM programming interface that allows a PC
application to communicate with a mainframe
application.  The hardware hookup is handled via
normal micro to mainframe 3270 emulation.  An
extended version of the interface (EHLLAPI) has
also been defined.



HLS
(Hue Lightness Saturation)  A variation of the HSV
color model.  The H and L in HLS correspond to the
H and V in the HSV model.  However, the saturation
component is measured differently; for example,
pure green in HLS is 120,1,0.5 compared to an HSV
of 120,1,1.  See HSV.



HMA
(High Memory Area)  In PCs, the first 64K of
extended memory from 1024K to 1088K, which can be
accessed by DOS.  It is managed by the HIMEM.SYS
driver.  It was discovered by accident that this
area could be used by DOS, even though it was
beyond the traditional one-megabyte barrier.



HMOS
(High-density MOS)  A chip with a high density of
NMOS transistors.



Hobbit
A microprocessor from AT&T used in a variety of
portable devices.



hog
A program that uses an excessive amount of computer
resources, such as memory or disk, or takes a long
time to execute.



Hollerith machine
The first automatic data processing system.  It was
used to count the 1890 U.S. census.  Developed by
Herman Hollerith, a statistician who had worked for
the Census Bureau, the system used a hand punch to
record the data in dollar-bill-sized punched cards
and a tabulating machine to count them.

   It was estimated that, with manual methods, the
1890 census wouldn't be completed until after 1900.
With Hollerith's machines, it took two years and
saved five million dollars.

   Hollerith formed the Tabulating Machine Company
and sold his machines throughout the world for a
variety of accounting functions.  In 1911, his
company was merged into the company that was later
renamed IBM.



home brew
Products that are developed at home by hobbyists.



home button
An icon that represents the beginning of a file or
a set of basic or starting functions.



home computer
In the 1980s, a home computer was the lowest-priced
computer of the time, such as an Apple II,
Commodore 64 or 128, Tandy Color Computer or Atari
ST.  Today, the term generally refers to a PC or
Mac.



home key
A keyboard key used to move the cursor to the top
of the screen or file or to the previous word or
beginning of line.  See home button.



home run
A single wire that begins at a central distribution
point (hub, PBX, etc.) and runs to its destination
(workstation, telephone, etc.) without connecting
to anything else.



homogeneous
The same.  Contrast with heterogeneous.



homogeneous environment
Hardware and system software from one vendor; for
example, an all-IBM or all-Digital shop.  Contrast
with heterogeneous environment.



Honeywell
See Bull HN.



hook
In programming, instructions that provide
breakpoints for future expansion.  Hooks may be
changed to call some outside routine or function or
may be places where additional processing is added.



hooked vector
A trapped interrupt in a PC.  The pointer for a
particular interrupt in the interrupt vector table
has been modified to jump to a new routine to
service that interrupt.



hookemware
Free software that contains a limited number of
features designed to entice the user into
purchasing the more comprehensive version.



hop count
The number of gateways and routers in a
transmission path.  Each hop slows down
transmission since the gateway or router must
analyze or convert the packet of data before
forwarding it to its destination.



hopper
A tray, or chute, that accepts input to a
mechanical device, such as a disk duplicator.



horizontal market software
Software packages, such as word processors and
spreadsheets, that are used in all industries
(banking, insurance, etc.).  Such products are also
called productivity software.  Contrast with
vertical market software.



horizontal resolution
The number of elements, or dots, on a horizontal
line (columns in a matrix).  Contrast with vertical
resolution.



horizontal scaling
In multiprocessing, adding more computer systems to
the environment.  Contrast with vertical scaling.



horizontal scan frequency
The number of lines illuminated on a video screen
in one second.  For example, a resolution of 400
lines refreshed 60 times per second requires a scan
rate of 24KHz plus overhead (time to bring the beam
back to the beginning of the next line).  Same as
horizontal sync frequency in TV.  Contrast with
vertical scan frequency.



horizontal software
See horizontal market software.



horizontal sync
See horizontal scan frequency.



HOS
(Higher Order Software)  A design and documentation
technique used to break down an information system
into a set of functions that are mathematically
correct and error free.  It uses a rigid set of
rules for the decomposition of the total system
into its elementary components.  The resulting
specifications are complete enough to have machine
language programs generated directly from them.



host
The main computer in a distributed computing
environment.  It typically refers to a large
timesharing computer or a central computer that
controls a network.



host adapter
Also called a controller, it is a device that
connects one or more peripheral units to a
computer.  It is typically an expansion card that
plugs into the bus.  IDE drives and SCSI
peripherals are examples of peripheral interfaces
that call their controllers host adapters.



host based
A communications system that is controlled by a
large, central computer system.



host mode
A communications mode that allows a computer to
answer an incoming telephone call and receive data
without human assistance.



hot fix
To repair a component in the middle of its
operation.  For example, some SCSI drives can
automatically move the data in sectors that are
becoming hard to read to spare sectors without even
the SCSI host adapter being aware of it, let alone
the operating system or the user.  See hot swap.



hot link
A predefined connection between programs so that
when information in one database or file is
changed, related information in other databases and
files are also updated.  See hypertext, compound
document and OLE.



hot potato routing
In communications, rerouting a message as soon as
it arrives.



hot spot
The exact location of the screen cursor that points
to and affects the screen object when the mouse is
clicked.  It is typically the tip of an arrow or
finger pointer or the crosspoint of an X-shaped
pointer, but can be elsewhere with other cursor
designs.



hot swap
To pull out a component from a system and plug in a
new one without turning the power off.  Redundant
systems can be designed to swap drives, circuit
boards, power supplies, virtually anything that is
duplexed within the computer.  PCMCIA cards in
laptop computers can be hot swapped while the
computer is running.  See hot fix.



hot topics
Following is a synopsis of the latest trends in the
computer industry.


                    Multimedia
Multimedia means a lot of different things to
people, but the bottom line is that the integration
of pictures, voice and video with traditional text
is a major force that will bring changes in
hardware and software for years to come.
Multimedia pushes the hardware to extremes.  Typing
a page of text uses three to five thousand bytes of
storage, but scanning that same page and treating
it as an image can take 50 thousand bytes or more.

   Online help in the form of video clips promises
improved productivity, but a few minutes of video
can eat up an entire hard disk.  Audio messages,
while not as storage intensive, require
considerably more capacity than text.  Thus,
multimedia not only impacts the production of CD-
ROM drives, sound cards, speakers and a whole
variety of imaging and video software, but larger
storage capacities and faster networks must also
meet the demand of ever-increasing multimedia
files.

   While CD-ROMs hold 660 megabytes of data, they
are as slow as floppy disks.  We are already seeing
CD-ROMs with huge databases crammed to the limit.
New standards for increased capacity, faster
speeds, network servers, carousel and juke box
drives are options.  But, ideally the single user
would like a 10 gigabyte hard disk to store a dozen
CD-ROMs on it and run them at high speed.  The
drive should also cost $1000.  At current prices of
about 50 cents per megabyte, it won't be too long
before it will.  See lessons multimedia and
realtime video.



                      Objects
Just like plugging an expansion board into an
expansion slot, objects and object-oriented
programming are designed to make software
components equally interchangeable.  The ability to
plug together software routines that can be
purchased from a wide variety of sources and have
them work together holds enormous promise for
software developers and users.

   Standardizing an object format that will run
across all platforms is perhaps as impossible as
standardizing on any other area in computing.
Therefore, it remains to be seen how bumpy the road
to success will be in this area.  See objects and
object-oriented programming.



           The Information Superhighway
Due to the Clinton/Gore administration's interest
in the information superhighway, more books have
been written about the Internet than ever before.
However, the Internet was never intended to be the
sum total of an information superhighway.  It may
be a major provider of information on the highway,
but it is not the delivery mechanism, certainly not
today at least.

   The superhighway concept is meant to modernize
the telecommunications infrastructure in the U.S.
so that everyone has access to information and
educational materials no matter what their station
in life.  The delivery of such a service is
realistically in the hands of the telephone and
cable companies, because they are already wired
into everyone's home and are capable of delivering
multimedia content.  This requires changes in
federal regulations for effective implementation.

   Entertainment may be more of a driving force
than information and education as video-on-demand
and all variety of interactive services converge
into this new frontier of online delivery.  With
deals being made daily by cable and telephone
companies, video providers and TV networks, major
companies are positioning themselves for what they
believe to be a huge consumer market.

   One thing is certain, some pretty large
investments are going to go down the tubes until it
all settles down and mom, pop and the kids decide
what they do and don't want, what they will and
won't watch and, more to the point, what they will
and won't pay for.  See information superhighway,
Internet, Oracle Media Server and Tiger.



           Client/Server and Downsizing
Switching applications from minicomputer and
mainframes to LANs of desktop computers has been
the trend for the past six or seven years.  Minis
and mainframes may still be used as servers to the
desktop machines, but dumb terminals to a single,
central computer architecture is no longer in vogue
for implementing most new information systems.

   Many organizations are migrating to
client/server LANs in stages, placing new
information systems on the LANs and planning to
convert legacy systems as necessary.  The primary
reasons for downsizing are cost/performance,
increasingly favoring LANs, the variety of
applications available for desktop machines and the
wide variety of sources for hardware.  However,
organizations have a huge investment in legacy
systems, and downsizing must be carefully analyzed.

   As desktop hardware becomes faster and as
desktop operating systems and LAN networking
software become more stable, providing the
industrial strength required to perform online
transaction processing 24 hours a day, more and
more legacy systems will be converted to
client/server architecture.

   Other factors necessitate the conversion as
well.  Many legacy systems were programmed years
ago with the original programmers either long gone
or nearing retirement.  Old systems can be
extremely difficult to maintain, and outsourcing
the programming to keep the systems current is
expensive.  Many older information systems were
developed to handle a two-digit year and assume a
'19' prefix.  When we reach the year 2000, our
software has to handle a four-digit year.  After a
while, it's just time for a change.

   Just to throw a fly in the ointment, there is
also a great possibility that by the year 2010 or
2015, there will be a push to go back to the
central mainframe concept.  The mainframe may have
1,000 processors in it, but reigning in all the
complexity from the desktop back into the glass-
enclosed datacenter may not be such a bad idea.

   With transmission capacities as high as they
will be tomorrow, a dumb terminal back to an
intelligent, centralized switching system may
provide better network management and system
administration than the client/server architecture
that's so hot right now and growing increasingly
more complex every day.

   The universe works in cycles.



                    Networking
Just as most organizations have gone through round
one in networking their desktop computers together
for information sharing and electronic mail, the
demands of client/server applications, multimedia
and realtime video are forcing them to plan round
two.

   Passing image and video files, especially
realtime video, over a network places greater
demands on network throughput.  As networks expand,
monitoring and controlling their routine operation
become more difficult.  Tying together
heterogeneous networks from different departments,
subsidiaries and divisions is a daunting task for
network administrators and IS managers.

   The network has becoming the information
backbone of the entire organization and will
continue to be the most complex of all operations
to manage.  See enterprise networking and ATM.



                   The PowerPCs
The PowerPC chips from Motorola offer the first
major threat to the x86 architecture, which has
been the mainstay of the PC industry.  Although
Intel has done a commendable job enhancing the x86
line, with Pentium CPUs over a hundred times faster
than the first 8088 chip, the x86 architecture
suffers from an ancestry that evolved from a
calculator chip.

   The joint venture of IBM, Apple and Motorola has
produced RISC-based PowerPC chips that have been
designed in the 1990s for the 21st century.  The
first implementation of the PowerPC is the Power
Macintosh line from Apple that runs the Macintosh
operating system with considerable performance
increases.  The PowerMacs also run DOS and Windows
applications via emulation at respectable
performance levels with upcoming PowerMac models
expected to provide dazzling speed.

   IBM and other PC manufacturers will also shortly
be offering PowerPC-based PCs that will run native
PowerPC applications and emulate DOS and Windows
applications.  A variety of operating systems will
be offered on these models, including IBM's OS/2
and Workplace OS and Microsoft's Windows NT.

   With any new generation of equipment as dramatic
as the PowerPC, many will take a wait and see
attitude.  Nevertheless, the PowerPC has caused
Intel to announce future CPU designs earlier than
it might have, and the competition between Intel
and Motorola is definitely heating up.  See PowerPC
and PowerMac.


                End of hot topics.






hotkey
The key or key combination that causes some
function to occur in the computer, no matter what
else is currently running.  It is commonly used to
activate a memory resident (TSR) program.



housekeeping
A set of instructions that are executed at the
beginning of a program.  It sets all counters and
flags to their starting values and generally
readies the program for execution.



how to buy a new computer
See how to select a personal computer.



how to buy a used computer
See used computers and computer exchange.



how to choose an accounting package
The following article was written by and is
reprinted with permission of Mr. Frank Arbaugh, a
consultant in accounting systems for small business
in the greater Philadelphia area.

              Frank Arbaugh
              F. A. RESOURCES
              213 Pinecrest Lane
              Lansdale, PA 19446
              215/361-2341


         HOW TO CHOOSE ACCOUNTING SOFTWARE
The right accounting package should (1) give you
the information you need for management, tax
estimation and tax preparation, and (2) enable you
to easily input the figures.

   Management needs are usually balance sheets and
P & L statements.  There also may be a need for
cash flow analysis, receivable/payable management
and identifying profit or loss on a job by job
basis (job costing).

   Tax estimation/preparation functions should
enable you to prepare quarterly state and federal
estimated tax returns.  The system should also give
you annual figures that can easily be used for tax
preparation, both state and federal.  Much of this
will depend on you and your accountant's ability to
set up your chart of accounts properly.  Sometimes
there are conflicts between management and tax
needs when setting up the accounts, but they can be
resolved in time.

   Most accounting software has provisions for
recurring entries, math calculators (debits must
equal credits), and the ability to add accounts
during data entry.  The issue of whether you
account on a cash or accrual basis must be
analyzed.  Most packages do not support your
invoicing if you are on a cash basis.  Each package
has its good and bad points in these areas.

   Job costing is not a traditional accounting
function.  It is an additional entry that keeps
track of the costs involved with a certain activity
or job.  Some accounting packages support it
directly while others can be adapted for it.

   Accounting software imposes certain demands on
you or your bookkeeper.  If you have a manual
system, you learned which journals to keep what
records in, and perhaps at the end of the month you
posted them all to the general ledger.  There may
not have been much thought about the impact of each
transaction on management information or even tax
strategies.  But electronic accounting forces you
to deal with these issues from the start, when you
set up your chart of accounts, and on a daily basis
when you enter and disburse each transaction.

   You now will be generating the financial
statements and reports, and the overall structure
and disbursements will determine the usefulness and
validity of these reports and statements.  The
bottom line is that management must understand and
participate in the setup and daily use of these
systems to be sure that they serve the needs
defined above.

   Bookkeeping, tax strategies through your
accountant as well as management needs must be
closely coordinated for best results.  Perhaps
people who have never communicated before will get
to know each other!  The good part is that no tax
deductions should slip away because of a lack of
documentation.

   How do you choose the right package?  You should
have identified your needs through discussions with
your accountant and bookkeeper, which may be one in
the same.  However, you are playing Russian
roulette if you expect them to make this selection
for you.  You will lose a golden learning
opportunity if you don't take this responsibility
yourself or share it equally.

   Prices for accounting software packages start at
$30 and range upwards to $10,000 and more, but
price is not a measure of how well any system will
meet your needs.  Even the least expensive one
takes effort to install and set up properly.  If
the software costs $300 or more, it might have more
features than a small business will ever need.

   Installing an accounting package is an on-going
process.  Don't expect to get everything right or
the way you want it the first time.  It is also not
recommended that you drastically change your chart
of accounts midyear, since the validity and
usefulness of the figures are greatly determined by
consistency.  Once you make a decision on what
account to disperse a particular expense to, you
should not change that during the same accounting
period.

   Nobody can make a specific recommendation
without looking at your needs.  However, I have
personally had considerable experience with the
following accounting packages.  For individuals, I
have found Moneycounts and Quicken to offer the
most features for the cost.  For small business,
the business version of Moneycounts, Quickbooks and
One Write Plus should be considered.  If you have
more than one person working on your books,
inventory, purchasing, etc., consider Pacioli 2000.
It is multiuser and network ready right out of the
box.

   There are dozens of good accounting packages on
the market.  All of them have their strengths and
weaknesses.  To be truly proficient in any of them,
you must use one for at least a year.

   Sales people and consultants can help but keep
in mind their perspectives and motivations.
Remember that no matter how expert somebody is,
that person can only know a handful of software
packages well.  No one individual can know them
all; there are too many, and each one is complex
with nuances and subtleties that take time to
master.

  Talk to other people who have similar accounting
needs.  Try and understand the similarities and
differences between their business and yours.  How
long have they been using the package and has
enough time transpired to point up problems?  They
have to go through at least one fiscal year to know
what's going on.

   Make the effort up front.  You don't want to
switch accounting packages year every year, since
this may invalidate annual comparison of figures.
Computer magazines have in-depth reviews of
accounting software, but keep in mind that reviews
are written by editors, not long-time users of the
software.  They view products generically, not from
your perspective.

   If your invoicing or inventory needs are unique,
you might consider custom software or a combination
of packaged and custom software. This is an
expensive process but can be very rewarding, since
you will get the system that you truly need.

   Even if you don't require customized software,
if you obtain the assistance of a consultant that
will help you through the installation of an
existing software package, you will have less
frustration, and you will reach your goals more
quickly.

   Good luck!





how to compress files
See Pkzip abc's.



how to convert files
There are dozens of file formats for word
processing documents, database files, graphics,
spreadsheets and so on.  If a file was created in
one application and you want to use it in another,
you can either import the file or use a conversion
program.


               Converting Text Files
Most word processing programs provide an Import
function, which provides built-in conversion for
various document formats.  Simply select Import
from the File or Import menu and choose the
document type you want to input.

   If your word processor does not import the
document type you need, you can usually use the
ASCII file format as a common denominator; however,
you will need the word processing program that
created the original document.

   If both word processing programs import and
export ASCII files, convert your original document
into an ASCII file using the source word processor.
Look for Export in the File or Export menu.  Select
ASCII file or Text File.  After creating an ASCII
file of the source document, use the destination
word processor and import that file using the
Import option, again for an ASCII file or Text
File.  Note that all format commands (bold,
italics, headers, footers, etc.) will generally be
lost between conversion.


             Converting Database Files
Most database programs provide an Import function,
which provides built-in conversion for various
record formats.  Simply select Import from the File
or Import menu and choose the database type you
want to input.

   If your database program does not import the
file type you need, you can usually use the ASCII
file format as a common denominator; however, you
will need the database program that created the
original file.

   If both database programs import and export
ASCII files, convert your original file into an
ASCII file using the source database program.  Look
for Export in the File or Export menu.  Select
ASCII file or Text File.  There are generally two
types of ASCII files that can be created: comma
delimited and SDF.

   Comma delimited separates each field with a
comma and puts quotes around text fields, for
example:

  "Harry Bacon","123 Main","El Paso","TX"
  "Mary Katz",4 W. 3rd St.","New York","NY"


   The SDF, or standard data format, creates
contiguous fixed fields:

   Harry Bacon     123 Main         El Paso     TX
   Mary Katz       4 W. 3rd St.     New York    NY


   Each field in a comma delimited or SDF format
follows in the order of its original placement.  In
your destination database program, create a new
database file with the same structure as the
original, using the same order as the original.
Then import the ASCII file into that structure.
You can always modify the structure after you have
imported the data into it.


          Converting Images and Drawings
Most paint, drawing, word processing, desktop
publishing and presentation graphics programs
provide an Import function, which provides built-in
conversion for various image and drawing formats.
Simply select Import from the File or Import menu
and choose the graphics file type you want to
input.

   If your program does not import the file type
you need, you can convert one image or drawing
format into another using an independent graphics
conversion program, such as Inset System's popular
HiJaak.

   Note that image formats, or raster graphics
formats, such as PCX, BMP, TIFF, GIF, etc. cannot
be converted into drawing formats, or vector
graphics formats, such as WMF, DXF, DRW, CGM, etc.,
but vector formats can be turned into raster images
(for more on rasters and vectors, see graphics and
graphics formats).

   Windows programs can usually import BMP and WMF
files, which are the standard Windows graphics
formats.  BMP is a raster graphics format (image)
and WMF is a vector graphics format (drawing).





how to copy a file
To learn how to copy a disk file using DOS
commands, see DOS Copy.



how to donate old equipment
See National Cristina Foundation.



how to download a file
See download.



how to find a file
In a PC, as of Windows 3.1 and DOS 6, there is no
built-in way to locate a file by name no matter
what directory it is stored in.  Since it is easy
to forget the name of the directory you saved a
file in, or the file may have been stored in the
wrong directory unintentionally, a "file find"
utility is very useful.

   This type of program is included with file
managers such as PC Tools and Norton Utilities.
Although you can use wild cards to broaden the
search, you still have to know the spelling of the
file you are looking for.  The file find program
searches all directories for matching files.



how to find a good computer book
Good computer books are worth their weight in gold,
because the online help in most applications leaves
a lot to be desired.  Unfortunately, while millions
are spent programming software, considerably less
money is allocated to documenting it.  Worse yet,
the documentation is usually last minute, rushed
and never read by anyone but the unfortunate user
of the software.  That's why having auxiliary
documentation in the form of books is extremely
helpful.

   How to find a good book is simple.  Get two or
three on the same subject.  Today, software
applications are often the culmination of decades
worth of functions and features that includes
everything everyone ever wanted in the program.  It
is rare to find a single author equally competent
in all areas of the program, and you won't know
that when you browse the book in the bookstore,
only when you're stuck later on.  If you have more
than one book, your chances are greater that your
question will be answered.

   In lieu of direct technical support from the
software vendor or from your organization's help
desk or IS department, several books on the subject
is your best bet.



how to format a disk
To learn how to format a diskette or a hard disk
using DOS commands, see DOS Format.



how to import a file
See how to transfer a file.



how to install a 2nd IDE drive
See IDE.



how to install a program
Most current-day install programs work as indicated
below.  If they do not, follow the instructions
that came with the install program.

   Any professionally-designed install program
should install your application easily.  All you
should have to do is just insert the next disk when
prompted.

   Following are instructions for installing DOS,
Windows and Macintosh applications.


                        DOS
To install a DOS application, do the following:

   1. Insert floppy disk #1 into the appropriate
      floppy disk drive.

   2. At the DOS prompt,

              type a:install or b:install.

   3. If the install program is written by
      amateurs, you will have to default to the
      floppy drive first and then load the
      install program; for example, if you're
      using the B: drive, you would type:

                b:
                install

   4. The install program should prompt you through
      all the necessary steps, including when to
      insert the next floppy (if applicable).  It
      will create a subdirectory for you, also
      allowing you to choose your own name for it.

      The install program may have to make changes
      in your AUTOEXEC.BAT and CONFIG.SYS files.
      If asked whether the install program should
      make certain changes now or let you do it
      later, let the program do it.

      After installation, you are usually returned
      to the DOS prompt.  You load your DOS program
      by typing in the name of an .EXE, .COM or
      .BAT file.  The installation manual will tell
      you what the name is.

      Note that you can generally run a DOS install
      program from within Windows by loading it
      from the Run command in the File menu.  Type
      a:install or b:install on the command line.


                      WINDOWS
To install a Windows application, do the following:

   1. Insert floppy disk #1 into the appropriate
      floppy disk drive.

   2. At Program Manager, select Run from the File
      menu and 

              type a:setup or b:setup

           or

              type a:install or b:install


   3. The install program should prompt you through
      all the necessary steps, including when to
      insert the next floppy (if applicable).  It
      will create a subdirectory for you, also
      allowing you to choose your own name for it.

      After installation, you are returned to
      Program Manager.  There is generally a new
      group window on screen that contains the icon
      of the new application.  Click on that icon
      to launch the program.


                     MACINTOSH
To install a Macintosh application, do the
following:

   1. Insert floppy disk #1 into the floppy disk
      drive.

   2. When the floppy disk window appears, there is
      usually an icon that says "Double Click on
      Me."  Double click on the icon to start the
      install.

   3. The install program should prompt you through
      all the necessary steps, including when to
      insert the next floppy (if applicable).  It
      will create a new folder for you, also
      allowing you to choose your own name for it.





how to learn more
Look up "Lessons" in this database for term lists
based on topics within the industry.  Use the term
lists as a systematic way to learn about a
particular subject by setting a bookmark in the
list, hypertexting to each term (with the mouse)
and coming back to the bookmark.



how to make backups
Backups are copies of documents, spreadsheets,
databases and images on the hard disk that have
been placed onto an external storage medium such as
floppy disk or tape.  Backups should be made
routinely because the hard disk can self destruct
(see head crash).  There is definitely more
paranoia about this than the number of incidents,
but they do happen, so it is wise to make backups.


         Using a Copy Command or Function
There are two ways to back up files onto external
storage media.  The first is to copy the individual
files using a copy command or function.  In DOS,
you would use the Copy or Xcopy commands.  In
Windows or the Mac, you would dragg the file icon
with a mouse from the graphical representation of
the hard disk to that of the desired floppy.
Copying files works best for copying a small number
of files or if you are sure that the all the
required files fit on the target storage medium.
To fit more files onto a single diskette, you can
compress files before you copy.  To learn how to do
this, look up Pkzip abc's.


         Using a Backup Command or Utility
The second way to back up files is to use a backup
program or backup command.  The advantage of this
method is that you can copy any number of files as
long as you have enough blank floppy disks.  When a
floppy disk is full and only a part of the file has
been copied, the backup program copies the
remaining part of the file to the next disk.  When
restoring files, the backup program deals with
these overlapping files, which normal copy commands
cannot.

   In addition, backup programs support tape backup
units, something that copy commands do not
generally do.  They also compress files
automatically to save space.

   DOS provides its own Backup and Restore
commands, but if you use Backup to back up your
files onto floppies and then switch to a different
computer, the Restore command from a different DOS
version won't restore your files.  As of DOS 6,
separate backup utilities are included with DOS
(see DOS MSbackup) that make the job easier.
However, third-party backup utilities provide more
versatility than both the commands and utilities
included with DOS.

   Another advantage of using a backup utility is
that you can make a full copy of your entire disk
directory, not just your data files, but the
software too.  This is especially helpful as you
add more and more applications to your system.  If
your disk crashed, reinstalling everything would
take quite some time.  However this works best when
you use high-capacity tapes or optical disks for
backup.  Routine copying onto multiple floppies is
a nuisance.

   Remember, it's your data (documents,
spreadsheets, databases, images, etc.) that is most
critical.  As long as it is still popular, you can
always obtain another copy of the software.  But
you cannot purchase copies of your data from
anybody.  See backup types.



how to protect a floppy
See file protection.



how to select a personal computer
The most important thing in selecting a personal
computer is that you obtain the performance and
storage capacity from your system that you need as
well as the technical support from your dealer that
you require.  The primary decision criteria are:

        1. PC versus Mac
        2. DOS versus Windows
        3. Desktop versus Laptop
        4. Where to buy


                   PC VERSUS MAC
The first decision is whether to purchase a PC or a
Macintosh.  It is, afterall, a PC and Mac personal
computer world.  Although Apple has only about 12%
of the business, it is also only one company.  The
rest of the personal computer market is made up of
countless PC vendors from thousands of mom and pop
shops to the big companies such as Compaq, IBM,
Dell and Gateway.  Thus, Apple continues to hold
its own in a largely PC world.

   The advantage of the Mac is that it is easier to
use compared to Windows and DOS machines.  The
Macintosh infrastructure is much more solid.
Applications for both the PC and the Mac are
increasingly becoming more feature laden and more
complicated as a result.  With the Mac, you can
spend more time learning your application and less
time configuring your computer.

   It is also considerably easier to upgrade a Mac
than a PC.  The Mac has always been plug and play.
Adding the second or third additional peripheral to
a PC can be a nightmare.  PCs will become easier to
upgrade when the Intel/Microsoft Plug and Play
standard becomes widely used; however, universal
adoption of that standard plus ironing out all the
bugs in it may not occur until 1996 or 1997.  To
implement it, you will need to run Windows 95 and
have an entirely new machine with all hardware Plug
and Play enabled.

   The disadvantage of the Mac is compatibility.
If your organization supports PCs and Macs, support
personnel have most likely determined the
appropriate applications and utilities that make
file transfer between both platforms
straightforward.  There may always be some effort
required to transfer your DOS/Windows file to the
Mac and vice versa, but experienced personnel will
show you the best ways to make the transition.  If
this support is not available, switching between
PCs and Macs can be bothersome and in some cases
not feasible.

   There are also decidedly more applications for
Windows than the Mac.  If an application will be
developed for both platforms, chances are it will
be developed for Windows first, unless it's from a
Mac-oriented developer.  However, with the Power
Macintoshes, users can run Mac, DOS and Windows
applications on the same machine.  The PowerMac
models that are expected in 1995 and 1996 should
run Windows applications as fast as a 486/66 or
Pentium.


                DOS VERSUS WINDOWS
If you've settled on a PC, then the type of
applications you will run determines the system
size.  If you are going to run only a vertical
market application (doctor, dentist, retailer,
etc.) that is DOS based, you can get by with a very
minimal PC configuration (see requirements below).

   On the other hand, if you are running Windows,
you need a fast and large machine.  Windows
applications can take enormous amounts of disk
space, as much as 20 and 30 or more megabytes per
application.  You may not be entering a lot of
data, but you could use up 100 megabytes of disk
just by installing four or five Windows
applications.  In addition, if you want to keep a
half dozen or more applications open at the same
time, you need gobs of memory (RAM).

   Future Windows applications will be even more
demanding than current ones.  Purchase the fastest
machine you can afford.


           Minimum Requirements for DOS

            CPU:     386/33
         Memory:     1MB
           Disk:     100MB
            Bus:     ISA
        Display:     VGA
     Multimedia:     Sound board,
                     CD-ROM and
                     speakers


         Minimum Requirements for Windows

           Word processing,    CAD, imaging,
           database,           desktop publishing
           spreadsheets
    CPU:        486/25        Pentium/90
    Memory:     4MB           16MB
    Disk:       300MB         500MB
    Bus:        ISA + VESA or PCI bus
    Display:    Accelerated VGA
    Multimedia:      Sound board,
                     CD-ROM and
                     speakers

   Regarding Windows requirements, you can always
get by with a slower machine.  It's all a matter of
your frustration waiting for something to happen.
Your experience level has nothing to do with the
power of the machine you should use.  You will get
used to the fastest PC on the market in about 10
minutes.  Then, if you go to a slower machine, you
will really notice the difference.


               DESKTOP VERSUS LAPTOP
If you have a requirement for a computer in more
than one location, a laptop can be an economical
alternative.  It can function as a desktop computer
by attaching a full-size monitor and keyboard.

   The caveat with laptops is that they are not as
expandable as desktop machines.  On desktop PCs,
peripherals are mostly interchangeable.  If you
need more hard disk, you can add another or swap
your current one for a larger one.  On laptops, the
hard disk may not be upgradable at all.  If it is,
there may be a limited number of options, and it
will usually cost at least twice that of a desktop
drive, so plan ahead.

   A docking station may provide one or two
expansion slots for expandability, but you will
have to duplicate docking stations and peripherals
if you need them in both locations.  Laptops with
PCMCIA slots also offer flexibility for expansion.

   In addition, the display resolution on a laptop
is built into the motherboard.  Even if you attach
a large monitor, you cannot upgrade to a higher
resolution unless you have a docking station with
another VGA adapter in it and the laptop is built
to switch to an external adapter.


                   WHERE TO BUY
The best price to pay for a personal computer and
the best place to buy it often has more to do with
the support you need than the equipment you
purchase.  If you don't need support, shop for the
best price from local dealers, superstores and the
mail-order houses.

   Most components in PCs are highly reliable, but
there are always exceptions.  Hard and floppy
drives come from a handful of vendors, but there
are dozens of motherboard manufacturers.  Look for
OS/2 and Novell NetWare certification, a good sign
of compatibility.  Get customer referrals if
possible.

   One component that ought to be better in brand-
name machines than in no-name clones is the power
supply.  If you use your computer all day, or if
you keep it on 24 hours as some do, opt for the
brand name.  The power supply in the no-name clone
might give way in a year or so.  An option is to
buy the no-name clone and put in a better power
supply, such as one from PC Power and Cooling,
Carlsbad, CA.

   If you're new to computers, look for local
dealers that specialize in hand holding for the
novice.  There is usually a dealer nearby that
caters to the beginner.  You may pay a few hundred
dollars more for your system, but it may be well
worth it, saving you time and frustration later.

   The superstores are also a good source for
computers, but the amount of support you get will
vary from store to store.  Remember, you can always
pay a consultant by the hour to help you if you
don't know any sympathetic hackers.

   The mail-order houses are another good source
with quality machines, but you will have to rely on
technical support by phone.  Ironically, the more
successful the direct sales organization, the worse
its phone support becomes, if only temporarily.  A
disadvantage of mail order is that you will have to
ship back your unit if you can't fix it by phone.
Look for mail-order firms with on-site support
administered by a national repair organization.


         Caution # 1 - The Small Business
The small business looking to automate its
accounting is going to need more help.  Don't be
fooled by the prices of hardware and off-the-shelf
software.  The small company often has information
requirements as complicated as a much larger one.
There are countless custom-designed applications
that have cost $5,000 to $25,000, running on $1,500
PCs, because no off-the-shelf software package
could fit the bill.

   It's tempting to think a $100 software package
can do the accounting for your entire company, and
the fact is, in some cases, it very well can.  But,
even if you understand your detailed information
requirements, matching them with the marketing
blurbs about a package's features is not always
straightforward.  You may not find the software's
limitations until after you are up and running.

   Determining the best accounting software for
your particular needs is not something most PC
vendors want to get involved with.  To do the job
right, it can take hours, days or weeks of analysis
depending on your business and what you want to
computerize.  You may want to use the services of a
software consulting firm or an independent
consultant.


          Caution #2 - The Bleeding Edge
Even if you can easily afford the newest
technology, it's not always a good idea to be the
first on the block to have it.  Wait a bit.  Ask
around.  When the bugs are finally fixed, and that
can take several months, you may be a lot better
off.  Good luck and happy computing.

   See Lessons Personal computers.





how to transfer a file

              Within the Same Machine
          From one Application to Another
The ability to transfer a file from one application
to another within the same machine depends on the
import and export capabilities of the application.
All full-featured applications accept a variety of
foreign files.

   Graphics applications (drawing programs, desktop
publishing, image editing, etc.) are typically
designed to import and export a wide variety of
file formats.  Just look at the import/export
menus.

  Some word processing and database programs can
detect different document and database types when
you open a file.  Other programs have to be
explicity told the type of file it is.  If you're
not sure, look for import/export menus or read the
import/export section in the manual or online help.


           From One Computer to Another
           Using a File Transfer Program
File transfer programs provide the simplest method
for transferring files between computers.  For
remote transfer, you need a modem and the file
transfer program on both machines.  The modems do
not have to come from the same vendor, but the file
transfer programs do.  However, if the remote
computer does not already have the program
installed, the transfer program can usually install
itself on the remote computer after you connect to
it, using its remote install procedure.

   In a file transfer program, the transfer
protocols are built in requiring no selection by
the user, and the entire operation is set up to
send and receive.  You can view on screen the
directories of both the local and remote machines.

   For transfer between local machines, file
transfer programs come with special cables to
connect both computers via the serial or parallel
ports.  See DOS Interlink.


           From One Computer to Another
          Using a Communications Program
Files can be transferred using general-purpose
communications programs.  The programs do not have
to be the same in both machines.  In order to
transfer a file remotely, both machines need
modems, which can come from different vendors.

   The user in the receiving computer sets the
communications program to Auto Answer.  The user in
the sending computer uses the communications
program to dial up the modem of the receiving
machine.  Both users must agree on a file transfer
protocol, the most common today being Zmodem.  When
a connection is made, the sending computer selects
Upload and identifies the file or files to be sent.
The receiving computer selects Download.  When the
transfer is complete, each user selects "hang up."

   If the machines are side by side, instead of
using a modem, connect a null modem cable between
the serial ports of both machines.  Since there are
no modems and telephone lines to dial, the transfer
is made by selecting Upload and Download (send and
receive) in the respective communications programs.


              From an Online Service
Online services allow for downloading files, and
each one provides its own method for doing so.  If
you are connected to the service via your own
general-purpose communications program, you have to
find the forum of interest and then select Download
from a menu of options.  You can search for file
names if you do not know the name.  You will also
be asked to select a file transfer protocol.
Zmodem is always a good choice.

   Many online services provide their own software
to help you select options and navigate their
databases.  If you are using such a program, such
as CompuServe's WinCIM, a series of menus makes it
easier to search for and download the files you
need.





how to use this database
This database is both a dictionary and a text book.
Fundamental terms are explained in depth, while
many technical terms are explained in more
technical language.

   All technical terms used to define a term are
also in this database.  You can quickly jump to a
term within a term by clicking on it (double click
in Windows) and go back to where you started by
selecting Review.

   Be sure to look up "lessons," which are lists of
terms by topic.  Set a bookmark in the list,
hypertext to the first term and read it, then find
the bookmark to go back to the list.

   Also remember that syntax examples for all the
important DOS commands are included.  A complete
DOS tutorial (DOS abc's) is also available for
beginners.  Print it out and go through it step by
step.

   There's Windows help for beginners with handy
review lists of important Windows functions.

   After you've been around computers awhile, you
will likely need to compress a file to save time
sending it via modem or to save space storing it on
a floppy.  Look up "Pkzip abc's" for details.

   Good luck!





how to work with DOS
All the DOS command examples are listed under "DOS"
in the index; for example, DOS Copy, DOS Format,
etc.  For a complete tutorial on how DOS disks are
organized and how you interact with DOS at the
command line, see DOS abc's.



how to work with Windows
Look under "Win" for a list of Windows basics; for
example, Win abc's, Win Clipboard, etc.



HP
(Hewlett-Packard Company, Palo Alto, CA)  A major
manufacturer of computers and electronics.  HP was
founded in 1939 by William Hewlett and David
Packard in a garage behind the Packard's California
home.  Its first product, an audio oscillator for
measuring sound, was the beginning of a line of
electronics that made HP an international supplier
of electronic test and measurement instruments.
Walt Disney Studios, HP's first big customer,
purchased eight oscillators to develop and test a
new sound system for the movie "Fantasia."

   HP entered the computer field in 1966 with the
2116A, the first of the HP 1000 series designed to
gather and analyze the data produced by HP
instruments.  HP 1000 computers are used for CIM
applications, such as process monitoring and
control, alarm management and machine monitoring.

   In 1972, HP branched into business computing
with the 3000 series, a multiuser system that
became well known for its high reliability,
especially for that time.  The successful 3000
family has continued to be one of HP's major
computer series.  Also in 1972, HP introduced the
first scientific handheld calculator, the HP-35,
obsoleting the slide rule and ushering in a new age
of pocket-sized calculators.  In 1982, the first HP
9000 workstation was introduced.

   HP's first personal computer was the Touchscreen
150, an MS-DOS personal computer that gained only
modest acceptance.  In 1985, it introduced the
Vectra, a 286-based machine that was the first of a
complete line of IBM-compatible PCs.

   In 1984, HP revolutionized the printer market
with its desktop LaserJet printer, which has set
the standard for the industry.  HP continues its
leadership in this area with routine advances in
resolution, speed and price.

   In 1986, it introduced Precision Architecture, a
RISC-based architecture for its 3000 and 9000
series product lines, which has proven very
successful.  HP's 1989 acquisition of Apollo
Computer made it the market leader in workstations.
Combining features with its own models, it
introduced the series 700 workstations in 1991.

   HP sells over 10,000 different products in the
electronics and computer field and has gained a
worldwide reputation for its quality engineering.



HP 1000
A family of realtime computers from HP introduced
in 1966.  They are sensor-based computers used
extensively in laboratory and manufacturing
environments for collecting and analyzing data.



HP 3000
A family of business-oriented computers from HP.
These midrange computers set a standard for
reliability and rugged engineering when they were
introduced in 1972.  Today's 900 models use HP's
PA-RISC architecture, are compatible with the
original 3000s and run the MPE/iX operating system.
Over the years, HP 3000s have migrated from the
central computer architecture to client/server, in
which intelligent workstations and PCs have
replaced the dumb terminal.



HP 9000
A family of high-performance UNIX workstations and
business servers from HP all running the HP/UX
operating system.  The series 700 are workstation
clients and the series 800 and model T500 are
servers.  The T500 is a multiprocessing mainframe
class computer that can contain up to 12 CPUs.  All
current models use HP's PA-RISC architecture.

   The earlier series 300 and 400 were based on
Motorola 680x0 CPUs, and the series 500 and 600
were predecessors to current models.



HP PA-RISC
(Hewlett-Packard Precision Architecture-RISC)  A
proprietary RISC architecture from HP introduced in
1986 that is incorporated into all new models of
its 3000 and 9000 computer families.



HP-UX
HP's version of UNIX that runs on its 9000 family.
It is based on SVID and incorporates features from
BSD UNIX along with several HP innovations.



HP-VUE
A Motif-based graphical user interface used in HP
workstations.  Parts of HP-VUE are used in COSE's
CDE (Common Desktop Environment).



HPC
See High-Performance Computing.



HPFS
(High Performance File System)  The file system,
introduced with OS/2 Version 1.2, that handles
larger disks (2TB volumes; 2GB files), long file
names (256 bytes) and can launch the program by
referencing the data as in the Macintosh.  It
coexists with the existing FAT system.



HPGL
(Hewlett-Packard Graphics Language)  A vector
graphics file format from HP that was developed as
a standard plotter language.  Most plotters support
the HPGL and DMPL standards.



HPIB
(Hewlett-Packard Interface Bus)  HP's version of
the IEEE 488 standard GPIB.



HS
(High Speed)  See modem.



HSB
(Hue Saturation Brightness)  See HSV.



HSL
(Hue Saturation Lightness)  See HLS.



HSM
(Hierarchical Storage Management)  The automatic
movement of files from hard disk to slower, less-
expensive storage media.  The typical hierarchy is
from magnetic disk to optical disk to tape.  HSM
software constantly monitors hard disk capacity and
moves older data from one storage level to the
next.  HSM often includes a system for routine
backup as well.



HSSI
(High-Speed Serial Interface)  A standard for a
serial connection with transmission rates up to 52
Mbps.  It is often used to connect to T3 lines.



HST
(1) An asymetrical modem protocol from U.S.
Robotics that includes error control and
compression and transmits from 4800 to 14400 bps in
one direction and from 300 to 400 bps in the other.
HST was the first reliable, high-speed modem
protocol before the V.32bis and V.42 standards
became widely used.

(2) (Hubble Space Telescope)  Launched in April
1990, it views star material some 10 to 12 billion
light years from earth.



HSV
(Hue Saturation Value)  A color model that uses a
cylindrical coordinate system structured as an
inverted hexcone (six-sided pyramid).  The hue, or
H, is measured by the angle around the vertical
axis in degrees with red at 0, yellow 60, green
120, cyan 180, blue 240 and magenta 300.  The
saturation, or S, is the amount of color from 0 to
1 or 0 to 100%.  The value, or V, is the amount of
light from black to white (0 to 1 or 0 to 100%).
For example, pure green would be H=120, S=1 and
V=1.  See HLS.



HTML
(HyperText Markup Language)  A standard for
defining hypertext links between documents.  It is
a subset of SGML (Standard Generalized Markup
Language).



HTTP
(HyperText Transport Protocol)  A client/server
protocol used for information sharing on the
Internet.  It is the basis of the Worldwide Web
(WWW).



hub
A central connecting device in a network that joins
communications lines together in a star
configuration.  Passive hubs are just connecting
units that add nothing to the data passing through
them.  Active hubs, also sometimes called multiport
repeaters, regenerate the data bits in order to
maintain a strong signal, and intelligent hubs
provide added functionality.

   Hubs are required in twisted pair Ethernet
(10BaseT) and Token Ring networks.  In Token Rings,
the hub is called a MAU (Multi-station Access
Unit).  Multiple media hubs interconnect different
types of Ethernets (twisted pair, coax and optical
fiber).  Hubs can provide bridging between LAN
types; for example, Ethernet, Token Ring and FDDI.
Switching hubs provide Ethernet and ATM switching.

   Hubs have become very intelligent, modular and
customizable, allowing for the insertion of
bridging, routing and switching modules all within
the same unit.  A hub can even host a CPU board and
network operating system, turning the hub into a
file server or some type of network control
processor that performs LAN emulation or other
complex function as networks grow.



hub ring
A flat ring pressed around the hole in a 5.25"
floppy disk for rigidity.  The drive's clamping
ring presses the hub ring onto the spindle.



hue
In computer graphics, a particular shade or tint of
a given color.



Huffman coding
A statistical compression method that converts
characters into variable length bit strings.  Most-
frequently-ocurring characters are converted to
shortest bit strings; least frequent, the longest.
Compression takes two passes.  The first pass
analyzes a block of data and creates a tree model
based on its contents.  The second pass compresses
the data via the model.  Decompression decodes the
variable length strings via the tree.  See LZW.



hybrid circuit
See hybrid microcircuit.



hybrid computer
A digital computer that accepts analog signals,
converts them to digital and processes them in
digital form.  It is used in process control and
robotics.



hybrid file
Sometimes refers to a graphics file that contains
vector graphics and raster graphics (bitmapped)
images.  See metafile.



hybrid microcircuit
An electronic circuit composed of different types
of integrated circuits and discrete components,
mounted on a ceramic base.  Used in military and
communications applications, it is especially
suited for building custom analog circuits
including A/D and D/A converters, amplifiers and
modulators.  See MCM.



hybrid network
In communications, a network made up of equipment
from multiple vendors.



Hydra
(1) (Hybrid Document Reproduction Apparatus)  A
printer, photocopier, scanner and fax built into
one machine.

(2) A device that converts analog signals to ISDN
Basic Rate Interface (BRI).

(3) A utility from the Austin Mac Developer's
Association that tests Macintosh graphics card
performance.



Hyperaccess
A PC communications program from Hilgraeve, Inc.,
Monroe, MI, that provides data compression, has its
own script language and supports a variety of
terminals and protocols.



HyperCard
An application development system from Apple that
runs on the Macintosh and Apple IIGS.  Using visual
tools, users build "stacks" of "cards" that hold
data, text, graphics, sound and video with
hypertext links between them.  The HyperTalk
programming language allows complex applications to
be developed.  Third-party compilers can compile
HyperCard stacks into executable programs,
eliminating the need to have HyperCard running in
order to execute the stacks.

   HyperCard used to be more popular with many
commercial and shareware stacks being developed
routinely.  Today Apple includes only a runtime
version with its Macs, not the full development
version, which is available from Claris.

   HyperCard's visual programming approach was
brought to PCs with Brightbill-Robert's HyperPad
and Asymetrix's ToolBook.



hypercube
A parallel processing architecture made up of
binary multiples of computers (4, 8, 16, etc.).
The computers are interconnected so that data
travel is kept to a minimum.  For example, in two
eight-node cubes, each node in one cube would be
connected to the counterpart node in the other.



hyperlink
A predefined linkage between one object and
another.  See hypertext.



hypermedia
The use of data, text, graphics, video and voice as
elements in a hypertext system.  All the various
forms of information are linked together so that a
user can easily move from one to another.



HyperPAD
An application development system for PCs from
Brightbill-Roberts & Company, Ltd., Syracuse, NY.
It is a HyperCard-like program that works in text
mode and includes the PADtalk scripting language.



HyperScript
An advanced macro (scripting) language that is
provided with the WINGZ spreadsheet.



HyperTalk
The programming language used in HyperCard.



hypertext
Linking related information.  For example, by
selecting a word in a sentence, information about
that word is retrieved if it exists, or the next
occurrence of the word is found.  The concept was
coined by Ted Nelson as a method for making the
computer respond to the way humans think and
require information.

   In the electronic versions of this database, you
can hypertext to the definition of any term used
within the definitions by clicking on it or
highlighting it with the mouse.



hyperware
Hypertext products.



hyphen ladder
Hyphens on two or more consecutive lines, which
causes distraction to the reader.



hyphenation
Breaking words that extend beyond the right margin.
Software hyphenates words by matching them against
a hyphenation dictionary or by using a built-in set
of rules, or both.  See discretionary hyphen.



hyphenation dictionary
A word file with predefined hyphen locations.



hyphenation zone
The distance from the right margin within which a
word may be hyphenated.



hypotenuse
In a right triangle, the side opposite the right
angle.  See sine.



hysteresis
The lag between making a change, such as increasing
or decreasing power, and the response or effect of
that change.



Hz
(HertZ)  See Hertz.



I-CASE
(Integrated CASE)  CASE systems that generate
applications code directly from design
specifications.  Features include support for rapid
prototyping, modeling the data and processing and
drawing logic diagrams.



I/E time
See instruction cycle.



i-node
(Identification NODE)  An individual entry in a
directory system that contains the name of and
pointer to a file or other object.



I/O
(Input/Output)  Transferring data between the CPU
and a peripheral device.  Every transfer is an
output from one device and an input into another.



I/O address
(1) On PCs, a three-digit hexadecimal number (2AB,
2A0, etc.) used to identify and signal a peripheral
device (serial port, parallel port, sound card,
etc.).  Address assignments must be unique,
otherwise conflicts will occur.  There are usually
a small number of selectable addresses on each
controller card.  See PC conflicts and PC I/O
addressing.

(2) The identifying address of a peripheral device.



I/O area
A reserved segment of memory used to accept data
from an input device or to accumulate data for
transfer to an output device.  See buffer.



I/O bound
Refers to an excessive amount of time getting data
in and out of the computer in relation to the time
it takes for processing it.  Faster channels and
disk drives improve the performance of I/O bound
computers.



I/O card
See expansion board and PC card.



I/O channel
See channel.



I/O device
Same as peripheral device.



I/O interface
See port and expansion slot.



I/O processor
Circuitry specialized for I/O operations.  See
front end processor.



I/O statement
A programming instruction that requests I/O.



I-time
See instruction time.



i486
See 486.



i750
A programmable compression chip from Intel that
supports a variety of techniques including DVI,
MPEG and JPEG.



i860
A RISC-based, 64-bit processor from Intel that uses
a 64-bit data bus, has built-in floating point and
3-D graphics capability and contains over one
million transistors.  It can be used as a stand-
alone CPU or to accelerate performance in existing
systems.



IAB
See Internet.



IAC
(InterApplication Communications)  The IPC
capability in Macintosh System 7.0.



IBI
(Information Builders, Inc., New York)  IBI is the
creator of the FOCUS database management system and
the EDA/SQL middleware.  See FOCUS and EDA/SQL.



IBM
(International Business Machines Corporation,
Armonk, NY) The world's largest computer company.
It started in New York in 1911 when the Computing-
Tabulating-Recording Company. (CTR) was created by
a merger of The Tabulating Machine Company
(Hollerith's punched card company in Washington,
DC), International Time Recording Company (time
clock maker in NY state), Computing Scale Company
(maker of scales and food slicers in Dayton, Ohio),
and Bundy Manufacturing (time clock maker in
Poughkeepsie, NY).  CTR started out with 1,200
employees and a capital value of $17.5 million.

   In 1914, Thomas J. Watson, Sr., became general
manager.  During the next 10 years, he dispensed
with all non-tabulating business and turned it into
an international enterprise renamed IBM in 1924.
Watson instilled a strict, professional demeanor in
his employees that set IBMers apart from the rest
of the crowd.

   IBM achieved spectacular success with its
tabulating machines and the punched cards that were
fed into them.  From the 1920s through the 1960s,
it developed a huge customer base that was ideal
for conversion to computers.

   IBM launched its computer business in 1953 with
the 701 and introduced the 650 a year later.  By
the end of the 1950s, the 650 was the most widely
used computer in the world with 1,800 systems
installed.  The 1401, announced in 1959, was its
second computer winner, and by the mid 1960s, an
estimated 18,000 were in use.

   In 1964, it announced System/360, the first
family of compatible computers ever developed.  The
360s were enormously successful and set a standard
underlying IBM mainframes to this day.

   During the 1970s and 1980s, IBM made a variety
of incompatible minicomputer systems, including the
System/36 and System/38.  Its highly-successful
AS/400, introduced in 1988, provides a broad family
of compatible machines in this segment.

   In 1981, IBM introduced the PC into a chaotic
personal computer field and set the standard almost
overnight.  IBM is still one of the largest single
suppliers of PCs, but the majority of sales come
from the PC industry at large, from companies such
as Compaq and Dell to mom and pop shops by the
thousands.

   Although IBM is a company with over 60 billion
dollars in sales, the early 1990s have been gut-
wrenching years.  IBM experienced major losses in
1992 and 1993, due mainly to slowing sales of high-
profit mainframes as companies worldwide began to
implement client/server systems with smaller
computers.  IBM also reduced its PC prices to
become more competitive, further reducing margins.
To meet the new marketing challenges of the 1990s,
IBM has reduced its staff by more than 150,000
employees and has engaged in a number of new
ventures.

   In 1993, IBM created its own competition by
offering PC clones via direct mail under the Ambra
brand name without the IBM logo.  However, a year
later, it shut down Ambra, claiming it caused too
much confusion in the marketplace.  Also in 1993,
the first of the PowerPC systems were developed,
initially as new workstations in the RS/6000 line.
This is the fruition of IBM's alliance with Apple
and Motorola, which surprised everyone when it was
announced in 1991 (see Apple for details).  New IBM
PowerPC-based PCs are on the horizon, which may
provide the first serious competition to the
current PC architecture since its inception.

   It's going to be very interesting to witness
IBM's strategy and tactics for exchanging slowing
mainframe revenues with sales of today's new and
powerful workstation/PC architectures.  No doubt,
many more surprises are in store!



IBM-compatible PC
A personal computer that is compatible with the IBM
PC and PS/2 standards.  Although this term is still
used, it had more validity in the early days when
PC makers were trying to copy the IBM PC, and many
PCs were not compatible.  Today, PCs conform to
standards that, although originally set by IBM,
have been modified over time by the PC industry at
large.



IBM mainframes
Following is a list of the different series of
mainframes IBM has offered over the years.  All of
the series in this list stem from the original
System/360 architecture introduced in 1964.  For
information about a series, look up the individual
term.


    Year
 Introduced  Series name  (model numbers)
    1964     System/360   (20 to 195)
    1970     System/370   (115 to 168)
    1977     303x series  (3031, 3032, 3033)
    1979     43xx series  (4300 to 4381, ES/4381)
    1980     308x series  (3081, 3083, 3084)
    1986     3090 series  (120 to 600, ES/3090)
    1986     9370 series  (9370, ES/9370)
    1990     System/390   (ES/9000, 120 to 900,
                                    120 to 9X2)





IBM minicomputers
Following is a list of the different series of
minicomputers IBM has offered over the years.  For
information about a series, look up the individual
term.


    Year
 Introduced   Series name
    1969      System/3
    1975      System/32
    1976      Series/1
    1977      System/34
    1978      System/38
    1978      8100
    1983      System/36
    1985      System/88
    1988      AS/400
    1990      RS/6000





IBM PC
Following is a list of early IBM PCs as well as
PS/2 models whose model numbers do not convey CPU
size and speed.  Other models of IBM personal
computers conform to common numbering systems used
by the PC industry; for example, 486/33 and 486/66.
Also included in the list are the popular ThinkPad
notebooks.

   For information about PCs, look up PC.


        FIRST GENERATION PC MODELS

            Year
Model      Intro.  CPU      Features
PC          1981   8088, No. 1 (floppy only)
XT          1983   8088, slow hard disk
XT 286      1986    286, slow hard disk
XT/370      1983   8088, 370 emulation
AT          1984    286, medium-speed hard disk
3270 PC     1983   8088, 3270 emulation
PCjr        1983   8088, floppy-based home use
PC Portable 1984   8088, floppy-based portable
Convertible 1986   8088, microfloppy laptop


       SECOND GENERATION PS/2 MODELS

PS/2 models use the Micro Channel bus architecture
unless otherwise noted below.

         Year
Model   Intro. CPU       Features
25       1987  8086, PC bus (limited expansion)
30       1987  8086, PC bus
30-286   1988  286, ISA bus
35 LS    1991  386SX, ISA bus, diskless
35 SX    1991  386SX, ISA bus
L40 SX   1991  386SX, ISA bus, laptop
40 SX    1991  386SX, ISA bus
N45 SL         386SL notebook
50       1987  286
50 Z     1988  286, faster 50
N51 SX   1992  386SX, notebook
N51 SLC  1992  386SLC, notebook
55 SX    1989  386SX
55 LS    1990  386SX, diskless
56 SLC   1992  386SLC
56 SX    1992  386SX, upgradeable
57 SLC   1992  386SLC
57 SX    1991  386SX, 2.88MB floppy
CL57 SX  1992  386SX, notebook, active matrix color
60       1987  286
65       1990  386SX
70       1988  386
70 486   1989  486
P70      1989  386 portable
P75 486  1990  486 portable, 22 lbs.
76       1994  486SX & DX, OS/2, SCSI
76i      1994  486SX, OS/2, IDE drive
77       1994  DX4, OS/2, SCSI, ECC memory
77i      1994  DX4, OS/2, IDE drive, ECC memory
80       1987  386, tower
90       1990  486, XGA, SCSI, upgradable
90       1992  486DX2/66
95       1990  486, tower
90 SX    1991  486SX
95 SX    1991  486SX, tower


         THINKPAD NOTEBOOK COMPUTERS
 300     1992  386SL/25
 350     1993  486SL/25, PCMCIA slot
 350C    1993  486SL/25, PCMCIA, passive color
 500     1993  486SLC2 50/25, PCMCIA, 3.8 pounds
 700     1992  486SLC/25
 700C    1992  486SLC/25, active matrix color
 710T    1993  486SLC/25, pen-based
 720     1993  486SLC2 50/25, PCMCIA slot
 720C    1993  486SLC2 50/25, PCMCIA, active color
 750Cs   1994  486SL/33, PCMCIA, dual scan passive,
                 removable hard disk, sound





IBM PC Company
A subsidiary of the IBM Corporation located in
Raleigh, NC, that is involved with all aspects of
IBM PCs.



IBM workstation
See RS/6000.



IBMBIO.COM
See IBMDOS.COM.



IBMDOS.COM
One of the disk files that make up PC-DOS.  The
fundamental parts of PC-DOS are contained in
IBMDOS.COM and IBMBIO.COM, both of which are hidden
system files.  The Microsoft version (MS-DOS) is
made up of MSDOS.SYS and IO.SYS.



IC
See integrated circuit and information center.



IC card
See PC card and memory card.



ICCP
(Institute for Certification of Computer
Professionals)  An organization founded in 1973
that offers industry certification and provides
worldwide test centers.  The Associate Computer
Professional exam is open to all.  The Certified
Computer Programmer (CCP), Certified Data Processor
(CDP) and Certified Systems Professional (CSP)
require job experience (academic credit may
substitute).  Address: 2200 E. Devon Ave., Des
Plaines, IL 60018, 708/299-4227.



ICE
(1) (In-Circuit Emulator)  A chip used for testing
and debugging logic circuits typically in embedded
systems.  The chip emulates a particular
microprocessor and contains breakpoints and other
debugging functions.  See ROM emulator.

(2) (Ice)  A Lotus 1-2-3 add-on program from Baler
Software Corporation, Rolling Meadows, IL, that
adds extensions to Lotus macros.  It is used for
developing customized macro-driven 1-2-3 programs.



iCOMP
(Intel COmparative Microprocessor Performance)  An
index of CPU performance from Intel.  It tests a
mix of 16-bit and 32-bit integer, floating point,
graphics and video operations.

             CPU         iCOMP Rating

         386SX   16MHz       22
         386SX   20MHz       32
         386SX   25MHz       39
         386SL   25MHz       41
         386DX   25MHz       49
         386DX   33MHz       68

         486SX   25MHz      100
         486DX   25MHz      122
         486SX   33MHz      136
         486DX   33MHz      166
         486DX2  50MHz      231
         486DX   50MHz      249
         486DX2  66MHz      297
         486DX4  75MHz      319
         486DX4 100MHz      435

        Pentium  60MHz      510
        Pentium  66MHz      567
        Pentium  90MHz      735
        Pentium 100MHz      815





icon
A small, pictorial, on-screen representation of an
object (file, program, disk, etc.) used in
graphical interfaces.  For example, to delete a
file in the Macintosh, the file icon is moved onto
the wastebasket icon.



iconic interface
A user interface that uses icons.



ICR
(Intelligent Character Recognition)  The ability to
recognize hand printing.



IDA
(Intelligent Drive Array)  A high-performance hard
disk interface from Compaq that controls a disk
array via the EISA bus.



IDAPI
(Independent Database API)  The programming
interface to the Borland Database Engine.  IDAPI
calls are made from dBASE, Paradox and C++
applications to access data in one of the supported
databases.  See Borland Database Engine.



IDC
(International Data Corporation, Framingham, MA)
The largest market research, analysis and
consulting firm in the information field.  Founded
in 1964, it provides annual briefings and in-depth
reports on all aspects of the industry.



IDE
(1) (Integrated Drive Electronics)
(2) (Integrated Development Environment)

(1) (Integrated Drive Electronics)  A hard disk
that contains a built-in controller.  IDE drives
are widely used in PCs and range in capacity from
40MB up to 1GB.  The drive connects via a 40-line
flat ribbon cable to an IDE host adapter (often
called an IDE controller) that plugs into an
expansion slot in the PC.  The host adapter
controls up to two IDE drives, but advanced host
adapters and Enhanced IDE adapters control up to
four.

   Some motherboards are built with a 40-pin IDE
connector directly on the board thus freeing up an
expansion slot for use by another device.  The IDE
drive uses the ATA interface (AT Attachment),
although ATA is often only referenced in technical
manuals.  See hard disk and Enhanced IDE.


           Installing a Second IDE Drive
Installing a disk drive correctly requires more
mechanical skill than it does knowledge of
computers or electronics.  Fitting the drive into
the bays and pushing and pulling on wires is the
hard part.

   Many PCs come with one IDE drive, but the IDE
host adapter can usually control two, and the 40-
line flat, signal cable between the host adapter
and the first drive generally has an open connector
for the second drive.

1. DETERMINE IF YOUR BIOS SUPPORTS THE NEW DRIVE
Note the cylinder, heads and sectors (spt)
identified on the second drive.  Go into your BIOS
setup and determine if you can define this new
drive properly.  To get into setup, many PCs tell
you on startup what key to press right away,
typically the Del key, but sometimes the F1 key.
If there is no startup message telling you about
setup, look in your hardware manual.  Some key
combination, such as Ctrl-Alt-Esc, may be used.

   When you are in the setup program, cursor down
to the second hard drive, which is either D: or 1
(drives are either indicated as C and D or 0 and
1).  If you are installing a hard disk that is
152MB or less, your disk type may be listed under
Types 1 through 46.  If not, or if your disk is
larger than 152MB, select Type 47, and enter the
number of cylinders, heads and sectors to derive
your total drive size.

   You must know the corrent number of cylinders,
heads and sectors on your new disk.  Most new
drives print this information on the drive itself.
Earlier drives do not, and you will have to obtain
this information from your vendor or some other
source (see hard disk references).  If you know
your write precomensation track (WPCOM), enter it.
Likewise, if you know your landing zone cylinder,
enter that number as well.

   This time, exit setup without saving anything.

   If you were able to define the new drive
successfully, proceed with step #2, otherwise do
not proceed and review the problem with your
hardware support personnel.

2. INSTALL THE DRIVE
Turn the computer off.  Look at your drives and
locate the Master/Slave jumpers.  These are tiny
plastic blocks that fit over two vertical pins.
They are generally labelled M and S or MA and SL.
Your first drive is already set to Master.  Either
M or MA is jumped or there is no jumper used.

   If you have a jumper, place it over Slave on the
second drive.  If you do not have a jumper, take
the jumper off M or MA on the first drive (it will
still act as Master) and place it on Slave on the
second one.  If there is no jumper on the first
drive and you do not have another one, get a jumper
before proceeding.

   Insert the new drive into a drive bay and screw
it in.  Do not over-tighten screws into the drive.
If you want to put a 3.5" drive into a 5.25" drive
bay, get an adapter that holds the drive and fits
into the 5.25" bay.

   Plug an available four-wire (red-black-black-
yellow/orange) power cable into the drive (it only
fits one way).  If none is available, get a power
cable splitter, pull out an existing power
connection to another drive and insert the
splitter.  Attach both drives to the splitter.

   The connectors on the flat signal cable can be
inserted up or down, so be sure to connect the
second drive in the same direction as the first
drive.  If the cable isn't long enough, a longer
40-pin IDE ribbon cable can be purchased.  The
three connectors on the cable are common, and
either one can be used for either drive or the host
adapter.  One side of the cable is usually colored.
Line that side up with pin 1 on the host adapter
and the drives if you have to start from scratch.

   After installing the drives, turn on the
computer and go immediately into setup mode and re-
enter the data from step #1 above.  This time,
select the option that saves the new data to the
CMOS RAM.  The computer will reboot, and the second
drive is now ready for Fdisk and Format (see
Formatting a Hard Disk under DOS Format).


(2) (Integrated Development Environment)  A set of
programs run from a single user interface.  For
example, programming languages often include a text
editor, compiler and debugger, which are all
activated and function from a common menu.



IDE controller
The term generally refers to an IDE host adapter,
the plug-in card used to attach IDE drives.  Since
an IDE drive contains both the controller and the
drive, the term technically refers to the
controller built into the drive housing, not the
interface to the computer.  However, this
distinction would only be critical for a very
technical person such as a disk drive design
engineer.  See IDE host adapter.



IDE host adapter
An expansion board that plugs into a PC, which is
used to connect either two or four IDE hard disks.
It generally also provides control for two floppy
disks, two serial ports, a parallel port and a game
port.  Sometimes, the IDE host adapter is built
onto the motherboard.  See enhanced IDE.



idle character
In data communications, a character transmitted to
keep the line synchronized when there is no data
being sent.



idle interrupt
An interrupt generated when a device changes from
an operational state to an idle state.



idle time
The duration of time a device is in an idle state,
which means that it is operational, but not being
used.



IDMS
See CA-IDMS.



IE
See information engineering.



IEC
(International Electrotechnical Commission)  An
organization that sets international electrical and
electronics standards founded in 1906 and
headquartered in Geneva.  It is made up of national
committees from over 40 countries.  Contact is via
ANSI in New York.



IEEE
(Institute of Electrical and Electronic Engineers)
A membership organization that includes engineers,
scientists and students in electronics and allied
fields.  Founded in 1963, it has over 300,000
members and is involved with setting standards for
computers and communications.  Address: 345 E. 47th
St., New York, NY 10017, 212/705-7900.

   The Computer Society of the IEEE has over
100,000 members and holds meetings and technical
conferences on computers.  Address: 1730 Mass. Ave.
N.W., Washington, DC 20036, 202/371-0101.



IEEE 1284
An IEEE standard for an enhanced parallel port that
is compatible with the Centronics parallel port
commonly used on PCs.  The standard also defines
the type of cable that must be used in order to
increase distances up to 30 feet and sustain the
higher transfer rates.

   There are several modes of operation.  The EPP
(Enhanced Parallel Port) mode provides high-speed
transfer to 500 Kbytes/sec compared to about 150
Kbytes/sec for Centronics.  It also allows multiple
devices to be daisy chained from one port.  A
higher-speed ECP (Enhanced Capabilities Port) mode,
originally developed by Microsoft and HP, provides
speeds up to 2Mbytes/sec in each direction.  Nibble
and byte modes provide slower bi-directional
transfer.



IEEE 488
See GPIB.



IEEE 802
IEEE standards for networking.  See "LANs" under
data link protocol.

  802.1Covers network management, etc.Ŀ
    
     802.2Specifies data link layer forĿ
              the following access methods     
     
      802.3Ŀ 802.4Ŀ 802.5Ŀ 802.6Ŀ
       CSMA/CD    token   token   DQDB  
      "Ethernet"  bus     ring    MAN   
         
      802.12Ŀ
       Demand   
       priority 
    





IEEE 802.12
See Fast Ethernet.



IEF
(Information Engineering Facility)  A fully-
integrated set of CASE tools from TI that runs on
PCs and MVS mainframes.  It generates COBOL code
for PCs, MVS mainframes, VMS, Tandem, AIX, HP-UX
and other UNIX platforms.



IETF
See Internet.



IEW
(Information Engineering Workbench)  CASE software
from Sterling Software, Atlanta, GA (formerly
KnowledgeWare), that runs on DOS PCs and generates
COBOL, CICS and IMS code for MVS mainframes.



if-then-else
A high-level programming language statement that
compares two or more sets of data and tests the
results.  If the results are true, the THEN
instructions are taken; if not, the ELSE
instructions are taken.  The following is a BASIC
example:

   10  IF ANSWER = "Y"  THEN PRINT "Yes"
   20  ELSE PRINT "No"


   In certain languages, THEN is implied.  All
statements between IF and ELSE are carried out if
the condition is true.  All instructions between
ELSE and ENDIF are carried out if not true.  The
following dBASE example produces the same results
as above:

   IF ANSWER = "Y"
       ? "Yes"
     ELSE
       ? "No"
   ENDIF





IFIP
(International Federation of Information
Processing)  A multinational affiliation of
professional groups concerned with information
processing, founded in 1960.  There is one voting
representative from each country (U.S.
representative is FOCUS).  Address: 16 Place
Longemalle, CH-1204 Geneva, Switzerland, 41 22 28
2649.



IFS
(Installable File System)  An OS/2 feature that
supports multiple file systems.  Different systems
can be installed (UNIX, CD-ROM, etc.) just like
drivers are installed for new peripherals.



IGES
(Initial Graphics Exchange Specification)  An ANSI
graphics file format that is system independent and
also intended for human interpretation.  It evolved
out of the Air Force's Integrated Computer
Automated Manufacturing (ICAM) program in 1979.
For more on IGES and PDES, contact: IGES
Organization, National Institute of Standards &
Technology, Building 220, Room A-353, Gaithersburg,
MD 20899, 301/921-3691.



IHV
(Independent Hardware Vendor)  An organization that
makes electronic equipment.  It implies a company
that specializes in a niche area, such as display
adapters or disk controllers, rather than a
computer systems manufacturer.  Contrast with ISV.
See VAR and systems integrator.



IIA
(1) (Information Industry Association)  A trade
organization that includes members from all aspects
of the information field.  Its purpose is to
conduct active government relations that safeguard
the interests of a healthy, competitive information
industry.  IIA sponsors seminars and conferences
and provides newsletters, newspapers and books.
Address: 555 New Jersey Ave. N.W., Washington, DC
20001, 201/639-8262.

(2) (Information Interchange Architecture)  IBM
formats for exchanging documents between different
systems.



illustration program
Same as drawing program.



Illustrator
See Adobe Illustrator.



IM
See information management.



IMA
(Interactive Multimedia Association)  A trade
association founded in 1988 originally as the
Interactive Video Industry Association.  The IMA
provides an open process for adopting existing
technologies and is involved in subjects such as
networked services, scripting languages, data
formats and intellectual property rights.  Address:
3 Church Circle, Annapolis, MD 21401, 410/626-1380.



image
(1) A picture (graphic).

(2) See system image.



image editing
Changing or improving graphics images either
interactively using a paint program or by using
software routines that alter contrast, smooth lines
or filter out unwanted data.  See image filter and
anti-aliasing.



image editing program
Software that allows images to be altered and
enhanced.  Image editing capabilities are found in
full-featured paint programs, such as Adobe
Photoshop and Fractal Design Painter.  See image
filter and anti-aliasing.



image enhancement
See image editing.



image filter
A routine that changes the appearance of an image
or part of an image by altering the shades and
colors of the pixels in some manner.  Filters are
used to increase brightness and contrast and add a
wide variety of special effects to a picture.



image processing
(1) The analysis of a picture using techniques that
can identify shades, colors and relationships that
cannot be perceived by the human eye.  It is used
to solve identification problems, such as in
forensic medicine or in creating weather maps from
satellite pictures and deals with images in raster
graphics format that have been scanned in or
captured with digital cameras.

(2) Any image improvement, such as refining a
picture in a paint program that has been scanned or
entered from a video source.

(3) Same as imaging.



imagesetter
A typesetting machine that handles text and
graphics and typically accepts PostScript input.
See phototypesetter.



imaging
Creating a film or electronic image of any picture
or paper form.  It is accomplished by scanning or
photographing an object and turning it into a
matrix of dots (raster graphics), the meaning of
which is unknown to the computer, only to the human
viewer.  Scanned images of text may be encoded into
computer data (ASCII or EBCDIC) with page
recognition software (OCR).  See micrographics,
image processing and document imaging.



imaging model
A set of rules for representing images.



imaging system
See document imaging, image processing and image
enhancement.



immediate access
Same as direct access.



impact printer
A printer that uses a printing mechanism that bangs
the character image into the ribbon and onto the
paper.  See printer for examples.



impedance
The resistance to the flow of alternating current
in a circuit.



implementation
(1) Computer system implementation is the
installation of new hardware and system software.

(2) Information system implementation is the
installation of new databases and application
programs and the adoption of new manual procedures.



implode
To link component pieces to a major assembly.  It
may also refer to compressing data using a
particular technique.  Contrast with explode.



import
To convert a file in a foreign format to the format
of the program being used.



Impromptu
A Windows query and reporting tool from Cognos with
support for a large variety of databases.  It is
capable of generating cross tabs for spreadsheets
such as Excel, Lotus for Windows and Quattro Pro
for Windows.



Improv
A multidimensional Windows spreadsheet from Lotus
that allows for easy switching to different views
of the data.  Data is referenced by name as in a
database rather than the typical spreadsheet row
and column coordinates.  Improv was originally
developed for the NeXt computer.



IMS
(Information Management System)  An IBM
hierarchical DBMS for mainframes under MVS.  It was
widely implemented throughout the 1970s and
continues to be used.  IMS/DC is its transaction
processing component (like CICS) that handles the
details of communications and SNA networking.
IMS/DC is also used to access DB2 databases.



in-circuit emulator
See ICE.



in hardware
Refers to logic that has been placed into the
electronic circuits of the computer.



in software
Refers to logic in a program.  For example, "that
routine is done in software."


incident light
In computer graphics, light that strikes an object.
The color of the object is based on how the light
is absorbed or reflected by the object.



Incorrect DOS version
A DOS error message that means the command you are
using belongs to another version of DOS.  Somehow
an earlier or later version of a command is on your
hard disk.  Commands from one DOS version often do
not work in other versions.



increment
To add a number to another number.  Incrementing a
counter means adding 1 to its current value.



incremental backup
See backup types.



incremental spacing
See microspacing.



IND$FILE
An IBM mainframe program that transfers files
between the mainframe and a PC functioning as a
3270 terminal.



indent
To align text some number of spaces to the right of
the left margin.  See hanging paragraph.



Indeo
A video compression/decompression algorithm from
Intel that is used to compress movie files.



independent software vendor
See ISV.



index
(1) In data management, the most common method for
keeping track of data on a disk.  Indexes are
directory listings maintained by the OS, DBMS or
the application.

   An index of files contains an entry for each
file name and the location of the file.  An index
of records has an entry for each key field (account
no., name, etc.) and the location of the record.

(2) In programming, a method for keeping track of
data in a table.  See indexed addressing.



index hole
A small hole punched into a hard sectored floppy
disk that serves to mark the start of the sectors
on each track.



index mark
A physical hole or notch, or a recorded code or
mark, that is used to identify a starting point for
each track on a disk.



index register
A high-speed circuit used to hold the current,
relative position of an item in a table (array).
At execution time, its stored value is added to the
instructions that reference it.



indexed addressing
A technique for referencing memory that
automatically increments the address with the value
stored in an index register.  See subscript (2).



indexed sequential
See ISAM.



indexing
(1) Creating indexes based on key data fields or
key words.

(2) Creating timing signals based on detecting a
mark, slot or hole in a moving medium.



indirect addressing
An address mode that points to another pointer
rather than the actual data.  This mode is
prohibited in RISC architecture.



inductance
The opposition to the changing flow of current in a
circuit, measured in Henrys.



induction
The process of generating an electric current in a
circuit from the magnetic influence of an adjacent
circuit as in a transformer or capacitor.



industrial strength
Refers to software that is designed for high-
volume, multiuser operation.  It implies that the
software is robust and that there are built-in
safeguards against system failures.  For example,
an industrial-strength operating system runs its
applications in protected address spaces and does
not lock up or stop if one of them crashes.
Industrial-strength features in a DBMS are
referential integrity and two-phase commit.

   The term is used to refer to any solid, sound
program that has been thoroughly tested in live
user environments for extensive periods, whether
system software (OS, DBMS, etc.) or application
software (order entry, query, etc.).



Industry Standard Architecture
See ISA.



industry topics
Computers and related fields cover a wide range of
disciplines.  The following topic list is included
to illustrate the depth and breadth of the
industry.  This list is the "HeadsUp Topic
Selection Guide" for the computer industry and is
reprinted with permission of INDIVIDUAL, Inc., 84
Sherman St., Cambridge, MA 02140.  (c) 1994
INDIVIDUAL, Inc.

   HeadsUp is a personal information service that
provides daily news briefs by fax or e-mail of pre-
selected topics.  The full article is transmitted
upon request.  HeadsUp services are also available
for the healthcare, energy, automotive, defense and
financial services industries.  For more
information, call 800/414-1000.


                 COMPUTER HARDWARE

  HIGH PERFORMANCE COMPUTING
    U.S. High-performance computing overview
      Supercomputers
      Parallel processing
      Mainframe systems
      Transaction processing
      Midrange computer systems
        IBM AS/400
      Realtime computer systems
    Workstations
    Multiuser systems distribution

  DESKTOP & PORTABLE COMPUTING
    PC desktop computing overview
      Desktop & portable distribution
    Apple hardware and software
      Apple hardware
    PC portable computing overview
      Notebook computing
      Handheld computing
    Portable computing technology
      Handheld computing
      Portable mass storage devices
      Personal wireless communications devices
    Pen-based computing
    Desktop/portable company financials
    Workstations
    Environmentally-friendly computer technology

  STORAGE TECHNOLOGY
    Mass storage overview
      Floppy disk data storage
      Hard disk data storage
      RAID, Parallel disk systems
      Tape systems data storage
      Optical disk data storage
      SCSI boards & drivers
      Portable mass storage devices

  MISCELLANEOUS PERIPHERALS
    Scanners
    Computer visual display devices
      LCD displays
    Computer printers
      Color printers
      Low-end printing, ink & laser
    Input devices
    Peripheral device distribution

  HARDWARE COMPANIES
    Apple company watch
    DEC company watch
    HP company watch
    IBM company watch
    Intel company watch
    Motorola company watch


                 COMPUTER SOFTWARE

  INDUSTRY PRODUCT & BUSINESS OVERVIEW
    Business news (top 25 high-performance ISVs)
    Business news (top 25 desktop ISVs)
    International news on software
    Intellectual property
    Software business alliances
    Software distribution
    Lotus company watch
    Microsoft company watch
    Novell company watch

  OPERATING ENVIRONMENTS
    Microcomputer operating systems
      Micro operating systems market war
      Windowing environments & GUIs
      Windows NT
      OS/2
    UNIX
    Network operating systems
    High-performance computer operating systems
      IBM OS/400

  SYSTEM SOFTWARE
    Enterprise systems management software
      Software development management
      Network management
    Utility software

  DATABASE SOFTWARE
    Microcomputer-based DBMS software
    Large system DBMS software
    Object-oriented DBMS software
    Database servers
    Text & document management software

  APPLICATION DEVELOPMENT
    Application development software overview
      CASE & 4GL tools
      Microcomputer application development
                                     software
      Programming languages
      Natural language programming
      Object-oriented software technology
    Downsizing, reengineering & system integration

  SCIENTIFIC SOFTWARE
    CAD/CAM software
    Computer-aided engineering (CAE) software
    Modeling & simulation software
    Statistical & mathematical software

  CROSS-INDUSTRY SOFTWARE & APPLICATIONS
    Desktop application software overview
      Desktop publishing & presentation software
      Groupware
      Microcomputer financial software
      Spreadsheet software
      Word processing software
    Multiuser application software overview
      Large-system financial software
      Human resource & payroll software
      Sales & marketing software
      Customer service software
      Office automation software
      Text & document management software
      Executive information systems (EIS)
    Workflow software
    Geographic information systems (GIS)
    Project management software
    Transaction processing software

  INDUSTRY-SPECIFIC APPLICATIONS & SERVICES
    Finance, banking & insurance
    Insurance industry
    Manufacturing & distribution
      Computer-integrated manufacturing (CIM)
      Manufacturing software
      Robotics & data collection applications
    Wholesale, retail & distribution
    Telecom & datacom
    Healthcare
    Public sector
    Training services & software

  OPEN COMPUTING & EMERGING TECHNOLOGIES
    Client/server computing
    Distributed computing
    Open systems computing
    Middleware
    Artificial intelligence (AI)
    Neural networking & fuzzy logic

  INFORMATION SECURITY
    Information/data security

  DESKTOP PUBLISHING, GRAPHIC ARTS &
  IMAGING SOFTWARE
    Desktop publishing & presentation software
    Text & document management software
    Image manipulation & processing systems
    Document image management


          COMPUTER & INFORMATION SERVICES

  COMPUTER SERVICES OVERVIEW
    Computer professional services business news
    Downsizing, reengineering & system integration
    Computer professional services business
                                         alliances

  CROSS -INDUSTRY COMPUTER SERVICES
    Application development services
    Business process reengineering services
    Computer hardware maintenance services
    Comptuer outsourcing services
    Customer-service computer services
    Downsizing, smartsizing and rightsizing
    Image processing technology services
    Open computing technology services
    Systems integration services
    Training software & services

  INDUSTRY-SPECIFIC COMPUTER SERVICES
    Finance, banking & insurance
    Manufacturing & distribution
    Wholesale, retail & distribution
    Telecom/datacom
    Healthcare
    Public sector
    Other industries

  INFORMATION SERVICES & INTERACTIVE MEDIA
    Information services industry overview
      Electronic frontier & information
                              infrastructure
      Information services
        Telco information services
      Interactive media
      Broadband multimedia applications
        Interactive TV


                DATA COMMUNICATIONS

  LOCAL AREA NETWORKS (LANs)
    Network operating systems
    Network management
    Wireless LANs
    LAN hardware overview
      Hubs, repeaters & MAUs
      Ethernet, Toekn Ring
      FDDI

  WIDE AREA NETWORKS
    High-speed telecom services
    Wireless WANs
    WAN hardware overview
      Communication servers
      X.25
      High-speed datacom equipment
    Broadband network equipment

  ADVANCED DIGITAL TECHNOLOGIES
    Advanced digital technologies overview
      Asynchronous transfer mode (ATM)
      Frame relay
      ISDN
      SMDS
      SONET

  INTERNETWORKING
    SNA
    Middleware
    Internetworking hardware overview
      Bridges, routers & gateways
      FDDI

  WIRELESS NETWORKS
    Wireless datacom overview
      Wireless LANs
      Wireless WANs

  ASYNCHRONOUS CONNECTIVITY
    Asynchronous connectivity overview
      Modem hardware
      Modem communications software
        Remote access of LANs
      Fax/modem hardware & software
        Fax servers

  APPLICATION LAYER SOFTWARE
    Network management
    E-mail
    Groupware

  OPEN COMPUTING
    Client/server computing
    Distributed computing
    Electronic data interchange (EDI)
    Open systems computing middleware

  MISCELLANEOUS
    Network servers
    Terminal emulation products
    Electronic frontier & information
                             infrastructure
    Broadband multimedia applications


               IMAGING & MULTIMEDIA

  IMAGING HARDWARE
    Scanners
    Digital photography
    Visual display devices
      LCD printers
    Computer printers
      Color printers
      Low-end printing, ink & laser
      Image data handling subsystems & sofware
    Facsimile machines
    Copy machines

  DESKTOP PUBLISHING/GRAPHIC ARTS
    Desktop publishing hardware & software
      Desktop publishing & presentation software
      Image manipulation & processing
    Graphics/imaging workstations

  OTHER IMAGING TOPICS
    Document image managment
    Text & document management software
    Image recognition & conversion
    News about major imaging companies
    HDTV
    Adobe company watch
    Automated ID industry overview
      Automated ID industry business news
      Bar code & OCR technology

  MULTIMEDIA
    Multimedia-ready computers & devices
    CD-ROM & multimedia
    Sound & multimedia
    Video & multimedia
    Videoconferencing
    Virtual reality
    Interactive TV
    Miscellaneous multimedia
    Multimedia for the microcomputer
    Leading edge multimedia technology
    Broadband multimedia applications

  INTERACTIVE MEDIA
    Interactive media
      Interactive TV
    Electronic games


                  SEMICONDUCTORS

  BUSINESS & TECHNOLOGY OVERVIEWS
    Business news - top 25 firms
    Semiconductor legal issues
    Semiconductor economics
    Semiconductor technology

  SEMICONDUCTOR CATEGORIES
    Processors (CPUs)
    Digital signal processors (DSPs)
    Linear & mixed signal ICs
    Application-specific ICs (ASICs)
    Programmable logic devices (PLDs)
    Memory
    Flash memory
    Chip packages

  RELATED TOPICS
    Low-voltage chips
    Memory cards
    Semiconductor manufacturing equipment
    Board (PCB) manufacturing
    Diodes, transistors, capacitors & resistors
    Batteries
    Gallium arsenide

  SEMICONDUCTOR APPLICATIONS
    Central process unit (CPU) applications
    Digital signal processing (DSP) applications
    Semiconductors in PCs & peripherals
    Semiconductors in communications devices
    Semiconductors in graphic devices
    Semiconductors in automotive components


                TELECOMMUNICATIONS

  LONG DISTANCE TELECOMMUNICATIONS
    Interstate switched facilities
    Interstate private facilities
    Long distance telco business
    Enhanced long distance business services
    Federal System 2000

  LOCAL TELECOMMUNICATIONS
    Local basic services
    Local telco services
    Metropolitan area networks (MANs)

  INTERNATIONAL TELECOMMUNICATIONS
    International long distance
    International wireless telecom

  NETWORK & CENTRAL OFFICE EQUIPMENT
    Network & central office telecom
      Network equipment
      Network business

  CPE EQUIPMENT & SERVICES
    CPE telecom report
      PBX & key systems
      T1 channel bank
      Telemanagement and call centers
      CPE business
    High-speed datacom equipment

  WIRELESS TELECOMMUNICATIONS
    Cellular equipment
    Cellular services
    Wireless WANs
    Personal communications services
    Paging
    Two-way radio

  ADDITIONAL & ENHANCED SERVICES
    Caller ID
    Calling card
    800 & 900 services
    Enhanced long distance business services
    Pay telephone equipment & services
    Fax services
    Videoconferencing
    Voice processing
    Telco information services
    Broadband multimedia applications

  TELECOMMUNICATIONS REGULATION
    Local telco regulatory developments
    Long distance telco regulatory developments
    Wireless telecom regulatory developments
    Federal Communications Commission

  GENERAL TELEOCOM TRANSMISSION MEDIA
    Fiber optic transmission technology
    Mobile radio transmission techology
    Communications satellites

  MISCELLANEOUS TELECOM INTERESTS
    Regional Bell holding companies
    AT&T
    Credit card
    Cable TV infrastructure
    Interactive TV
    Information services
    Digital data services





inference engine
The processing program in an expert system.  It
derives a conclusion from the facts and rules
contained in the knowledge base using various
artificial intelligence techniques.



infix notation
The common way arithmetic operators are used to
reference numeric values.  For example, A+B/C is
infix notation.  Contrast with Polish notation and
reverse Polish notation.



Info Select
A popular personal information manager (PIM) for
PCs from Micro Logic Corporation, Hackensack, NJ,
that includes automatic phone dialing via modem.
It is noted for its exceptional ease of use and
ability to store random information and instantly
retrieve it in a very useful manner.  It is based
on an earlier product called Tornado designed by
Paul Mendelsohn and Micro Logic's Jim Lewis.



infopreneur
A person who is in business to gather and
disseminate electronic information.



InfoPump
Software from Trinzic Corporation, Palo Alto, CA,
that is used to synchronize data in different types
of databases by moving the data and converting it
to the destination format.  It supports Lotus Notes
documents, ASCII files, mainframe file formats and
most of the popular databases.  A Windows-based
client component controls the InfoPump Server.
Data movement can be performed on a scheduled or
event-driven basis.



informate
To dispense information, as coined by Harvard
Professor Shoshana Zuboff.



information
The summarization of data.  Technically, data are
raw facts and figures that are processed into
information, such as summaries and totals.  But
since information can also be raw data for the next
job or person, the two terms cannot be precisely
defined.  Both terms are used synonymously and
interchangeably.

   As office automation and data processing merge,
it may be more helpful to view information the way
data is defined and used, namely: data, text,
spreadsheets, pictures, voice and video.  Data are
discretely defined fields.  Text is a collection of
words.  Spreadsheets are data in matrix (row and
column) form.  Pictures are lists of vectors or
frames of bits.  Voice is a continuous stream of
sound waves.  Video is a sequence of frames.

   Future databases will routinely integrate all
these forms of information.



information appliance
A type of future home or office device that can
transmit to or plug into common public or private
networks.  Envisioned is a "digital highway," like
telephone and electrical power networks.



information center
The division within the IS department that supports
end-user computing.  Responsible for training users
in applications and solving related personal
computer problems.



information engineering
An integrated set of methodologies and products
used to guide and develop information processing
within an organization.  It starts with enterprise-
wide stategic planning and ends with running
applications.



information hiding
Keeping details of a routine private.  Programmers
only know what input is required and what outputs
are expected.  See encapsulation and data
abstraction.



information highway
See information superhighway.



information industry
(1) Organizations that publish information via
online services or through distribution by diskette
or CD-ROM.

(2) All computer, communications and electronics-
related organizations, including hardware, software
and services.



Information Industry Association
See IIA.



information management
The discipline that analyzes information as an
organizational resource.  It covers the
definitions, uses, value and distribution of all
data and information within an organization whether
processed by computer or not.  It evaluates the
kinds of data/information an organization requires
in order to function and progress effectively.

   Information is complex because business
transactions are complex.  It must be analyzed and
understood before effective computer solutions can
be developed.  See data administration.



information processing
Same as data processing.



information requirements
The information needed to support a business or
other activity.  Requirements are typically defined
as lists of detailed items as well as summarized
data from business transactions, such as orders and
purchases, and master records, such as customers
and vendors.  How frequently this information must
be made available is also part of the requirement.

   Information requirements (the what and when) are
turned into functional specs (the how) of an
information system by systems analysts.   The
information is defined as a collection of data
elements that are obtained by running query and
report programs against a particular database or
group of databases.  The data and information that
is stored in the databases in the first place is
also derived from the information requirements.
See functional specification.



information resource management
See Information Systems and information management.



information science
See information management.



information service
Any information retrieval, publishing, timesharing
or BBS facility.  See online services.



Information Services
See Information Systems.



information superhighway
The telecommunications infrastructure within the
U.S. that will allow access to government, industry
and educational data banks for all people.  While
many envision a single high-speed link to and from
every house in America, this is not feasible for
many years.  More likely is an interlinking of
existing capabilities via local telephone, cable
TV, satellite and online service providers.  Also,
rather than one type of receiver, many types of
devices will hook into this superhighway, including
TVs with the appropriate adapters, personal
computers and PDAs (personal digital assistants).

   The Internet has become synonymous with the
information superhighway, because it provides an
enormous source of information that is available to
the public.  However, universal, dial-up access to
the Internet is not without charge, and it was
never designed to be a high-speed link into
everyone's home.  It may serve as a backbone for
the information superhighway, or it may serve only
as a prototype for a real information superhighway
in the future.

   Various bills for altering U.S. communications
laws have been proposed that allow telephone and
cable companies to enter each other's markets.
Some telephone companies have already ventured into
new markets, challenging existing laws.  Stay
tuned!



information system
A business application of the computer.  It is made
up of the database, application programs, manual
and machine procedures and encompasses the computer
systems that do the processing.

   The database stores the subjects of the business
(master files) and its activities (transaction
files).  The application programs provide the data
entry, updating, query and report processing.  The
manual procedures document how data is obtained for
input and how the system's output is distributed.
Machine procedures instruct the computer how to
perform the batch processing activities, in which
the output of one program is automaticaly fed into
another program.

   The daily processing is the interactive,
realtime processing of the transactions.  At the
end of the day or other period, the batch
processing programs update the master files that
have not been updated since the last cycle.
Reports are printed for the cycle's activities.

   The periodic processing of an information system
is the updating of the master files, which adds,
deletes and changes the information about
customers, employees, vendors and products.


         Relationships Between Systems

    STRUCTURE (is)           FUNCTION (does)

 Management system
                       Sets organization's goals
   1.  PEOPLE          and objectives, strategies
   2.  MACHINES        and tactics, plans,
                       schedules and controls
 Information system
                       
   1. DATABASE          Defines data structures
   2. APPLICATION       Data entry, updating,
       PROGRAMS          queries and reporting
   3. PROCEDURES        Defines data flow
                       
 Computer system
                       
   1. CPU                Processes (The 3 C's)
   2. PERIPHERALS        Store and retrieve
   3. OPERATING SYSTEM   Manages computer system





Information Systems
The formal title for a data processing, MIS, or IS
department.  Other titles are Data Processing,
Information Processing, Information Services,
Management Information Systems, Management
Information Services and Information Technology.



Information Technology Association of America
See ITAA.



information theory
The study of encoding and transmitting information.
From Claude Shannon's 1938 paper, "A Mathematical
Theory of Communication," which proposed the use of
binary digits for coding information.



information utility
(1) A service bureau that maintains up-to-date
databases for public access.

(2) A central source of information for an
organization or group.



information warehouse
The collection of all databases in an enterprise
across all platforms and departments.



INFORMIX
A relational database management system (DBMS) from
Informix Software, Inc., Menlo Park, CA, that runs
on most UNIX platforms, including SCO UNIX for x86
machines and NetWare.  Development tools from
Informix include INFORMIX-4GL, a fourth-generation
language, and INFORMIX-New Era, a client/server
development system for Windows clients that
supports INFORMIX and non-INFORMIX databases.



infoware
Information sold electronically, such as the
electronic versions of this database.



InfoWindow
The trade name for IBM display screens.



infrared
An invisible band of radiation at the lower end of
the electromagnetic spectrum.  It starts at the
middle of the microwave spectrum and goes up to the
beginning of visible light.  Infrared transmission
requires an unobstructed line of sight between
transmitter and receiver.  It is used for wireless
transmission between computer devices as well as
most all hand-held remotes for TVs, video and
stereo equipment.  Contrast with ultraviolet.  See
SIR.



infrastructure
The fundamental structure of a system or
organization.  The basic, fundamental architecture
of any system (electronic, mechanical, social,
political, etc.) determines how it functions and
how flexible it is to meet future requirements.



Ingres
See CA-OpenIngres.



inheritance
In object-oriented programming, the ability of one
class of objects to inherit properties from a
higher class.



inhouse
An operation that takes place on the user's
premises.



INIT
(INITiate)  A Macintosh routine that is run when
the computer is started or restarted.  It is used
to load and activate drivers and system routines.
Many INITs are memory resident and may conflict
with each other like TSRs in the PC environment.



initial program load
See IPL.



initialization string
Same as setup string.



initialize
To start anew, which typically involves clearing
all or some part of memory or disk.



ink jet
A printer mechanism that sprays one or more colors
of ink onto paper and produces high-quality
printing like that of a laser printer.

   The continuous stream method produces droplets
that are aimed onto the paper by electric field
deflectors.

   The drop-on-demand method uses a set of
independently controlled injection chambers, the
newest of which use solid ink developed by Exxon in
1983.  Solid ink liquefies quickly when heated and
solidifies instantly when it reaches the paper.



INMARSAT
(INternational MARitime SATellite)  An
international organization involved in providing
satellite communications to and from ships and
offshore rigs.  It is represented in the U.S. and
partially owned by COMSAT.



inner join
See join.



innoculate
To store characteristics of an executable program
in order to detect a possible unknown virus if the
file is changed.



input
(1) Data that is ready for entry into the computer.

(2) To enter data into the computer.



input area
A reserved segment of memory that is used to accept
data from a peripheral device.  Same as buffer.



input device
A peripheral device that generates input for the
computer such as a keyboard, scanner, mouse or
digitizer tablet.



input/output
See I/O.



input program
Same as data entry program.



input queue
A reserved segment of disk or memory that holds
messages that have been received or job control
statements describing work to be done.



input stream
A collection of job control statements entered in
the computer that describe the work to be done.



inquiry program
Same as query program.



Ins key
(INSert key)  A keyboard key that is used to switch
between insert and overwrite mode or to insert an
object at the current cursor location.



insert mode
A data entry mode that causes new data typed on the
keyboard to be inserted at the current cursor
location on screen.  Contrast with overwrite mode.



insomnia
The inability to sleep.  If you suffer from it, the
solution is to look up and read "standards &
compatibility."  Dozing should occur shortly.  If
it doesn't work, well, at least you'll become a
computer guru!



install program
Also called a setup program, it is a program that
prepares an application (software package) to run
in the computer.  It creates a default directory or
folder on the hard disk and copies the files from
the distribution diskettes to the hard disk.  It
decompresses them if they are distributed in a
compressed format.

   Install programs may analyze the computer's
current environment and/or ask the user to identify
components in order to link in the appropriate
software drivers required to display and print
properly.

   An install program may also be used to activate
new hardware by setting or resetting parameters in
an updatable memory (flash memory, EEPROM, etc.) on
the expansion board.  It is often used to identify
resource requirements when installing a new
peripheral, such as IRQs and I/O addresses (see PC
conflicts).

   During installation, a component of the install,
or setup, program is often copied to and left on
the hard disk to allow the user to make additional
changes to the application or hardware at a later
time.  See how to install a program and CMOS RAM.



installation conflicts
See PC conflicts.



installation spec
Documentation from an equipment manufacturer that
describes how a product should be properly
installed within a physical environment.



instance
In object-oriented programming, a member of a
class; for example, "Lassie" is an instance of the
class "dog."  When an instance is created, the
initial values of its instance variables are
assigned."



instance variable
In object-oriented programming, the data in an
object.



instant print
The ability to use the computer as a typewriter.
Each keystroke is transferred to the printer.



instantiate
In object-oriented programming, to create an object
of a specific class.  See instance.



Institute for Certification
See ICCP.



instruction
(1) A statement in a programming language.

(2) A machine instruction.



instruction cycle
The time in which a single instruction is fetched
from memory, decoded and executed.  The first half
of the cycle transfers the instruction from memory
to the instruction register and decodes it.  The
second half executes the instruction.



instruction mix
The blend of instruction types in a program.  It
often refers to writing generalized benchmarks,
which requires that the amount of I/O versus
processing versus math instructions, etc., reflects
the type of application the benchmark is written
for.



instruction register
A high-speed circuit that holds an instruction for
decoding and execution.



instruction repertoire
Same as instruction set.



instruction set
The repertoire of machine language instructions
that a computer can follow (from a handful to
several hundred).  It is a major architectural
component and is either built into the CPU or into
microcode.  Instructions are generally from one to
four bytes long.



instruction time
The time in which an instruction is fetched from
memory and stored in the instruction register.  It
is the first half of the instruction cycle.



insulator
A material that does not conduct electricity.
Contrast with conductor.



int
A programming statement that specifies an interrupt
or that declares an integer variable.  See
interrupt and integer.



int 13
A DOS interrupt used to activate disk functions,
such as seek, read, write and format.



int 14
A DOS interrupt used to activate functions on the
serial port (COM1, COM2, etc.).  See NASI.



int 21
A multipurpose DOS interrupt used for various
functions including reading the keyboard and
writing to the console and printer.  It was also
used to read and write disks using the earlier File
Control Block (FCB) method.



integer
A whole number.  In programming, the integer
function would yield 123 from 123.898.



Integer BASIC
Apple's version of BASIC for the Apple II that
handles only fixed point numbers (non-floating
point).  Due to its speed, many games are written
in it.



integrated
A collection of distinct elements or components
that have been built into one unit.



integrated CASE
See I-CASE.



integrated circuit
The formal name for chip.



integrated development environment
See IDE.



integrated drive electronics
See IDE.



integrated injection logic
A type of bipolar transistor design known for its
fast switching speeds.



integrated software package
Software that combines several applications in one
program, typically database management, word
processing, spreadsheet, business graphics and
communications.  Such programs (Microsoft Works,
AppleWorks, etc.) provide a common user interface
for their applications plus the ability to cut and
paste data from one to the other.

   User interfaces, such as found on the Macintosh
and Windows, provide this capability with all
applications written for their environments.



integrator
In electronics, a device that combines an input
with a variable, such as time, and provides an
analog output; for example, a watt-hour meter.



integrity
See data integrity.



Intel
(Intel Corporation, Santa Clara, CA)  A leading
manufacturer of semiconductor devices founded in
1968 by Bob Noyce and Gorden Moore in Mountain
View, CA.  A year later it introduced its first
product, a 64-bit bipolar static RAM chip.  By
1971, its very successful memory chips began to
obsolete magnetic core storage.

   Intel is known for its x86 microprocessor
family, but it also developed the first
microprocessor in 1971.  In response to a
calculator chip order from Japanese manufacturer
Busicom, Intel engineer Marcian E. "Ted" Hoff
decided it would make more sense to design a
general-purpose machine.  The resulting 4004 chip
was the world's first microprocessor.

   Over the years, Intel has developed a wide
variety of chips and board-level products,
including the MULTIBUS bus used in industrial
applications.  Intel started with 12 people and its
first year revenues were less than three thousand
dollars.  In 1993, it had nearly 30,000 employees
with revenues close to nine billion.



Intellect
A natural language query program from Trinzic
Corporation, Palo Alto, CA, that runs on IBM
mainframes and other computers.  It was originally
developed by Artificial Intelligence Corporation,
which merged into Trinzic.



Intellifont
A scalable font technology from Agfa CompuGraphic.
Intellifont typefaces are built into LaserJet IIIs
and 4s (see LaserJet).  The Intellifont for Windows
font scaler creates matching screen fonts for
Windows from Intellifont and compatible typefaces.



intelligence
Processing capability.  Every computer is
intelligent!


intelligent cable
Same as smart cable.



intelligent controller
A peripheral control unit that uses a built-in
microprocessor for controlling its operation.



intelligent database
A database that contains knowledge about the
content of its data.  A set of validation criteria
are stored with each field of data, such as the
minimum and maximum values that can be entered or a
list of all possible entries.  See DBMS
(Intelligent Databases).



intelligent form
A data entry application that provides help screens
and low levels of AI in aiding the user to enter
the correct data.



intelligent hub
A central connecting device in a network that
performs a variety of processing functions such as
network management, bridging, routing and
switching.  Contrast with passive hub and active
hub.  See hub.



intelligent modem
A modem that responds to commands and can accept
new instructions during online transmission.  It
was originally developed by Hayes.



intelligent paper
Same as intelligent form.



intelligent terminal
A terminal with built-in processing capability, but
no local disk or tape storage.  It may use a
general-purpose CPU or may have specialized
circuitry as part of a distributed intelligence
system.  Contrast with dumb terminal.



IntelliSense
Features in Microsoft applications that help the
user by making decisions automatically.  By
analyzing activity patterns, the software can
derive the next step without the user having to
explicitly state it.  Automatic typo correction and
suggesting shortcuts also fall under the
IntelliSense umbrella.



INTELSAT
(INternational TELecommunications SATellite)  An
international organization involved in launching
and operating commercial satellites.  It was
created in 1964 with only 11 countries
participating.  Today, over 100 nations have
ownership.  It is represented in the U.S. and
partially owned by COMSAT.



inter
To cross over boundaries; for example, internetwork
means from one network to another.  Contrast with
intra.



interactive
Back-and-forth dialog between the user and a
computer.



interactive cable TV
See interactive TV.



interactive fiction
An adventure game that has been created or modified
for the computer.  It has multiple story lines,
environments and endings, all of which are
determined by choices the player makes at various
times.



Interactive Multimedia Association
See IMA.



interactive session
Back-and-forth dialogue between user and computer.
Contrast with batch session.



interactive TV
Two-way communications between the TV viewer and
service providers.  Using phone lines, cable,
optical fiber or satellite, services include home
shopping, movies on demand, interactive
participation in live broadcasts as well as access
to news, databases and other networks.

   Current analog TV sets can be connected to boxes
that add dial out capability via modem and phone
line as well as handle digital signals interleaved
with the incoming analog signals.  As cable systems
become more digital, more interactive programming
will be provided.  See digital convergence.



Interactive UNIX
A UNIX-based operating system from SunSoft that
runs on x86 machines.  It has been widely used to
connect character-based terminals or process
control devices, such as bar code readers in a
supermarket, to a central computer.



interactive video
The use of CD-ROM and videodisc controlled by
computer for an interactive education or
entertainment program.  See CD-ROM and videodisc.



InterBase
A relational DBMS from Borland that runs on UNIX
workstations and VAXes, designed to handle online
complex processing (OLCP).  It can be a peer-to-
peer or client/server system and uses SQL plus its
own data manipulation language.



interblock gap
Same as interrecord gap.



interesting stuff
See Lessons Slang & interesting stuff.



interexchange carrier
See IXC.



interface
The connection and interaction between hardware,
software and the user.

   Hardware interfaces are the plugs, sockets,
wires and the electrical pulses travelling through
them in a particular pattern.  Also included are
electrical timing considerations.  Examples are RS-
232 transmission, the Ethernet and Token Ring
network topologies and the IDE, ESDI, SCSI, ISA,
EISA and Micro Channel interfaces.

   Software, or programming, interfaces are the
languages, codes and messages programs use to
communicate with each other and to the hardware. 
Examples are the applications that run under the
Mac, DOS and Windows operating systems as well as
the SMTP e-mail and LU 6.2 communications
protocols.

   User interfaces are the keyboards, mice,
commands and menus used for communication between
you and the computer.  Examples are the command
lines in DOS and UNIX and the Mac, Windows and
Motif graphical interfaces.

   Interfacing is a major part of what engineers,
programmers and consultants do.  Users "talk to"
the software.  The software "talks to" the hardware
and other software.  Hardware "talks to" other
hardware.  All this is interfacing.  It has to be
designed, developed, tested and redesigned, and
with each incarnation, a new specification is born
that may become yet one more de facto or regulated
standard.


                 Format & Function
Every interface implies a structure.  Electrical
signals are made up of voltage levels, frequencies
and duration.  The data passed from one device or
program to another has a precise format (header,
body, trailer, etc.).

   Every interface implies a function.  At the
hardware level, electronic signals activate
functions; data is read, written, transmitted,
received, analyzed for error, etc.  At the software
level, instructions activate the hardware (access
methods, data link protocols, etc.).  At higher
levels, the data transferred or transmitted may
itself request functions to be performed
(client/server, program to program, etc.).


              Language & Programming
An interface is activated by programming language
commands.  The complexity of the functions and the
design of the language determine how difficult it
is to program.


       User Interface, Protocol, API and ABI
The design of the interaction between the user and
the computer is called a user interface.  The
rules, formats and functions between components in
a communications system or network is called a
protocol.  The language and message formats between
routines within a program or between software
components is called an API.  The specification for
an operating system working in a specific machine
environment is called an ABI.

   All the above interactions are interfaces.
Regardless of what they're called, they all create
rules that must be precisely followed in a digital
world.



interface adapter
In communications, a device that connects the
computer or terminal to a network.



interface designer
See GUI builder.



interframe coding
In video compression, coding only the differences
between frames.  See intraframe coding.



interlaced
Illuminating a CRT by displaying odd lines and then
even lines (every other line first; then filling in
the gaps).  TV signals are interlaced and generate
60 half frames (30 full frames) per second.
Computer display systems may also be interlaced,
but usually only at the highest resolution.

   Rather than send every line of information to
the screen (non-interlaced), interlacing sends half
the information in the same time frame, thus
requiring less-complicated and less-expensive
circuits.

   TV's constant animation has always provided
acceptable viewing using the interlaced method,
although reading a still image on TV is not all
that pleasing.  Interlaced screens used on
computers can provide an annoying flicker that
causes headaches and eye strain (see below).


      Interlaced       Non-interlaced
   1      
   2      
   3      
   4      
   5      



               Where's the Flicker?
When you purchase a video display adapter and
monitor, the interlaced vs non-interlaced issue
comes up when you get into the highest resolution
mode.  For example, most VGA adapters and monitors
support the following three resolutions: 640x480,
800x600 and 1024x768.  Advanced models support
1280x1024 and higher.

   The lower resolutions (640x480 and 800x600) are
usually non-interlaced, but the highest mode
1024x768 or 1280x1024 may be interlaced.  When you
start up under DOS, you are always at the lowest,
non-interlaced 640x480 resolution.  It's only when
you get into Windows or AutoCAD that the high-
resolution drivers, supplied with the graphics
adapter, are able to activate the higher modes.

   An interlaced resolution does not cause flicker
like a badly-synchronized movie projector.  Rather
it provides a faint overall flutter that is often
very noticeable on the entire screen and especially
on tiny, complex graphic elements such as buttons
and icons.

   A related issue is the vertical scan frequency,
or the number of times the entire screen is
refreshed per second.  Since the refresh rate may
go down as resolution goes up, this is another
consideration.  The number can range from 45 to
over 100; however, 60 is the smallest refresh
generally tolerable, and 70 and higher is
recommended.

   For CAD and destop publishing, a non-interlaced
1280x1024 or higher resolution with a 70Hz refresh
rate on a 21" monitor is recommended.  Depending on
the size of the page you are working with, a non-
interlaced 1024x768 resolution on a 17" screen may
suffice.

   The high resolutions required to see full pages
and facing pages of text provide enough strain on
the eyes.  Interlaced screens and low refresh rates
only add to the burden.





Interleaf
Desktop publishing software for DOS and a variety
of UNIX-based computers from Interleaf, Inc.,
Waltham, MA.  The Windows version is expected in
the fall of 1994.  Interleaf is a full-featured
program that supports a large number of document
and image types.  It is used for creating compound
documents as well as extremely long documents
(hundreds of thousands of pages).

   It includes built-in word processing and
graphics tools and provides a number of optional
components for enhanced document control and
workgroup operation.  Interleaf used to be known as
Interleaf TPS (Technical Publishing Software).  In
1990, it became Interleaf5, later Interleaf6, etc.

   Interleaf RDM (Relational Document Manager) is
another product that provides distribution and
tracking of documents.  Interleaf WorldView
provides runtime viewing with customizable searches
for Interleaf and other document types.



interleave
See sector interleave and memory interleaving.



interlock
A device that prohibits an action from taking
place.



intermediate language
Same as pseudo language.



intermediate node routing
Routing a message to non-adjacent nodes; for
example, if three computers are connected in series
A--B--C, data transmitted from A to C can be routed
through B.



intermittent error
An error that occurs sporadically, not
consistently.  It is the most difficult type of
problem to diagnose and repair.



internal bus
A data pathway between closely-connected
components, such as between the CPU and memory.
See local bus.



internal command
In DOS and OS/2, a command, such as Copy, Dir and
Rename, which may be used at all times.  Internal
commands are executed by the command processor
programs COMMAND.COM in DOS and CMD.EXE in OS/2.
The command processor is always loaded when the
operating system is loaded.  Contrast with external
command.



internal font
A set of characters for a particular typeface that
is built into a printer.  Contrast with font
cartridge and soft font.



internal interrupt
An interrupt that is caused by processing, for
example, a request for input or output or an
arithmetic overflow error.  Contrast with external
interrupt.



internal modem
A modem that plugs into an expansion slot within
the computer.  Unlike an external modem, an
internal modem does not provide a series of display
lights that inform the user of the changing modem
states.  The user must rely entirely on the
communications program.  Contrast with external
modem.



internal sort
Sorting that is accomplished entirely in memory
without using disks or tapes for temporary files.



Internal stack failure
A DOS error message that means DOS has gotten
completely confused.  Turn off the computer and
restart.



internal storage
Same as memory.



International Data Corporation
See IDC.



International Electrotechnical Commission
See IEC.



International Federation of Information Processing
See IFIP.



International Standards Organization
See ISO.



International Telecommunications Union
See ITU-TSS.



Internaut
A person that uses the Internet.



internet
(1) A large network made up of a number of smaller
networks.

(2) (Internet)  "The" Internet is made up of
thousands of interconnected networks in over 70
countries, comprised of academic, commercial,
government and military networks.  As of the end of
1994, an estimated 30,000 networks are on the
Internet, and this number is expected to double
each year.

   Originally developed for the military, much of
the Internet today is used for academic and
commercial research.  Users have access to
unpublished data, journals and BBSs.  It is also
widely used as a worldwide electronic mail system.
E-mail connection to the Internet is available
through online services such as CompuServe, BIX and
America Online.  DELPHI is the first online service
to provide full Internet access, not just e-mail.

   Internet computers use the TCP/IP communications
protocol.  There are over two million hosts on the
Internet, a host being a mainframe, mini or
workstation that directly supports the Internet
Protocol (the IP in TCP/IP).  The Internet is
connected to all types of computer networks
worldwide via gateways that convert TCP/IP into
other protocols.

   Some of the major utilities used to work the
Internet are FTP, Archie, Telnet, Gopher and
Veronica.  FTP stands for File Transfer Protocol.
There are countless files throughout the Internet
that can be downloaded free of charge using FTP.
Archie is a utility that provides listings of these
files.

   Telnet is a terminal emulation program that lets
you log onto a computer in the Internet and run a
program.  Gopher is a utility that lets you search
hierarchical menus describing Internet files (not
just file names), and Veronica lets you make more
sophisticated searches on Gopher sites.  See FTP,
Archie, Telnet, Gopher and Veronica.

   The IAB, or Internet Activities Board is the
governing body for the Internet.  Its Internet
Research Task Force (IRTF) explores new
technologies which it refers to the Internet
Engineering Task Force (IETF).  The IETF works on
the specifications of new standards.

   To obtain a list of organizations that provide
access to the Internet, see PDIAL.  See Lessons
Internet, information superhighway and online
services.

                 Getting Started?
For a list of good books on the Internet, see
Internet references.





Internet access
See Internet address and PDIAL.



Internet address
The format for addressing a message to an Internet
user is
           recipient@location.domain

   For example, the address of the Free Software
Foundation is gnu@prep.ai.mit.edu, which means
transmitting to the GNU mailbox via nodes PREP, AI
and MIT.  The suffix at the end is the domain, or
host classification, in this case EDU (see below).


                Internet Domains

         com - business (commercial)
         edu - educational and research
         gov - government
         mil - military agency
         net - gateway or host
         org - other organization



                  Via CompuServe
If you are a CompuServe subscriber, you can access
the Internet by adding the >internet: prefix to the
Internet address.  For example, to send mail from
CompuServe to the Free Software Foundation address
mentioned above, you would address the message to:

         >internet:gnu@prep.ai.mit.edu


   To reach a CompuServe user from the Internet,
change the comma in the CompuServe account number
to a period.  For example, if the CompuServe number
is 71022,1560, the Internet e-mail address is
71022.1560@compuserve.com.


          To Send Mail to Other Services
If you know your recipients' "online names" and
which services they use, you can send messages
directly to their mailboxes via the Internet.  For
example, if the recipient's e-mail name is
lmorrison, you would address the message to the
following services.  If the name is "l morrison,"
remove the blanks.

    lmorrison@aol.com           America Online

    lmorrison@genie.geis.com    GEnie

    lmorrison@mcimail.com       MCI Mail

    lmorrison@prodigy.com       PRODIGY

    lmorrison@delphi.com        DELPHI



           To Obtain an Internet Address
To obtain an Internet network address and reserve a
domain name, organizations must register with the
InterNIC Registration Service.  See InterNIC.

   See also IP address for information about the
physical structure of an Internet address.





Internet gateway
A computer system that converts messages back and
forth between TCP/IP and other protocols.  Internet
gateways connect the Internet to all the other
communications networks in the world.



Internet Protocol
See Internet and TCP/IP.



Internet references
A well-written and excellent book for people
getting started on the Internet is "Internet Slick
Tricks" by Alfred and Emily Glossbrenner, published
by Random House, ISBN 0-679-75611-6.

   Another book by Alfred Glossbrenner, but more in
depth is "Internet 101," published by McGraw-Hill,
ISBN 0-07-024054-X.  While aimed at the college
market, this is a must-have for anyone interested
in the Internet.  Glossbrenner is a superb author.

   To learn what information is available on the
Internet, read "Internet Yellow Pages" by Harley
Hahn and Rick Stout, published by Osborne McGraw-
Hill, ISBN 007-882023-5.

   Joshua Eddings' "How the Internet Works,"
published by Ziff-Davis Press, ISBN 1-56276-192-7,
provides a delightful and colorful guide to the
inner-workings of the Internet.





InterNet Router
Macintosh software from Apple that internetworks
different access methods (LocalTalk, EtherTalk,
TokenTalk, etc.) and can reside in any network
station.  Each Router can connect up to eight
networks with a maximum of 1,024 networks and 16
million nodes.



Internet utility
Software used to search the Internet for specific
information.  See Archie, Gopher, Veronica, WAIS
and WWW.



internetwork
To go between one network and another.



InterNIC
(NFSnet Network Information Center)  The source for
Internet information and registration.  It was
formed in 1993 by agreements with the National
Science Foundation, General Atomics, AT&T and
Network Solutions Inc.

   Internet network addresses and domain names are
assigned by InterNIC Registration Services, which
is administered by Network Solutions Inc. of
Herndon, VA.

   For general information about InterNIC services,
call the automated hotline at 619/455-4600.  Send
an e-mail request to info@is.internic.net.



interoperable
The ability for one system to communicate or work
with another.



interpolate
To estimate values that lie between known values.



Interpress
A page description language from Xerox used on the
2700 and 9700 page printers (medium to large-scale
laser printers).  Ventura Publisher provides output
in Interpress.



interpret
To run a program one line at a time.  Each line of
source language is translated into machine language
and then executed.



interpreter
A high-level programming language translator that
translate and runs the program at the same time.
It translates one program statement into machine
language, executes it, then proceeds to the next
statement.  This differs from regular executable
programs that are presented to the computer as
binary-coded instructions.  Interpreted programs
remain in the same source language format the
programmer wrote in: as text files, not machine
language files.

   Interpreted programs run slower than their
compiler counterparts.  Whereas the compiler
translates the entire program before it is run,
interpreters translate a line at a time while the
program is run.  However, it is very convenient to
write an interpreted program, since a single line
of code can be tested interactively.

   Interpreted programs must always be run with the
interpreter.  For example, in order to run a BASIC
or dBASE program, the BASIC or dBASE interpreter
must be in the target computer.

   If a language can be both interpreted and
compiled, a program may be developed with the
interpreter for ease of testing and debugging and
later compiled for production use.



interpretive language
A programming language that requires an interpreter
to run it.



interprocess communication
See IPC.



interrecord gap
The space generated between blocks of data on tape,
created by the starting and stopping of the reel.



interrogate
(1) To search, sum or count records in a file.  See
query.

(2) To test the condition or status of a terminal
or computer system.



interrupt
A signal that gets the attention of the CPU and is
usually generated when I/O is required.  For
example, hardware interrupts are generated when a
key is pressed or when the mouse is moved.
Software interrupts are generated by a program
requiring disk input or output.

   An internal timer may continually interrupt the
computer several times per second to keep the time
of day current or for timesharing purposes.

   When an interrupt occurs, control is transferred
to the operating system, which determines the
action to be taken.  Interrupts are prioritized;
the higher the priority, the faster the interrupt
will be serviced.



interrupt-driven
A computer or communications network that uses
interrupts.



interrupt latency
The time it take to service an interrupt.  It
becomes a critical factor when servicing realtime
functions such as a communications line.  See UART
overrrun.



interrupt mask
An internal switch setting that controls whether an
interrupt can be processed or not.  The mask is a
bit that is turned on and off by the program.



interrupt priorities
The sequence of importance assigned to interrupts.
If two interrupts occur simultaneously, the
interrupt with the highest priority is serviced
first.  In some systems, a higher-priority
interrupt can gain control of the computer while
it's processing a lower-priority interrupt.



Interrupt Request
See IRQ.



interrupt vector
In the PC, one of 256 pointers that reside in the
first 1KB of memory.  Each vector points to a
routine in the ROM BIOS or elsewhere in memory,
which handles the interrupt.



intersect
In a relational database, to match two files and
produce a third file with records that are common
in both.  For example, intersecting an American
file and a programmer file would yield American
programmers.



intra
Within a boundary; for example, intraoffice refers
to operations that take place within the office.
Contrast with inter.



intraframe coding
Compressing redundant areas within a video frame.
See interframe coding.



Invalid directory
A DOS error message that means you entered the name
of a directory that does not exist.



Invalid drive specification
A DOS error message.  If you get this message on a
valid drive such as C:, it may mean that your hard
disk has become corrupted.  See DOS Mirror.



Invalid file name or file not found
A DOS error message.  You have probably used an
invalid character in a DOS file name, or you have
used wild cards when they are not applicable.  For
example, type *.* will produce this error, because
you cannot Type more than one file at a time.



Invalid media type
A DOS error message that means DOS doesn't
recognize the format of the drive being referenced.
The disk has been corrupted in some manner and is
not readable.  You will also get this message if
you low-level formatted a new disk, performed the
Fdisk procedure, but forgot to high-level format it
with the Format command.



invalid parameter
A DOS error message that means DOS doesn't
understand the command line.  It indicates that a
switch is used incorrectly.  If you're typing path
names, be sure to use a backslash (\), not a
forward slash (/).  The forward slash is used to
enter parameters (see DOS switch and DOS abc's).



inverse multiplexing
Splitting a high-speed channel into several low-
speed channels in order to be able to use available
transmission facilities.  For example, an inverse
multiplexor is used to transmit high-speed LAN
traffic over leased digital lines (T-carrier),
which are made up of several lower-speed channels.
See DS.



inverse video
Same as reverse video.



inverted file
In data management, a file that is indexed on many
of the attributes of the data itself.  For example,
in an employee file, an index could be maintained
for all secretaries, another for managers.  It's
faster to search the indexes than every record.
Inverted file indexes use lots of disk space;
searching is fast, updating is slower.



inverted list
Same as inverted file.



inverter
(1) A logic gate that converts the input to the
opposite state for output.  If the input is true,
the output is false, and vice versa.  An inverter
performs the Boolean logic NOT operation.

(2) A circuit that converts DC current into AC
current.  Contrast with rectifier.



invoke
To activate a program, routine, function or
process.



IO.SYS
See MSDOS.SYS.



IOCA
(Image Object Content Architecture)  See MO:DCA.



IOCS
(Input Output Control System)  An early,
rudimentary IBM operating system (1950s).  It was a
set of I/O routines for tapes and disks.  Today's
counterpart in the PC is the ROM BIOS.



ion deposition
A printing technology used in high-speed page
printers.  It is similar to laser printing, except
instead of using light to create a charged image on
a drum, it uses a printhead that deposits ions.
After toner is attracted to the ions on the drum,
the paper is pressed directly against the drum
fusing toner to paper.

   Quality approaches that of a laser printer;
however, the ink has not been embedded as deeply,
and the paper can smear more easily.



IOS
(Integrated Office System)  See office automation.



IP
(1) (Internet Protocol)  The IP part of the TCP/IP
protocol, which routes a message across networks.
See TCP/IP, datagram and IP address.

(2) See image processing.



IP address
(Internet Protocol address)  The physical address
of a TCP/IP packet uses 32 bits to contain a
network address and host address, known as the
netid and hostid.  The 32 bits are divided
differently according to the class of the address,
which is based on the number of hosts that can be
attached to the network.  Thus, the more bits used
for host address, the fewer remain for the network
address.  The addresses support the following
number of networks and hosts.

       Class     Networks     Hosts
         A        128          16M
         B         16K         65K
         C         16M        256


   Network addresses are supplied to organizations
by the InterNIC Registration Service.  See
InterNIC.  See also CIDR.



IPC
(InterProcess Communication)  The exchange of data
between one program and another either within the
same computer or over a network.  It implies a
protocol that guarantees a response to a request.
Examples are OS/2's Named Pipes, Windows' DDE,
Novell's SPX and Macintosh's IAC.

   IPCs are performed automatically by the
programs.  For example, a spreadsheet program could
query a database program and retrieve data from one
of its databases.  A manual example of an IPC
function is performed when users cut and paste data
from one file to another using the clipboard.



IPDS
(Intelligent Printer Data Stream)  An IBM format
for sending full pages of text and graphics from a
mainframe or mini to a laser printer.



IPI
(Intelligent Peripheral Interface)  A high-speed
hard disk interface used with minis and mainframes
that transfers data in the 10 to 25 MBytes/sec
range.  IPI-2 and IPI-3 refer to differences in the
command set that they execute.   See hard disk.



IPL
(Initial Program Load)  Same as boot.



IPng
(IP Next Generation)  An enhanced Internet Protocol
developed by the Internet Engineering Task Force
(IETF).  IPng improves data security and increases
the Internet address from four to 16 bytes,
providing for an unlimited number of networks and
systems.



ips
(Inches Per Second)  The measurement of the speed
of tape passing by a read/write head or paper
passing through a pen plotter.



IPX
(Internet Packet EXchange)  A NetWare
communications protocol used to route messages from
one node to another.  IPX packets include network
addresses and can be routed from one network to
another.  An IPX packet can occasionally get lost
when crossing networks, thus IPX does not guarantee
delivery of a complete message.  Either the
application has to provide that control or
NetWare's SPX protocol must be used.

   IPX provides services at layers 3 and 4 of the
OSI model (network and transport layers).  See SPX.



IR
(1) (Industry Remarketer)  Same as VAR or VAD.

(2) See infrared.



IRG
(InterRecord Gap)  See interrecord gap.



IRIX
See Silicon Graphics.



IRM
(Information Resource Management)  See Information
Systems and information management.



Irma
A trade name for a variety of desktop computer to
host communications products from Digital
Communications, Inc. (DCA).  Irma is not an
acronym; it is the lady's name.



Irma 3 Convertible
A 3270 emulator from DCA, Inc., Alpharetta, GA.  It
is the third generation of the Irma board, the
first 3270 emulator.  Convertible stands for its
dual bus (ISA and Micro Channel) compatibility.



Irma board
The first 3270 emulator for PCs.  Originally
spelled all caps (IRMA board) and introduced in
1982, it was the first product to provide PC to IBM
host connectivity.  See Irma 3 Convertible.



Irma software
A family of terminal emulation software products
that provide desktop to host connectivity.  Irma
Suite is a collection of the following products.

   Irma for the Mainframe provides Windows, Mac,
DOS, NT and OS/2 client connectivity to IBM
mainframes via modem, LAN and 3270 emulator.

   Irma for the AS/400 provides Windows client
connectivity to the AS/400 via modem, LAN and
twinax card.

   Irma for Open Systems provides Telnet and LAT
support on a Windows client to VAX, HP and UNIX
hosts as well as online services via LAN and modem.



Irmalan
A family of gateway programs from DCA, Inc.,
Alpharetta, GA, that allow PCs connected to
NetWare, NetBIOS and VINES networks to access an
SNA host.  Irmalan gateways support IEEE 802.2,
SDLC (via modem) and DFT environments.



iron oxide
The material used to coat the surfaces of magnetic
tapes and lower-capacity disks.



IRQ
(Interrupt ReQuest)  A hardware interrupt on a PC.
Eight lines (0-7 on 8086/88s) and 16 lines (0-15 on
286s and up) accept interrupts from devices such as
a scanner and network adapter.  Unless specifically
programmed to interact together, two devices cannot
use the same line.  If a new expansion board is
preset to the IRQ used by an existing board, one of
them must be changed.  See PC conflicts.

   Starting with the 286, the PC uses two 8259A
controller chips to handle the IRQs.  The chips are
cascaded together.  IRQ 2 connects to IRQ 9 of the
second chip.  All the IRQs except for 10, 11, 12
and 15 are preassigned.

   If a second parallel port is not used, IRQ 5 is
available.  IRQ 9 is also often available as most
VGA cards do not require an IRQ.  Thus IRQs 5, 9,
10, 11, 12 and 15 are arbitrarily used for
scanners, SCSI boards, CD-ROM controllers, sound
boards and any other peripheral that can be
attached to a PC.  They become the "IRQ
battleground."


     IRQ  Assignment
      0 - System timer
      1 - Keyboard
      2 - Connects to IRQ 9
      3 - COM2, COM4
      4 - COM1, COM3
      5 - LPT2**
      6 - Floppy disk
      7 - LPT1
      8 - Realtime clock
      9 - VGA, 3270 emulation**
     10 - **
     11 - **
     12 - **
     13 - Math coprocessor
     14 - Hard disk
     15 - **

   ** For general use.  "The battleground."





IRTF
See Internet.



IS
See Information Systems.



IS-IS
(Intermediate System to Intermediate System)  An
ISO protocol that provides dynamic routing between
routers.



ISA
(1) (Industry Standard Architecture)  Pronounced
"eye-suh."  An expansion bus commonly used in PCs.
It accepts the plug-in boards that control the
video display, disks and other peripherals.  Most
PC expansion boards on the market are ISA boards.

   ISA was originally called the AT bus, because it
was first used in the IBM AT, extending the
original bus from eight to 16 bits.  Most ISA PCs
provides a mix of 8-bit and 16-bit expansion slots.
Contrast with EISA and Micro Channel.  See local
bus.

(2) (Interactive Services Association)  A trade
group for the online industry originally founded in
1981 as the Videotex Industry Association (VIA).
Members are online services, service bureaus and
hardware and software companies, all providing
products for users with a computer and modem.
Address: 8403 Colesville Road, Silver Spring, MD
20910, 301/495-4955.



ISAM
(Indexed Sequential Access Method)  A common disk
access method that stores data sequentially, while
maintaining an index of key fields to all the
records in the file for direct access.  The
sequential order would be the one most commonly
used for batch processing and printing (account
number, name, etc.).



ISDN
(Integrated Services Digital Network)  An
international telecommunications standard for
transmitting voice, video and data over digital
lines running at 64 Kbits/sec.  ISDN service is
increasing in the U.S.

   ISDN uses circuit-switched bearer channels (B
channels) to carry voice and data and uses a
separate data channel (D channel) for control
signals via a packet-switched network.  This out-
of-band D channel allows for features such as call
forwarding, call waiting and advice of charge.

   The ISDN Basic Rate Interface, or BRI, provides
two B channels and one 16 Kbps D channel (2B+D) for
a total of 144 Kbps.

   The ISDN Primary Rate Interface, or PRI, in the
U.S. provides 23 B channels and one 64 Kbps D
channel (23B+D), equivalent to T1.  In Europe, PRI
includes 30 B channels and one D channel, which is
equivalent to European E1.

   A second-generation ISDN standard, known as
broadband ISDN or BISDN, utilizes fiber optic
cables for speeds of 155 Mbps and higher.  BISDN's
bottom three layers of implementation are called
ATM.  ATM has been decoupled from BISDN and is
gaining rapid momentum as an independent networking
technology.



ISO
(International Standards Organization)  An
organization that sets international standards,
founded in 1946 and headquartered in Geneva.  It
deals with all fields except electrical and
electronics, which is governed by the older
International Electrotechnical Commission (IEC),
also in Geneva.  With regard to information
processing, ISO and IEC created JTC1, the Joint
Technical Committee for information technology.

   It carries out its work through more than 160
technical committees and 2,300 subcommittees and
working groups and is made up of standards
organizations from more than 75 countries, some of
them serving as secretariats for these technical
bodies.  ANSI is the U.S. member body.  Address:
ANSI, 1430 Broadway, New York, NY 10018.



ISO 9660
The logical format for a CD-ROM which evolved from
the High Sierra format.  The physical format for a
CD-ROM is defined in the Yellow Book.



isochronous
Time dependent.  Realtime voice, video and
telemetry are examples of isochronous data.



isochronous Ethernet
See IsoENET.



IsoENET
(ISOchronous EtherNET)  National Semiconductor's
enhancement to Ethernet for handling realtime voice
and video.  IsoENET adds a 6Mbps synchronous
channel, made up of 96 64Kbps ISDN subchannels, to
the 10Mbps Ethernet standard.



isometric view
In computer graphics, a rendering of a 3-D object
that eliminates the distortion of shape created by
true perspective.  In isometric views, all lines on
each axis are parallel to each other, and the lines
do not converge.  Such drawings are commonly used
in technical illustrations because of their
clarity, simplicity and speed of creation.



isotropic
Refers to properties, such as transmission speed,
that are the same regardless of the direction that
is measured.  Contrast with anisotropic.



ISPF
(Interactive System Productivity Facility)  IBM
mainframe software that executes interactive user
interfaces on 3270 terminals.  It is created with
ISPF's PDF (Program Development Facility) software.



ISR
(Interrupt Service Routine)  Software routine that
is executed in response to an interrupt.



ISV
(Independent Software Vendor)  A person or company
that develops software.  It implies an organization
that specializes in software only and is not part
of a computer systems or hardware manufacturer.
Contrast with IHV.



IT
(Information Technology)  Same as Information
Systems.



ITAA
(Information Technology Association of America)
Formerly Association of Data Processing Service
Organizations (ADAPSO).  A membership organization
founded in 1960 that defines performance standards,
improves management methods and monitors government
regulations in the computer services field.
Address: 1616 N. Fort Myer Dr., Arlington, VA
22209, 703/522-5055.



item
One unit or member of a group.  See data item.



iteration
One repetition of a sequence of instructions or
events.  For example, in a program loop, one
iteration is once through the instructions in the
loop.



iterative operation
An operation that requires successive executions of
instructions or processes.



ITSEC
See NCSC.



ITU-TSS
(International Telecommunications Union-
Telecommunications Standards Section)  Formerly the
CCITT (Consultative Committee for International
Telephony and Telegraphy), it is an international
organization that sets communications standards.
TSS is one of four organs of the ITU, founded in
1865, headquartered in Geneva and comprised of over
150 member countries.




IV
See interactive video.



IVD
(Interactive VideoDisc)  See interactive video.



IVDS
(Interactive Video and Data Services)  The wireless
implementation of interactive TV.  In 1994, an
additional part of the VHF television spectrum
(218-219 MHz), which was divided into 1450
licenses, was auctioned to the highest bidders by
the U.S. government.  Organizations that own these
licenses will be able to provide interactive
television services to subscribers in their
jurisdictions.  See interactive TV.



Iverson notation
A set of symbols developed by Kenneth Iverson for
writing statements in APL.



IVR
(Interactive Voice Response)  See voice response.



iWARP
A systolic-array microprocessor from Intel that was
originally funded by DARPA and developed by
Carnegie-Mellon.



Iway
See information superhighway.



IXC
(IntereXchange Carrier)  An organization that
provides interstate communications services, such
as AT&T, MCI and Sprint.



IZE
A PC text management system from Persoft, Inc.,
Madison, WI, noted for its flexible searching.  Key
words can be entered manually or can be created
from a list or condition, such as the name between
"Dear" and a comma.



J-lead
See SOJ.



jack
A receptacle into which a plug is inserted.



jacket
A plastic housing that contains a floppy disk.  The
5.25" disk is built into a flexible jacket; the
3.25" disk uses a rigid jacket.



Jacquard loom
An automated loom that transformed the 19th century
textile industry and became the inspiration for
future calculating and tabulating machines.
Developed by the French silk-weaver, Joseph-Marie
Jacquard (1752-1834), it used punched cards to
control its operation.  Although punched cards were
used in earlier looms and music boxes, Jacquard's
loom was a vast improvement and allowed complex
patterns to be created swiftly.



JAD
(Joint Application Development)  An approach to
systems analysis and design introduced by IBM in
1977 that emphasizes teamwork between user and
technician.  Small groups meet to determine system
objectives and the business transactions to be
supported.  They are run by a neutral facilitator
who can move the group toward well-defined goals.
Results include a prototype of the proposed system.



jaggies
The stairstepped appearance of diagonal lines on a
low-resolution graphics screen.



JAM
(JYACC Application Manager)  An application
development system for client/server environments
from JYACC, Inc., New York.  It supports Windows,
Mac and Motif clients and most all UNIX servers and
VMS.  It supports over 20 databases and includes
its own database (JDB) for prototyping.  JAM/CASE
allows CASE information to be moved into JAM.
JAM/TPi integrates JAM with the Tuxedo and Encina
TP monitors.



Japanese Electronic Industry Development Assn.
See JEIDA.



Japanese PC market
It is expected that three million PCs will be sold
throughout 1994 in Japan.  NEC has over half the
market with its PC-98 series.  Apple has the next
largest share with approximately 14%.  The
remainder is divided among Fujitsu, IBM, Epson,
Toshiba and others.  A Japanese version of Windows
is available.



Javelin Plus
A PC spreadsheet from Information Resources, Inc.,
Waltham, MA.  Instead of row and column numbers, it
uses names to identify cells and consolidate data.



Jazz
An integrated Macintosh software package from
Lotus.  Modeled after Symphony, it never caught on.



JCL
(Job Control Language)  A command language for mini
and mainframe operating systems that launches
applications.  It specifies priority, program size
and running sequence, as well as the files and
databases used.



JEDEC
(Joint Electronic Device Engineering Council)  An
international body that sets integrated circuit
standards.



JEIDA
(Japanese Electronic Industry Development
Association)  A Japanese trade and standards
organization.  JEIDA joined with PCMCIA to
standardize the PC card.  In 1991, the PC card
specifications JEIDA 4.1 and PCMCIA 2.0 are the
same.



JES
(Job Entry Subsystem)  Software that provides batch
communications for IBM's MVS operating system.  It
accepts data from remote batch terminals, executes
them on a priority basis and transmits the results
back to the terminals.  The JES counterpart in VM
is called RSCS.



JetForm
Forms software for DOS, Windows and Mac from
JetForm Corporation, Waltham, MA.  JetForm provides
on-screen forms creation, routing and tracking for
workflow automation.



jewel box
A plastic container used to package an audio CD or
CD-ROM disc.



JFIF
See JPEG.



jiff
See GIF.



jitter
A flickering transmission signal or display image.



job
A unit of work running in the computer.  A job may
be a single program or a group of programs that
work together.



job class
The descriptive category of a job that is based on
the computer resources it requires when running.



job control language
See JCL.



Job Entry Subsystem
See JES.



job management language
Same as JCL.



job processing
Handling and processing jobs in the computer.



job queue
The lineup of programs ready to be executed.



job scheduling
In a large computer, establishing a job queue to
run a sequence of programs over any period of time
such as a single shift, a full day, etc.



job stream
A series of related programs that are run in a
prescribed order.  The output of one program is the
input to the next program and so on.



join
(1) In relational database management, to match one
table (file) against another based on some
condition creating a third table with data from the
matching tables.  For example, a customer table can
be joined with an order table creating a table for
all customers who purchased a particular product.

   The default type of join is known as an "inner"
join.  It produces a resulting record if there is a
matching condition.  For example, matching
shipments with receipts would produce only those
shipments that have been received.  On the other
hand, an "outer" join using that example would
create a record for every shipment whether or not
it was received.  The data for received items would
be attached to the shipments, and empty, or null,
fields would be attached to shipments without
receipts.

(2) See DOS Join.



Joint Electronic Device Engineering Council
See JEDEC.



joint requirements planning
See JRP.



Josephson junction
An ultra-fast switching technology that uses
superconductor materials, originally conceived by
Brian Josephson.  Circuits are immersed in liquid
helium to obtain near-absolute zero degrees
required for operation.  A Josephson junction has
been observed to switch in as little as 50
femtoseconds.



journal
Same as log.



journaled file system
A file system that contains its own backup and
recovery capability.  Before indexes on disk are
updated, the information about the changes is
recorded in a log.  If a power or other system
failure corrupts the indexes as they are being
rewritten, the operating system can use the log to
repair them when the system is restarted.



journaling
Keeping track of events by recording them in a
journal, or log.



JOVIAL
(Jules' Own Version of the International Algebraic
Language)  An ALGOL-like programming language
developed by Systems Development Corp. in the early
1960s and widely used in the military.  Its key
architect was Jules Schwartz.



joy stick
A pointing device used to move an object on screen
in any direction.  It employs a vertical rod
mounted on a base with one or two buttons.  Joy
sticks are used extensively in video games and in
some CAD systems.



JPEG
(Joint Photographic Experts Group)  An ISO/ITU-TSS
standard for compressing images using discrete
cosine transform.  It provides lossy compression
(you lose sharpness from the original) and can
provide ratios of 100:1 and higher.  It depends
entirely on the image, but ratios of 10:1 and 20:1
may provide little noticeable loss.  The more the
loss can be tolerated, the more the image can be
compressed.  Compression is achieved by dividing
the picture into tiny pixel blocks, which are
halved over and over until the ratio is achieved.

   JPEG is implemented in software and hardware,
with the latter providing sufficient speed for
realtime, on-the-fly compression.  C-Cube
Microsystems introduced the first JPEG chip.

   JPEG++ is an extension to JPEG from Storm
Technology, Mountain View, CA, that allows picture
areas to be selectable for different ratios.  For
example, the background could be compressed higher
than the foreground image.

   JPEG uses the JPEG File Interchange Format, or
JFIF.  File extensions are .JPG or .JFF.  MPEG is
the JPEG counterpart for full-motion digital video.



JRP
(Joint Requirements Planning)  Systems planning
performed cooperatively by a team of users and
technicians.  Functions should be prioritized and
related to the organization's goals and business
opportunities.



JTC1
(Joint Technical Committee 1)  See ISO.



jukebox
A storage device for multiple sets of CD-ROMs, tape
cartridges or disk modules.  Using carousels, robot
arms and other methods, a jukebox physically moves
the storage medium from its assigned location to an
optical or magnetic station for reading and
writing.  Access between modules usually takes
several seconds.



Julian date
The representation of month and day by a
consecutive number starting with Jan. 1.  For
example, Feb. 1 is Julian 32.   Dates are converted
into Julian dates for calculation.



jump
Same as goto.



jumper
The simplest form of an on/off switch.  It is just
a tiny, plastic-covered metal block, which is
pushed onto two pins to close that circuit.  It is
used to select myriads of functions on a printed
circuit board or on a peripheral device.  For
example, on a PC, jumpers are used to select I/O
addresses and IRQs.  On an IDE drive, a jumper
selects between master and slave.  A jumper can be
used in place of a more costly DIP switch.



junction
The point at which two elements make contact.  In a
transistor, a junction is the point where an N-type
material makes contact with a P-type material.



justification
In typography, the alignment of text evenly between
left and right margins.  Contrast with ragged
right.



justify
(1) To shift the contents of a field or register to
the right or left.

(2) To align text evenly between left and right
margins.



K
See kilo.



K-byte
See kilobyte.



K&R C
(Kernighan and Ritchie C)  A version of C defined
by Brian Kernighan and Dennis Ritchie that preceded
the ANSI standard.



K5
The code name for a Pentium-class CPU chip from
Advanced Micro Devices, Inc., (AMD).  It is
expected to be available in volume by mid 1995.



Kaleida
(Kaleida Labs, Inc., Mountain View, CA)  A joint
venture of IBM and Apple that is developing
multimedia software.  See ScriptX.



KB, Kb
See kilobyte and kilobit.



Kbit
See kilobit.



Kbits/sec
(KiloBITS per SECond)  Thousand bits per second.



KBps, Kbps
(KiloBytes Per Second, KiloBits Per Second)
Thousand bytes per second.  Thousand bits per
second.



Kbs
(KiloBits per Second)  Same as Kbps.



Kbyte
See kilobyte.



Kbytes/sec
(KiloBYTES per SECond)  Thousand bytes per second.



Kerberos
A security system developed at MIT that
authenticates users.  It does not provide
authorization to services or databases; it
establishes identity at logon, which is used
throughout the session.



Kermit
An asynchronous file transfer protocol developed at
Columbia University, noted for its accuracy over
noisy lines.  Several extensions exist, including
SuperKermit, a full-duplex, sliding window version.
Kermit is popular on minis and mainframes and can
also handle byte-oriented transfers over 7-bit
ASCII systems.



kernel
The fundamental part of a program, typically an
operating system, that resides in memory at all
times and provides the basic services.  It is the
part of the operating system that is closest to the
machine and may activate the hardware directly or
interface to another software layer that drives the
hardware.  See microkernel.



kerning
In typography, the spacing of letter combinations,
such as WA, MW and TA, where each character
overlaps into some of the space of the other for
improved appearance.



Kerr effect
A change in rotation of light reflected off a
magnetic field.  The polarity of a magneto-optic
bit causes the laser to shift one degree clockwise
or counterclockwise.



key
(1) A keyboard button.

(2) Data that identifies a record.  Account number,
product code and customer name are typical key
fields used to identify a record in a file or
database.  As an identifier, each key value must be
unique in each record.  See sort key.

(3) A numeric code used by an algorithm to create a
code for encrypting data for security purposes.



key cap
A replaceable, top part of a keyboard key.  To
identify commonly-used codes, it can be replaced
with a custom-printed key cap.



key click
An audible feedback provided when a key is pressed.
It may be adjustable by the user.



key command
A key combination (Alt-G, Ctrl-B, Command-M, etc.)
used as a command to the computer.



key driven
Any device that is activated by pressing keys.



key entry
Data entry using a keyboard.



key field
See key (2).



key in
To enter data by typing on a keyboard.



key rollover
See n-key rollover.



key system
See key telephone system.



key telephone system
An inhouse telephone system that is not centrally
connected to a PBX.  Each telephone has buttons for
outside lines that can be dialed directly without
having to "dial 9."



key-to-disk machine
A stand-alone data entry machine that stores data
on magnetic disk for computer entry.



key-to-tape machine
A stand-alone data entry machine that stores data
on magnetic tape for computer entry.  Introduced by
Mohawk Data Sciences in the mid 1960s, it was the
first advancement in data entry since the card
keypunch.  Mohawk's stock went from $2 to $200 in a
couple of years.



key word
(1) A word used in a text search.

(2) A word in a text document that is used in an
index to best describe the contents of the
document.

(3) A reserved word in a programming or command
language.



keyboard
A set of input keys.  On terminals and personal
computers, it includes the standard typewriter
keys, several specialized keys and features
outlined below.  See PC keyboard, AT keyboard and
Enhanced keyboard.


                Enter (Return) Key
In text applications, it ends a paragraph or short
line.  In data applications, it signals the end of
the input for that field or line.


                    Cursor Keys
The four arrow keys move the cursor on screen.
They are used in conjunction with shift, alt and
control to move the cursor in bigger jumps; for
example, CONTROL UP ARROW might scroll the screen.
Some earlier keyboards didn't have cursor keys, in
which case, control or alt was used with some
letter key.


       Control, Alt, Command and Option Keys
Used like a shift key, these keys are held down
while another key is pressed to command the
computer in a variety of ways.


                    Escape Key
Commonly used to exit or cancel the current mode
such as exiting from a menu.  Also used to clear an
area or repeat a function such as redrawing the
screen.


                   Numeric Lock
Locks a combination number/cursor keypad into
numeric mode only.


                 Home and End Keys
Commonly used to move the cursor to the extreme
left or right side of the current line.  Often used
in conjunction with shift, control and alt; for
example, CONTROL HOME and CONTROL END usually move
the cursor to the beginning and end of file.


            Page Up and Page Down Keys
Used to move the cursor up and down a page, screen
or frame.  Often used in combination with shift,
control and alt.


                   Function Keys
Used to call up a menu or perform a function, they
are located in a cluster on the left side or in a
row across the top of the keyboard (labelled F1,
F2, etc.).  Often used with the shift, control and
alt keys providing 40 separate functions with F1
through F10.


                   Backspace Key
Used to delete the character to the left of the
cursor (erase typos) and may be used with the
shift, control and alt keys to erase segments of
text.  The extra-wide, typewriter-style key is
preferred.


                    Delete Key
Used to erase the character at the current cursor
location.  Used in conjunction with the shift,
control and alt keys, it is used to erase any
segment of text, such as a word, sentence or
paragraph.


                    Insert Key
Usually a toggle switch to go back and forth
between insert and overwrite mode.  Also used to
"paste" a segment of text or graphics into the
document at the current cursor location.


                  Repeating Keys
Most computer keys repeat when held down, a
phenomenon first-time computer users must get used
to.  If you hold a key down that is used to command
the computer, you'll be entering the command
several times.


                 Audible Feedback
Keyboards may cause a click or beep to be heard
from the computer when keys are pressed.  This is
done to acknowledge that the character has been
entered.  It should be adjustable for personal
preference.


            All Keyboards Are Not Equal
Keyboard quality is critical for experienced
typists.  The feel (tension and springiness) varies
greatly.  Key placement is important.  Older
keyboards and new laptop keyboards may have awkward
return and shift key placements.





keyboard buffer
A memory bank or reserved memory area that stores
keystrokes until the program can accept them.  It
lets fast typists continue typing while the program
catches up.



keyboard controller
A circuit that monitors keystrokes and generates
the required data bits when pressed.



keyboard enhancer
Same as macro processor.



keyboard interrupt
A signal that gets the attention of the CPU each
time a key is pressed.  See interrupt.



keyboard macro processor
See macro processor.



keyboard processor
See keyboard controller and keyboard enhancer.



keyboard template
A plastic card that fits over the function keys to
identify each key's purpose in a particular
software program.



keyframe
In computer graphics animation, a frame that
indicates the beginning or end of an object in
motion.



keyframe animation
Animating a graphics object by creating smooth
transitions between various keyframes.



keypad
A small keyboard or supplementary keyboard keys;
for example, the keys on a calculator or the
number/cursor cluster on a computer keyboard.



keypunch
To punch holes in a punched card.  Although punched
cards are obsolete, some people still say "keys are
punched" on a keyboard.



keypunch department
Same as data entry department.



keypunch machine
A punched-card data entry machine.  A deck of blank
cards is placed into a hopper, and, upon operator
command, the machine feeds one card to a punch
station.  As characters are typed, a series of dies
at the punch station punch the appropriate holes in
the selected card column.



Khornerstones
A benchmark program that tests CPU, I/O and
floating point performance.



KHz
(KiloHertZ)  One thousand cycles per second.  See
horizontal scan frequency.



kicks
See CICS.



kilo
Thousand.  Abbreviated "K."  It often refers to the
precise value 1,024 since computer specifications
are usually binary numbers.  For example, 64K means
65,536 bytes when referring to memory or storage
(64x1024), but a 64K salary means $64,000.  The
IEEE uses "K" for 1,024, and "k" for 1,000.  See
binary values and space/time.



kilobit
One thousand bits.  Also Kb, Kbit and K-bit.  See
kilo and space/time.



kilobyte
One thousand bytes.  Also KB, Kbyte and K-byte.
See kilo and space/time.



Kinetics FastPath
A gateway from the Kinetics division of Excelan,
Inc., that connects LocalTalk and PhoneNet systems
and LaserWriters to VAXs, UNIX-based computers, PCs
and other Ethernet-based hosts.  It supports
AppleTalk, TCP/IP and DECnet protocols.



kiosk
A small, self-standing structure such as a newstand
or ticket booth.  Unattended multimedia kiosks
dispense public information via computer screens.
Either a keyboard, touch screen or both are used
for input.



Kittyhawk
A hard disk used in laptops and portable
applications from HP.  It was the world's first
1.3" hard disk, introduced in 1992.



kludge
Also spelled "kluge" and pronounced "klooj."  A
crude, inelegant system, component or program.  It
may refer to a makeshift, temporary solution to a
problem as well as to any product that is poorly
designed or that becomes unwieldy over time.



knowledge acquisition
The process of acquiring knowledge from a human
expert for an expert system, which must be
carefully organized into IF-THEN rules or some
other form of knowledge representation.



knowledge base
A database of rules about a subject used in AI
applications.  See expert system.



knowledge based system
An AI application that uses a database of knowledge
about a subject.  See expert system.



knowledge domain
A specific area of expertise of an expert system.



knowledge engineer
A person who translates the knowledge of an expert
into the knowledge base of an expert system.



knowledge representation
A method used to code knowledge in an expert
system, typically a series of IF-THEN rules (IF
this condition occurs, THEN take this action).



KnowledgeMan
An application development system for DOS, OS/2,
VMS and UNIX environments from Micro Data Base
Systems, Inc., Lafayette, IN.  It includes an
RDBMS, object-based 4GL programming and integrated
functions, allowing, for example, database queries
to update spreadsheets or results to be embedded in
text documents.



Korn shell
See UNIX.



KSDS
(Keyed Sequence DataSet)  A VSAM structure that
uses an index to store records in available free
space.  Retrieval is by key field or by address.
Contrast with ESDS.



KSR terminal
(Keyboard Send Receive terminal)  Same as
teleprinter.  Contrast with RO terminal.



L1 cache
See cache.



L2 cache
See cache.



L3_PDU
(Level 3_Protocol Data Unit)  See SIP.



label
(1) In data management, a made-up name that is
assigned to a file, field or other data structure.

(2) In spreadsheets, descriptive text that is
entered into a cell.

(3) In programming, a made-up name used to identify
a variable or a subroutine.

(4) In computer operations, a self-sticking form
attached to the outside of a disk or tape in order
to identify it.

(5) In magnetic tape files, a record used for
identification at the beginning or end of the file.



label prefix
In a spreadsheet, a character typed at the
beginning of a cell entry.  For example, in 1-2-3,
a single quote (') identifies what follows as a
descriptive label even if it's a number.



ladder DAC
(ladder Digital to Analog Converter)  Circuitry
used to convert digital sound back into analog form
for amplification.  An individual resistor is
associated with each bit of the digital sample,
typically 16 bits.  The resistors are weighted to
the mathematical value of the bit they represent.
The 16-bit sample is read, passed to all 16
resistors at the same time, and the sum total of
the current passing through the resistors
represents the analog value of the digital sample.

   Ladder DACs represent a parallel conversion of
the sample.  See 1-bit DAC.



LAN
(Local Area Network)  A communications network that
serves users within a confined geographical area.
It is made up of servers, workstations, a network
operating system and a communications link.

   Servers are high-speed machines that hold
programs and data shared by all network users.  The
workstations, or clients, are the users' personal
computers, which perform stand-alone processing and
access the network servers as required (look up the
term client/server for more information on this
concept).

   Diskless and floppy-only workstations are
sometimes used, which retrieve all software and
data from the server.  A printer can be attached to
a workstation or to a server and be shared by
network users.

   Small LANs can allow each workstation to
function as a server, allowing all users access to
data on all machines.  These peer-to-peer networks
are often simpler to install and manage, but
dedicated servers provide better performance and
can handle higher transaction volume.  Multiple
servers are used in large networks.

   The controlling software in a LAN is the network
operating system, such as NetWare, UNIX and
Appletalk, which resides in the server.  A
component part of the software resides in each
client and allows the application to read and write
data from the server as if it were on the local
machine.

   The message transfer is managed by a transport
protocol such as IPX, SPX and TCP/IP.  The physical
transmission of data is performed by the access
method (Ethernet, Token Ring, etc.) which is
implemented in the network adapters that plug into
the machines.  The actual communications path is
the cable (twisted pair, coax, optical fiber) that
interconnects each network adapter.  See MAN, WAN,
bridge, router, gateway and hub.



LAN adapter
Same as network adapter.



LAN administrator
See network administrator.



LAN analyzer
See network analyzer.



LAN Emulation
The ability to support communications protocols,
such as IP, IPX, AppleTalk and DECnet, on an ATM
network as well as to connect Ethernet, Token Ring
and FDDI LANs to ATM networks.  The processing is
done in a LAN Emulation driver in the client
station and in LAN Emulation servers that reside in
an ATM network.



LAN Manager
(1) A network operating system from Microsoft that
runs as a server application under OS/2 and
supports both DOS, Windows and OS/2 clients.  It
uses the Microsoft File Sharing protocol (SMB) for
file sharing, the NetBEUI protocol for its
transport mechanism and uses Named Pipes for
interprocess communication (IPC).  See LAN Server.

   LAN Manager for Windows NT is a different
product.  It adds network management and services
to Windows NT, which includes peer-to-peer
networking.

(2) Same as network administrator.



LAN Network Manager
IBM Token Ring network management software.  LAN
Station Manager is the workstation counterpart that
collects data for LAN Network Manager.



LAN Requester
LAN Server software that resides in the
workstation.



LAN segment
A section of a local area network that is used by a
particular workgroup or department and separated
from the rest of the LAN by a bridge, router or
switch.  Networks are divided into multiple
segments for security and to improve traffic flow
by filtering out packets that are not destined for
the segment.



LAN Server
(1) A network operating system from IBM that runs
as a server application under OS/2 and supports
both DOS, Windows and OS/2 clients.  Originally
based on LAN Manager when OS/2 was jointly
developed by IBM and Microsoft, Version 3.0 runs
under IBM's own OS/2 Version 2.0.

   Version 3.0 provides disk mirroring, CID
capability and Network Transport Services/2 (NTS/2)
for concurrent access to NetWare servers.  Options
are Lan Server for the Macintosh for Mac client
access and System Performance/2 (SP/2), a series of
network management utilities.

(2) (LAN server)  Generically, a file server in a
network.



LAN station
(1) A workstation in a local area network.

(2) See LAN Network Manager.



LAN Workplace
A family of software products from Novell that
allows DOS, Windows, Macintosh and OS/2 clients in
a NetWare environment to access resources on a
TCP/IP network.  LAN Workplace for DOS can also
encapsulate NetWare protocols and run NetWare-
dependent applications entirely within a TCP/IP
network.



LANDA
(LAN Dealers Association)  An association that
merged with NOMDA to become the Business Technology
Association.  See BTA.



landing zone
A safe non-data area on a hard disk used for
parking the read/write head.



Landmark rating
A widely-used PC performance test from Landmark
Research International, Clearwater, FL, that
measures CPU, video and coprocessor speed.  CPU
speed is rated as the clock speed required in an
AT-class machine that would provide equivalent
performance.



landscape
A printing orientation that prints data across the
wider side of the form.  Contrast with portrait.



landscape monitor
A monitor that is used to display facing text
pages.  It is wider than it is high.



language
A set of symbols and rules used to convey
information.  See machine language, programming
language, graphics language, page description
language, fourth-generation language, standards &
compatibility and user interface.



language processor
Language translation software.  Programming
languages, command languages, query languages,
natural languages and foreign languages are all
translated by software.



LanguageAccess
An SAA-compliant query language from IBM that
translates a user's English-language request into
SQL language for QMF.  QMF retrieves the data.



LANtastic
A popular peer-to-peer LAN operating system for
DOS, Windows and OS/2 from Artisoft, Inc., Tucson,
AZ.  It supports Ethernet, ARCNET and Token Ring
adapaters as well as its own twisted-pair adapater
at two Mbits/sec.  Artisoft also makes Ethernet
adapters.  Included are e-mail and chat functions.
Voice mail and conversation are optional.

   Simply LANtastic is an entry-level version
designed for easy installation and use.  It is
available as software only or with network adapters
that eliminate common cabling problems for first-
time users.

   Multiple protocols are supported starting with
LANtastic 6.0, allowing a LANtastic client station
to access a NetWare, LAN Manager, LAN Server or
Windows NT server.  See CorStream.



LAP
(Link Access Procedure)  An ITU-TSS family of error
correction protocols originally derived from the
HDLC standard and used on X.25 packet networks.


    LAP-B (LAP-Balanced)     Used in current X-25
                             networks.

    LAP-D (LAP-D channel)    Used in the data
                             channel of an ISDN
                             transmission.

    LAP-M (LAP-Modem)        Defined in ITU-TSS
                             V.42, which uses some
                             of the LAPD methods
                             and adds additional
                             ones.

    LAP-X (LAP-Half-dupleX)  Used for ship to shore
                             transmission.





LapLink
A PC file transfer program from Traveling Software,
Inc., Bothell, WA, that transfers data between
laptops and desktop computers.  LapLink Mac
transfers files between PCs and Macs.



laptop computer
A portable computer that has a flat screen and
usually weighs less than a dozen pounds.  It uses
AC power and/or batteries.  Most have connectors
for an external monitor and keyboard transforming
them into desktop computers.  See notebook computer
and pocket computer.


                 LAPTOP FEATURES

   Keyboard
   Keyboard layout is often sacrificed.  The Home,
   End, PageUp and PageDn keys may not be dedicated
   keys, requiring that you hold down the Fn key in
   conjunction with them.  This is more cumbersome.

      Function keys and cursor keys are often made
   smaller.  If you have large hands, test the
   keyboard carefully.


   Screen Quality
   Monochrome LCD screens translate colors into
   shades of gray.  The more shades, the better the
   representation of full-color images.  Passive
   matrix LCD screens provide a subdued color.
   Active matrix LCD screens are sharp and rich,
   but are costly and use more power.  Double scan
   passive matrix is better than passive matrix,
   but not as sharp as active matrix.  Stay tuned
   for active addressing screens (see LCD).


   Screen Resolution & Acceleration
   Without a docking station or expansion slot
   capability, you cannot improve the built-in
   display resolution.  If you want higher
   resolution when you hook it up to your desktop
   monitor, it may not be there.  In addition,
   Windows needs fast graphics.  If a graphics
   accelerator is not built into your display, you
   will experience poor Windows performance.


   External Display & Keyboard Connectors
   Connect a full-size CRT and keyboard for
   home/office.  Even if you like your laptop
   keyboard, you may want to use an external
   keyboard with your external monitor, because the
   laptop screen usually doesn't lie back flat to
   get out of the way from straight-on viewing
   of the external monitor.

      A full-size keyboard can be connected through
   the external keyboard connector on most laptops.
   Keyboards can be attached to earlier laptops
   with an adapter via the serial or parallel port.


   Low Power CPU
   Newer CPUs use less voltage and have built-in
   power management that lets them idle or
   essentially "go to sleep" when not used.
   Intel's SL chips and AMD's SXL chips are
   examples.


   Built-in Trackball
   Very convenient, but placement is not standard.
   Try it first.  Keyboard keys or a specially-
   designed key may also be used as a mouse
   substitute.  Barring any of these, a built-in
   mouse port or serial port lets you use an
   external mouse or trackball.


   Built-in Modem
   Saves lugging an external modem.


   Expansion
   Expansion is critical on a laptop.  Early
   laptops have no expansion at all.  Some laptops
   connect to an optional docking station that
   provides one or more expansion slots for
   expandability, but that's only when it is used
   as a desktop machine.  Some laptops allow for
   interchangeable hard disks and screens.

   The PCMCIA slot is becoming the major expansion
   vehicle on a laptop.  Laptops with one or two
   PCMCIA slots can be expanded with a modem,
   network adapter, more memory, a solid state
   disk, a removable hard disk and other devices as
   they are developed.


   Auto Resume
   Lets you return to the computer and pick up
   where you left off without having to reload your
   applications.


   Dual Display
   Using an external monitor and laptop display at
   the same time.  For presentations with a data
   projector, it may be difficult to look at a
   projected image off in the distance.


   Nickel Hydride Battery
   Provides about 20% more power per pound than
   nickel cadmium and doesn't have its associated
   memory problem.  Recharge life may be shorter,
   however.


   Weight
   Seven pounds doesn't sound like much until you
   lug it around all day.  Some subnotebooks use an
   external floppy disk to reduce poundage.

      Also, check the transformer weight.  They
   never mention this in the ads, but it can add
   one or two pounds.  On long trips, you will
   probably keep the transformer in the case.

      Following is a rough guide to current-day
   weights (without the transformer):


                        Weight
           Type        (Pounds)

          Laptop         4-18
          Notebook       4-7
          Subnotebook    2-4
          Pocket          1





laser
(Light Amplification from the Stimulated Emission
of Radiation)  A device that creates a very uniform
light that can be precisely focused.  It generates
a single wavelength or narrow band of wavelengths
and is used in applications such as communications,
printing and disk storage.  Unlike the transmission
of electricity, transmission of light pulses over
optical fibers is not affected by nearby electrical
interferences.  See LED.


                The Laser Discovery
In 1957, the laser was conceived by Gordon Gould, a
graduate student in physics at Columbia University.
When Gould filed for patents in 1959, he found that
Columbia professor Charles Townes and Arthur
Schawlow of Bell Labs had already filed for them.
The year before, AT&T had, in fact, demonstrated a
working laser at Bell Labs.  In 1977, after years
of litigation, a court awarded Gould rights to the
first of three patents and later to all of them.
He finally reaped millions in royalties.



laser disc
See LD and videodisc.



laser printer
A printer that uses the electrophotographic method
used in copy machines to print a page at a time.  A
laser "paints" the dots of light onto a
photographic drum or belt.  The toner is applied to
the drum or belt and then transferred onto the
paper.  Desktop printers use cut sheets like a copy
machine.  Large printers may use rolls of paper.

   In 1975, IBM introduced the first laser printer,
the high-speed model 3800.  Later, Siemens
introduced the ND 2 and Xerox introduced the 9700.
These self-contained printing presses are online to
a mainframe or offline, accepting print image data
on tape reels or disk packs.  Large-scale machines
provide collating and stacking, and some models can
print on very wide paper.

   In 1984, HP introduced the LaserJet, the first
desktop laser printer, which propelled desktop
publishing.  The desktop laser printer has made the
daisy wheel printer obsolete, and it competes
directly with the dot matrix printer.

   Although high-resolution color laser printers
are also available, less expensive desktop versions
will become widely used throughout the 1990s.

   Note: All large-scale printers that print a page
at a time do not use a laser.  Some use ion
deposition, which creates the image with
electricity rather than light.



LaserDisc
Also called a videodisc, it is an optical disk used
for full-motion video that uses the LaserVision
technology developed by Philips.  LaserDisc players
can read the CLV format for two hours of recording
as well as the CAV direct access format for a total
of one hour.

   Movie LaserDiscs typically use the CLV (constant
linear velocity) format, which records the signal
on a continuous, spiraling track.  Each side
contains 108,000 frames equalling one hour of
video, or two hours per disc.  In this format, the
signal density is uniform, and the player increases
or decreases the speed of rotation depending on
which part of the disc is being played.

   LaserDiscs used for interactive purposes
(training, video games, etc.) and some movies use
the CAV (constant angular velocity) format like
that of a magnetic disk, in which the tracks are
concentric circles, each one containing one frame
of video.  This format is used when fast direct
access to a frame is required.  Each side holds
54,000 frames equalling 30 minutes of video, or one
hour per disc.

   Early LaserDiscs recorded sound in analog
format.  Today, most LaserDiscs contain both an
analog and a digital soundtrack, and modern players
default to the digital sound if available.  Some
players let the user select the soundtrack,
allowing multiple languages and other annotations
to be included on the same disc.

   Various videodisc systems were introduced during
the 1970s, but only the LaserVision technology
survived.  Whereas VCRs are widespread, as of 1995,
LaserDiscs have still gained only modest acceptance
in the marketplace.  It is expected that LaserDiscs
will become more widely used as home theater
systems become more popular, since the LaserDisc's
superior resolution is more noticeable on larger
screens.



LaserJet
A family of desktop laser printers from HP.
Introduced in 1984 at $3,495, the first LaserJet
revolutionized the desktop laser printer market.
LaserJets print at 300 dpi and starting with the
LaserJet 4, at 600 dpi.  Third-party enhancements,
such as the WinJet, increase resolution to 1200
dpi.  PCL is the printer command language.

   LaserJets accept bitmapped fonts from plug-in
cartridges and, except for the original model, from
the computer (soft fonts).  Built-in Intellifont
scalable fonts were included starting with the
LaserJet III (PCL Version 5).  The III also
overcame previous limitations by being able to
print portrait and landscape fonts on the same page
and white text on a black background.

   PostScript capability became available starting
with the Series II in the form of plug-in
cartridges from HP and others.  Native PostScript
models were introduced with the LaserJet 4.

   In 1994, HP launched the HP Color LaserJet,
capable of printing 16.7 million colors (24 bit) at
300 dpi with a list price of $7295 plus $799 for
optional PostScript.  It prints color in a single
pass at 2 ppm or 10 ppm for black only.  It
supports an enhanced PCL 5 language as well as
PostScript Level 2.


              LASERJET SPECIFICATIONS

     Input paper capacity  Built in fonts    Canon
            Year Speed       Cartridges  Printer
  Model     Intro (ppm)           RAM   Engine
 
 x LaserJet   1984 8 100  2 1 128K-2M  CX
 x PLUS       1985 8 100  2 1 512K-2M  CX
 x 500 PLUS   1986 8 500  2 1 512K-2M  CX
 x 2000 (1)   198720 500 34 3 1-5M  LPB20
 x Series II  1987 8 200  6 2 512K-4M  SX
 x IID *dss   1989 8 400 22 2 640K-4M  SX
 x IIP        1989 4  50 14 1 512K-4.5 LX
 x IIP+       1991slightly faster than IIP LX
 x III        1990 8 200 22f2 1-5M     SX
 x IIID *dss  1990 8 400 22f2 1-5M     SX
 x IIIP       1991 4  50 22f1 1-5M     LX
 x IIIsi *ds  1991171000 30f2 1-17M    NX
   4L         1993 4 10026sf0 1-2M    
   4ML        1993 4 10080sf0   4M    
 600 dpi
 x 4          1992 8 35045sf1 2-32M    EX
   4+  *ds    199412 35045sf1 2-66M    EX
 x 4M         1992 8 35080sf1 6-26M    EX
   4M+ *ds    199412 35080sf1 6-38M    EX
   4si *ds    199317100045sf2 2-34M   LPB-NX
   4siMX *ds  199317100080sf210-26M   LPB-NX
   4V  *11x17 199417 35045sf- 4-68M   LPB-NX
   4MV *11x17 199417 35080sf-12-44M   LPB-NX
 Color 300 dpi
  Color LJ  1994 2  250 45sf- 8-72M   
        mono    10                    


     x = No longer made as of Oct. 1994
     *ds = double sided printing optional
     *dss = double sided printing standard
     *11x17 = handles 11x17" paper with full bleed
     26sf = 26 Intellifont scalable fonts
     45sf = 45 scalable fonts: 35 Intellifont
                                10 TrueType
     80sf = 80 scalable fonts: 35 Intellifont
                                10 TrueType
                                35 Type 1
     22f = 14 bitmapped fonts, 8 Intellifont
     30f = 14 bitmapped fonts, 16 Intellifont







LaserMaster
(LaserMaster Corporation, Eden Prarie, MN)  A
manufacturer of high-resolution PostScript printers
and add-in boards.  See WinJet.



LaserWriter
A family of 300 dpi desktop laser printers from
Apple introduced in 1985.  All models handle
bitmapped fonts, and, except for the SC models,
include PostScript, built-in AppleTalk connections,
as well as RS-232 ports for connecting PCs via
Diablo emulation.



LAT
(Local Area Transport)  A communications protocol
from Digital for controlling terminal traffic in a
DECnet environment.



LATA
(Local Access and Transport Area)  The geographic
region set up to differentiate local and long
distance telephone calls.  Any telephone call
between parties within a LATA is handled by the
local telephone company.



latch
An electronic circuit that maintains one of two
states.  See flip-flop.



late binding
Linking routines at runtime.



latency
The time between initiating a request for data and
the beginning of the actual data transfer.  On a
disk, latency is the time it takes for the selected
sector to come around and be positioned under the
read/write head.  Channel latency is the time it
takes for a computer channel to become unoccupied
in order to transfer data.  Network latency is the
delay introduced when a packet is momentarily
stored and then forwarded.



latent image
An invisible image typically of electrical charges.
For example, in a copy machine, a latent image of
the page to be copied is created on a plate or drum
as an electrical charge.



launch
To cause a program to load and run.



LAWN
(Local Area Wireless Network)  A
transmitter/receiver from O'Neill Communications,
Inc., Princeton, NJ, that connects devices using
radio transmission.



layer
(1) In computer graphics, one of several on-screen
"drawing boards" for creating elements within a
picture.  Layers can be manipulated independently,
and the sum of all layers make up the total image.

(2) In communications, a protocol that interacts
with other protocols to provide all the necessary
transmission services.  See OSI.



layout setting
A value used to format a printed page.  Margins,
tabs, indents, headers, footers and column widths
are examples.



lazer
See laser.



lazy write
Refers to the effect caused by using a write back
cache.  Data is written to the cache first and,
later, during idle machine cycles or at some
specified time, is written to disk if it is a disk
cache or to memory if it is a CPU cache.



LBRV
(Low Bit Rate Voice)  A voice sampling technique
that analyzes each 15-30 millisecond speech segment
independently and converts it into a 30-byte frame.



LC
(Low cost Color)  See Macintosh.



LCC
See leaded chip carrier.



LCD
(Liquid Crystal Display)  A display technology that
uses rod-shaped molecules (liquid crystals) that
flow like liquid and bend light.  Unenergized, the
crystals direct light through two polarizing
filters, allowing a natural background color to
show.  When energized, they redirect the light to
be absorbed in one of the polarizers, causing the
dark appearance of crossed polarizers to show.  The
more the molecules are twisted, the better the
contrast and viewing angle.

   Because it takes less power to move molecules
than to energize a light-emitting device, LCDs
replaced LEDs in digital watches years ago.  The
LCD was developed at RCA's Sarnoff Research Center
in Princeton, NJ in 1963.


                   TYPES OF LCDs

           Passive Display (TN and STN)
Called "passive matrix" when used for computer
screens.  Called "passive display" when used for
digital readouts, icons, etc.  All active
electronics (transistors) are outside of the
display screen.  Passive display provides a sharp
image for monochrome screens, but is more subdued
for color.  Submarining is common.  Passive display
types are:

  TN (twisted nematic) - low-cost displays for
     consumer products, instruments, etc.
     90 twist; black on gray/silver background

  STN (supertwisted nematic) - used extensively on
     laptops for mono and color displays.
       180 twist; green/blue on yellow background
       270 twist; blue on white/blue background

  Dual Scan - Improves STN display by dividing the
     screen into two halves and scanning each half
     simultaneously and doubling the number of
     lines refreshed.  Not as sharp as active
     matrix.

  Active Addressing - Improves STN display by
     addressing pixels differently.  Eliminates
     submarining and less expensive than active
     displays, but not as sharp.  Expected late
     1994, early 1995.


               Active Display (TFT)
Typically used for laptop color screens, thus
called "active matrix" displays.  Transistors are
built into each pixel within the screen.  For
example, 640x480 color VGA screen requires 921,600
transistors; one for each red, green and blue dot.
Provides a sharp, clear image with good contrast
and eliminates submarining, but fabrication costs
are high.  Uses a 90 (TN) twist.  Also called TFT
LCD (thin film transistor LCD).


               Reflective vs Backlit
Reflective screens used in many consumer appliances
and some lightweight laptops require external light
and only work well in a bright room or with a desk
lamp.  Backlit and sidelit screens have their own
light source and work well in dim lighting.





LCD panel
Also called a projection panel, it is a data
projector that accepts computer output and displays
it on a see-through liquid crystal screen that is
placed on top of an overhead projector.  Some
laptops are built with an LCD screen that you can
remove from the computer, take the back off and use
as a projection panel.



LCD printer
An electrophotographic printer that uses a single
light source directed by liquid crystal shutters.



LD
(Laser Disc)  A videodisc that contains full-motion
video in analog form with audio in both analog and
digital.  It comes in 8" and 12" diameters in CAV
and CLV formats.  Playing time for a two-sided 12"
LD is up to two hours for CLV and one hour for CAV.
The 8" LD provides 40 and 28 minutes respectively.
See videodisc.



LE
(Less than or Equal to)  See relational operator.



lead acid
A rechargeable battery technology widely used in
portable gardening tools, but has been used in some
portable computers.  It uses lead plates and an
acid electrolyte.  It provides the least amount of
charge per pound of the rechargeable technologies.
See nickel cadmium, nickel hydride and zinc air.



leaded chip carrier
A square chip housing with pin connectors on all
four sides (provides more I/O paths than a DIP).
Contrast with leadless chip carrier.



leader
(1) A length of unrecorded tape used to thread the
tape onto the tape drive.

(2) A dot or dash used to draw the eye across the
printed page, such as in a table of contents.



leading
In typography, the vertical spacing between lines
of type (between baselines).  The name comes from
the early days of typesetting when the space was
achieved with thin bars of lead.



leading edge
(1) The edge of a punched card or document that
enters the reading station first.

(2) In digital electronics, a pulse as it changes
from a 0 to a 1.

(3) In programming, a loop that tests a condition
before the loop is entered.

(4) (Leading Edge Products, Inc., Westborough, MA)
A PC manufacturer founded in 1980.  Its Model M
(for Mitsubishi) in 1982 was the first PC-
compatible from overseas.  Korean Daewoo
Corporation supplied it with products since 1984
and acquired it in 1989.



leading zeros
Zeros used to fill a field that do not increase the
numerical value of the data.  For example, all the
zeros in 0000006588 are leading zeros.



leadless chip carrier
A square chip housing with flat contact connectors
on all four sides (provides more I/O paths than a
DIP).  Contrast with leaded chip carrier.



leaf
In database management, the last node of a tree.



League for Programming Freedom
An organization of professors, students and
businessmen who believe that software copyrights
and patents jeopardize the industry.  They are
dedicated to "bringing back the freedom to write
programs."  Address: 1 Kendall Square, P.O. Box
9171, Cambridge, MA 02139.



leapfrog test
A storage diagnostic routine that replicates itself
throughout the storage medium.



leased line
A private communications channel leased from a
common carrier.  It can be ordered in pairs,
providing a four-wire channel for full-duplex
transmission (dial-up system provides only two-wire
lines).  To improve line quality, it can also be
conditioned.



leased line modem
A high-speed modem used in private lines.  It may
have built-in lower speeds for alternate use in
dial-up lines.



least significant digit
The rightmost digit in a number.



LEC
(Local Exchange Carrier)  An organization that
provides local telephone services (RBOCs, GTE,
etc.).



LED
(Light Emitting Diode)  A display technology that
uses a semiconductor diode that emits light when
charged.  It usually gives off a red glow, although
other colors can be generated.  It is used in
readouts and on/off lights in myriads of electronic
appliances.  It was the first digital watch
display, but was superseded by LCD, which uses less
power.



LED printer
An electrophotographic printer that uses a matrix
of LEDs as its light source rather than a laser.



left justify
Same as flush left.



legacy card
In a PC, an expansion card that does not have the
ISA Plug and Play capability built into it.  Up
until late 1994, all cards were legacy cards.



legacy LAN
A LAN topology, such as Ethernet or Token Ring,
that has a large installed base or has been in
existence for a long time.



legacy system
A mainframe or minicomputer information system that
has been in existence for a long time.



Lempel Ziv
A data compression algorithm that uses an adaptive
compression technique.  See LZW.



LEN
(Low Entry Networking)  In SNA, peer-to-peer
connectivity between adjacent Type 2.1 nodes, such
as PCs, workstations and minicomputers.  LU 6.2
sessions are supported across LEN connections.



LEO
(Low-Earth Orbit)  A type of communications
satellite that orbits no higher than 500 miles
above the earth.  It differs from the
geosynchronous, or GEO, satellite, which is 22,282
miles high.  The GEO appears stationary, because it
rotates at earth speed.  The LEO rotates around the
globe in a couple of hours, but its shorter
distance supports low-power, hand-held
transmitters.



Lessons
Following are lists of definitions based on
subject.  Use them as a springboard to other terms.
Either print the list and check off your progress
on paper or set a bookmark here and return to the
bookmark.



Lessons Associations
(Set a bookmark to return here.)

  ACM     (Information processing)
  BCS     (Personal computers)
  BTA     (Business technology)
  CBEMA   (Equipment vendors)
  CompTIA (Resellers, distributors)

  CPA     (Computer press)
  DPMA    (DP management)
  EMA     (Electronic Mail)
  ICCP    (Industry certification)
  IMA     (Interactive multimedia)

  ITAA    (Information technology)
  MMA     (Microcomputer managers)
  MPC     (Multimedia)
  MUG     (Mac users)
  NASI    (Systems integrators)

  National Cristina Foundation
           (Channel for donating old equipment)
  NCGA     (Computer graphics)
  PowerOpen Association 
           (PowerOpen certification)
  SPA      (Software publishers)
  UniForum (UNIX and open systems)
  WUGNET   (Windows users)


 STANDARDS BODIES
  ANSI    (U.S. standards)
  NIST    (U.S. standards)
  CCIA    (Computer/communications industry)
  ITU-TSS (International standards)
  IEC     (International standards)

  ISO     (International standards)
  EIA     (Interface standards; RS-232)
  IEEE    (Electronics standards)
  JEDEC   (IC standards)
  JEIDA   (Japanese electronics)

  PCMCIA  (PC memory card standards)
  X.400 API Association  (X.400 standards)



Lessons Basics
(Set a bookmark to return here.)

  hot topics
  hardware
  software
  data
  computer

  computer system
  program
  analog
  digital
  bit

  binary
  byte
  peripheral
  magnetic recording
  floppy disk

  hard disk
  printer
  monitor
  modem
  operating sytem

  bus
  space/time
  chip
  PC
  Macintosh

  Apple-IBM alliance
  personal computer
  office automation
  x86
  68000

  PowerPC
  how to select a personal computer
  industry topics
  enterprise networking
  standards & compatibility (lots of detail)



Lessons Communications
(Set a bookmark to return here.)

  communications
  LAN
  enterprise networking
  OSI
  OSI model

  data link protocol
  client/server
  baseband
  Ethernet
  Token Ring Network

  ARCNET
  FDDI
  ATM
  NetWare
  Lantastic

  Appletalk
  SNA
  TCP/IP
  X Window
  routable protocol

 LAN CONNECTIVITY
   repeater
   bridge
   router
   brouter
   gateway
   hub

 MODEMS
   BBS
   online services
   modem
   emoticon
   RS-232

   V.22bis    2200 bps standard
   V.32       9600 bps standard
   V.32bis   14400 bps standard
   V.34      28800 bps standard
   V.42      error checking
   V.42bis   compression
   MNP       error checking/compression



Lessons Desktop publishing
(Set a bookmark to return here.)

  desktop publishing
  font
  typeface
  scalable font
  outline font
  vector font

  halftone
  bitmap
  kerning
  leading
  color separation

  colors
  point
  prepress
  imagesetter
  phototypesetter

  page description language
  PCL
  PostScript
  ransom note typography



Lessons Graphics
(Set a bookmark to return here.)

  graphics
  paint program
  drawing program
  CAD
  CAD/CAM

  bit depth
  wireframe modeling
  solid modeling
  surface modeling
  ray tracing
  artifact

  Renderman interface
  JPEG
  AutoCAD
  FastCAD
  Bezier

  spline
  GKS
  PHIGS
  bitblt
  PCX

  GIF
  TIFF
  PIC
  HSV
  graphics formats



Lessons History
(Set a bookmark to return here.)

  Pascaline
  Hollerith machine
  ABC
  ENIAC
  UNIVAC I

  punched card
  1401
  650
  IBM mainframes
  IBM minicomputers

  personal computer
  PDP
  VAX
  Altair 8800
  TRS

  PET
  System/360
  Trilogy
  Apple-IBM alliance



Lessons Internet
(Set a bookmark to return here.)

  Internet
  Internet address
  Internet references
  USENET
  TCP/IP

  PDIAL
  Telnet
  FTP
  Archie
  Gopher

  Veronica
  Worldwide Web
  Mosaic
  Cello
  WAIS

  Finger
  WHOIS
  PING
  newsgroup
  newsreader

  Internaut
  InterNIC
  information superhighway
  Mbone
  FAQ file

  IP address



Lessons Job categories
(Set a bookmark to return here.)

  user
  systems analyst
  business analyst
  programmer
  programmer analyst

  data administrator
  database administrator
  network administrator
  system administrator
  operator



Lessons Mainframes
(Set a bookmark to return here.)

  mainframe
  channel
  front end processor
  communications controller
  TP monitor

  DASD
  IBM mainframes
  VAX
  dumb terminal
  intelligent terminal

  screen scraper
  ES/9000
  System/360
  System/370
  ESA/370

  ESA/390
  3270
  Irma board
  ESCON
  Sysplex

  SNA
  MVS
  VM
  VSE
  CICS

  IMS
  TSO
  SQL
  DB2
  Micro Focus


Lessons Multimedia
(Set a bookmark to return here.)

  multimedia
  MPC
  CD
  CD-ROM
  sound card

  MIDI
  MIDI voices
  CD-I
  DVI
  Video CD

  artifact
  hypertext
  Private Eye
  virtual reality
  ScriptX

  Video for Windows
  QuickTime



Lessons Networking
See Lessons Communications.



Lessons Personal computers
(Set a bookmark to return here.)


 CATEGORIES
   personal computer
   how to select a personal computer
   hot topics
   Apple-IBM alliance
   PC

   Macintosh
   Amiga
   MEGA 
   laptop
   palmtop


 HARDWARE
   computer
   memory
   floppy disk
   hard disk
   magnetic disk

   keyboard
   modem
   optical disk
   laser printer
   serial port

   parallel port
   game port
   mouse
   tape backup
   PC conflicts

   x86
   68000
   PowerPC


 BUSES
   bus
   ISA
   EISA
   Micro Channel
   NuBus

   local bus
   VL-bus
   PCI


 ENVIRONMENTS
   operating system
   DOS
   Windows
   Windows NT
   OS/2

   DESQview
   DESQview/X
   UNIX
   DMI
   PowerOpen


 SOFTWARE
   word processing
   DBMS
   spreadsheet
   business graphics
   communications program

   integrated software package
   paint program
   drawing program


 TUTORIALS
   DOS abc's
   Win abc's
   Pkunzip abc's



Lessons Programming
(Set a bookmark to return here.)

  programming
  assembly language
  high-level language
  machine language
  microcode

  reentrant code
  function
  object-oriented programming
  COBOL
  BASIC

  FORTRAN
  Pascal
  C
  C++
  LISP

  Prolog
  LOGO
  MUMPS
  REXX


 PC PROGRAMMING
   ASCII chart
   hex chart
   binary values
   PC display modes
   PC memory map

   PC color codes
   paragraph
   Turbo C
   Microsoft C
   Borland C++



Lessons Slang & interesting stuff
(Set a bookmark to return here.)

  flame
  frob
  droupie
  trashware
  shelfware

  kludge
  RTFM
  hookemware
  dribbleware
  phone hawk

  computercruiter
  Big Blue
  hacker
  dweeb
  foo

  TLA
  write only code
  buffer flush
  Stringy Floppy
  sneakernet

  boss screen
  ransom note typography
  Easter Egg
  plug and hope
  emoticons

  TTFN
  vaporware
  Systemantics
  hot topics



Lessons System design
(Set a bookmark to return here.)


 OVERVIEW
   information system
   system development cycle
   enterprise networking
   Systemantics


 PEOPLE
   systems analyst
   application programmer
   programmer analyst
   systems programmer
   database administrator

   network administrator
   system administrator
   operator


 DEVELOPMENT
   data administration
   prototyping
   functional specification
   documentation
   CASE
   standards & compatibility


 SOFTWARE
   query language
   report writer
   spreadsheet
   DBMS
   financial planning system

   DSS
   EIS
   EPSS
   expert system
   case-based reasoning



Lessons UNIX
(Set a bookmark to return here.)

  UNIX
  open systems
  TCP/IP
  NFS
  NIS

  SMTP
  SNMP
  Motif
  Open Look
  Tuxedo

  Encina
  Sequent
  Pyramid
  Encore
  HP 9000

  RS/6000
  OSF
  X/Open
  POSIX
  USL

  X Window
  X terminal
  BSD UNIX
  STREAMS
  emacs

  vi
  awk
  sed 
  grep
  UniForum


 UNIX/PC INTEGRATION
   DESQview/X
   SCO Open Desktop
   Solaris 2.0
   Lan Workplace
   UnixWare
   NetWare NFS



Lessons Vendors
(Set a bookmark to return here.)

  vendors
  hardware vendors
  software vendors
  IBM
  Apple

  Atari
  Commodore
  HP
  Digital Equipment
  Data General

  Bull HN
  Intel
  Motorola
  TI
  Tandy

  Tandem
  Microsoft
  Borland
  Digital Research
  Computer Associates

  D&B Software
  industry topics





letter quality
The print quality of an electric typewriter.  Laser
printers, ink jet printers and daisy wheel printers
provide letter quality printing.  24-pin dot matrix
printers provide near letter quality (NLQ), but the
characters are not as dark and crisp.



level 1 cache
See cache.



level 2 cache
See cache.



lexicographic sort
Arranging items in alphabetic order like a
dictionary.  Numbers are located by their
alphabetic spelling.



LF
See line feed.



LHARC
A popular freeware compression program developed by
Haruyasu Yoshizaki that uses a variant of the LZW
(LZ77) dictionary method followed by a Huffman
coding stage.  It runs on PCs, UNIX and other
platforms as its source code is also free.



li-ion
See lithium ion.



librarian
(1) A person who works in the data library.

(2) See CA-Librarian.



library
(1) A collection of programs or data files.

(2) A collection of functions (subroutines) that
are linked into the main program when it is
compiled.

(3) See data library.



library function
A subroutine that is part of a function library.
Same as library routine.



library management
See version control.



library routine
A subroutine that is part of a macro or function
library.



LIFO
(Last In First Out)  A queueing method in which the
next item to be retrieved is the item most recently
placed in the queue.  Contrast with FIFO.



ligature
Two or more typeface characters that are designed
as a single unit (physically touch).  Fi, ffi, ae
and oe are common ligatures.



light bar
Same as highlight bar.



light emitting diode
See LED.



light guide
A transmission channel that contains a number of
optical fibers packaged together.



light pen
A light-sensitive stylus wired to a video terminal
used to draw pictures or select menu options.  The
user brings the pen to the desired point on screen
and presses the pen button to make contact.

   Screen pixels are constantly being refreshed.
When the user presses the button, allowing the pen
to sense light, the pixel being illuminated at that
instant identifies the screen location.



light source
In computer graphics, the implied location of a
light source in order to simulate the visual effect
of a light on a 3-D object.  Some programs can
compute multiple light sources.



lightwave
Light in the infrared, visible and ultraviolet
ranges, which falls between x-rays and microwaves.
Wavelengths are between 10 nanometers and one
millimeter.



lightwave system
A device that transmits light pulses over optical
fibers at extremely high speeds (Gbits/sec range).
Many intercity telephone trunks have been converted
to lightwave systems.



lightweight protocol
A communications protocol designed with less
complexity in order to reduce overhead.  For
example, it uses fixed-length headers because they
are faster to parse than variable-length headers.
To ensure compatibility, it eliminates optional
subsets of the standard so that both sides are
always equipped to deal with each other.



LIM EMS
See EMS.



limited distance modem
Same as short-haul modem.



limulator
See EMS emulator.



Linda
A set of parallel processing functions added to
languages, such as C and C++, that allows data to
be created and transferred between processes.  It
was developed by Yale professor David Gelernter,
when he was a 23-year old graduate student.



line
(1) In text-based systems, a row of characters.

(2) In graphics-based systems, a row of pixels.

(3) Any communications channel.



line adapter
In communications, a device similar to a modem,
that converts a digital signal into a form suitable
for transmission over a communications line and
vice versa.  It provides parallel/serial and
serial/parallel conversion, modulation and
demodulation.



line analyzer
A device that monitors the transmission of a
communications line.



line concentration
See concentrator.



line conditioning
See conditioning.



line dot matrix printer
A line printer that uses the dot matrix method.
See printer.



line drawing
A graphic image outlined by solid lines.  The mass
of the drawing is imagined by the viewer.  See wire
frame.



line driver
In communications, a device that is used to extend
the transmission distance between terminals and
computers that are connected via private lines.  It
is used for digital transmission and is required at
each end of the line.



line editor
An outmoded editing program that allows text to be
created and changed one line at a time.  The Edlin
editor included with DOS is an example.



line feed
(1) A character code that advances the screen
cursor or printer to the next line.  The line feed
is used as an end of line code in UNIX.  In DOS and
OS/2 text files, the return/line feed pair (ASCII
13 10) is the standard end of line code.

(2) A printer button that advances paper one line
when depressed.



line frequency
The number of times each second that a wave or some
repeatable set of signals is transmitted over a
line.  See horizontal scan frequency.



line level
In communications, the signal strength within a
transmission channel, measured in decibels or
nepers.



line load
(1) In communications, the percentage of time a
communications channel is used.

(2) In electronics, the amount of current that is
carried in a circuit.



line number
(1) A specific line of programming language source
code.

(2) On display screens, a specific row of text or
row of dots.

(3) In communications, a specific communications
channel.



line of code
A statement in a source program.  In assembly
language, it usually generates one machine
instruction, but in a high-level language, it may
generate a series of instructions.

   Lines of code are used to measure the complexity
of a program.  However, comparisons are misleading
if the programs are not in the same language or
category.  For example, 20 lines of code in COBOL
might require 200 lines of code in assembly
language.



line of sight
An unobstructed view from transmitter to receiver.



line printer
A printer that prints one line at a time.  Line
printers are usually connected to mainframes and
minicomputers.  See printer.



line segment
In vector graphics, same as vector.



line speed
See data rate.



line squeeze
In a mail merge, the elimination of blank lines
when printing names and addresses that contain no
data in certain fields, such as title, company and
second address line.  See field squeeze.

   Without line squeeze     With line squeeze

   Pat Smith                 Pat Smith
                             10 South Main
   10 South Main             Bearcat, OR 80901
   Bearcat, OR 80901





linear
Sequential or having a graph that is a straight
line.



linear address space
See flat address space.



linear editing
See linear video editing.



linear programming
A mathematical technique used to obtain an optimum
solution in resource allocation problems, such as
production planning.



linear video
Continuous playback of videotape or videodisc.  It
typically refers to analog video technology.



linear video editing
Editing analog videotape.  Before digital editing
(nonlinear video editing), video sequences were
edited by inserting new frames and reconstructing
the balance of the tape by adding the remainder of
the frames.  Contrast with nonlinear video editing.



link
(1) In communications, a line, channel or circuit
over which data is transmitted.

(2) In data management, a pointer embedded within a
record that refers to data or the location of data
in another record.

(3) In programming, a call to another program or
subroutine.



link edit
To use a linkage editor to prepare a program for
running.



Link Support Layer
See LSL.



linkage editor
A utility program that links a compiled or
assembled program to a particular environment.  It
formally unites references between program modules
and libraries of subroutines.  Its output is a load
module, a program ready to run in the computer.



linked list
In data management, a group of items, each of which
points to the next item.  It allows for the
organization of a sequential set of data in
noncontiguous storage locations.



linker
See linkage editor.



Linpack
A package of FORTRAN programs for numerical linear
algebra that is commonly used to create benchmark
programs for testing a computer's floating point
performance.



Linux
A freeware version of a clone of the UNIX System V
Release 3.0 kernel that runs on x86 machines.  It
is available on programming BBSs and on the
Internet.



LIPS
(Logical Inferences Per Second)  The unit of
measurement of the thinking speed of an AI
application.  Humans do about 2 LIPS.  In the
computer, one LIPS equals from 100 to 1,000
instructions.



liquid crystal display
See LCD.



liquid crystal shutters
A method of directing light onto the drum in an
electrophotographic printer.  A matrix of liquid
crystal dots function as shutters that are opened
and closed.  See LCD.



Lisa
The first personal computer to include integrated
software and use a graphical interface.  Modeled
after the Xerox Star and introduced in 1983 by
Apple, it was ahead of its time, but never caught
on due to its $10,000 price and slow speed.



LISP
(LISt Processing)  A high-level programming
language used in non-numeric programming.
Developed in 1960 by John McCarthy, its syntax and
structure is very different than traditional
programming languages.  For example, there is no
syntactic difference between data and instructions.

   LISP, available in both interpreter and compiler
versions, is used extensively in AI applications as
well as in compiler creation.  The language can be
modified and expanded by the programmer.  Many
varieties of LISP have been developed, including
versions that perform calculations efficiently.
The following Common LISP example converts
Fahrenheit to Celsius:

   (defun convert ()
     (format t "Enter Fahrenheit ")
     (let ((fahr (read)))
      (format t "Celsius is <126>D"
        (truncate (*(-fahr 32)
            (/ 5 9))))))





list
(1) An arranged set of data, often in row and
column format.

(2) In fourth-generation languages, a command that
displays/prints selected records.  For example, in
dBASE, list name address displays all names and
addresses in the current file.



list box
An on-screen display of text items in a scrollable
window.  For example, the DOS and Windows versions
of this database use a list box for the index of
terms.



list processing
Processing non-numeric data.



list processing language
A programming language, such as LISP, Prolog and
Logo, used to process lists of data (names, words,
objects).  Although operations such as selecting
the next to first, or next to last element, or
reversing all elements in a list, can be programmed
in any language, list processing languages provide
commands to do them.  Recursion is also provided,
allowing a subroutine to call itself over again in
order to repetitively analyze a group of elements.



listing
Any printed output.



literal
In programming, any part of an instruction that
remains unchanged when translated into machine
language, such as an output message.



lithium ion
A rechargeable battery technology that provides
more than twice the charge per pound as nickel
hydride.  Although used in camcorders and other
devices, Toshiba introduced the first lithium ion
notebook in the U.S. with its Portg 3400 series
in late 1993.

   Lithium polymer technology may provide twice as
much power as lithium ion.



little endian
See big endian.



liveware
People.



LLC
(Logical Link Control)  See "LANs" under data link
protocol.



LLCC
See leadless chip carrier.



lo-res
See low resolution.



load
(1) To copy a program from some source, such as a
disk or tape, into memory for execution.

(2) To fill up a disk with data or programs.

(3) To insert a disk or tape into a drive.

(4) In programming, to store data in a register.

(5) In performance measurement, the current use of
a system as a percentage of total capacity.

(6) In electronics, the flow of current through a
circuit.



load high
To load programs into high memory.  See DOS
Loadhigh.



load module
A program in machine language form ready to run in
the computer.  It is the output of a link editor.



load sharing
Sharing the workload in two or more computers.



loaded line
A telephone line from customer to central office
that uses loading coils to reduce distortion.



loader
A program routine that copies a program into memory
for execution.



loader routine
Same as loader.



loading coil
A device used in local telephone loops (exceeding
18,000 ft.) that boosts voice-grade transmission.
It often adds noise to high-speed data transmission
and must be removed for such traffic.



local area network
See LAN.



local bus
A bus between the CPU, memory and peripheral
devices that runs at the speed of the CPU.  In a
PC, the VL-bus and PCI bus provide faster data
transfer than the traditional ISA bus.

   Starting with the 386, when CPU speeds began to
greatly accelerate, PCs have been built with two
buses.  The CPU accesses its memory chips via a 32-
bit (64 bits with the Pentium) internal path, known
as the local bus, at the full clock speed of the
CPU (25MHz, 33MHz, etc.).  However, it has
traditionally accessed its peripheral devices more
slowly; over a 16-bit ISA bus at at only 8MHz.
Even the inherently-faster 32-bit EISA runs slow in
order to accomodate ISA boards, which plug into it.

   VESA's VL-bus and Intel's PCI local bus
standards were created to tap directly into the
higher CPU speeds.  PCI runs at 33MHz and VL-bus
runs up to 40MHz.  Faster speeds are also expected.
ISA and EISA motherboards are now built with extra
slots for VL-bus or PCI cards or both.


          Bus Architecture in a PC
       Ŀ     Ŀ
                 Ĵ   Main   
          CPU    LOCAL  Memory  
                 ÿ   ڴ          
       ٳ B 
       Ŀ U Ŀ
          VESA    S  PCI bus  
       Controllerÿ   ڴController
       ٳ   
              Ŀ     
               ISA bus       
         VL   Controller  PCI
         bus    bus
                  ISA         
                  bus         
                             
                             
      The peripheral controller cards
      plug into slots on the ISA, PCI and
      VLbus buses (disk controller, display
      adapter (VGA), serial port, parallel port,
      SCSI controller, scanner card, CD-ROM card,
      sound card, etc.).



               Bus Speed Comparisons

      Bus type  Width   Speed   Total rate

       ISA     2 bytes     8MHz    16MB
       EISA    4 bytes     8MHz    32MB
       VL-bus  4 bytes    25MHz   100MB
       VL-bus  4 bytes    33MHz   132MB
       PCI     4 bytes    33MHz   132MB
       PCI     8 bytes    33MHz   264MB





local bypass
An interconnection between two facilities without
the use of the local telephone company.



local console
A terminal or workstation directly connected to the
computer or other device that it is monitoring and
controlling.



local exchange carrier
See LEC.



local loop
A communications line between a customer and the
telephone company's central office.  See loop
carrier.



local memory
The memory used by a single CPU or allocated to a
single program or function.



local storage
The disk storage used by a single CPU.



local variable
In programming, a variable used only within the
routine or function it is defined in.



LocalTalk
A LAN access method from Apple that uses twisted
pair wires and transmits at 230,400 bps.  It runs
under AppleTalk and uses a daisy chain topology
that can connect up to 32 devices within a distance
of 1,000 feet.  Third party products allow it to
hook up with bus, passive star and active star
topologies.

   Apple's LocalTalk PC Card lets a PC gain access
to an AppleTalk network.



lock manager
Software that provides file and record locking for
multiple computer systems or processors that share
a single database.



lockup
Refers to a computer's inability to respond to user
input.  See abend.



log
A record of computer activity used for statistical
purposes as well as backup and recovery.



logic
The sequence of operations performed by hardware or
software.  Hardware logic is made up of circuits
that perform an operations.  Software logic
(program logic) is the sequence of instructions in
a program.  See algorithm.

   Note: Logic is not the same as logical.  See
logical vs physical and logical expression.



logic analyzer
(1) A device that monitors computer performance by
timing various segments of the running programs.
The total running time and the time spent in
selected progam modules is displayed in order to
isolate the the least efficient code.

(2) A device used to test and diagnose an
electronic system, which includes an oscilloscope
for displaying various digital states.



logic array
Same as gate array or PLA.



logic bomb
A program routine that destroys data; for example,
it may reformat the hard disk or insert random bits
into data files.  It may be brought into a personal
computer by downloading a corrupt public-domain
program.  Once executed, it does its damage right
away, whereas a virus keeps on destroying.



logic chip
A processor or controller chip.  Contrast with
memory chip.



logic circuit
A circuit that performs some processing or
controlling function.  Contrast with memory.



logic controller
See PLC.



logic diagram
A flow chart of hardware circuits or program logic.



logic error
A program bug due to an incorrect sequence of
instructions.



logic gate
A collection of transistors and electronic
components that make up a Boolean logical
operation, such as AND, NAND, OR and NOR.
Transistors make up logic gates.  Logic gates make
up circuits.  Circuits make up electronic systems.



logic operation
An operation that analyzes one or more inputs and
generates a particular output based on a set of
rules.  See AND, OR and NOT and Boolean logic.



logic-seeking printer
A printer that analyzes line content and skips over
blank spaces at high speeds.



logical
(1) A reasonable solution to a problem.

(2) A higher level view of an object; for example,
the user's view versus the computer's view.  See
logical vs physical.



logical data group
Data derived from several sources.  Same as view.



logical drive
An allocated part of a physical drive that is
designated and managed as an independent unit.  For
example, drives C:, D: and E: could represent three
physical drives or one physical drive partitioned
into three logical drives.



logical expression
An expression that results in true or false.  Same
as Boolean expression.



logical field
A data field that contains a yes/no, true/false
condition.



Logical Link Control
See LLC.



logical lock
The prevention of user access to data that is
provided by marking the file or record through the
use of software.  Contrast with physical lock.



logical operator
One of the Boolean logical operators (AND, OR and
NOT).



logical record
A reference to a data record that is independent of
its physical location.  It may be physically stored
in two or more locations.



Logical Unit
See LU and LU 6.2.



logical unit number
See LUN.



logical vs physical
High-level versus low-level.  Logical implies a
higher view than the physical.  Users relate to
data logically by data element name; however, the
actual fields of data are physically located in
sectors on a disk.  For example, if you want to
know which customers ordered how many of a
particular product, your logical view is customer
name and quantity.  Its physical organization might
have customer name in a customer file and quantity
in an order file cross referenced by customer
number.  The physical sequence of the customer file
could be indexed, while the sequence of the order
file could be sequential.

   A message transmitted from Phoenix to Boston
logically goes between two cities; however, the
physical circuit could be Phoenix to Chicago to
Philadelphia to Boston.

   When you command your program to change the
output from the video screen to the printer, that's
a logical request.  The program will perform the
physical change of address from, say, device number
02 to device number 04.



login
Same as logon.



Logo
A high-level programming language noted for its
ease of use and graphics capabilities.  It is a
recursive language that contains many list
processing functions that are in LISP, although
Logo's syntax is more understandable for novices.

   Logo's graphics language is called turtle
graphics, which allows complex graphics images to
be created with a minimum of coding.  The turtle is
a triangular-shaped cursor, which is moved on
screen with commands that activate the turtle as if
you were driving it, for example, go forward 100
units, turn right 45 degrees, turn left 20 degrees.

   Stemming from a National Science Foundation
project, Logo was created by Seymour Papert in the
mid 1960s along with colleagues at MIT and members
of Bolt Beranek & Newman.  Originally developed on
large computers, it has been adapted to most
personal computers.

   The following Object Logo example converts
Fahrenheit to Celsius:

   convert
   local [fahr]
   print "|Enter Fahrenheit |
   make "fahr ReadWord
   print "|Celsius is |
   print (:fahr - 32) * 5 / 9
   end





logoff
To quit, or sign off, a computer system.



logon
To gain access, or sign in, to a computer system.
If restricted, it requires users to identify
themselves by entering an ID number and/or
password.  Service bureaus base their charges for
the time between logon and logoff.



logout
Same as logoff.



long
In programming, an integer variable.  In C, a long
is four bytes and can be signed (-2G to +2G) or
unsigned (4G).  Contrast with short.



long card
In PCs, a full-length controller board that plugs
into an expansion slot.  Contrast with short card.



long-haul
In communications, modems or communications devices
that are capable of transmitting over long
distances.



long lines
In communications, circuits that are capable of
handling transmissions over long distances.



longitudinal redundancy check
See LRC.



LONWORKS
A control network from Echelon Corporation, Palo
Alto, CA, that uses Echelon's NEURON CHIP (made by
Motorola and Toshiba) and LONTALK protocol.  Each
NEURON CHIP uses a 48-bit number for
identification.  Control modules that contain the
NEURON CHIP and transceivers for transmitting via
RS-485, twisted pair, coax and AC power lines are
available on credit card-sized boards.

   The LONBUILDER development system is used to
create applications, which are written into PROM
chips.  LONWORKS software, as well as programming
interfaces for DOS and Windows, provide node
installation and network management.



look and feel
Generally refers to the user interface of a
program, especially with regard to its similarity
to other programs.  This issue has been and will
continue to be hotly contested in the courts,
because some programs look and function like
others, and the original developer sometimes gets
upset about it.

   Oddly enough, programming languages have never
been copyrighted or patented, which allows a
developer to write a compiler that translates an
language identical to one already in use.  However,
when a vendor sells a software package that looks
and feels like another, it is subject to
litigation, and look and feel cases have been won
in the U.S. courts.



lookup
A data search performed within a predefined table
of values (array, matrix, etc.) or within a data
file.



loop
In programming, a repetition within a program.
Whenever a process must be repeated, a loop is set
up to handle it.  A program has a main loop and a
series of minor loops, which are nested within the
main loop.  Learning how to set up loops is what
programming technique is all about.

   The following example prints an invoice.  The
main loop reads the order record and prints the
invoice until there are no more orders to read.
After printing date and name and addresses, the
program prints a variable number of line items.
The code that prints the line items is contained in
a loop and repeated as many times as required.

   mainĿ
   loop           Get next order
                      
                  Print date
                  Print bill to
                  Print ship to
          lineĴ
          item       
          loop   Print line item
                     
              Ĵ
                      
                  Print totals
       

   Loops are accomplished by various programming
structures that have a beginning, body and end.
The beginning generally tests the condition that
keeps the loop going.  The body comprises the
repeating statements, and the end is a GOTO that
points back to the beginning.  In assembly
language, the programmer writes the GOTO, as in the
following example that counts to 10.

          MOVE     "0" TO COUNTER
   LOOP   ADD      "1" TO COUNTER
          COMPARE  COUNTER TO "10"
          GOTO     LOOP IF UNEQUAL
          STOP

   In high-level languages, the GOTO is generated
by the interpreter or compiler; for example, the
same routine as above using a WHILE loop.

       COUNTER = 0
       DO WHILE COUNTER <> 10
          COUNTER = COUNTER + 1
       ENDDO
       STOP


   For a more detailed look at a loop, look at the
end of the C definition.  The main event loop of
the DOS version of this database is presented.





loop carrier
In telephone communications, a system that
concentrates a number of analog or digital lines
from a remote termination station into the central
office.  It normally converts analog voice into
digital at the remote station; however, it can be
adapted to provide ISDN service to a customer.



loopback plug
A diagnostic connector that directs the sending
line back into the receiving line for test
purposes.



loosely coupled
Refers to stand-alone computers connected via a
network.  Loosely coupled computers process on
their own and exchange data on demand.  Contrast
with tightly coupled.



lossless compression
Compression techniques that decompress data 100%
back to original.  Contrast with lossy compression.



lossy compression
Compression techniques that do not decompress data
100% back to original.  Images and audio samples
may be able to afford small losses of resolution in
order to increase compression.  Contrast with
lossless compression.



lost cluster
Disk records that have lost their identification
with a file name.  This can happen if a file is not
closed properly, which can sometimes occur if the
computer is turned off without formally quitting an
application.  See DOS Chkdsk.



Lotus
(Lotus Development Corporation, Cambridge, MA)  A
major software company founded in 1981 by Mitch
Kapor.  It achieved outstanding success by
introducing the first spreadsheet for the IBM PC
(see Lotus 1-2-3).  Over the years, it has
developed a variety of applications and has helped
set industry standards.  In 1990, it acquired Samna
Corporation, developers of the popular, Windows-
based Ami word processors.



Lotus 1-2-3
The most widely-used spreadsheet application with
over 20 million copies installed worldwide.  It
runs on DOS, Windows, Macintosh, Sun, VAX, OS/2,
UNIX and IBM mainframe platforms.  Major
development effort centers on Windows, OS/2 and
DOS.  Starting with Version 3.0, it provides 3-D
and dynamic linking capabilities.

   The first 1-2-3 (DOS) shipped in January 1983
under a well-organized marketing campaign.  It was
the first innovative spreadsheet for the IBM PC.
The 1-2-3 stood for the integration of spreadsheet,
database and graphics.  Its ability to function
like a simple database was unique, and turning data
into a chart with a single keystroke was dazzling
for its time.  The program's user interface was
also easier to use than other programs (see Lotus
menu).



Lotus menu
The menu introduced with Lotus 1-2-3 that became a
de facto standard.  It is a row of words, each of
which is an option that can be selected by
highlighting it and pressing Enter or by pressing
the first letter of the word.  When the word is
highlighted, an explanation line is displayed above
or below it.  Contrast with pull-down menu.



Lotus Notes
A document database system from Lotus that runs in
a client/server environment under Windows, OS/2 and
various UNIX platforms.  Notes is designed for
workgroups.  It provides a way to create a document
that coworkers append their own comments to as a
project moves from stage to stage.  Files can also
be attached to a Notes document.  In addition,
Notes provides e-mail and outbound fax.

   Notes keeps documents in sync.  When a change is
made to a document, those changes are replicated
throughout the organization where necessary.  As of
Release 3, it allows a Windows PC to act as a Notes
server and will run with any VIM-compliant e-mail
system such as cc:Mail.

   In 1994, programming interfaces were introduced
to add multimedia capability.  Phone Notes lets
users access Notes functionality via telephone and
listen to Notes databases via text-to-speech
facilities.  It allows voice annotations to be
embedded into Notes databases as well.  Video Notes
lets video be embedded.



low density
Refers to an earlier version of a storage device
with less bits per inch than today's version.  See
DD and double density.



low-earth orbit
See LEO.



low entry networking
See LEN.



low frequency
An electromagnetic wave that vibrates in the range
from 30 to 300,000 Hertz.



low-level format
The sector identification on a disk that the drive
uses to locate sectors for reading and writing.
See format program.



low-level language
A programming language that is very close to
machine language.  All assembly languages are low-
level languages.  Contrast with high-level
language.



low-orbit satellite
See LEO.



low radiation
Refers to video terminals that emit less VLF (Very
Low Frequency) and ELF (Extremely Low Frequency)
radiation.  This level of radiation cannot be
shielded by office partitions.  It must be
cancelled out from the CRT.  Health studies on this
are not conclusive and are very controversial.  See
MPR II.



low resolution
A low-grade display or printing quality due to a
lower number of dots or lines per inch.



lower CASE
See back-end CASE.



lpi
(Lines Per Inch)  The number of lines printed in a
vertical inch.



lpm
(Lines Per Minute)  The number of lines a printer
can print or a scanner can scan in a minute.



LPT1
In a PC, the logical name assigned to parallel port
#1.  The parallel port is typically used for the
printer.  A second parallel port, if installed, is
assigned to LPT2.  Contrast with COM1.



LQ
See letter quality.



LRC
(Longitudinal Redundancy Check)  An error checking
method that generates a parity bit from a specified
string of bits on a longitudinal track.  In a row
and column format, such as on magnetic tape, LRC is
often used with VRC, which creates a parity bit for
each character.



LSAPI
(Licensing Service API)  A programming interface
from Microsoft that allows a licensing server to
track applications in use for managing multiuser
software licenses.



LSI
(Large Scale Integration)  Between 3,000 and
100,000 transistors on a chip.  See SSI, MSI, VLSI
and ULSI.



LSI-11
A family of board-level computers from Digital that
uses the micro version of the PDP-11.  Introduced
in 1974, it was the first to use the Q-bus.



LSL
(Link Support Layer)  A common interface for
network drivers.  It provides a common language
between the transport layer and the data link layer
and allows different transport protocols to run
over one network adapter or one transport protocol
to run on different network adapters.

   Instead of directly calling a particular data
link protocol, the transport protocol calls the LSL
library.  Thus, any LSL-compliant network driver
can provide data link services in that protocol
stack.  LSL is part of UNIX System V.  It is also
the basis of Novell and Apple's ODI specification.
See ODI and STREAMS.


     OSI
    LAYER  Transport Transport
      3    Protocol  Protocol 
        Ŀ
        Multiple Protocol Interface
        Ĵ
            LINK SUPPORT LAYER     
        Ĵ
          Multiple Link Interface  
        
     OSI   Data       Data    
    LAYER  Link       Link    
      2    Driver     Driver  





LT
(Less Than)  See relational operator.



LU
(Logical Unit)  In SNA, one end of a communications
session.  The complete LU to LU session is defined
by session type.  Common types are:

     1  Host to 3770 RJE terminal
     2  Host to 3270 mainframe terminal
     3  Host to 3270 printer
   6.2  Program-to-program
     7  Host to 5250 midrange terminal





LU 6.2
An SNA protocol that establishes a session between
two programs.  It allows peer-to-peer
communications as well as interaction between
programs running in the host with PCs, Macs and
midrange computers.

   Before LU 6.2, processing was done only in the
mainframe.  LU 6.2 allows processing to take place
at both ends of the communications, necessary for
today's distributed computing and client/server
environment.  See APPC and CPI-C.



lumen
A unit of measurement of the flow (rate of
emission) of light.  A wax candle generates 13
lumens; a 100 watt bulb generates 1,200.  See
candela.



Lumena
A PC paint program from Time Arts, Inc., Santa
Rosa, CA, that provides sophisticated, special
effects.  It accepts and generates NTSC video
output and requires a video graphics board.



luminance
The amount of brightness, measured in lumens, that
is given off by a pixel or area on a screen.  It is
the black/gray/white information in a video signal.



LUN
(Logical Unit Number)  The physical number of a
device in a daisy change of drives.  See SCSI.



LZW
(Lempel-Ziv-Welch)  A widely-used dictionary
compression method that stems from two techniques
introduced by Jacob Ziv and Abraham Lempel.  LZ77
scans a fixed length block of data and creates
pointers back to data when it repeats.  LZ78 scans
the data and creates a dictionary of repeating
phrases.  Pointers are created to those phrases.



M
See mega.



M-byte
See megabyte.



M-O
See magneto-optic.



M-R
See magneto-resistance.



M Technology Association
See MUMPS.



M1
The code name for a Pentium-class CPU chip from
Cyrix Corporation.  It is expected to be available
in volume by mid 1995.



Mac
(1) See Macintosh.

(2) (MAC) (Mandatory Access Control)  A security
control that requires clearance levels.  See NCSC.

(3) See MAC layer.



MAC layer
(Media Access Control layer)  The protocol sublayer
that controls access to the physical transmission
medium on a LAN.  The MAC layer is implemented in
the network adapter (NIC).  Common MAC standards
are the CSMA/CD architecture used in Ethernet and
various token passing methods such as those used in
Token Ring, FDDI and MAP.  See "LANs" under data
link protocol.



Mac OS
(MACintosh Operating System)  In late 1994, Apple
formally renamed its System 7 operating system Mac
OS and introduced the Mac OS logo.  However, the
term has been used for years to refer to the
current version of the operating system running in
the Macintosh.



Mac to DOS
See Mac to PC.



Mac to midrange
Using the Macintosh as the terminal to IBM S/3x and
AS/400 computers.  Apple and third party
connectivity products add local processing and a
friendly interface to IBM midrange computers.



Mac to PC
The following DOS and Windows software packages are
designed for transferring Macintosh files from the
Mac to the PC via floppy disk.  These programs read
the Mac disks in the PC's 3.5" floppy drive.

     MacAccess
     Hypro Technologies, Culver City, CA
     310/473-0328

     MacDisk
     Insignia Solutions, Mountain View, CA
     800/848-7677

     Mac-In-DOS
     Mac-In-DOS Windows
     Pacific Microelectronics, Mountain View, CA
     800/628-3475

     Mac-to-DOS for Windows
     Peripheral Land Inc., Fremont, CA
     800/288-8754

     TransferPro for Windows
     Digital Instrumentation Technology,
     Los Alamos, NM
     800/467-1459





MacAPPC
LU 6.2-compliant software from Apple Computer that
allows a Macintosh to be a peer to an IBM APPC
application.



MacDFT
Software that provides 3270 emulation for the
Macintosh from Apple.  It accompanies Apple's
TwinAx/Coax board and supports CUT and DFT modes
and DFT multiple sessions under SNA.



MacDraw Pro
A Macintosh drawing program from Claris Corporation
that is an enhanced version of the original MacDraw
from Apple and includes full on-screen slide
presentation capability.  It is used for
illustrations and elementary CAD work.  MacDraw
files are a subset of the Claris CAD file format.



Mach
A UNIX-like operating system developed at Carnegie-
Mellon University.  It is designed with a
microkernel architecture that makes it easily
portable to different platforms.  IBM has based its
future operating systems on Mach.  See Workplace.



machine
Any electronic or electromechanical unit of
equipment.  A machine is always hardware; however,
"engine" refers to hardware or software.



machine address
Same as absolute address.



machine code
Same as machine language.



machine cycle
The shortest interval in which an elementary
operation can take place within the processor.  It
is made up of some number of clock cycles.



machine dependent
Refers to software that accesses specific hardware
features and runs in only one kind of computer.
Contrast with machine independent.  See device
dependent.



machine independent
Refers to software that runs in a variety of
computers.  The hardware-specific instructions are
in some other program (operating system, DBMS,
etc.).  Contrast with machine dependent.  See
device independent.



machine instruction
An instruction in machine language.  Its anatomy is
a verb followed by one or more nouns:

     OP CODE    OPERANDS (one or more)
     (verb)     (nouns)

   The op code is the operation to be performed
(add, copy, etc.), while the operands are the data
to be acted upon (add a to b).  There are always
machine instructions to INPUT and OUTPUT, to
process data by CALCULATING, COMPARING and COPYING
it, and to go to some other part of the program
with a GOTO instruction.  See hardware platforms
and computer.



machine language
The native language of the computer.  In order for
a program to run, it must be presented to the
computer as binary-coded machine instructions that
are specific to that CPU model or family.  Although
programmers are sometimes able to modify machine
language in order to fix a running program, they do
not create it.  Machine language is created by
programs called assemblers, compilers and
interpreters, which convert the lines of
programming code a human writes into the machine
language the computer understands.

   Machine language tells the computer what to do
and where to do it.  When a programmer writes:
total = total + subtotal, that statement is
converted into a machine instruction that tells the
computer to add the contents of two areas of memory
(where TOTAL and SUBTOTAL are stored).

   A programmer deals with data logically, "add
this, subtract that," but the computer must be told
precisely where this and that are located.

   Machine languages differ substantially.  What
may take one instruction in one machine can take 10
instructions in another.  See hardware platforms,
assembly language and interpreter.



machine readable
Data in a form that can be read by the computer,
which includes disks, tapes and punched cards.
Printed fonts that can be scanned and recognized by
the computer are also machine readable.



Macintosh
A series of 32-bit personal computers from Apple
introduced in 1984.  It uses the Motorola 68000 CPU
family and an operating system that simulates a
user's desktop on screen.  The Mac's graphics-based
user interface has provided a measure of
consistency and ease of use that is unmatched.  The
Macintosh family is the largest non-IBM compatible
personal computer series in use.

   Introduced in 1984 as a floppy-based computer
with 128K of memory, its "high-rise" cabinet and
built-in 9" monochrome screen were unique.  This
design is retained in the Classic model, while the
rest of the line is now clothed in traditional
cabinetry.

   In 1994, Apple introduced the PowerMacs, the
next generation of Macintoshes, which use the
PowerPC CPU chip.  PowerMacs run native PowerPC
applications and emulate traditional Macintosh
680x0 applications as well as DOS and Windows
applications.


            MACINTOSH SPECIFICATIONS

                             3.5"
             Clock Bus      Floppy  Hard
       68xxx Speed Size RAM  Disk   Disk    Screen
Model     CPU  Mhz Bits( MBytes  )(Mbytes )   Res.

128*       000  8 16128K 400K   20    512x342
512*       000  8 16512K 400K Ĵ 9" Mono
Plus*      000  8 161-4  800K        Black on
                         Ĵ        White
SE*        000  8 161-4  3.5"  20-160
SE30*      030 16 321-8  Super       
Classic*   000  8 161-4  Drive       
Classic II 030 16 162-10       40-80 
Color Classic                        
 256 cols  030 16 164-10       80-16010" diag
II*        020 16 321-8              
IIx*       030 16 321-8              640x480
IIcx*      030 16 321-8              12" mono
IIci*      030 25 325-32       80-23014"color
IIfx*      030 40 324-32       80+   
IIsi*      030 20 323-17       40-80 640x870
IIvi*      030 16 324-20       40-40015" mono
IIvx*      030 32 324-20       40-400
LC*        020 16 161-10       40-80 832x624
LC II*     030 16 162-10       40-80 17"color
LC III     030 25 324-36       80-160
LC 475     040 25 324-36       80-1601152x870
LC 520     030 25 324-36       80-16021"color
Centris610*040 20 324-68      80-500 
Centris650*040 25 324-132     80-500 
Portable*  000 16 321-9         40   am

Quadra
605        040 25 324-36       80-160**
610        040 25 324-68      160-230**
650        040 33 324-132      80-500**
700*       040 25 324-20       80-400**
800        040 33 328-136     230-1G **
900*       040 25 324-64      160-400**
950        040 33 328-256     230-1G **
660 av     040 25 328-68      230-1G **
840 av     040 40 328-128     230-1G **

Performa (consumer product line)
200        030 16 164-10       80    640x480
400        030 16 164-10       80    14"
405        030 16 164-10       80    256 cols
430        030 16 164-10       120   
                                     
450        030 25 164-36       120   32K cols
600        030 32 164-68       80-40064K cols

PowerBook Portables
100*       000 16 162-8         20   pm
140*       030 16 162-8        20-40 pm
145*       030 25 164-8        40-80 pm
145B       030 25 164-8        40-80 pm
160*       030 25 164-14      40-120 pm
165        030 33 164-14      80-160 pm
165c color 030 33 164-14      80-120 pm
170*       030 25 164-8         40   Am
180        030 33 164-14      80-120 Am
180c color 030 33 164-14      80-160 Am
210 Duo*   030 25 164-24      80     pm
230 Duo    030 33 164-24      80-160 Am
250 Duo    030 33 164-24      200    Am
270cDuo    030 33 164-32      240    Am

Duo line designed to insert into docking station
for desktop look.
 * No longer made as of 11/93
** Built-in 24-bit color
pm passive matrix LCD
Am active matrix LCD




Macintosh extension
Additional software functions for the Macintosh,
which include drivers and other enhancements to the
operating system.  In System 7, system extensions
reside in the Extensions folder.  Mac extensions
are the counterpart to the CONFIG.SYS file for DOS.



Macintosh Toolbox
Software routines that perform the graphical user
interface functions in the Macintosh.  Apple is
licensing the Mac Toolbox to vendors developing a
version of PowerOpen for the PowerPC.  This is the
first time Apple has licensed the Toolbox.  See
MAS.



Macintosh User Group
See MUG.



Macintosh user interface
The method of operating a Macintosh, which was
originally developed by Xerox and introduced on the
Xerox Star in 1981.  It uses a graphics-based
screen that places familiar objects on a two-
dimensional desktop.  Programs, files, folders and
disks are represented by small pictures (icons).
An object is selected by moving a mouse over the
real desktop, which correspondingly moves a pointer
on the screen desktop.  When the pointer touches an
icon, the object is selected by clicking the mouse
button.

   A hierarchical file system is provided that lets
a user "drag" a document icon into and out of a
folder icon.  Folders can also contain other
folders.  To delete a document, its icon is
literally dragged into a trash can icon.

   The Macintosh always displays a row of menu
titles at the top of the screen.  The full menu
appears as if it were pulled down from the top of
the screen when selected.  With the mouse button
held down, the option within the menu is selected
by pointing to it and releasing the button.

   Unlike the PC world, which, before Windows, left
the design of the user interface up to the software
developer, Macintosh developers always conform to
the Mac interface.  As a result, users feel more
comfortable with new programs from the start.

   In operation, the operating system and
applications are almost indistinguishable, and
Apple keeps technical jargon to a minimum.

   Early Mac applications had little regard for
experienced typists, forcing them to use the mouse
instead of well-designed keyboard commands.
Subsequent versions offer both methods and have
greatly improved.

   The Macintosh style has been adapted to many
environments, including Windows, OS/2 and Motif.



MacIRMA
A 3270 emulator board for the Macintosh from DCA,
Inc., Alpharetta, GA.  It is the Macintosh
counterpart of the IRMA board, the first 3270
emulator for PCs.  See Irma software.



MacLink Plus
A Macintosh file transfer program from DataViz
Corporation, Trumbull, CT, that provides document
conversion for a wide variety of Mac and PC
formats.  Versions are also available for Sun, NeXT
and Wang systems.



MacPaint II
A full-featured Macintosh paint program from Claris
that was originally developed by Apple and bundled
with every Mac up until the Mac Plus.  MacPaint's
PICT file format is used for printing the screen.
By pressing Command-shift-3, the current screen is
stored in a PICT file for printing either in
MacPaint or other program.



macro
(1) A series of menu selections, keystrokes and/or
commands that have been recorded and assigned a
name or key combination.  When the macro name is
called or the macro key combination is pressed, the
steps in the macro are executed from beginning to
end.

   Macros are used to shorten long menu sequences
as well as to create miniature programs within an
application.  Macro languages often include
programming controls (IF THEN, GOTO, WHILE, etc.)
that automate sequences like any programming
language.  See macro recorder, batch file and shell
script.

(2) In assembly language, a prewritten subroutine
that is called for throughout the program.  At
assembly time, the macro calls are substituted with
the actual subroutine or instructions that branch
to it.  The high-level language equivalent is a
function.

(3) In dBASE programming, a variable which
references another variable that actually contains
the data.  At runtime, the macro variable is
substituted with the data variable.



macro assembler
An assembly language that allows macros to be
defined and used.



macro call
Same as macro instruction.



macro generator
See macro recorder.



macro instruction
An instruction that defines a macro.  In assembly
language, MACRO and ENDM are examples that define
the beginning and end of a macro.  In C, the
#DEFINE statement is used.



macro language
(1) Commands used by a macro processor.  Same as
script.

(2) An assembly language that uses macros.



macro processor
(1) Software that creates and executes macros from
the keyboard.

(2) The part of an assembler that substitutes the
macro subroutines for the macro calls.



macro recorder
A program routine that converts menu selections and
keystrokes into a macro.  A user turns on the
recorder, calls up a menu, selects a variety of
options, turns the recorder off and assigns a key
command to the macro.  When the key command is
pressed, the selections are executed.



Macromedia
(Macromedia, Inc., San Francisco, CA)  A software
company specializing in multimedia authoring tools.
It was founded in 1992 by the merger of Aurhorware,
Inc., which was founded in 1984, and MacroMind-
Paracomp.  Macromind was founded in 1984 and merged
with Paracomp in 1991.  Its primary products are
Aurthorware Professional and Macromedia Director,
both for Macintosh and Windows.



MacroMind
See Macromedia.



MacTerminal
Macintosh terminal emulation software from Apple
that allows a Mac to function as an IBM 3278 Model
2 (when used with an AppleLine Protocol Converter)
or Digital VT 52 or VT 100 terminal.



MacTwin
Mac to IBM midrange connectivity from Andrew/KMW,
which includes a card for the Mac that connects to
the twinax cabling from the S/3x or AS/400.
Software for the Mac provides 5250, 3196 and 3197
emulation.



MacWrite II
A full-featured Macintosh word processing program
from Claris Corporation, that was originally
packaged with every Mac 128 and 512.



mag
Abbreviation for "magnetic."



Magellan
A disk management utility for PCs from Lotus that
searches for file names and contents.  It
popularized the file viewer, which lets you look
into various data files as if you were using the
applications that created them.



Magic Cap
(Magic Communicating Applications Platform)  An
object-oriented control program from General Magic
for personal intelligent communicating devices
(PDAs, hand-held units, etc.) that includes the
Telescript language.



magnetic card
(1) See magnetic stripe.

(2) Magnetic tape strips used in early data storage
devices and word processors.  See CRAM, RACE and
Data Cell.



magnetic coercivity
The amount of energy required to alter the state of
a magnet.  The higher a magnetic disk's coercivity
index, the more data it can store.



magnetic disk
The primary computer storage device.  Like tape, it
is magnetically recorded and can be re-recorded
over and over.  Disks are rotating platters with a
mechanical arm that moves a read/write head between
the outer and inner edges of the platter's surface.
It can take as long as one second to find a
location on a floppy disk to as short as one
millisecond on an ultra-fast hard disk.  See floppy
disk and hard disk.


                Tracks and Sectors
The disk surface is divided into concentric tracks
(circles within circles).  The thinner the tracks,
the more storage.  The data bits are recorded as
tiny spots on the tracks.  The tinier the spot, the
more bits per inch and the greater the storage.
Most disks hold the same number of bits on each
track, even though the outer tracks are physically
longer than the inner ones.  Some disks pack the
bits as tightly as possible within each track.

   Tracks are further divided into sectors, which
hold the least amount of data that can be read or
written at one time; for example, READ TRACK 7
SECTOR 24.  In order to update the disk, one or
more sectors are read into the computer, changed
and written back to disk.  The operating system
figures out how to fit data into these fixed
spaces.  See hard disk and floppy disk.



magnetic disk & tape
The primary computer storage media.  The choice
depends on accessing requirements.  Disk is direct
access; tape is sequential access.  Locating a
program or data on disk can take a fraction of a
second.  On tape, it can take seconds or minutes.

   On minis and mainframes, disks are used for
daily transaction processing, and tapes are used
for backup and history.  Tapes have traditionally
been more economical for archival storage and
easier to transport than disk packs.

   For personal computers, hard disks are used for
all interactive processing, and both floppy disks
and tapes are used for backup.  Bernoulli disks and
removable hard disks are increasingly becoming
backup alternatives.

   In time, magnetic disks will be as obsolete as
punched cards.  Optical disks are getting faster
and cheaper, and optical technologies that employ
no moving parts will undoubtedly supersede them
all.  Compared to the magical technology within the
chip, whirling chunks of metal around is rather old
fashioned, don't you think?



magnetic drum
An early high-speed, direct access storage device
that used a magnetic-coated cylinder with tracks
around its circumference.  Each track had its own
read/write head.



magnetic field
An invisible energy emitted by a magnet.  Same as
flux.



magnetic ink
A magnetically detectable ink used to print the
MICR characters that encode account numbers on bank
checks.



magnetic oxide
See ferric oxide.



magnetic recording
With regard to computers, the technique used to
record, or write, digital data in the form of tiny
spots (bits) of negative or positive polarity on
tapes and disks.  A read/write head discharges
electrical impulses onto the moving ferromagnetic
surface.  Reading is accomplished by sensing the
polarity of the bit with the read/write head.



magnetic stripe
A small length of magnetic tape adhered to ledger
cards, badges and credit cards.  It is read by
specialized readers that may be incorporated into
accounting machines and terminals.  Due to heavy
wear, the data on the stripe is in a low-density
format that may be duplicated several times.



magnetic tape
A sequential storage medium used for data
collection, backup and historical purposes.  Like
videotape, computer tape is made of flexible
plastic with one side coated with a ferromagnetic
material.  Tapes come in reels, cartridges and
cassettes of many sizes and shapes.  Although still
used, the 1/2" open-reel tape from the earliest
days of computers has been mostly superseded by
cartridges with enhanced storage capacities.

   Locating a specific item on tape requires
reading everything in front of it.  There is no
fast forward.  In order to add and delete records,
the current tape is input to the computer and a
blank tape is used for output.  If data on tape is
only changed and the byte count is not altered,
some tape drives can update in place by reading a
block of data and writing back over the same area.

   Except for QIC and DAT tape cartridges, which
use serpentine and helical scan methods, data bits
are recorded on parallel tracks that run the length
of the tape.  For example, 9-track tape holds one
byte of data across the tape's width (8 bits plus
parity).  Mainframe tape cartridges use 18- and 36-
track tape, placing two and four bytes across the
width.  Data is recorded in blocks of contiguous
bytes, separated by a space called an interrecord
or interblock gap.

   Tape is more economical than disks for archival
data.  However, if tapes are stored for the
duration, they must be periodically recopied or the
tightly coiled magnetic surfaces may contaminate
each other.

   Storage capacity is measured in bits per inch
(bpi).  The once-widely-used 1/2" reel-to-reel tape
formats store one byte from top to bottom on nine
parallel tracks at 200, 556, 800, 1650 and 6250
bpi.  IBM's 3480 and 3490 tape cartridges store two
to four bytes on 18 or 36 parallel tracks at 38000
bpi.

   Tape drive speed is measured in inches per
second (ips), thus, transfer rate = ips X bpi.



magneto-optic
A high-density, erasable recording method.  Data is
recorded magnetically like disks and tapes, but the
bits are much smaller, because a laser is used to
pinpoint the bit.  The laser heats the bit to 150
Celsius, at which temperature the bit is realigned
when subjected to a magnetic field.  In order to
record new data, existing bits must first be set to
zero.  See Curie point, Kerr effect and optical
disk.



magneto-resistance
A high-density magnetic recording method that uses
two technologies for the read/write head.  The
write head is the standard inductive type, but the
magneto-resistance read head can read a fainter
signal on the disk, thus allowing the bits to be
packed more tightly together.



magnetographic
A non-impact printer technology from Groupe Bull
that prints up to 90 ppm.  A magnetic image is
created by a set of recording heads across a
magnetic drum.  Monocomponent toner is applied to
the drum to develop the image, which is transferred
to paper by light pressure and an electrostatic
field.  The toner is then fused by heat.  The print
quality is not as good as a laser printer, but the
machines require less maintenance.



mail API
See messaging API and MAPI.



mail box
See mailbox.



mail enabled
Refers to an application that has built-in,
although typically very limited, mail capabilities.
For example, it can send or send and receive a file
that it has created over one or more messaging
systems.  See messaging API.



mail merge
Printing customized form letters.  A common feature
of a word processor, it uses a letter and a name
and address list.  In the letter, Dear A: Thank you
for ordering B from our C store..., A, B and C are
merge points into which data is inserted from the
list.  See field squeeze and line squeeze.



mail protocol
See messaging protocol and messaging system.



mail system
See electronic mail and messaging system.



mailbox
A simulated mailbox on disk that holds incoming
electronic mail.



main distribution frame
See MDF.



main line
See main loop.



main loop
The primary logic in a program.  It contains the
instructions that are repeated after each event or
transaction has been processed.  See loop.



main memory
Same as memory.



main storage
Same as memory.



mainframe
A large computer.  In the "ancient" mid 1960s, all
computers were called mainframes, since the term
referred to the main CPU cabinet.  Today, it refers
to a large computer system.

   There are small, medium and large-scale
mainframes, handling from a handful to several
thousand online terminals.  Large-scale mainframes
can have hundreds of megabytes of main memory and
terabytes of disk storage.  Large mainframes use
smaller computers as front end processors that
connect to the communications networks.

   The original mainframe vendors were Burroughs,
Control Data, GE, Honeywell, IBM, NCR, RCA and
Univac, otherwise known as "IBM and the Seven
Dwarfs."  After GE and RCA's computer divisions
were absorbed by Honeywell and Univac respectively,
the mainframers were known as "IBM and the BUNCH."


                 There Was a Time
There was a time when mainframes meant
"complicated" and required the most expertise in
programming and operations.  That is no longer the
case.  PCs and PC networks make mainframes look
easy.  Nothing is more complicated than the
PC/DOS/Windows environment.  Add NetWare, Windows
NT and other network operating systems, throw in a
little UNIX for good measure, and you have
enterprise computing at its most complex since the
beginning of written history.



maintenance
(1) Hardware maintenance is the testing and
cleaning of equipment.

(2) Information system maintenance is the routine
updating of master files, such as adding and
deleting employees and customers and changing
credit limits and product prices.

(3) Software, or program, maintenance is the
updating of application programs in order to meet
changing information requirements, such as adding
new functions and changing data formats.  It also
includes fixing bugs and adapting the software to
new hardware devices.

(4) Disk or file maintenance is the periodic
reorganizing of disk files that have become
fragmented due to continuous updating.



maintenance credits
Monetary credits issued to a customer by the vendor
for qualified periods during which the vendor's
products are not functioning properly.



maintenance service
A service provided to keep a product in good
operating condition.



major key
The primary key used to identify a record, such as
account number or name.



make
To compile a multi-module program.  The make
utility recompiles only those modules that have
been updated since the last compilation.



male connector
A plug that is designed to fit into a particular
socket.



Maltron keyboard
A keyboard that uses independent left- and right-
hand modules shaped to conform to the natural
position of the hands, designed to prevent strain
(RSI).



MAN
(Metropolitan Area Network)  A communications
network that covers a geographic area such as a
city or suburb.  See LAN and WAN.



man machine interface
Same as user interface.



management console
A terminal or workstation used to monitor and
control a network.



Management Information Base
See MIB.



management information system
See MIS.



management science
The study of statistical methods, such as linear
programming and simulation, in order to analyze and
solve organizational problems.  Same as operations
research.



management support
See DSS and EIS.



management system
The leadership and control within an organization.
It is made up of people interacting with other
people and machines that, together, set the goals
and objectives, outline the strategies and tactics,
and develop the plans, schedules and necessary
controls to run an organization.



Manchester Code
A self-clocking data encoding method that divides
the time required to define the bit into two
cycles.  The first cycle is the data value (0 or 1)
and the second cylce provides the timing by
shifting to the opposite state.



MANTIS
An application development language from Cincom
Systems, Inc., Cincinnati, OH, that runs on IBM
mainframes, VAXs and other mainframes.  It provides
procedural and non-procedural languages for
developing prototypes and applications and works
with Cincom's SUPRA database, DB2 and IMS.



mantissa
The numeric value in a floating point number.  See
floating point.



MAP
(Manufacturing Automation Protocol)  A
communications protocol introduced by General
Motors in 1982.  MAP provides common standards for
interconnecting computers and programmable machine
tools used in factory automation.  At the lowest
physical level, it uses the IEEE 802.4 token bus
protocol.

   MAP is often used in conjunction with TOP, an
office protocol developed by Boeing Computer
Services.  TOP is used in the front office and MAP
is used on the factory floor.



map
(1) A set of data that has a corresponding
relationship to another set of data.

(2) A list of data or objects as they are currently
stored in memory or disk.

(3) To transfer a set of objects from one place to
another.  For example, program modules on disk are
mapped into memory.  A graphic image in memory is
mapped onto the video screen.  An address is mapped
to another address.

(4) To relate one set of objects with another.  For
example, a logical database structure is mapped to
the physical database.  A vendor's protocol stack
is mapped to the OSI model.



MAPI
(Mail API)  A programming interface that enables an
application to send and receive mail over the
Microsoft Mail messaging system.  Simple MAPI is a
subset of MAPI that includes a dozen functions for
sending and retrieving mail.



MAPPER
(MAintaining, Preparing and Processing Executive
Reports)  A Unisys mainframe fourth-generation
language.  In 1980, it was introduced as a high-
level report writer and was later turned into a
full-featured development system used successfully
by non-technical users.



mapping
See map and digital mapping.



marginal test
A system test that introduces values far above and
far below the expected values.



mark
(1) A small blip printed on or notched into various
storage media used for timing or counting purposes.

(2) To identify a block of text in order to perform
some task on it such as deletion, copying and
moving.

(3) To identify an item for future reference.

(4) In digital electronics, a 1 bit.  Contrast with
space.

(5) On magnetic disk, a recorded character used to
identify the beginning of a track.

(6) In optical recognition and mark sensing, a
pencil line in a preprinted box.

(7) On magnetic tape, a tape mark is a special
character that is recorded after the last character
of data.



Mark I
An electromechanical calculator designed by
professor Howard Aiken, built by IBM and installed
at Harvard in 1944.  It strung 78 adding machines
together to perform three calculations per second.
It was 51 feet long, weighed five tons and used
punched cards and typewriters for I/O.  Made of
765,000 parts, it sounded like a thousand knitting
needles according to Admiral Grace Hopper.  The
experience helped IBM develop its own computers a
few years later.



MARK IV
See Crosstalk and MARK IX.



MARK IX
An application generator from Sterling Software's
Answer Systems Division, Woodland Hills, CA, that
runs on IBM mainframes and personal computers.  It
stems from MARK IV, the first report writer to use
fill-in-the-blanks forms.  MARK V was a subsequent
online version.



mark sensing
Detecting pencil lines in predefined boxes on paper
forms.  The form is designed with boundaries for
each pencil stroke that represents a yes, no,
single digit or letter, providing all possible
answers to each question.  A mark sense reader
detects the marks and converts them into digital
code.



MAS
(1) (Multiple Address System)  A radio service in
the 932-932.5 and 941-941.5Mhz frequency that
covers a 25-mile radius from the antenna.  It is
used for sensor-based and transaction systems
(ATMs, reservations, alarms, traffic control,
etc.).

(2) (Multiple Award Schedule)  A list of approved
products available for purchase by U.S. government
agencies.

(3) (Macintosh Application System)  Software that
allows a Macintosh to run in a PowerPC.  It
includes a 68000 emulator and the Macintosh
Toolbox, which contains the Mac's graphical
functions.  The Macintosh graphical user interface
runs native in the PowerPC while only the Motorola
68000 instructions are emulated.



mask
(1) A pattern used to transfer a design onto an
object.  See photomask.

(2) A pattern of bits used to accept or reject bit
patterns in another set of data.  For example, the
Boolean AND operation can be used to match a mask
of 0s and 1s with a string of data bits.  When a 1
occurs in both the mask and the data, the resulting
bit will contain a 1 in that position.

   Hardware interrupts are often enabled and
disabled in this manner with each interrupt
assigned a bit position in a mask register.



mask bit
A 1 bit in a mask used to control the corresponding
bit found in data.



maskable interrupts
Hardware interrupts that can be enabled and
disabled by software.



masked
A state of being disabled or cut off.



MASM
See macro assembler.



mass storage
A high-capacity, external storage such as disk or
tape.



massage
To process data.



massively parallel processor
See MPP.



master
Primary, controlling.  See master-slave
communications and master file.



master card
A master record in punched card format.



master clock
A clock that provides the primary source of
internal timing for a processor or stand-alone
control unit.



master console
The main terminal used by the computer operator or
systems programmer to command the computer.



master control program
See operating system.



master file
A collection of records pertaining to one of the
main subjects of an information system, such as
customers, employees, products and vendors.  Master
files contain descriptive data, such as name and
address, as well as summary information, such as
amount due and year-to-date sales.  Contrast with
transaction file.

   Following are the kinds of fields that make up a
typical master record in a business information
system.  There can be many more fields depending on
the organization.  The "key" fields below are the
ones that are generally indexed for matching
against the transaction records as well as fast
retrieval for queries.  The account number is
usually the primary key, but name may also be
primary.  There can be secondary indexes; for
example, in an inverted file structure, almost all
the fields could be indexed.  See transaction file
for examples of typical transaction records.


       EMPLOYEE MASTER RECORD
  key  Employee account number
  key  Name (last)
       Name (first)
       Address, city, state, zip
       Hire date
       Birth date
       Title
       Job class
       Pay rate
       Year-to-date gross pay

       CUSTOMER MASTER RECORD
  key  Customer account number
  key  Name
       Bill-to address, city, state, zip
       Ship-to address, city, state, zip
       Credit limit
       Date of first order
       Sales-to-date
       Balance due

       VENDOR MASTER RECORD
  key  Vendor account number
  key  Name
       Address, city, state, zip
       Terms
       Quality rating
       Shipping method

       PRODUCT MASTER RECORD
  key  Product number
  key  Name
       Description
       Quantity on hand
       Location
       Primary vendor
       Secondary vendor




master record
A set of data for an individual subject, such as a
customer, employee or vendor.  See master file.



master-slave communications
Communications in which one side, called the
master, initiates and controls the session.  The
other side (slave) responds to the master's
commands.



math coprocessor
A mathematical circuit that performs high-speed
floating point operations.  It may be built into
the CPU chip, as in the 486DX, or it may be a
separate chip, such as the 387 and 487, which work
with the 386 and 486SX respectively.

   The math coprocessor is used primarily in CAD
and spreadsheet applications to improve
performance.  It is of such importance to
computation-intensive CAD work, that some CAD
programs will not operate without a coprocessor.
Spreadsheet programs may test for its existence and
then use it, but it is not mandatory.  See array
processor and vector processor.



Mathcad
Mathematical software from Mathsoft, Inc.,
Cambridge, MA, for PCs and Macs.  It allows
complicated mathematical equations to be expressed,
performed and displayed.



Mathematica
Mathematical software for PCs and Macs from Wolfram
Research, Inc., Champaign, IL.  It includes
numerical, graphical and symbolic computation
capabilities, all linked to the Mathematica
programming language.  Its use requires a math
coprocessor.



mathematical expression
A group of characters or symbols representing a
quantity or an operation.  See arithmetic
expression.



mathematical function
A rule for creating a set of new values from an
existing set; for example, the function f(x) = 2x
creates a set of even numbers (if x is a whole
number).



matrix
An array of elements in row and column form.  See
x-y matrix.



matrix printer
See dot matrix and printer.



MAU
(Multi-station Access Unit)  A central hub in a
token ring local area network.  See hub.



maximize
In a graphical environment, to enlarge a window to
full size.  Contrast with minimize.



MB, Mb
(1) (MB, upper case "B") (MegaByte or MotherBoard)
MB mostly stands for megabyte, but on ads for raw
components, it may refer to motherboard.

(2) (Mb, lower case "b") (MegaBit)  Adherence to
"b" and "B" for bit and byte is not always
followed.  See space/time for common usage.



Mbit
See megabit.



Mbits/sec
(MegaBITS per SECond)  One million bits per second.
See space/time.



Mbone
(Multicast backBONE)  A collection of sites on the
Internet that support the IP multicasting protocol
(one-to-many) and allow for live audio and
videoconferencing.



MBps, Mbps
(MegaBytes Per Second, MegaBits Per Second)  One
million bytes per second, one million bits per
second.  Adherence to "b" and "B" for bit and byte
is not always followed.  See space/time for common
usage.



Mbs
(MegaBits per Second)  Same as Mbps.



Mbyte
See megabyte.



Mbytes/sec
(MegaBYTES per SECond)  One million bytes per
second.  See space/time.



MC68000
See 68000.



MCA
See Micro Channel.



MCB
(Memory Control Block)  An identifier (16-bytes)
that DOS places in front of each block of memory it
allocates.



MCGA
(Multi Color Graphics Array)  An IBM video display
standard built into low-end PS/2 models.  It is not
well supported by software vendors.  See PC display
modes.



MCI
(Media Control Interface)  A high-level programming
interface from IBM/Microsoft for controlling
multimedia devices.  It includes text commands such
as open, play and close for languages such as
Visual Basic, as well as functions for languages
such as C.  See RIFF and AVI.



MCI decision
An FCC decree in 1969 that granted MCI the right to
compete with the Bell System by providing private,
intercity telecommunications services.



McIntosh
See Macintosh.



MCM
(MultiChip Module or MicroChip Module)  A chip
housing that uses a ceramic base and contains two
or more raw chips closely connected with high-
density lines.  This packaging method saves space
and speeds processing due to short leads between
chips.

   MCMs were originally called microcircuits or
hybrid microcircuits, since this technique is well
suited for mixing analog and digital components
together.

   MCMs are a more workable solution to wafer scale
integration, in essence, building the "superchip,"
which has been very difficult to implement.



MCP
See Microsoft Certified Professional.



MCU
(1) (MicroController Unit)  A control unit on a
single chip.

(2) (Multipoint Control Unit)  A device that
connects multiple sites for audio and video
conferencing.



MD
See minidisc.



MDA
(Monochrome Display Adapter)  The first IBM PC
monochrome video display standard for text only.
Due to its lack of graphics, MDA cards were often
replaced with Hercules cards, which provided both
text and graphics.  See PC display modes.



MDBS IV
A DBMS from Micro Data Base Systems, Inc.,
Lafayette, IN, that runs on DOS, OS/2, UNIX, MPE
and VMS servers.  Noted for its performance and
maturity (in 1984, MDBS III was the first
client/server DBMS), it provides a superset of
hierarchical, network and relational storage
concepts.  M/4 for Windows is a single-user Windows
version.



MDF
(Main Distribution Frame)  A connecting unit
between external and internal lines.  It allows for
public or private lines coming into the building to
connect to internal networks.  See CDF.



MDI
(1) (Multiple Document Interface)  A Windows
function that allows an application to display and
lets the user work with more than one document at
the same time.  If the application is not
programmed for MDI and you want to work with
multiple documents of the same type concurrently,
you must load the application again for each
subsequent document.  Contrast with SDI.

(2) (Medium Dependent Interface)  Refers to an
Ethernet port connection.  The MDI-X port on an
Ethernet hub is used to connect to a workstation
(the X stands for crossing the transmit and recieve
lines).  An MDI port (not crossed) is used to
connect to the MDI-X port of another hub.



mean time between failure
See MTBF.



mean time to repair
See MTTR.



mechanical mouse
A mouse that uses a rubber ball that rolls against
wheels inside the unit.  Contrast with optical
mouse.



media
A material that stores or transmits data, for
example, floppy disks, magnetic tape, coaxial cable
and twisted pair.



media access method
See "LANs" under data link protocol.



media control
Also called media processing, in computer telephony
it refers to some processing or altering of the
call; for example, digitizing the content.
Contrast with call control.



Media Control Interface
See MCI.



media conversion
Converting data from one storage medium to another,
such as from disk to tape or from one type of disk
pack to another.



media failure
A condition of not being able to read from or write
to a storage device, such as a disk or tape, due to
a defect in the recording surface.



Media Player
A Windows multimedia utility that is used to play
sound and video files.



Media Vision
(Media Vision Technology, Inc., Fremont, CA)  A
manufacturer of Sound Blaster-compatible products
for PCs founded in 1990.  Media Vision was the
first to introduce a 16-bit sound card (Pro Audio
line) and multimedia upgrade kit.



MediaMap
(MediaMap, Cambridge, MA)  A public relations
information source for the high-tech industry that
maintains editorial lists and schedules for every
major computer media organization, including trade
and national press, TV and radio, user groups and
syndicated columns.  Its MediaManager software for
PCs and Macs provides a complete media contact
management system and allows searches based on
editorial niche and scheduled story opportunities.



medium frequency
An electromagnetic wave that oscillates in the
range from 300,000 to 3,000,000 Hz.  See
electromagnetic spectrum.



meg
Same as mega.



mega
(1) Million.  Abreviated "M."  It often refers to
the precise value 1,048,576 since computer
specifications are usually binary numbers.  See
binary values and space/time.

(2) (MEGA)  A personal computer series from Atari
that is Motorola 68000 based, runs under GEM and
the TOS operating system and includes a MIDI
interface.  It is ST compatible.



megabit
One million bits.  Also Mb, Mbit and M-bit.  See
mega and space/time.



megabyte
One million bytes.  Also MB, Mbyte and M-byte.  See
mega and space/time.



megaflops
(mega FLoating point OPerations per Second)  One
million floating point operations per second.



megahertz
One million cycles per second.  See MHz.



megapel display
In computer graphics, a display system that handles
a million or more pixels.  A resolution of 1,000
lines by 1,000 dots requires a million pixels for
the full screen image.



membrane keyboard
A dust and dirtproof keyboard constructed of two
thin plastic sheets (membranes) that contain
flexible printed circuits made of electrically
conductive ink.  The top membrane is the printed
keyboard and a spacer sheet with holes is in the
middle.  When a user presses a simulated key, the
top membrane is pushed through the spacer hole and
makes contact with the bottom membrane, completing
the circuit.



memo field
A data field that holds a variable amount of text.
The text may be stored in a companion file, but it
is treated as if it were part of the data record.
For example, in the dBASE command list name,
biography, name is in the data file (DBF file) and
biography could be a memo field in the text file
(DBT file).



memory
The computer's workspace (physically, a collection
of RAM chips).  It is an important resource, since
it determines the size and number of programs that
can be run at the same time, as well as the amount
of data that can be processed instantly.

   All program execution and data processing takes
place in memory.  The program's instructions are
copied into memory from a disk or tape and are then
extracted from memory into an electronic circuit
for analysis and execution.  The instructions
direct the computer to input data into memory from
a keyboard, disk, tape or communications channel.

   As data is entered into memory, the previous
contents of that space are lost.  Once the data is
in memory, it can be processed (calculated,
compared and copied).  The results are sent to a
screen, printer, disk, tape or communications
channel.

   Memory is like an electronic checkerboard, with
each square holding one byte of data or
instruction.  Each square has a separate address
like a post office box and can be manipulated
independently.  As a result, the computer can break
apart programs into instructions for execution and
data records into fields for processing.


          Memory Doesn't Usually Remember
Oddly enough, the computer's memory doesn't
remember anything when the power is turned off.
That's why you have to save your files before you
quit your program.  Although there are memory chips
that do hold their content permanently (ROMs,
PROMs, EPROMs, etc.), they're used for internal
control purposes and not for the user's data.

     "Remembering" memory in a computer system is
its disks and tapes, and although they are also
called memory devices, many prefer to call them
storage devices (as we do) in order to
differentiate them from internal memory.  Perhaps
in time, memory will refer to disks exclusively and
RAM will refer to working memory.  Until then, its
usage for both RAM and disk only adds confusion to
the most confusing industry on earth.

   Other terms for memory are RAM, main memory,
main storage, primary storage, read/write memory,
core and core storage.



memory allocation
Reserving memory for specific purposes.  Operating
systems generally reserve all the memory they need
at startup.  Application programs use memory when
loaded and may allocate more after being loaded.
If there is not enough free memory, they cannot
run.

   On a personal computer, memory can be allocated
for a disk cache, which retains large chunks of
data from the disk in faster RAM.  However, a large
disk cache that speeds up one application may slow
down another because there is less normal memory
available.

   Memory can be allocated for a RAM disk, which
simulates a disk drive in memory.  Disk files are
copied to the RAM disk and all accesses take place
in faster memory.  RAM disks may dramatically speed
up one program and have little effect on others.
Like the disk cache, it takes away from the total
available memory.

   On DOS PCs, allocating a mix of extended memory
and EMS memory is often requried.  Windows 3.x and
DOS-extended applications use extended memory,
while other applications may use EMS memory.  On
286s, allocation requires changing parameters in
the CONFIG.SYS file and rebooting.  Older 286s may
require changing switches on the EMS boards.  On
386s and up, using advanced memory managers such as
QEMM386, 386MAX and the EMM386 that comes with DOS
6 and up, allocation can be done on demand
automatically.  See DOS memory manager.



memory bank
(1) A physical section of memory.  See memory
interleaving.

(2) Refers generically to a computer system that
holds data.



memory based
Programs that hold all data in memory for
processing.  Almost all spreadsheets are memory
based so that a change in data at one end of the
spreadsheet can be instantly reflected at the other
end.



memory cache
See cache.



memory card
A credit-card-sized memory module used as an
additional disk or disk alternative in laptops and
palmtops.  Called IC cards, ROM cards and RAM
cards, they use a variety of chip types, including
RAM, ROM, EEPROM and flash memory.  RAM cards used
in this manner contain a battery to keep the cells
charged.

   Note that when you add more memory in a laptop,
the plug-in cards may also be called memory cards
or RAM cards, but these are not substitutes for
disk.  They extend the computer's normal RAM memory
and are typically contained on proprietary plug-in
cards or modules.  The memory card that functions
as a disk typically uses the PCMCIA architecture
and requires special software that accompanies the
computer.  See solid state disk and flash memory.



memory cell
One bit of memory.  In dynamic RAM memory, a cell
is made up of one transistor and one capacitor.  In
static RAM memory, a cell is made up of about five
transistors.



memory chip
A chip that holds programs and data either
temporarily (RAM), permanently (ROM, PROM) or
permanently until changed (EPROM, EEPROM).



memory cycle
A series of operations that take place to read or
write a byte of memory.  For destructive memories,
it includes the regeneration of the bits.



memory cycle time
The time it takes to perform one memory cycle.



memory dump
A display or printout of the contents of memory.
When a program abends, a memory dump can be taken
in order to examine the status of the program at
the time of the crash.  The programmer looks into
the buffers to see which data items were being
worked on when it failed.  Counters, variables,
switches and flags are also inspected.



memory effect
See nickel cadmium and nickel hydride.



memory interleaving
A category of techniques for increasing memory
speed.  For example, with separate memory banks for
odd and even addresses, the next byte of memory can
be accessed while the current byte is being
refreshed.



memory management
Refers to a variety of methods used to store data
and programs in memory, keep track of them and
reclaim the memory space when they are no longer
needed.  In traditional minicomputers and
mainframes, it comprises virtual memory, bank
switching and memory protection techniques.  See
virtual memory, memory protection and garbage
collection.

   Memory management has become a major issue with
PCs, because the PC has more different types of
memory regions than any computer in history.  In a
PC, it refers to managing conventional memory, the
upper memory area (UMA), the high memory area
(HMA), extended memory and expanded memory.

   By reserving fixed areas in upper memory (UMA)
for use by the operating system, expanding the PC
has been a memory management nightmare.  Countless
books have been written on a problem that never
should have existed in the first place.  There are
even two-day courses on the subject.  See EMS, EMM
and DOS memory manager.



memory manager
Software that manages memory in a computer.  See
memory management.



memory map
The location of instructions and data in memory.



memory mapped I/O
A peripheral device that assigns specific memory
locations to input and output.  For example, in a
memory mapped display, each pixel or text character
derives its data from a specific memory byte or
bytes.  The instant this memory is updated by
software, the screen is displaying the new data.



memory protection
A technique that prohibits one program from
accidentally clobbering another active program.
Using various different techniques, a protective
boundary is created around the program, and
instructions within the program are prohibited from
referencing data outside of that boundary.



memory resident
A program that remains in memory at all times.  See
TSR.



memory sniffing
Coined by Data General, a diagnostic routine that
tests memory during normal processing.  The
processor uses cycle stealing techniques that allow
it to test memory during unused machine cycles.  A
memory bank can be "sniffed" every few minutes.



memory typewriter
A typewriter that holds a few pages of text in its
memory and provides limited word processing
functions.  With a display screen of only one or
two lines, editing is tedious.



menu
An on-screen list of available functions, or
operations, that can be performed currently.
Depending on the type of menu, selection is
accomplished by (1) highlighting the menu option
with a mouse and releasing the mouse, (2) pointing
to the option name with the mouse and clicking on
it, (3) highlighting the option with the cursor
keys and pressing Enter, or (4) pressing the first
letter of the option name or some designated letter
within the name.  See Lotus menu and pull-down
menu.



menu bar
A row of on-screen menu options.



menu-driven
Using menus to command the computer.  Contrast with
command-driven.



menuing software
Software that provides a menu for launching
applications and running operating system commands.



merge
See mail merge and concatenate.



merge purge
To merge two or more lists together and eliminate
unwanted items.  For example, a new name and
address list can be added to an old list while
deleting duplicate names or names that meet certain
criteria.



mesa
A semiconductor process used in the 1960s for
creating the sublayers in a transistor.  Its deep
etching gave way to the planar process.



mesh network
A net-like communications network in which there
are at least two pathways to each node.  Since the
term network means net-like as well as
communications network, the term mesh is used to
avoid saying network communications network.



message
(1) In communications, a set of data that is
transmitted over a communications line.  Just as a
program becomes a job when it's running in the
computer, data becomes a message when it's
transmitted over a network.

(2) In object-oriented programming, communicating
between objects, similar to a function call in
traditional programming.



message based
An interface that is based on a set of commands.  A
message-based system is a type of client/server
relationship, in which requests are made by a
client component, and the results are provided by a
server component.  It implies greater flexibility
and interoperability in contrast with a hard coded
operation, which would have to be modified by
reprogramming the source code.



message handling
(1) An electronic mail system.  See messaging
system.

(2) In communications, the lower level protocols
that transfer data over a network, which assemble
and disassemble the data into the appropriate codes
for transmission.



Message Handling Service
See MHS.



message handling system
Same as messaging system.



message queue
A storage space in memory or on disk that holds
incoming transmissions until the computer can
process them.



message switch
A computer system used to switch data between
various points.  Computers have always been ideal
switches due to their input/output and compare
capabilities.  It inputs the data, compares its
destination with a set of stored destinations and
routes it accordingly.  Note: A message switch is a
generic term for a data routing device, but a
messaging switch converts mail and messaging
protocols.



message transfer agent
The store and forward capability in a messaging
system.  See messaging system.



MessagePad
The first PDA from Apple to use the Newton
technology.  Introduced in the summer of 1993, it
is a hand-held personal organizer that recognizes
hand printing.  It can add an appointment to a
calendar and dial a phone or send a fax.



messaging API
A programming interface that enables an application
to send and receive messages and attached files
over a messaging system.  VIM, MAPI and CMC are
examples.  Novell's SMF-71, although also called an
API, is actually the message format that mail must
be placed into for submission to Novell's MHS.
There are no functions associated with it.



messaging gateway
A computer system that converts one messaging
protocol to another.  It provides an interface
between two store and forward nodes, or message
transfer agents (MTAs).



messaging protocol
The rules, formats and functions for exchanging
messages between the components of a messaging
system.  The major industry messaging protocols are
the international X.400, SMTP (Internet), IBM's
SNADS and Novell's MHS.  Widely-used messaging
products such as cc:Mail and Microsoft Mail use
proprietary messaging protocols.



messaging switch
A messaging hub that provides protocol conversion
between several messaging systems.  Examples of
switches include Soft-Switch's EMX, HP's OpenMail
and Digital's MAILbus.  A messaging switch differs
from a messaging gateway in that it supports more
than two protocols and connections as well as
providing management and directory integration.



messaging system
Software that provides an electronic mail delivery
system.  It is comprised of three functional areas,
which are either packaged together or are
modularized as independent components.  (1) The
user agent, or UA, submits and receives the
message.  (2) The message transfer agent, or MTA,
stores and forwards the message.  (3) The message
store, or MS, holds the mail and allows it to be
selectively retrieved and deleted.  It also
provides a list of its contents.

   Messaging products such as cc:Mail, Microsoft
Mail, PROFS, DISOSS and ALL-IN-1 implement the
entire messaging system.  Other products must use
components of other systems; for example, DaVinci
Mail uses Novell's MHS.



metadata
Data that describes other data.  See data
dictionary and repository.



metafile
A file that contains other files.  It generally
refers to graphics files that can hold vector
drawings and bitmaps.  For example, a Windows
Metafile (WMF) can store pictures in vector
graphics and raster graphics formats as well as
text.  A Computer Graphics Metafile (CGM) also
stores both types of graphics.



metal oxide semiconductor
See MOS.



metal oxide varistor
See MOV.



metalanguage
A language used to describe another language.



metamail
A public-domain UNIX utility that composes and
decomposes a MIME message on the Internet.



metaphor
The derivation of metaphor means "to carry over."
Thus the "desktop metaphor" as so often described
means that the office desktop has been brought over
and simulated on computers.



meter
The basic unit of the metric system (39.37 inches).
A yard is about 9/10ths of a meter (0.9144 meter).



method
In object-oriented programming, a method is the
processing that an object performs.  When a message
is sent to an object, the method is implemented.



methodology
The specific way of performing an operation that
implies precise deliverables at the end of each
stage.



metric
Measurement.  Although metric generally refers to
the decimal-based metric system of weights and
measures, software engineers often use the term as
simply "measurement."  For example, "is there a
metric for this process?"  See software metrics.



metropolitan area network
See MAN.



MFC
See Microsoft C and Visual C++.



Mflops
See megaflops.



MFM
(Modified Frequency Modulation)  A magnetic disk
encoding method used on most floppy disks and most
hard disks under 40MB.  It has twice the capacity
of the earlier FM method, transfers data at 625
Kbytes per second and uses the ST506 interface.
See hard disk.



MGA
(Monochrome Graphics Adapter)  A display adapter
that employs Hercules Graphics, combining graphics
and text on a monochrome monitor.



MGP
(Monochrome Graphics Printer port)  A display
adapter that employs Hercules Graphics and a
parallel printer port on the same expansion board.



MHS
(1) (Message Handling Service)  A messaging system
from Novell that supports multiple operating
systems and other messaging protocols.  Optional
modules support SMTP, SNADS and X.400.  It uses the
SMF-71 messaging format.  Standard MHS runs on a
DOS machine attached to the server.  Global MHS
runs as a NetWare NLM.  Under NetWare, MHS runs on
top of IPX.

(2) See messaging system.



MHz
(MegaHertZ)  One million cycles per second.  It is
used to measure the transmission speed of
electronic devices, including channels, buses and
the computer's internal clock.  Megahertz is
generally equivalent to one million bits per second
or to one million times some number of bits per
second.

   When it refers to the computer's clock, it is
used to measure the speed of the CPU.  For example,
a 50MHz 486 computer processes data internally
(calculates, compares, copies) twice as fast as a
25MHz 486.  However, this does mean twice as much
finished work in the same time frame, because cache
design, disk speed and software design all
contribute to the computer's actual performance, or
throughput.  See MIPS.


               MHz Is the Heartbeat
When referencing CPU speed, the megahertz rating is
really the heartbeat of the computer, providing the
raw, steady pulses that energize the circuits.  If
you know a little of the German language, it's easy
to remember this.  The word "Herz," pronounced
"hayrtz," means heart.



MIB
(Management Information Base)  An SNMP structure
that describes the particular device being
monitored.  See SNMP.



mickey
A unit of mouse movement typically set at 1/200th
of an inch.



MICR
(Magnetic Ink Character Recognition)  The machine
recognition of magnetically-charged characters
typically found on bank checks and deposit slips.
MICR readers detect the characters and convert them
into digital data.



micro
(1) A microcomputer or personal computer.

(2) One millionth or 10 to the -6th power.  See
space/time.

(3) Microscopic or tiny.



Micro Channel
Also known as MCA (Micro Channel Architecture), it
is an IBM 32-bit bus used in most PS/2s, the
RS/6000 series and certain ES/9370 models.  MCA
boards are not interchangeable with ISA and EISA
boards.

   Micro Channel provides auto configuration, which
means that a unique identification is built into
each expansion board, allowing it to be configured
by software rather than by setting jumpers or DIP
switches on the board itself.  This system
identifies conflicts ahead of time and assists
users in configuring their systems when a new
peripheral is added.

   Micro Channel transfers data at 20MBytes/sec and
has modes for increasing speeds to 40 and 80MB.  It
also has specifications for 64 bits and 160MB
transfer.  Micro Channel supports up to 15 levels
of bus mastering.



Micro Focus
(Micro Focus Inc., Palo Alto, CA)  A software
company founded in 1976 that specializes in COBOL
application development for a variety of platforms.
It is known for its COBOL Workbench programming
tools.  Micro Focus products are used to develop
applications on personal computers and workstations
that are intended for execution on mainframes, as
well as to move COBOL, CICS and IMS applications
from the mainframe to client/server environments.



micro manager
A person who manages personal computer operations
within an organization and is responsible for the
analysis, selection, installation, training and
maintenance of personal computer hardware and
software.  See information center and MMA.



Micro PDP-11
The microcomputer version of the PDP-11 from
Digital introduced in 1975.  Uses the Q-bus and
serves as a stand-alone computer or is built into
other equipment.



micro to mainframe
An interconnection of personal computers to
mainframes.  See 3270 emulator.



microchip
Same as chip.



microchip module
See MCM.



microcircuit
A miniaturized, electronic circuit, such as is
found on an integrated circuit.  See chip and MCM.



microcode
A permanent memory that holds the elementary
circuit operations a computer must perform for each
instruction in its instruction set.  It acts as a
translation layer between the instruction and the
electronic level of the computer and enables the
computer architect to more easily add new types of
machine instructions without having to design
electronic circuits.  Microcode is used in CISC
architecture.  See microprogramming.



Microcom Protocol
See MNP.



microcomputer
Same as personal computer.



Microcomputer Industry Association
See CompTIA.



Microcomputer Manager's Association
See MMA.



microcontroller
See MCU.



microelectronics
The miniaturization of electronic circuits.  See
chip.



microfiche
Pronounced "micro-feesh."  A 4x6" sheet of film
that holds several hundred miniaturized document
pages.  See micrographics.



microfilm
A continuous film strip that holds several thousand
miniaturized document pages.  See micrographics.



microfloppy disk
A floppy disk encased in a 3.5" wide, rigid plastic
shell.  Developed by Sony, it has become the medium
of choice as it holds more data and is easier to
handle than its 5.25" counterpart.



microform
In micrographics, a medium that contains
microminiaturized images such as microfiche and
microfilm.



micrographics
The production, handling and use of microfilm and
microfiche.  Images are created by cameras or by
COM units that accept computer output directly.
The documents are magnified for human viewing by
readers, some of which can automatically locate a
page using indexing techniques.

   Microfiche and microfilm have always been an
economical alternative for high-volume data and
picture storage.  However, optical disks are
competing with film-based systems and may become
the preferred storage medium.



microimage
In micrographics, any photographic image of
information that is too small to be read without
magnification.



microinstruction
A microcode instruction.  It is the most elementary
computer operation that can take place; for
example, moving a bit from one register to another.
It takes several microinstructions to carry out one
machine instruction.



microjacket
In micrographics, two sheets of transparent plastic
that are bonded together to create channels into
which strips of microfilm are inserted and stored.



microkernel
The hardware-dependent component of an operating
system that is designed to be more easily portable
to multiple platforms.  The rest of the operating
system interacts with the microkernel in a message-
based relationship and does not have to be
rewritten.  Only the microkernel has to be
reprogrammed to the architecture of the new
hardware.  See kernel.



microlithography
Using x rays instead of light rays to form the
patterns of elements on a chip.  This technology is
expected to emerge by the 21st century.  AT&T Bell
Labs has speculated that by the year 2001, a
dynamic RAM chip with one billion bits (1 gigabit)
will be built using .18 micron microlithography.
By contrast, a 486 chip is built with 1.0 micron
technology (the lines are 1.0 micron wide).



micromainframe
A personal computer with mainframe or near
mainframe speed.



micromechanics
The microminiaturization of mechanical devices
(gears, motors, rotors, etc.) using similar
photomasking techniques as in chip making.



micromini
A personal computer with minicomputer or near
minicomputer speed.



micron
One millionth of a meter.  Approximately 1/25,000
of an inch.  The tiny elements that make up a
transistor on a chip are measured in microns.  For
example, the 486 uses 1.0 micron technology, the
Pentium .8 micron.  Digital is expected to produce
its Alpha chip with .035 micron technology in 1995.



microprocessor
A CPU on a single chip.  In order to function as a
computer, it requires a power supply, clock and
memory.  First-generation microprocessors were
Intel's 8080, Zilog's Z80, Motorola's 6800 and
Rockwell's 6502.  The first microprocessor was
created by Intel.



microprogram
Same as microcode.



microprogramming
Programming microcode.



micropublishing
In micrographics, the issuing of new or reformatted
information on microfilm for sale or distribution.



microrepublishing
In micrographics, the issuing of microfilm that has
been previously or is simultaneously published in
hardcopy for sale or distribution.



microsecond
One millionth of a second.  See space/time.



Microsoft
(Microsoft Corporation, Redmond, WA)  The world's
most influential software company.  Microsoft was
founded in 1975 by Paul Allen and Bill Gates, two
college students who wrote the first BASIC
interpreter for the Intel 8080 microprocessor
(Allen now runs Asymetrix Corporation).

   MBASIC was licensed to Micro Instrumentation and
Telemetry Systems to accompany its Altair 8800 kit.
By the end of 1976, more than 10,000 Altairs were
sold with MBASIC.  Versions were licensed to Radio
Shack, Apple and many other vendors.  Later, a
version called GW-BASIC (Gee Whiz BASIC) was
developed for 16-bit personal computers.

   Although Microsoft became a leader in
microcomputer programming languages, its
outstanding success is due to supplying IBM with
DOS and the compatible companies with MS-DOS.  It
continues this success with Windows since Version
3.0 was introduced in 1990.  Windows is the de
facto standard environment for desktop computers.

   Microsoft is also extremely successful in the
applications market with products such as Excel,
Word for Windows and Access.  However, Microsoft's
position as the supplier of the major operating
systems to the world's largest computer base gives
it considerable advantage and power.



Microsoft Access
A database program for Windows from Microsoft that
directly reads Paradox, dBASE and Btrieve files.
Using ODBC, it directly reads Microsoft and SYBASE
SQL Server and Oracle data.  Access BASIC is its
programming language, and "Wizards" ask you
questions to create forms, reports and graphs.



Microsoft BackOffice
See BackOffice.



Microsoft C
A C compiler and development system for DOS and
Windows applications from Microsoft.  Windows
programming requires the Windows Software
Development Kit (SDK), which is included.

   Version 7.0 includes C++ capability and Version
1.0 of the Microsoft Foundation Class Library
(MFC), which provide a base framework of object-
oriented code to build an application upon.  See
Visual C++.



Microsoft Certified Professional
A training program that provides certification of
competency in Microsoft products.  Administered
throughout the world at Microsoft centers as well
as colleges and universities, it provides the
following certification levels.  The Certified
Product Specialist (CPS) is for the user and
reseller who supports Windows-based PCs.  The
Certified Systems Engineer (CSE) is for the
technical specialist involved with Windows NT and
other advanced Microsoft products.  The Certified
Trainer (CT) is for people that will train others.
For more information about the program, call
800/426-9400.



Microsoft Mail
A messaging system from Microsoft that runs on PC
and AppleTalk networks.  Gateways are available to
a variety of mail systems including X.400, PROFS,
Novell's MHS and MCI Mail.  Microsoft Mail-enabled
applications are written to the MAPI programming
interface.



Microsoft Office
A suite of Windows applications from Microsoft that
include Mail, Access, PowerPoint, Word and Excel.
The applications have been designed for tighter
integration with sharing of common functions such
as spell checking and graphing.  Objects can be
dragged and dropped between applications.  It
includes MOM, the Microsoft Office Manager, a
toolbar utility that launches the applications.



Microsoft SQL Server
See SQL Server.



Microsoft Word
A full-featured word processing programs for DOS,
Windows and Mac from Microsoft.  The Windows
version, Word for Windows, or WinWord, is a
sophisticated program with rudimentary desktop
publishing capabilities.  Word for Windows is very
popular and has increasingly gained market share.
The earlier DOS version provides both graphics-
based and text-based interfaces for working with a
document.



Microsoft Works
An integrated software package for PCs and the
Macintosh from Microsoft.  It provides file
management with relational-like capabilities, word
processing, spreadsheet, business graphics and
communications capabilities in one package.



microspacing
Positioning characters for printing by making very
small horizontal and vertical movements.  Many dot
matrix printers and all laser printers have this
ability.



MicroStation
A full-featured 2-D and 3-D CADD program from
Intergraph Corporation, Huntsville, AL, for PCs,
Macs and Intergraph, Sun and HP workstations.



MicroVAX
A series of entry-level VAXs introduced in 1983
that run under VMS or ULTRIX.  Some models use the
Q-bus architecture.



microwave
An electromagnetic wave that vibrates at 1GHz and
above.  Microwaves are the transmission frequencies
used in communications satellites as well as in
line-of-sight systems on earth.



MID file
See MIDI file.



middleware
Software that functions as a conversion or
translation layer.  The term is used to describe a
diverse group of products.  It may refer to
software that sits between an application and a
control program (operating system, network control
program, DBMS, etc.) that provides a single
programming interface for the applications to be
written to.  The application will run in as many
different computer environments as the middleware
runs in.

   TP monitors are called middleware, because they
reside between the client applications and the
servers.  Information Builder's EDA/SQL is called
middleware, because it translates various query
languages to different database programs.
Microsoft's ODBC interface is also called
middleware, because it provides a common API to
many different databases.



MIDI
(Musical Instrument Digital Interface)  A standard
protocol for the interchange of musical information
between musical instruments, synthesizers and
computers.  It defines the codes for a musical
event, which includes the start of a note, its
pitch, length, volume and musical attributes, such
as vibrato.  It also defines codes for various
button, dial and pedal adjustments used on
synthesizers.

   MIDI is commonly used to synchronize notes
produced on several synthesizers.  Its control
messages can orchestrate a series of synthesizers,
each playing a part of the musical score.

   A computer with a MIDI interface can be used to
record a musical session, but instead of recording
the analog sound waves as in a tape recorder, the
computer stores the music as keystroke and control
codes.  The recording can be edited in an entirely
different manner than with conventional recording;
for example, the rhythm can be changed by editing
the timing codes in the MIDI messages.  In
addition, the computer can easily transpose a
performance from B major into D major.  MIDI files
also take up much less disk space than sound files
that contain the actual digitized music.

   The objective of MIDI was to allow the keyboard
of one synthesizer to play notes generated by
another.  However, since Version 1.0 in 1983, MIDI
has brought electronic control of music to
virtually everybody, benefiting musicians and
teachers alike.

   MIDI makes an ideal system for storing music on
digital media due to its small storage requirement
compared with digitizing actual music.  Since the
advent of General MIDI, a standard for defining
MIDI instruments, MIDI will become more widely used
for musical backgrounds in multimedia applications.

   See General MIDI, MIDI sequencer, MIDI patch,
MIDI voices, MPU-401, wave table synthesis, FM
synthesis and sound card.



MIDI file
A MIDI sound file that contains MIDI messages.
MIDI files used in DOS and Windows have a .MID
extension.  A variation of this format is the RIFF
MIDI file, which uses the .RMI extension.

   The format for MIDI files, or Standard MIDI File
(SMF), contains a header "chunk" at the beginning
of the file, which defines the format type,
followed by one or more track chunks.  Type 0 files
store all tracks in one track chunk.  Type 1 files
use a separate chunk for each track, with the first
chunk storing the tempo.

   Type 0 files use less memory and run faster than
type 1.  Thus, original MIDI music is maintained in
type 1 format and frequently distributed in type 0.
MIDI files distributed for editing are usually in
type 1 format, since it is difficult to convert
from type 0 to type 1 using a MIDI sequencer.

   A less-widely used type 2 file can contain
several type 0 files.



MIDI Mapper
A Windows application that converts MIDI sound
sequences (MIDI messages) to conform to a
particular MIDI sound card or module.  The keyboard
map is used to assign values to non-standard
keyboard keys.  The patch map assigns sounds to an
instrument number (see MIDI patch).  The channel
map assigns input channels to output channels.



MIDI messages
A series of MIDI notes for a musical sequence.
Since MIDI data is a set of musical note
definitions rather than the actual sound of the
music, the contents of a MIDI file are called MIDI
messages.



MIDI patch
One of 16 channels in a MIDI device.  Many keyboard
synthesizers and MIDI sound modules can handle
several waveforms per patch, mixing different
instruments together to create synthetic sounds.
Each waveform counts as a MIDI voice.  Some sound
cards can support two or more waveforms per patch.

   Before General MIDI, which standardized patches,
MIDI vendors assigned patch numbers to their
synthesizer products in an arbitrary manner.  See
MIDI voices.



MIDI sequencer
A hardware device or software application that
allows for the composition, editing and playback of
MIDI sound sequences.  Media player applications
can play MIDI sound files, but creating and
modifying MIDI files requires a sequencer.



MIDI sound module
A stand-alone device that generates MIDI sound.
Other MIDI sound-generating devices are
synthesizers with keyboards and sound cards for
personal computers.



MIDI voices
The number of musical notes that can be played back
simultaneously in a MIDI sound device.  MIDI
provides up to 16 channels of simultaneous
playback.  The number of voices is the total number
of notes from all the instruments played back
through all the channels.

   For example, if one of the channels (patches) is
a piano, up to 10 fingers could strike the keyboard
at the same time, generating 10 notes, assuming
that particular piano patch triggers only one
waveform (see MIDI patch).  Typically, a MIDI sound
card will support from 24 to 32 voices.  Keyboard
synthesizers and sound modules can handle up to 64.



midicomputer
A computer with performance and capacity between a
minicomputer and a mainframe.



midrange computer
Same as minicomputer, but excludes single-user
minicomputer workstations.  For example, an IBM
AS/400 would be typically called a midrange
computer, but a Sun SPARCstation would not.



MIF
(1) (Maker Interchange Format)  An alternate file
format for a FrameMaker document.  A MIF file is
ASCII text, which can be created in another program
and imported into FrameMaker.

(2) (Managment Information File)  A DMI file format
that describes a hardware or software component
used in a PC.  It can contain data, code or both.
See DMI.



mill
A very old term for processor (number crunching!).



milli
One thousandth or 10 to the -3rd power.



millimeter
One thousandth of a meter, or 1/25th of an inch.



million
One thousand times one thousand or 10 to the 6th
power.  See mega and microsecond.



millisecond
One thousandth of a second.  See space/time.



MIMD
(Multiple Instruction stream Multiple Data stream)
A computer architecture that uses multiple
processors, each processing its own set of
instructions simultaneously and independently of
the others.  Contrast with SIMD.



MIME
(Multipurpose Internet Mail Extensions)  Extensions
to the SMTP format that allow it to carry multiple
types of data (binary, audio, video, etc.).



mini
See minicomputer.



mini-supercomputer
A computer that is 25% to 100% as fast as a
supercomputer, but costs less.  Note: A mini-
supercomputer is not the same as a supermini.



minicartridge
See QIC.



minicomputer
A medium-scale computer that functions as a single
workstation, or as a multiuser system with up to
several hundred terminals.  A minicomputer system
costs roughly from $20,000 to $250,000.

   In 1959, Digital launched the minicomputer
industry with its PDP-1.  Soon after, Data General
and HP introduced minis, and eventually Wang,
Tandem, Datapoint and Prime joined them.  IBM has
introduced several minicomputer series (see IBM
minicomputers).

   Today, the term "midrange" has become popular
for medium-sized computer.  High-end microcomputers
and low-end mainframes overlap in minicomputer
price and performance.



MiniDisc
An optical disk drive from Sony that uses a 2.5"
platter that holds 140MB.  Used as a removable disk
drive in portable machines, or potentially, as a
floppy disk replacement, the drive handles three
types of disks.  An MD-ROM is read-only like a CD-
ROM.  An MD-Data disk is rewritable, and a
combination disk allows for permanent and updatable
information.



minifloppy
The formal name for the ubiquitous floppy disk that
is encased in a 5.25" wide, stiff plastic jacket.
Introduced by Shugart in 1978, it superseded IBM's
8" floppy.  Although used extensively, the
minifloppy is finally giving way to the 3.5" format
(microfloppy disk).



minimize
In graphical environments, to reduce a window to an
icon.



MINIX
A version of UNIX for the PC, Mac, Amiga and Atari
ST developed by Andrew Tannenbaum and published by
Prentice-Hall.  It comes with complete source code.



minor key
A secondary key used to identify a record.  For
example, if transactions are sorted by account
number and date, account number is the major key
and date is the minor key.



MIPS
(Million Instructions Per Second)  The execution
speed of a computer.  For example, .5 MIPS is
500,000 instructions per second.  High-speed
personal computers and workstations perform at 100
MIPS and higher.  Digital's Alpha chip has a peak
rate of over 1,200 MIPS (that's 1.2 BIPS!).
Inexpensive microprocessors used in toys and games
may be in the .05-.1 MIPS range.

   MIPS rates are not uniform.  Some are best-case
mixes while others are averages.  In addition, it
takes more instructions in one machine to do the
same thing as another (RISC vs CISC, mainframe vs
micro).  As a result, MIPS has been called
"MisInformation to Promote Sales" as well as
"Meaningless Interpretation of Processor Speed."

   MIPS rate is just one factor in overall
performance.  Bus and channel speed and bandwidth,
memory speed, memory management techniques and
system software also determine total throughput.
See also MIPS Computer.


                     MIPS and MHz
There is a mathematical relationship between MIPS
and MHz.  You can derive MIPS from MHz if you know
how many machine cycles it takes to execute an
instruction in the CPU.  For example, a 486 takes
1.9 cycles on average.  To obtain MIPS on a 50MHz
486, you would divide 50 by 1.9, yielding 26 MIPS.



MIPS Computer
(MIPS Computer Systems, Inc., Sunnyvale, CA.)  A
microcomputer and minicomputer manufacturer that
was acquired by Silicon Graphics (SGI).  MIPS RISC-
based R3000 and R4000 families of 32- and 64-bit
microprocessors are widely used in the industry.
They are designed by MIPS and made under license by
NEC and other companies.  Silicon Graphics
workstations are powered by MIPS chips as well as
computer systems from companies such as Pyramid,
Tandem, NEC and Siemens/Nixdorf.



Mirror II
A PC communications program from Softklone
Distributing Corporation, Tallahassee, FL, that
supports a variety of terminals and protocols and
provides a learn mode for recording common
sequences.



mirroring
See disk mirroring.



Mirrors
Software from Micrografx, Inc., Richardson, TX,
that allows Windows programs to be converted to
OS/2 with minimal modification.



MIS
(1) (Management Information System)  An information
system that integrates data from all the
departments it serves and provides operations and
management with the information they require.

   It was "the" buzzword of the mid to late 1970s,
when online systems were implemented in all large
organizations.  See DSS.

(2) (Management Information Services)  See
Information Systems.



mission critical
Vital to the operation of an organization.  In the
past, mission critical information systems were
implemented on mainframes and minicomputers.
Increasingly, they are being designed for and
installed on personal computer networks.  See
client/server.



mixed object
Same as compound document.



MKS
(Mortice Kern Systems Inc., Waterloo, Ontario)  A
software company that specializes in programming
tools and utilities for a variety of platforms.
For example, its RCS system for Windows, OS/2 and
UNIX is a version control software package.



ML
A symbolic programming language developed in the
1970s at the University of Edinburgh, Scotland.
Although similar to LISP, its commands and
structures are like Pascal.



MM
(1) See Multiple Master.

(2) (mm) (MilliMeter)  One thousandth of a meter.



MMA
(Microcomputer Manager's Association, Inc.)  A
membership organization with chapters throughout
the U.S. devoted to educating personnel responsible
for personal computers.  Provides seminars,
conferences, trade show events, job bank and
newsletters.  Address: P.O.Box 4615, Warren, NJ,
908/580-9091.



MME
See Multimedia Extensions.



MMF
See multimode fiber.



MMI
(Man Machine Interface)  Same as user interface.



MMU
(Memory Management Unit)  A virtual memory circuit
that translates logical addresses into physical
addresses.



mnemonic
Pronounced "nuh-monic."  Means memory aid.  A name
assigned to a machine function.  For example, in
DOS, COM1 is the mnemonic assigned to serial port
#1.  Programming languages are almost entirely
mnemonics.



MNP
(Microcom Networking Protocol)  A family of
communications protocols from Microcom, Inc.,
Norwood, MA, that have become de facto standards
for error correction (classes 2 though 4) and data
compression (class 5).

Class    Features

  1  Half-duplex asynchronous transmission.
     (Early mode, no longer used.)

  2  Full-duplex asynchronous transmission.

  3  Full-duplex synchronous transmission using
     HDLC framing techniques using 64-byte
     blocks.  Start/stop bits stripped.

  4  Increased throughput.  Shorter headers,
     frames up to 256 bytes.  Some vendors
     adjust frame size based on line quality.

  5  Compresses data up to two times.

  6  Starts at V.22bis modulation and switches
     to V.29 if possible.  Uses pseudo-
     duplexing ping-pong method for faster
     turnaround of V.29 transmission.

  7  Compresses data up to three times.

  8  Not in use.

  9  Adds Piggy-back Acknowledgement** and
     selective retransmission for more
     efficient transport of data.  Provides
     better performance over variety of links.

 10  Adds Adverse Channel Enhancements** for
     efficient operation on noisy lines (rural,
     cellular, international, etc.).

** Proprietary Microcom techniques.





MO
See magneto-optic.



MO:DCA
(Mixed Object:Document Content Architecure)  An IBM
compound document format for text and graphics
elements in a document.  It supports Revisable
Documents, which are editable like revisable-form
DCA, Presentation Documents, which provide specific
output formatting similar to DCA final-form, and
Resource Documents, which hold control information
such as fonts.

   Formats for specific objects are specified in
OCAs (Object Content Architectures): PTOCA for
Presentation and Text that has been formatted for
output, GOCA for vector Graphics objects, IOCA for
bitmapped Images and FOCA for Fonts.



Mobitex
A packet radio service from RAM Mobile Data (joint
venture of RAM Broadcasting and BellSouth).  Base
stations serve major cities throughout the U.S.



mod
See modulo.



modal
Mode oriented.  A modal operation switches from one
mode to another.  Contrast with non-modal.



modal bandwidth
The capacity of an optical fiber measured in MHz-km
(megahertz over one kilometer).  One MHz-km equals
approximately .7 to .8 Mbps.  Thus, a 100 MHz-km
fiber can carry about 70 to 80 Mbps of data.



modal dispersion
A signal distortion in an optical fiber in which
the light pulses spread out, and the receiving
device cannot detect the beginnings and ends of
pulses.



mode
An operational state that a system has been
switched to.  It implies at least two possible
conditions.  There are countless modes for hardware
and software.  See Real Mode, Protected Mode, burst
mode, insert mode, supervisor state and program
state.



model
(1) A style or type of hardware device.

(2) A mathematical representation of a device or
process used for analysis and planning.  See data
model, data administration, financial planning
system and scientific applications.



model-based expert system
An expert system based on fundamental knowledge of
the design and function of an object.  Such systems
are used to diagnose equipment problems, for
example.  Contrast with rule-based expert system.



modeling
Simulating a condition or activity by performing a
set of equations on a set of data.  See data
modeling, data administration, financial planning
system and scientific applications.



modem
(MOdulator-DEModulator)  A device that adapts a
terminal or computer to a telephone line.  It
converts the computer's digital pulses into audio
frequencies (analog) for the telephone system and
converts the frequencies back into pulses at the
receiving side.  The modem also dials the line,
answers the call and controls transmission speed,
which ranges from 300 to 14,400 bps and higher.

   Other kinds of modems are made for a variety of
modulation requirements; for example, broadband
modems connect lines to high-speed broadband
channels.

   For hookup to a personal computer, an internal
modem needs a free expansion slot, while an
external modem in its own case requires a free
serial port.  A communications program drives the
modem.  It turns the personal computer into an
interactive terminal and file transfer program that
controls the modem and transmission.  The term
modem is also used as a verb; for example, "I'll
modem you later."  See communications program.

   The recent migration from 2,400 bps modems to
9,600 and 14,400 bps makes it simpler to transfer
large files.  The number of characters transmitted
is about 10% of the bit rate; thus, 9,600 bps is
equivalent to sending 960 bytes of text in one
second.  At 9,600 bps, it takes a little more than
two seconds to display a full screen of text, but
considerably more for graphics.  Remote control
software, which lets you take complete control of
another machine via modem, constantly refreshes the
remote screen with changes and requires the fastest
modem.

   New modems have built-in error correction (V.42)
and data compression (V.42bis, MNP 5), which means
faster transmission if both sides have the same
capability.  They also have automatic feature
negotiation, which adjusts to the other modem's
speed and hardware protocols.

   Most personal computer modems use the Hayes AT
command set, which is the series of machine
instructions that control the modem.  See AT
command set and Hayes Smartmodem.


               Modem Status Signals
The following acronyms are used with the display
lights on the modem to identify the unit's current
status:

              AA  Auto answer mode
              CA  Compression active
              CD  Carrier detect
             CTR  Clear to send
       DTR or TR  Terminal ready
              EC  Error control active
              HS  High speed
              LB  Low battery
              MR  Modem ready
              OH  Off hook
             PWR  Power on
       RNG or RI  Ringing
             RTS  Request to send
       RXD or RD  Receiving data
              TM  Test mode
   TXD, TD or SD  Transmitting (send) data





modem eliminator
A device that allows two close computers to be
connected without modems.  For personal computers,
it is the same as a null modem cable.  In
synchronous systems, it provides active
intelligence for synchronization.



modem lights
See "Modem Status Signals" under modem.



modem server
See communications server.



modify structure
A database command that changes a file's structure.
Field lengths and field names can be changed, and
fields can be added or deleted.  It may convert the
old data file into the new structure without data
loss, unless fields have been truncated or deleted.



Modula-2
(MODUlar LAnguage-2)  An enhanced version of Pascal
introduced in 1979 by Swiss professor Nicklaus
Wirth, creator of Pascal.  It supports separate
compilation of modules.  The following example
changes Fahrenheit to Celsius:

      MODULE FahrToCent;
   FROM InOut IMPORT ReadReal,WriteReal,
   WriteString,WriteLn;
   VAR Fahr:REAL;
   BEGIN
   WriteString("Enter Fahrenheit ");
   ReadReal(Fahr);
   WriteLn;
   WriteString("Celsius is ");
   WriteReal((Fahr - 32) * 5 / 9);
      END  FahrToCent





modular programming
Breaking down the design of a program into
individual components (modules) that can be
programmed and tested independently.  It is a
requirement for effective development and
maintenance of large programs and projects.



Modular Windows
A subset of Windows for TV-based consumer
electronics.  It does not use Program Manager,
scroll bars and overlapping windows.  The
application is the window.



modulate
To vary a carrier wave.  Modulation blends a data
signal (text, voice, etc.) into a carrier for
transmission over a network.  Major methods are AM
(amplitude modulation) - modulate the height of the
carrier wave, FM (frequency modulation) - modulate
the frequency of the wave, and PM (phase
modulation) - modulate the polarity of the wave.
Contrast with demodulate.  See carrier.



module
A self-contained hardware or software component
that interacts with a larger system.  Hardware
modules are often made to plug into a main system.
Program modules are designed to handle a specific
task within a larger program.



modulo
A mathematical operation (modulus arithmetic) in
which the result is the remainder of the division.
For example, 20 MOD 3 results in 2 (20/3 = 6 with a
remainder of 2.



moire
Pronounced "mor-ray."  In computer graphics, a
visible distortion.  It results from a variety of
conditions; for example, when scanning halftones at
a resolution not consistent with the printed
resolution or when superimposing curved patterns on
one another.  Internal monitor misalignment can
also be a cause.



molecular beam epitaxy
A technique that "grows" atomic-sized layers on a
chip rather than creating layers by diffusion.



MOM
See Microsoft Office.



monadic
One.  A single item or operation that deals with
one item or operand.



Monarch
A data capture program from Personics, Wilmington,
MA, that is used to transfer data from mainframe
and minicomputer reports to the PC.  It uses report
files that contain data ready to print.  Users
identify the data directly from the report format
on screen, and the program copies the data into the
fields of various database or spreadsheet formats
for the PC.



monitor
(1) A display screen used to present output from a
computer, camera, VCR or other video generator.  A
monitor's clarity is based on video bandwidth, dot
pitch, refresh rate and convergence.  See analog
monitor, digital monitor and interlaced.

(2) Software that provides utility and control
functions such as setting communications
parameters.  It typically resides in a ROM chip and
contains startup and diagnostic routines.

(3) Software that monitors the progress of
activities within a computer system.

(4) A device that gathers performance statistics of
a running system via direct attachment to the CPU's
circuit boards.



monochrome
Also called "mono."  The display of one foreground
color and one background color; for example, black
on white, white on black and green on black.

   Non-color laptop PCs commonly use "monochrome
VGA" screens, which are actually gray-scale
screens.  This is like black and white TV and is
not the same as the monochrome screens widely used
over the years on mini and mainframe terminals and
PCs using the MDA adapter, which display a solid
color and no shades in between.



monolithic integrated circuit
The common form of chip design, in which the base
material (substrate) contains the pathways as well
as the active elements that take part in its
operation.



monophonic
Sound reproduction using a single channel.
Contrast with stereophonic.



monospacing
Uniform horizontal spacing, such as 10 characters
per inch.  Contrast with proportional spacing.



Monte Carlo method
A technique that provides approximate solutions to
problems expressed mathematically.  Using random
numbers and trial and error, it repeatedly
calculates the equations to arrive at a solution.



MORE II
A Macintosh desktop presentation program and
outline processor from Symantec Corporation,
Cupertino, CA, that includes writing, spell
checking, presentation-quality text and graphics
and 35mm slide output.



morphing
Transforming one image into another; for example, a
car into a tiger.  From metamorphosis.  See
tweening.



morray
See moire.



Morse code
A character code represented by dots and dashes,
developed by Samuel Morse in the mid-19th century.
A dot can be a voltage, carrier wave or light beam
of one duration, while a dash is a longer duration.
It was used to send telegraph messages before the
telephone and was used in World War II for
signalling by light.



MOS
(Metal Oxide Semiconductor)  Pronounced "moss."
One of two major categories of chip design (the
other is bipolar).  It derives its name from its
use of metal, oxide and semiconductor layers.
There are several varieties of MOS technologies,
including PMOS, NMOS and CMOS.



Mosaic
An Internet utility that lets you browse through
the Worldwide Web.  It was created by the
University of Illinois National Center for
Supercomputing Applications and released on the
Internet in early 1993.  A variety of Mosaic-based
products are expected for business use.



MOSFET
(Metal Oxide Semiconductor Field Effect Transistor)
A common type of transistor fabricated as a
discrete component or into MOS integrated circuits.



most significant digit
The leftmost, non-zero digit in a number.  It is
the digit with the greatest value in the number.



motherboard
The main printed circuit board in an electronic
device, which contains sockets that accept
additional boards.  In a personal computer, the
motherboard contains the bus, CPU and coprocessor
sockets, memory sockets, keyboard controller and
supporting chips.

   Chips that control the video display, serial and
parallel ports, mouse and disk drives may or may
not be present on the motherboard.  If not, they
are independent controllers that are plugged into
an expansion slot on the motherboard.



Motif
The graphical user interface (GUI) endorsed by the
Open Software Foundation.  It has become the
standard graphical interface for UNIX.  Motif,
Windows and Mac are the three major GUIs.  See OSF.



motion path
In computer graphics, the path to be followed by an
animated object.



Motorola
(Motorola, Inc., Schaumburg, IL)  A leading
manufacturer of semiconductor devices founded in
Chicago in 1928 by Paul V. Galvin as the Galvin
Manufacturing Corporation.  Its first product
allowed radios to operate from household current
instead of batteries.  In the 1930s, the company
commercialized car radios under the Motorola brand
suggesting "sound in motion," and in 1947, changed
the company name.

   By the 1960s, it was a leader in communications
and consumer electronics and had built its first
semiconductor facility.  It eventually moved from
the consumer side, selling its color TV business in
the mid-1970s.

   Although Motorola is known in computers for its
68000 microprocessor family, and now the PowerPC
line, it is also involved in radio and data
communications systems and automotive and
industrial products, among others.



mount
To cause a file on a remote workstation or server
to be available for access locally.  For example,
in NFS (Network File System), a server maintains a
list of its directories that are available to
clients.  When a client mounts a directory on the
server, that directory and its subdirectories
become part of the client's directory hierarchy.
See automounting.



mouse
A puck-like object used as a pointing and drawing
device.  As it is rolled across the desktop, the
screen cursor (pointer) moves correspondingly.

   It is similar to the tablet cursor on a
digitizer tablet; however, the tablet cursor makes
contact with the tablet with absolute reference.
Placing it on the upper left part of the tablet
moves the screen cursor to that same location on
screen.

   With a mouse, movement is relative; the screen
cursor moves from its existing location.  The mouse
could be moved across your arm, and the screen
cursor would move as well.  See mechanical mouse,
optical mouse, serial mouse, bus mouse and mickey.



mouse pad
A fabric-covered rubber pad roughly 9" square that
provides a smooth surface for rolling a mouse.



mouse port
A socket in the computer into which a mouse is
plugged.



MOV
(1) (Metal Oxide Varistor)  A discrete electronic
component used in surge suppresssors that diverts
excessive voltage to the ground and/or neutral
lines.

(2) An assembly language instruction that moves
(copies) data from one location to another.



move
(1) In programming, to copy data from one place in
memory to another.  At the end of the move, source
and destination data are identical.

(2) In word processing and graphics, to relocate
text and images to another part of the document or
drawing.



movie file
A file that contains full-motion, digital video,
such as an AVI file.



Mozart
A screen scraper from Mozart Systems Corporation,
Burlingame, CA, that is used to turn a character-
based mainframe screen into a Windows or DOS front
end via 3270 emulation.  It is noted for being able
to easily combine multiple terminal screens into
one.  Mozart was originally named Enter 3270.



MP
See multiprocessing.



MPC
(Multimedia PC)  Requirements for a multimedia PC
as specified by the Multimedia PC Marketing
Council, a subsidiary of the Software Publishers
Association.  Address: 1730 M St., N.W.,
Washington, DC 20036, 202/331-0494.

   Vendors certified by the Multimedia PC Marketing
Council may display the MPC or MPC2 insignias on
their products.

   The first MPC specification was published in
1990.  Level 2 of the specification was published
in May 1993, which reflects the demands made by the
latest multimedia hardware and software.  Level 2
is backward compatible with Level 1.


              MINIMUM REQUIREMENTS
                   Level 1           Level 2

    RAM          2MB               4MB
    Processor    386SX 16MHz       486SX 25MHz
    Floppy disk  1.44MB 3.5"       1.44MB 3.5"
    Hard disk    30MB              160MB
    CD-ROM       150KB transfer    300KB transfer
                  rate, 1 second    rate, 400 ms
                  access time       access time
                                    CD-ROM XA ready
                                    multisession
    Sound        8-bit, 8 voice    16-bit, 8 voice
                  synthesizer       synthesizer
                  MIDI playback     MIDI playback
    Video        640x480x16        640x480x64K
    Ports        MIDI, joystick    MIDI, joystick


              RECOMMENDED FEATURES
                   Level 1           Level 2

    RAM          ------------      8MB
    CD-ROM       64KB on-board     64KB on-board
                  buffer            buffer
    Sound        ------------      CD-ROM XA audio,
                                    support for IMA
                                    adopted ADPCM
                                    algorithm
    Video        640x480x256       Able to deliver
                                    1.2 megapixels
                                    per second
                                    without using
                                    more than 40%
                                    of CPU
                                    bandwidth





MPC601
See PowerPC.



MPE/iX
(MultiProgramming Executive/POSIX)  A POSIX-
compliant multitasking operating system that runs
on the HP 3000 series.  The earlier non-POSIX
version was called MPE.



MPEG
(Moving Pictures Experts Group)  An ISO/ITU-TSS
standard for compressing full-motion video.  MPEG I
provides a standard image of 352x240, 30 fps, 15-
bit color and CD-quality sound.  MPEG II is an
evolving standard for full broadcast-quality video.
MPEG I is used in Video CD.  See JPEG.



MPP
(Massively Parallel Processor)  A parallel
processing architecture that uses hundreds or
thousands of processors.  Some might contend that a
computer system with 64 or more CPUs is a massively
parallel processor.  However, the number of CPUs is
not so much the issue as the architecture.  MPP
systems use a different programming paradigm than
the more common symmetric multiprocessing (SMP)
systems used as servers.

   In an MPP, each CPU contains its own memory and
copy of the operating system and application.  As a
result, an information processing problem must be
breakable into pieces that can be all solved
simultaneously.  In scientific environments,
simulations and various mathematical problems can
be split apart and processed at the same time.  In
the business world, database searches lend
themselves to this.  For example, a parallel data
query (PDQ) breaks a query into multiple searches
so that several parts of the database can be
searched concurrently.  See SMP.



MPR II
The Swedish government standard for maximum video
terminal radiation.  The earlier MPR I is less
stringent.  See TCO.



MPU
(MicroProcessor Unit)  Same as microprocessor.



MPU-401
A MIDI standard from Roland Corporation that has
become the de facto interface for connecting a
personal computer to a MIDI device.



MRCI
(Microsoft Realtime Compression Interface)  The
programming interface for Microsoft's DoubleSpace
technology used in DOS 6.



ms
(1) (MilliSecond)  See space/time.

(2) (MS) See Microsoft.



MS-DOS
(MicroSoft-Disk Operating System)  A single user
operating system for PCs from Microsoft.  It is
functionaly identical to IBM's PC-DOS version,
except that starting with DOS 6, MS-DOS and PC-DOS
each provide different sets of auxiliary utility
programs.  Both MS-DOS and PC-DOS are called DOS.
See DOS.



MS-Net
(MicroSoft Network)  Microsoft's version of PC-
Network introduced in 1985.



MS-Windows
(MicroSoft Windows)  See Windows.



MSa/s
(MegaSAmples per Second)  A measurement of sampling
rate in millions of samples per second.



MSCDEX
(MicroSoft CD-ROM EXtensions)  See CD-ROM
Extensions.



MSD
(MicroSoft Diagnostics)  A utility that accompanies
Windows 3.1 and DOS 6 that reports on the internal
configuration of the PC.  A variety of information
on disks, video, drivers, IRQs and port addresses
is provided.



MSDOS.SYS
One of the disk files that make up MS-DOS.  The
fundamental parts of MS-DOS are contained in
MSDOS.SYS and IO.SYS, both of which are hidden
system files.  The IBM version (PC-DOS) is made up
of IBMDOS.COM and IBMBIO.COM.



MSI
(Medium Scale Integration)  Between 100 and 3,000
transistors on a chip.  See SSI, LSI, VLSI and
ULSI.



MSP
(1) A Microsoft Paint graphics file format.

(2) (Multiprocessing Server Pack)  A utility that
enables LAN Manager to utilize a computer's
multiprocessing capabilities.

(3) An operating system used in Fujitsu IBM-
compatible mainframes.



MTA
(Message Transfer Agent)  The store and forward
part of a messaging system.  See messaging system.



MTBF
(Mean Time Between Failure)  The average time a
component works without failure.  It is the number
of failures divided by the hours under observation.



MTS
(Modular TV System)  The stereo channel added to
the NTSC standard, which includes the SAP audio
channel for special use.



MTTR
(Mean Time To Repair)  The average time it takes to
repair a failed component.



MUG
(Macintosh User Group)  There are many Mac user
groups throughout the world.  One organization that
disseminates press releases and product ads to over
1,300 MUGs is Pawtuckaway Graphics, 53 Lakeview
Dr., Raymond, NH 03077, 603/895-6227.



multi-station access unit
See MAU.



multi-timbral
The ability to play multiple instrument sounds
(patches) simultaneously.  See MIDI patch and
timbre.



MULTIBUS
An advanced bus architecture from Intel used in
industrial, military and aerospace applications.
It includes message passing, auto configuration and
software interrupts.  MULTIBUS I is 16-bits;
MULTIBUS II is 32-bits.



multicast
To transmit a message to multiple recipents at the
same time.  Multicasting is used in
teleconferencing and data communications networks.
Multicast is a one-to-many transmission that
implies sending to several designated recipients,
whereas broadcast implies sending to everyone
connected to the network.  Contrast with unicast.



multicast backbone
See Mbone.



multichip module
See MCM.



multicomputer
A computer made up of several computers.  The term
generally refers to an architecture in which each
processor has its own memory rather than multiple
processors with a shared memory.  See parallel
computing.



MULTICS
(MULTiplexed Information and Computing Service)
Developed at MIT and Bell Labs in the mid 1960s,
MULTICS was the first timesharing operating system.
It was used on GE's mainframes, which were absorbed
into the Honeywell product line, later acquired by
Bull.



multidimensional views
Looking at data in several dimensions; for example,
sales by region, sales by sales rep, sales by
product category, sales by month, etc.



multidrop line
See multipoint line.



MultiFinder
See Finder.



multifrequency monitor
A monitor that adjusts to all frequencies within a
range (multiscan) or to a set of specific
frequencies, such as VGA and Super VGA.



multilaunch
To open the same application based in a server
simultaneously from two or more clients.



multiline
A cable, channel or bus that contains two or more
transmission paths (wires or optical fibers).



multimastering
See bus mastering.



MultiMate
A PC word processing program from Ashton-Tate that
was originally noted for its similarity to the Wang
word processors of the 1970s.  Version 4.0 (1989)
introduced a number of advanced features.



multimedia
Disseminating information in more than one form.
It includes the use of text, audio, graphics,
animated graphics and full-motion video.
Multimedia programs are typically games,
encyclopedias and training courses on CD-ROM.
However, any application with sound and/or video
can be called a multimedia program.  See hot topics
and MPC.



Multimedia Extensions
Windows routines that support audio recording and
playback, animation playback, joysticks, MIDI, the
MCI interface for CD-ROM, videodiscs, videotapes,
etc., and the RIFF file format.  See MPC.



multimedia PC
A PC that includes stereo sound and a CD-ROM drive.
PCs that are sold with the MPC label meet the
technical requirements of the Multimedia PC
Marketing Council, but the requirements are easily
met today with new 486 PCs and double-speed CD-ROM
drives.

   To upgrade an older system to multimedia
requires installing a CD-ROM drive, a sound card
and shielded speakers, which can be purchased
separately or together in a multimedia upgrade kit.
See MPC and multimedia upgrade kit.



multimedia upgrade kit
The hardware and software necessary to turn a
standard PC into a multimedia PC (MPC).  The
package includes a CD-ROM drive, sound card and
speakers.  Some combination of bundled software
and/or CD-ROMs may also be included.  The advantage
of the kit is that the CD-ROM controller card and
sound card have been preset to avoid potential
conflicts with each other, and the correct cables
are included.  See CD-ROM audio cable.



multimode fiber
An optical fiber with a core diameter of from 50 to
100 microns.  It is the most commonly used optical
fiber.  Light can enter the core at different
angles, making it easier to connect the light
source.  However, light rays bounce around within
the core causing some distortion and providing less
bandwidth than single-mode fiber.  Contrast with
single-mode fiber.



MultiPlan
An early spreadsheet for CP/M machines and PCs from
Microsoft.  It was one of the first spreadsheets.



Multiple Document Interface
See MDI.



Multiple Master
A font technology from Adobe Systems, Mountain
View, CA, that allows a typeface to be generated in
different styles, from condensed to expanded and
from light to heavy.  Multiple Master can generate
fonts that are more optically correct at both
extremes in size from very small to very large than
standard Type 1 fonts.



multiple zone recording
See ZBR.



multiplexing
Transmitting multiple signals over a single
communications line or computer channel.  The two
common multiplexing techniques are FDM, which
separates signals by modulating the data onto
different carrier frequencies, and TDM, which
separates signals by interleaving bits one after
the other.  See inverse multiplexing.



multiplexor
In communications, a device that merges several
low-speed transmissions into one high-speed
transmission and vice versa.



multiplexor channel
A computer channel that transfers data between the
CPU and several low-speed peripherals (terminals,
printers, etc.) simultaneously.  It may have an
optional burst mode that allows a high-speed
transfer to only one peripheral at a time.



multiplier-accumulator
A general-purpose floating point processor that
multiplies and accumulates the results of the
multiplication.  Newer versions also perform
division and square roots.



multipoint line
In communications, a single line that interconnects
three or more devices.



multiport repeater
A hub in a 10BaseT network is often known as a
multiport repeater, because it sends any input
signal to all outputs.  See 10BaseT.



multiported memory
A type of memory that provides more than one access
path to its contents.  It allows the same bank of
memory to be read and written simultaneously.  See
video RAM.



multiprocessing
Simultaneous processing with two or more processors
in one computer, or two or more computers
processing together.  When two or more computers
are used, they are tied together with a high-speed
channel and share the general workload between
them.  If one fails, the other takes over.

   It is also accomplished in special-purpose
computers, such as array processors, which provide
concurrent processing on sets of data.  Although
computers are built with various overlapping
features, such as executing instructions while
inputting and outputting data, multiprocessing
refers specifically to concurrent instruction
executions.  See parallel processing, bus mastering
and fault tolerant.



multiprogramming
Same as multitasking.



multiscan monitor
A monitor that adjusts to all frequencies within a
range.  See multifrequency monitor.



multisession
See Photo CD.



MultiSync monitor
A family of multiscan monitors from NEC
Technologies, Inc.  NEC popularized the multiscan
monitor.



multitasking
The running of two or more programs in one computer
at the same time.  The number of programs that can
be effectively multitasked depends on the type of
multitasking performed (preemtive vs cooperative),
CPU speed and memory and disk capacity.

   Programs can be run simultaneously in the
computer because of the differences between I/O and
processing speed.  While one program is waiting for
input, instructions in another can be executed.
During the milliseconds one program waits for data
to be read from a disk, millions of instructions in
another program can be executed.  In interactive
programs, thousands of instructions can be executed
between each keystroke on the keyboard.

   In large computers, multiple I/O channels also
allow for simultaneous I/O operations to take
place.  Multiple streams of data are being read and
written at the exact same time.

   In the days of mainframes only, multitasking was
called multiprogramming, and multitasking meant
multithreading.



multithreading
Multitasking within a single program.  It allows
multiple streams of execution to take place
concurrently within the same program, each stream
processing a different transaction or message.
Multithreading generally uses reentrant code, which
cannot be modified when executing, so that the same
code can be shared by multiple programs.

   In a symmetric multiprocessing (SMP) operating
system, multithreading allows multiple CPUs to be
controlled at the same time.  It is also used to
create synchronized audio and video applications.



multiuser
A computer shared by two or more users.



multiuser DOS
(1) A DOS-compatible operating system that runs
multiple terminals from a single PC.

(2) (Multiuser DOS)  A multiuser DOS-compatible
operating system from Novell that runs multiple
terminals from a single 386 or higher PC.
Supersedes Concurrent DOS.



multivariate
The use of multiple variables in a forecasting
model.



MUMPS
An advanced, high-level programming language and
integrated database used for business applications.
It has extensive string handling making it suitable
for databases with vast amounts of free text.

   MUMPS has unique features including the ability
to store both data and program statements in its
database.  In addition, formulas written in a
program can be stored and used by other programs.
Developed in 1966 at Massachusetts General Hospital
(Mass. Utility MultiProgramming System), it has
been used extensively in health-care.

   The following example converts Fahrenheit to
Celsius:

   READ "Enter Fahrenheit ",FAHR
   SET CENT=(FAHR-32)*5/9
   WRITE "Celsius is", CENT


   The M Technology Association (formerly MUMPS
Users Group) is an organization that supports the
MUMPS community through training, meetings and
distribution of publications and software.
Address: 1738 Elton Rd., Suite 205, Silver Spring,
MD 20903, 301/431-4070.



music CD
Generally refers to an audio CD, otherwise known as
"Red Book audio."  However, the term could refer to
a CD-ROM that contains sound files, such as WAV and
MID files.



MUX
(MUltipleXor)  See multiplexor.



MVGA
(Monochrome VGA)  The type of display often found
on a non-color laptop.  It should more accurately
be called "gray scale VGA," since monochrome means
two colors; for example, black and white and no
shades in between.



MVIP
(MultiVendor Integration Protocol)  A voice bus and
switching protocol for PCs originated by a number
of companies, including Natural Microsystems of
Natick, MA, its major supporter.  It provides a
second communications bus within the PC that is
used to multiplex up to 256 full-duplex voice
channels from one voice card to another.

   Digital voice, fax, video (any digital data) is
bussed over a ribbon cable connected at the top of
each ISA, EISA or Micro Channel card.  For example,
several fax boards could be cabled to a board that
multiplexes their lines onto a T1 channel.  Using
the high bandwidth of this second bus, video
conferencing systems are built around MVIP.

   MVIP products can make the PC perform like a
small-scale PBX.  For example, an interactive voice
response system on one card could pass incoming
voice conversations to a card that switches the
lines to live agents in a call center.

   The ability to plug a card into a standard AT
bus and perform voice and video processing is
opening up a whole new world to vendors.  It allows
far more flexible and affordable systems to be
built, and it helps solve worldwide interface
problems.  A variety of interface cards from
different countries can be plugged in, allowing
MVIP products to connect to telephone systems all
around the world.



MVP
(Multimedia Video Processor)  A high-speed DSP chip
from TI introduced in 1994.  Formally the
TMS320C80, it combines RISC technology with the
functionality of four DSPs on one chip.



MVS
(Multiple Virtual Storage)  Introduced in 1974, the
primary operating system used on IBM mainframes
(the others are VM and DOS/VSE).  MVS is a batch
processing-oriented operating system that manages
large amounts of memory and disk space.  Online
operations are provided with CICS, TSO and other
system software.

   MVS/XA (MVS/eXtended Architecture) manages the
enhancements, including 2GB of virtual memory,
introduced in 1981 with IBM's 370/XA architecture.

   MVS/ESA (MVS/Enterprise Systems Architecture)
manages the enhancements made to large scale
mainframes, including 16TB of virtual memory,
introduced in 1988 with IBM's ESA/370 architecture.
 MVS/ESA runs on all models of the System/390
ES/9000 product line introduced in 1990.



MVS/ESA
See MVS.



MVS/XA
See MVS.



n-dimensional
Some number of dimensions.



N-key rollover
A keyboard circuit built into most keyboards and
vital for fast typing.  To test this capability,
press four adjacent keys in sequence without
removing any finger from any of the keys.  If all
four letters appear on screen, it has this feature.



NACCB
(National Association of Computer Consultant
Businesses)  An organization representing companies
that provide professional help in information and
engineering fields.  Founded in 1987, it is
concerned with legislation that affects computer
consultants.  Address: 1250 Connecticut Ave. N.W.,
Suite 700, Washington, DC 20036, 202/637-9134.



NACOMEX
(NAtional COMputer EXchange)  See computer
exchange.



NAEC
See NetWare certification.



NAK
(Negative AcKnowledgement)  A communications code
used to indicate that a message was not received,
or that a terminal does not wish to transmit.
Contrast with ACK.



name service
See naming service.



Named Pipes
An IPC facility in LAN Manager that allows data to
be exchanged from one application to another either
over a network or running within the same computer.
The use of the term pipes for interprocess
communication was coined in UNIX.



naming service
Software that converts a name into a physical
address on a network, providing logical to physical
conversion.  Names can be user names, computers,
printers, services or files.  The transmitting
station sends a name to the server containing the
naming service software, which sends back the
actual address of the user or resource.

   It serves as a Yellow Pages for the network,
which is precisely what Sun's NIS system was
originally called.  Novell's naming service for
NetWare 4.0 is called NDS (NetWare Directory
Service).  In AppleTalk, the naming service is
embedded within the protocol.  See directory
service.



NAND
(Not AND)  A Boolean logic operation that is true
if any single input is false.  Two-input NAND gates
are often used as the sole logic element on gate
array chips, because all Boolean operations can be
created from NAND gates.

          Inputs  Output 
         Ŀ
          0   0   1  
          0   1   1  
          1   0   1  
          1   1   0  
         





nano
One billionth or 10 to the -9th power.



nanometer
One billionth of a meter.  One nanometer is equal
to 10 angstroms.  Nanometers are used to measure
the wavelengths of light.



nanosecond
One billionth of a second.  Used to measure the
speed of logic and memory chips, a nanosecond can
be visualized by converting it to distance.  In one
nanosecond, electricity travels about six inches in
a wire.

   Even at 186,000 miles per second, electricity is
never fast enough for the hardware designer who
worries over a few inches of circuit path.  The
slightest delay is multiplied millions of times,
since millions of pulses are sent through a wire in
a single second.  See space/time.



nanotechnology
A future science that builds devices at the atomic
and molecular level.  For example, a bit might be
represented by only one atom some time in the
future.  Nanotechnology could be used to build
anything, not just computers and communications
devices.



NAPLPS
(North American Presentation-Level Protocol Syntax)
An ANSI-standard protocol for videotex and
teletext.  It compresses data for transmission over
narrow-bandwidth lines and requires decompression
on the receiving end.  PRODIGY uses this format for
transmitting and displaying some of its graphics.



narrowband
In communications, a voice grade transmission of
2,400 bps or less, or a sub-voice grade
transmission from 50 to 150 bps.



NAS
(Network Application Support)  Digital's
implementation of open systems, which provides
standards-based software that allows a variety of
workstations (VMS, ULTRIX, Sun, DOS, Windows, OS/2,
Mac, etc.) to interface via VAX and ULTRIX servers.



NASI
(1) (NetWare Asynchronous Service Interface)  A
protocol from Novell for connecting to modems in a
communications server.  It was derived from the
NCSI protocol.  NASI provides more advanced
features than the common int 14 (interrupt 14)
method.  It allows a specific modem or line to be
chosen.  It frees the call more quickly, and it
transfers data more efficiently.

(2) (National Association of Systems Integrators)
An organization of more than 5,000 members founded
in 1991, dedicated to exchanging up-to-date
information on members' products and services.  Its
annual Computer Suppliers & Services Directory, in
print and on disk, is organized by zipcode.
Address: 412 High Plain Street, Unit #1, Walpole,
MA 02081, 508/668-8900.



National Association of Systems Integrators
See NASI.



National Computer Exchange
See computer exchange.



National Computer Graphics Association
See NCGA.



National Computer Security Center
See NCSC.



National Cristina Foundation
A not-for-profit organization, founded by Bruce
McMahan and Yvette Marrin and named in honor of
McMahan's daughter who has cerebral palsy.  It
channels used and surplus computers and software to
NCF network partner organizations that train people
with disabilities, at risk students and the
disadvantaged in the U.S. and abroad.  If you have
old equipment that you no longer need, please give
them a call.  Address: 591 W. Putnam Ave.,
Greenwich, CT 06830, 800/274-7846.



National Information Infrastructure
See NII.



National Institute of Standards & Technology
See NIST.



National Office Machine Dealers Association
See BTA.



National Software Testing Lab
See NSTL.



National TV Standards Committee
See NTSC.



native language
Same as machine language.  See native mode.



native mode
(1) The normal running mode of a computer,
executing programs from its built-in instruction
set.  Contrast with emulation mode.

(2) The highest performance state of a computer,
such as a 486 or Pentium running in Protected Mode.



NATURAL
A fourth-generation language from Software AG,
Reston, VA, that runs on a variety of computers
from micro to mainframe.



natural language
English, Spanish, French, German, Japanese,
Russian, etc.



natural language query
A query expressed by typing English, French or any
other spoken language in a normal manner.  For
example, "how many sales reps sold more than a
million dollars in any eastern state in January?"
In order to allow for spoken queries, both a voice
recognition system and natural language query
software are required.



natural language recognition
Same as voice recognition.



NAU
(1) (Network Access Unit)  An interface card that
adapts a computer to a local area network.

(2) (Network Addressable Unit)  An SNA component
that can be referenced by name and address, which
includes the SSCP, LU and PU.



NB card
(NuBus card)  See NuBus.



NC
See numerical control.



NCB
(Network Control Block)  A packet structure used by
the NetBIOS communications protocol.



NCF
See National Cristina Foundation.



NCF file
(NetWare Command File)  A file of NetWare commands
that are executed one at a time, similar to a DOS
batch (.BAT) file.  The NetWare AUTOEXEC.NCF file
is executed in the server at startup, just like the
DOS AUTOEXEC.BAT file.



NCGA
(National Computer Graphics Association)  An
organization dedicated to developing and promoting
the computer graphics industry.  It maintains a
clearinghouse for industry information and strives
to encourage communication among computer graphics
users, consultants, educators and vendors.
Address: 2722 Merrilee Dr., Suite 200, Fairfax, VA
22031, 800/225-NCGA.



NCP
(1) (Network Control Program)  See SNA and network
control program.

(2) (NetWare Core Protocol)  Application layer
protocols in the NetWare network operating system.
It is the internal NetWare language used to
communicate between client and server and provides
functions such as opening, closing, reading and
writing files and obtaining access to the NetWare
bindery and NDS naming service databases.

(3) (Not Copy Protected)  Software that can be
easily copied.



NCR
See AT&T GIS.



NCR paper
(No Carbon Required paper)  A multiple-part paper
form that does not use carbon paper.  The ink is
adhered to the reverse side of the previous sheet.



NCSC
(National Computer Security Center)  The arm of the
U.S. National Security Agency that defines criteria
for trusted computer products.  Following are the
Trusted Computer Systems Evaluation Criteria
(TCSEC), DOD Standard 5200.28, also known as the
Orange Book, and the European equivalent.  The Red
Book is the Orange Book counterpart for networks.

   Level D is a non-secure system.

   Level C provides discretionary access control
(DAC).  The owner of the data can determine who has
access to it.

   C1  Requires user log-on, but allows group ID.

   C2  Requires individual user log-on with
       password and an audit mechanism.

   Levels B and A provide mandatory access control
(MAC).  Access is based on standard DOD clearances.
Each data structure contains a sensitivity level,
such as top secret, secret and unclassified, and is
available only to users with that level of
clearance.

   B1  DOD clearance levels.

   B2  Guarantees path between user and the
       security system.  Provides assurances that
       system can be tested and clearances cannot
       be downgraded.

   B3  System is characterized by a mathematical
       model that must be viable.

   A1  System is characterized by a mathematical
       model that can be proven.  Highest
       security.  Used in military computers.


                 European Ratings
The European Information Technology Security
Evaluation Criteria (ITSEC) is similar to TCSEC,
but rates functionality (F) and effectiveness (E)
separately.

   Orange Book
      TCSEC      ITSEC
         D         E0
        C1      F-C1, E1
        C2      F-C2, E2
        B1      F-B1, E3
        B2      F-B2, E4
        B3      F-B3, E5
        A1      F-B3, E6





NCSI
(Network Communications Services Interface)  Also
called "nixie," it is a protocol used to handle
serial port communications on a network.  NCSI
applications talk to the NCSI driver rather than
directly to the COM port, which allows redirection
of the data to a communications server on the
network.  See NASI.



NDIS
(Network Driver Interface Specification)  A network
driver interface from Microsoft.  See network
driver interface.



NDS
See NetWare Directory Service.



NE
(Not Equal to)  See relational operator.



NE2000
An Ethernet network adapter from Novell that has
become a de facto standard.  Many Ethernet adapters
are NE2000 compatible.



near letter quality
See NLQ.



near pointer
In an x86 segmented address, a memory address
within a single segment (the offset).  Contrast
with far pointer.



NEAT chipset
(New Enhanced AT chipset)  A set of chips used to
build an AT-class machine from Chips and
Technologies, Inc.  EMS capability is included.
The CPU, BIOS and NEAT chipset are the primary
logic chips on a 286-based PC.



negative logic
The use of high voltage for a 0 bit and low voltage
for a 1 bit.  Contrast with positive logic.



nematic
The stage between a crystal and a liquid that has a
threadlike nature; for example, a liquid crystal.



nemonic
See mnemonic.



neper
The unit of measurement based on Napierian
logarithms that represents the ratio between two
values, such as current or voltage.



nerd
A person typically thought of as dull socially.
Nerds often like technical work and are generally
introspective.  Contrast with hacker, a technical
person that may or may not be a nerd.



nesting
In programming, the positioning of a loop within a
loop.  The number of loops that can be nested may
be limited by the programming language.  See loop.



net
Abbreviation of network.  "The Net" often refers to
the Internet.



NetBEUI
(NetBIOS Extended User Interface)  Pronounced "net-
booey," it is an enhanced version of the NetBIOS
protocol used by network operating systems such as
LAN Manager, LAN Server, Windows for Workgroups and
Windows NT.  It formalizes the transport frame that
was never standardized in NetBIOS and adds
additional functions.



NetBIOS
A commonly-used network protocol for PC local area
networks.  NetBIOS provides session and transport
services (layers 4 and 5 of the OSI model).
NetBIOS did not provide a standard frame format for
transmission over the network, causing various
different implementations of NetBIOS to be created.
For example, Artisoft's LANtastic uses a
proprietary version of NetBIOS for transmission
between client and server.  The frame format was
later formalized in NetBEUI.

   There are two NetBIOS modes.  The Datagram mode
is the fastest mode, but does not guarantee
delivery.  It uses a self-contained packet with
send and receive name, usually limited to 512
bytes.  If the recipient device is not listening
for messages, the datagram is lost.  The Session
mode establishes a connection until broken.  It
guarantees delivery of messages up to 64KB long.

   There is no routing layer in NetBIOS or NetBEUI,
thus there is no internetworking capability.  Other
protocols, such as IPX and IP, must be used for
internetworking, although NetBIOS is often used to
establish the connection as in the NetWare example
below.  See NetBEUI.


 OSI LAYER     NETWARE EMULATION OF NETBIOS
            Ŀ
     5            NetBIOS Session Layer     
            Ĵ
     4         NETWARE TRANSPORT PROTOCOL   
             PEP (Packet Exchange Protocol) 
            Ĵ
     3         NETWARE NETWORKING PROTOCOL  
             IPX (Internet Packet Exchange) 
            Ĵ
     2              DATA LINK LAYER         
                 (Ethernet, Token Ring)     
            Ĵ





netbooey
See NetBEUI.



netiquette
(NETwork etIQUETTE)  Proper manners when using an
online service or BBS.  Emily Post may not have
told you to curtail your cussing via modem, but
netiquette has been established to remind you that
profanity is not in good form over the network.

   Using UPPER CASE TO MAKE A POINT all the time
and interjecting emoticons throughout a message is
also not good netiquette.  See flame.



NetNews
See USENET.



NETROOM
A DOS memory manager from Helix Software Company,
Long Island City, NY.  NETROOM3's "cloaking" runs
the system and video BIOS in extended memory
freeing up previously-used upper memory blocks
(UMBs).  New BIOSs are included which provide an
automatic BIOS upgrade for the PC.  Also included
are cloaked utilities (disk cache, RAM drive,
screen saver, etc.) that run mostly in extended
memory.



NetScape
Mosaic utilities from Mosaic Communications
Corporation that provide secure transmission over
the Internet.  Client support for Windows, X Window
and Macintosh is provided.  NetScape server
software provides encryption based on the RSA
method.



NetView
IBM SNA network management software that provides
centralized monitoring and control for SNA, non-SNA
and non-IBM devices.  NetView/PC interconnects
NetView with Token Ring LANs, Rolm CBXs and non-IBM
modems, while maintaining control in the host.



netViz
Network and flowchart diagramming software for
Windows from Quyen Systems, Inc., Rockville, MD.
It preserves interconnected lines between symbols
when the diagram is changed.  Predefined symbols
are included, and images can be imported to add to
the palette.  Text for each symbol is maintained in
a database, which can be exported as a master
inventory list.



NetWare
A family of network operating systems from Novell
that support DOS, OS/2, Mac and UNIX clients and
various LAN access methods including Ethernet,
Token Ring and ARCNET.  NetWare is the most widely-
used LAN control program.

   Personal NetWare is a peer-to-peer network
operating system, which allows any client
workstation to be a server.  It supersedes earlier
peer-to-peer versions known as NetWare Lite and
NetWare ELS (Entry Level System).  Personal NetWare
is also included with Novell's DOS operating
system.

   NetWare 2.x (originally Advanced NetWare 286)
runs in a dedicated file server (286 and up) and
supports up to 100 concurrent users per server.
This version is no longer being updated.

   NetWare 3.x (originally NetWare 386), which
supports up to 250 concurrent users, runs on 386
servers and up and takes advantage of the 32-bit
architecture.

   NetWare 4.0, introduced in 1993, is backward
compatible with NetWare 2.x and 3.x and includes
the NetWare Directory Service (NDS), which provides
X.500 compatibility (see NDS).  A NetWare 4.x
server supports up to 1,000 concurrent users.

   Except for Personal NetWare, NetWare is a stand-
alone operating system that runs in the server.  It
does not use DOS or any other operating system.
The hard disks in a NetWare server are formatted
with a Novell format, not a DOS format.

   SFT NetWare (System Fault Tolerant) provides
automatic recovery from network malfunctions.
NetWare for VMS provides NetWare connectivity to
VAX networks.  Portable NetWare provides NetWare
source code for conversion to other platforms.  See
IPX, SPX and MHS.



NetWare certification
Novell provides certification for technical
competence with self-study tests and courses given
at National Authorized Education Centers (NAECs).
Certificates include CNA (Certified NetWare
Administrator), CNE (Certified NetWare Engineer),
ECNE (Enterprise CNE, which includes WAN expertise)
and CNI (Certified NetWare Instructor).



NetWare Core Protocol
Application layer protocols in the NetWare network
operating system.  It is the internal NetWare
language used to communicate between client and
server and provides functions such as opening,
closing, reading and writing files and obtaining
access to the naming service databases (bindery and
NDS).



NetWare Directory Service
Also known as NDS, it is a global naming service in
NetWare 4.0 based on X.500 for compatibility with
other public directories.  The NDS Directory
maintains information about all the resources in
the network, including users, groups, servers,
volumes and printers.  NDS replaces the bindery
file used in previous versions of NetWare and is
backward compatible with it.

   Compared to the bindery's single server
orientation, NDS is designed to manage all servers
in the network and allows its database to be
replicated to support this capability.  With NDS,
users log into the network, not into a specific
server.

   In NDS, every network resouce, such as a user,
server, server volume, printer and print queue is
called an object.  Each object contains properties
(fields); for example, a user object would contain
login ID, password, name, address, telephone and
node address.  An NDS database is a hierarchical
structure that can store the resources of not only
multiple networks but the internetworking of an
entire multinational enterprise.



NetWare Global Messaging
E-mail software from Novell for NetWare 3.x that
includes directory synchronization across
distributed servers and provides optional
interfaces to X.400, SMTP and SNADS.  See SMF.



NetWare Loadable Module
Known as an NLM, it is software that enhances or
provides additional functions in a NetWare 3.x or
higher server.  Support for database engines,
workstations, network protocols, fax and print
servers are examples.  The NetWare 2.x counterpart
is a VAP.



NetWare Management System
Also known as NMS, it is an SNMP-based network
management software from Novell for monitoring and
controlling NetWare networks.



NetWare NFS
Software from Novell that implements the NFS
distributed file system on NetWare 3.11 servers. 
It allows UNIX and other NFS client machines to
access files on the NetWare server.  See LAN
Workplace and UnixWare.



NetWare Users International
A voluntary organization of more than 250 NetWare
user groups worldwide.  For information, call
800/228-4NUI within the U.S. or 801/429-7000
outside the U.S.



NetWire
Novell's BBS on CompuServe, which provides
technical support for its NetWare products.



network
(1) An arrangement of objects that are
interconnected.  See LAN and network database.

(2) In communications, the transmission channels
interconnecting all client and server stations as
well as all supporting hardware and software.



network access unit
See NAU.



network accounting
The reporting of network usage.  It gathers details
about user activity including the number of logons
and resources used (disk accesses and space used,
CPU time, etc.).



network adapter
A printed circuit board that plugs into both the
clients (personal computers or workstations) and
servers and controls the exchange of data between
them.  The network adapter provides services at the
data link level of the network, which is also known
as the access method (OSI layers 1 and 2).

   The most common network adapters are Ethernet
and Token Ring.  Sometimes, the Ethernet adapter is
built into the motherboard.  LocalTalk, which
provides the data link services of Apple's
AppleTalk network, is built into all Macintoshes.

   A transmission medium, such as twisted pair,
coax or fiber optic, interconnects all the adapters
in the network.  A network adapter is also called a
NIC, or network interface card.



network addressable unit
See NAU.



network administrator
A person who manages a communications network
within an organization.  Responsibilities include
network security, installing new applications,
distributing software upgrades, monitoring daily
activity, enforcing licensing agreements,
developing a storage management program and
providing for routine backups.



network analyzer
Software only or a combination of hardware and
software that monitors traffic on a network.  It
can also read unencrypted text transmitted over the
network.



network architecture
(1) The design of a communications system, which
includes the hardware, software, access methods and
protocols used.  It also defines the method of
control: whether computers can act independently or
are controlled by other computers monitoring the
network.  It determines future flexibility and
connectability to foreign networks.

(2) The access method in a LAN, such as Ethernet,
Token Ring and LocalTalk.



network card
See network adapter.



network cloud
A cloud-like symbol in a network diagram used to
reduce an entire communications network into points
of entry and exit.  It infers that although there
may be any number of switches, routers, trunks, and
other network devices within the cloud, the point
of interconnection to the cloud (network) is the
only technical issue in the diagram.  Clouds are
often used to depict a WAN (wide area network).



network control block
See NCB.



network control program
Software that manages the traffic between terminals
and the host mini or mainframe.  It resides in the
communications controller or front end processor.
In a personal computer LAN, it is called a network
operating system and resides in the server and
manages requests from the workstations.  IBM's SNA
network control program is called NCP.



network database
(1) A database that runs in a network.  It implies
that the DBMS was designed with a client/server
architecture.

(2) A database that holds addresses of other users
in the network.

(3) A database organization method that allows for
data relationships in a net-like form.  A single
data element can point to multiple data elements
and can itself be pointed to by other data
elements.  Contrast with relational database.



network driver
Software that performs the data link protocol in a
network and activates the network adapter.



network driver interface
A software interface between the transport protocol
and the data link protocol (network driver).  The
interface provides a protocol manager that accepts
requests from the transport layer and activates the
network adapter.  Network adapters with compliant
network drivers can be freely interchanged.

   This method allows multiple protocol stacks to
run over one network adapter.  For example, a PC
can connect to a NetWare network running SPX/IPX
and a UNIX network running TCP/IP.  It also allows
one transport protocol to run over different
network adapters; for example, SPX/IPX over
Ethernet and Token Ring.

   In PC LANs, the two primary network driver
interfaces are Novell's ODI and Microsoft's NDIS.
Novell provides an ODI interface utility that
allows NDIS and ODI protocols to work in the same
computer.



Network Driver Interface Specification
See NDIS.



Network File System
See NFS.



Network Information Services
See NIS.



network interface card
Same as network adapter.



network layer
Internetworking services provided by the network as
defined by layer 3 of the OSI model.  See OSI
model.



network management
Monitoring an active communications network in
order to diagnose problems and gather statistics
for administration and fine tuning.  Examples of
network management products are IBM's NetView, HP's
OpenView, Sun's SunNet Manager and Novell's NMS.
Almost all network management software supports the
SNMP network management protocol.  Other management
protocols are CMIP and DME.



network management console
The client component of network management software
that provides the user interface and "control room"
view of the network.



network manager
See network administrator.



network modem
A modem shared by all users in a network.  See ACS.



network operating system
Also called a NOS, it is an operating system that
manages network resources.  It manages multiple
requests (inputs) concurrently and provides the
security necessary in a multiuser environment.  It
may be a completely self-contained operating
system, such as NetWare, or it may require an
existing operating system in order to function (LAN
Manager requires OS/2; LANtastic requires DOS,
etc.).

   One piece of the network operating system
resides in each client machine and another resides
in each server.  It allows the remote drives on the
server to be accessed as if they were local drives
on the client machine.  It allows the server to
handle requests from the client to share files and
applications as well as network devices such as
printers, faxes and modems.

   In a peer-to-peer network, the network operating
system allows each station to be both client and
server.  In a non-peer-to-peer network, dedicated
servers are used, and files on a client machine
cannot be retrieved by other users.

   NetWare is the most widely used network
operating system in PC local area networks.  IBM's
LAN Server, Microsoft's LAN Manager, Banyan's VINES
and Windows NT are also used.  Artisoft's LANtastic
is an example of a popular peer-to-peer network
operating system.

   UNIX, combined with TCP/IP and NFS, VMS combined
with DECnet, the Mac OS combined with AppleTalk,
and SNA, combined with VTAM and NCP, also provide
network operating system services.



network protocol
A communications protocol used by the network.
There are many layers of network protocols.  See
OSI model.



network ready
Software designed to run in a network.  It implies
that multiple users can share databases without
conflict.



network security
The authorization of access to files and
directories in a network.  Users are assigned an ID
number and password that allows them access to
information and programs within their authority.
Network security is controlled by the network
administrator.



network segment
See LAN segment.



network server
See file server.



Networks Expo
Formerly NetWorld, it is a computer trade show
sponsored by the Blenheim Group.  See Blenheim
shows.



NetWorld
See Networks Expo.



neural network
A modeling technique based on the observed behavior
of biological neurons and used to mimic the
performance of a system.  It consists of a set of
elements that start out connected in a random
pattern, and, based upon operational feedback, are
molded into the pattern required to generate the
required results.  It is used in applications such
as robotics, diagnosing, forecasting, image
processing and pattern recognition.



New Era
See INFORMIX.



new media
See digital convergence.



newline
End of line code.  See CR/LF.



NeWS
(Network Extensible Windowing Support)  A networked
windowing system (similar to X Windows) from
SunSoft that renders PostScript fonts on screen the
way they print on a PostScript printer.



news and weather
See online services.



newsgroup
A collection of messages about a particular subject
on the Internet.  See USENET.



newsreader
An Internet utility, such as nn, rn or tin, that is
used to read the messages in a newsgroup.



Newton
An artificial intelligence technology from Apple
for use in PDAs and other hand-held and desktop
appliances.  See MessagePad.



NewWave
A PC operating environment from HP that runs
between DOS and Windows.  It integrates data and
activates tasks within the system.  Its object-
management facility allows data from different
applications to be merged to create a compound
document.  Hot links automatically update the
document if data in one of the source files is
updated.

   It allows for the creation of agents (automatic
procedures) that can be activated based on time or
events.  For example, at month end, an agent could
extract data from the corporate mainframe and
prepare a report using several application
programs.  Programs must be modified to run under
NewWave.



NexGen
See Nx586.



NeXT
(NeXT, Inc., Redwood City, CA)  Founded in 1985 by
Steven Jobs, co-founder of Apple, NeXT created a
family of high-resolution, UNIX-based workstations
running its NEXTSTEP environment.  The first
machine was introduced in 1988.  Manufacturing of
the hardware ceased in early 1993, but NeXT is
continuing with its NEXTSTEP software for the Intel
x86 platform.



NEXTSTEP
A UNIX-based, object-oriented development
environment from NeXT Computer, Redwood City, CA.
It runs on NeXT computers, x86s (386 and up) and
Sun and HP workstations, providing an advanced,
integrated environment for creating applications.
Insiginia Solution's SoftPC allows DOS and Windows
applications to run on a NEXTSTEP/x86 machine.  See
OpenStep.



NFS
(Network File System)  A distributed file system
from SunSoft that allows data to be shared across a
network regardless of machine, operating system,
network architecture or protocol.  This de facto
UNIX standard lets remote files appear as if they
were local on a user's machine.  The combination of
TCP/IP, NFS and NIS comprise the primary networking
components of UNIX.



NGM
See NetWare Global Messaging.



nibble
Half a byte (four bits).



nibble mode memory
A type of dynamic RAM that outputs four consecutive
bits (nibble) at one time.



NIC
(Network Interface Card)  Same as network adapter.



NICAD
A trademark of SAFT America Inc., Valdosta, GA, for
nickel cadmium products.  See nickel cadmium.



nickel cadmium
(NiCd) A rechargeable battery technology that has
been widely used in portable applications,
including portable computers.  It provides more
charge per pound than lead acid batteries, but less
than nickel hydride or zinc air.  Its major problem
is a so-called "memory effect," in which the
battery seems to remember how full it was when you
last charged it, and it doesn't go past that point
the next time.  Nickel cadmium batteries should be
completely drained periodically to maintain the
longest charge.  It uses a nickel and cadmium plate
and potassium hydroxide as the electrolyte.  See
lead acid, nickel hydride and zinc air.



nickel hydride
A rechargeable battery technology that provides
more charge per pound than lead acid and nickel
cadmium, but less than zinc air.  It does not
suffer from the nickel cadmium memory effect.  It
uses nickel and metal hydride plates with potassium
hydroxide as the electrolyte.  See lead acid,
nickel cadmium and zinc air.



NII
(National Information Infrastructure)  The proposal
by the Clinton/Gore administration to provide
universal high-bandwidth telecommunications
throughout the U.S.  Highlights are:

 (1) network funded by private industry
 (2) supports two-way communications of data,
     images, voice and video
 (3) services available to rich and poor alike
 (4) legislation overhauls Telecommunications Act
     of 1934 and the Modified Final Judgment that
     broke up AT&T
 (5) any service provider will be able to buy
     access to the network





Nile
A family of MIPS R4400-based servers from Pyramid
Technology Corporation, San Jose, CA.   The
machines run an SMP version of UNIX and provide
high availability by connecting multiple units in
clusters and by using RAID storage.



NIS
(Network Information Services)  A naming service
from SunSoft that allows resources to be easily
added, deleted or relocated.  Formerly called
Yellow Pages, NIS is a de facto UNIX standard.
NIS+ is a redesigned NIS for Solaris 2.0 products.
The combination of TCP/IP, NFS and NIS comprise the
primary networking components of UNIX.



NIST
(National Institute of Standards & Technology)  The
standards-defining agency of the U.S. government,
formerly called the National Bureau of Standards.



Nixdorf
See SNI.



nixie
See NCSI.



NJE
(Network Job Entry)  An IBM mainframe protocol that
allows two JES devices to communicate with each
other.



NLM
See NetWare Loadable Module.



NLQ
(Near Letter Quality)  The print quality that is
almost as sharp as an electric typewriter.  The
slowest speed of a dot matrix printer often
provides NLQ.



NMI
(NonMaskable Interrupt)  A high-priority interrupt
that cannot be disabled by another interrupt.  It
is used to report malfunctions such as parity, bus
and math coprocessor errors.



NMOS
(N-Channel MOS)  Pronounced "N moss."  A type of
microelectronic circuit used for logic and memory
chips.  NMOS transistors are faster than their PMOS
counterpart and more of them can be put on a single
chip.  It is also used in CMOS design.



NMS
See NetWare Management System.



nn
(NetNews)  A newsreader for reading the messages in
a newsgroup on the Internet.  See USENET.



no-op
(NO OPeration)  An instruction that does nothing
but hold the place for a future machine
instruction.



no wait state memory
Memory fast enough to meet the demands of the CPU.
Idle wait states do not have to be introduced.



node
(1) In communications, a network junction or
connection point (terminal or computer).

(2) In database management, an item of data that
can be accessed by two or more routes.

(3) In computer graphics, an endpoint of a
graphical element.

(4) In symmetric multiprocessing (SMP), a single
processing unit.  It includes a shared memory,
shared I/O and all the CPUs connected to it.



noise
An extraneous signal that invades an electrical
transmission.  It can come from strong electrical
or magnetic signals in nearby lines, from poorly
fitting electrical contacts, and from power line
spikes.



NOMAD
A relational DBMS from Must Software International,
Norwalk, CT, that runs on IBM mainframes, PCs and
VAXs.  Introduced in the mid 1970s, it was one of
the first database systems to provide a non-
procedural language for data manipulation.



NOMDA
(National Office Machine Dealers Association)  An
association that merged with LANDA to become the
Business Technology Association.  See BTA.



non-blocking
The ability of a signal to reach its destination
without interference or delay.



non-breaking space
See hard space.



non-document mode
A word processing mode used for creating source
language programs, batch files and other text files
that contain only text and no proprietary headers
and format codes.  All text editors, as well as
XyWrite word processors, automatically output this
format.



non-impact printer
A printer that prints without banging a ribbon onto
paper, such as a thermal or ink jet printer.  See
printer.



non-interlaced
Illuminating a CRT by displaying lines sequentially
from top to bottom.  Non-interlaced monitors
eliminate annoying flicker found in interlaced
monitors, which illuminate half the lines in the
screen in the first cycle and the remaining half in
the second cycle.  Contrast with and see interlaced
for a diagram.



non-modal
Not mode oriented.  A non-modal operation moves
from one situation to another without apparent mode
switching.



non-numeric programming
Programming that deals with objects, such as words,
board game pieces and people, rather than numbers.
Same as list processing.



non-preemptive multitasking
A multitasking environment in which an application
is able to give up control of the CPU to another
application only at certain points, such as when it
is ready to accept input from the keyboard.  Under
this method, one program performing a large number
of calculations for example, can dominate the
machine and cause other applications to have
limited access to the CPU.

   Non-preemtive multitasking is also called
cooperative multitasking, because programs must be
designed to cooperate with each other in order to
work together effectively in this environment.

   A non-preemtive multitasking operating system
cannot guarantee service to a communications
program running in the background.  If another
application has usurped the CPU, the CPU cannot
process the interrupts from the communications
program quickly enough to capture the incoming
data, and data can be lost.  Contrast with
preemptive multitasking.



non-procedural language
A computer language that does not require
traditional programming logic to be stated.  For
example, a command, such as LIST, might display all
the records in a file on screen, separating fields
with a blank space.  In a procedural language, such
as COBOL, all the logic for inputting each record,
testing for end of file and formatting the screen
has to be explicitly programmed.

   Query languages, report writers, interactive
database programs, spreadsheets and application
generators provide non-procedural languages for
user operation.  Contrast with and see procedural
language for an example.



non-return-to-zero
See NRZ.



non-routable protocol
A communications protocol that contains only a
device address and not a network address.  It does
not incorporate an addressing scheme for sending
data from one network to another.  Examples of non-
routable protocols are NetBIOS and DEC's LAT
protocols.  Contrast with routable protocol.



Non-system disk error or disk error
A DOS error message.  The full message is

    Non-system disk or disk error
    Replace and press any key when ready

This usually means there's a non-bootable floppy in
drive A.  The computer looks for DOS on a floppy
before it looks for DOS on the hard disk.  If an
ordinary floppy is in drive A at startup, it causes
this error.  Remove the disk and press any key.



non trivial
A favorite word used among programmers for any task
that isn't simple.



non-volatile memory
Memory that holds its content without power.
Firmware chips (ROMs, PROMs, EPROMs, etc.) are
examples.  Disks and tapes may be called non-
volatile memory, but they are usually considered
storage devices.



nonlinear
A system in which the output is not a uniform
relationship to the input.



nonlinear editing
See nonlinear video editing.



nonlinear video
See nonlinear video editing.



nonlinear video editing
Storing video in the computer for editing.  It is
much easier to edit video in the computer than with
earlier analog editing systems.  Today's digital
nonlinear editing systems provide high-quality
post-production editing on a personal computer.
However, lossy compression is used to store digital
images, and some detail will be lost.

   Depending on the purpose for the video
presentation, output is either the final video
turned back into analog or an edit decision list
(EDL) that describes frame sources and time codes
in order to quickly convert the original material
into the final video in an editing room.  For
commercial production, the latter allows editing to
be done offline rather than in a studio that costs
several hundred dollars per hour.

   Prior to digital, a system using several analog
tape decks was considered a nonlinear video editing
system.  Contrast with linear video editing.



nonmaskable interrupt
See NMI.



nonpreemptive multitasking
See non-preemptive multitasking.



NonStop
Tandem's trade name for its fault-tolerant computer
systems.



NOR
(Not OR)  A Boolean logical operation that is true
if all inputs are false, and false if any input is
true.  An exclusive NOR is true if both inputs are
the same.

           NOR           EXCLUSIVE NOR
      Inputs  Output    Inputs  Output
      Ŀ   Ŀ
       0   0   1      0   0   1  
       0   1   0      0   1   0  
       1   0   0      1   0   0  
       1   1   0      1   1   1  
         





normal wear
Deterioration due to natural forces that act upon a
product under average, everyday use.



normalization
In relational database management, a process which
breaks down data into record groups for efficient
processing.  There are six stages.  By the third
stage (third normal form), data is identified only
by the key field in the record.  For example,
ordering information is identified by order number,
customer information, by customer number.



Northgate
(Northgate Computer Systems, Inc., Eden Prarie, MN)
A PC manufacturer founded in 1987 by Arthur Lazere
that is known for its high-end systems and
keyboards.  Its PCs are sold mostly through direct
marketing, but its highly-praised line of OmniKey
keyboards is also sold through dealers.



Norton Desktop
Popular shells for DOS and Windows from Symantec.
They include a comprehensive package of utilities
and provide a large amount of customizability.



Norton SI
(Norton System Information)  A Norton utility that
measures computer performance.  It provides a
computing index (CI) for CPU speed, a disk index
(DI) for disk speed and a performance index (PI)
that blends CI and DI.  The IBM XT is used as a
reference of 1.0.



Norton Utilities
Widely-used utility programs for the PC and
Macintosh from Symantec Corporation, Cupertino, CA.
It includes programs to search, edit and undelete
files, to restore damaged files and to defragment
the disk, plus more.  Originally from Peter Norton
Computing, these programs were among the first to
popularize disk utilities for the PC.



NOS
See network operating system.



NOS/VE
(Network Operating System/Virtual Environment)  A
multitasking, virtual memory operating system from
Control Data that runs on its medium to large-scale
mainframes.



NOT
A Boolean logic operation that reverses the input.
If a 0 is input, a 1 is output, and vice versa.
See AND, OR & NOT.



Not ready error reading drive x
A DOS error message.  The full message is

    Not ready reading drive x
    Abort, Retry, Fail?

This means the drive door is left open, or the
floppy disk is not in the drive.  Either put the
appropriate floppy disk in the drive or close the
drive door (turn lever) and press R.

   To switch to another drive, press F, and type in
the drive letter you want to go back to when you
get the "Current drive is no longer valid>"
message.  In DOS versions prior to 4.0, type I for
Ignore rather than F for Fail.



Not ready writing device PRN
A DOS error message.  The full message is

    Not ready writing device PRN
    Abort, Retry, Fail?

This means the printer is turned off or
unavailable.  Press A to cancel, or turn the
printer on and press R.  You might also check the
cable connection to the printer.



Nota Bene
See XyWrite.



notation
How a system of numbers, phrases, words or
quantities is written or expressed.  Positional
notation is the location and value of digits in a
numbering system, such as the decimal or binary
system.



notebook computer
A laptop computer that weighs from approximately
five to seven pounds.  A notebook that weighs under
five pounds is usually called a subnotebook.  For
features of a portable computer, see laptop
computer.



Notes
See Lotus Notes.



Nova
A minicomputer series from Data General.  When
introduced in 1969, it was the first 16-bit mini to
use four CPU accumulators, quite advanced for its
time.  Novas and its RDOS operating system were
used extensively in the OEM marketplace.



NovaNET
A satellite-based network for educational services
created by the Education Research Lab of the
University of Illinois.  It includes over 10,000
hours of lesson material from third grade to post
graduate work in over a hundred subject areas.



Novell
(Novell Inc., Provo, UT)  Novell was founded as
Novell Data Systems in 1981 by Jack Davis and
Geroge Canova.  It initially manufactured terminals
for IBM mainframes.  In 1983, Ray Noorda became CEO
and president of a restructured Novell, Inc., which
would concentrate on the development of its NetWare
operating system.  NetWare has grown into the most
widely used network operating system in the world.

   Novell has recently become heavily involved with
UNIX.  First by creating Univel, a joint venture
with USL, AT&T's UNIX subsidiary, and second by
acquiring USL in its entirety in 1993.



Novell DOS
A DOS-compatible operating system from Novell.
Formerly DR DOS from Digital Research, Novell
acquired the company in 1991 and revamped the
product.  The first release under Novell DOS 7,
introduced in 1994, includes new utilities, built-
in NetWare client support, peer-to-peer networking,
preemptive multitasking and the ability to store
drivers in extended memory.

   Novell is expected to not introduce future
versions of the product.



Novell network
A LAN controlled by one of Novell's NetWare
operating systems.  See NetWare.



nroff
(Nontypesetting RunOFF)  A UNIX utility that
formats documents for terminals and dot matrix
printers.  Using a text editor, troff codes are
embedded into the text and the nroff command
converts the document into the required output.
Complex troff codes are ignored.  See troff.



NRZ
(Non-Return-To-Zero)  A signalling method used in
magnetic recording and communications that does not
automatically return to a neutral state after each
bit is transmitted.



ns
(NanoSecond)  See nanosecond.



NSTL
(National Software Testing Lab, Philadelphia)  An
independent organization that evaluates computer
hardware and software.  It adheres to controlled
testing methods to ensure objective results and
publishes its findings in Software Digest Ratings
Report and PC Digest.



NT
See Windows NT.



NT File System
See NTFS.



NTAS
(NT Advanced Server)  The server version of Windows
NT.  See Windows NT.



NTFS
(NT File System)  A file system used in Windows NT
which uses the Unicode character set and allows
file names up to 255 characters in length.  The
NTFS is designed to recover on the fly from hard
disk crashes.  Windows NT supports multiple file
systems.  It can run with a DOS FAT, an OS/2 HPFS
and a native NTFS, each in a different partition on
the hard disk.  NT's security features require that
the NTFS be used.



NTSC
(National TV Standards Committee)  The U.S. colored
TV standard administered by the FCC.  It currently
broadcasts at 525 lines of resolution that are
transmitted as 30 interlaced frames per second (60
half frames per second, or 60 "fields" per second
in TV jargon).  It is a composite of red, green and
blue signals for color and includes an FM frequency
for audio and an MTS signal for stereo.

   The NTSC will reconvene in order to change TV
standards.  See HDTV.  Contrast with the European
PAL color TV standard at 625 lines of resolution
and SECAM at 819 lines.



NuBus
A bus architecture (32-bits) originally developed
at MIT and defined as a Eurocard (9U).  Apple has
changed its electrical and physical specs for its
Macintosh series.  Many Macs have one or more NuBus
slots for peripheral expansion.



NUI
(1) (Notebook User Interface)  A term coined by Go
Corporation for its PenPoint pen-based interface.

(2) (NetWare Users International)  A voluntary
organization of more than 250 NetWare user groups
worldwide.  For information, call 800/228-4NUI
within the U.S. or 801/429-7000 outside the U.S.
and ask for NUI.

(3) (Network User Identifier)  A code used to gain
access into local European packed-switched
networks.



NUL
See null.



null
The first character in ASCII and EBCDIC.  In hex,
it prints as 00; in decimal, it prints as a blank.
It is naturally found in binary numbers when a byte
contains no 1 bits.  It is also used to pad fields
and act as a delimiter; for example, in C, it
specifies the end of a character string.



null modem cable
An RS-232 cable used to connect two personal
computers in close proximity.  It connects to both
serial ports and crosses the sending wire on one
end to the receiving wire on the other.



null pointer
In programming, a reference to zero.  May be the
response of an unsuccessful search function.



null string
In programming, a character string that contains no
data.



Num Lock
(NUMeric Lock)  A keyboard key used to toggle a
combination number/cursor keypad between number
keys and cursor keys.



Number 9 board
A family of high-resolution display boards for PCs
from Number Nine Computer Corporation, Lexington,
MA, noted for its advanced features (virtual
screen, built-in zoom, etc.) and speed.  Products
begin with #9, such as #9GXi and #9GXe.



number crunching
Refers to computers running mathematical,
scientific or CAD applications, which perform large
amounts of calculations.



numbers
In a computer, numbers can be stored in several
forms.  Although they are all coded as binary
digits (bits), BCD and packed decimal numbers
retain the decimal relationship of a number,
whereas fixed and floating point do not.


            Binary Coded Decimal (BCD)
BCD encodes each decimal digit in a single byte.
The number 6508 would take four bytes.  A
variation, called packed decimal, encodes two
digits in one byte.  6508 would take two bytes.


         Decimal      Packed Decimal
      Ŀ       Ŀ
       6 5 0 8       6508
             
      Ŀ    Ŀ
             6508           650800
          
       Fixed Point      Floating Point


                Binary Fixed Point
This method converts the entire decimal number into
a binary number, placing it in a fixed unit of
storage.  The number 6508 would require at least
two bytes.  Binary numbers are calculated faster
than decimal (BCD) numbers.

        Bytes  Bits   Values
          1     8     0 to 255
          2    16     0 to 65,535
          4    32     0 to 4,294,967,295


               Binary Floating Point
Floating point allows very small fractions and very
large numbers to be maintained and calculated
quickly.  Both the mantissa (significant digits)
and the exponent (power to which the base is
raised) are converted into binary numbers.  See
floating point.



numeric data
Refers to quantities and money amounts used in
calculations.  Contrast with string or character
data.



numeric field
A data field that holds only numbers to be
calculated.  Contrast with character field.



numeric keypad
A four-row keyboard.

   Calculator   Telephone
      789          123
      456          456
      123          789
       0            0




numerical aperture
The amount of light that can be coupled to an
optical fiber.  The greater the aperture, the
easier it is to connect the light source to the
fiber.



numerical control
A category of automated machine tools, such as
drills and lathes, that operate from instructions
in a program.  Numerical control (NC) machines are
used in manufacturing tasks, such as milling,
turning, punching and drilling.

   First-generation machines were hardwired to
perform specific tasks or programmed in a very low-
level machine language.  Today, they are controlled
by their own microcomputers and programmed in high-
level languages, such as APT and COMPACT II, which
automatically generate the tool path (physical
motions required to perform the operation).

   The term was coined in the 1950s when the
instructions to the tool were numeric codes.  Just
like the computer industry, symbolic languages were
soon developed, but the original term remained.



Nx586
A family of Pentium-class CPUs from NexGen, Inc.,
Milpitas, CA.  The P100, P90, P80 and P75 chips
provide 93MHz, 84MHz, 75MHz and 70MHz speeds
respectively.  Nx586 chips are designed with two
internal 16KB caches.  The math coprocessor is an
external option.



NxN switch
See crosspoint switch.



NZ
(Non Zero)  A value greater or less than 0.



OA
See office automation.



OADG
(Open Architecture Development Group)  An
organization founded by IBM Japan in 1991 to
promote PC standards in Japan.  See DOS/V.



OAI
(Open Application Interface)  A computer to
telephone interface that lets a computer control
and customize PBX and ACD operations.



object
(1) In object-oriented programming, a self-
contained module of data and its associated
processing.  Objects are software building blocks.
See objects and object-oriented programming.

(2) In a compound document, an independent block of
data, text or graphics that was created by a
separate application.



object code
Same as machine language.



object computer
Same as target computer.



object database
See object-oriented database.



Object Database Management Group
An organization formed in 1991 to promote standards
for object databases.  The ODMG-93 is a standard
that defines the message structure between objects.
See CORBA.



object language
(1) A language defined by a metalanguage.

(2) An object-oriented programming language.

(3) Same as machine language or target language.



Object Linking and Embedding
See OLE.



Object Management Group
An international organization founded in 1989 to
endorse technologies as open standards for object-
oriented applications.  Address: 492 Old
Connecticut Path, Framingham, MA 01701, 508/820-
4300.



object module
The output of an assembler or compiler, which must
be linked with other modules before it can be
executed.



object oriented
See objects.



object-oriented analysis
The examination of a problem by modeling it as a
group of interacting objects.  An object is defined
by its class, data elements and behavior.  For
example; in an order processing system, an invoice
is a class, and printing, viewing and totalling are
examples of its behavior.   Objects (individual
invoices) inherit this behavior and combine it with
their own data elements.



object-oriented database
A database that holds abstract data types (objects)
and is managed by an object-oriented database
management system (DBMS).  See object-oriented
DBMS.



object-oriented DBMS
A database management system (DBMS) that manages
objects (abstract data types).  An object-oriented
DBMS, or ODBMS, is suited for multimedia
applications as well as data with complex
relationships that are difficult to model and
process in a relational DBMS.  Because any type of
data can be stored (the rules for processing the
data are part of an object), an ODBMS allows for
fully integrated databases that hold data, text,
pictures, voice and video.

   Objects can point to actual data physically
located outside of the object database as
independent files, such as graphics and video files
on a hard disk or CD-ROM for example.  This
inherent object flexibility lets an ODBMS function
as a master repository (information about
information) for the enterprise.

   Relational DBMSs are primarily designed to
handle numbers, alphanumeric text and dates.  They
may also support a BLOB field, which holds any
binary data, but the routine to handle that BLOB
must be written into or called for by the
application that accesses the database.

   In an object database, a picture or video clip
may take the form of an object that literally says
"go get that picture file and go run this routine
to display it."  The application is not responsible
for each new type of format and its associated
processing.  The methods, or processing, in the
object dynamically invoke the necessary procedures
to handle that type of data.  This provides
flexibility in an ever-changing world of formats
and interfaces.

   In addition, a BLOB field doesn't support a 10-
megabyte video clip all that well, which an object
database can handle with ease, because it's simply
pointing to it.

   Some ODBMSs are purely object oriented and are
accessed from an application program written in an
object-oriented programming language.  Many allow
access via an SQL-like language or derivative,
while others combine relational and object
orientation in a unified product.

   Examples of ODBMSs are Servio Corporation's
Gemstone, Object Design's Object Store, Ontos'
ONTOS DB, HP's Open ODB and UniSQL's UniSQL/X.



object-oriented design
Transforming an object-oriented model into the
specifications required to create the system.
Moving from object-oriented analysis to object-
oriented design is accomplished by expanding the
model into more and more detail.



object-oriented graphics
Same as vector graphics.



object-oriented interface
A graphical interface that uses icons and a mouse,
such as Mac, Windows and Motif.



object-oriented operating system
An operating system that is based on objects.



object-oriented programming
Abbreviated "OOP," a programming technology that is
more flexible than standard programming.  It is an
evolutionary form of modular programming with more
formal rules that allow pieces of software to be
reused and interchanged between programs.  Major
concepts are (1) encapsulation, (2) inheritance,
and (3) polymorphism.

   Encapsulation is the creation of self-sufficient
modules that contain the data and the processing
(data structure and functions that manipulate that
data).  These user-defined, or abstract, data types
are called classes.  One instance of a class is
called an object.

   Classes are created in hierarchies, and
inheritance allows the knowledge in one class to be
passed down the hierarchy.  New objects can be
created by inheriting characteristics from existing
classes. For example, the object MACINTOSH could be
one instance of the class PERSONAL COMPUTER, which
could inherit properties from the class COMPUTER
SYSTEMS.  Adding a new computer requires entering
only what makes it different from other computers,
while the general characteristics of personal
computers can be inherited.

   Object-oriented programming allows procedures
about objects to be created whose exact type is not
known until runtime.  For example, a screen cursor
may change its shape from an arrow to a line
depending on the program mode.  The routine to move
the cursor on screen in response to mouse movement
would be written for "cursor," and polymorphism
would allow that cursor to be whatever shape is
required at runtime.  It would also allow a new
shape to be easily integrated into the program.

   Xerox's Smalltalk was the first OOP language and
was used to create the graphical user interface
whose derivations are so popular today.  C++ is
becoming the mainstay OOP language, because it
combines traditional C programming with object-
oriented features.

   Following is a terminology comparison:

   Object-oriented   Traditional
   programming       programming

    class             data type + characteristics
    instance          variable
    instantiate       declare a variable
    method            processing code
    message           call
    object            data type + processing





object-oriented technology
A variety of disciplines that support object-
oriented programming, including object-oriented
analysis and object-oriented design.



Object Packager
A Windows utility that embeds a document as an icon
inside another document.  It is part of Windows'
OLE (object linking and embedding).  It also allows
objects created by non-OLE-compliant applications
to be embedded.  When the icon is double clicked,
the application that created it is opened to view
and edit it.  See OLE.



object program
A machine language program ready to run in a
particular operating environment.  It has been
assembled, or compiled, and link edited.



Object Request Broker
See ORB.



Object Studio
An object-oriented client/server development system
from Easel Corporation, Burlington, MA, that
supports Windows, OS/2 and various UNIX clients and
the major server databases.  Its Synchronicity
module is used to graphically design the business
object model (data and business logic) and generate
Enfin Smalltalk code.  A visual programming tool is
used to create the user interfaces.



Objective-C
An object-oriented C programming language from The
Stepstone Corporation that runs on PCs and popular
workstations.  It was the first commercial object-
oriented extension of the C language.



objects
Software routines designed according to a set of
rules that allows them to function as independent
building blocks that interact with each other.
This architecture is expected to be revolutionary
in payback if meaningful standards become widely
used across all environments and platforms.

   Just as hardware components are routinely
designed as modules to plug into and work with each
other, objects are software components designed to
work together no matter which source language they
were originally developed in.  See object-oriented
programming.



ObjectView
A Windows-based client/server application
development software from Sterling Software,
Atlanta, GA (formerly KnowledgeWare).  ObjectView
applications can access multiple databases of
varying types, including Oracle and Sybase.
Business graphics and spreadsheet capabilities can
be included.



ObjectVision
Application development software from Borland for
creating Windows and OS/2 2.0 applications.  Uses
visual techniques for user interface design as well
as for programming logic.  It also provides links
to spreadsheets and databases.



ObjectWindows
A class library of Windows objects from Borland
that helps developers create Windows applications.
It is an open standard available from Borland and
the Object Management Group.



OC-1, 3, etc.
See SONET.



OC1, 3, etc.
See SONET.



occam
A parallel processing language designed to handle
concurrent operations.  The INMOS Transputer
executes occam almost directly.  In the following
statements, two items of data are read and
incremented at the same time.  PAR specifies that
following statements are to be executed
concurrently, and SEQ indicates that the following
statements are executed sequentially.

   PAR
    SEQ
      chan1 ? item1
      item1 := item1 + 1
    SEQ
      chan2 ? item2
      item2 := item2 + 1





OCE
See AOCE.



OCR
(Optical Character Recognition)  Machine
recognition of printed characters.  OCR systems can
recognize many different OCR fonts, as well as
typewriter and computer-printed characters.
Advanced OCR systems can recognize hand printing.



octal
A numbering system that uses eight digits.  It is
used as a shorthand method for representing binary
characters that use six-bits.  Each three bits
(half a character) is converted into a single octal
digit.   Okta is Greek for 8.  


   Decimal Binary  Octal
      0     000      0
      1     001      1
      2     010      2
      3     011      3
      4     100      4
      5     101      5
      6     110      6
      7     111      7





octet
An eight-bit storage unit.  In the international
community, octet is often used instead of byte.



ODAPI
(Open Data API)  A database programming interface
from Borland that was rewritten and turned into the
IDAPI interface.  See Borland Database Engine.



ODBC
(Open DataBase Connectivity)  A database
programming interface from Microsoft that provides
a common language for Windows applications to
access databases on a network.  It is part of
Microsoft's WOSA strategy.  ODBC is a superset of
the SQL Access Group's Call Level Interface (CLI).



ODBMS
See object-oriented DBMS.



odd parity
See parity checking.



ODI
(Open Data-Link Interface)  A network driver
interface from Novell.  ODI is based on the LSL
interface developed by AT&T for its UNIX System V
operating system.  See network driver interface and
LSL.



ODMG
See Object Database Management Group.



ODT
See SCO Open Desktop.



Oe
See Oersted.



OEM
(Original Equipment Manufacturer)  A manufacturer
that sells equipment to a reseller.  Also refers to
the reseller itself.  OEM customers either add
value to the product before reselling it, private
label it, or bundle it with their own products.
See VAR.



OEM font
In Windows, the font used to replicate the
monospaced characters of a DOS application, when
DOS text has been copied to the clipboard or a DOS
character mode application is running in a Windows
window.



Oersted
Pronounced "ers-ted," the measurement of magnetic
resistance.  The higher the "Oe," the more current
required to magnetize it.



off-hook
The state of a telephone line that allows dialing
and transmission but prohibits incoming calls from
being answered.  The term stems from the days when
a telephone handset was lifted off of a hook.
Contrast with on-hook.



off-line
See offline.



off-the-shelf
Refers to products that are packaged and available
for sale.



office automation
The integration of office information functions,
including word processing, data processing,
graphics, desktop publishing and e-mail.

   The backbone of office automation is a LAN,
which allows users to transmit data, mail and even
voice across the network.  All office functions,
including dictation, typing, filing, copying, fax,
Telex, microfilm and records management, telephone
and telephone switchboard operations, are
candidates for integration.



Office Vision
Integrated office automation applications from IBM
that run in all IBM computer families.  It was the
first major implementation of SAA and incorporates
the Presentation Manager interface across OS/2
networks, AS/400s and mainframes.

   Introduced in 1989, it includes e-mail,
scheduling, document creation and distribution as
well as decision support and graphics capabilities
among all users.



OfficeJet
A combination ink jet printer, copier and fax
machine from Hewlett-Packard Company.  Introduced
in 1994, this first combo unit from HP is two
separate devices in one box: a computer printer and
fax machine.  There is no way to fax from or to the
computer.  Its copy facility allows for reductions
of up to 70%.



offline
Not connected to or not installed in the computer.
If a terminal, printer or other device is
physically connected to the computer, but is not
turned on or in ready mode, it is still considered
offline.

   Disks and tapes that have been demounted and
stored in the data library are considered offline.
Contrast with online.



offline browser
See offline reader.



offline navigator
See offline reader.



offline reader
Software that downloads e-mail and selected data
from an online service, allowing the user to browse
the captured material after disconnecting.  It
automates retrieving routine data and saves online
fees by shortening the connect time.



offline storage
Disks and tapes that are kept in a data library.



offload
To remove work from one computer and do it on
another.  See cooperative processing.



offset
(1) The distance from a starting point, either the
start of a file or the start of a memory address.
Its value is added to a base value to derive the
actual value.  An offset into a file is simply the
character location within that file, usually
starting with 0; thus "offset 240" is actually the
241st byte of the file.  See relative address.

(2) In word processing, the amount of space a
document is printed from the left margin.



OH
See off-hook and modem.



ohm
A unit of measurement for electrical resistance.
One ohm is the resistance in a circuit when one
volt maintains a current of one amp.



OLAP database
(OnLine Analytical Processing database)  A database
designed for fast access to summarized data.  Using
specialized indexing techniques, it processes
queries that pertain to large amounts of data and
multidimensional views of data much faster than
traditional relational databases.  See EIS.



olay
See OLE.



OLCP
(OnLine Complex Processing)  Processing complex
queries, long transactions and simultaneous reads
and writes to the same record.  Contrast with OLTP,
in which records are updated in a more predictable
manner.



OLE
(Object Linking and Embedding)  Windows' compound
document protocol that allows one document to be
embedded within or linked to another.  When an
object (document, drawing, sound, etc.) that is
embedded is clicked, the application that created
it is loaded so that you can edit it.  Changes made
to the embedded object affect only the document
that contains it.

   If an object is linked rather than embedded, it
references an original file outside of the
document.  Thus, if you make a change to a linked
object, all the documents that contain that link
are automatically updated the next time you open
them.

   The application that creates the document that
holds an embedded object is called the "client"
application.  The application that creates the
object for embedding is called the "server"
application.  An application can also be both
client and server.  See Object Packager.



OLR
See offline reader.



OLTP
(OnLine Transaction Processing)  See transaction
processing and OLCP.



OME
(Open Messaging Environment)  An open messaging
system from Novell.  It is based on Microsoft's
MAPI and is a superset of Novell's MHS and
WordPerfect Office's messaging systems.



OMG
See Object Management Group.



OMI
(Open Messaging Interface)  A messaging protocol
developed by Lotus, now included in VIM.



omnidirectional
In all directions.  For example, an omnidirectional
antenna can pick up signals in all directions.



OmniPage
Character recognition software for PCs and the
Macintosh from Caere Corporation, Los Gatos, CA.
It was the first personal computer software that
could distinguish text from graphics and convert a
wide variety of fonts into text.



OMNIS 7
A client/server development system for creating
Windows, Mac and PowerMac applications from Blyth
Software, Foster City, CA.  It includes its own
database manager for local and laptop use and
supports a wide variety of databases.  OMNIS
includes visual programming tools and a 4GL for
application development.  Client support for NT,
OS/2, Solaris, AIX and HP-UX is expected.



on-hook
The state of a telephone line that can receive an
incoming call.  Contrast with off-hook.



on-line
See online.



on the fly
As needed.  It implies little or no degradation in
performance to accomplish the task.  See realtime
and realtime compression.



ONA
(Open Network Architecture)  An FCC plan that
allows users and competing enhanced service
providers (ESPs) equal access to unbundled, basic
telephone services.  The Open Network Provision
(ONP) is the European counterpart.



ONC
(Open Network Computing)  A family of networking
products from SunSoft for implementing distributed
computing in a multivendor environment.  Includes
TCP/IP and OSI protocols, NFS distributed file
system, NIS naming service and TI-RPC remote
procedure call library.  ONC+ adds Federated
Services, which is an interface for third-parties
to connect network services into the Solaris
environment.



one-chip computer
See computer on a chip.



one-off
One at a time.  CD-ROM recorders (CD-R drives) are
commonly called one-off machines because they write
one CD-ROM at a time.



onion diagram
A graphical representation of a system that is made
up of concentric circles.  The innermost circle is
the core, and all outer layers are dependent on the
core.



online
(1) A peripheral device (terminal, printer, etc.)
that is ready to operate.  A printer can be
attached and turned on, yet still not online, if
the ONLINE or SEL light is out.  Pressing the
ONLINE button will usually turn it back online.

(2) An online computer system refers to a system
with terminals, but does not imply how the system
functions.  All the following are online systems.
Data collection systems accept data from terminals,
but do not update master files.  Interactive
systems imply data entry and updating.  Transaction
processing systems update necessary files as
transactions arrive (orders, financial quotes,
etc.).  Realtime systems provide an immediate
response to a question.

 Want to impress your friends?Ŀ
  Although complete overkill, it is not         
  incorrect to say that one has an online,      
  realtime, interactive, transaction processing 
  system.  However, don't say this to an        
  experienced systems analyst!                  
 





online complex processing
See OLCP.



online help
On-screen instruction that is immediately
available.



online industry
The collection of service organizations that
provide dial-up access to databases, shopping,
news, weather, sports, e-mail, etc.  See online
services.



online services
Following are major online information service
organizations, including the types of databases
provided.  "Wide variety" generally includes news,
weather and shopping as well as information on a
host of topics.  Most services provide e-mail and
many provide access to e-mail and news groups on
the Internet.  Full Internet access is expected on
many services in the future.


 America Online, Inc.
 Databases: wide variety, personal computer
 technical
  8619 Westwood Center Dr.
  Vienna, VA 22182
  800/827-6364
  703/448-8700


 BIX
 Databases: personal computer technical
  Byte Information Exchange
  General Videotex Corporation
  1030 Massachusetts Ave.
  Cambridge, MA 02138
  800/695-4775
  617/491-3393


 CompuServe Information Service, Inc.
 Databases: wide variety, personal computer
 technical
  P.O. Box 20212
  Columbus, OH 43220
  800/848-8199 (Ohio)
  800/848-8990
  614/457-8650


 DataTimes Corporation
 Databases: newspapers, magazines, financial
  14000 Quail Springs Pkwy., Suite 450
  Oklahoma City, OK 73134
  800/642-2525
  405/751-6400


 Delphi
 Databases: wide variety, access to DIALOG,
 full Internet access
  News Corporation
  1030 Massachusetts Ave.
  Cambridge, MA 02138
  800/544-4005
  617/491-3393


 DIALOG Information Services, Inc.
 Databases: over 400 (largest)
  3460 Hillview Avenue
  Palo Alto, CA 94304
  800/334-2564
  415/858-2700


 Dow Jones News/Retrieval Service
 Databases: financial plus shopping
 airline reservations, etc.
  P.O. Box 300
  Princeton, NJ 08543
  800/522-3567
  609/520-4000


 EasyLink
 Services: e-mail, Telex, EDI
 Databases: access to major providers (DIALOG,
 CompuServe, etc.)
  AT&T EasyLink Services
  400 Interpace Pkwy.
  Parsippany, NJ 07054
  800/242-6005
  201/331-4000


 GEnie
 Databases: wide variety
  General Electric Information Services Co.
  401 N. Washington St.
  Rockville, MD 20850
  800/638-9636
  301/340-4000


 Mead Data Central
 Databases: news (NEXIS), legal (LEXIS)
  P.O. Box 933
  Dayton, OH 45401
  800/227-4908
  513/865-6800


 Maxwell Online
 Databases: medical (BRS),
 patent, trademark (ORBIT)
  8000 Westpark Dr.
  McClean, VA 22102
  ORBIT 800/456-7248
  BRS 800/289-4277


 MEDLARS
 Databases: medical
  National Library of Medicine
  8600 Rockville Pike
  Bethesda, MD 20894
  800/638-8480
  301/496-6193


 MCI Mail
 Services: e-mail, Telex, fax
 Databases: access to Dow Jones
  1133 19th St., NW
  Washington, DC 20036
  800/444-6245
  202/833-8484


 National Videotex Network
 Databases: wide variety
  5555 San Felipe, Suite 1200
  Houston, TX 77056
  800/336-9096
  713/877-4444


 NewsNet, Inc.
 Databases: newsletters
  945 Haverford Rd.
  Bryn Mawr, PA 19010
  800/952-0122
  215/527-8030


 PRODIGY
 Databases: wide variety, shopping
  445 Hamilton Ave.
  White Plains, NY 10601
  800/776-3449
  914/993-8848


 VU/TEXT Information Services, Inc.
 Databases: newspapers
  325 Chestnut St., Suite 1300
  Philadelphia, PA 19106
  800/323-2940
  215/574-4400


 WESTLAW
 Databases: legal (plus access to
 DIALOG and Dow Jones)
  West Publishing Co.
  610 Opperman Dr.
  St. Paul, MN 55123
  800/WESTLAW
  612/687-7000


 ZiffNet
 Databases: personal computer (technical,
 news, shopping)
  25 First St.
  Cambridge, MA 02141
  800/666-0330
  617/252-5000





online transaction processing
See transaction processing and OLCP.



OO
Object oriented.



OOA
See object-oriented analysis.



OOD
See object-oriented design.



OODB
See object-oriented database.



OODBMS
See object-oriented DBMS.



OOOS
See object-oriented operating system.



OOP
See object-oriented programming.



OOPL
(OOP Language)  An object-oriented programming
language.



OOPS
(Object-Oriented Programming System)  See object-
oriented programming.



OORDBMS
(Object-Oriented Relational DBMS)  A relational
database management system that has object-oriented
capabilities.



OOT
(Object-Oriented Technology)  See objects and
object-oriented programming.



op amp
(Operational Amplifier)  A device that amplifies
analog signals.  It uses two inputs; one for power
and one for data.  It is used in myriads of
applications from communications to stereo.



op code
See operation code.



open
(1) To identify a disk or tape file for reading and
writing.  The open procedure "locks on" to an
existing file or creates a new one.

(2) With regard to a switch, open is "off."

(3) Made to operate with other products.  See open
architecture and open systems.



open architecture
A system in which the specifications are made
public in order to encourage third-party vendors to
develop add-on products.  Much of Apple's early
success was due to the Apple II's open
architecture.  The PC is open architecture.



open computing
See open systems.



Open Data-link Interface
See ODI.



Open Database Connectivity
See ODBC.



Open Desktop
See SCO Open Desktop.



open file
A file, typically a disk file, that has been made
available to the application by the operating
system for reading and/or writing.  All files must
be "opened" before they can be accessed and
"closed" when no longer required.



OPEN LOOK
An X Window-based graphical user interface for UNIX
developed by Sun.  It has been widely used by Sun
and was defined and distributed by AT&T when it was
still involved with UNIX.  OPEN LOOK is giving way
to Motif, which has become the standard user
interface in the UNIX world.



Open Messaging Environment
See OME.



Open Network Computing
See ONC.



open pipe
A continuous path from sender to receiver, such as
found in a circuit-switching network or leased
line.  Transmitted data is not broken up into
packets.



open shop
A computing environment that allows users to
program and run their own programs.  Contrast with
closed shop.



Open Software Foundation
See OSF.



open system
A vendor-independent system that is designed to
interconnect with a variety of products.  It
implies that standards are determined from a
consensus of interested parties rather than one or
two vendors.

   Sometimes, the PC is called an open system, but
it is more an open architecture than an open
system, because Intel and Microsoft have strong
control over the hardware and system software.
Contrast with closed system.  See open systems,
OSI, OSF and X/Open.



Open System Interconnection
See OSI.



open systems
For years, open systems and UNIX-based computing
have been synonymous, because UNIX runs on more
different kinds of computers than any other
operating system.  The goal of open systems is
interoperability between hardware and software that
is defined by the industry at large and not one or
two vendors.

   Open systems includes database management
systems (DBMSs) that run on many different
platforms as well and any other tools that are used
cross platforms.  While this provides a certain
freedom for future changes, it is by no means a
problem free environment and never will be.
Whenever several hardware platforms are used, a
version of each software product must be available
for that platform.

   For example, in order to migrate an application
from one UNIX system to another, all the system
software components (DBMSs, TP monitors, compilers,
etc.) that are currently linked to that application
must also be available for the new system.
Otherwise, custom conversion programs must be
developed and more conversion effort is required.

   The goal of open systems is a beautiful one,
very much akin to world peace.  Everyone pledges
allegiance to it, but getting there seems to take
forever.



OpenDoc
A compound document architecture from Apple, IBM,
Novell, Sun and others that allows multiple data
structures (text, graphics, sound, etc.) to be
stored in a single document.

   OpenDoc supports small software modules, called
"part handlers" in addition to linking to full
applications.  For example, rather than requiring
the full application that created the text, a part
handler can be used to edit text in all documents
no matter how they were created.  The menus change
automatically as the cursor is moved onto different
parts of the document, activating the tools
required to edit it.

   OpenDoc refers to the data components in a
document as parts, whereas OLE calls them objects.
OpenDoc is a superset of OLE, and OLE objects can
be placed into OpenDoc documents.  Like OLE,
OpenDoc handles both embedded and linked document
segments.



OpenGL
(OPEN Graphics Language)  A 3-D graphics language
developed by Silicon Graphics and endorsed by a
variety of vendors.  Windows NT Version 3.5
supports OpenGL.



OpenMail
An electronic mail system from HP that runs on UNIX
servers.  It complies with the X.400 messaging and
X.500 directory standards and supports all major
mail programs that run on the client.



OpenStep
An operating system-independent object standard
that is based on NeXT's NEXTSTEP object-oriented
software.  It comprises the object layer within
NEXTSTEP that is separate and apart from the
kernel.  In 1995, OpenStep is expected to be
released in new versions of Sun, Digital and HP
operating systems.

   The goal of OpenStep is to create an open,
portable standard for object-oriented computing
that allows objects to be easily used in a
distributed, heterogeneous environment.



OpenView
Network management software from HP.  It supports
SNMP and CMIP protocols, and third-party products
that run under OpenView support SNA and DECnet
network management protocols.  OpenView is an
enterprise-wide network management solution.



OpenVMS
A version of the VMS operating system from Digital
that is POSIX and XPG3-compliant and runs on VAX
and Alpha systems.



operand
The part of a machine instruction that references
data or a peripheral device.  In the instruction,
ADD A to B, A and B are the operands (nouns), and
ADD is the operation code (verb).  In the
instruction READ TRACK 9, SECTOR 32, track and
sector are the operands.



operating system
The master control program that runs the computer.
It is the first program loaded when the computer is
turned on, and its main part, called the kernel,
resides in memory at all times.  It may be
developed by the vendor of the computer it's
running in or by a third party.

   It is an important component of the computer
system, because it sets the standards for the
application programs that run in it.  All programs
must "talk to" the operating system.

   The main difference between an operating system
and a network operating system is its multiuser
capability.  Operating systems, such as Macintosh
System 7, DOS and Windows, are single user,
designed for one person at a desktop computer.
Windows NT and UNIX on the other hand are network
operating systems, because they are designed to
manage multiple user requests at the same time.

   An operating system is also called an executive
or supervisor.  Operating systems perform the
following functions.


                  User Interface
The user interface, or shell, provides the
interaction between the user and the operating
system.  Operating systems may allow for different
shells; for example, DOS and UNIX provide command-
driven interfaces but can host other shells that
provide a menu-driven or graphical interface.  Even
Windows, which is graphics based to begin with,
allows other shells to provide an interface to the
user.

                  Job Management
Job management controls the running of programs.
Which one gets executed first, then next.  In small
computers, the operating system responds to
interactive commands from the user and loads the
requested application program into memory for
execution.  Larger computers are more oriented to
accepting a batch of instructions.  For example,
job control language (JCL) may describe the
programs that must be run for an entire shift.  In
some cases, the output of one program may then be
input into another and so on.


                  Task Management
Task management controls the simultaneous execution
of programs.  In single tasking computers, the
operating system has virtually no task management
to do, but in multitasking computers, it is
responsible for the concurrent operation of one or
more programs (jobs).  Advanced operating systems
have the ability to prioritize programs so that one
job gets done before the other.

   In order to provide users at terminals with the
fastest response time, batch programs can be put on
lowest priority and interactive programs can be
given highest priority.  Advanced operating systems
can be fine tuned by the computer operator so that
a specific job can be speeded up or slowed down.

   Multitasking is accomplished by executing
instructions for one function while data is coming
into or going out of the computer for another.
Large computers are designed to overlap these
operations, and data can move simultaneously in and
out of the computer through separate channels with
the operating system governing these actions.

   In small computers, the operating system can
monitor idle time when a user is interactively
working with a program to execute another program
in the background.  Even the milliseconds between
keystrokes can be used for something else.  A user,
pausing at the keyboard for just a couple of
seconds, is light years to the computer, which can
use that time to execute hundreds of thousands of
instructions.


                  Data Management
Data management keeps track of data on the disk;
hence the term DOS, or disk operating system.  The
application program does not know where the data is
actually stored or how to get it.  That knowledge
is contained in the operating system's access
method, or device driver, routines.  When a program
is ready to accept data, it signals the operating
system with a message.  The operating system finds
the data and delivers it to the program.
Conversely, when the program is ready to output,
the operating system transfers the data from the
program onto the available space on disk.


                 Device Management
Device management controls the input and output of
data to and from the peripheral devices.  In
theory, the operating system is supposed to manage
all devices, not just disk drives.  It is supposed
to handle the input and output to the display
screen as well as the printer.  By keeping the
details of the peripheral device within the
operating system, a device can be replaced with a
newer model, and only the routine in the operating
system that deals with that device needs to be
replaced.

   In the DOS world, software developers often
bypassed the operating system, because DOS either
did not support the device or added too much
performance overhead.  Developers of graphics, word
processing and desktop publishing applications were
made responsible for providing drivers (routines)
for all the popular displays and printers, adding
an enormous burden to their development efforts.

   This is a major reason why Windows, which
provides device management for all peripherals,
became so popular.


                     Security
Multiuser operating systems maintain a list of
authorized users and provide password protection to
unauthorized users who may try to gain access to
the system.  Large operating systems also maintain
activity logs and accounting of the user's time for
billing purposes.  They also provide backup and
recovery routines to start over again in the event
of a system failure.


                      History
The earliest operating systems were developed in
the late 1950s to manage tape storage, but
programmers mostly wrote their own I/O routines.
In the mid 1960s, operating systems became
essential to manage disks, complex timesharing and
multitasking systems.

   Today, all multi-purpose computers from micro to
mainframe use an operating system.  Special-purpose
devices (appliances, games, toys, etc.) generally
do not.  They usually employ a single program that
performs all the required I/O and processing tasks.


             Common Operating Systems
PCs use DOS, Windows, OS/2, SCO XENIX and AIX (see
PC operating environments).  Windows is the most
popular operating environment for PCs, although it
is technically not a complete operating system
since it requires and interacts with DOS.  Windows
NT and Windows 95 are complete operating systems.

   The old Apple II's used the ProDOS operating
system.  The Macintoshes use System 7 as well as
A/UX, Apples UNIX version.  Digital's VAX series
uses VMS and ULTRIX (UNIX).  IBM mainframes use
MVS, VM and VSE.

   In the past, when a vendor introduced a new
operating system, users had little understanding of
this behind-the-glass-enclosed-datacenter
phenomenon.  Today, it is squarely in their hands.

   Perhaps the Japanese have the right idea with
their TRON operating system.  It is intended to be
a common interface across all applications from a
microwave oven to the largest supercomputer!

   The following diagram shows the interaction of
the operating system with other system and
application software running within the computer.


  to/from terminals (RAM)ͻ
 Ŀ   Ŀ   
  Comm.      TP Monitor (Multiuser)      
  Access        
  Methods       Ŀ Ŀ 
 Ĵ      Application Application  
                in COBOL or in DBMS's    
                other lang. own language 
                  
    OS    ......................... .......
          .Ŀ   Ŀ .
          .Interactive:     Interpreter .
          .enter, edit,      .
          .query, reports                .
 Ĵ.                .
  Disk    .  Ŀ.
  Access         Database manager       .
  Methods .  .
 ...............DBMS ................
  to/from disk ͼ

          System and Application Software
                Running in Memory





operation code
The part of a machine instruction that tells the
computer what to do, such as input, add or branch.
The operation code is the verb; the operands are
the nouns.



operations
See datacenter.



operations research
See management science.



operator
(1) A person who operates the computer and performs
such activities as commanding the operating system,
mounting disks and tapes and placing paper in the
printer.  Operators may also write the job control
language (JCL), which schedules the daily work for
the computer.

(2) In programming and logic, a symbol used to
perform an operation on some value.  See arithmetic
operator and Boolean operator.



operator overloading
In programming, the ability to use the same
operator to perform different operations.  For
example, arithmetic operators such as +, -, * and /
could be defined to perform differently on certain
kinds of data.



OPI
(Open Prepress Interface)  An extension to
PostScript by Aldus Corporation to provide a format
for color separations.



optical character recognition
See OCR.



optical disk
A direct access disk written and read by light.
CDs, CD-ROMs and videodiscs are optical disks that
are recorded at the time of manufacture and cannot
be erased.  WORM disks are recorded in the user's
environment, but cannot be erased.

   Erasable optical disks function like magnetic
disks and can be rewritten over and over.  In the
late 1980s, a variety of erasable optical disks
were introduced that use magneto-optic, dye polymer
and phase change recording technologies.

   Throughout the 1990s, erasable optical disks may
become a viable alternative to magnetic disks.
Optical disks have greater storage capacity per
square inch than their magnetic counterparts, and
optical technology will eventually replace magnetic
media.  Lasers can be moved electronically and, in
time, will be built into a new breed of non-
spinning storage device that will dramatically
impact future computers.



optical fiber
A thin glass wire designed for light transmission,
capable of transmitting billions of bits per
second.  Unlike electrical pulses, light pulses are
not affected by random radiation in the
environment.

   An optical fiber is constructed of a transparent
core made of pure silicon dioxide (SiO2), through
which the light travels.  This core is so
transparent that you could see through a three-mile
thick window made out of it.  The core is
surrounded by a cladding layer that reflects light,
keeping it in the core.  The cladding is surrounded
by a plastic layer, a layer of kevlar fibers for
strength and an outer sheath of plastic or Teflon.

   When the telephone companies eventually replace
the copper wire from their central stations into
everyone's home with optical fiber, all varieties
of information services will be interactively
available to the consumer.  In-ground optical
fibers may eventually eliminate the need for
satellite transmission.

   Multimode fiber is the most commonly used, which
has a core diameter of from 50 to 100 microns.  For
intercity cabling and highest speed, single-mode
fiber with a core diameter of less than 10 microns
is used.  See FDDI and cable categories.



optical isolator
A device used with current loop transmission that
uses an LED and photoresistor to detect current in
the line.



optical mouse
A mouse that uses light to get its bearings.  It is
rolled over a small desktop pad that contains a
reflective grid.  The mouse emits a light and
senses its reflection as it is moved.  Contrast
with mechanical mouse.



optical reader
An input device that recognizes typewritten or
printed characters and bar codes and converts them
into their corresponding digital codes.



optical recognition
See OCR.



optical scanner
See scanner.



optimizer
Hardware or software that improves performance.
See defragger and disk management.



optoelectronics
Merging light and electronics technologies, such as
in optical fiber communications systems.



OR
A Boolean logic operation that is true if any of
the inputs is true.  An exclusive OR is true if
only one of the inputs is true, but not both.

             OR           EXCLUSIVE OR
       Inputs  Output    Inputs  Output
      Ŀ   Ŀ
       0   0   0      0   0   0  
       0   1   1      0   1   1  
       1   0   1      1   0   1  
       1   1   1      1   1   0  
         





Oracle
(1) A relational database management system (DBMS)
from Oracle Corporation, Redwood Shores, CA, that
runs on a wide variety of computer platforms from
micro to mainframe.  Oracle was the first DBMS to
incorporate the SQL language and to run on a wide
variety of platforms.  As a result, it has been
very successful.  Applications can be developed
with Oracle's Cooperative Development Environment
(CDE), which includes a variety of tools for
client/server development.  See CDE.

(2) A European broadcast television text-message
service.


Oracle Browser
See CDE.



Oracle Data Query
See CDE.



Oracle Documents
A document database system from Oracle that is
expected in 1995.  Similar to Lotus Notes, it keeps
distributed documents in sync; however, Oracle
Documents is expected to be more comprehensive and
capable of managing any kind of file.



Oracle Forms
See CDE.



Oracle Media Server
An multimedia system for interactive TV delivery
from Oracle Corporation that runs on nCUBE, HP and
other hardware platforms.  The client software runs
on Macs, PCs and set-top boxes.  It is designed to
store and disseminate multiple streams of text
(news), images, audio and video on demand. 



Oracle Parallel Server
A version of the Oracle database system designed
for massively parallel processors (MPPs).  It
allows multiple CPUs to access a single database.



Oracle Reports
See CDE.



Orange Book
See NCSC and CD.



ORB
(Object Request Broker)  Software that handles the
communication of messages from the requesting
program (client) to the object as well as any
return values from the object back to the calling
program.  See CORBA.



ORB gateway
Software that translates messages between two
different ORBs.



Order Form
This database is updated quarterly.  To order the
next version for only $12.95, use the following
form.  Turn your printer on, move the dotted line
to the top of the text window and select PRINT from
the menu.  Mac users, select PRINT icon.

    License the Glossary for your networks
           And all stand-alone PCs.

   ADD YOUR OWN TERMS WITH MULTIUSER LICENSES!

    Number of users     License cost  Upgrades
         25                $125         $45
         50                 175          60
        100                 250          75
        250                 500         125
     Unlimited            1,000         250
     Unlimited national   5,000         750

              Call 215/297-5999.

.............................................
       THE COMPUTER LANGUAGE COMPANY INC.
            5521 State Park Road
          Point Pleasant, PA 18950

Name_______________________________________

Company____________________________________

Address____________________________________

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Telephone__________________________________

To qualify for $12.95 upgrade (full price $29.95),
include diskette serial number.  If pre-installed
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ordinal number
The number that identifies the sequence of an item,
for example, record #34.  Contrast with cardinal
number.



orientation
In typography, the direction of print across a
page.  See portrait.



original equipment manufacturer
See OEM.



orphan
See widow & orphan.



OS
See operating system.



OS/2
A single user, multitasking operating system for
PCs from IBM that runs OS/2, DOS and Windows
applications.  It provides both a graphical user
interface as well as a command line interface
similar to DOS.  Many OS/2 and DOS commands are the
same.

   The first versions of OS/2 were written for 286s
and were developed jointly by IBM and Microsoft.
Subsequent releases, starting with Version 2.0,
were written for 32-bit 386s and up and are solely
the product of IBM.  OS/2 is highly regarded as a
robust operating system, which prevents an errant
application from freezing the computer.

   OS/2's graphical user interface, called
Presentation Manager (PM) in Versions 1.x and
Workplace Shell, starting with Version 2.0, is
similar to Windows and the Macintosh.  The term
Presentation Manager however still refers to the
programming interface used to write OS/2 graphical
applications.

   OS/2 provides a dual boot feature.  When you
turn the computer on, you can boot either OS/2 or
DOS.  Included with OS/2 is Adobe Type Manager for
rendering Type 1 fonts on screen and providing
PostScript output on non-PostScript printers.


              OS/2 16-bit Version 1.x
The first versions (1.0, 1.1, etc.) were written
for the 16-bit 286.  DOS compatibility was limited
to about 500K.  Version 1.3 (OS/2 Lite) required
2MB RAM instead of 4MB and included Adobe Type
Manager.  IBM's Extended Edition version included
Communications Manager and Database Manager.


           OS/2 32-bit Version 2.x - IBM
Introduced in April 1992, this 32-bit version for
386s and up from IBM multitasks DOS, Windows and
OS/2 applications.  Data can be shared between
applications using the clipboard and between
Windows and PM apps using the DDE protocol.
Version 2.x provides each application with a 512MB
virtual address space, which allows huge tasks to
be easily managed.

   Version 2.1 supports Windows' Enhanced Mode and
applications that take full advantage of Windows
3.1.  It also provides support for more video
standards and CD-ROM drives than Version 2.0.

   Communications and database management for OS/2
are provided by Communications Manager/2 (CM/2) and
Database Manager/2 (DB2/2).  CM/2 replaces
Communications Manager, which was part of OS/2
2.0's Extended Services option.


            OS/2 32-bit Version 3 - IBM
In late 1994, IBM introduced Version 3 of OS/2,
known as OS/2 Warp.  It runs in only 4MB of memory
and includes a variety of full applications,
including Internet access.  See OS/2 Warp.


              Windows NT - Microsoft
Originally to be named OS/2 Version 3.0, this 32-
bit version from Microsoft was renamed Windows NT
and introduced in 1993.  Windows NT can run
character-based OS/2 applications; however, almost
all OS/2 applications use the graphical
Presentation Manager interface.  See Windows NT.



OS/2 for Windows
A special edition of OS/2 Version 2.1 for PCs that
already have DOS and Windows 3.1 installed.  It is
less expensive than the full OS/2, because it does
not include the Windows code.  This was superseded
by OS/2 Warp.



OS/2 PM
(OS/2 Presentation Manager)  The graphical user
interface in OS/2 Version 1.x.  It is now called
Workplace Shell in Versions 2.x.  See OS/2.



OS/2 Warp
Introduced in late 1994 and officially known as
OS/2 Warp, Version 3, it is the successor to OS/2
for Windows and OS/2 Version 2.1.  It is an
enhanced version that can run in only 4MB of
memory.  It includes a simpler installation,
improved multimedia support, Internet utilities and
access via IBM's Global Network and a variety of
bundled applications.  The applications include IBM
Works, a productivity suite, a fax program, PIM,
comm program and others.  The first release of the
product is for users that already have Windows 3.1
installed.  The second release is the full pack for
users that do not have Windows.



OS/400
The operating system designed for the AS/400
minicomputer from IBM.



OS/8
A single user, multitasking operating system from
Digital for its PDP-8 computers.  Variants run on
DECstation and DECmate systems.



OS/9
A UNIX-like, realtime operating system from
Microware Systems Corporation for Motorola 68000
CPUs.  Originally developed for the 6809 chip, a
version of OS/9 was created for CD-I players.



OS/9000
A portable version of OS/9, written in C, which
runs on 386s and up and 68020s and up.



oscillate
To swing back and forth between the minimum and
maximum values.  An oscillation is one cycle,
typically one complete wave in an alternating
frequency.



oscillator
An electronic circuit used to generate high-
frequency pulses.  See clock.



oscilloscope
Test instrument that displays electronic signals
(waves and pulses) on a screen.  It creates its own
time base against which signals can be measured,
and display frames can be frozen for visual
inspection.



OSF
(Open Software Foundation)  A non-profit
organization dedicated to delivering an open
computing environment based on standards.  Formed
in 1988, it solicits technologies from industry,
invites member participation to set technical
direction and licenses software to members.
Address: 11 Cambridge Center, Cambridge, MA 02142,
617/621-8700.

   The OSF licenses source code, which is compiled
into machine code for various platforms by its
members.  The source code, originally developed
inhouse, is currently outsourced.  Following are
OSF's major products.

                       OSF/1
OSF/1 is the operating system that uses Carnegie
Mellon's Mach kernel.  It is a B1-secure, symmetric
multiprocessing operating system that can run on
multiple processors within the same machine.
Compliant with POSIX, XPG4 and SVID base and kernel
extensions.  IBM, HP, DEC and Hitachi are major
users of OSF/1 in full or in part.

                       Motif
Motif is a graphical user interface (GUI) for
applications running on any system with X Window
Version 11.  Compliant with POSIX, ANSI C and XPG,
Motif is the de facto standard graphical interface
for UNIX.

                        DCE
The Distributed Computing Environment is a set of
integrated programs that provides an environment
for developing and maintaining client/server
applications across heterogeneous platforms in a
network.  DCE includes security, directory naming,
time synchronization, file sharing, RPCs and
multithreading services.

   Increasingly, database vendors are adding
support for DCE.  Thus, enterprise adoption of DCE
will let users access databases by name no matter
where they reside in the network.  See application
partitioning.

                        DME
The Distributed Management Environment is a set of
integrated programs that provides coherent
management of systems and networks.  DME provides
services for software distribution and licensing
and supports X/Open's XMP high-level management
protocol.

                       ANDF
The Architecture Neutral Distribution Format
supports developing portable applications.  The
developer generates an intermediate ANDF language
that can be shrink-wrapped.  Each target machine
would then have an ANDF compiler that compiles the
intermediate language into machine language when it
is installed.

   In order for ANDF to provide universal, shrink-
wrapped UNIX software, every hardware vendor would
have to support it.  Because UNIX runs on so many
different computers, shrink-wrapped UNIX may always
be a dream, unless the hardware world were to
consolidate into two or three platforms some day.
See PowerOpen.





OSF/Motif
See Motif and OSF.



OSI
(Open System Interconnection)  An ISO standard for
worldwide communications that defines a framework
for implementing protocols in seven layers.

   Control is passed from one layer to the next,
starting at the application layer in one station,
proceeding to the bottom layer, over the channel to
the next station and back up the hierarchy.

   Most of this functionality exists in all
communications networks; however, non-OSI systems
often incorporate two or three layers into one.

   Vendors have agreed to support OSI in one form
or another; however OSI serves more as a model than
a universal standard.  Many OSI components are too
loosely defined, and proprietary standards are
entrenched.  One exception is the OSI-compliant
X.400 e-mail protocol that is widely implemented.

   Learning the OSI layers and functions is
essential for understanding communications
networks.  See OSI model.



OSI model

      User
        
  Ŀ   The purpose for communicating.
 7Application    E-mail, file transfers,
     transactions, remote services.
  Ŀ
 6Presentation   Transfer syntax.
  
  Ŀ   Coordinates
 5  Session      overall flow of
     communications.
  Ŀ
 4 Transport     End to end control.
  
  Ŀ   Routes data from sending
 3  Network      to receiving station.
  
  Ŀ   Node to node control.
 2 Data Link     (Token Ring, Ethernet, SDLC
      HDLC/X.25, Xmodem, Zmodem)
        
  Ŀ   Transmission type,
 1  Physical     encoding method, speeds,
                 cable, plugs.
     (RS-232, TDM, FDM)
        
         Transmission medium (twisted pair,
                              coax, optical fiber)
  Ŀ
 1  Physical  
  


               Application - Layer 7
This top layer defines the language and syntax that
programs use to communicate with other programs.
The application layer represents the purpose of
communicating in the first place.  For example, a
program in a client workstation uses commands to
request data from a program in the server.  Common
functions at this layer are opening, closing,
reading and writing files, transferring files and
e-mail messages, executing remote jobs and
obtaining directory information about network
resouces.


              Presentation - Layer 6
When data is transmitted between different types of
computer systems, the presentation layer negotiates
and manages the way data is represented and
encoded.  For example, it provides a common
denominator between ASCII and EBCDIC machines as
well as between different floating point and binary
formats.  Sun's XDR and OSI's ASN.1 are two
protocols used for this purpose.  This layer is
also used for encryption and decryption.


                 Session - Layer 5
Provides coordination of the communications in an
orderly manner.  It determines one-way or two-way
communications and manages the dialogue between
both parties; for example, making sure that the
previous request has been fulfilled before the next
one is sent.  It also marks significant parts of
the transmitted data with checkpoints to allow for
fast recovery in the event of a connection failure.

   In practice, this layer is often not used or
services within this layer are sometimes
incorporated into the transport layer.


                Transport - Layer 4
The transport layer is responsible for overall end
to end validity and integrity of the transmission.
The lower data link layer (layer 2) is only
responsible for delivering packets from one node to
another.  Thus, if a packet gets lost in a router
somewhere in the enterprise internet, the transport
layer will detect that.  It ensures that if a 12MB
file is sent, the full 12MB is received.

   "OSI transport services" include layers 1
through 4, collectively responsible for delivering
a complete message or file from sending to
receiving station without error.


                 Network - Layer 3
The network layer establishes the route between the
sending and receiving stations.  The node to node
function of the data link layer (layer 2) is
extended across the entire internetwork, because a
routable protocol contains a network address in
addition to a station addresses.

   This layer is the switching function of the
dial-up telephone system as well as the functions
performed by routable protocols such as IP, IPX,
SNA and AppleTalk.  If all stations are contained
within a single network segment, then the routing
capability in this layer is not required.


                Data Link - Layer 2
The data link is responsible for node to node
validity and integrity of the transmission.  The
transmitted bits are divided into frames; for
example, an Ethernet or Token Ring frame for local
area networks (LANs).  Layers 1 and 2 are required
for every type of communications.  For more on this
layer, see data link protocol.


                Physical - Layer 1
The physical layer is responsible for passing bits
onto and receiving them from the connecting medium.
This layer has no understanding of the meaning of
the bits, but deals with the electrical and
mechanical characteristics of the signals and
signalling methods.  For example, it comprises the
RTS and CTS signals in an RS-232 environment, as
well as TDM and FDM techniques for multiplexing
data on a line.


                 End of OSI model.






OSI stack
See OSI model.



OSPF
(Open Shortest Path First)  A router protocol that
determines the least expensive path for routing a
message.  OSPF was originally developed to replace
the RIP protocol.



OT
(Object Technology)  The use of objects.



OTPROM
(One Time PROM)  A PROM chip that can be programmed
only once.



out of band
Outside the primary system or frequency.  For
example, any routing or network service from a long
distance carrier that is not directly switching a
customer's voice is an out-of-band service.  See
signaling in/out of band.



out of memory
See Windows memory limitation.



outdent
Same as hanging indent and hanging paragraph.



outer join
See join.



outline font
A type of font made from basic outlines of each
character.  The outlines are scaled into actual
characters (bitmaps) before printing.  See scalable
font.



outline processor
Software that allows the user to type in thoughts
and organize them into an outline form.



output
(1) Any computer-generated information displayed on
screen, printed on paper or in machine readable
form, such as disk and tape.

(2) To transfer or transmit from the computer to a
peripheral device or communications line.



output area
A reserved segment of memory used to collect data
to be transferred out of the computer.  Same as
buffer.



output bound
Excessive slowness due to output functions,
typically slow-speed communications lines or
printers.  See print buffer.



output device
Any peripheral that presents output from the
computer, such as a screen or printer.  Although
disks and tapes receive output, they are called
storage devices.



outsourcing
Contracting with outside consultants, software
houses or service bureaus to perform systems
analysis, programming and datacenter operations.
See facilities management.



OverDrive CPU
An Intel CPU chip used to upgrade existing 486SX
and 486DX PCs.  The internal clock speed of the
OverDrive CPU is twice that of the regular chip,
thus a 486/33 becomes a 486/66 internally.



overflow error
An error that occurs when calculated data cannot
fit within the designated field.  The result field
is usually left blank or is filled with some symbol
to flag the error condition.



overhead
(1) The amount of processing time used by system
software, such as the operating system, TP monitor
or database manager.

(2) In communications, the additional codes
transmitted for control and error checking, which
take more time to process.



overlay
(1) A preprinted, precut form placed over a screen,
key or tablet for indentification purposes.  See
keyboard template.

(2) A program segment called into memory when
required.  When a program is larger than the memory
capacity of the machine, the parts of the program
that are not in constant use can be set up as
overlays.  When called in, the contents of the
previous overlay is lost.  Virtual memory is a
system of automatic overlays.



overlay card
A controller that digitizes NTSC signals from a
video source for display in the computer.



overloading
In programming, the ability to use the same name
for more than one variable or procedure, requiring
the compiler to differentiate them based on
context.



oversampling
Creating a more accurate digital representation of
an analog signal.  In order to work with real-world
signals in the computer, analog signals are sampled
some number of times per second (frequency) and
converted into digital code.  Using averaging and
different algorithms, samples can be generated
between existing samples, creating more digital
information for complex signals, "smoothing out the
curve" so to speak.

   Sampling requires at least twice the bandwidth
of the frequency being sampled.  For example, with
regard to sound, 20KHz is the highest frequency
perceptible to the human ear, and sampling is done
at 44.1KHz for high quality audio playback.  A 2x
oversampling means that the CD player runs at twice
the rate, or 88.2KHz, and inserts a made-up sample
in between each real sample on the disc.  An 8x
oversampling runs eight times faster and so on.
See sampling rate.



overscan
Outside of the normal rectangular viewing area on a
display screen.  Contrast with underscan.



overstrike
(1) To type over an existing character.

(2) A character with a line through it.



overwrite
(1) A data entry mode that writes over existing
characters on screen when new characters are typed
in.  Contrast with insert mode.

(2) To record new data on top of existing data such
as when a disk record or file is updated.



p-code
See pseudo language and UCSD p-System.



p-System
See UCSD p-System.



P24T
See Pentium.



P5
The code name from Intel for the Pentium CPU.



P6
The code name from Intel for the successor to the
Pentium.  Also called the 686 by industry analysts,
since it follows the Pentium, which was originally
to be named the 586.  This chip is expected in 1995
with as many as six million transistors using .6
micron technology (transistor elements as small as
.6 micron) and be twice as fast as the Pentium.



P7
The code name from Intel for the sucessor to the
P6.  It is expected in the 1996-1997 time frame
with as many as 25 million transistors.



PA-RISC
See HP PA-RISC.



PABX
(Private Automatic Branch eXchange)  Same as PBX.



PACBASE
Integrated CASE software for IBM, Bull HN and
Unisys mainframes from CGI Systems, Pearl River,
NY.  It supports a wide variety of databases
including DB2 and Oracle.  PACLAN is the version
for PCs running on LANs.



pack
(1) To compress data in order to save space.
Unpack refers to decompressing data.  See data
compression.

(2) An instruction that converts a decimal number
into a packed decimal format.  Unpack converts a
packed decimal number into decimal.

(3) In database programs, a command that removes
records that have been marked for deletion.



package
See software package.



packaged software
See software package.



packbase
See PACBASE.



packed decimal
A storage mode that places two decimal digits into
one byte, each digit occupying four bits.  The sign
occupies four bits in the least significant byte.



packet
A block of data (a frame) used for transmission in
LANs and packet switching systems.



packet cellular
The transmission of data over the cellular network.
Data is divided into packets, or frames, for error
checking.  Contrast with circuit cellular.  See
CDPD and wireless.



Packet Exchange Protocol
See PEP.



packet overhead
Refers to the time it takes to transmit data on a
packet-switched network.  Each packet requires
extra bytes of format information, which, combined
with the assembly and dissassembly of packets,
reduces the overall transmission speed of the raw
data.



packet radio
The wireless transmission of data, which is divided
into packets, or frames, for error checking.  See
Ardis and Mobitex.



packet switching
A networking technology that breaks up a message
into smaller packets for transmission.  It is the
most common form of data transmission technology
used in LANs, MANs and WANs.

   Unlike circuit switching, which requires a
constant point-to-point circuit to be established,
each packet in a packet switched network contains a
destination address.  Thus all packets in a single
message do not have to travel the same path.  They
can be dynamically routed over the network as
circuits become available or unavailable.  The
destination computer reassembles the packets back
into their proper sequence.

   An advantage of packet switching over point-to-
point switched or private services is that it
allows for a one-to-many transmission.  A message
can be broadcast to many recipients.

   Packet switching efficiently handles messages of
different lengths and priorities.  By accounting
for packets sent, a public network can charge
customers for only the data they transmit.  Packet
switching is suitable for data, but not realtime
voice and video.

   The international standard for wide area packet
switching networks is X.25, which was defined when
all circuits were analog.  Newer technologies, such
as frame relay and ATM are designed for today's
almost-error-free digital lines.

   ATM uses a cell-switching technology that
provides the bandwidth-sharing efficiency of packet
switching with the guaranteed bandwith of circuit
switching.

   Public packet switching networks may provide
value added services, such as protocol conversion
and electronic mail.  Contrast with circuit
switching.



packetized voice
The transmission of realtime voice in a packet
switching network.



packing density
The number of bits or tracks per inch of recording
surface.  Also refers to the number of memory bits
or other electronic components on a chip.



pad
(1) To fill a data structure with padding
characters.

(2) (PAD)  (Packet Assembler/Disassembler)  A
communications device that formats outgoing data
into packets of the required length for
transmission in an X.25 packet switching network.
It also strips the data out of incoming packets.



padding
Characters used to fill up unused portions of a
data structure, such as a field or communications
message.  A field may be padded with blanks, zeros
or nulls.



paddle
An input device that moves the screen cursor in a
back-and-forth motion.  It has a dial and one or
more buttons and is typically used in games to hit
balls and steer objects.  See joy stick.



page
(1) In virtual memory systems, a segment of the
program that is transferred into memory.

(2) In videotex systems, a transmitted frame.

(3) In word processing, a printed page.



page break
In printing, a code that marks the end of a page.
A "hard" page break, inserted by the user, breaks
the page at that location.  "Soft" page breaks are
created by word processing and report programs
based on the current page length setting.



page description language
A device-independent, high-level language for
defining printer output.  If an application
generates output in a page description language,
such as PostScript, the output can be printed on
any printer that supports it.

   Much of the character and graphics shaping is
done within the printer rather than in the user's
computer.  Instead of downloading an entire font
from the computer to the printer, which includes
the design of each character, a command to build a
particular font is sent, and the printer creates
the characters from font outlines.  Likewise, a
command to draw a circle is sent to the printer
rather than sending the actual bits of the circle
image.



page fault
A virtual memory interrupt that reads the required
page from disk when the next instruction or item of
data is not in memory.



page frame
See EMS.



page header
Common text that is printed at the top of every
page.  It generally includes the page number and
headings above each column.



page makeup
Formatting a printed page, which includes the
layout of headers, footers, columns, page numbers,
graphics, rules and borders.



page mode memory
The common dynamic RAM chip design.  Memory bits
are accessed by row and column coordinates.
Without page mode, each bit is accessed by pulsing
the row and column select lines.  With page mode,
the row (page) is selected only once for all bits
(columns) within the row, resulting in faster
access.



page printer
A type of printer that prints a page at a time.
See laser printer and ion deposition.



page recognition
Software that recognizes the content of a printed
page which has been scanned into the computer.  It
uses OCR to convert the printed words into computer
text and should be able to differentiate text from
other elements on the page, such as pictures and
captions.



PageMaker
A full-featured desktop publishing program for the
PC and Macintosh from Aldus Corporation, Seattle,
WA.  Originally introduced for the Mac in 1985, it
set the standard for desktop publishing.  In fact,
Paul Brainerd, president of Aldus, coined the term
desktop publishing.  The PC version was introduced
in 1987.



pagination
(1) Page numbering.

(2) Laying out printed pages, which includes
setting up and printing columns, rules and borders.
Although pagination is used synonymously with page
makeup, the term often refers to the printing of
long manuscripts rather than ads and brochures.



paging
(1) In a virtual memory computer, paging is the
transfer of program segments (pages) into and out
of memory.  Although paging is the primary
mechanism for virtual memory, excessive paging is
not desired.  See thrashing.

(2) A communications service that is evolving from
a one-way beeper service to a one-way text service,
and eventually, to a two-way text and voice
service.  It is expected that the paging industry
will undergo several changes as new hand-held
devices and wireless services mature.  See PCS.



paint
(1) In computer graphics, to "paint" the screen
using a tablet stylus or mouse to simulate a
paintbrush.

(2) To transfer a dot matrix image as in the phrase
"the laser printer paints the image onto a
photosensitive drum."

(3) To create a screen form by typing anywhere on
screen.  To "paint" the screen with text.



paint program
A graphics program that allows the user to simulate
painting on screen with the use of a mouse or
graphics tablet.  Paint programs create raster
graphics images made up of dots.  Full-featured
paint programs provide a variety of image editing
capabilities for enhancing scanned images which are
also created in the raster format.

   Unlike drawing programs, which generate vector
graphics images, the picture objects created in a
paint program cannot be easily isolated and scaled
independently.  Raster graphics files are much like
a painted canvas: objects are "painted" together.
However, colors can be changed and parts or all of
an image can be run through image filters to create
a wide variety of special effects.  See image
editing program.



Painter
A full-featured paint program for Macintosh and
Windows from Fractal Design Corporation, Aptos, CA.
Painter is noted for its very sophisticated image
editing and watercolor simulation capabilities.
The Painter disks and manuals comes packaged in a
rather unique, yet appropriate manner... in a paint
can.



PAL
(1) (Paradox Application Language)   Paradox's
programming language.

(2) (Programmable Array Logic)  A programmable
logic chip (PLD) technology from Advanced Micro
Devices.

(3) (Phase Alternating Line)  A European color TV
standard that broadcasts an analog signal at 625
lines of resolution 25 interlaced frames per second
(50 half frames per second).  PAL's color
transmission is accurate, requiring no hue control
on a PAL TV.  Contrast with NTSC and SECAM.



palette
(1) In computer graphics, the total range of colors
that can be used for display, although typically
only a subset of them can be used at one time.  May
also refer to the collection of painting tools
available to the user.

(2) A set of functions or modes.



palmtop
A computer small enough to hold in one hand and
operate with the other.  Palmtops may have
specialized keyboards or keypads for data entry
applications or have small qwerty keyboards.



pan
(1) In computer graphics, to move (while viewing)
to a different part of an image without changing
magnification.

(2) To move (while viewing) horizontally across a
text record.



Pantone Matching System
See PMS.



Panvalet
See CA-Panvalet.



paper tape
(1) A slow, low-capacity, sequential storage medium
used in the first half of the 20th century to hold
data as patterns of punched holes.

(2) A paper roll printed by a calculator or cash
register.



paperless office
Long predicted, the paperless office is still a
myth.  Although paper usage has been reduced in
some organizations, it has increased in others.
Today's PCs make it easy to churn out documents.

   In time, laptop computers with immense storage
and high-resolution screens will serve to replace
paper when travelling.  Optical fiber networks will
make it easy to send data, pictures, voice and
video quickly.

   As color laser printers become commonplace, it
will be easy to reproduce any document, no matter
how complex.  People will eventually get used to
the idea that a paper document is no better proof
of a transaction than its electronic form.  When
this occurs, the paperless office will arrive.



paradigm
Pronounced "para-dime."  A model, example or
pattern.



Paradise
A family of display adapters for PCs from the
Paradise subsidiary of Western Digital Corporation,
Irvine, CA.



Paradox
A relational database management (DBMS) and
application development system for DOS and Windows
from Borland.  Paradox is known for its ease of use
and query by example method for asking questions.
Its PAL programming language is unique.  Many PAL
statements are interactive Paradox commands, so
that a Paradox user can adjust to programming more
easily.  Version 4.0 supports memo fields and
BLOBs.  The Paradox engine (available separately)
lets C applications access Paradox databases.

   Paradox for Windows comes with the Borland
Database Engine, which turns Paradox into a
client/server development system that can access
remote database servers (see Borland Database
Engine).



paragraph
In DOS programming, a 16 byte block.  Memory
addresses are generated as "segment:offset," where
the segment is expressed in paragraphs.  To compute
an address, the segment register is shifted left
four bits (multiplying it by 16).  For example, the
address A000:0100 = 655,616:

     Segment    A000     655,360 (40,960 X 16)
     Offset      0100        256
     Result     A0100    655,616

   This means there are 4,096 possibilities for
expressing each memory byte, a situation that has
helped generate confusion.



paragraph tag
In desktop publishing, a style sheet assigned to a
text paragraph.  It defines font, tab, spacing and
other settings.



parallel computing
Solving a problem with multiple computers or
computers made up of multiple processors.  It is an
umbrella term for a variety of architectures,
including symmetric multiprocessing (SMP), clusters
of SMP systems and massively parallel processors
(MPPs).  See SMP, MPP, pipeline processing, array
processor, vector processor and hypercube.



parallel data query
See PDQ.



parallel interface
A multiline channel that transfers one or more
bytes simultaneously.  Personal computers generally
connect printers via a Centronics 36-wire parallel
interface, which transfers one byte at a time over
eight wires, the remaining ones being used for
control signals.  Large computer parallel
interfaces transfer more than one byte at a time.
It is faster than a serial interface, because it
transfers several bits concurrently.  Contrast with
serial interface.  See Centronics.



parallel port
A socket on a computer used to connect a printer or
other peripheral device.  It may also be used to
attach a portable hard disk, tape backup or CD-ROM.
Transferring files between two PCs can be
accomplished by cabling the parallel ports of both
machines together and using a file transfer program
such as LapLink.

   On the back of a PC, the parallel port is a 25-
pin female DB-25 connector.  In a PC, the parallel
port circuit is contained on a small expansion card
that plugs into an expansion slot.  Typically two
serial ports, one parallel port and one game port
are on the card.  These ports are often also
included on an IDE host adapter card, which takes
up only one expansion slot and provides hard and
floppy disk control as well as I/O.

   The Enhanced Parallel Port, or EPP, is a higher-
speed parallel port standard that has been
sanctioned by the IEEE.  The EPP is expected to
become widely used on PCs.  See IEEE 1284.



parallel processing
(1) An architecture within a single computer that
performs more than one operation at the same time.
See pipeline processing, array processor and vector
processor.

(2) An architecture using mulitiple computers.  See
parallel computing.



parallel server
A computer system used as a server that provides
various degrees of simultaneous processing.  See
SMP, massively parallel and multiprocessing.



parallel transmission
Transmitting one or more bytes at a time using a
cable with multiple lines dedicated to data (8, 16,
32 lines, etc.).  Contrast with serial
transmission.



parallelism
An overlapping of processing, input/output (I/O) or
both.



parallelizing
To generate instructions for a parallel processing
computer.



parameter
(1) Any value passed to a program by the user or by
another program in order to customize the program
for a particular purpose.  A parameter may be
anything; for example, a file name, a coordinate, a
range of values, a money amount or a code of some
kind.  Parameters may be required as in parameter-
driven software (see below) or they may be
optional.  Parameters are often entered as a series
of values following the program name when the
program is loaded.

   A DOS switch is a parameter.  For example, in
the DOS Dir command   dir /p  the DOS switch /p
(pause after every screenful) is a parameter.

(2) In programming, a value passed to a subroutine
or function for processing.  Programming today's
graphical applications with languages such as C,
C++ and Pascal requires knowledge of hundreds, if
not thousands, of parameters.

   In the following C function, which creates the
text window for the Windows version of this
database, there are 11 parameters passed to the
CreateWindow routine.  Some of them call yet other
functions for necessary information.  In order to
call this routine in a program, the programmer must
decide what the values are for every parameter.

 hWndText = CreateWindow    (
      "TextWClass",
       NULL,
       WS_CHILD|WS_BORDER|WS_VSCROLL|WS_TABSTOP,
       xChar*23+GetSystemMetrics(SM_CXVSCROLL)+8,
       yChar*4,
       Rect.right-Rect.left+1-xChar*23
          -2*GetSystemMetrics(SM_CXVSCROLL)+5,
       yChar*(Lines+1)+2,
       hWnd,
       IDC_TEXTLIST,
       (HANDLE)hInstance,
       NULL                 ) ;





parameter-driven
Software that requires external values expressed at
runtime.  A parameter-driven program solves a
problem that is partially or entirely described by
the values (parameters) that are entered at the
time the program is loaded.  For example, typing 
bio 6-20-36  might load a program that calculates
biorhythms for someone born on June 20, 1936.  In
this case, the date is a required parameter.  The
more user-friendly approach is a menu-driven
program that would have you select a menu option
and present you with a data entry box to type in
date of birth.

   Parameter-driven software is widely used when a
program is called for and loaded by another program
rather than by the user.  Since the parameters are
generated by one program and used by another, any
number of parameters can be passed no matter how
obscure the codes.



parameter RAM
See PRAM.



PARC
(Palo Alto Research Center)  Xerox's research and
development center where the Smalltalk programming
language and GUI interface were developed.
Established in 1970, it is located in the Stanford
University Industrial Park, Palo Alto, CA.



parent-child
In database management, a relationship between two
files.  The parent file contains required data
about a subject, such as employees and customers.
The child is the offspring; for example, the child
of a customer file may be the order file.



parent program
The main, or primary, program or first program
loaded into memory.  See child program.



parity bit
An extra bit attached to the byte, character or
word used to detect errors in transmission.



parity checking
An error detection technique that tests the
integrity of digital data within the computer
system or over a network.  Parity checking uses an
extra ninth bit that holds a 0 or 1 depending on
the data content of the byte.  Each time a byte is
transferred or transmitted, the parity bit is
tested.

   Even parity systems make the parity bit 1 when
there is an even number of 1 bits in the byte.  Odd
parity systems make it 1 when there is an odd
number of 1 bits.



parity drive
A separate disk drive that holds parity bits in a
disk array.  See RAID.



parity error
An error condition that occurs when the parity bit
of a character is found to be incorrect.



park
To retract the read/write head on a hard disk to
its home location before the unit is physically
moved in order to prevent damage.  Most modern
drives park themselves when the power is turned
off.



parse
To analyze a sentence or language statement.
Parsing breaks down words into functional units
that can be converted into machine language.  For
example, to parse the dBASE expression

   sum salary for title = "MANAGER"

   SUM must be identified as the primary command,
FOR as a conditional search, TITLE as a field name
and MANAGER as the data to be searched.

   Parsing breaks down a natural language request,
such as "What's the total of all the managers'
salaries" into the commands required by a high-
level language, such as in the example above.





parser
A routine that performs parsing operations on a
computer or natural language.



partition
A reserved part of disk or memory that is set aside
for some purpose.



partitioning
To divide a resource or application into smaller
pieces.  See partition, application partitioning
and PDQ.



Pascal
A high-level programming language developed by
Swiss professor Niklaus Wirth in the early 1970s
and named after the French mathematician, Blaise
Pascal.  It is noted for its structured
programming, which caused it to achieve popularity
initially in academic circles.  Pascal has had
strong influence on subsequent languages, such as
Ada, dBASE and PAL.  See Turbo Pascal.

   Pascal is available in both interpreter and
compiler form and has unique ways of defining
variables.  For example, a set of values can be
stated for a variable, and if any other value is
stored in it, the program generates an error at
runtime.  A Pascal set is an array-like structure
that can hold a varying number of predefined
values.  Sets can be matched and manipulated
providing powerful non-numeric programming
capabilities.

   The following Turbo Pascal example converts
Fahrenheit to Celsius:

   program convert;
   var
   fahr, cent : integer;
   begin
    write('Enter Fahrenheit ');
    readln(fahr);
    cent := (fahr - 32) * 5 / 9;
    writeln('Celsius is ',cent)
   end.





Pascaline
A calculating machine developed in 1642 by French
mathematician Blaise Pascal.  It could only add and
subtract, but gained attention because 50 units
were placed in prominent locations throughout
Europe.  Accountants expressed grave concern that
they might be replaced by technology!



passive hub
A central connecting device in a network that joins
wires from several stations in a star
configuration.  It does not provide any processing
or regeneration of signals.  Contrast with active
hub and intelligent hub.  See hub.



passive matrix
A common LCD technology used in laptops.  See LCD.



passive star
See passive hub.



passthrough SQL
See embedded SQL.



password
A word or code used to serve as a security measure
against unauthorized access to data.  It is
normally managed by the operating system or DBMS.
However, the computer can only verify the
legitimacy of the password, not the legitimacy of
the user.  See NCSC.


              Password Tips from the
    Office of Standards and Product Evaluation
         National Computer Security Center

CHANGE PASSWORD FREQUENTLY
The longer you use a password, the higher the risk
of losing it.

USE GOOD PASSWORDS
Don't use persons, places or things that can be
identified with you.

DON'T DISCLOSE YOUR PASSWORD
Your password is as valuable as the information it
protects.

INSPECT YOUR DATA
If you suspect someone has tampered with your
files, report it immediately.

NEVER LEAVE AN ACTIVE TERMINAL UNATTENDED
Always log off or lock your terminal before leaving
it.

REPORT ANY SUSPECTED COMPUTER MISUSE OR ABUSE
Whether directed against you or not, abuse or
misuse of your computer resources only hinders the
timely completion of your tasks.





paste
See cut & paste.



patch
A temporary or quick fix to a program.  Too many
patches in a program make it difficult to maintain.
It may also refer to changing the actual machine
code when it is inconvenient to recompile the
source program.  See MIDI patch.



path
(1) In communications, the route between any two
nodes.  Same as line, channel, link or circuit.

(2) In database management, the route from one set
of data to another, for example, from customers to
orders.

(3) The route to a file on a disk.  In DOS and
OS/2, the path for file MYLIFE located in
subdirectory STORIES within directory JOE on drive
C: looks like:

            c:\joe\stories\mylife


   The equivalent UNIX path follows.  UNIX knows
which drive is used:

            /joe/stories/mylife


   The Macintosh also uses a path in certain
command sequences; for example, with "hard disk" as
the drive, the same path is:

          hard disk:joe:stories:mylife


   See DOS path name, DOS Path, DOS directories and
DOS abc's.





Path not found
A DOS error message that means you entered an
invalid path name.  See DOS Path.



PATHWORKS
A network operating system from Digital that lets a
VAX minicomputer function as a server for DOS,
Windows, Windows NT, OS/2 and Macintosh clients.
DECnet, TCP/IP, AppleTalk and NetWare protocols are
supported.



PAX
(1) (Private Automatic Exchange) An inhouse
intercom system.

(2) (Parallel Architecture Extended)  A parallel
processing environment standard based on Intel's
i860 RISC chip, UNIX System V and Alliant
Computer's parallel and 3-D graphics technologies.



PAX-1
Software from VXM Technologies, Boston, MA, that
allows a network of computers to function as a
single parallel processing system.  It runs in an
Ethernet network under TCP/IP and supports personal
computers, minis and mainframes.



payware
Software distributed for money.  Contrast with
freeware.



PB
See PowerBuilder.



PBX
(Private Branch eXchange)  An inhouse telephone
switching system that interconnects telephone
extensions to each other, as well as to the outside
telephone network.  It may include functions such
as least cost routing for outside calls, call
forwarding, conference calling and call accounting.

   Modern PBXs use all-digital methods for
switching and can often handle digital terminals
and telephones along with analog telephones.



PC
(1) Also see printed circuit board.

(2) (Personal Computer)  Although the term PC is
sometimes used to refer to any kind of personal
computer (Mac, Amiga, etc.), in this database and
in general, PC refers to computers that conform to
the PC standard originally developed by IBM.

   Today the PC industry is governed by Intel,
Microsoft and major PC vendors collectively.  The
PC is the world's largest computer base; 1994
estimates are 100 to 150 million units.  A rather
wide range, one wonders who's keeping count.

   PCs are used as stand-alone personal computers
or as workstations and file servers in a LAN (local
area network).  They are predominantly used as
single-user systems under DOS; however, they are
occasionally used as a central computer in a
multiuser environment under UNIX and other
operating systems.

   IBM's first PC models had names: XT, AT,
Convertible, etc.  Models of the second-generation
PS/2 series use numbers: Model 30, 55, 80, etc.
(see IBM PC).  Compatibles often use the CPU
designation in the name, such as "386 Turbo."

   Although there are literally thousands of PC
vendors, from mom and pop shops to large mail order
houses (Dell, Gateway, etc.) to the major computer
companies (Compaq, HP, Digital, etc.), and of
course IBM, still the world's largest PC maker, all
PCs use an Intel x86 or compatible CPU.  See PC CPU
models.

   First attempts at cloning the IBM PC were not
all successful.  From 1982 to 1985, there were a
lot of "almost compatible" PCs.  However, as soon
as the part of the operating system known as the
ROM BIOS was successfully cloned and made
commercially available, true compatibles appeared
in abundance.

   Today, you can replace floppies, hard disks and
video displays, as well as add a scanner, CD-ROM or
other device without too much difficulty.  In
general, PC components are interchangeable.
Expansion cards are easily plugged in and out, and
an entire motherboard can be replaced with one
(from a different vendor) in about a half hour.

   The problems come when you add a second or third
device and run into a conflict with an existing one
(see PC conflicts).  In addition, having to modify
DOS's infamous AUTOEXEC.BAT and CONFIG.SYS
configuration files causes every novice to flinch
in the beginning.

   Conflicts aside, the PC has become a commodity
item, winding its way onto the shelves of a wide
variety of retail outlets.  This is a testimonial
to the power of a computer standard, even one
fraught with as many loopholes and inconsistencies
as this one.

   Today, most PCs run most software and work with
most plug-in boards, but there are always
exceptions.  With the myriads of adapters and
applications available for the PC, one device,
application, TSR or utility can always conflict
with another.  The way to guarantee that something
works is to try it.  This has been true since day
one in the computer business.

   To learn more about the PC, look up the
following definitions:

           PC CPU models
           PC operating environments
           PC data buses
           PC input/output
           PC printers
           PC floppy disks
           PC hard disks
           PC keyboards
           PC display modes





PC-8
A symbol set that contains the extended ASCII
characters of the IBM PC.



PC-98
A personal computer series from NEC.  It is the
most popular PC in Japan.



PC board
See printed circuit board.



PC bus
The bus architecture used in first-generation IBM
PCs and XTs.  It refers to the original 8-bit bus,
which accepted only 8-bit expansion boards.  In
286s and up, it was superseded by the 16-bit AT
bus, later known as the ISA bus.  Contrast with
ISA, EISA and Micro Channel.



PC card
(1) A credit-card sized, removable module that
contains memory, I/O or a hard disk.  The term may
refer to a variety of proprietary card-sized
products; however, the term "PC Card" is PCMCIA's
trademark for its PC card standard.  See PCMCIA.

(2) An expansion board for a PC.



PC color codes
Following are the color numbers for the 16
foreground and eight background colors in text
mode.  Foreground and background numbers are added
together; for example, white text on a red
background is 79.  To blink the text, add 128.

    NumberĿ
        Color     
  BACKGROUND  FOREGROUND
    0  Black       0
   16  Blue        1
   32  Green       2
   48  Cyan        3
   64  Red         4
   80  Magenta     5
   96  Brown       6
  112  Light gray  7

  FOREGROUND ONLY
   8  Dark gray
   9  Light blue
  10  Light green
  11  Light cyan
  12  Light red
  13  Light magenta
  14  Yellow
  15  White

  128  Blinking





PC configuration
See PC conflicts and plug and play.



PC conflicts
When adding new peripherals, such as a scanner, CD-
ROM, sound card, etc., to your ISA-bus PC, the new
plug-in board may conflict with a setting of an
existing board.  If you're adding your first or
even second device to a basic system, you may have
no conflicts, but as you add more, the chances are
greater.

   The reason for conflicts is that PCs use the
three following ways to transfer signals to a
peripheral device, and the settings associated with
these methods are not entirely standardized.

        1. IRQ
        2. I/O address (port address)
        3. memory address

   Most peripherals use an IRQ and an I/O address.
Many use a memory address.  When you install a new
board in your PC, you MUST read the installation
manual in order to find out what the initial
settings are and how to change them if necessary.
If a new board uses the same setting as an existing
board, it won't work properly or at all.  Or, it
will work and the old one won't, or both won't
work.


    EISA & Micro Channel Buses Ŀ
     Note: PCs that use the EISA and Micro  
     Channel buses still have the same      
     configuration problems, but the        
     boards are configurable by software,   
     eliminating the need to set switches   
     or jumpers on the boards themselves.   
                                            
     In addition, when a board is added, a  
     setup program is run to install the    
     board, and conflicts are identified    
     ahead of time.  Although the user      
     still has to participate under this    
     "plug and tell" capability, it is much 
     better than the "plug and hope"        
     situation with ISA cards.              
                                            
     Help is on its way.  The Plug and Play 
     standard is expected to provide a true 
     "plug and play" capability with ISA    
     cards.  See Plug and Play.             
   


                    Keep a List
If you plan on installing several peripherals, it's
a good idea to write down the status of each board
you install when you install it.  Utility programs,
such as MSD.EXE, which comes with Windows,
Quarterdeck's Manifest (QEMM386) and Helix's
Discover (NETROOM), will help you identify most
current settings, but not all of them.

   Make a chart like the one below and keep it
handy:

      Device     IRQ  I/O  Memory address
   Ŀ
    COM1                           
    COM2                           
    LPT1                           
    scanner                        
    CD-ROM                         
    etc.                           


              IRQ (Interrupt Request)
An interrupt is a method of signalling the computer
for attention.  There are 16 IRQ lines in a PC, but
only 15 are usable, because one line (IRQ 2) is
used to connect the first bank of eight to the
second bank (the early XTs had only eight lines).

   If the device uses an interrupt, it must use a
unique IRQ line.  IRQ settings are changed by
setting DIP switches or changing jumpers on the
board itself or by running a setup program.  Just
be sure that no two devices use the same interrupt
number.

   Some expansion boards are preset to one IRQ.  If
two such boards are preset to the same number and
cannot be changed with DIP switches, jumpers or
software, they cannot co-exist in the same PC.

   Following are the standard IRQ settings.  If a
second parallel port (LPT2) is not used, IRQ 5 is
available.  IRQ 9 is also often available, and IRQs
10, 11, 12 and 15 are "up for grabs."

      0 - System timer
      1 - Keyboard
      2 - Connects to IRQ 9
      3 - COM2, COM4
      4 - COM1, COM3
      5 - LPT2**
      6 - Floppy disk
      7 - LPT1
      8 - Realtime clock
      9 - VGA, 3270 emulation**
     10 - **
     11 - **
     12 - **
     13 - Math coprocessor
     14 - Hard disk
     15 - **

  ** For general use.  "The Battleground."


                    I/O Address
The I/O address, or port address, is one way a
peripheral device is identified, or addressed, from
another.  The addresses are numbered in hex; for
example:
                   280h
                   290h
                   2A0h

   Like IRQs, they are set with DIP switches or
jumpers on the board, or possibly by running a
setup program.  If you change settings, you may
have to identify that change elsewhere, such as by
changing a parameter in a device= line in the
CONFIG.SYS file.  Read the manual for your new
device.  There is no other source for that kind of
information.

   If you change I/O addresses and still have a
problem, try an address that is one or two numbers
apart on the list.  For example, if one board is
set to 280h and another at 290h, change 280h to
270h or 260h and try again.  For details on this
technology, see PC I/O addressing.

   The default I/O addresses for the parallel and
serial ports are:

           Port      PC     PS/2

           LPT1     378h    3BCh
           LPT2     278h    378h
           LPT3     3BCh    278h
           COM1     3F8h
           COM2     2F8h
           COM3     2E8h
           COM4     2E0h


                  Memory Address
A peripheral device often requires a block of upper
memory (between 640K-1M) for transferring data,
which must be reserved for its exclusive use.  Some
common devices, such as VGA video, use fixed areas
in upper memory that are automatically reserved.
With other devices, you have to find an unused
block in this area (for a diagram, see PC memory
map).

   That's why you'll find a number of memory
addresses to select, typically in the C800h to
F000h range (800-960K) so that you can hopefully
find an unused block.  Addresses are given with
either beginning or beginning-ending numbers in
hex; for example:

           B000          CC00-CEFF
           C800    or    CE00-D0FF
           D000          D000-D2FF

   When a block is chosen, it is also necessary to
inform your memory manager not to load other
drivers or TSRs into it.  This may be done by a
setup program or you may have to do it yourself by
adding an "exclude" to the line in CONFIG.SYS that
loads the memory manager.  For example, EMM386.EXE
is the memory manager in DOS 5 and Windows.  To
exclude the E800-EFFF block, the x= parameter is
added to the device= line as follows:

     device=emm386.exe noems x=e800-efff

   See DOS EMM386.EXE for more on the above syntax.
For other memory managers, such as QEMM and 386MAX,
a similar "exclude" parameter is also used.

   If you use Windows, an "exclude" line is also
added to the [386Enh] section in the SYSTEM.INI
file; for example:

            EMMExclude=e800-efff

   If you later change the board to another memory
area, both CONFIG.SYS and SYSTEM.INI must be
updated.


                DMA - Yet Another!
Although not as frequent as IRQs and I/O addresses,
some peripheral devices use the PC's DMA channels
to transfer data directly from memory to memory
without going through the CPU.  Sound cards
especially use this feature.  Like everything else,
there is no standard assignment for DMA channels,
and they can conflict.

   There are eight DMA channels commonly used as
follows.  Most sound cards are set to use DMA
channel 1.

         DMA channel     Used for
              0        8-bit transfer
              1        8-bit transfer
              2        Floppy disk controller
              3        8-bit transfer
              4        Cascaded from 0-3
              5        16-bit transfer
              6        16-bit transfer
              7        16-bit transfer



                      Summary
You MUST READ the installation manual that comes
with your peripheral.  Each type of board is
configured differently.  The first time you install
a new board, fill out the chart suggested above.
It will save you headaches later!  See Plug and
Play.





PC CPU models
The brains of the PC is a CPU, or processor, from
the Intel 8086 family (x86) of microprocessors or
from a company that makes x86-compatible CPUs, such
as AMD (Advanced Micro Devices) and Cyrix
Corporation.  IBM also makes its own x86-compatible
chips.  Following are the major classes of PCs.


               XT CLASS - 8086, 8088
The original PC launched by IBM in 1981 used the
16-bit 8088 CPU.  This architecture was chosen
because it was designed for easy migration from the
major personal computer base of that time, which
was made up of Z80 CPUs running the CP/M operating
system.

   Unfortunately, the design of the Intel 8086 and
8088 was not only limited to one megabyte of
memory, it was designed without flexibility for the
future (who knew this would become the world's
greatest hardware standard).  This architecture has
caused enormous confusion and problems for software
developers and users alike.  Although more advanced
CPUs (286, 386, etc.) came later, they had to build
in 16-bit operating modes to conform to the
original standard in order to run all PC
applications on the market.  DOS applications are
all written to the limitations of the first PC.

   These first PCs, known as XT-class machines,
survive in a second-hand market, but are best used
with older software that does not place much demand
on the computer.  XTs are too slow for intensive
graphics or Windows applications.

   Memory can be increased beyond one megabyte
using expanded memory (EMS).


                  AT CLASS - 286
First used in the IBM AT in 1984, the 286's 16-bit
CPU can address up to 16 megabytes of memory.  ATs
were generally nothing more than faster XTs.
Memory above one megabyte was rarely used for
applications until Windows 3.0 became popular.  By
then, 386s and 486s were widely used.

   AT-class machines are fast enough for most DOS
applications, but are sluggish under Windows.
However, they can run Windows 3.0 and 3.1, but not
Windows 95.


                 386, 486, Pentium
First used by Compaq in 1986, the 386, or 386DX, is
a 32-bit machine that runs faster than the 286 and
can address an unbelievable four gigabytes of
memory, although motherboards generally only have
slots for up to 32 or 64 megabytes.  Its flexible
architecture allows both extended and expanded
(EMS) memory to be allocated on demand (see memory
allocation).  386s will also run OS/2 2.0, Windows
NT, Windows 95 and other 32-bit operating systems
and applications.

   The advances in the 386 are carried forth in the
486 and Pentium CPUs.

   The 386SX is slower than the 386, but retains
the same 32-bit architecture.  The 386SL is
designed for battery conservation in laptops.

   With initial models introduced in late 1989, the
486, or 486DX, is two to five times as fast as a
386, depending on clock rates, and has a built-in
math coprocessor, required by CAD programs.  The
486 is better suited for today's demanding
applications than the 386 and has become the entry-
level CPU in the Intel x86 line.  The 486SX runs at
slower speeds than the 486DX and makes the
coprocessor an optional item.

   Introduced in 1993, the Pentium is the successor
to the 486 and is currently the fastest CPU in the
Intel x86 family.  It is used as a file server in a
LAN (local area network) as well as a high-end
desktop machine.  Internally, the Pentium is 300
times faster than an XT-class machine.  See PC
operating environments.


                
                Extended
                 Memory 
                 1MB and
                   up   
   Ŀ- - -Ĵ- - - - - - -
    8088        286    Conventional
    8086        386       Memory
    (XT)        486     Up to 1MB
              Pentium 
        
                   
   
      Expanded memory (EMS)
   

          CPUs AND MEMORY TYPES



   Ŀ
     For more details on Intel CPUs,  
              look up x86.            
                                      
    Also look up the invidivual CPUs: 
      8088, 286, 386, 486, Pentium    
   





PC data buses
The bus in a PC is the common pathway between the
CPU and the peripheral devices.  Controller boards
for the video, disks and other devices plug
directly into slots in the bus.

                        ISA
The original PC used an 8-bit bus (transfers 8 bits
simultaneously) known as the PC or XT bus.  With
the 286-based AT model, the bus was extended to 16-
bits.  Machines come with a mix of 8-bit and 16-bit
expansion slots.  8-bit expansion cards fit in both
slots, but 16-bit cards require 16-bit slots.  The
16-bit bus has becomn known as the ISA ("i-suh")
bus, or Industry Standard Architecture bus.

                   Micro Channel
When IBM introduced the PS/2 line, it switched from
the ISA bus to the high-speed 32-bit Micro Channel
(MCA) bus.  The MCA also provides bus mastering,
which has yet to be exploited.  Later, IBM
introduced ISA PS/2 models for greater
compatibility.  ISA and MCA expansion boards are
not interchangeable.

                       EISA
To counter the Micro Channel and extend the ISA bus
from 16 bits to 32 bits, EISA ("e-suh") was
conceived by the compatible vendors in 1988.  The
EISA bus accepts both EISA and ISA boards, but
still runs at the same clock speeds as the ISA bus
in order to accomodate ISA boards.

                     Local Bus
VESA's VL-bus and Intel's PCI bus are buses that
improve performance by providing a high-speed
channel directly to the CPU that bypasses the
slower ISA and EISA buses.

  See ISA, EISA, Micro Channel, VL-bus and PCI.





PC display modes
The screen resolution on a PC is determined by an
expansion board, called a display adapter or
graphics adapter, which is plugged into one of the
computer's expansion slots.  The monitor must also
be able to adjust to the resolutions of the display
adapter.  The common display adapter today is the
VGA adapter, which supports a number of resolutions
that have been standardized by VESA.  See VESA BIOS
Extension.

   When the computer boots up in DOS, the display
is in text mode with an on-screen resolution of
720x400 pixels with a maximum of 16 colors.  When
the PC is switched to graphics, either for Windows
or a graphics-based DOS application, the resolution
and colors can change depending on the capabilities
of the display adapter, monitor and application.

   All display adapters come with their own
software drivers for Windows.  The driver is
installed after the adapter is plugged in.  The
driver lets Windows display its output at all the
resolutions and colors the display adapter is
capable of.  Users switch resolutions by activating
a software control panel that manages the driver.

   The display adapter may also come with drivers
for major DOS applications such as AutoCAD and
WordPerfect.  These drivers have no effect on
Windows or other DOS applications.

   VESA supports four screen resolutions: 640x480,
800x600, 1024x768 and 1280x1024.  On monitors
smaller than 15", the lower 640x480 graphics
resolution is usually preferred.  On 17" monitors,
either 800x600 or 1024x768 is commonly used.  On 20
and 21" monitors, 1024x768 and 1280x1024
resolutions are used.  For desktop publishing
applications that require two visible pages on
screen, non-VESA resolutions of 1600x1200 and
1600x1280 are also used.  These resolutions are
expected to be supported by VESA some time in the
future.

   There are also display adapters and monitors
that provide even higher resolutions, such as
2016x1660 and 2048x1536.  Often monochrome only,
these systems are used for document imaging where
on-screen text must be as readable as possible.



          Summary of PC Display Standards
The following list summarizes each display type.
Detailed specifications follow this summary.

            VESA STANDARDS - SUPER VGA
     640x480 text & graphics (256-16M colors)
     800x600 text & graphics (16-16M colors)
    1024x768 text & graphics (16-16M colors)
   1280x1024 text & graphics (16-16M colors)

                IBM STANDARDS
  MDA   720x350 text only, monochrome
  CGA   320x200 text & graphics (4 colors)
  EGA   640x350 text & graphics (16 colors)
  MCGA  640x400 text; 320x200 graphics (256 cols)
  VGA   720x400 text; 640x480 graphics (16 colors)
  8514 1024x768 text & graphics (256 colors)
  XGA  1024x768 text & graphics (256 colors)

             HERCULES STANDARD
    720x348 text & graphics (monochrome)



             VESA MODES
      VESA BIOS Extension (VBE)
    Super VGA modes defined by VESA
   Decimal mode no.
      Hex mode no.         Video
                  Colors RAM used
  256  100  640x400   256   250K
  257  101  640x480   256   300K

  258  102  800x600    16   234K
  259  103  800x600   256   469K

  260  104  1024x768   16   384K
  261  105  1024x768  256   768K

  262  106  1280x1024  16   640K
  263  107  1280x1024 256  1280K

  264  108   80x60 text     9.3K
  265  109  132x25 text     6.4K
  266  10A  132x43 text    11.1K
  267  10B  132x50 text    12.9K
  268  10C  132x60 text    15.5K

  269  10D  320x200   32K   125K
  270  10E  320x200   64K   125K
  271  10F  320x200   16M   188K

  272  110  640x480   32K   600K
  273  111  640x480   64K   600K
  274  112  640x480   16M   900K

  275  113  800x600   32K   938K
  276  114  800x600   64K   938K
  277  115  800x600   16M  1406K

  278  116  1024x768  32K  1536K
  279  117  1024x768  64K  1536K
  280  118  1024x768  16M  2304K

  281  119  1280x1024 32K  2560K
  282  11A  1280x1024 64K  2560K
  283  11B  1280x1024 16M  3840K

      81FF  Special mode to save
            and restore video RAM.

  Note: As of VBE 2.0, VESA no longer defines new
modes by number.  It provides a mechanism for
defining the mode by resolution.


        Number    Pixel bits
      of colors    R  G  B

         32K       5  5  5
         64K       5  6  5
         16M       8  8  8



           EARLIER IBM MODES
   Mode no.
      CGA
    0  320x200  40x25 txt  16 gray
    1  320x200  40x25 txt  16 colors
    2  640x200  80x25 txt  16 gray
    3  640x200  80x24 txt  16 colors
    4  320x200  graphics    4 colors
    5  320x200  graphics    4 gray
    6  640x200  graphics   monochrome

       EGA
    0  320x350  40x25 txt  16 gray
    1  320x350  40x25 txt  16 colors
    2  640x350  80x25 txt  16 gray
    3  640x350  80x25 txt  16 colors
    7  720x350  80x25 txt  monochrome
   13  320x200  graphics   16 colors
   14  640x200  graphics   16 colors
   15  640x350  graphics   monochrome
   16  640x350  graphics   16 colors

       MCGA
    0  320x400  40x25 txt  16 gray
    1  320x400  40x25 txt  16 colors
    2  640x400  80x25 txt  16 gray
    3  640x400  80x25 txt  16 colors
   17  640x480  graphics   monochrome
   19  320x200  graphics   256 colors

       VGA
    0  360x400  40x25 txt  16 gray
    1  360x400  40x25 txt  16 colors
    2  720x400  80x25 txt  16 gray
    3  720x400  80x25 txt  16 colors
    7  720x400  80x25 txt  monochrome
   18  640x480  graphics   16 colors

       XGA
       640x480  graphics   256 colors
       640x480  graphics   64K colors
      1024x768  graphics   256 colors







PC-DOS
The DOS operating system from Microsoft supplied by
IBM with its PCs.  Up until DOS 6, PC-DOS was
almost identical to Microsoft's MS-DOS for non-IBM
PCs, and both versions are called DOS.  See "IBM's
DOS 6" under DOS 6.



PC EXPO
A trade show for resellers and corporate PC buyers
held in the summer (New York) and fall (Chicago).
It started in New York in 1983 with 120 exhibitors
and 9,600 attendees.  In 1994, more than 800
exhibitors drew 120,000 attendees.  PC EXPO is
sponsored by the Blenheim Group PLC, One Executive
Drive, Fort Lee, NJ 07024, 800/829-3976.  See also
Blenheim shows.

                     Schedule

            New York, Jun. 28-30, 1994
            Chicago,  Oct. 19-21, 1994

            New York, Jun. 20-22, 1995
            Chicago,  Oct. 3-5,   1995





PC floppy disks
Until recently, there were two kinds of floppy
disks routinely used in a PC: the 5.25" disk, which
is housed in a square, flexible envelope, and the
3.5" disk, housed in a rigid plastic case.  Today,
the 5.25" format has become nearly obsolete, and it
is safe to purchase a PC with only the 3.5" drive.

   The low-density 360KB, 5.25" disk, introduced
soon after the first PC, was widely used for retail
software, because it provided a common distribution
medium.  Even after the high-density 5.25" was
introduced on IBM's AT in 1984, which holds 1.2
megabytes, the 360KB disks were still often used.
The 1.2MB drives can read and write the 360KB
disks.

   If there is no manufacturer's label on a 5.25"
diskette, you cannot tell by looking at it whether
it is a 360KB or 1.2MB disk.  If the disk is used,
you can get a byte count by viewing its file
contents in Windows or DOS.

   The 3.5" diskettes were first introduced in a
low-density 720KB version on IBM's Convertible
laptop.  Capacity was doubled to 1.44MB with the
PS/2 line.  Due to their greater storage and
convenience, 3.5" drives have been retrofitted to
many machines and the 3.5" diskette has become the
medium of choice.  1.44MB drives can read, write
and format 720KB disks.

   You can tell the difference between the 720KB
and 1.44MB disks.  Looking at it from the label
side with the aluminum slider at the bottom, the
1.44MB disk has a hole in the upper left corner,
while the 720KB disk does not.

   Newer IBM models include the extra-high density
2.88MB floppy drives, compatible with the 1.44MB
disks.  However this format has not caught on.


                Floppy Disk Formats

  360KB  5.25"  DS/DD  Low density (Double Density)
  1.2MB  5.25"  DS/HD  High density

  720KB   3.5"  DS/DD  Low density (Double Density)
 1.44MB   3.5"  DS/HD  High density
 2.88MB   3.5"  DS/ED  Extra-high density

    The DS stands for double sided.
    Today, all floppies are double sided.





PC hard disks
The primary storage medium in a PC is a non-
removable hard disk.  Hard disks are available with
storage capacities from 40MB to 2GB and above.
Buying a system with less than an 80MB hard disk
may be shortsighted, considering the lower cost of
today's drives.  Applications are getting larger
and are using more and more of the hard disk all
the time.

   There have been several hard disk interface
standards used for PCs, including MFM, RLL, ESDI,
IDE and SCSI (see hard disk).  Today, most hard
drives sold with PCs are IDE and SCSI.  It depends
on the controller (expansion board) whether or not
another hard disk interface type can co-exist in
the PC.  In some cases, IDE and SCSI drives can co-
exist, in others they cannot.

   The IDE host adapter (expansion board) that
plugs into a PC can generally control two IDE hard
disks.  Installing the second IDE hard disk on a
reasonably-new PC is not complicated (see IDE~).

   Since most hard disks are not removable, the
low-level physical format of one drive has no
bearing on that of another in a different machine.
For example, two computers can be cabled together
and files can be transferred from the IDE hard disk
of one PC to the SCSI disk of another.  The hard
disk controllers are reading and writing their
disks according to their own technology.

   Removable disk drives and Bernoulli disks
provide the convenience of transportability and
unlimited amounts of storage, although each drive
holds only one disk module at a time.  Cartridges
come in 40MB and higher capacities, and optical
disks hold up to 600MB and more.  Each cartridge is
of a proprietary design and can be inserted only
into the drive it is designed for.

   As storage capacity grows, so does performance.
Disk access times run from 9 milliseconds (fast) to
100 ms (slow).  See hard disk.



PC I/O addressing
This is a method for passing signals from the CPU
to the controller boards of peripheral devices on
x86 machines.  I/O addresses, also called port
addresses, reference a separate memory space on
peripheral boards.  This is often confused with
memory-mapped peripherals, such as video cards,
which use a block of upper memory (UMB) in the
upper memory area (UMA).  Peripheral devices often
use both methods: an I/O address for passing
control signals and an upper memory block (UMB) for
transferring and buffering data to and from the
CPU.

   There is a 64K address space for I/O addresses,
although typically less than 1K is used.  Each
board that uses an I/O address contains a few bytes
of memory (16, 32, etc.) set to a default address
range.  One or more alternate addresses is also
provided to resolve conflicts with other boards.
These I/O spaces are a bunch of tiny memory banks
scattered over different devices.  As long as each
one is set to a different address, the CPU can
transmit signals to the appropriate boards without
conflict.

   An I/O address operation takes place as follows.
If a program needs to send a byte to the serial
port, it issues an OUT instruction to the CPU with
the address of that serial port.  The CPU notifies
the address bus to activate the I/O space, not
regular memory, and the address bus signals the
appropriate byte location on the board.  The CPU
then sends the data character over the data bus to
that memory location.



PC input/output
There are three ways of getting data into and out
of the PC.  The first is via the keyboard, which
plugs into a keyboard connector always built onto
the motherboard.  The keyboard plugs directly into
the 5-pin DIN receptacle.  The PS/2 uses a 6-pin
mini-DIN connector.

   The second is via the data bus, or expansion
bus, which is a set of slots on the motherboard.
Expansion boards, or cards, are plugged into the
slots and contain cables to their respective
devices.  These cards are control circuits for disk
drives, the video display, CD-ROM reader and
network adapter for example.  See PC conflicts.

   The third way is through serial and parallel
ports which are input/output pathways built into
the motherboard or contained on a separate
expansion board.  On the back of the PC, there are
typically two serial ports (one 9-pin male and one
25-pin male).  In DOS, the first port is named
COM1, and the second is COM2.  Both ports provide
the same capability.  The parallel port (LPT1) uses
a 25-pin female connector on the PC.

   The serial ports are typically used for modems,
mice, scanners and digitizer tablets, and the
parallel port is used for the printer, although
some printers use a serial port.  Both serial and
parallel ports can be used for file transfer
between two computers cabled together.

   Mice can be purchased for either the serial port
(serial mouse) or for connection via an expansion
board (bus mouse).  Some scanners and printers
require an expansion board, which accompanies the
product when you buy it and must be plugged into
the PC.



PC keyboard
(1) The keyboard introduced with the IBM PC that
provides a dual-function keypad for numeric entry
and cursor movement.  It was severely criticized
for its non-standard shift key placement, which was
corrected with the AT keyboard.  Regardless of key
placement, users love the feel of IBM keyboards.

(2) Any keyboard made for the PC, including the PC
keyboard, AT keyboard and Enhanced keyboard.



PC keyboards
IBM has had three generations of keyboards since
the introduction of the original PC, all of which
have been an annoyance for the touch typist.  The
original "PC keyboard" used an awkward return and
left shift key placement.  Finally corrected on the
"AT keyboard," the backspace key was made harder to
reach.  The "Enhanced keyboard" relocated a host of
keys, including the function keys, making it
impossible to assign them intelligently.  What was
easy on one keyboard is hard to reach on the other.

   Keyboard manufacturers make both the AT keyboard
and the Enhanced keyboard with the same key
placement.  Only a few dare to be different and
incorporate the best features of both.

   One advantage of PC keyboards is that they
usually work on all PCs, including laptops and even
XTs, in which case there is a switch on the bottom
of the keyboard marked XT and AT.  Switch it to XT
for XTs and AT for all others.  PC keyboards use a
5-pin DIN connector that plugs into a socket on the
motherboard.  With an adapter, the larger 5-pin DIN
plug can be connected to the smaller 6-pin mini DIN
socket used on laptops and PS/2s.

   Key placement on some PC laptops is dreadful,
placing often-used Ctrl and Alt keys in hard to
reach locations and forcing users to press the Fn
key for commonly-used functions.  Touch typists
beware!



PC LAN
(1) A network of IBM or IBM-compatible PCs.

(2) A network of any variety of personal computers.



PC memory
The original PC design was constrained to one
megabyte of memory.  In addition, certain parts of
the operating system were placed into fixed
locations in the upper part of memory without any
method for cooperatively storing additional drivers
and programs.  This design gave rise to the most
confusing platform in history.

   Following are the different types of memory in a
PC.  In other computers, there is just plain
memory.  In mainframes and supercomputers, there
are also large, auxiliary memory banks that
function as caches between disk and RAM.

   Conventional Memory       First 640K
   UMA (Upper Memory Area)   Next 384K
   HMA (High Memory Area)    Next 64K
   Extended Memory           From 1MB up
   EMS (Expanded Memory)     Additional memory
                              beyond 1MB bank-
                              switched into the UMA

   See PC memory map.




PC memory card
See memory card.



PC memory map
The following chart shows how the first megabyte of
RAM is used in a PC:

     Address                         
11000:0000 1088KĴ Extended
                HMA(high memory area)  Memory
10000:0000 1024KĴ------------
                PC ROM BIOSPS/2     
 F000:0000  960KĴROM BIOS 
                           & VGA ROM
 E000:0000  896K Available Ĵ Top 384K
                 for drivers and      of the
 D000:0000  832K   EMS page frame     first
 C800:0000  800KĴ megabyte
                  EGA, VGA ROM BIOS   of RAM is
 C000:0000  768KĴ called the
                    Free             upper
 BC00:0000  752KĴ          memory
                 CGA                 area (UMA)
                 Graphics  Hercules  made up
                 CGA, EGA, Graphics  of upper
                 VGA Text            memory
 B800:0000  736KĴ          blocks
                    Free             (UMBs)
 B400:0000  720KĴ         
                  MDA RAM           
 B000:0000  704KĴ
                EGA, VGA Graphics RAM
 A000:0000  640KĴ------------
                    Conventional     
                       Memory         Lower 640K
                                      is used by
                                      DOS and
                                      user
                                      programs.
                                     
                                     

                 DOS and COMMAND.COM 
                  Interrupt vectors  
              0K





PC-MOS/386
A multiuser PC operating system from The Software
Link, Inc., Norcross, GA.  It runs most standard
DOS applications as well as applications written
for the 386's Protected Mode.



PC network
(1) A network of IBM and/or IBM-compatible PCs.

(2) A network of any variety of personal computers.

(3) (PC Network)  The first PC LAN from IBM
introduced in 1984.  It inaugurated the NetBIOS
interface and uses the CSMA/CD access method.
Token Ring support was added later.  See MS-Net.



PC operating environments
Almost all PCs use the DOS operating system, which
was developed for the 8088 CPU with its maximum of
one megabyte of RAM.  The PC was also designed so
that the first 640K of the one megabyte is used for
applications, while the next 384K, or UMA (upper
memory area), is used by the operating system to
control peripheral devices (see PC memory map).
Since some of the 640K is also used by DOS, only
about 570K to 600K is available to user programs.

   As users became comfortable with PCs, they
wanted more than one application open and active at
the same time.  In order to get around DOS' single
task nature and the PC's 640K limit, a variety of
add-ons, techniques and remedies have been created
to solve this dilemma.  Following is a synopsis.


                       TSRs
In 1984, Borland introduced Sidekick and
popularized the TSR, or popup, program.  Sidekick
stayed in memory but swapped in and out of view by
pressing a hotkey, and users could instantly switch
to a handy phone directory or notepad.  However,
keeping many TSRs in memory may not leave room for
important, big applications, and TSRs are known to
cause conflicts.


                  Expanded Memory
In 1984, expanded memory (EMS) was created to break
the one megabyte barrier.  An EMS board with
multiple megabytes of RAM could be plugged in, and
its memory used directly by EMS applications.

   Lotus 1-2-3 quickly took advantage of it and
hundreds of other applications have been written to
use it.  EMS can be installed in all PCs from XTs
on up, a major advantage when XTs were purchased
widely.  See EMS for details.


           Task Switchers & Multitaskers
Programs such as Software Carousel extend DOS's
capabilities by allowing the user to keep a variety
of programs open at the same time and switch back
and forth between them.  These "task switchers" use
EMS memory, extended memory and/or the hard disk to
swap applications in and out of conventional
memory.

   Combining multitasking with task switching,
Quarterdeck's popular DESQview was the first
control program to use expanded (EMS) memory to
allow programs to run in, not just reside in, the
background.


                  Memory Managers
Memory managers were developed to store TSRs and
other memory-resident software (drivers) in the
384K UMA (upper memory area), thus freeing more
precious "conventional memory" in the 640K region.

   Memory managers manage both extended and EMS
memory, and products, such as QEMM-386, 386MAX and
DOS 6's EMM386.EXE, can allocate both types on
demand on 386s and up.  See DOS memory manager and
memory allocation.


          Extended Memory and Windows 3.x
By the late 1980s, the DOS extender was introduced,
which is software that allows DOS applications to
run in, not just reside in, extended memory in 286s
and up.  Paradox 386 and Lotus 1-2-3 Version 3.0
were some of the first programs to use it.

   Windows uses its own DOS extender to manage up
to 16MB of memory in Windows 3.0 and up to 256MB in
Windows 3.1.  It lets users launch, keep active and
switch between several Windows and DOS
applications.  Windows' ability to finally use
large amounts of memory in the PC contributed to
its success.


                     DOS 5 & 6
DOS 5 added a task switching capability that runs
multiple DOS applications and swaps inactive ones
to disk.  It improved memory management, freeing up
more conventional memory by loading operating
system components into upper memory areas (HMA and
UMA).

   DOS 6 improved memory management and added
realtime compression.  It can allocate extended
memory and EMS memory on demand, making it more
flexible for running a mix of old DOS and new
Windows programs.  Its DoubleSpace or DriveSpace
compression can double the capacity of a hard disk.
In DOS 6, for the first time, a variety of stand-
alone utility programs have been included.


                      DR DOS
DR DOS is a DOS-compatible operating system with
advanced memory management and other features that
always inspired Microsoft to include similar
functionality in its subsequent DOS releases.
Novell acquired DR DOS and added NetWare
functionality to it.


            Advanced Operating Systems
The OS/2 operating system from IBM is highly
regarded.  Its Workplace Shell interface is similar
to Windows, and it can also run DOS and Windows
applications.  OS/2 requires a 386 or higher
machine.

   Microsoft turned its development of OS/2 into
Windows NT, a redesigned operating system for 386s
and up.  NT is a stand-alone operating system that
doesn't use DOS, although it runs existing DOS and
Windows applications.  NT is more geared for the
network server than the desktop, but versions are
available for both client and server.

   Windows 95, expected by mid 1995, is also a
stand-alone operating system that will run earlier
DOS and Windows applications.


                   The Bad News
The legacy of TSRs, memory managers and task
switchers combined with the various versions of DOS
and Windows make quite a nightmare for the micro
manager responsible for personal computers in a
large enterprise.


                   The Good News
If somebody already set up your PC, you may not
have to deal with any of the bad news!

   In addition, Windows has become the primary
desktop operating system.  Although Windows is a
complicated environment to develop for, and it is
not as easy to use as was intended, it offers much
more consistency, integration and standardization
than the DOS world ever did.  It is the clear
winner.

   You should be able to buy Windows software
packages for years to come.  You should also be
able to run your DOS programs for a long time.  All
future operating systems for the desktop must be
able to run DOS and Windows programs.


          The PowerPC: A New Generation?
The alliance of IBM, Apple and Motorola launched
the PowerPC chip in 1993.  The Power Macintoshes,
the first machines to use the PowerPC, provide
extraordinary performance using the Macintosh
operating system.  The PowerMacs can also run DOS
and Windows applications.  IBM and other PC makers
will introduce PowerPC-based PCs in the 1995
timeframe with new operating systems that also run
DOS and Windows applications.  It's a whole new
ballgame!





PC Paintbrush
A PC paint program from ZSoft Corporation,
Marietta, GA, that is widely used and has set an
industry standard graphics format.  Its PCX raster
graphics format is generated and accepted by many
graphics, word processing and desktop publishing
programs.



PC printers
There are hundreds of printer models that work with
PCs from dot matrix to ink jet to laser printers
and most of them plug into the PC's parallel port.
Printing text files directly from DOS works with
all printers, but in order to select fonts,
boldface, underline and other print attributes, the
application must support the printer.

   Word processing, desktop publishing, CAD and any
other DOS package that offers full-featured
printing, provides drivers for the popular
printers.  These drivers are selected by the user
when installing the program, and fonts installed
for one application are often not sharable by
another.

   One of the significant advantages of Windows is
that once the printer installation has been
performed for Windows, every Windows application
can use all the installed fonts.  All Windows
applications use the print services in Windows to
do their printing.  Once products such as
LaserMaster's WinJet system, which extends Windows'
printing capabilities, is hooked into Windows, then
all applications use it.  In either case, Windows
provides a single, central facility for managing
all the installed fonts and doing the printing.

   For an explanation of the different types of
computers printers that have been manufactured, see
printer.



PC screen resolutions
See PC display modes.



PC Tools
A popular and comprehensive packages of utilities
for DOS and Windows from Symantec (originally
Central Point Software).  They include a DOS or
Windows shell as well as antivirus, file
management, caching, backup, compression and data
recovery utilities.



PC troubleshooting
See PC conflicts and Windows Resource Kit.



PCB
See printed circuit board.



PCD file
See Photo CD.



PCI
(Peripheral Component Interconnect)  A local bus
for personal computers that provides a high-speed
data path between the CPU and peripheral devices
(video, disk, network, etc.).  There are typically
three or four PCI slots on the motherboard.  There
may also be one or two built-in PCI controllers
(IDE, SCSI, network, etc.) on the motherboard.

   In a PC, the PCI bus coexists with the ISA or
EISA bus.  ISA and EISA boards still plug into an
ISA or EISA slot, while high-speed PCI boards plug
into a PCI slot.

   PCI provides "plug and play" capability,
automatically configuring the PCI cards at startup.
When PCI is used with the ISA bus, the only thing
that is generally required is to indicate in the
CMOS RAM which IRQs are already in use by ISA
cards.  PCI takes care of the rest.

   PCI runs at 33MHz, supports 32- and 64-bit data
paths and bus mastering.  The first PCs with PCI
buses became available in late 1993.  PCI is
processor independent and is available for PCs,
PowerPCs and other CPUs.  This architecture is
sanctioned by the PCI special interest group (SIG),
supported by over 100 manufacturers.  Its chief
designer and promoter is Intel.

   The number of peripheral devices the bus can
handle is based on loads, which have to do with
inductance, capacitance and other electrical
characteristics.  Normally there are 10 loads per
bus.  The basic PCI chipset uses three, leaving
seven for peripherals.  Controllers built onto the
motherboard use one load, whereas controllers that
plug into an expansion slot use 1.5 loads.



PCjr
(PC junior)  IBM's first home computer introduced
in 1983.  Its original keyboard was unsuitable for
typing, but adequate keyboards were later added.
It was discontinued in 1985.



PCL
(Printer Control Language)  The command language
for the HP LaserJet printers.  It has become a de
facto standard used in many printers and
typesetters.  PCL Level 5, introduced with the
LaserJet III in 1990, also supports Compugraphic's
Intellifont scalable fonts.



PCM
(1) (Pulse Code Modulation)  A technique for
digitizing speech by sampling the sound waves and
converting each sample into a binary number.  It
uses waveform coding that samples a 4KHz bandwidth
8,000 times a second.  Each sample is an 8 bit
number, resulting in 64K bits of data per second.
See ADPCM.

(2) (Plug Compatible Manufacturer)  An organization
that makes a computer or electronic device that is
compatible with an existing machine.



PCMCIA
(Personal Computer Memory Card International
Association)  A non-profit trade association
founded in 1989 to standardize the PC card.
Address: 1030G East Duane Ave., Sunnyvale, CA
94086, 408/720-0107.

   PCMCIA's trademarked name for its card is "PC
Card," although "PCMCIA Card" has become the more
popular term, requiring everyone to pronounce six
syllables instead of three.

   The PCMCIA card is a credit-card sized,
removable module that has become the expansion
vehicle for portable computers.  PCMCIA cards are
used to attach memory, modems, radio transceivers,
network adapters, solid state disks and hard disks
to a portable computer.  The PCMCIA card is a "plug
and play" device, which is configured automatically
by the PCMCIA Card Services software (see below).

   All PCMCIA cards are 85.6 mm long by 54 mm wide
(3.37" x 2.126") and use a 68-pin connector.  The
original Type I card is 3.3 mm thick and is now
used for memory in palmtops and other light-weight
applications.

   The Type II card, which is 5.0 mm thick, is
commonly used for memory, modems and LAN adapters
in laptops.  The Type III card is 10.5 mm thick and
is used to hold a hard disk, wireless transceiver
or other peripheral that needs more space.  One
Type III slot can hold one Type III or two Type II
cards.

   Toshiba introduced a 16 mm Type IV card, but
this has not been officially adopted by the PCMCIA.
Smaller cards will work in a Type IV slot.


             Card and Socket Services
In order to use a PCMCIA slot in the computer,
PCMCIA Card and Socket services must be loaded,
typically at system startup.  Card and Socket
Services software is generally included with
laptops that have PCMCIA slots.  It also comes
packaged with PCMCIA cards.

   Card Services manage system resources required
by the PCMCIA card, and, on PCs, determines which
IRQs and memory and I/O addresses are assigned.
They also manage hot swapping and pass changes in
events to higher-level drivers written for specific
PCMCIA cards.

   Card Services talk to Socket Services, which is
the lowest level of software that communicates
directly with the PCMCIA controller chips.  Socket
Services can be built into the system BIOS or added
via software.



PCradio
An IBM laptop designed for mobile use.  It is a
ruggedized machine that provides cellular, wireless
data radio (Ardis) and modem communications.



PCS
(Personal Communications Services)  Refers to a
variety of wireless services expected to emerge
after the U.S. Government auctions commercial
licenses in late 1994 and early 1995.  This two
gigahertz radio spectrum will be used for digital
transmission that will compete with cellular and
other wireless services.



PCTE
(Portable Common Tool Environment)  An ECMA
standard for exchanging data between CASE tools.
See CDIF.



PCX
A widely-used raster graphics file format developed
by Zsoft Corporation, Marietta, GA, that handles
monochrome, 2-bit, 4-bit, 8-bit and 24-bit color
and uses RLE to achieve compression ratios of
approximately 1.1:1 to 1.5:1.  Images with large
blocks of solid colors compress best under the RLE
method.



PD software
See public domain software.



PDA
(Personal Digital Assistant)  A handheld computer
that serves an an organizer, electronic book or
note taker and includes features such as pen-based
entry and wireless transmission to a cellular
service or desktop system.



PDES
(Product Data Exchange Specification)  A standard
format for exchanging data between advanced CAD and
CAM programs.  It describes a complete product,
including the geometric aspects of the images as
well as manufacturing features, tolerance
specifications, material properties and finish
specifications.  See IGES.



PDF file
(Portable Document Format file)  The file format
used by the Acrobat document exchange system.  See
Acrobat.



PDIAL
(Public Dialup Internet Access List)  A list of
Internet providers maintained by Peter Kaminsky.
To obtain PDIAL, send an e-mail message with the
appropriate phrase (see below) to the Internet
address:

         info-deli-server@netcom.com.


   If you are on CompuServe, send the message to

      >internet:info-deli-server@netcom.com



      Phrase                   To obtain

  Send PDIAL                 Latest edition
  Subscribe PDIAL            Future editions
  Subscribe Info-Deli-News   News about PDIAL





PDIP
(Plastic DIP)  A common type of DIP made of
plastic.



PDL
See page description language.



PDP
(Programmed Data Processor)  A minicomputer family
from Digital that started with the 18-bit PDP-1 in
1959.  Its $120,000 price was much less than the
million dollar machines of the time and 50 units
were built.

   In 1965, Digital legitimized the minicomputer
industry with the PDP-8, which sold for about
$20,000.  By the late 1970s, the PDP-8 processor
was put on a single chip and used in DECmate
workstations.

   Other PDPs were built, including 12-, 18- and
36-bit machines, the larger ones evolving into
DECsystem models.

   In 1970, Digital introduced the 16-bit PDP-11,
which became the most widely used minicomputer with
over 50,000 systems sold.  The PDP series was
followed by the VAX series in 1977; however, PDP-
11s are still made.



PDQ
(Parallel Data Query)  A query optimized for
massively parallel processors (MPPs).  The software
breaks down the query into pieces so that several
parts of the database can be searched
simultaneously.  See SMP.



PE
(1) (Phase Encoding)  An early magnetic encoding
method used on 1600bpi tapes in which a 1 is an up
transition and a 0 is a down transition in the
center of the bit cell.

(2) (Processing Element)  One of multiple CPUs in a
parallel processing system.

(3) (Professional Engineer)  An engineering degree.



PE format
(Portable Executable format)  A Win32 file format
for executable programs (EXEs and DLLs) supported
under Windows 3.1 Enhanced Mode (Win32s) and
Windows NT.



peek/poke
Instructions that view and alter a byte of memory
by referencing a specific memory address.  Peek
displays the contents; poke changes it.



peer
In communications, a functional unit that is on the
same protocol layer as another.



peer-to-peer communications
Communications in which both sides have equal
responsibility for initiating, maintaining and
terminating the session.  Contrast with master-
slave communications, in which the host determines
which users can initiate which sessions.  If the
host were programmed to allow all users to initiate
all sessions, it would look like a peer-to-peer
system to the user.



peer-to-peer network
A communications network that allows all
workstations and computers in the network to act as
servers to all other users on the network.
Dedicated file servers may be used, but are not
required as in a client/server network.

   Do not confuse this term with "peer-to-peer
communications."  A peer-to-peer network implies
peer-to-peer communications, but peer-to-peer
communications does not imply a peer-to-peer
network.  Don't you love the extensive thought and
analysis that goes into naming things in this
business in order to make the terms perfectly clear
and understandable!



pel
Same as pixel.



pen-based computing
Using a stylus to enter hand writing and marks into
a computer.  See gesture recognition.



pen plotter
See plotter.



Pen Windows
An extension to Windows that allows pen-based
computing.



PenPoint
An operating system from Go Corporation, Foster
City, CA, that provides a stylus (pen) interface
for hand-written input.  It uses a DOS-compatible
file system, but does not run DOS applications.
The direction, speed and order of the user's pen
strokes is analyzed for recognition.  See NUI.



Pentium
Currently, the fastest CPU in the Intel x86 line.
Pentium refers to the Pentium CPU chip or the PC
that uses it.  The Pentium is the successor to the
486 and was originally thought to be named the 586.
Depending on the clock speed, the Pentium runs from
half again to more than twice as fast as a 50MHz
486, while its floating point operations are up to
four times as fast.  Although its integer
performance rivals major RISC-based CPUs (Alpha,
HP-PA, MIPS, SPARC, etc.), its floating point
performance is generally slower.

   Pentium PCs are used as servers, CAD
workstations and for process-intensive
applications.  Remember though, today's leading
edge technology always becomes tomorrow's entry
level machine.

   The P24T is the code name for a scaled-down
Pentium used as to upgrade a 486 on motherboards
that have the required socket.


            Pentium CPU Technical Specs
It is a 32-bit multitasking microprocessor in a
273-pin PGA package.  Same registers and
operational modes as the 386.  Uses RISC design
techniques and obtains its speed by using two
internal 8K caches (one for code, the other for
data) and a "superscaler" dual pipeline
architecture, which executes two instructions in
the same clock cycle when it determines that the
next instruction is not dependent on the outcome of
the current one.

   The Pentium uses a 64-bit internal bus compared
to 32-bits on the 486.  PC makers use a variety of
high-speed bus and cache controllers to enhance
performance; for example, a 128-bit memory bus can
be used to extract data 128 bits at a time into the
external cache, which feeds it to the CPU 64 bits
at a time.

   The first Pentium models have internal and local
bus speeds of 60 and 66MHz.  These are expected to
be replaced by a 75MHz model in late 1994.

   The 90 and 100MHz models are faster and run
cooler, using only 3.3 volts instead of 5.  Local
bus speeds are 60 and 66Mhz.  Higher-speed models
are expected in 1995.

   The Pentium chip contains 3.1 million
transistors and uses .8 micron technology
(transistor elements are as small as .8 micron).



Pentium upgradable
The ability to be upgraded to a Pentium CPU.  486
motherboards designed for Pentium upgrades contain
a ZIF socket to make chip changing easy and are, in
theory, designed to support the higher speeds of
the Pentium chip.



People, Places and Things
The code name for the user interface in Taligent's
upcoming operating system.  It refers to the task
orientation of the interface in which a People
object might refer to a name and address, a Thing
could be a telephone or printer, and a Place could
be a location in the network.



PeopleSoft
(PeopleSoft, Walnut Creek, CA)  A software company
that specializes in human resource and accounting
packages for client/server environments.  All major
databases are supported.  The products are known
for their ease of modification and custom
development using the PeopleTools development
system.



PEP
(1) (Packet Exchange Protocol)  A Xerox protocol
used internally by NetWare to transport internal
Netware NCP commands (NetWare Core Protocols).  It
uses PEP and IPX for this purpose.  Application
programs use SPX and IPX.

(2) A high-speed modem protocol from Telebit
Corporation, Sunnyvale, CA, suited for cellular
phone use.



PEPPER board
An earlier family of high-resolution graphics
display boards for PCs from Number Nine Computer
Corporation, Lexington, MA.



performance ratings
See DOSmark, Winmark, SPECmark, Landmark rating,
Dhrystones, Whetstones, iCOMP, PLB and MIPS.



peripheral
Any hardware device connected to a computer, such
as a monitor, keyboard, printer, plotter, disk or
tape drive, graphics tablet, scanner, joy stick,
paddle and mouse.



Peripheral Component Interconnect
See PCI.



peripheral controller
See control unit (2).



peripheral device
See peripheral.



Perl
(Practical Extraction Report Language)  A UNIX
programming language written by Larry Wall that
combines syntax from several UNIX utilities and
languages.  Perl is designed to handle a variety of
system administrator functions.



permanent font
(1) A soft font that is kept in the printer's
memory until the printer is turned off.

(2) Same as internal font.



permanent memory
Same as non-volatile memory.



permanent virtual circuit
See PVC.



permutation
One possible combination of items out of a larger
set of items.  For example, with the set of numbers
1, 2 and 3, there are six possible permutations:
12, 21, 13, 31, 23 and 32.



perpendicular recording
See vertical recording.



persistence
In a CRT, the time a phosphor dot remains
illuminated after being energized.  Long-
persistence phosphors reduce flicker, but generate
ghost-like images that linger on screen for a
fraction of a second.



persistent link
See hot link.



personal communications services
See PCS.



personal computer
Synonymous with microcomputer, a computer that
serves one user.  It is used at home and in the
office for almost all applications traditionally
performed on larger computers.

   With the addition of a modem, it becomes a
terminal, capable of retrieving information from
other computers and online services worldwide.

   There are a variety of personal computers on the
market, priced from $300 to over $10,000.  Size is
based on its memory and disk capacity.  Speed is
based on the CPU that runs it, and output quality
is based on the resolution of its display screen
and printer.


       MAJOR SUPPLIERS OF PERSONAL COMPUTERS
The personal computer world is overwhelmingly
dominated by IBM PCs and IBM-compatible PCs.  There
are hundreds of vendors and thousands of models,
although all models fall into a handful of
categories (see PC).

   The next largest supplier is Apple Computer,
with its Macintosh family and Apple IIe.  The Apple
II has been widely used in schools, but is rapidly
giving way to the Macs.  Macintoshes are popular
with individuals and are increasingly being
purchased by large corporations.

   Both Atari and Commodore continue to carve out a
niche and are popular as home and small business
computers.  Each of them has support from software
vendors providing a rounded supply of applications.


         THE HISTORY OF PERSONAL COMPUTERS
The industry began in 1977, when Apple, Radio Shack
and Commodore introduced the first off-the-shelf
computers as consumer products.

   The first machines used an 8-bit microprocessor
with a maximum of 64K of memory and floppy disks
for storage.  The Apple II, Atari 500, and
Commodore 64 became popular home computers, and
Apple was successful in companies after the
VisiCalc spreadsheet was introduced.  However, the
business world was soon dominated by the Z80
processor and CP/M operating system, used by
countless vendors in the early 1980s, such as
Vector Graphic, NorthStar, Osborne and Kaypro.  By
1983, hard disks began to show up on these
machines, but CP/M was soon to be history.

   In 1981, IBM introduced the PC, an Intel 8088-
based machine, slightly faster than the genre, but
with 10 times the memory.  It was floppy-based, and
its DOS operating system from Microsoft was also
available for the clone makers (MS-DOS).  The 8088
was cleverly chosen so that CP/M software vendors
could convert to it easily.  They did!

   dBASE II was introduced in 1981 bringing
mainframe database functions to the personal
computer level and launching an entire industry of
compatible products and add-ons.  Lotus 1-2-3 was
introduced in 1982, and its refined interface and
combined graphics helped spur sales of the new
standard.

   The IBM PC was successfully cloned by Compaq and
unsuccessfully by others.  However, by the time IBM
announced the AT in 1984, vendors were effectively
cloning the PC and, as a group, eventually grabbed
the majority of the PC market.

   In 1983, Apple introduced the Lisa, a graphics-
based machine that simulated the user's desktop.
Although ahead of its time, Lisa was abandoned for
the Macintosh in 1984.  The graphics-based desktop
environment caught on with the Mac, especially in
desktop publishing, and the graphical interface, or
"gooey," (GUI) worked its way to the PC world with
Microsoft Windows, and, eventually Ventura
Publisher with its GEM interface.

   In 1986, the Compaq 386 ushered in the first
Intel 386-based machine.  In 1987, IBM introduced
the PS/2, its next generation of personal
computers, which added improved graphics, 3.5"
floppy disks and an incompatible bus to help fend
off the cloners.  OS/2, jointly developed by IBM
and Microsoft, was also introduced to handle the
new machines, but the early versions didn't catch
on.

   In the same year, more powerful Macintoshes were
introduced, including the Mac SE and Mac II, which
opened new doors for Apple.

   In 1989, the PC makers introduced 486-based
computers, and Apple gave us faster Macs, which it
has continued to do each year since.

   In 1990, Microsoft's introduced Windows 3.0,
which is rapidly becoming the most widely-used
graphical environment.  Software publishers are
developing Windows versions of all their products.

   In 1991, Microsoft and IBM decided to go it
alone each working on their own version of the
future PC operating system (IBM's OS/2 2.0 and
Microsoft's Windows NT).  OS/2 2.0 has been
moderately successful, and Windows NT is expected
to gain market share.

   1992 was the year of PC price cuts with all
major suppliers slashing prices to keep in line
with mail-order vendors, such as Gateway 2000.
Gateway, along with others, drove down the cost of
high-end systems by mail.  Prices keep getting
lower, machines keep getting faster.

   In 1993, Intel introduced its Pentium CPU,
successor to the 486.  It contains 3,100,000
transistors and is 300 times faster than the
original PC.  As a result, the 486 has become the
entry level PC.

   Inspired by Radio Shack's Model 100 in 1984 and
ignited by Toshiba and Zenith, the laptop market
provides a fascinating growth area in personal
computing.  More circuits are being stuffed into
less space, providing computing power on the go
that few would have imagined back in 1977.

   Just as the IBM and compatible PC world matures,
the joint venture of IBM, Apple and Motorola
arrives to challenge the personal computer industry
once again.  In 1993, IBM and Motorola introduced
their first PowerPC chips, an entirely new desktop
architecture that can be used to run almost all
existing applications while providing an advanced
platform for the future.  As of the beginning of
1995, over a million PowerPC chips have been
shipped as the CPUs in Apple PowerMacs and various
IBM RS/6000 workstations.


                    THE FUTURE
The personal computer industry sprang up without
any planning.  All of a sudden, it was there.
Machines were bought to solve individual problems,
such as automating a budget or typing a letter.

   However, in large organizations, the real data
exists in the mainframe, and it doesn't make sense
to have an employee retype the mainframe reports
into the micro in order to analyze and manipulate
it.  Personal computers can serve as invaluable
tools for the user when they are designed into the
fabric of the organization.  The major issue of the
1990s is to tie them together in LANs and
interconnect them with the company's minis and
mainframes.

   Fast personal computers are changing the
marketplace.  Not only do they compete with
minicomputer workstations, but, networks of these
machines are rapidly replacing traditional
minicomputer and mainframe systems.

   High-powered desktop computers will encourage
the development of more artificial intelligence
applications that are the backbone of the next
computing generation.  By the turn of the century,
you should be able to talk to your computer as
easily as typing on it.

   As stand-alone machines, personal computers have
placed creative capacity into the hands of an
individual that would have cost millions of dollars
less than 25 years ago.  It slowly but surely is
shifting the balance of power from the large
company to the small, from the elite to the masses,
from the wealthy to individuals of modest means.
The personal computer has revolutionized the
computer industry and the world.





personal digital assistant
See PDA.



personal information manager
See PIM.



Personal Intelligent Communicator
See PIC.



personal workstation
Same as personal computer or workstation.



PET computer
(Personal Electronic Transaction computer)  A CP/M
and floppy disk-based personal computer introduced
in 1977 by Commodore.  It was one of the three
first personal computers.



PEX
(PHIGS Extensions to X)  A set of 3-D extensions to
the X Window System.  See PHIGS and X Window.



PFA file
(Printer Font ASCII file)  A file that contains the
PostScript code for a Type 1 font.  See PFB and
PostScript.



PFB file
(Printer Font Binary file)  A file that contains
encrypted PostScript code for a Type 1 font.  It
was encrypted from a PFA (Printer Font ASCII) file,
which contains the ASCII PostScript description of
the font.  See PostScript.



PFS:First Choice
An integrated software package for PCs from SoftKey
International, Inc., Cambridge, MA, that provides
word processing, database, spreadsheet, graphics
and communications capabilities.



PFS:Write
See Professional Write.



PGA
(1) (Pin Grid Array)  A chip housing with high
density of pins (200 pins can fit in 1.5" square).
Used for large amounts of I/O, its underside looks
like a "bed of nails."

(2) (Programmable Gate Array)  A type of gate array
that is programmed by the customer.

(3) (Professional Graphics Adapter)  An early IBM
display standard for PCs (640x480x256) with 3-D
processing.  It was not widely used.



PGP
(Pretty Good Privacy)  An encryption program
developed by Phil Zimmermann that is based on RSA
public-key cryptography.  A version for personal,
non-business use is available on various BBSs and
Internet hosts.  A commercial version of PGP is
available for UNIX, DOS, Windows and Mac platforms
from Viacrypt, Phoenix, AZ.  See encyrption for an
explanation of public-key cryptography.



PgUp/PgDn keys
The Page Up and Page Down keys are typically used
to move text up and down one screenful, but they
can be programmed to do anything.



phase change recording
An optical recording technique that uses a laser to
create a bit by altering the crystalline structure
of a metallic surface.  The bit either reflects or
absorbs light when read.



phase encoding
See PE.



phase locked
A technique for maintaining synchronization in an
electronic circuit.  The circuit receives its
timing from input signals, but also provides a
feedback circuit for synchronization.



phase modulation
A transmission technique that blends a data signal
into a carrier by varying (modulating) the phase of
the carrier.  See modulate.



phase-shift keying
See DPSK.



PHIGS
(Programmer's Hierarchical Interactive Graphics
Standard)  A graphics system and language used to
create 2-D and 3-D images.  Like the GKS standard,
PHIGS is a device independent interface between the
application program and the graphics subsystem.

   It manages graphics objects in a hierarchical
manner so that a complete assembly can be specified
with all of its subassemblies.  It is a very
comprehensive standard requiring high-performance
workstations and host processing.



Phoenix BIOS
A PC-compatible ROM BIOS from Phoenix Technolgies,
Ltd., Norwood, MA.  Phoenix was the first company
to successfully mass produce the ROM BIOS for the
PC.



phone connector
(1) A plug and socket for a two or three-wire
coaxial cable used to plug microphones and
headphones into amplifiers.  The plug is a single,
nail-like " thick prong about 1" in length.  See
phono connector.

(2) A plug and socket for a telephone line,
typically the RJ-11 modular connector.



phone hawk
Slang for a person who calls up a computer via
modem and either copies or destroys data.



Phone Notes
See Lotus Notes.



phoneme
A speech utterance, such as "k," "ch," and "sh,"
that is used in synthetic speech systems to compose
words for audio output.



PhoneNET
Communications products from Farallon Computing,
Inc., Emeryville, CA, that extend LocalTalk
distances to 3,000 feet and use unshielded twisted
phone lines instead of shielded twisted pair.
Configurations include daisy chain, passive star as
well as active star topologies for both EtherTalk
and LocalTalk.  Optional Traffic Watch software
provides network management and administration.



Phong shading
In computer graphics, a technique developed by
Phong Bui Tuong that computes a shaded surface
based on the color and illumination at each pixel.
It is more accurate than Gouraud shading, but
requires much more extensive computation.



phono connector
Also called an RCA connector, a plug and socket for
a two-wire coaxial cable used to connect audio and
video components.  The Apple II has a video out
phono connector for a TV.  The plug is a 1/8" thick
prong that sticks out 5/16" from the middle of a
cylinder.  See phone connector.



phosphor
A rare earth material used to coat the inside face
of a CRT.  When struck by an electron beam, the
phosphor emits a visible light for a few
milliseconds.  In color displays, red, green and
blue phosphor dots are grouped as a cluster.



Photo CD
A CD imaging system from Kodak that digitizes 35mm
slides or negatives onto a CD-ROM disc.  The Photo
CD is created by photo finishers that have a Kodak
Picture Imaging Workstation.  It takes about a half
hour to put 100 photos (the maximum per disc) onto
the CD.  Each photographic-quality image
(2048x3072x24) compresses into six megabytes.  A
replica of each image in the form of contact prints
is also included.

   The minimum RAM required is 4MB, but 10MB is
needed in order to display an image in full
resolution.  Hardware requirements for Photo CDs
are a CD-ROM drive that conforms to the CD-ROM XA
standard.

   Earlier CD-ROM drives are single session drives,
which can only read the original set of images
recorded on the disc.  A multisession drive is
required to read Photo CD images that were added
after the original set.  Most new CD-ROM drives
provide multisession capability.

   Other formats include the Photo CD Portfolio,
which holds up to 800 TV-quality images (512x768),
the Pro Photo CD, which stores images from
professional format film (120, 4x5, etc.), the
Photo CD Catalog, which holds thousands of pictures
and the Photo CD Medical disk for storing film-
based images.

   There are a variety of software packages that
access Photo CD images, and increasingly, paint,
drawing and image enhancement programs are
importing the Photo CD format (PCD file).

   A Kodak Photo CD player is available that lets
you view the Photo CDs on your TV and also play
audio CDs.



photo editing
See image editing.



photocomposition
Laying out a printed page using electrophotographic
machines, such as phototypesetters and laser
printers.  See page makeup and pagination.



photoconductor
The type of material typically used in a
photodetector.  It increases its electrical
conductivity when exposed to light.



photodetector
A device that senses the light pulses in an optical
fiber and converts them into electrical pulses.  It
uses the principle of photoconductivity, which is
exhibited in certain materials that change their
electrical conductivity when exposed to light.



photolithography
A lithographic technique used to transfer the
design of the circuit paths and electronic elements
on a chip onto a wafer's surface.  A photomask is
created with the design for each layer of the chip.
The wafer is coated with a light-sensitive film
(photoresist) that is hardened when exposed to
light shining through the photomask.  The wafer is
then exposed to an acid bath (wet processing) or
hot ions (dry processing), and the unhardened areas
are etched away.



photomask
An opaque image on a transluscent plate that is
used as a light filter to transfer an image from
one device to another.  See chip.



photomicrography
Photographing microscopic images.



photon
A unit of energy.  Elementary particle of
electromagnetic radiation (light, radio waves, X-
rays, etc.).



photonics
The science of building machine circuits that use
light instead of electricity.



photooptic memory
A storage device that uses a laser beam to record
data onto a photosensitive film.



photorealistic
Having the image quality of a photograph.



photorealistic image synthesis
In computer graphics, a format for describing a
picture that depicts the realism of the actual
image.  It includes such attributes as surface
texture, light sources, motion blur and
reflectivity.



photoresist
A film used in photolithography that temporarily
holds the pattern of a circuit path or microscopic
element of a chip.  When exposed to light, it
hardens and is resistant to the acid bath that
washes away the unexposed areas.



photosensor
A light-sensitive device that is used in optical
scanning machinery.



Photoshop
See Adobe Photoshop.



phototypesetter
A device that generates high-resolution text
directly onto a photo-sensitive material.  Input
comes from the keyboard, or via disk, tape or
modem.  The output is a paper-like or transparent
film that is processed into a camera-ready master
for printing.

   Phototypesetters employ various light
technologies.  Older machines pass light through a
spinning font photomask, then through lenses that
create the point size and onto film.  Others create
images on CRTs and expose the film.  Modern
imagesetters use lasers to generate the image
directly onto the film.

   The phototypesetter was originally the only
machine that could handle multiple fonts and text
composition such as kerning.  Today, desktop laser
printers are used for many typesetting jobs and are
quickly advancing in resolution, although the 1270
and 2540 dpi resolutions of the phototypesetter
combined with the high-quality of film still
provide the finest printing.

   Phototypesetters that handle both text and
graphics are called imagesetters.



physical
Refers to devices at the electronic, or machine,
level.  Contrast with logical.  See logical vs
physical.



physical address
The actual, machine address of an item or device.



physical format
See record layout and low-level format.



physical link
(1) An electronic connection between two devices.

(2) In data management, a pointer in an index or
record that refers to the physical location of data
in another file.



physical lock
A device that prevents access to data, such as a
key lock switch on a computer or a file protection
mechanism on a floppy disk.  Contrast with logical
lock.



Physical Unit
See PU.



PIC
(1) (PICture)  A file extension used for graphics
formats.  Lotus PIC is a vector format for 1-2-3
charts and graphs.  Videoshow PIC is a vector
format that is a subset of the NAPLPS standard.

(2) (Personal Intelligent Communicator)  A hand-
held computer from General Magic that uses 3" CD-
ROMs and has a HyperCard-like interface.  Cellular
phone and wireless communications for networks,
radio and TV are planned.

(3) (Programmable Interrupt Controller)  An Intel
8259A chip that controls interrupts.  Starting with
the 286-based AT, there are two PICs in a PC,
providing a total of 15 usable IRQs.  The PIC has
been superseded by an Advanced Programmable
Interrupt Controller, or 82489DX chip, that is
enhanced for multiprocessing.  See IRQ.



pica
(1) In word processing, a monospaced font that
prints 10 characters per inch.

(2) In typography, about 1/6th of an inch (0.166")
or 12 points.



Pick System
A multiuser operating environment and database
management system (DBMS) from Pick Systems, Inc.,
Irvine, CA, that runs on a variety of platforms,
including x86, 680x0 and RS/6000.  It is highly
praised for its ease of use and flexibility.  Most
customers use only the DBMS portion of the Pick
System today.

   It was originally developed by Richard Pick, who
created a system for the U.S. Army while working at
TRW Corporation.  He later transformed it into the
Reality operating system for Microdata and then
obtained the right to license it to other vendors.



pico
One trillionth or 10 to the -12th power.



picosecond
One trillionth of a second.  Pronounced "pee-co-
second."



PICT
(PICTure)  A Macintosh graphics file format that
stores images in the QuickDraw vector format.  When
PICT files are converted to the PC, they use the
.PCT file extension.



picture
In programming, a pattern that describes the type
of data allowed in a field or how it will print.
The pattern is made up of a character code for each
character in the field; for example, 9999 is a
picture for four numeric digits.  A picture for a
telephone number could be (999) 999-9999.  XXX999
represents three alphanumerics followed by three
numerics.  Pictures are similar but not identical
in all programming languages.



picture element
See pixel.



Picture Level Benchmark
See PLB.



Picturephone
The proposed video/telephone introduced by AT&T at
the 1964 World's Fair (New York).   Many thought it
would flourish by the end of the 1980s.  Realtime
video is expected to flourish in the late 1990s.



PID
(1) (Process IDentifier)  A temporary number
assigned by the operating system to a process or
service.

(2) (Proportional Integral Derivative)  A
controller used to regulate a continuous process
such as grinding or cooking.



pie chart
A graphical representation of information in which
each unit of data is represented as a pie-shaped
piece of a circle.  See business graphics.



piezoelectric
The property of certain crystals that oscillate
when subjected to electrical pressure (voltage).



PIF
(Program Information File)  A Windows data file
used to hold requirements for DOS applications
running under Windows.  Windows comes with a
variety of PIFs, but users can edit them and new
ones can be created with the PIF editor if a DOS
application doesn't work properly.  An application
can be launched by clicking on its PIF.



piggyback board
A small printed circuit board that plugs into
another circuit board in order to enhance its
capabilities.  It does not plug into the
motherboard, but would plug into the boards that
plug into the motherboard.



PIL
(Publishing Interchange Language)  A standard for
document interchange that defines the placement of
text and graphics objects on the page.  It does not
address the content of the objects.



PILOT
(Programmed Inquiry Learning Or Teaching)  A high-
level programming language used to generate
question-and-answer courseware.  A version that
incorporates turtle graphics runs on Atari personal
computers.



PIM
(Personal Information Manager)  Software that
organizes random information for fast retrieval.
It provides a combination of features such as a
telephone list with automatic dialing, calendar,
scheduler and tickler.  A PIM lets you jot down
text for any purpose and retrieve it based on any
of the words you typed in.  PIMs vary widely, but
all of them attempt to provide methods for managing
information the way you use it on a daily basis.



pin
(1) The male lead on a connecting plug (serial
port, monitor cable, keyboard connector, etc.) or
the spiderlike foot on a chip.  Each pin is plugged
into a socket to complete the circuit.

(2) (PIN) (Personal Identification Number)  A
personal password used for identification purposes.

(3) (PIN) (Processor Independent NetWare)  A
version of NetWare designed for portability to
multiple platforms starting at the feature level of
NetWare 4.1.  A PIN version of NetWare is expected
to be released in 1995 for the PowerPC.



pin compatible
Refers to a chip or other electronic module that
can be plugged into the same socket as the chip or
module it is replacing.



pin feed
A method for moving continuous paper forms.  Pins
at both ends of a rotating platen or tractor engage
the forms through pre-punched holes at both sides.



pin grid array
See PGA.



pinch roller
A small, freely-turning wheel in a tape drive that
pushes the tape against a motor-driven wheel in
order to move it.



pincushioning
A screen distortion in which the sides bow in.
Contrast with barrel distortion.




PING
(Packet INternet Groper)  An Internet utility used
to determine whether a particular IP address is
online.  It is used to test and debug a network by
sending out a packet and waiting for a response.



ping pong
(1) A half-duplex communications method in which
data is transmitted in one direction and
acknowledgement is returned at the same speed in
the other.  The line is alternately switched from
transmit to receive in each direction.  Contrast
with asymmetric modem.

(2) To go in one direction and then in the other.



ping-pong buffer
See double buffering.



Pink
The code name for Taligent's object-oriented
operating system.  See Taligent.



pinouts
The description and purpose of each pin in a
multiline connector.



PIP
(Peripheral Interchange Program)  A CP/M utility
program used to copy files.



pipe
A shared space that accepts the output of one
program for input into another.  In DOS, OS/2 and
UNIX, the pipe command is a vertical line (|).  For
example, in DOS and OS/2, the statement, dir | sort
directs the output of the directory list to the
sort utility.  See DOS filters & pipes and DOS
redirection.



pipeline processing
A category of techniques that provide simultaneous,
or parallel, processing within the computer  It
refers to overlapping operations by moving data or
instructions into a conceptual pipe with all stages
of the pipe processing simultaneously.  For
example, while one instruction is being executed,
the computer is decoding the next instruction.  In
vector processors, several steps in a floating
point operation can be processed simultaneously.



piracy
The illegal copying of software for personal or
commercial use.



pitch
The number of printed characters per inch.  With
proportionally spaced characters, the pitch is
variable and must be measured as an average.  See
dot pitch.



pixel
(PIX [picture] ELement)  The smallest element on a
video display screen.  A screen is broken up into
thousands of tiny dots, and a pixel is one or more
dots that are treated as a unit.  A pixel can be
one dot on a monochrome screen, three dots (red,
green and blue) on color screens, or clusters of
these dots.

   For monochrome screens, the pixel, normally
dark, is energized to different light intensities,
creating a range from dark to light.  For color,
each red, green and blue dot is energized to
different intensities, creating a range of colors
perceived as the mixture of these dots.  Black is
all three dots off, white is all three dots on, and
grays are even intensities of each color.

   The number of bits assigned to each pixel in its
associated digital memory determines the number of
shades and colors that can be represented.  The
most economical system is monochrome in which one
bit is used per pixel (on or off).  In the most
elaborate color displays, which use up to four full
bytes for each of the red, green and blue dots,
each pixel can display billions of different
shades.  Considering that a high-resolution screen
may use a million pixels, many megabytes of memory
would have to be reserved to hold such an image.



pixel graphics
Same as raster graphics.



PixelPaint
A Macintosh drawing program from SuperMac
Technology, Sunnyvale, CA, that is known for its
extensive paint palette and color mixing schemes.



PK software
Popular PC shareware compression programs from
PKWARE Inc., Brown Deer, WI (PK stands for Phil
Katz).  PKZIP compresses files into a ZIP file and
PKUNZIP decompresses them.  PKSFX compresses files
into a self-extracting EXE file that decompresses
when loaded and doesn't require the PKUNZIP
program.  ZIP2EXE creates the self-extracting file
from an existing ZIP file.

   PKLITE is a program that compresses only EXE and
COM program files.  Unlike ZIP'd files, which are
compressed for archiving or distribution and
decompressed upon installation, PKLITE'd files stay
compressed all the time and decompress
automatically when loaded.

   PKWARE also provides its data compression
library (DCL) to developers that want to include
realtime compression and decompression of data in
their applications.

   The Pkzip programs are also available on other
platforms from a third party.  See Pkzip cross
platform.

   PKARC and PKXARC were previous compression
programs that are no longer supported.  See Pkzip
abc's.



Pkunzip
See PK software and Pkzip abc's.



Pkzip
See PK software and Pkzip abc's.



Pkzip abc's
Following are some basic examples to learn how to
zip and unzip files.  All files can be compressed.
The amount of compression depends on the file
content.  Text and data files compress well.  So do
many .EXE files.  Graphics files vary depending on
the graphics format used.

                  Version Numbers
There are two major versions of Pkzip/Pkunzip that
are in widespread use: Version 1.1 and 2.0.  Files
zipped with Version 1.1 can be unzipped with either
version, but files zipped under 2.0 cannot be
unzipped with 1.1.  The version number is displayed
on screen as the program starts processing.



   The format of a PKZIP command is:

           PKZIP    TO    FROM


   To zip everything in the current directory,
creating a MUCHSTUF.ZIP file, type:

           pkzip muchstuf *.*


   To zip everthing in the current directory,
except the .BAK files, use the -x (eXclude) switch.
There can be NO spaces between the -x and the file
description that follows it; for example:

        pkzip muchstuf *.* -x*.bak


   To zip all the .DBF files in the current
directory, creating a DATA.ZIP file, type:

          pkzip data *.dbf


   To zip files onto a floppy disk, just add the
drive letter; for example:

          pkzip b:data *.dbf


   To zip selected files, just name them
sequentially.  Use path names if the files are not
in the current directory.  For example, presuming
SALES.DBF is in the current directory, but CREDIT
is not, type:

    pkzip data sales.dbf \123\credit.wk1



UNZIPPING INTO THE CURRENT DIRECTORY
The format of a PKUNZIP.EXE command is:

     PKUNZIP    FROM    (selected files)


   To unzip DATA.ZIP in the current directory,
type:

               pkunzip data


   To unzip selected files from the floppy into
your current directory, just name them
sequentially; for example:

   C:\ANYWHERE>pkunzip b:data doc1 doc3 doc7


   The .ZIP file still remains intact after
exploding.  Delete it if you have no further use
for it.


UNZIPPING FROM A FLOPPY INTO THE CURRENT DIRECTORY
To unzip DATA.ZIP from the B: drive into the
current directory, type:

        C:\ANYWHERE>pkunzip b:data



CREATING A SELF-EXTRACTING ARCHIVE
Once a zip file has been created, it can be used to
create a self-extracting archive with the
ZIP2EXE.EXE utility.  It combines PKUNZIP.EXE with
the .ZIP file creating a new executable program
that unzips automatically when you run it.

   For example, to create the DATA.EXE self-
extracting archive from the DATA.ZIP file, type:

             zip2exe data


   To run DATA.EXE, simply type the program name
like you would any executable file:

                 data


   To extract selected files from a self-extracting
archive on a floppy, just name the files
sequentially.  For example, to pull out DOC5 and
DOC9 from DOCUMENT.EXE on the B: drive into the
current directory, type:

      C:\ANYWHERE>b:document doc5 doc9



UPDATING FILES
You can use PKZIP to update only files that have
been changed.  For example, to update all the .DOC
files on a floppy archive called DOCUMENT.ZIP from
the current directory, type the following:

       pkzip b:document *.doc -u -bc:


   The -u switch means zip only files that have a
more recent date than the ones on the target drive,
in this case the floppy drive B:.  The -bc: switch
indicates that the C: drive should be used if extra
room is required to do the compressing.  This is a
good safeguard if you are zipping files onto
floppies, otherwise the operation will stop if
there is not enough room.

   In the above example, new .DOC files that do not
already exist in the DOCUMENT.ZIP file would also
be added.  To update only files that already exist
in the zip file without adding new ones, use the -f
(Freshen) switch instead of the -u (Update) switch.



ADDING FILES
You can add one or more files to an existing zip
file.  For example, to add the file LETTER.DOC to
the DOCUMENT.ZIP file, type:

          pkzip document letter.doc



DELETING FILES
You can delete one or more files from an existing
zip file by using the -d switch.  For example, to
delete LETTER.DOC from DOCUMENT.ZIP, type:

         pkzip document letter.doc -d



   Ŀ
        End of PKZIP/PKUNZIP tutorial.     
   



Pkzip cross platform
Pkzip, Pkunzip and PKWARE's Data Compression
Library (DCL) are available on MVS, AS/400 and
various UNIX platforms, including HP 9000, ICL,
MIPS, RS/6000, SPARC and VAX.  This allows files,
for example, that are Zip'd in DOS to be Unzip'd on
a UNIX machine.  For information, contact Ascent
Solutions, Inc., 10460 Miamisburg-Springboro Pike,
Dayton OH 45342, 513/885-2031.



PL/I
(Programming Language 1)  A high-level IBM
programming language introduced in 1964 with the
System/360 series.  It was designed to combine
features of and eventually supplant COBOL and
FORTRAN, which never happened.  A PL/I program is
made up of procedures (modules) that can be
compiled independently.  There is always a main
procedure and zero or more additional ones.
Functions, which pass arguments back and forth, are
also provided.



PL/M
(Programming Language for Microprocessors)  A
dialect of PL/I developed by Intel as a high-level
language for its microprocessors.  PL/M+ is an
extended version of PL/M, developed by National
Semiconductor for its microprocessors.



PLA
(Programmable Logic Array)  A programmable logic
chip (PLD) technology from Philips/Signetics.



plaintext
Normal text that has not been encrypted and is
readable by text editors and word processors.
Contrast with ciphertext.



planar
A technique developed by Fairchild Instruments that
creates transistor sublayers by forcing chemicals
under pressure into exposed areas.  Planar
superseded the mesa process and was a major step
toward creating the chip.



planar area
In computer graphics, an object that has
boundaries, such as a square or polygon.



planning system
See spreadsheet and financial planning system.



plasma display
Also called gas discharge, a flat-screen technology
that contains an inert ionized gas sandwiched
between x- and y-axis panels.  A pixel is selected
by charging one x- and one y-wire, causing the gas
in that vicinity to glow a bright orange.



plastic LCC
See PLCC.



plastic quad flatpack
See PQFP.



platen
A long, thin cylinder in a typewriter or printer
that guides the paper through it and serves as a
backstop for the printing mechanism to bang into.



platform
The hardware architecture of a particular CPU model
or computer family.  For example, the x86, or PC,
is the world's largest hardware platform.  VAX,
AS/400 and SPARC are other examples (see hardware
platforms for a complete list).

   The term is also used to refer to the operating
system, such as DOS, Windows or UNIX.  In such
cases, the hardware is implied, because programs
presented to the computer for execution must talk
to the both the operating system and the computer's
machine language.

   When a program is said to be "for Windows," or
"it supports Windows," it means it runs on a PC.
However, if Windows were to become widely used on
other platforms, then "Windows for x86" and
"Windows for PowerPC" are the designations that
would have to be used to make it clear what a
program actually runs on.

   The phrase "runs on the UNIX platform" is even
more ambiguous, since some variation of UNIX runs
on everything.  Such a phrase would imply the major
UNIXs.  However, if you need to know what runs on
what, you need more details.  Which hardware
platforms?  Which version of UNIX?

   The terms platform and environment are used
interchangeably.  See environment.



PLATO
(Programmed Logic for Automatic Teaching
Operations)  Developed by Donald Bitzer and
originally marketed by CDC, it was the first CBT
system to combine graphics and touch-sensitive
screens for interactive training.



platter
One of the disks in a disk pack or hard disk drive.
Each platter provides a top and bottom recording
surface.  See magnetic disk.



PLB
(Picture Level Benchmark)  The Graphics Performance
Characterization (GPC) committee's benchmark,
available through NCGA, for measuring graphics
workstation performance.  The Benchmark Interface
Format (BIF) defines the PLB format, the Benchmark
Timing Methodology (BTM) performs the test and the
Benchmark Reporting Format (BRF) generates results
in GPCmarks.  Image quality is not rated.



PLC
(Programmable Logic Controller)  A computer used in
process control applications.  PLC microprocessors
are typically RISC-based and are designed for high-
speed, realtime and rugged industrial environments.



PLCC
(Plastic LCC)  A widely-used type of leaded chip
carrier.  See LCC.



PLD
(Programmable Logic Device)  A logic chip that is
programmed at the customer's site.  There are a
wide variety of PLD techniques; however, most PLDs
are compatible with the PAL method from Advanced
Micro Devices.

   The PLD is not a storage chip like a PROM or
EPROM, although fuse-blowing techniques are used.
It contains different configurations of AND, OR and
NOR gates that are "blown" together.  Contrast with
gate array, which requires a manufacturing process
to complete the programming.



plot
To create an image by drawing a series of lines.
In programming, a plot statement creates a single
vector (line) or a complete circle or box that is
made up of several vectors.



plotter
A graphics printer that draws images with ink pens.
It requires data in vector graphics format, which
makes up an image as a series of point-to-point
lines.  See flatbed plotter and drum plotter.



Plotter in a Cartridge
HPGL emulation in a cartridge for laser printers
from Pacific Data Products, San Diego, CA.



PLP
(Presentation Level Protocol)  A North American
standard protocol for videotex.



plug and hope
Refers to the frustration of installing additional
peripheral devices on a PC.  See plug and tell,
plug and play and PC conflicts.



plug and play
(1) The ability to add a new component and have it
work without having to perform any technical
analysis or procedure.

(2) (Plug and Play)  Also known as PnP, it is a
Microsoft/Intel standard for PCs incorporated into
new expansion cards and upcoming operating systems
(Windows 95, etc.).  It eliminates the frustration
of configuring the system when adding new
peripherals.  IRQ and DMA settings and I/O and
memory addresses self configure on startup.

   Implementing Plug and Play requires a system
BIOS on the motherboard that supports Plug and Play
as well as Plug and Play expansion cards.  Plug and
Play can also be retrofitted to older systems by
installing the DWCFGMG.SYS driver and using new
Plug and Play cards.

   A Plug and Play system will also assist with
older non-Plug and Play cards.  When a non-Plug and
Play card is installed, the ISA Configuration
Utility, or ICU, will check its list of known card
requirements and recommend the appropriate
settings.  If the card is not in the list, it will
also help the user determine the correct settings,
providing a "plug and tell" capability.

   In time, when all systems and cards are Plug and
Play, we can forget the "plug and hope" days of
installing PC peripherals.  See PC conflicts.



plug and tell
Refers to installing new peripheral devices in a PC
and using a utility program that helps to configure
the device properly.  Micro Channel and EISA bus
installations, as well as installing a non-Plug and
Play card in a Plug and Play machine, are plug and
tell because they analyze the system and recommend
which settings should be made.

   Plug and tell is between the "plug and hope" of
installing a legacy ISA card in a PC and the "plug
and play" of installing an ISA Plug and Play card
in a Plug and Play machine.



plug compatible
Hardware that is designed to perform exactly like
another vendor's product.  A plug compatible CPU
runs the same software as the machine it's
compatible with.  A plug compatible peripheral
works the same as the device it's replacing.



plugboard
A board containing a matrix of sockets used to
program early tabulating machines and computers.
Each wire directs a column of data from source to
destination, or it functions as a switch by closing
a circuit.  Complicated programs looked like
"mounds of spaghetti."



plugs & sockets
The physical connectors used to link together all
variety of electronic devices.  See DB-9, RS-232,
and Centronics.



PM
See preventive maintenance, Presentation Manager,
Program Manager and phase modulation.



PMMU
(Paged Memory Management Unit)  A virtual memory
chip for the 68020 processor (it is built in on the
68030), which is required to run A/UX on the Mac or
any 68020 platform running hardware virtual memory.



PMOS
(Positive channel MOS)  Pronounced "P moss."  A
type of microelectronic circuit in which the base
material is positively charged.  PMOS transistors
were used in the first microprocessors and are
still used in CMOS.  They are also used in low-cost
products (calculators, watches, etc.).



PMS
(Pantone Matching System)  A color matching system
that has a number assigned to over 500 different
colors and shades.  This standard for the printing
industry has been built into many graphics and
desktop publishing programs to ensure color
accuracy.



PnP
See Plug and Play.



POA
See PowerOpen Association.



pocket computer
A hand-held, calculator-sized computer that runs on
batteries.  It can be plugged into a personal
computer for data transfer.



POE
See PowerOpen.



point
(1) To move the cursor onto a line or image on
screen by rolling a mouse across the desk or by
pressing the arrow keys.

(2) In typography, a unit equal to 1/72nd of an
inch, used to measure the vertical height of a
printed character.



point and shoot
To select a menu option or activate a function by
moving the cursor onto a line or object and
pressing the return key or mouse button.



point of presence
See POP.



point of sale
Capturing data at the time and place of sale.
Point of sale systems use personal computers or
specialized terminals that are combined with cash
registers, optical scanners for reading product
tags, and/or magnetic stripe readers for reading
credit cards.

   Point of sale systems may be online to a central
computer for credit checking and inventory
updating, or they may be stand-alone machines that
store the daily transactions until they can be
delivered or transmitted to the main computer for
processing.



point-to-multipoint
A communications network that provides a path from
one location to multiple locations (from one to
many).



point-to-point
A communications network that provides a path from
one location to another (point A to point B).



Point-to-Point Protocol
See PPP.



pointer
(1) In database management, an address embedded
within the data that specifies the location of data
in another record or file.

(2) In programming, a variable that is used as a
reference to the current item in a table (array) or
to some other object, such as the current row or
column on screen.

(3) An on-screen symbol used to identify menu
selections or the current screen location.  It is
moved by a mouse or other pointing device.



pointing device
An input device, such as a mouse or graphics
tablet, used to move the cursor on screen or to
draw an image.



Poisson distribution
A statistical method developed by the 18th century
French mathematician S. D. Poisson, which is used
for predicting the probable distribution of a
series of events.  For example, when the average
transaction volume in a communications system can
be estimated, Poisson distribution is used to
determine the probable minimum and maximum number
of transactions that can occur within a given time
period.



poke
See peek/poke.



polarity
(1) The direction of charged particles, which may
determine the binary status of a bit.

(2) In micrographics, the change in the light to
dark relationship of an image when copies are made.
Positive polarity is dark characters on a light
background; negative polarity is light characters
on a dark background.



polarized
A one-way direction of a signal or the molecules
within a material pointing in one direction.



Polish notation
A method for expressing a sequence of calculations
developed by the Polish logician Jan Lukasiewicz in
1929.  For example, A(B+C) would be expressed as
* A + B C.  In reverse Polish notation, it would be
A B C + *.



polling
A communications technique that determines when a
terminal is ready to send data.  The computer
continually interrogates its connected terminals in
a round robin sequence.  If a terminal has data to
send, it sends back an acknowledgement and the
transmission begins.  Contrast with interrupt-
driven, in which the terminal generates a signal
when it has data to send.



polling cycle
One round in which each and every terminal
connected to the computer or controller has been
polled once.



polygon
In computer graphics, a multi-sided object that can
be filled with color or moved around as a single
entity.



polyhedron
A six- or more-sided object.  A group of connected
polygons.



polyline
In computer graphics, a single entity that is made
up of a series of connected lines.



polymorphic tweening
See tweening.



polymorphic virus
A virus that changes its binary pattern each time
it infects a new file to keep it from being
identified.  See stealth virus.



polymorphism
Meaning many shapes.  In object-oriented
programming, the ability of a generalized request
(message) to produce different results based on the
object that it is sent to.



polyphonic
The ability to play back some number of musical
notes simultaneously.  For example, 16-voice
polyphony means a total of 16 notes, or waveforms,
can be played concurrently.



Polyvision
A flat panel display from Alpine Polyvision Inc.
that uses a plastic film of metal ions sandwiched
between horizontal and vertical electrodes.  Where
current intersects, the metal ions turn black.



pop
(1) See push/pop.

(2) (Point of Presence)  The place where a line
from a long distance carrier (IXC) connects to the
line of the local telephone company or to the user
if the local company is not involved.

(3) (Post Office Protocol)  A protocol commonly
used by an electronic mail program to download
messages from a mail server on the Internet.



POP-11
(Package for Online Programming)  A general-purpose
programming language with list processing and
compiler writing functionality from SD-Scicon PLC.



pop-down menu
See pull-down menu.



populate
To plug in chips or components into a printed
circuit board.  A fully populated board is one that
contains all the devices it can hold.



popup
(1) A type of menu called for and displayed on top
of the existing text or image.  When the item is
selected, the menu disappears and the screen is
restored.

(2) Same as TSR.



port
(1) A pathway into and out of the computer.    The
serial and parallel ports on a personal computer
are external sockets for plugging in communications
lines, modems and printers.  On a front end
processor, serial ports connect to communications
lines and modems.

(2) To convert software to run in a different
computer environment.



port address
A physical identification of an I/O port.  See I/O
address.



port expander
A device that connects several lines to one port in
the computer.  The port may be one interface type
that is expanded into several by this device (see
port multiplier), or it may contain multiple
interfaces.  For example, a port expander may
provide additional serial and parallel ports on a
laptop.


port multiplier
Also called a fan-out, it is a device that expands
one port into several.  For example, an Ethernet
port multiplier allows multiple stations to be
connected to a 10Base5 cable via one transceiver
tap.  Otherwise, each station requires its own
transceiver.



port replicator
A device used to connect peripherals to a laptop.
All the desktop devices are permanently plugged
into the port replicator, which quickly connects to
the laptop.  It is like a docking station without
expansion slots.



portability
See portable.



portable
Refers to software that can be easily moved from
one type of machine to another.  It implies a
product that has a version for several hardware
platforms or has built-in capabilities for
switching between them.  However, a program that
can be easily converted from one machine type to
another is also considered portable.



portable computer
A personal computer that can be easily transported.
Compared to desktop models, it has limited
expansion slots and disk capacity.

   The first portable was the Osborne I, a CP/M
machine that was soon followed by many others, such
as the Kaypro and Otrona's Attache.  In late 1982,
Compaq introduced the first MS-DOS portable.  See
laptop computer, notebook computer and pocket
computer.



Portable NetWare
An OEM version (C source code) of Novell's NetWare
operating system that can be compiled for a
specific vendor's machine.



porting
See port.



portrait
An orientation in which the data is printed across
the narrow side of the form.

      Ŀ
                   Ŀ
      Portrait      Landscape  
                               
                   
      





POS
See point of sale.



POSIT
(Profiles for Open Systems Internetworking
Technolgoies)  A set of voluntary standards
published by the National Institute of Standards
and Technology (NIST) for network equipment
purchased by the U.S. government.  It is the
successor to GOSIP.



positive logic
The use of low voltage for a 0 bit and high voltage
for a 1 bit.  Contrast with negative logic.



POSIX
(Portable Operating System Interface for UNIX)  An
IEEE 1003.1 standard that defines the language
interface between application programs and the UNIX
operating system.  Adherence to the standard
ensures compatibility when programs are moved from
one UNIX computer to another.  POSIX is primarily
composed of features from UNIX System V and BSD
UNIX.



POST
(Power On Self Test)  A series of built-in
diagnostics that are performed when the computer is
first started.  Proprietary codes are generated
(POST codes) that indicate test results.  See
diagnostic board.



Post Office Protocol
See POP.



postfix notation
See reverse Polish notation.



postprocessor
Software that provides some final processing to
data, such as formatting it for display or
printing.



PostScript
A page description language from Adobe Systems,
Inc., Mountain View, CA, that is used extensively
on Macs and PCs as well as workstations, minis and
mainframes.  It is the de facto standard in
commercial typesetting and printing houses.  Most
all accept and may even require PostScript files as
electronic input.

   PostScript commands do not drive the printer
directly.  They are language statements in ASCII
text that are translated into the printer's machine
language by a PostScript interpreter built into the
printer.  Fonts are scaled to size by the
interpreter, thus eliminating the need to store a
variety of font sizes on disk.

   PostScript Level 2, downward compatible with
original PostScript, adds data compression and
enhancements, especially for color printing.

   PostScript fonts come in Type 1 and Type 3
formats, and Adobe makes only Type 1.  Type 1 fonts
are widely used and are made by other companies as
Adobe later made the format public.

   Type 1 fonts are encrypted and compressed and
also allow for hints, which improve the appearance
of text at 300 dpi and lower resolutions.  Type 1
fonts use a simpler, more efficient command
language than Type 3.  With Adobe Type Manager,
Type 1 fonts can also be used on non-PostScript
printers.  See Adobe Type Manager.

   Type 3 fonts do not use encryption or hints, but
can use the entire PostScript language to create
complex designs.  They can also be bitmaps.  Type 3
fonts are not widely used; however, in order to
speed up printing small fonts on PostScript
printers, Windows 3.1 creates Type 3 bitmaps from
its TrueType outlines.


                 Type 1 Font Files
Type 1 fonts are distributed by Adobe as two files.
One contains the outlines, and the other contains
the font metrics, which includes character widths
and heights and kerning values.

   Type 1 font distribution disks for Windows
contain PFB, AFM and INF files.  The PFB (Printer
Font Binary) outline files are copied to the hard
disk, and the AFM (Adobe Font Metric) files are
converted into PFM (Printer Font Metric) files on
the hard disk.  INF files contain information that
the font installer requires.

   A font generator, called Font Foundry, is
available from Adobe that converts Type 1 outlines
into bitmaps for HP printers (.SFP and .SFL files)
and screen fonts for DOS applications, such as
WordPerfect and the GEM version of Ventura
Publisher.

   Type 1 font distribution disks for the Mac
contain outline and metric files that are copied
onto the hard disk.  For example, a Helvetica font
would have an outline file named "Helve" and a font
metrics file named "Helvetica."  The icon for the
font metrics file looks like a suitcase, and is
often called the "suitcase file."  A Helve.AFM file
may also be included on the distribution disk.

   PostScript font distribution disks for UNIX
contain both AFM and PFA (Printer Font ASCII)
files.  The PFA files contain the PostScript ASCII
code of the outline.





pot
See potentiometer.



potentiometer
A device that controls the amount of current that
flows through a circuit, such as a volume switch on
a radio.



POTS
(Plain Old Telephone Service)  The traditional
analog telephone network.



power
(1) See computer power.

(2) (POWER) (Performance Optimization With Enhanced
RISC)  A RISC-based CPU architecture from IBM used
in its RS/6000 workstation and parallel computer
line.  The PowerPC, enhanced by Motorola and Apple,
is a single-chip version of the POWER architecture.



power adapter
A transformer that converts AC power from a wall
outlet into the DC power required by an electronic
device.



power down
To turn off the computer in an orderly manner by
making sure all applications have been closed
normally and then shutting the power.



power good
A signal transmitted from the power supply to the
circuit board indicating that the power is stable.
For various power supply definitions, see power
supply.



Power Macintosh
See PowerMac.



power management
Maximizing battery power by using low-voltage CPUs
and slowing down components when they are inactive.
See SMM.



Power PC
See PowerPC.



power platform
Refers to a mature, high-speed computer system.



power supply
An electrical system that converts AC current from
the wall outlet into the DC currents required by
the computer circuitry.  In a personal computer,
+5, -5, +12 and -12 voltages are generated.  The 5
volts are used for the electronic circuitry, and
the 12 volts are required for the drives.

   The following power supply definitions are
reprinted with permission from PC Power & Cooling,
Inc., Carlsbad, CA 92008, a manufacturer of
exceptionally high-quality power supplies.

    agency approval
    UL, CSA and TUV are safety agencies that test
    specifications such as component spacing, hi-
    pot isolation, leakage currents, circuit board
    flammability and temperature rating.  Hi-pot
    (high-potential) isolation is the ability to
    accept voltage surges with safety.

    efficiency
    Ratio of output power to input power expresses
    as a percentage.

    EMI
    (ElectroMagnetic Interference)  Noise generated
    by the switching action of the power supply and
    other system components.  Conducted EMI is
    radiation reflected back into the power line,
    which is normally controlled with a line
    filter.  Radiated EMI is that portion that
    would radiate into free space, but is
    suppressed by enclosing a power supply's
    circuitry in a metal case.  The FCC governs
    conducted and radiated emission levels in the
    U.S.

    fan rating
    Airflow rated in cubic feet per minute.  A 100%
    increase in airflow will reduce system
    operating temperatures by 50% relative to
    ambient temperature.  For each 10C (18F)
    reduction, the life of the system is doubled
    (Arrhenius equation).

    hold-up time
    Time period that a power supply's output will
    remain within specified limits, following power
    disturbances or a loss of input power. 
    Adequate hold-up time keeps the computer
    running until a standby UPS takes over within a
    few milliseconds.

    load regulation
    Change in output voltage due to a varying load.
    Expressed as a percent of the normal output
    voltage, a power supply with tight load
    regulation delivers optimum voltages regardless
    of system configuration.  This is tested by
    measuring the difference in output voltage when
    applying a light load and a heavy load.

    line regulation
    Change in output voltage due to varying input
    voltage.  Expressed as a percent of the normal
    ouput voltage, a power supply with tight line
    regulation delivers optimum voltages throughout
    the operating range.  This is tested by
    measuring the difference in output voltages
    while varying the input voltage from minimum to
    maximum, i.e., from 85 to 135 volts.

    MTBF
    (Mean Time Between Failure)  Measurement of the
    relative reliability of a power supply based
    upon actual operating data or calculated
    according to MIL-HDBK-217.

    noise (loudness)
    Issues include fan blade pitch and speed, hub
    size, venturi depth, bearing quality and layout
    of power supply components.  Acoustical noise
    is measured logarithmically; each 3 db
    reduction represents 50% less noise.

    operating range
    Minimum and maximum input voltage limits within
    which a power supply will operate to
    specifications.  A power supply with a wide
    input range is recommended when the line
    voltage is subject to brownouts and surges.

    operating temperature
    Range of ambient temperatures within which a
    power supply can be safely operated.

    output current
    Maximum current that can be continuously drawn
    from the output of a power supply.  PC
    motherboards and expansion cards draw 5 volt
    current.  Drive motors draw 12 volts.

    overcurrent protection
    Circuit that shuts down the power supply from
    excessive current, inluding short circuits.

    overvoltage protection
    Circuit that shuts down the power supply if the
    output voltage exceeds a specified limit.

    power good signal
    Signal used to prevent the computer from
    starting until the power has stabilized.  The
    power good line switches from 0 to +5 volts
    within one tenth to one half second after the
    power supply reaches normal voltage levels. 
    Whenever low input voltage causes the output
    voltage to fall below operating levels, the
    power good signal goes back to zero.

    ripple
    AC voltage superimposed onto the DC output,
    expressed as a percent of the normal output
    voltage or as peak to peak volts.  A power
    supply with clean DC output is essential for
    computers with high-speed CPUs and memory.

    transient response
    Time required for the output voltage to return
    within the regulation envelope following a 50%
    load change.  A power supply with quick
    transient response will reduce the risk of
    read/write errors.





power surge
An oversupply of voltage from the power company
that can last up to several seconds.  Power surges
are the most common cause of loss to computers and
electronic equipment.  See spike and sag.



power up
To turn the computer on in an orderly manner.



power user
A person who is very proficient with personal
computers.  It implies knowledge of a variety of
software packages.



PowerBook
A family of Macintosh portable computers from Apple
that include a trackball centered in a wrist rest.
PowerBooks are very popular.  See Macintosh for
specifications.



PowerBuilder
A popular application development system for
Windows client/server environments from Powersoft
Corporation, Concord, MA.  It supports various
databases, including DB2 and Oracle, and is also
packaged with the Watcom SQL database.
PowerBuilder provides visual programming tools as
well as a BASIC-like programming language called
PowerScript.  Macintosh, Windows NT and UNIX
support is also expected by 1995.

   PowerMaker is a subset of PowerBuilder with a
simplified interface for non-programmers and
departmental use.  PowerViewer is the query,
reporting and business graphics generator for both
products.



PowerCD
A consumer-oriented CD-ROM player from Apple that
connects to a TV for Photo CD use, to a Macintosh
for data, audio and Photo CD or to a stereo for
audio CDs.



PowerHouse
A fourth-generation language from Cognos that was
introduced in the late 1970s for midrange
computers.  It supports both character-oriented,
terminal-based applications as well as Windows
clients.  Applications developed under PowerHouse
can be imported into Cognos' Axiant client/server
environment.



PowerMac
A PowerPC-based Macintosh, formally designated the
"Power Macintosh."  With the first models
introduced in March 1994, Apple plans to eventually
migrate all Macintoshes from the Motorola 680x0
family of CPUs to the PowerPC RISC chip.  PowerMacs
run the PowerPC version of the Mac System 7
operating system and also run DOS and Windows
applications by way of Insignia Solutions'
SoftWindows, which is an optional feature.

   Traditional 680x0 applications generally run as
fast or faster on the PowerMacs, depending on how
graphics intensive the application.  Although 680x0
applications are emulated on the PowerMacs, they
can pick up speed, because Apple's QuickDraw
graphics engine is running in native PowerPC code.

   Native PowerMac applications run much faster on
the PowerMacs.  By the summer of 1994, over 100 Mac
applications had been ported to the new
architecture.  It is expected that all Mac
applications will eventually run native on the
PowerMacs.  In order to accomodate this dual
platform, Apple has created a "fat binary" disk
format that allows software to be distributed in
both 680x0 and PowerPC executable form.

   Windows applications generally run at the speed
of a 486/25 on the PowerMac, which is reasonable,
considering the application is emulated.  This
rather acceptable performance is achieved because
SoftWindows uses native Windows code from
Microsoft, ported to PowerPC machine language.  The
Windows application itself is emulated from x86 to
PowerPC, but when a call is made to Windows,
Windows is running native on the PowerPC.  Since
there are countless calls to Windows from the
application, much Windows execution is native
PowerPC.

   The first PowerMac models use the 601 CPU chip.
When models using the 604 and 620 chips are
available, performance will increase dramatically,
and DOS and Windows applications are expected to
run extremely fast, especially on the 620.

   Initial PowerMacs come in 60MHz, 66MHz and 80MHz
versions, known as the 6100/60, 7100/66 and
8100/80.  They come with 8MB of RAM, expandable to
72, 136 and 264MB respectively.  Internal hard
disks range from 160MB to 1GB.  All models are
available in an AV configuration, a suite of
communications technologies that let you send and
receive faxes, play high-quality sound and import
and export video.



PowerOpen
A standard for a UNIX-based operating system
running on the PowerPC platform.  An application
certified as PowerOpen compliant will run on a
PowerPC under any PowerOpen-compliant operating
system.  This is officially known as the PowerOpen
Environment (POE).

   Apple's Macintosh Application System (MAS) is
expected to allow PowerOpen operating system
vendors to run Mac applications.  It includes an
emulator and the Macintosh Toolbox, which allows
the Mac interface to run native while emulating
680x0 instructions in the application.  DOS and
Windows emulation are also expected, most likely
from Insignia Solutions.

   The POE is an application binary interface (ABI)
specification, which differs from an application
program interface (API).  An API deals with the
linkage between the application and the operating
system.  An ABI takes it a step further, defining
API and machine language compatibility for the
hardware platform, in this case, the PowerPC.  The
goal is to create a market for shrink-wrapped
PowerPC applications just as there is for DOS,
Windows and the Mac.

   What has kept UNIX from this very desirable
position all these years are all the different
varieties of UNIX and the platforms they run on.
If the PowerPC chip continues to be the leading
RISC-based hardware platform (it's already the
leader in units shipped after one year), wider
adoption of the chip could promote more support for
PowerOpen compatibility.

   Both operating system and application developers
will seek POE certification, ensuring that their
products are interoperable on this platform.
However, it's always a chicken-egg proposition with
this business, so stay tuned!



PowerOpen Association
An independent membership organization founded in
1993 by Apple, IBM, Motorola, Bull, Harris,
Thompson-CSF and Tadpole Technologies.  It is
dedicated to the broad acceptance of an open
systems standard based on the PowerOpen Environment
(POE).  Certification ensures that the products are
X/Open and Spec 1170 compliant and that they run on
the PowerPC.  Address: 10050 N. Wolf Road,
Cupertino, CA 95014, 408/366-0460.  See PowerOpen.



PowerPC
A family of CPU chips designed by Apple, IBM and
Motorola, introduced in 1993.  Both IBM and
Motorola offer the chips for sale to PowerPC
resellers, but IBM owns the architecture, and
Motorola is a licensee of it.  The PowerPC is
designed to span a range of computing devices from
hand-held machines to supercomputers.

   PowerPC chips are the CPUs in the PowerMacs,
Apple's latest line of Macintoshes, which run a
version of System 7 that supports Mac/680x0 and
Mac/PowerPC applications.  IBM is using the PowerPC
chips in certain RS/6000 models and is expected to
offer PowerPC systems that run OS/2 and a PowerOpen
version of AIX.

   Other operating systems, including Windows NT,
Sun's Solaris, Taligent's object-oriented OS and
various pen-based systems are either here now or
are expected for the PowerPC.  All PC manufacturers
can purchase PowerPC chips from IBM and Motorola
and license operating systems from IBM, Apple and
others.

   The PowerPC is the latest architecture for the
desktop that provides a platform for advanced
applications while supporting existing applications
via emulation and native graphical interface
support for Macintosh and Windows.


              Off to a Running Start
Over a million PowerPC systems have been shipped
within one year of introduction, making the PowerPC
the market leader in RISC-based systems by annual
units sold.  With all the forces in place to
promote the PowerPC, (Apple-IBM-Motorola, the
members of the PowerOpen Association, even Windows
NT runs on the PowerPC), the PowerPC is expected to
gain a large share of the market.


            PowerPC CPU Technical Specs
The PowerPC is a refined version of IBM's RS/6000
single-chip CPU.  It is a RISC-based 32-bit
multitasking microprocessor that has an internal
64-bit data path to memory similar to the Pentium.

   The first model, the 601 (MPC601) runs initially
at 50 and 66MHz and is as fast or faster than a
Pentium, but is half the size and uses half the
electricity.  Upcoming models available throughout
1994 are a low-power MPC603 for notebooks and the
MPC604, which may be up to four times faster than
the 601.  In 1995, a true 64-bit, ultra-fast MPC620
with multiple levels of parallelism, is expected.



PowerPlay
A decision support system from Cognos that
summarizes information for management.  It combines
EIS and DSS features in an integrated environment,
and its Transformer creates multidimensional views
of information.  It runs on Windows clients and VMS
and UNIX servers.



PowerPoint
A presentation graphics program from Microsoft for
Macintosh and Windows.  It was the first desktop
presentation program for the Mac.



PowerSCSI!
Software from Future Domain Corporation that
accompanies its SCSI host adapters for PCs allowing
them to control all SCSI peripherals.  It
translates the popular methods for accessing SCSI
devices, including DOS' int 13, Windows FastDisk,
ASPI and various CD-ROM methods into industry
standard CAM, supported on its host adapter.  See
CorelSCSI.



PowerShare
Software from Apple that resides in a Macintosh
server and provides messaging store and forward,
authentication of network users, encryption of
messages and other workgroup/enterprise services.



Powersoft
(Powersoft Corporation, Concord, MA)  Powersoft is
the developer of the popular PowerBuilder
application development system.  In November 1994,
Sybase, Inc. and Powersoft announced their
agreement to merge, making Powersoft an independent
subsidiary of Sybase.  This creates a software
company with 4,400 employees and revenues exceeding
$700 million.



PowerTalk
Messaging software from Apple that is included in
the Macintosh System 7 Pro operating system.  It
provides a unified mail box that holds different
types of communication including e-mail, fax, voice
mail and pager.  It provides for RSA digital
signatures, which guarantees the authenticity of
documents electronically signed by other users.

   PowerTalk uses the AppleTalk transport protocol
for transmission over the network.  PowerTalk runs
on individual Macs, while PowerShare runs on Mac
servers.  PowerTalk and PowerShare are part of
Apple's AOCE technology framework.



PPC
See PowerPC.



PPD file
(PostScript Printer Description file)  A file that
contains detailed information about a particular
printer.  Although PostScript is a device-
independent language, the PostScript driver uses
information in the PPD file to take advantage of
special features in the target printer or
imagesetter.



PPGA
(Plastic PGA)  See PGA.



pph
(Pages Per Hour)  Measures printing speed.



ppi
(1) (Pixels Per Inch)  The measurement of the
display or print elements.

(2) (Points Per Inch, Pulses Per Inch)  The
measurement of mouse movement.



ppm
(Pages Per Minute)  The measurement of printing
speed.



PPP
(Point-to-Point Protocol)  A communications
protocol that provides dial-up access to the
Internet.  Developed by the Internet Engineering
Task Force (IETF) in 1991, PPP is more advanced
than the earlier SLIP protocol, which is also
commonly used for Internet access.  PPP can
establish and terminate a session as well as hang
up and redial on a low-quality call.  It can run on
any full-duplex link from dial-up to high-speed DS1
and DS3 lines.

   PPP encapsulates common network-layer protocols
in specialized Network Control Protocol packets;
for example, IPCP (IP over PPP) and IPXCP (IPX over
PPP).  It can be used to replace a network adapter
driver, allowing remote users to log on to the
network as if they were inhouse.

   PPP also provides password protection using the
Password Authentication Protocol (PAP) and the
Challenge Handshake Authentication Protocol (CHAP).
See SLIP.



pps
(Packets Per Second)  The measurement of LAN
transmission speed.



PQFP
(Plastic Quad FlatPack)  A surface mount chip
housing with flat leads on all four sides.



PR/SM
(Processor Resource/Systems Manager)  An IBM
mainframe feature that allows the CPU to run as
multiple logical processors, each capable of
running a different operating system and set of
applications.  Standard on ES/9000 models, it is an
upgrade to 3090 processors.



PRAM
(Parameter RAM)  Pronounced "P RAM."  A battery-
backed part of the Macintosh's memory that holds
Control Panel settings and the settings for the
hidden desktop file.  If the command and option
keys are held down at startup, the desktop settings
are cleared and a dialog to rebuild the desktop is
initiated.



precedence
The order in which an expression is processed.
Mathematical precedence is normally:

   1. unary + and - signs
   2. exponentiation
   3. multiplication and division
   4. addition and subtraction

   In order to properly compute the formula that
converts Fahrenheit to Celsius, which is
fahrenheit-32*5/9, the expression

           (fahrenheit-32)*5/9

   must be used with parentheses separating the
fahrenheit-32 from the multiplication.  Since
multiplication is evaluated before subtraction, 32
would be multiplied by 5 first, which is not what
is wanted.

   Logical precedence is normally:

   1. NOT
   2. AND
   3. OR

   In the dBASE query:

list for item = "TIE" .and. color = "GRAY"
   .or. color = "RED"

all gray ties and anything red will be selected,
since ANDs are evaluated before ORs.  Grouping the
colors in parentheses:

  (color="GRAY" .or. color="RED") 

         yields only gray and red ties.





precision
The number of digits used to express the fractional
part of a number.  The more digits, the more
precision.  See single precision and double
precision.



predicate
In programming, a statement that evaluates an
expression and provides a true or false answer
based on the condition of the data.



preemptive multitasking
A multitasking method that shares processing time
with all running programs.  Preemtive multitasking
creates a true timesharing environment in which all
running programs get a recurring slice of time from
the CPU.  Depending on the operating system, the
time slice may be the same for all programs or it
may be adjustable to meet the current mix of
programs and users.  For example, background
programs can be given more CPU time no matter how
heavy the foreground load and vice versa.  Contrast
with non-preemtive multitasking.



prefix notation
See Polish notation.



PreP
(PowerPC REference Platform)  A common
specification for PowerPCs from IBM and Apple that
will allow them to run System 7, Windows NT, OS/2,
AIX, Solaris and NetWare operating systems.  Such
systems are expected in 1995 and may include ports
for common IBM and Apple peripherals.



prepress
In typography and printing, the preparation of
camera-ready materials up to the actual printing
stage, which includes typesetting and page makeup.



preprocessor
Software that performs some preliminary processing
on the input before it is processed by the main
program.



presentation graphics
Presentation materials for overheads, 35mm slide
shows and computer-driven slide shows (screen
shows).  Presentation graphics programs provide a
wide selection of predefined backgrounds and page
layouts as well as the ability to create various
types of business graphics for charting numerical
data.  They include drawing and painting tools and
the ability to select from stock graphical elements
to illustrate a page.

   For computer-driven slide shows, the application
provides a variety of special effects that can be
used to fade and wipe one frame into another such
as commonly found in the video world.  Sound and
video can also be merged into the presentation.

   Examples of Windows presentation graphics
programs are Harvard Graphics, Freelance Graphics,
PowerPoint and Charisma.



Presentation Level Protocol
See PLP.



Presentation Manager
A graphical user interface (GUI) library used to
develop OS/2 applications.  Character-based OS/2
applications can be developed similar to DOS
applications, but OS/2 PM applications are graphics
based like Macintosh, Windows and Motif
applications.  The term used to be the name of the
interface itself, which is now called Workplace
Shell.



Prestel
A commercial videotex service of British Telecom
(formerly part of the British Post Office).



Pretty Good Privacy
See PGP.



preventive maintenance
The routine checking of hardware that is performed
by a field engineer on a regularly scheduled basis.
See remedial maintenance.



PRI
See ISDN.



primary index
The index that controls the current processing
order of a file.  It maintains an index on the
primary key.  See secondary index.



primary key
An indexed field that maintains the primary
sequence of the file/table.



primary storage
The computer's internal memory (RAM).  Contrast
with secondary storage.



primitive
(1) In computer graphics, a graphics element that
is used as a building block for creating images,
such as a point, line, arc, cone or sphere.

(2) In programming, a fundamental instruction,
statement or operation.

(3) In microprogramming, a microinstruction, or
elementary machine operation.



print buffer
See printer buffer.



print column
A column of data on a printed report that may be
subtotalled or totalled.  Print columns are the
heart of a report writer's description.



print engine
See printer engine.



print head
A mechanism that deposits ink onto paper in a
character printer.



print image
A text or graphics document that has been prepared
for the printer.  Format codes for the required
printer have been embedded in the document at the
appropriate places.  With text files, headers,
footers and page numbers have been created and
inserted in every page.



print image format
See print image.



print queue
Disk space that holds output designated for the
printer until the printer can receive it.



print screen
The ability to print the current on-screen image.
See screen dump.



print server
A computer in a network that controls one or more
printers.  It stores the print-image output from
all users of the system and feeds it to the printer
one job at a time.  This function may be part of
the network operating system or an add-on utility.



print spooler
Software that manages printing in the background.
When an application is made to print, it quickly
generates the output on disk and the spooler feeds
the print images to the printer at slower printing
speeds.  This second step can be run in the
background without appreciably interfering with
user interaction in the foreground.  See spooling.



print to disk
To redirect output from the printer to the disk.
The resulting file contains text and graphics with
all the codes required to direct the printer to
print it.  The file can be printed later or at a
remote location without requiring the word
processor, DTP or drawing program that was
originally used to create it.  This is actually the
first stage of a print spooling operation.  See
print spooler.



printed circuit board
A flat board that holds chips and other electronic
components.  The board is made of reinforced
fiberglass or plastic and interconnects components
via copper pathways.  The main printed circuit
board in a system is called a system board or
motherboard, while smaller ones that plug into the
slots in the main board are called boards or cards.

   The printed circuit board of the 1960s connected
discrete components together.  The circuit board of
the 1990s interconnects chips, each containing
hundreds of thousands and millions of elementary
components.

   The "printed" circuit is really an etched
circuit.  A copper foil is placed over the glass or
plastic base and covered with a photoresist.  Light
is shined through a negative image of the circuit
paths onto the photoresist, hardening the areas
that will remain after etching.  When passed
through an acid bath, the unhardened areas are
washed away.  A similar process creates the
microminiaturized circuits on a chip (see chip).



printer
A device that converts computer output into printed
images.  Following is an overview of printer types.

                  Serial Printers
Serial printers print a character at a time from
approximately 10 to 400 cps (about 6 to 240 lpm).
Serial printers use dot matrix and character
printer technologies.  Serial printers are referred
to as character printers regardless of the printing
technology employed.


                   Line Printers
Line printers print a line at a time from
approximately 100 to 5,000 lpm and are the standard
impact printers found in datacenters.  They employ
drum, chain, train, band, dot matrix and dot band
technologies.


                   Page Printers
Page printers, also called laser printers, print a
page at time from approximately 4 to 215 ppm (400
to 14,000 lpm), and generally use the copy machine
electrophotographic technique.  High-speed page
printers are used in large datacenters, and desktop
laser printers are now commonplace for personal
computers.


                 Graphics Printers
Graphics printers use impact serial dot matrix,
impact line dot matrix, impact line dot band and
all non-impact technologies.


                  Color Printers
Color printers use impact dot matrix with multiple
color ribbons, electrophotographic with multiple
color toners, electrostatic plotters with multiple
color toners, printers using Cycolor technology,
ink jet with multiple color inks and thermal-
transfer with multiple colors.


                  IMPACT PRINTERS

           Band, Chain & Train Printers
A continuous loop of several character sets
connected together spins horizontally around a set
of hammers.  When the desired character is in front
of the selected print location, that particular
hammer hits the paper forcing the shaped character
image on the band, chain, or train into the ribbon
and onto the paper.

   Since the chain, band, or train moves so fast,
it appears to print a line at a time.  A band is a
solid loop, while the chain is individual character
images (type slugs) chained together.  The train is
individual character images (type slugs) revolving
in a track, one pushing the other.  See band
printer and chain printer.


                   Drum Printer
A rotating drum (cylinder) contains the character
set carved around it for each print location, like
an odometer.  When the desired character for the
selected print location has rotated around to the
hammer line, the appropriate hammer hits the paper
from behind, forcing it against the ribbon that is
between the paper and the drum.  Since the drum
rotates so fast, it appears to print a line at a
time.  See drum printer.


                Character Printers
Character printers are similar to Selectric
typewriters, printing one character at a time.  A
daisy wheel or similar mechanism is moved serially
across the paper.  At the selected print location,
a hammer hits the shaped character image on the
wheel into the ribbon and onto the paper.


                 Serial Dot Matrix
A vertical set of printing wires moves serially
across the paper, formulating characters by
impacting a ribbon and transferring dots of ink
onto the paper.  The clarity of the character is
determined by how close the dots print together.


                  Line Dot Matrix
A stationary or oscillating line of printing wires
generates images by impacting a ribbon and
transferring dots of ink onto the paper a line at a
time.


                  Dot Band Matrix
A combination band and dot matrix configuration.  A
steel band is etched to create fingers (petals).
At the tip of each finger is an anvil with a steel
dot attached.  Print hammers impact the anvils,
which are larger than the dots, allowing the dots
to be printed in areas between the hammer faces.
Different size dots may be used on different bands
to change the speed of printing and the print
resolution.


                NON-IMPACT PRINTERS

                Electrophotographic
A drum is charged with a high voltage and an image
source paints a negative light copy of the image to
be printed onto the drum.  Where the light falls
onto the drum, the drum is discharged.  A toner
(ink) is allowed to adhere to the charged portion
of the drum.  The drum then fuses the image onto
the paper by pressure and heat.  See
electrophotographic.


                 Electrosensitive
Dots are charged onto specially coated silver-
colored paper, usually in a serial fashion.  The
charge removes the aluminum coating, leaving a
black image.


                   Electrostatic
Dots are charged onto specially coated paper,
usually a line at a time.  An ink adheres to the
charges that become embedded into the paper by
pressure or by heat.


                      Ink Jet
Continuous streams of ink are sprayed onto paper,
or droplets of ink generate a dot matrix image,
usually in a serial fashion.  Another technique
uses ink in a solid form, which is melted just
before it is ejected.


                    Ionographic
A technology that uses ion deposition and is
similar to direct electrostatic, except that in
this type of indirect electrostatic, the image is
formed on a dielectric surface and then transferred
to plain paper.


                  Magnetographic
A magnetic image is created by a set of recording
heads across a magnetic drum.  Monocomponent toner
is applied to the drum to develop the image.  It is
transferred to paper by light pressure and an
electrostatic field.  The toner is then fused by
heat.


                      Thermal
Dots are burned onto specially coated paper that
turns black or blue when heat is applied to it.  A
line of heat elements forms a dot matrix image as
the paper is passed across it, or a serial head
with heating elements is passed across the paper.


               Thermal Wax Transfer
Dots of ink are transferred from a mylar ribbon
onto paper by passing the ribbon and the paper
across a line of heat elements, or by passing a
serial head with heating element across the paper.
See thermal wax transfer.


               Thermal Dye Transfer
Also called dye sublimation and thermal dye
diffusion, this technique is similar to thermal wax
transfer.  However, instead of an ink, dyes are
used, which are vaporized onto a special coated
paper creating continuous tone color for
photorealistic quality.  See thermal dye transfer.





printer buffer
A memory device that accepts printer output from
one or more computers and transmits it to the
printer.  It lets the computer dispose of its
printer output at full speed without waiting for
each page to print.  Printer buffers with automatic
switching are connected to two or more computers
and accept their output on a first-come, first-
served basis.



printer cable
A wire that connects a printer to a computer.  On a
PC, the cable has a 25-pin DB-25 male connector for
the computer and a 36-pin Centronics male connector
for the printer.



Printer Control Language
See PCL.



printer driver
Software routine that converts an application
program's printing request into the language the
printer understands.



printer engine
The unit within the printer that does the actual
printing.  For example, in a laser printer, it is
the "copy machine" unit, which transfers and fuses
the toner onto the paper.  It is specified by its
resolution and speed.



printer file
(1) A document in print image format ready to be
printed.  See print to disk.

(2) Same as printer driver.



printer font
A font used for printing.  Printer and screen
resolutions are not the same, thus fonts generated
for the printer will not display accurately on
screen.  Contrast with screen font.



printout
(PRINTer OUTput)  Same as hard copy.



privacy
The authorized distribution of information (who has
a right to know?).  Contrast with security, which
deals with unauthorized access to data.



private branch exchange
See PBX.



Private Eye
A headband-mounted LED display system from
Reflection Technology, Waltham, MA, that plugs into
a PC.  Its 1x1" screen gives the appearance of a
12" monitor floating in space in front of the
viewer.



private file
A file made available only to the user that created
it.  Contrast with public file.



private key
See encryption.



private line
(1) A dedicated line leased from a common carrier.

(2) A line owned and installed by the user.



PRMD
(PRivate Management Domain)  An inhouse e-mail
service.  See X.400.



PRML
(Partial Response Maximum Likelihood)  A technique
used to differentiate a valid signal from noise by
measuring the rate of change at various intervals
of the rising waveform.  Bits generated by a modem
or hard disk platter have uniform characteristics,
whereas random noise does not.



PRN
(PRiNter)  The DOS name for the first connected
parallel port.  See DOS device names.



problem-oriented language
A computer language designed to handle a particular
class of problem.  For example, COBOL was designed
for business, FORTRAN for scientific and GPSS for
simulation.



procedural language
A programming language that requires programming
discipline, such as COBOL, FORTRAN, BASIC, C,
Pascal and dBASE.  Programmers writing in such
languages must develop a proper order of actions in
order to solve the problem, based on a knowledge of
data processing and programming.  Contrast with
non-procedural language.

   The following dBASE example shows procedural and
non-procedural language to list a file.

  Procedural          Non-procedural (interactive)
USE FILEX                   USE FILEX
  DO WHILE .NOT. EOF        LIST NAME, AMOUNTDUE
    ? NAME, AMOUNTDUE
    SKIP
  ENDDO





procedure
(1) Manual procedures are human tasks.

(2) Machine procedures are lists of routines or
programs to be executed, such as described by the
job control language (JCL) in a mini or mainframe,
or the batch processing language in a personal
computer.

(3) In programming, another term for a subroutine
or function.



procedure oriented
An application that forces the user to follow a
predefined path from step A to step B.  Data entry
programs are typical examples.  Contrast with event
driven.



process
To manipulate data in the computer.  The computer
is said to be processing no matter what action is
taken upon the data.  It may be updated or simply
displayed on screen.

   In order to evaluate a computer system's
performance, the time it takes to process data
internally is analyzed separately from the time it
takes to get it in and out of the computer.  I/O is
usually more time consuming than processing.  See
computer (The 3 C's).



process bound
An excessive amount of processing causing an
imbalance between I/O and processing.  Process-
bound applications may slow down other users in a
multiuser system.

   A personal computer is process bound when it is
recalculating a spreadsheet, for example.



process color
A color printed from four separate printing plates.
Four-color process printing uses cyan, magenta,
yellow and black (CMYK) inks to produce full color
reproduction.  Contrast with spot color.



process control
The automated control of a process, such as a
manufacturing process or assembly line.  It is used
extensively in industrial operations, such as oil
refining, chemical processing and electrical
generation.  It uses analog devices to monitor
real-world signals and digital computers to do the
analysis and controlling.  It makes extensive use
of analog/digital, digital/analog conversion.



process identifier
See PID.



process printing
See process color.



processing
Manipulating data within the computer.  The term is
used to define a variety of computer functions and
methods.  See centralized processing, distributed
processing, batch processing, transaction
processing, multiprocessing and computer (The 3
C's).



processor
(1) Same as CPU.

(2) May refer to software.  See language processor
and word processor.



Processor Independent NetWare
See PIN.



processor unit
Same as computer.



Procomm
A popular PC shareware communications program from
Datastorm Technologies, Inc., Columbia, MO, that
supports a wide number of protocols and terminals.
Procomm Plus is the commercial version with more
features.



PRODIGY
An online information service (partnership of IBM
and Sears) that includes weather and stock market
reports, airline scheduling and at-home shopping.
Users receive a communications program that must be
installed in their personal computer, which
provides full-screen displays and simplifies the
logon.  See online services.



ProDOS
(PROfessional Disk Operating System)  An operating
system for the Apple II family that superseded
Apple's DOS 3.3.  It provides a hierarchical file
system with file names up to 15 characters in
length.



production database
A central database containing an organization's
master files and daily transaction files.



production system
A computer system used to process an organization's
daily work.  Contrast with a system used only for
development and testing or for ad hoc inquiries and
analysis.



productivity software
Refers to word processors, spreadsheets, database
management systems, PIMs, schedulers and other
software packages that are designed for individual
use.  Contrast with custom-designed, multiuser
information systems which provide the primary data
processing in an organization.



productivity suite
A suite of applications that generally includes a
word processor, spreadsheet, database program, comm
program and perhaps a presentation graphics or
charting program.



Professional Write
A word processing program for DOS and Windows from
SoftKey International, Inc., Cambridge, MA.  It is
easy to use and meets the needs of many who write
uncomplicated letters and memos.  Originally called
PFS:Write, it was one of the earliest PC word
processors.



Professional YAM
(Professional Yet Another Modem)  A PC
communications program from Omen Technology, Inc.,
Portland, OR, for the serious communications user.
It is a flexible, full-featured program that
supports a wide variety of terminals and protocols.



PROFS
(PRofessional OFfice System)  IBM office automation
software for the VM mainframe environment.  It
provides an e-mail facility for text and graphics,
a library service for centrally storing text,
electronic calendars and appointment scheduling,
and it allows document interchange with DISOSS
users.  PROFS uses IBM's proprietary ZIP messaging
protocol.



ProgMan
See Program Manager.



PROGMAN.INI
A Windows configuration file that describes the
current state of the Program Manager layout.  For
example, the [Settings] section describes the on-
screen location of the Program Manager window.  The
[Group] section identifies the group window files.
Like WIN.INI and SYSTEM.INI, Windows' major
configuration files, PROGMAN.INI can also be edited
by the user if required.  It usually isn't.



program
A collection of instructions that tell the computer
what to do.  A program is called software; hence,
program, software and instructions are synonymous.
A program is written in a programming language and
is converted into the computer's machine language
by software called assemblers, compilers and
interpreters.

   A program is made up of

        1. machine instructions
        2. buffers
        3. constants and counters

   Instructions are the directions that the
computer will follow (the program's logic).
Buffers are reserved space, or input/output areas,
that accept and hold the data while it's being
processed.  They can receive any kind of
information required by the program.

   Constants are fixed values used to compare the
data against, such as minimums and maximums and
dates.  Menu titles and error messages are another
example of constants.

   Counters, also called variables, are reserved
space for summing money amounts, quantities,
virtually any calculations, including those
necessary to keep track of internal operations,
such as how many times a function should be
repeated.

   The program calls for data in an input-process-
output sequence.  After data has been input into
one of the program's buffers from a peripheral
device (keyboard, disk, etc.), it is processed.
The results are then output to a peripheral device
(screen, printer, etc.).  If data has been updated,
it is output back onto the disk.

   The application program, which does the actual
data processing, does not instruct the computer to
do everything.  When it is ready for input or needs
to output data, it sends a request to the operating
system, which performs those services and then
turns control back to the application program.

   Following is a conceptual illustration of a
program residing in memory.  In the physical
reality of memory, everything below would be in
binary coded form (0s and 1s).


    buffersĿ
                                     
    Ĵ
                                       
    constantscountersĴ
    198415%150250000000000000000000
    Ĵ
           ܳ
           ܳ
           ܳ
      machine instructions  ܳ
      (thousands of them)  ܳ
           ܳ
           ܳ
           ܳ
           ܳ
           ܳ
           ܳ
           ܳ
           ܳ
    

              ANATOMY OF A PROGRAM

     Although represented as small blocks
     above,  machine instructions can be
     variable in length and they also contain
     their own logic path.  Some of them would
     be GOTO instructions that point back to
     the beginning of a routine or to other
     parts of the program.


   For an understanding of what the computer does
to process data, look up computer and read about
The 3 C's (calculate, compare and copy).





program counter
A register or variable used to keep track of the
address of the current or next instruction.  See
address register and instruction register.



program development
See system development cycle.



program generator
See application generator.



Program Information File
See PIF.



program logic
A sequence of instructions in a program.  There are
many logical solutions to a problem.  If you give a
specification to ten programmers, each one may
create program logic that is slightly different
than all the rest, but the results can be the same.
The solution that runs the fastest is usually the
most desired, however.

   Program logic is written using three classes of
instructions: sequential processing, selection and
iteration.

   1. Sequential processing is the series of steps
that do the actual data processing.  Input, output,
calculate and move (copy) instructions are used in
sequential processing.

   2. Selection is the decision making within the
program and is performed by comparing two sets of
data and branching to a different part of the
program based on the results.  In assembly
languages, the compare and branch instructions are
used.  In high-level languages, IF THEN ELSE and
CASE statements are used.

   3. Iteration is the repetition of a series of
steps and is accomplished with DO LOOPS and FOR
LOOPS in high-level languages and GOTOs in assembly
languages.  See loop.



program maintenance
Updating programs to reflect changes in the
organization's business or to adapt to new
operating environments.  Although maintaining old
programs written by ex-employees is often much more
difficult than writing new ones, the task is
usually given to junior programmers, because the
most talented professionals don't want the job.



Program Manager
The control center for Windows 3.x operation.  It
provides the means to launch applications and
manage the desktop.  Program Manager may be
replaced with another shell, such as Norton's
Desktop for Windows, HP's Dashboard or
Quarterdeck's SideBar, all of which provide similar
functionality with a different user interface.



program state
An operating mode of the computer that executes
instructions in the application program.  Contrast
with supervisor state.



program statement
A phrase in a high-level programming language.  One
program statement may result in several machine
instructions when the program is compiled.



program step
An elementary instruction, such as a machine
language instruction or an assembly language
instruction.  Contrast with program statement.



program-to-program communications
Communications between two programs.  Often
confused with peer-to-peer communications, it is a
set of protocols a program uses to interact with
another program.  Peer-to-peer establishment is the
network's responsibility.  You can have program-to-
program communications in a master-slave
environment without peer-to-peer capability.



programmable
Capable of following instructions.  What sets the
computer apart from all other electronic devices is
its programmability.



programmable calculator
A limited-function computer capable of working with
only numbers and not alphanumeric data.



Programmable Interrupt Controller
See PIC.



programmable logic array
See PLA.



programmable logic controller
See PLC.



programmable logic device
See PLD.



programmable read only memory
See PROM.



programmatic interface
Same as API.



programmer
A person who designs the logic for and writes the
lines of codes of a computer program.  See
application programmer and systems programmer.



programmer analyst
A person who analyzes and designs information
systems and designs and writes the application
programs for the system.  In theory, a programmer
analyst is both systems analyst and applications
programmer.  In practice, the title is sometimes
simply a reward to a programmer for tenure.  Which
skill is really dominant is of concern when
recruiting people with such titles.



Programmer's Switch
The physical buttons included with the Macintosh
(fkey on the LC) that include a System Reset button
and a Debugging button that will invoke MacsBug if
present or switch to the built in monitor in ROM.



programming
Creating a computer program.  The steps are:

 1. Developing the program logic to solve the
    particular problem.

 2. Writing the program logic in a specific
    programming language (coding the program).

 3. Assembling or compiling the program to turn it
    into machine language.

 4. Testing and debugging the program.

 5. Preparing the necessary documentation.

   The logic is the most difficult part of
programming.  Writing the language statements is
comparatively easy once the solution has been
developed.  However, regardless of how difficult
the program may be, documenting it is considered
the most annoying activity by most programmers.



programming interface
See API.



programming language
A language used to write instructions for the
computer.  It lets the programmer express data
processing in a symbolic manner without regard to
machine-specific details.

   The statements that are written by the
programmer are called source language, and they are
translated into the computer's machine language by
programs called assemblers, compilers and
interpreters.  For example, when a programmer
writes MULTIPLY HOURS TIMES RATE, MULTIPLY must be
turned into a code that means multiply, and HOURS
and RATE must be turned into memory locations where
those items of data are actually located.

   Like human languages, each programming language
has its own grammar and syntax.  There are many
dialects of the same language, and each dialect
requires its own translating system.  Standards
have been set by ANSI for many programming
languages, and ANSI-standard languages are dialect
free.  However, it can take years for new features
to be included in ANSI standards, and new dialects
inevitably spring up as a result.

   Programming languages fall into two categories:
low-level assembly languages and high-level
languages.  Assembly languages are available for
each CPU family, and each assembly instruction is
translated into one machine instruction by the
assembler program.  With high-level languages, a
programming statement may be translated into one or
several machine instructions by the compiler.

   Following is a synopsis of the major high-level
languages.  Look up each one for more details.


   Ada
   Comprehensive, Pascal-based language used by
   the Department of Defense.


   ALGOL
   International language for expressing
   algorithms.


   APL
   Used for statistics and mathematical matrices.
   Requires special keyboard symbols.


   BASIC
   Developed as a timesharing language in the
   1960s.  It has been widely used in microcomputer
   programming in the past, and various dialects of
   BASIC have been incorporated into many different
   applications.


   C
   Developed in the 1980s at AT&T.  Widely used to
   develop commercial applications.  UNIX is
   written in C.


   C++
   Object-oriented version of C that is popular
   because it combines object-oriented capability
   with traditional C programming syntax.


   COBOL
   Developed in the 1960s.  Widely used for mini
   and mainframe programming.  Also available for
   personal computers.


   dBASE
   Widely used in business applications.  Offshoots
   of dBASE ("Xbase" languages) are Clipper,
   Quicksilver, FoxBase and FoxPro.


   FORTH
   Developed in the 1960s, FORTH is used in process
   control and game applications.


   FORTRAN
   Developed in 1954 by IBM, it was the first major
   scientific programming language.  Some
   commercial applications have been developed in
   it, and it continues to be widely used.


   LISP
   Developed in 1960.  Used for AI applications.
   Its syntax is very different than other
   languages.


   Logo
   Developed in the 1960s, it is noted for its ease
   of use and "turtle graphics" drawing functions.


   Modula-2
   Enhanced version of Pascal introduced in 1979.


   MUMPS
   Originally Massachusetts Utility
   MultiProgramming System, it includes its own
   database.  It is widely used in medical
   applications.


   Pascal
   Originally an academic language developed in the
   1970s.  Borland commercialized it with its Turbo
   Pascal.


   Prolog
   Developed in France in 1973.  Used throughout
   Europe and Japan for AI applications.


   REXX
   Runs on IBM mainframes.  Used as a general
   purpose macro language.


   Visual Basic
   Version of BASIC for Windows programming from
   Microsoft that is very popular.





Progress
An application development system for client/server
environments from Progress Software, Corporation,
Bedford, MA.  It supports a variety of clients,
including DOS, Windows, OS/2, AIX, HP-UX and Sun.
It includes its own relational DBMS, but interfaces
to Oracle, Sybase and others.  The majority of
Progress systems are created by third-party
developers.  The company was founded in 1984.



progressive scan
Same as non-interlaced.



project life cycle
See full project life cycle and system life cycle.



project manager
Software used to monitor the time and materials on
a project.  All tasks to complete the project are
entered into the database, and the program computes
the critical path, the series of tasks with the
least amount of slack time.  Any change in the
critical path slows down the entire project.



projection panel
See LCD panel.



Prokey
A keyboard macro processor for DOS and Windows from
CE Software, Inc., West Des Moines, IA, that allows
users to eliminate repetitive typing by setting up
an occurrence of text or a series of commands as a
macro.



Prolog
(PROgramming in LOGic)  A programming language used
for developing AI applications (natural language
translation, expert systems, abstract problem
solving, etc.).  Developed in France in 1973, it is
used throughout Europe and Japan and is gaining
popularity in the U.S.

   Similar to LISP, it deals with symbolic
representations of objects.  The following example,
written in University of Edinburgh Prolog, converts
Fahrenheit to Celsius:

  convert:- write('Enter Fahrenheit'),
   read(Fahr),
   write('Celsius is '),
   Cent is (5 * (Fahr - 32)) / 9,
   write(Cent),nl.





PROM
(Programmable Read Only Memory)  A permanent memory
chip that is programmed, or filled, by the customer
rather than by the chip manufacturer.  It differs
from a ROM, which is programmed at the time of
manufacture.  PROMs have been mostly superseded by
EPROMs, which can be reprogrammed.  See PROM
programmer.



PROM blower
Same as PROM programmer.



PROM programmer
A device that writes instructions and data into
PROM chips.  The bits in a new PROM are all 1s
(continuous lines).  The PROM programmer only
creates 0s, by "blowing" the middle out of the 1s.
Some earlier units were capable of programming both
PROMs and EPROMs.



prompt
A software message that requests action by the
user; for example, "Enter employee name."  Command-
driven systems issue a cryptic symbol when ready to
accept a command; for example, the dot (.) in
dBASE, the $ or % in UNIX, and the venerable C:\>
in DOS.  See DOS prompt.



propagation
The transmission (spreading) from one place to
another.



propagation delay
The time it takes to transmit a signal from one
place to another.



property list
In a list processing language, an object that is
assigned a descriptive attribute (property) and a
value.  For example, in Logo, PUTPROP "KAREN
"LANGUAGE "PARADOX assigns the value PARADOX to the
property LANGUAGE for the person named KAREN.  To
find out what language Karen speaks, the Logo
statement PRINT GETPROP "KAREN "LANGUAGE will
generate PARADOX as the answer.



proportional spacing
Character spacing based on the width of each
character.  For example, an I takes up less space
than an M.  In monospacing (fixed), the I and M
each take up the same space.  See kerning.



proprietary software
Software owned by an organization or individual.
Contrast with public domain software.



Protected Mode
In Intel 286s and up, an operational state that
allows the computer to address all of memory.  It
also prevents an errant program from entering into
the memory boundary of another.  In a 386 and up,
it provides access to 32-bit instructions and
sophisticated memory management modes.  See 32-bit
processing, Real Mode, Virtual 8086 Mode and memory
protection.



protocol
Rules governing transmitting and receiving of data.
See communications protocol and OSI.



protocol analyzer
See network analyzer.



protocol stack
The hierarchy of protocols used in a communications
network.  Network architectures designed in layers,
such as TCP/IP, OSI and SNA, are referred to as
stacks.  See OSI model.



protocol suite
Same as protocol stack.



prototyping
(1) Creating a demo of a new system.  Prototyping
is essential for clarifying information
requirements.  The design of a system (functional
specs) must be finalized before the system can be
built.  While analytically-oriented people may have
a clear picture of requirements, others may not.

   Using fourth-generation languages, systems
analysts and users can develop the new system
together.  Databases can be created and manipulated
while the user monitors the progress.

   Once users see tangible output on screen or on
paper, they can figure out what's missing or what
the next question might be if this were a
production system.  If prototyping is carefully
done, the end result can be a working system.

   Even if the final system must be reprogrammed in
other languages for standardization or machine
efficiency, prototyping has served to provide
specifications for a working system rather than a
theoretical one.

(2) See function prototyping.



Prt Sc
See print screen.



PS
(Personal Services)  IBM office automation software
for PCs, minis and mainframes, which includes word
processing, electronic mail and library services.



PS/1
An IBM home computer series introduced in 1990.
The original models featured an integrated monitor
and easy-to-open case.  The first PS/1 was a 286
with an ISA-bus.  See PC.



PS/2
An IBM personal computer series introduced in 1987,
superseding the original PC line.  It introduced
the 3.5" floppy disk, VGA graphics and Micro
Channel bus.  The 3.5" disks and VGA are now common
in all PCs, but the Micro Channel is used primarily
by IBM.  Smaller PS/2 models use the ISA bus.  See
PC.



PS/2 bus
Same as Micro Channel.



pseudo compiler
A compiler that generates a pseudo language, or
intermediate language, which must be further
compiled or interpreted for execution.



pseudo-duplexing
A communications technique that simulates full-
duplex transmission in a half-duplex line by
turning the line around very quickly.



pseudo language
An intermediate language generated from a source
language, but not directly executable by a CPU.  It
must be interpreted or compiled into machine
language for execution.  It facilitates the use of
one source language for different types of
computers.  See "ANDF" in OSF definition.



PSK
See DPSK.



PSN
(Packet-Switched Network)  A communications network
that uses packet switching technology.



PSS
See EPSS.



PSTN
(Public Switched Telephone Network)  The worldwide
voice telephone network.



PSW
(Program Status Word)  A hardware register that
maintains the status of the program being executed.



PTOCA
(Presentation Text Object Content Architecture)
See MO:DCA.



PTT
(Postal, Telegraph & Telephone)  The governmental
agency responsible for combined postal, telegraph
and telephone services in many European countries.



PU
(Physical Unit)  In SNA, software responsible for
managing the resources of a node, such as data
links.  A PU supports a connection to the host
(SSCP) for gathering network management statistics.



PU 2.1
(Physical Unit 2.1)  In SNA, the original term for
Node Type 2.1, which is software that provides
peer-to-peer communications between intelligent
devices (PCs, workstations, minicomputers).  Only
LU 6.2 sessions are supported between Type 2.1
nodes (PU 2.1).



public domain software
Software in which ownership has been relinquished
to the public at large.  See freeware and
shareware.



public file
A file made available to all other users connected
to the system or network.  Contrast with private
file.



public key
See encryption.



Publish and Subscribe
A Macintosh System 7 capability that provides hot
links between files.  All or part of a file can be
published into an "edition file," which is imported
into a subscriber file.  When any of the published
files are updated, the subscriber file is also
updated.



puck
The mouse-like object used to draw on a digitizer
tablet.



pull-down menu
Also called a pop-down menu, a menu that is
displayed from the top of the screen downward when
its title is selected.  The menu remains displayed
while the mouse button is depressed.  To select a
menu option, the highlight bar is moved (with the
mouse) to the appropriate line and the mouse button
is let go.

   The drop-down menu is a variation that keeps the
menu open after its title is selected.  To select a
menu option, the highlight bar is moved to the line
and the mouse button is clicked.  Key commands may
also activate drop-down menus.



pulse code modulation
See PCM.



pulse level device
A disk drive or other device that inputs and
outputs raw voltages.  Data coding/decoding is in
the controller the device.  Contrast with bit level
device.



PUMA
(Programmable Universal Micro Accelerator)  A Chips
and Technolgies' chipset that accelerates graphics
operations for the screen and printer.



punch block
Also called a quick-connect block, a device that
interconnects telephone lines from remote points.
The wires are pushed, or punched, down into metal
teeth that strip the insulation and make a tight
connection.



punched card
An early storage medium made of thin cardboard
stock that holds data as patterns of punched holes.
Each of the 80 or 96 columns holds one character.
The holes are punched by a keypunch machine or card
punch peripheral and are fed into the computer by a
card reader.

   Although still used as turnaround documents,
punched cards are practically obsolete.  However,
from 1890 until the 1970s, they were synonymous
with data processing.  Concepts were simple: the
database was the file cabinet; a record was a card.
Processing was performed on separate machines
called sorters, collators, reproducers, calculators
and accounting machines.



purchasing a personal computer
See how to select a personal computer.



push/pop
Instructions that store and retrieve an item on a
stack.  Push enters an item on the stack, and pop
retrieves an item, moving the rest of the items in
the stack up one level.  See stack.



push/pull tractor
A printer tractor that can be switched from pushing
paper onto the platen to pulling it from the
platen.  Single-sheet continuous forms can be
pushed, but most multipart forms and labels must be
pulled to prevent jamming.



put
In programming, a request to store the current
record in an output file.  Contrast with get.



PVC
(Permanent Virtual Circuit)  A point-to-point
connection that is established ahead of time.  All
PVCs defined at the time of subscription to a
particular service are known as a VPN (virtual
private network).  Contrast with SVC.



PVCS
A system of version control and configuration
management from Intersolv, Inc., Rockville, MD,
that runs on DOS, Windows, OS/2 and various UNIX
platforms.  In 1994, it was the most widely used
SCM system on PC LANs.



PVGA
(Paradise VGA)  A VGA adapter or VGA chips from the
Paradise Division of Western Digital.



Px64
An ITU-TSS standard for transmitting audio and
video in 64 Kbits/sec ISDN channels (P represents
number of channels used).  Although video
conferencing can be done in only one or two
channels, more channels are required for smooth
motion.

   Px64 uses two screen formats.  The CIF (Common
Intermediate Format) generates a 352x288
resolution, while QCIF (Quarter CIF) is 176x144.
CIF transmits at 36.45 Mbits/sec; QCIF is 9.115
Mbits/sec.  See H.261.



PXP
(Packet eXchange Protocol)  See PEP.



Pyramid
(Pyramid Technology Corporation, San Jose, CA)  A
computer company founded in 1981 that specializes
in multiprocessing open systems.  It originally
adapted UNIX to symmetric multiprocessing (SMP) for
its proprietary MIServer architecture that was also
licensed to other vendors.  Its current line is the
R4400-based Nile Series that provides scalable
processing up to 16 CPUs.  Pyramid helped pioneer
SMP on open systems, and its DC/OSx operating
system is the SMP implementation of UNIX System V
Release 4.



Q-bus
A bus architecture used in Digital's PDP-11 and
MicroVAX series.



Q&A
An integrated file manager and word processor for
DOS and Windows from Symantec Corporation,
Cupertino, CA, that includes mail merge capability
as well as a programming language for customizing
data entry forms and reports.  Its Intelligent
Assistant feature provides a query language that
can learn new words from the user.



QAM
(1) (Quadrature Amplitude Modulation)  A modulation
technique that generates four bits out of one baud.
For example, a 600 baud line (600 shifts in the
signal per second) can effectively transmit 2,400
bps using this method.  Both phase and amplitude
are shaped with each baud, resulting in four
possible patterns.

(2) (Quality Assessment Measurement)  A system used
to measure and analyze voice transmission.



QBasic
A BASIC interpreter from Microsoft that comes with
DOS starting with DOS 5.  It supersedes Microsoft's
GW-BASIC and includes REMLINE.BAS, a program that
helps convert GW-BASIC programs to QBasic.



QBE
(Query By Example)  A method for describing a query
originally developed by IBM for mainframes.  A
replica of an empty record is displayed and the
search conditions are typed in under their
respective columns.  The following query selects
all Pennsylvania records that have a balance due of
$5000 or more.

     City         State Balance due
    Ŀ
                PA   >=5000       

            A query by example





QCIF
(Quarter CIF)  A video format that transmits 9.115
Mbits/sec at 30 frames/sec, one quarter the speed
of CIF.  See H.261.



QEMM-386
(Quarterdeck EMM-386)  A popular DOS memory manager
for 386s and up from Quarterdeck Office Systems,
Santa Monica, CA.  Its Stealth feature in Version
6.0 remaps ROM BIOS routines into EMS to free up
high DOS memory.  It is also part of DESQview.



QIC
(Quarter Inch Cartridge)  A backup technology that
uses 1/4" wide (6.35mm) magnetic tape cartridges.
It uses the serpentine recording method with
cartridge capacities ranging from 40MB to 13GB.

   QIC minicartridges are designed around a 3.5"
form factor, and QIC data cartridges are 5.25".
Minicartridges and data cartridges are also known
as DC2000 and DC6000 cartridges.

              MINICARTRIDGE DRIVES (3.5")
 Recording    Media  Storage      InterfacesĿ
  Format      Type    (MB)Read   Basic Intelligent
                          Compatibility
 QIC-40-MC   DC2000     40       QIC-107
                                 QIC-115
                                 QIC-117
 QIC-80-MC   DC2120    12040     QIC-107
             DC2080     80       QIC-115
             QIC-159   208       QIC-117
             QIC-160   170
 QIC-100-MC  DC2000  20/40       QIC-103   SCSI
 QIC-128-MC  DC2110     86100    QIC-103   SCSI
             DC2165    128
 QIC-3010-MC QIC-143   34040/80  QIC-107  Floppy
             QIC-148   425       QIC-115    or
                                 QIC-117   IDE
 QIC-3020-MC QIC-143   68040/80  QIC-107  Floppy
             QIC-148   8333010   QIC-115    or
                                 QIC-117   IDE
 QIC-3030-MC QIC-143   580                 SCSI-2
 QIC-3040-MC QIC-143   840                 SCSI-2
             QIC-148   1GB                 SCSI-2
 QIC-3050-MC QIC-143   1GB                 SCSI-2
 QIC-3070-MC QIC-138   4GB3030             SCSI-2
 QIC-3080-MC QIC-152 1.6GB                 SCSI-2
             QIC-156      
 QIC-3110-MC QIC-153   2GB                 SCSI-2


             DATA CARTRIDGE DRIVES (5.25")
 Recording    Media  Storage      InterfacesĿ
  Format      Type    (MB)Read   Basic Intelligent
                          Compatibility
 QIC-24-DC   DC600A     60       QIC-38    SCSI
 QIC-120-DC  DC6150    12524               SCSI
 QIC-150-DC  DC6250    25024/120           SCSI
             DC6150    150
 QIC-525-DC  DC6525    525120/150          SCSI
             DC6320    320                 SCSI-2
 QIC-1000-DC QIC-136 1.2GB120/150/525      SCSI
                                           SCSI-2
 QIC-1350-DC QIC-137 1.6GB525/1000         SCSI-2
 QIC-2GB-DC  QIC-136 2.5GB120/150/525/1000 SCSI-2
 QIC-2100-DC QIC-137 2.6GB525/1000/1350    SCSI-2
 QIC-5GB-DC  QIC-137   5GB24/120/150/525   SCSI-2
                          1000/1350/2GB
                          2100
 QIC-5010-DC QIC-139  13GB150/525/1000     SCSI-2
                          1350/2100





QIC-WIDE
(Quarter Inch Cartridge-WIDE)  An extension to the
QIC tape from Sony that provides more storage
capacity than quarter inch tape.  It uses .315"
wide tape rather than .25", a thin base film that
increases length from 300 to 400 feet and a higher
recording density.  It uses the standard QIC
minicartridge with a redesigned housing.  QIC-WIDE
drives support both QIC-WIDE and QIC formats.



QMF
(Query Management Facility)  An IBM fourth-
generation language for end-user interaction with
DB2.



Qmodem Pro
Communications programs for DOS and Windows from
Mustang Software, Inc., Bakersfield, CA.  The
programs support a wide variety of modems as well
as all the major file transfer protocols and
terminal emulations.  The Windows version is noted
for its integrated fax facilities allowing the user
to fax directly from within any Windows word
processor.  Mustang Software is also the publisher
of the popular WILDCAT! BBS software.



QNX
A multiuser, multitasking, realtime operating
system for PCs from QNX Software Systems, Ltd.,
Kanata, Ontario, noted for its low-memory
requirement and rapid response.  Similar to UNIX,
it has been in use since the early 1980s.



quadbit
A group of four bits used in QAM modulation.



Quadra
Apple's brand name for certain Macintosh computers.
See Macintosh.



quadrature amplitude modulation
See QAM.



quadrillion
One thousand times one trillion or 10 to the 15th
power.  See femtosecond.



quantize
To assign a number to a sample.  The larger the
number the more the digital sample represents the
analog signal.  See sampling.



QuarkXpress
A desktop publishing program for the Macintosh and
Windows from Quark, Inc., Denver, CO.  Originally
developed for the Mac, it is noted for its precise
typographic control and advanced text and graphics
manipulation.



quartz crystal
A slice of quartz ground to a prescribed thickness
that vibrates at a steady frequency when stimulated
by electricity.  The tiny crystal, about 1/20th by
1/5th of an inch, creates the computer's heartbeat.



Quattro Pro
A PC spreadsheet from Novell that provides advanced
graphics and presentation capabilities.  It has an
optional interface that is keystroke, macro and
file compatible with Lotus 1-2-3.  Version 2.0 adds
goal seeking, 3-D graphing and the ability to
create multi-layered slide shows.  Quattro Pro was
originally developed by Borland and was purchased
by Novell in 1994.



query
To interrogate a database (count, sum and list
selected records).  Contrast with report, which is
usually a more elaborate printout with headings and
page numbers.  The report may also be a selective
list of items; hence, the two terms may refer to
programs that produce the same results.



query by example
See QBE.



query language
A generalized language that allows a user to select
records from a database.  It uses a command
language, menu-driven method or a query by example
(QBE) format for expressing the matching condition.

   Query languages are usually included in DBMSs,
and stand-alone packages are available for
interrogating files in non-DBMS applications.  See
query program.



query program
Software that counts, sums and retrieves selected
records from a database.  It may be part of a large
application and be limited to one or two kinds of
retrieval, such as pulling up a customer account on
screen, or it may refer to a query language that
allows any condition to be searched and selected.



queue
Pronounced "Q."  A temporary holding place for
data.  See message queue and print queue.



Quick B
CompuServe's communications protocol for
downloading files.



QuickApp
A software tool from DCA that adds screen scraping
capability to client/server development systems.
QuickApp scans and records the mainframe terminal
screens that are displayed on the PC via a 3270
emulator.  QuickApp navigation engines that work
within languages, such as PowerBuilder, Visual
Basic, SQLWindows, ObjectView and Visual C++, allow
developers point and click access to on-screen
fields.



QuickBASIC
A popular BASIC compiler from Microsoft that adds
advanced features to the BASIC language.



QuickBooks
A small business accounting system for Windows from
Intuit, Inc., Menlo Park, CA.  It works like the
popular Quicken program, but is designed to track a
whole business.



QuickC
A C compiler and development system from Microsoft
that is compatible with Microsoft C and used by the
beginner or occasional programmer.  QuickC for
Windows is a version that provides a Windows-based
environment for developing Windows applications.
See Visual C++.



QuickDB
An ODBC driver from DCA that provides an APPC
connection directly from the client to communicate
with IBM's DRDA interface.



Quickdraw
The graphics display system built into the
Macintosh.  It accepts commands from the
application and draws the corresponding objects on
the screen.  It provides a consistent interface
that software developers can work with.



Quicken
A popular financial management program for PCs and
Macs from Intuit, Inc., Menlo Park, CA.  It is used
to write checks, organize investments and produce a
variety of reports for personal finance and small
business.



QuickPascal
A pascal compiler from Microsoft that is compatible
with Turbo Pascal and provides object oriented
capabilities.



QuickPeer
A software tool from DCA that generates the
communications code for developing three-tier
client/server systems.  It works with languages
such as PowerBuilder, Visual Basic, SQLWindows,
ObjectView and Visual C++.  It eliminates writing
highly technical code in languages such as C to
support the communications protocols.



Quicksilver
A family of dBASE III PLUS compilers originally
developed by WordTech Systems, Inc.  In 1992, the
technology was acquired by Borland.  See Arago.



QuickTime
Multimedia extensions to Macintosh's System 7 that
add sound and video capabilities.  A QuickTime file
can contain up to 32 tracks of audio, video, MIDI
or other time-based control information.  Most
major Macintosh DBMSs (database management systems)
support QuickTime.  Apple also provides a QuickTime
for Windows version for Windows-based PCs.



QuickWin
A library of C and FORTRAN routines from Microsoft
that allows quick porting of DOS applications to
the Windows environment.  Character-based apps run
in resizable windows.



quit
To exit the current program.  It's a good habit to
quit a program before turning the computer off.
Some programs don't close all files properly until
quit is activated.

   To quit the DOS version of this database, hold
down the Ctrl key and press Q.



qwerty keyboard
The standard English language typewriter keyboard.
Q, w, e, r, t and y are the letters on the top
left, alphabetic row.  It was originally designed
to slow typing to prevent the keys from jamming.
See Dvorak keyboard.



R3000
See MIPS Computer.



R4000
See MIPS Computer.



R4400
See MIPS Computer.



R:BASE
A relational DBMS for PCs from Microrim, Inc.,
Bellevue, WA, that provides interactive data
processing, a complete programming language and an
application generator.  It was the first DBMS to
compete with dBASE II in the early 1980s.



RACE
(Random Access Card Equipment)  An early RCA mass
storage device.  Magnetic cards were released from
a cartridge, passed down a raceway and wrapped
around a read/write head.  It often jammed!



RACF
(Resource Access Control Facility)  IBM mainframe
security software introduced in 1976 that verifies
user ID and password and controls access to
authorized files and resources.



rack
A frame or cabinet into which components are
mounted.



rack mounted
Components that are built to fit in a metal frame.
Electronic devices, such as testing equipment and
tape drives, are often rack mounted units.



RAD
(Rapid Application Development)  Developing systems
incrementally and delivering working pieces every
three to four months, rather than waiting until the
entire project is programmed before implementing
it.  Over the years, many information projects have
failed, because, by the time the implemention took
place, the business had changed.

   RAD employs a variety of automated design and
development tools, including CASE, 4GLs, visual
programming and GUI builders, that get prototypes
up and running quickly.

   RAD was coined years ago by industry guru, James
Martin, and focuses on personnel management and
user involvement as much as on technology.  Joint
application development (JAD) is another RAD
concept.



RAD tool
Any program or utility that speeds up the
development and programming of an application.
Visual programming tools are widely used to quickly
develop graphical front ends.



radio
The transmission of electromagnetic energy
(radiation) over the air or through a hollow tube
called a waveguide.  Although radio is often
thought of as only AM or FM, all airborne
transmission is radio, including satellite and
line-of-sight microwave.



radio buttons
A series of on-screen buttons that allow only one
selection.  If a button is currently selected, it
will de-select when another button is selected.



radio frequency
See RF.



radio frequency interference
See RFI.



Radio Shack
See Tandy.



radix
The base value in a numbering system.  For example,
in the decimal numbering system, the radix is 10.



radix point
The location in a number that separates the
integral part from the fractional part.  For
example, in the decimal system, it is the decimal
point.



ragged right
In typography, non-uniform text at the right
margin, such as the text you're reading.



RAID
(Redundant Arrays of Inexpensive Disks)  A category
of disk arrays (two or more drives working
together) that provide increased performance and
various levels of error recovery and fault
tolerance.  The disk controller is designed to
perform these techniques.  RAID can also be
implemented in software using standard drives and
controllers.

 Level           Configuration

  0  Single disk only or multiple disks using
      disk striping only (essentially non-RAID).

  1  Uses disk mirroring to provide 100%
      duplication of data.

  2  Highest performance.  Uses extra drives to
      detect 2-bit errors and correct 1-bit errors
      on the fly.  Interleaves by bit or block.

  3  Highest performance.  Does parity checking but
      cannot guarantee on-the-fly recovery.
      Interleaves data by bit or block.

  4  Uses dedicated drive for parity.  Can be used
      with only two drives.  Interleaves data by
      sector and can handle multiple I/Os from
      sophisticated operating systems.

  5  Most popular RAID method.  Works with two or
      more drives.  Does not require dedicated
      parity drive.  Can be made fault tolerant.





RAM
(Random Access Memory)  The computer's primary
workspace.  Also true of most memory chips (ROMs,
PROMs, etc.), "random" means that the contents of
each byte can be directly accessed without regard
to the bytes before or after it.  RAM chips require
power to maintain their content.  That's why you
must save your files to the disk before you turn
the computer off.  Any running programs and all the
data they currently reference, such as the
spreadsheet or word processing document you're
working on, are lost without power.  See dynamic
RAM, static RAM and memory.  Contrast with disk and
ROM.



RAM cache
See cache.



RAM card
(1) A printed circuit board containing memory chips
that is plugged into a socket within the computer.

(2) A credit-card-sized module that contains memory
chips and battery.  See memory card.



RAM chip
(Random Access Memory chip)  A memory chip.  See
dynamic RAM, static RAM, RAM and memory.



RAM cram
Insufficient memory to run applications, especially
in DOS PCs with its 1MB memory limit.



RAM disk
A disk drive simulated in memory.  To use it, files
are copied from magnetic disk into the RAM disk.
Processing is faster, because there's no mechanical
disk action, only memory transfers.  Updated data
files must be copied back to disk before the power
is turned off, otherwise the updates are lost.
Same as E-disk and virtual disk.



RAM network
See Mobitex.



RAM refresh
Recharging dynamic RAM chips many times per second
in order to keep the bit patterns valid.



RAM resident
Refers to programs that remain in memory in order
to interact with other programs or to be instantly
popped up when required by the user.  See TSR.



RAMAC
(Random Access Method of Accounting and Control)
The first hard disk computer which was introduced
by IBM in 1956.  All 50 of its 24" platters held a
total of five million characters!  It was half
computer, half tabulator.  It had a drum memory for
program storage, but its I/O was wired by
plugboard.

   After 38 years, IBM resurrected the RAMAC name
with the introduction of a high-capacity disk
storage system in 1994.  The differences between
the 1956 and 1994 RAMACs are rather dramatic.
Areal density rose from 2000 bits per square inch
to 260 million increasing total storage capacity
from 5MB to 90GB.  Access times changed from 600 ms
to 9.5 ms.



Rambus DRAM
See RDRAM.



RAMDAC
(Random Access Memory Digital to Analog Converter)
The VGA controller chip that maintains the color
palette and converts data from memory into analog
signals for the monitor.



Ramdrive
A RAM disk driver that comes with DOS, starting
with DOS 4.0.  See DOS RAM disks.



RAMIS
See CA-RAMIS.



random access
Same as direct access.



random access memory
See RAM.



random noise
Same as Gaussian noise.



random number generator
A program routine that produces a random number.
Random numbers are created easily in a computer,
since there are many random events that take place;
for example, the duration between keystrokes.  Only
a few milliseconds' difference is enough to seed a
random number generation routine with a different
number each time.  Once seeded, an algorithm
computes different numbers throughout the session.



range
(1) In data entry validation, a group of values
from a minimum to a maximum.

(2) In spreadsheets, a series of cells that are
worked on as a group.  It may refer to a row,
column or rectangular block defined by one corner
and its diagonally opposite corner.



ransom note typography
Using too many fonts in a document.  The term comes
from the text in a ransom note that is pasted
together from words cut out of different magazines
and newspapers.

   The ease with which fonts can be selected in a
word processor has led many inexperienced people to
use too many fonts in a document or newsletter.
Typographers and graphics artists know that only
two or three fonts are necessary for the most
professional appearance.



rapid application development
See RAD.



RARP
See ARP.



RAS
(1) (Remote Access Server)  A network server that
provides access to remote computer users via modem.

(2) (Remote Access Service)  Software in Windows
for Workgroups and Windows NT that provides access
to remote computer users via modem.

(3) (Reliability Availability Serviceability)
Originally an IBM term, it refers to a computer
system's overall reliability, its ability to
respond to a failure and its ability to undergo
maintenance without shutting it down entirely.



raster display
A display terminal that generates dots line by line
on the screen.  TVs and almost all computer screens
use the raster method.  Contrast with vector
display.



raster graphics
In computer graphics, a technique for representing
a picture image as a matrix of dots.  It is the
digital counterpart of the analog method used in
TV.  However, unlike TV, which uses one standard,
there are many raster graphics standards.  See
graphics.  Contrast with vector graphics.



raster image processor
See RIP.  Remember...  try  the acronym first!



raster scan
Displaying or recording a video image line by line.



rasterize
To perform the conversion of vector graphics
images, vector fonts or outline fonts into bitmaps
for display or printing.  Unless output is printed
on a plotter, which uses vectors directly, all non-
bitmapped images must be rasterized into bitmaps
for display or printing.  See font scaler.



raw data
Data that has not been processed.



ray tracing
In computer graphics, the creation of reflections,
refractions and shadows on a graphics image.  It
follows a series of rays from a specific light
source and computes each pixel in the image to
determine the effect of the light.  It is a very
process-intensive operation.



RBASE
See R:BASE.



RBHC
(Regional Bell Holding Company)  Same as RBOC.



RBOC
(Regional Bell Operating Company)  One of seven
regional telephone companies created by
divestiture: Nynex, Bell Atlantic, BellSouth,
Southwestern Bell, US West, Pacific Telesis and
Ameritech.



RCA connector
Same as phono connector.



RCDD
See BICSI.



RCS
(1) (Remote Computer Service)  A remote timesharing
service.

(2) (Revision Control System)  A UNIX utility that
provides version control.



Rdb
(Relational DataBase/VMS)  A relational DBMS from
Digital for its VAX series.



RDBMS
(Relational DataBase Management System)  See
relational database.



RDRAM
(Rambus DRAM)  A dynamic RAM chip from Rambus,
Inc., that transfers data at 500MBytes/sec (3-10
times faster than DRAM and VRAM chips).  It
requires modified motherboards, but eliminates the
need for memory caches.



read
To input into the computer from a peripheral device
(disk, tape, etc.).  Like reading a book or playing
an audio tape, reading does not destroy what is
read.

   A read is both an input and an output (I/O),
since data is being output from the peripheral
device and input into the computer.  Memory is also
said to be read when it is accessed to transfer
data out to a peripheral device or to somewhere
else in memory.  Every peripheral or internal
transfer of data is a read from somewhere and a
write to somewhere else.



read cycle
The operation of reading data from a memory or
storage device.



read error
A failure to read the data on a storage or memory
device.  Although it is not a routine phenomenon,
magnetic and optical recording surfaces can become
contaminated with dust or dirt or be physically
damaged, and cells in memory chips can malfunction.

   When a read error occurs, the program will allow
you to bypass it and move on to the next set of
data, or it will end, depending on the operating
system.  However, if the damaged part of a disk
contains control information, the rest of the file
may be unreadable.  In such cases, a recovery
program must be used to retrieve the remaining data
if there is no backup.



read only
(1) Refers to storage media that permanently hold
their content; for example, ROM and CD-ROM.

(2) A file which can be read, but not updated or
erased.  See file attribute.



read-only attribute
A file attribute that, when turned on, indicates
that a file can only be read, but not updated or
erased.



read only memory
See ROM.



read the flaming manual
See RTFM.



read/write
(1) Refers to a device that can both input and
output or transmit and receive.

(2) Refers to a file that can be updated and
erased.



read/write channel
Same as I/O channel.



read/write head
A device that reads (senses) and writes (records)
data on a magnetic disk or tape.  For writing, the
surface of the disk or tape is moved past the
read/write head.  By discharging electrical
impulses at the appropriate times, bits are
recorded as tiny, magnetized spots of positive or
negative polarity.

   For reading, the surface is moved past the
read/write head, and the bits that are present
induce an electrical current across the gap.



read/write memory
Same as RAM.



reader
A machine that captures data for the computer, such
as an optical character reader, magnetic card
reader and punched card reader.  A microfiche or
microfilm reader is a self-contained machine that
reads film and displays its contents.



readme file
A text file copied onto software distribution disks
that contains last-minute updates or errata that
have not been printed in the documentation manual.



readout
(1) A small display device that typically shows
only a few digits or a couple of lines of data.

(2) Any display screen or panel.



real address
Same as absolute address.



Real Mode
An operational state in Intel 286s and up in which
the computer functions as an 8086/8088.  It is
limited to one megabyte of memory.  See Protected
Mode and Virtual 86 Mode.



real storage
Real physical memory in a virtual memory system.



Realizer
See CA-Realizer.



realtime
An immediate response.  It refers to process
control and embedded systems; for example, space
flight computers must respond instantly to changing
conditions.  It also refers to fast transaction
processing systems as well as any electronic
operation fast enough to keep up with its real-
world counterpart (animating complex images,
transmitting live video, etc.).



realtime clock
An electronic circuit that maintains the time of
day. It may also provide timing signals for
timesharing operations.



realtime compression
The ability to compress and decompress data without
any noticeable loss in speed compared to non-
compressed data.  PC products such as Stacker and
SuperStor let you create a separate compressed
drive on your hard disk.  All data written to that
drive is compressed and decompressed when read
back.  Realtime compression is included in DOS
starting with DOS 6.  See DOS DoubleSpace and
DriveSpace.  See JPEG.



realtime conferencing
See teleconferencing (3).



realtime image
A graphics image that can be animated on screen at
the same speed as the real-world object.



realtime information system
A computer system that responds to transactions by
immediately updating the appropriate master files
and/or generating a response in a time frame fast
enough to keep an operation moving at its required
speed.  See transaction processing.



realtime operating system
A master control program that can provide immediate
response to input signals and transactions.



realtime system
A computer system that responds to input signals
fast enough to keep an operation moving at its
required speed.



realtime video
The ability to transmit video live without missing
any frames.  It requires very high transmission
capacity.  See ATM.



reasonable test
A type of test that determines if a value falls
within a range considered normal or logical.  It
can be made on electronic signals to detect
extraneous noise as well as on data to determine
possible input errors.



reboot
To reload the operating system and restart the
computer.  See boot.



receiver
A device that accepts signals.  Contrast with
transmitter.



record
(1) A group of related fields that store data about
a subject (master record) or activity (transaction
record).  A collection of records make up a file.

   Master records contain permanent data, such as
account number, and variable data, such as balance
due.  Transaction records contain only permanent
data, such as quantity and product code.  See
master file and transaction file for examples of
record contents.

(2) In certain disk organization methods, a record
is a block of data read and written at one time
without any relationship to records in a file.



record format
Same as record layout.



record head
A device that writes a signal on tape.  Some tape
drives and all disk drives use a combination
read/write head.



record layout
The format of a data record, which includes the
name, type and size of each field in the record.



record locking
See file and record locking.



record mark
A symbol used to identify the end of a record.



record number
The sequential number assigned to each physical
record in a file.  Record numbers change when the
file is sorted or records are added and deleted.



records management
The creation, retention and scheduled destruction
of an organization's paper and film documents.
Computer-generated reports and documents fall into
the records management domain, but traditional data
processing files do not.



recovery
See backup & recovery, checkpoint/restart and tape
backup.



rectifier
An electrical circuit that converts AC into DC
current with the use of diodes that act as one-way
valves.  Contrast with inverter.



recursion
In programming, the ability of a subroutine or
program module to call itself.  It is helpful for
writing routines that solve problems by repeatedly
processing the output of the same process.



Red Book
(1) The documentation of the U.S. National Security
Agency that defines criteria for secure networks.
The volumes are "Trusted Network Interpretation of
the Trusted Computer System Evaluation Criteria"
(NCSC-TG-005) and "Trusted Network Interpetation
Environments Guideline: Guidance for Applying the
Trusted Network Interpretation" (NCSC-TG-011).  It
is the network counterpart of the Orange Book for
computers.  See NCSC.

(2) The documentation for the technical
specification of audio CDs, which includes such
details as sampling and transfer rates.  "Red Book
audio" refers to digital sound that conforms to the
common standard used in music compact discs.  See
CD.



red green blue
See RGB.



redaction
The editing done to sensitive documents before
release to the public.



redirection
Diverting data from its normal destination to
another; for example, to a disk file instead of the
printer, or to a server's disk instead of the local
disk.  See DOS redirection and redirector.



redirector
In a LAN, software that routes workstation (client)
requests for data to the server.



redundancy check
In communications, a method for detecting
transmission errors by appending a calculated
number onto the end of each segment of data.  See
CRC.



reengineering
Using information technology to improve performance
and cut costs.  Its main premise, as popularized by
the book "Reengineering the Corporation" by Michael
Hammer and James Champy, is to examine the goals of
an organization and to redesign work and business
processes from the ground up rather than simply
automate existing tasks and functions.

   According to the authors, reengineering is
driven by open markets and competition.  No longer,
can we enjoy the protection of our own country's
borders as we could in the past.  Today, we are in
a global economy, and worldwide customers are more
sophisticated and demanding.

   In addition, modern industrialization was based
on theories of fragmentation and specialization,
which have led to the "left eye" specialist with
millions of workers doing dreary, monotonous jobs
as well as the creations of departments, functions
and business units governed by multiple layers of
management.  Management has been the necessary glue
to control the fragmented workplace.

   In order to be successful in the future, the
organization will have fewer layers of management
and fewer, but more highly-skilled workers that do
more complex tasks.  Information technology, used
for the past 50 years to automate manual tasks,
will be used to enable new work models.  The
successful organization will not be "technology
driven," rather it will be "technology enabled."

  Although reengineering may, in fact, reduce a
department of 200 employees down to 50, it is not
just about eliminating jobs.  It's goals are
customer oriented; for example, it's about
processing a contract in 24 hours instead of two
weeks or performing a telecommunications service in
one day instead of 30.  It's about reducing the
time it takes to get a drug to market from eight
years to four years or reducing the number of
suppliers from 200,000 to 700.

   Reengineering is about radical improvement, not
incremental changes.



reentrant code
A programming routine that can be used by multiple
programs simultaneously.  It is used in operating
systems and other system software as well as in
multithreading, where concurrent events are taking
place.  It is written so that none of its code is
modifiable (no values are changed) and it does not
keep track of anything.  The calling programs keep
track of their own progress (variables, flags,
etc.), thus one copy of the reentrant routine can
be shared by an any number of users or processes.

   Conceptually, it is as if several people were
each baking a cake from a single copy of a recipe
on the wall.  Everyone looks at the master recipe,
but keeps track of their own progress by jotting
down the step they are at on their own scratchpad
so they can pick up where they left off.  The
master recipe is never disturbed.



referential integrity
A database management safeguard that ensures every
foreign key matches a primary key.  For example,
customer numbers in a customer file are the primary
keys, and customer numbers in the order file are
the foreign keys.  If a customer record is deleted,
the order records must also be deleted otherwise
they are left without a primary reference.  If the
DBMS doesn't test for this, it must be programmed
into the applications.



reflection mapping
In computer graphics, a technique for simulating
reflections on an object.



Reflective Memory
A memory bus technology from Encore Computer that
allows simultaneous reads and writes to multiple
memories.  It is used in Encore's SMP computer
systems, in which memory is shared among multiple
CPUs.



reflective spot
A metallic foil placed on each end of a magnetic
tape.  It reflects light to a photosensor to signal
the end of tape.



reflective VGA
An LCD screen that needs bright ambient light for
viewing.  Backlit and sidelit screens are much
easier to see.



reformat
(1) To change the record layout of a file or
database.

(2) To initialize a disk over again.



refraction
The bending of light, heat or sound as it passes
through different materials.



refresh
To continously charge a device that cannot hold its
content.  CRTs must be refreshed, because the
phosphors hold their glow for only a few
milliseconds.  Dynamic RAM chips require refreshing
to maintain their charged bit patterns.



refresh rate
(1) The number of times per second that a device is
re-energized, such as a CRT or dynamic RAM chip.
See vertical scan frequency.

(2) In computer graphics, the time it takes to
redraw or redisplay an image on screen.



regenerator
(1) In communications, the same as a repeater.

(2) In electronics, a circuit that repeatedly
supplies current to a memory or display device that
continuously loses its charges or content.



ReGIS
(REmote Graphics InStruction)  A graphics language
from Digital used on graphics terminals and first
introduced on the PDP-11.



register
A small, high-speed computer circuit that holds
values of internal operations, such as the address
of the instruction being executed and the data
being processed.  When a program is debugged,
register contents may be analyzed to determine the
computer's status at the time of failure.

   In microcomputer assembly language programming,
programmers reference registers routinely.
Assembly languages in larger computers are often at
a higher level.



register level compatibility
A hardware component that is 100% compatible with
another device.  It implies that the same type,
size and names of registers are used.



regression analysis
A statistical technique for detecting relationships
among multiple properties of observations in a
sample.



related files
Two or more data files that can be matched on some
common condition, such as account number or name.



relational algebra
(1) The branch of mathematics that deals with
relations; for example, AND, OR, NOT, IS and
CONTAINS.

(2) In relational database, a collection of rules
for dealing with tables; for example, JOIN, UNION
and INTERSECT.



relational calculus
The rules for combining and manipulating relations;
for example De Morgan's law, "the complement of a
union is equal to the union of the complements."



relational database
A database organization method that links files
together as required.  In non-relational systems
(hierarchical, network), records in one file
contain embedded pointers to the locations of
records in another, such as customers to orders and
vendors to purchases.  These are fixed links set up
ahead of time to speed up daily processing.

   In a relational database, relationships between
files are created by comparing data, such as
account numbers and names.  A relational system has
the flexibility to take any two or more files and
generate a new file from the records that meet the
matching criteria (see join).

   Routine queries often involve more than one data
file.  For example, a customer file and an order
file can be linked in order to ask a question that
relates to information in both files, such as the
names of the customers that purchased a particular
product.

   In practice, a pure relational query can be very
slow.  In order to speed up the process, indexes
are built and maintained on the key fields used for
matching.  Sometimes, indexes are created "on the
fly" when the data is requested.

   The term was coined in 1970 by Edgar Codd, whose
objective was to easily accomodate a user's ad hoc
request for selected data.

      Relational terms     Common terms
      table or relation    file
      tuple                record
      attribute            field





relational operator
A symbol that specifies a comparison between two
values.

      Relational Operator        Symbol
   EQ   Equal to                   =
   NE   Not equal to               <>  or #  or !=
   GT   Greater than               >
   GE   Greater than or equal to   >=
   LT   Less than                  <
   LE   Less than or equal to      <=





relative address
A memory address that represents some distance from
a starting point (base address), such as the first
byte of a program or table.  The absolute address
is derived by adding it to the base address.



relative path
An implied path.  When a command is expressed that
references files, the current working directory is
the implied, or relative, path if the full path is
not explicitly stated.  Contrast with full path.



relative vector
In computer graphics, a vector with end points
designated in coordinates relative to a base
address.  Contrast with absolute vector.



relay
An electrical switch that allows a low power to
control a higher one.  A small current energizes
the relay, which closes a gate, allowing a large
current to flow through.



Relay Gold
A PC communications program from Microcom, Inc.,
Norwood, MA, that provides standard asynchronous
transmission as well as mainframe file transfer and
LAN support.



relocatable code
Machine language that can be run from any memory
location.  All modern computers run relocatable
code.  See base/displacement.



REM
(REMarks)  A programming language statement used to
document the program.  Rem statements are used in
DOS files as well.  For example, typing the word
REM in front of a line in AUTOEXEC.BAT or
CONFIG.SYS turns that line into comments and
prevents any executable function on that line from
taking place.



rem it out
To disable a command in a batch file or in
programming source code by placing the letters
"rem" (for remarks) in the beginning of the line.
Rem is used in DOS batch files as well as in BASIC
and some other languages, but it is not a universal
statement.  See REM and DOS Rem.



remedial maintenance
A repair service that is required due to a
malfunction of the product.  Contrast with
preventive maintenance.



remote access server
See RAS.



Remote Access Service
See RAS.



remote access software
See remote control software.



remote batch
See RJE.



remote communications
(1) Communicating via long distances.

(2) See remote control software.



remote console
A terminal or workstation in a remote location that
is used to monitor and control a local computer.



remote control software
Software, installed in both machines, that allows a
user at a local computer to have control of a
remote computer via modem.  Both users run the
remote computer and see the same screen.  Remote
control operation is used to take control of an
unattended desktop personal computer from a remote
location as well as to provide instruction and
technical support to remote users.

   Remote control is different than remote node.
In remote control, only screen updates are
transmitted to the remote machine as all processing
takes place in the local computer.  All file
transfers are done locally or over a high-speed
LAN.  In a remote node setup, the user is logged
onto the network using the phone line as an
extension to the network.  Thus, all traffic has to
flow over a low-speed telephone line.

   When working with large files, remote control is
faster than remote node, and it gives users the
flexibility to do whatever they want on the local
machine.  However, remote control sessions move
screen changes constantly to the remote machine and
graphics applications are slow.  Remote control
usually requires more network ports than remote
node for the same number of users.  In addition, in
remote control, you don't do any local processing
in the remote machine so online sessions are often
longer than with remote node.


                  REMOTE CONTROL
        REMOTE USER CONTROLS LOCAL CLIENT

  REMOTE             LOCAL               LOCAL
 PCĿ  Only     CLIENT            SERVER
 takes   screen           Data            
 over  <-changes->      <-transfer->      
 local ==========       ܳ      
 client   WAN        LAN      
                                        DATABASES

                 REMOTE NODE
    REMOTE USER LOGGED DIRECTLY ONTO SERVER

                    LOCAL
   REMOTE           MODEM             LOCAL
  CLIENT         SERVER          SERVER
  acts                                 
  like   <-----data transfer----->       
  local =========      ܳ      
  client   WAN      LAN    
                                     DATABASES





Remote Imaging Protocol
See RIP.



remote job entry
See RJE.



remote node
See remote control software.



remote-office router
A router specialized to route data to its
counterpart in a remote site.  Configuring the
router is done at the central site, thus network
administration is simplified.  3Com pioneered the
concept with its Boundary Routing.



remote procedure call
See RPC.



removable disk
A disk unit that is inserted into a disk drive for
reading and writing and removed when not required;
for example, floppy disks, disk cartridges and disk
packs.



render
To draw a real-world object as it actually appears.



rendering
In computer graphics, creating a 3-D image that
incorporates the simulation of lighting effects,
such as shadows and reflection.



Renderman interface
A graphics format from Pixar, Point Richmond, CA,
that uses photorealistic image synthesis.
Developer's Renderman (PCs and UNIX) and Mac
Renderman (Macintosh) are Pixar programs that apply
photorealistic looks and surfaces to 3-D objects.



Renovator
See ESL Renovator.



repeater
(1) A communications device that amplifies or
regenerates the data signal in order to extend the
transmission distance.  Available for both analog
and digital signals, it is used extensively in long
distance transmission.  It is also used to tie two
LANs of the same type together.  Repeaters work at
layer 1 of the OSI model.  See bridge and router.

(2) The term may also refer to a multiport
repeater, which is a hub in a 10BaseT network.



repetitive strain injury
See RSI.



Replica
Document exchange software from Farallon Computing,
Inc., Alameda, CA, that converts a Windows or
Macintosh document into a proprietary file format
for viewing on other machines.  The Replica viewer
can be distributed to the target machines or
embedded within the Replica document file itself,
turning it into a single-document viewer.



report
A printed or microfilmed collection of facts and
figures with page numbers and page headings.  See
report writer and query.



report file
A file that describes how a report is printed.



report format
The layout of a report showing page and column
headers, page numbers and totals.



report generator
Same as report writer.



Report Program Generator
See RPG.



report writer
Software that prints a report based on a
description of its layout.  As a stand-alone
program or part of a DBMS or file manager, it can
sort selected records into a new sequence for
printing.  It may also print standard mailing
labels.

   A report is described by entering text for the
page header and stating the position of the print
columns (data fields) and which ones are totalled
or subtotalled.  Once created, the description is
stored in a report file for future use.

   Developed in the early 1970s, report writers
(report generators) were the precursor to query
languages and were the first programs to generate
computer output without having to be programmed.



repository
A database of information about applications
software that includes author, data elements,
inputs, processes, outputs and interrelationships.
It may be the central core of a CASE system; for
example, Repository Manager in IBM's AD/Cycle is
designed to integrate third-party CASE products.



reproducer
An early tabulating machine that duplicated punched
cards.



reprographics
Duplicating printed materials using various kinds
of printing presses and high-speed copiers.



request for price quotation
See RPQ.



request for proposal
See RFP.



request to send
See RTS.



ResEdit
(Resource Editor)  A Macintosh system utility used
to edit the resource fork.



reserved word
A verb or noun in a programming or command language
that is part of the native language.



reset button
A computer button or key that reboots the computer.
All current activities are stopped cold, and any
data in memory is lost.  On a printer, the reset
button clears the printer's memory and readies it
to accept new data.



resident module
The part of a program that must remain in memory at
all times.  Instructions and data that stay in
memory can be accessed instantly.



resident program
A program that remains in memory at all times.  See
TSR.



resistor
An electronic component that resists the flow of
current in an electronic circuit.



resolution
(1) The degree of sharpness of a displayed or
printed character or image.  On screen, resolution
is expressed as a matrix of dots.  VGA resolution
of 640x480 means 640 dots across each of 480 lines.
Sometimes the number of colors are added to the
spec; for example, 640x480x16 or 640x480x256.  The
same resolution looks sharper on a small screen
than a large one.  See PC display modes.

   For printers, resolution is expressed as the
number of dots per linear inch.  300 dpi means
90,000 dots per square inch (300x300).  Laser
printers and plotters have resolutions from 300 to
1000 dpi and more, whereas most display screens
provide less than 100 dpi.  That means jagged lines
on screen may smooth out when they print.

(2) The number of bits used to record the value of
a sample in a digitized signal.  See sampling rate.



resolve
To change, transform or solve a problem.  The
phrase "external references are resolved" refers to
determining the addresses that link modules
together; that is, solving the unknown links.



resource compiler
In a graphical interface (GUI), software that
converts and links a resource (menu, dialog box,
icon, font, etc.) into the executable program.



resource fork
The resource part of a Macintosh file.  For
example, in a text document, it contains format
codes with offsets into the text in the data fork.
In a program, it contains executable code, menus,
windows, dialog boxes, buttons, fonts and icons.



resource requirements
The components of a system that are required by
software or hardware.  It refers to resources that
have finite limits such as memory and disk.  In a
PC, it may refer to the resources required to
install a new peripheral, namely IRQs, DMA
channels, I/O addresses and memory addresses.  All
of these are finite resources within the computer.
See PC conflicts.



response time
The time it takes for the computer to comply with a
user's request, such as looking up a customer
record.



restart
To resume computer opertion after a planned or
unplanned termination.  See boot, warm boot and
checkpoint/restart.



restricted function
A computer or operating system function that cannot
be used by an application program.



retrieve
To call up data that has been stored in a computer
system.  When a user queries a database, the data
is retrieved into the computer first and then
transmitted to the screen.



return key
Also called the enter key, the keyboard key used to
signal the end of a line of data or the end of a
command.  In word processing, return is pressed at
the end of a paragraph, and a return code is
inserted into the text at that point.  See CR.

        Ŀ Ŀ Ŀ
        { [ } ]       
                
          Ŀ       
          " '   Enter
           

     Standard Return Key Placement





reusability
The ability to use all or the greater part of the
same programming code or system design in another
application.



reverse engineer
To isolate the components of a completed system.
When a chip is reverse engineered, all the
individual circuits that make up the chip are
identified.  Source code can be reverse engineered
into design models or specifications.  Machine
language can be reversed into assembly langauge
(see disassembler).



reverse polish notation
A mathematical expression in which the numbers
precede the operation.  For example, 2 + 2 would be
expressed as 2 2 +, and 10 - 3 * 4 would be 10 3 4
* -.  See FORTH.



reverse video
A display mode used to highlight characters on
screen.  For example, if the normal display mode is
black on white, reverse video would be white on
black.



revision level
See version number.



REXX
(REstructured EXtended eXecutor)  An IBM mainframe
structured programming language that runs under
VM/CMS and MVS/TSO.  It can be used as a general-
purpose macro language that sends commands to
application programs and to the operating systems.
REXX is also included in OS/2 Version 2.0.

   The following REXX example converts Fahrenheit
to Celsius:

   Say "Enter Fahrenheit "
   Pull FAHR
   Say "Celsius is " (FAHR - 32) * (5 / 9)





RF
(Radio Frequency)  The range of electromagnetic
frequencies above the audio range and below visible
light.  All broadcast transmission, from AM radio
to satellites, falls into this range, which is
between 30KHz and 300GHz.  See RF modulation.



RF/ID
(Radio Frequency/IDentification)  An identification
system that uses tags that transmit a wireless
message.  The tag gets its power from a hand-held
gun/reading unit.



RF modulation
The transmission of a signal through a carrier
frequency.  In order to connect to a TV's antenna
input, some home computers and all VCRs provide RF
modulation of a TV channel, usually Channel 3 or 4.
See FCC class.



RF shielding
A material that prohibits electromagnetic radiation
from penetrating it.  Personal computers and
electronic devices used in the home must meet U.S.
government standards for electromagnetic
interference.



RFI
(Radio Frequency Interference)  High-frequency
electromagnetic waves that eminate from electronic
devices such as chips.



RFP
(Request For Proposal)  A document that invites a
vendor to submit a bid for hardware, software
and/or services.  It may provide a general or very
detailed specification of the system.



RFS
(Remote File System)  A distributed file system for
UNIX computers introduced by AT&T in 1986 with UNIX
System V Release 3.0.  It is similar to Sun's NFS,
but only for UNIX systems.



RFT
See DCA.



RGB
(Red Green Blue)  A video color generation method
that displays colors as varying intensities of red,
green and blue dots.  When all three are turned on
high, white is produced.  As intensities are
equally lowered, shades of gray are derived.  The
base color of the screen appears when all dots are
off.  See colors.



RGB monitor
(1) A video display screen that requires separate
red, green and blue signals from the computer.  It
generates a better image than composite signals
(TV) which merge the three colors together.  It
comes in both analog and digital varieties.

(2) Sometimes refers to a CGA monitor that accepts
digital RGB signals.



ribbon cable
A thin, flat, multiconductor cable that is widely
used in electronic systems; for example, to
interconnect peripheral devices to the computer
internally.



rich e-mail
E-mail annotated with voice messages.



rich text
(1) Text that includes formatting commands for
bold, italic, etc.  It may also refer to the mixing
of graphics with text.

(2) Text in Microsoft's RTF format.  See RTF.



RIFF
(Resource Interchange File Format)  A multimedia
data format jointly introduced by IBM and
Microsoft.  See MCI.



right justify
Same as flush right.



rightsizing
Selecting a computer system, whether micro, mini or
mainframe, that best meets the needs of the
application.



rigid disk
Same as hard disk.



ring
One stage or level in a set of prioritized stages
or levels, typically involved with security and
password protection.



ring network
A communications network that connects terminals
and computers in a continuous loop.



RIP
(1) (Raster Image Processor)  In computer graphics,
the hardware, software (or both) that prepares data
for the screen or printer, which is a raster output
device.  RIPs are designed to rasterize a specific
type of data, such as PostScript or vector graphics
images, as well as different kinds of raster data.

(2) (Routing Information Protocol)  A routing
protocol in TCP/IP and NetWare used to identify all
attached networks as well as the number of router
hops required to reach them.  The responses are
used to update a router's routing table.

(3) (Remote Imaging Protocol)  A graphics format
from TeleGrafix Communications, Inc., designed for
transmitting graphics over low-speed lines.  Using
a communications program that supports RIP enables
graphical interfaces to be used on a BBS with
respectable performance via modem.



RIPscrip
See RIP (3).



RISC
(Reduced Instruction Set Computer)  A computer
architecture that reduces chip complexity by using
simpler instructions.  RISC compilers have to
generate software routines to perform complex
instructions that were previously done in hardware
by CISC computers.  In RISC, the microcode layer
and associated overhead is eliminated.

   RISC keeps instruction size constant, bans the
indirect addressing mode and retains only those
instructions that can be overlapped and made to
execute in one machine cycle or less.  The RISC
chip is faster than its CISC counterpart and is
designed and built more economically.



RISC System/6000
See RS/6000.



Rivest-Shamir-Adleman
See RSA.



RJ-11
A four or six-wire telephone connector.  The four-
wire plug and socket is the common connector
between the handset and the telephone and for
plugging telephones and modems into wall outlets.


                               
                    
          
                            

            RJ-11                     RJ-45





RJ-45
An eight-wire telephone connector.



RJE
(Remote Job Entry)  Transmitting batches of
transactions from a remote terminal or computer.
The receiving computer processes the data and may
transmit the results back to the RJE site for
printing.  RJE hardware at remote sites can employ
teleprinters with disk or tape storage or complete
computer systems.



RLE
See run length encoding.



RLL
(Run Length Limited)  A magnetic disk encoding
method that packs 50% more bits into the same space
than the earlier MFM method.  It is used with RLL,
IDE, ESDI, SCSI, SMD and IPI interfaces.

   The "run length" is the number of consecutive 0s
before a 1 bit is recorded.  MFM is actually a run
length of 1,3; not less than one or more than three
"no pulses" separating adjacent pulses.  RLL
increases the run length over MFM; for example, RLL
2,7 means not less than two or more than seven 0s
before a 1 is recorded.  ARLL (Advanced RLL) is RLL
3,9.  See hard disk.



RLL interface
See ST506 RLL.



RMON
See SNMP.



RMS
(1) (Record Management Services)  A file management
system used in VAXs.

(2) (Root Mean Square)  A method used to measure
electrical output in volts and watts.



rn
(ReadNews)  A newsreader for reading the messages
in a newsgroup on the Internet.  See USENET.



RO terminal
(Receive Only terminal)  A printing device only (no
keyboard).



RoboCAD
A PC CAD program from Robo Systems International,
Inc., Newtown, PA, that includes a wide variety of
features and text functions.  It provides up to 256
colors and layers, has two drawing pages and a
scratch pad, and can transfer data to its solid
modeling program.



robot
A stand-alone hybrid computer system that performs
physical and computational activities.  It is a
multiple-motion device with one or more arms and
joints that is capable of performing many different
tasks like a human.  It can be designed similar to
human form, although most industrial robots don't
resemble people at all.

   It is used extensively in manufacturing for
welding, riveting, scraping and painting.  Office
and consumer applications are also being developed.
Robots, designed with AI, can respond to
unstructured situations.  For example, specialized
robots can identify objects in a pile, select the
objects in the appropriate sequence and assemble
them into a unit.

   Robots use analog sensors for recognizing real-
world objects and digital computers for their
direction.  Analog to digital converters convert
temperature, motion, pressure, sound and images
into binary code for the robot's computer.  The
computer directs the physical actions of the arms
and joints by pulsing their motors.



robotics
The art and science of the creation and use of
robots.



robust
Refers to software without bugs that handles
abnormal conditions well.  It is often said that
there is no software package totally bug free.  Any
program can exhibit odd behavior under certain
conditions, but a robust program will not lock up
the computer, cause damage to data or send the user
through an endless chain of dialog boxes without
purpose.  Whether or not a program can be totally
bug free will be debated forever.  See industrial
strength.



roll in/roll out
A swapping technique for freeing up memory
temporarily in order to perform another task.  The
current program or program segment is stored
(rolled out) on disk, and another program is
brought into (rolled in) that memory space.



rollback
A database management system feature that reverses
the current transaction out of the database,
returning the database to its former state.  This
is done when some failure interrupts a half-
completed transaction.



rollover
See n-key rollover.



ROM
(Read Only Memory)  A memory chip that permanently
stores instructions and data.  Its contents are
created at the time of manufacture and cannot be
altered.  ROM chips are used to store control
routines in personal computers (ROM BIOS),
peripheral controllers and other electronic
equipment.  They are also often the sole component
of a cartridge that plugs into printers, video
games and other systems.

   When computers are used in hand-held
instruments, appliances, automobiles and any other
such devices, the instructions for their routines
are generally stored in ROM chips or some other
non-volatile chip such as a PROM or EPROM.
Instructions may also be stored in a ROM section
within a general-purpose computer on a chip.  See
PROM, EPROM and EEPROM.  Contrast with RAM.



ROM BIOS
(ROM Basic Input Output System)  Instructions
contained in a ROM chip that activate peripheral
devices in a PC.  The motherboard has a system
BIOS, and an expansion card often has its own BIOS.

   The system BIOS includes routines for the
keyboard, screen, disk, parallel and serial port
and for internal services such as time and date.
It accepts requests from the device drivers in the
operating system as well as from application
programs.

   It also contains an autostart routine that tests
the system on startup and prepares the computer for
operation.  It searches for BIOSes on the plug-in
boards and sets up pointers (interrupt vectors) in
memory to access BIOS routines.  It then loads the
operating system and passes control to it.

   System BIOS's prior to 1990 may not be
compatible with new software and peripherals.  In
order to use devices such as 3.5" diskettes, 101-
key keyboards, IDE drives as well as provide
compatibility with Windows, NetWare and other
applications, you can upgrade an older PC with a
new BIOS.  The following firms specialize in ROM
BIOS upgrades:

     UNICORE SOFTWARE    800/800-BIOS
     1538 Turnpike St.
     N. Andover, MA 01845

     UPGRADES, ETC.      800/955-3527
     2432-A Palma Drive
     Ventura, CA 93003





ROM BIOS swapping
Alternating areas in the UMA (640K-1M) between ROM
BIOSs and applications as needed.



ROM card
A credit-card-sized module that contains permanent
software or data.  See memory card.



ROM emulator
A circuit that helps debug a ROM chip by simulating
the ROM with RAM.  The RAM circuit plugs into the
ROM socket.  Since RAM can be written over, whereas
ROM cannot, programming changes can be made easily.



ROMable
Machine language capable of being programmed into a
ROM chip.  Being "read only" the chip cannot be
updated and ROMable programs must use RAM or disk
for holding changing data.



root directory
In hierarchical file systems, the starting point in
the hierarchy.  When the computer is first started,
the root directory is the current directory.
Access to directories in the hierarchy requires
naming the directories that are in its path.

   In DOS, the command line symbol for the root
directory is a backslash (\).  In UNIX, it is a
slash (/).  See path, DOS Path and DOS abc's.



root mean square
See RMS.



rotational delay
The amount of time it takes for the disk to rotate
until the required location on the disk reaches the
read/write head.



round robin
Continuously repeating sequence, such as the
polling of a series of terminals, one after the
other, over and over again.



routable protocol
A communications protocol that contains a network
address as well as a device address, allowing data
to be routed from one network to another.  Examples
of routable protocols are SNA, OSI, TCP/IP, XNS,
IPX, AppleTalk and DECnet.  Contrast with non-
routable protocol.



router
A computer system in a network that stores and
forwards data packets between LANs and WANs.
Routers see the network as network addresses and
all the possible paths between them.  They read the
network address in a transmitted message and can
make a decision on how to send it based on the most
expedient route (traffic load, line costs, speed,
bad lines, etc.).  Routers work at the network
layer (layer 3 of the OSI model), whereas bridges
work at the data link layer (layer 2).

   Routers with high-speed buses in the gigabit
range can serve as an internet backbone,
interconnecting all networks in the enterprise.

   Routers can only route a message that is
transmitted by a routable protocol such as IPX and
IP.  Messages in non-routable protocols, such as
NetBIOS and LAT, cannot be routed, but they can be
transferred from LAN to LAN via a bridge.  Because
routers have to inspect the network address in the
protocol, they do more processing than a bridge and
add overhead to the network.

  In Novell terminology, a router is a network-
layer bridge.

   The major router vendors are Cisco Systems and
Wellfleet.  See bridge, brouter, gateway, hub and
intermediate node routing.



router protocol
A protocol used by routers to report their status
to other routers in the network and keep their
internal tables up-to-date.  See RIP and OSPF.



routine
A set of instructions that perform a task.  Same as
subroutine, module, procedure and function.



routing
See intermediate node routing and router.



Routing Information Protocol
See RIP.



routing protocol
A communications protocol used to update the
routing table in a router.



row
A horizontal set of data or components.  In a
graph, it is called the x-axis.  Contrast with
column.



RPC
(Remote Procedure Call)  A type of interface that
allows one program to call another in a remote
location.  Using a standard RPC allows an
application to be used in a variety of networks
without change.



RPG
(Report Program Generator)  One of the first
program generators designed for business reports,
introduced in 1964 by IBM.  In 1970, RPG II added
enhancements that made it a mainstay programming
language for business applications on IBM's
System/3x midrange computers.  RPG III, which added
more programming structures, is widely used on the
AS/400.  RPG statements are written in columnar
format.

   The following RPG III System/38-AS/400 example
changes Fahrenheit to Celsius.  The A lines are
Data Description Specs (DDS) code.  They define a
display file and are compiled separately.  The F
line links RPG code (C lines) to the A lines:

A   R FHEITR
A                         6 18'Enter Fahrenheit: '
A     FRHEIT    3Y  0B    6 42DSPATR(PC)
A                             EDTCDE(J)
A                         9 18'Celsius is '
A     CGRADE    3Y  0B    9 42DSPATR(PC)
A                             EDTCDE(J)
FFHEITD   CF   E        WORKSTN
C               EXFMTFHEITR
C               Z-ADDO          CGRADE
C      FRHEIT   SUB    32       CGRADE
C      CGRADE   MULT   5        CGRADE
C      CGRADE   DIV    9        CGRADE    H
C               EXFMTFHEITR





rpm
(Revolutions Per Minute)  The measurement of the
rotational speed of a disk drive.  Floppy disks
rotate at 300 rpm, while hard disks rotate from
2,400 to 3,600 rpm and more.



RPN
See reverse polish notation.



RPQ
(Request for Price Quotation)  A document that
requests a price for hardware, software or services
to solve a specific problem.  It is created by the
customer and delivered to the vendor.



RS-170
An NTSC standard for composite video signals.



RS-232
(Recommended Standard-232)  A TIA/EIA standard for
serial transmission between computers and
peripheral devices (modem, mouse, etc.).  It uses a
25-pin DB-25 or 9-pin DB-9 connector.  Its normal
cable limitation of 50 feet can be extended to
several hundred feet with high-quality cable.

   RS-232 defines the purpose and signal timing for
each of the 25 lines; however, many applications
use less than a dozen.  RS-232 transmits positive
voltage for a 0 bit, negative voltage for a 1.

   In 1984, this interface was officially renamed
TIA/EIA-232-E standard (E is the current revision,
1991), although most people still call it RS-232.


              Pin Settings for Plug
           (Reverse order for socket.)
   
     1  2  3  4  5  6  7  8  9  10 11 12 13
      14 15 16 17 18 19 20 21 22 23 24 25
      

               
                 1  2  3  4  5
                   6  7  8  9
                   


  25 pin                            9 pin
    1 - PG   Protective ground
    2 - TD   Transmitted data         3
    3 - RD   Received data            2
    4 - RTS  Request to send          7
    5 - CTS  Clear to send            8
    6 - DSR  Data set ready           6
    7 - SG   Signal ground            5
    8 - CD   Carrier detect           1
    9 - + voltage (testing)
   10 - - voltage (testing)
   11 - 
   12 - SCD  Secondary CD
   13 - SCS  Secondary CTS
   14 - STD  Secondary TD
   15 - TC   Transmit clock
   16 - SRD  Secondary RD
   17 - RC   Receiver clock
   18 - 
   19 - SRS  Secondary RTS
   20 - DTR  Data terminal ready      4
   21 - SQD  Signal quality detector
   22 - RI   Ring indicator           9
   23 - DRS  Data rate select
   24 - XTC  External clock
   25 - 





RS-422, 423
A TIA/EIA standards for serial interfaces that
extend distances and speeds beyond RS-232.  RS-422
is a balanced system requiring more wire pairs than
RS-423 and is intended for use in multipoint lines.
They use either a 37-pin connector defined by RS-
449 or a 25-pin connector defined by RS-530.

   RS-449 and RS-530 specify the pin definitions
for RS-422 and RS-423.  RS-422/423 specify
electrical and timing characteristics.



RS-449
Defines a 37-pin connector for RS-422 and RS-423
circuits.



RS-485
A TIA/EIA standard for multipoint communications
lines.  It can be implemented with as little as a
wire block with four screws or with DB-9 or DB-37
connectors.  By using lower-impedance drivers and
receivers, RS-485 allows more nodes per line than
RS-422.



RS-530
Defines a 25-pin connector for RS-422 and RS-423
circuits.  It allows for higher speed transmission
up to 2Mbits/sec over the same DB-25 connector used
in RS-232, but is not compatible with it.



RS/6000
(RISC System/6000)  IBM family of RISC-based
computer systems introduced in 1990.  It comes in
workstation (POWERstation) and server (POWERserver)
models and uses the Micro Channel bus.  It
introduced Version 3 of AIX and two graphical user
interfaces: AIXwindows Environment/6000 (enhanced X
Window system) and AIX NeXTStep Environment/6000
from NeXT Computer.

   RS/6000s started out using IBM's RISC chip,
called POWER.  Starting in 1993, certain models
began using the PowerPC chip, a single-chip version
of the POWER architecture, which was enhanced by
Motorola and Apple.  Software is compatible on both
platforms, unless it uses PowerPC-only
instructions.  New models of the RS/6000s will use
the PowerPC chip.



RS232
See RS-232.



RSA
(Rivest-Shamir-Adleman)  A highly-secure encryption
method by RSA Data Security, Inc., Redwood City,
CA, that uses a two-part key.  The private key is
kept by the owner; the public key is published.

   Data is encrypted by using the recipient's
public key, which can only be decrypted by the
recipient's private key.  RSA is very computation
intensive, thus it is often used to create an "RSA
digital envelope," which holds an RSA-encrypted DES
key and DES-encrypted data.

   RSA is also used for authentication.  You can
verify who you are with a digital signature by
encrypting with your private key and letting others
decrypt your message with your public key.  This
requires the sender to compute a hash value of the
message being sent, which is encrypted along with
the message.  The recipient decrypts the hash value
and computes the hash value from the message using
the same algorithm.  If they match, the signature
is authenticated.

   The RSA algorithm is also implemented in
hardware.  As RSA chips get faster, RSA encoding
and decoding add less overhead to the operation.
For more on public keys, see encryption.



RSCS
(Remote Spooling Communications Subsystem)
Software that provides batch communications for
IBM's VM operating system.  It accepts data from
remote batch terminals, executes them on a priority
basis and transmits the results back to the
terminals.  The RSCS counterpart in MVS is called
JES.  Contrast with CMS, which provides interactive
communications for VM.



RSI
(Repetitive Strain Injury)  Ailments of the hands,
neck, back and eyes due to computer use.  The
remedy for RSI is frequent breaks which should
include stretching or yoga postures.  See carpal
tunnel syndrome.



RSTS/E
A PDP-11 operating system from Digital.



RSX-11
(Resource Sharing eXtension-PDP 11)  A multiuser,
multitasking operating system from Digital that
runs on its PDP-11 series.



RT
A RISC-based workstation from IBM introduced in
1986 that was superseded by the RS/6000 family.



RT-11
A single user, multitasking operating system from
Digital that runs on its PDP-11 series.



RTF
(Rich Text Format)  A Microsoft standard for
encoding formatted text and graphics.  It was
adapted from IBM's DCA format and supports ANSI,
IBM PC and Macintosh character sets.



RTFM
(Read The Flaming Manual)  The last resort when
having a hardware or software problem!



RTOS
(RealTime Operating System)  An operating system
designed for use in a realtime computer system.
See realtime system, embedded system, process
control and OS/9.



RTS
(Request To Send)  An RS-232 signal sent from the
transmitting station to the receiving station
requesting permission to transmit.  Contrast with
CTS.



rubber banding
In computer graphics, the moving of a line or
object where one end stays fixed in position.



rubout key
A keyboard key on a terminal that deletes the last
character that was entered.



rule-based expert system
An expert system based on a set of rules that a
human expert would follow in diagnosing a problem.
Contrast with model-based expert system.



ruler line
A graphic representation of a ruler on screen that
is used for laying out text and graphics.



rules
(1) A set of conditions or standards which have
been agreed upon.

(2) In printing, horizontal and vertical lines
between columns or at the top and bottom of a page
in order to enhance the appearance of the page.



RUMBA
A PC-to-host connectivity software from Wall Data,
Redmond, WA.  It provides a Windows front end to
IBM mainframes, AS/400s and VAXes and supports a
variety of network configurations.



run
(1) To execute a program.

(2) A single program or set of programs scheduled
for execution.



run around
In desktop publishing, the flowing of text around a
graphic image.



run length encoding
A simple data compression method that converts a
run of identical symbols as a symbol followed by a
count.  A rough example might be []36* where [] is
a code and 36* means 36 *'s follow.



run length limited
See RLL.



run native
To "run native" is to execute software written for
the native mode of the computer.  Contrast with
running a program under some type of emulation or
simulation.

   Running native has traditionally been the
fastest way to execute instructions on a computer.
However, if as expected in the future, machines are
so fast they can run emulated programs without any
noticeable delay to the user, this will no longer
be the important issue it is today.



run on top of
To run as the control program to some other
program, which is subordinate to it.  Contrast with
run under.



run time
See runtime.



run under
To run within the control of a higher-level
program.  Contrast with run on top of.



runtime
Refers to the actual execution of a program.



runtime version
Software that enables another program to execute on
its own or with enhanced capabilities.  For
example, a full-featured database management system
(DBMS) includes a programming language for
developing applications.  The language is generally
an interpreted one, which means that the DBMS
software must be loaded into the computer in order
to run the programs (see interpreter).  A runtime
version of the DBMS would allow the developer to
create the application in that language and to
package it for customers that have not purchased
the DBMS.  The runtime version "runs" the
application, but does not allow the user access to
all the bells and whistles that the owner of the
full DBMS has.

   In the book "Dvorak Predicts," published by
Osborne McGraw-Hill, the well-known computer
columnist, John Dvorak, proposes an interesting
runtime version.  He says that Apple should create
a "runtime Mac."  As an example, he uses an
automobile tune-up kit, suggesting that its probes
to the spark plugs, exhaust pipe, etc., be
controlled by a computer using the Mac interface
for that application only.  He claims that the
advantages are lower hardware costs if a full-blown
Mac isn't required and that the Mac's interface
would become widely known if runtime Macs were used
for many specialized jobs.



RXD
(Receiving Data)  See modem.



S-100 bus
An IEEE 696, 100-pin bus standard used extensively
in first-generation personal computers (8080, Z80,
6800, etc.).  It is still used in various systems.



S/360
See System/360.



S/370
See System/370.



S/3x
See System/3x.



S-RAM
See static RAM.



S-VHS
(Super-VHS)  A video recording and playback system
that uses a higher-quality VHS cassette and the S-
video technology.  VCRs that support S-VHS can also
record and play back normal VHS tapes.



S-video
(Super-video)  A video technology, also called Y/C
video, that records and maintains luminance (Y) and
color information (C) separately.  S-VHS and Hi-8
cameras and VCRs use this method, which provide a
better color image than standard VHS and 8mm
formats.  S-video hookups use a special 5-pin
connector rather than the common RCA phono plug.



s/w
See software.



S3 chip
Refers to one of the graphics accelerator chips
(86C911, 86C928, etc.) from S3, Inc., San Jose, CA,
used in a variety of graphics accelerator boards.



SAA
(System Application Architecture)  Introduced in
1987, SAA is a set of standards from IBM that
provide consistency across all IBM platforms.  It
governs user interfaces, programming interfaces and
communications protocols.  Categories are Common
User Access (CUA), Common Programming Interface for
Communications (CPI-C) and Common Communications
Support (CCS).  See CUA, CPI-C and CCS.



sabermetrician
Slang for a statistician who uses computers to
predict future performance of sports teams and
players.



sag
(1) A momentary drop in voltage from the power
source.  Contrast with spike.

(2) (SAG) (SQL Access Group)  See CLI.



SAM
(1) (Symantec AntiVirus for Macintosh)  A popular
Macintosh antivirus program from Symantec
Corporation, Cupertino, CA.

(2) See sequential access method.



Samna
One of the first full-featured word processors for
PCs (1983) from Samna Corporation, now part of
Lotus.



sampling
(1) In statistics, the analysis of a group by
determining the characteristics of a significant
percentage of its members chosen at random.

(2) In digitizing operations, the conversion of
real-world signals or movements at regular
intervals into digital code.  See sampling rate and
oversampling.



sampling rate
In digitizing operations, the frequency with which
samples are taken and converted into digital form.
The sampling frequency must be at least twice that
of the analog frequency being captured.  For
example, the sampling rate for hi-fi playback is
44.1KHz, slightly more than double the 20KHz
frequency a person can hear.  The higher the
sampling rate, the closer real-world objects are
represented in digital form.

   Another attribute of sampling is quantizing,
which creates a number for the sample.  The larger
the maximum number, also called resolution or
precision, the more granularity of the scale and
the more accurate the digital sampling.  See
oversampling.



sans-serif
A typeface style without serifs, which are the
short horizontal lines added at the tops and
bottoms of the vertical member of the letter.
Helvetica is a common sans-serif font.



SAP
(1) (Service Advertising Protocol)  A NetWare
protocol used to identify the services and
addresses of servers attached to the network.  The
responses are used to update a table in the router
known as the Server Information Table.

(2) (Secondary Audio Program)  An NTSC audio
channel used for auxiliary transmission, such as
foreign language broadcasting or teletext.



SAS System
(1) Originally called the "Statistical Analysis
System," SAS is an integrated set of data
management tools from SAS Institute Inc., Cary, NC,
that runs on PCs to mainframes.  It includes a
complete programming language as well as modules
for spreadsheets, CBT, presentation graphics,
project management, operations research,
scheduling, linear programming, statistical quality
control, econometric and time series analysis and
mathematical, engineering and statistical
applications.

(2) See FDDI.



SASI
(Shugart Associates Systems Interface)  A
peripheral interface developed by Shugart and NCR
in 1981 that evolved into the ANSI SCSI standard in
1986.



satellite
See communications satellite


satellite channel
A carrier frequency used for satellite
transmission.



satellite computer
A computer located remotely from the host computer
or under the control of the host.  It can function
as a slave to the master computer or perform
offline tasks.



satellite link
A signal that travels from the earth to a
communications satellite and back down again.
Contrast with terrestrial link.



saturation
(1) On magnetic media, a condition in which the
magnetizable particles are completely aligned and a
more powerful writing signal will not improve the
reading back.

(2) In a bipolar transistor, a condition in which
the current on the gate (the trigger) is equal to
or greater than what is necessary to close the
switch.

(3) In a diode, a condition in which the diode is
fully conducting.



save
To copy the document, record or image being worked
on onto a storage medium.  Saving updates the file
by writing the data that currently resides in
memory (RAM) onto disk or tape.  Most applications
prompt the user to save data upon exiting.

   All processing is done in memory (RAM).  When
the processing is completed, the data must be
placed onto a permanent storage medium such as disk
or tape.



save as
To copy the document or image being worked on onto
a storage medium as a new file.  "Save as" provides
an easy way to make multiple copies of a document
or image.  With your document or image on screen,
select "Save as" from the File menu.  You will be
prompted for a new file name.



SBC
See single board computer.



Sbus
Originally a proprietary bus from Sun, the Sbus has
been released into the public domain.  The IEEE
standardized a 64-bit version in 1993.



SC connector
A fiber-optic cable connector that uses a push-pull
latching mechanism.  It is used in FDDI, Fiber
Channel and B/ISDN applications.  See SMA connector
and ST connector.



SCAI
(Switch-to-Computer Applications Interface)  A
standard for integrating computers to a PBX.  See
switch-to-computer.



scalability
The ability to expand.  Implies minimal change in
current procedures in order to accomodate growth.



scalable
Capable of being changed in size and configuration.



scalable font
A font that is created in the required point size
as needed to display or print a document.  The dot
patterns (bitmaps) are generated from a set of
outline fonts, or base fonts, which contain a
mathematical representation of the typeface.
Although a bitmapped font designed from scratch for
a particular font size will always look the best,
scalable fonts eliminate storing dozens of
different font sizes on disk.  Contrast with
bitmapped font.

   The two major scalable fonts are Adobe's Type 1
PostScript and Apple/Microsoft's TrueType.  There
are more Type 1 fonts available, although TrueType
fonts are rapidly becoming as abundant.  Agfa's
Intellifont and Bitstream's Speedo fonts are also
used.



scalar
A single item or value.  Contrast with vector and
array, which are made up of multiple values.



scalar processor
A computer that performs arithmetic computations on
one number at a time.  Contrast with vector
processor.



scalar variable
In programming, a variable that contains only one
value.



scale
(1) To resize a device, object or system, making it
larger or smaller.

(2) To change the representation of a quantity in
order to bring it into prescribed limits of another
range.  For example, values such as 1249, 876, 523,
-101 and -234 might need to be scaled into a range
from -5 to +5.

(3) To designate the position of the decimal point
in a fixed or floating point number.



scan
(1) In optical technologies, to view a printed form
a line at a time in order to convert images into
bitmapped representations, or to convert characters
into ASCII text or some other data code.

(2) In video, to move across a picture frame a line
at a time, either to detect the image in an analog
or digital camera, or to refresh a CRT display.

(3) To sequentially search a file.



scan head
An optical sensing device in an scanner or fax
machine that is moved across the image to be
scanned.



scan line
One of many horizontal lines in a graphics frame.



scan rate
The number of times per second a scanning device
samples its field of vision.  See horizontal scan
frequency.



ScanDisk
See DOS ScanDisk.



ScanJet
A family of popular desktop scanners from HP.
Monochrome and color models are available.



scanner
A device that reads text, images and bar codes.
Text and bar code scanners recognize printed fonts
and bar codes and convert them into a digital code
(ASCII or EBCDIC).  Graphics scanners convert a
printed image into a video image (raster graphics)
without recognizing the actual content of the text
or pictures.  See flatbed scanner, sheet-fed
scanner, hand-held scanner and drum scanner.



scatter diagram
A graph plotted with dots or some other symbol at
each data point.  Also called a scatter plot or dot
chart.



scatter plot
Same as scatter diagram.



scatter read
The capability that allows data to be input into
two or more noncontiguous locations of memory with
one read operation.  See gather write.



SCbus
See SCSA.



SCERT II
(Systems and Computers Evaluation and Review
Technique)  Pronounced "skirt."  Software from
Pinnacle Software Corporation, Washington, DC, that
measures the performance of a system by modeling
the computer environment and applications.



scheduler
The part of the operating system that initiates and
terminates jobs (programs) in the computer.  Also
called a dispatcher, it maintains a list of jobs to
be run and allocates computer resources as
required.



scheduling algorithm
A method used to schedule jobs for execution.
Priority, length of time in the job queue and
available resources are examples of criteria used.



schema
The definition of an entire database.  See
subschema.



Scheme
A LISP dialect developed at MIT and Indiana
University.  TI has a personal computer version of
Scheme called PC Scheme.



Schottky
A category of bipolar transistor known for its fast
switching speeds in the three-nanosecond range.
Schottky II devices have switching speeds in the
range of a single nanosecond.



SCI
(Scalable Coherent Interface)  An IEEE standard for
a high-speed bus that uses wire or fiber optic
cable.  It can transfer data up to 1GBytes/sec.



scientific application
An application that simulates real-world activities
using mathematics.  Real-world objects are turned
into mathematical models and their actions are
simulated by executing the formulas.

   For example, some of an airplane's flight
characteristics can be simulated in the computer.
Rivers, lakes and mountains can be simulated.
Virtually any objects with known characteristics
can be modeled and simulated.

   Simulations use enormous calculations and often
require supercomputer speed.  As personal computers
become more powerful, more laboratory experiments
will be converted into computer models that can be
interactively examined by students without the risk
and cost of the actual experiments.



scientific computer
A computer specialized for high-speed mathematic
processing.  See array processor and floating point
processor.



scientific language
A programming language designed for mathematical
formulas and matrices, such as ALGOL, FORTRAN and
APL.  Although all programming languages allow for
this kind of processing, statements in a scientific
language make it easier to express these actions.



scientific notation
The display of numbers in floating point form.  The
number (mantissa) is always equal to or greater
than one and less than 10, and the base is 10.  For
example, 2.345E6 is equivalent to 2,345,000.  The
number following E (exponent) represents the power
to which the base should be raised (number of zeros
following the decimal point). 


scissoring
In computer graphics, the deleting of any parts of
an image which fall outside of a window that has
been sized and laid over the original image.  Also
called clipping.



SCL
(1) (Switch-to-Computer Link)  Refers to
applications that integrate the computer through
the PBX.  See switch-to-computer.

(2) A file extension used for ColoRIX raster
graphics file format (640x400 256 colors).



SCM
(1) (Software Configuration Management)  See
configuration management.

(2) (Service Control Manager)  The part of Windows
NT that launches background tasks.  Developers can
write executable programs that run under the
control of the SCM.

(3) (Single Chip Module)  A chip package that
contains one chip.  Contrast with MCM.



SCM file
(ScreenCam Movie file)  A file created by Lotus'
ScreenCam recorder program.



SCO
(The Santa Cruz Operation, Inc., Santa Cruz, CA)  A
system software company that specializes in UNIX
operating systems.  Its first operating system was
SCO XENIX in 1984 which ran on the Apple Lisa, IBM
PC XT and the DEC Pro 350.  Subsequently, all SCO
products were developed for Intel's x86 machines.
As of 1994, with nearly one million installed nodes
and 15 years in the business, SCO is the leader in
UNIX operating systems for the Intel platform.



SCO Merge
Software from SCO that adds DOS capability to SCO
UNIX.  It includes a licensed copy of DOS 5.0 and
can run DOS applications and Windows applications
in Standard Mode.



SCO MPX
(SCO MultiProcessor EXtension)  Software that adds
SMP capability to SCO Open Server operating
systems.



SCO Open Desktop
A UNIX-based, single-user client operating system
from SCO for 386s and up.  It is based on SCO UNIX
and includes the Motif and X Window user
interfaces, standard UNIX networking (TCP/IP, NFS
and NIS) as well as LAN Manager and NetBIOS
support.  It also includes SCO Merge, for DOS and
Windows compatibility.



SCO Open Server
A family of server operating systems from SCO based
on SCO UNIX.  SCO Open Server Network System
includes standard UNIX networking (TCP/IP, NFS and
NIS) and IPX/SPX support.  SCO Open Server
Enterprise System adds additional features such as
the Motif and X Window user interfaces and SCO
Merge (DOS and Windows compatibility).



SCO UNIX
A version of UNIX System V Release 3.2 for 386s and
up from SCO.  SCO UNIX has more security,
networking and standards conformance than SCO XENIX
and is the foundation of SCO's Open Desktop and
Open Server products.  SCO UNIX servers are used to
support dumb terminals as well as Windows, X
terminal and SCO Open Desktop clients.



SCO VP/ix
Software from SCO that adds DOS capability to
machines running SCO XENIX.  It includes a licensed
copy of DOS.



SCO XENIX
A version of UNIX System V for 286 PCs and up from
SCO.  Developed by Microsoft, it was the original
UNIX system for personal computers.  SCO XENIX is a
fast multiuser operating system that takes less
memory than SCO UNIX and is used in a variety of
vertical market applications for small workgroups.



scope
(1) A CRT screen, such as used on an oscilloscope
or common display terminal.

(2) In programming, the visibility of variables
within a program; for example, whether one function
can use a variable created in another function.

(3) In dBASE, a range of records, such as the "next
50" or "current record to end of file."


scrambler
A device or software program that encodes data for
encryption.



scrambling
Encoding data to make it indecipherable.  See
encryption, DES and RSA.



Scrapbook
A Macintosh disk file that holds frequently-used
text and graphics objects, such as a company
letterhead.  Contrast with Clipboard, which holds
data only for the current session.



scratch tape
A magnetic tape that can be erased and reused.



scratchpad
A register or reserved section of memory or disk
used for temporary storage.



screen
The display area of a video terminal or monitor.
It is either a CRT or one of the flat panel
technologies.



screen angle
The angle at which a halftone screen is placed over
an image, typically 45.



screen capture
Transfering the current on-screen image to a text
or graphics file.



screen dump
Printing the current on-screen image.  In PCs,
pressing Shift-PrtSc prints the screen.  If the
screen contains graphics, the DOS Graphics utility
must be loaded.  Third party screen capture
programs also dump graphic screens to the printer
or to disk.

   In the Macintosh, pressing Command-shift-3
creates a MacPaint file of the current screen.

   In Windows, pressing PrintScreen places a copy
of the current screen into the Clipboard.  See Win
Print screen.



screen font
A font used for on-screen display.  For true
WYSIWYG systems, screen fonts must be matched as
close as possible to the printer fonts.  Contrast
with printer font.



screen frequency
The resolution of a halftone.  It is the density of
dots (how far they're spaced apart from each other)
measured in lines per inch.



screen modes
See PC display modes.



screen overlay
(1) A clear, fine-mesh screen that reduces the
glare on a video screen.

(2) A clear touch panel that allows the user to
command the computer by touching displayed buttons
on screen.

(3) A temporary data window displayed on screen.
The part of the screen that was overlaid is saved
and restored when the screen overlay is removed.



screen resolutions
See PC display modes.



screen saver
A utility that prevents a CRT from being etched by
an unchanging image.  After a specified duration
without keyboard or mouse input, it blanks the
screen or displays moving objects.  Pressing a key
or moving the mouse restores the screen.

   It would actually take many hours to burn in an
image on today's color monitors.  However, the
entertainment provided by these utilities (swimming
fish, flying toasters, etc.) has made them very
popular.



screen scraper
Also called frontware, it is software that adds a
graphical user interface to character-based
mainframe and minicomputer applications.  The
screen scraper application runs in the personal
computer which is used as a terminal to the
mainframe or mini via 3270 or 5250 emulation.

   Popular screen scrapers are Knowledgeware's
Flashpoint, Mozart Systems Corporation's Mozart and
Easel's ESL Renovator.  DCA's QuickApp adds screen
scraper capability to development systems such as
PowerBuilder, Visual Basic and SQLWindows.



ScreenCam
Screen recording software from Lotus that is used
to make "movies" of software actions for demos and
training purposes.  Voice annotations can be added
with a microphone and sound card.  A runtime
player, which can be freely distributed, plays the
.SCM files.  The player can also be combined with
the file, providing a self-running ScreenCam movie.



script
(1) A typeface that looks like handwriting or
calligraphy.

(2) A program written in a special-purpose
programming language such as used in a
communications program or word processor.  Same as
macro.



ScriptX
A multimedia technology from Kaleida Labs, Inc.
that includes data formats, a scripting language
and a runtime environment.  It is designed for
creating applications that can be played on a
variety of personal computers and consumer
electronic devices.



scroll
To continuously move forward, backward or sideways
through the images on screen or within a window.
Scrolling implies continuous and smooth movement, a
line, character or pixel at a time, as if the data
were on a paper scroll being rolled behind the
screen.



scroll arrow
On-screen arrow that is clicked in order to scroll
the screen in the corresponding direction.  The
screen moves one line, or increment, with each
mouse click.



scroll back buffer
Reserved memory that holds a block of transmitted
data, allowing the user to browse back through it.



scroll bar
A horizontal or vertical bar that contains a box
that looks like an elevator in a shaft.  The bar is
clicked to scroll the screen in the corresponding
direction, or the box (elevator, thumb) is clicked
and then dragged to the desired direction.



Scroll Lock
On PC keyboards, a key used to toggle between a
scrolling and non-scrolling mode.  When on, the
arrow keys scroll the screen regardless of the
current cursor location.  This key is rarely used
for its intended purpose and may be used for just
about anything.  Most applications do not use it a
all.



scrollable
See scroll.



scrollable field
A short line on screen that can be scrolled to
allow editing or display of larger amounts of data
in a small display space.



scrollable window
A window that contains more data than is visible at
one time.  Its contents can be scrolled (moved up,
down, sideways within the window) in order to view
the entire document, image or list of items.



SCSA
(Signal Computing System Architecture)  An open
architecture from Dialogic Corporation for
transmitting signals, voice and video.  Its
backbone is the SCbus, a 131Mbps data path that
provides up to 2048 time slots, the equivalent of
1,024 two-way voice conversations at 64Kbps.



SCSI
(Small Computer System Interface)  Pronounced
"scuzzy."  SCSI is a hardware interface that allows
for the connection of up to seven peripheral
devices, such as a disk, tape or CD-ROM, to a
single SCSI expansion board, called a SCSI host
adapter (also called a SCSI controller), that plugs
into the computer.  The advantage of SCSI is that
seven different devices use up only one expansion
slot in the computer.

   However, the Macintosh, Sun and Digital
operating systems have supported SCSI directly, but
DOS has not, allowing various implementations of
SCSI drivers and host adapters to be developed for
the PC.  The SCSI host adapter and driver that
comes with a SCSI peripheral often work with only
that device or similar devices.  Thus when several
SCSI devices are used in a PC, multiple host
adapters are required, each taking up an expansion
slot.  Attempts at standardizing SCSI have resulted
in Adaptec's ASPI, ANSI's CAM and Microsoft's LADDR
specifications (see CorelSCSI and PowerSCSI!).

   SCSI is a bus structure itself and functions
like a mini-LAN connecting eight devices, but the
host adapter counts as one device.  SCSI allows any
two devices to communicate at one time (host to
peripheral, peripheral to peripheral).

   Each SCSI device can actually be broken up into
eight logical units as logical unit numbers (LUNs)
0 to 7, theoretically allowing up to 56 peripherals
to connect to one SCSI host adapter.  For example,
a jukebox for five disks could be LUN 0 to 4.  SCSI
devices can be built to take advantage of this
capability, but to date, most function only as a
single device (LUN 0).


               SCSI SPECIFICATIONS

                                   Maximum
                Bus width Pins in  Transfer rate
   Type           (bits)   cable   (MB/sec)

   SCSI-1              8    25        5
   SCSI-2              8    50        5
   Fast SCSI-2         8    50       10
   Fast Wide SCSI-2   16    68       20
   Fast Wide SCSI-2   32    68       40
   SCSI-3        16,  32    68      20-40


   SCSI-3 proposes enhanced features and the
ability to handle more than eight devices.  It also
supports serial transmission for small computers
such as palmtops.  See hard disk.


                SCSI and IDE Drives
You can install SCSI hard disk drives in a PC that
already contains one or two IDE disk drives.  The
IDE drive will still be the boot drive, and the
SCSI drives will provide additional storage.
Follow the instructions in your SCSI host adapter
manual carefully to make the correct settings.
SCSI host adapters usually provide floppy disk
control, which you will want to disable, otherwise
you would have two floppy disk controllers running
simultaneously.


                 Parallel to SCSI
There are adapters that allow SCSI peripherals to
be connected via the parallel port.  Although the
parallel port's transfer rate is considerably less
than the SCSI host adapter, it does provide a means
to hook up SCSI devices that might be otherwise
impossible, such as to a laptop with no expansion
slots.


           Single-Ended vs Differential
There are two types of SCSI signalling.  Single-
ended SCSI allows devices to be attached in a total
cable length of approximately 20 feet.
Differential SCSI increases this to about 80 feet.
Adapters can convert common single-ended SCSI
signals into differential SCSI that exceed 80 feet.

   Single-ended SCSI uses a data line and ground.
Differential SCSI uses data low and data high lines
to increase transmission distance.



scuzzy
See SCSI.



SDBN
(Software-Defined Broadband Network)  A future
high-bandwidth service from AT&T for data, voice
and video.  It uses ATM cell relay technology with
speeds up to 600 Mbits/sec.



SDF
(Standard Data Format)  A simple file format that
uses fixed length fields.  It is commonly used to
transfer data between different programs.


                    SDF

  Pat Smith     5 E. 12 St.       Rye         NY
  Robert Jones  200 W. Main St.   Palo Alto   CA

               Comma delimited

  "Pat Smith","5 E. 12 St.","Rye","NY"
  "Robert Jones","200 W. Main St.","Palo Alto","CA"





SDH
(Syncronous Digital Hierarchy)  The European
counterpart to SONET.  Speeds supported include 155
and 622 Mbits/sec and 2.5 GBits/sec.



SDI
(1) (Switched Digital International)  An AT&T dial-
up service providing 56 and 64 Kbits/sec digital
transmission to international locations.

(2) (Single Document Interface)  A Windows function
that allows an application to display and lets the
user work with only one document at a time.  SDI
applications require that the user load the
application again for the second and each
subsequent document to be worked on concurrently.
Contrast with MDI.

(3) (Standard Drive Interface)  A hard disk
interface for VAXs.

(4) (Serial Data Interface)  See serial interface.

(5) (Strategic Defense Initiative)  A high-tech
defense system for the U.S. proposed during the
Reagan administration.



SDK
(Software Developer's Kit)  See developer's toolkit
and Windows SDK.



SDLC
(Synchronous Data Link Control)  The primary data
link protocol used in IBM's SNA networks.  It is a
bit-oriented synchronous protocol that is a subset
of the HDLC protocol.



SDP
(Streaming Data Procedure)  A Micro Channel mode
that increases data transfer from 20MB per second
to 40MB per second.



SDRAM
(Synchronous DRAM)  A high-speed DRAM memory that
can transfer bursts of non-contiguous data at
100MBytes/sec.  JEDEC is also specifying SDRAM
standard.



SE
See systems engineer and Macintosh.



Seagate
(Seagate Technology, Inc., Scotts Valley, CA)  The
largest independent manufacturer of disk drives.
Founded in 1979 by Alan Shugart, Tom Mitchell and
Doug Mahon, it was the first to offer a 5MByte
drive using 5.25" platters making it ideal for the
burgeoning desktop computer industry.  Seagate
became the first company to ship 10 million drives.
In 1989, it aquired Imprimis Technology, a CDC
subsidiary making workstation and mainframe drives,
nearly doubling Seagate's revenue to $2.5 billion.
Seagate's 1993 revenues were three billion.



SEAlink
A version of Xmodem that uses a sliding window
protocol, transmits file name, date and size and
provides batch file transfer.  Good for delay-
introduced transmissions (packet switching,
satellites).



seamless integration
An addition of a new application, routine or device
that works smoothly with the existing system.  It
implies that the new feature can be activated and
used without problems.  Contrast with transparent,
which implies that there is no discernible change
after installation.



search and replace
To look for an occurrence of data or text and
replace it with another set of data or text.



search key
In a search routine, the data entered and used to
match other data in the database.



search path
The route to a particular file.  See path.



seashell
The "C" shell in UNIX.  See UNIX.



SECAM
(Systeme Electronique Couleur Avec Memoire)  A
French and Eastern European color TV standard that
broadcasts an analog signal at 819 lines of
resolution 25 interlaced frames per second (50 half
frames per second).  Mostly used in France, it is
slowly being switched over to the European PAL
standard.  Contrast with NTSC and PAL.



second-generation computer
A computer made of discrete electronic components.
In the early 1960s, the IBM 1401 and Honeywell 400
were examples.



second source
An alternative supplier of an identical or
compatible product.  A second source manufacturer
is one that holds a license to produce a copy of
the original product from another manufacturer.



secondary channel
In communications, a subchannel that is derived
from the main channel.  It is used for diagnostic
or supervisory purposes, but does not carry data
messages.



secondary index
An index that is maintained for a data file, but
not used to control the current processing order of
the file.  For example, a secondary index could be
maintained for customer name, while the primary
index is set up for customer account number.  See
primary index.



secondary storage
External storage, such as disk and tape.



secret key
See encryption.



sector
The smallest unit of storage read or written on a
disk.  See magnetic disk.



sector interleave
Sector numbering on a hard disk.  A one to one
interleave (1:1) is sequential: 0,1,2,3, etc.  A
2:1 interleave staggers sectors every other one:
0,4,1,5,2,6,3,7.

   In 1:1, after data in sector 1 is read, the disk
controller must be fast enough to read sector 2,
otherwise the beginning of sector 2 will pass the
read/write head and must rotate around to come
under the head again.  If it isn't fast enough, a
2:1 or 3:1 interleave gives it time to read all
sectors in a single rotation, eliminating wasted
rotations.

   The best interleave depends on the disk and disk
controller.  It can be changed with a low-level
format program.



sector map
See sector interleave.



sector sparing
Maintaining a spare sector per track to be used if
another sector becomes defective.



security
The protection of data against unauthorized access.
Programs and data can be secured by issuing
identification numbers and passwords to authorized
users of a computer.  However, systems programmers,
or other technically competent individuals, will
ultimately have access to these codes.

   Passwords can be checked by the operating system
to prevent users from logging onto the system in
the first place, or they can be checked in
software, such as DBMSs, where each user can be
assigned an individual view (subschema) of the
database.  Any application program running in the
computer can also be designed to check for
passwords.

   Data transmitted over communications networks
can be secured by encryption to prevent
eavesdropping.

   Although precautions can be taken to detect an
unauthorized user, it is extremely difficult to
determine if a valid user is performing
unauthorized tasks.  Effective security measures
are a balance of technology and personnel
management.  See NCSC.



security kernel
The part of the operating system that grants access
to users of the computer system.



security levels
See NCSC.



sed
(Stream EDitor)  A UNIX editing command that makes
changes a line at a time and is used to edit large
files that exceed buffer limitations of other
editors.



seed
(1) The starting value used by a random number
generation routine to create random numbers.

(2) (SEED)  (Self-Electro-optic-Effect Device)  An
optical transistor developed by David Miller at
Bell Labs in 1986.



seek
(1) To move the access arm to the requested track
on a disk.

(2) An assembly language instruction that activates
a seek operation on disk.

(3) A high-level programming language command used
to select a record by key field.



seek time
The time it takes to move the read/write head to a
particular track on a disk.



segment
(1) Any partition, reserved area, partial component
or piece of a larger structure.  See overlay.

(2) One of the bars that make up a single character
in an LED or LCD display.

(3) For DOS segment addressing, see paragraph.



segmented address space
Memory addressing in which each byte is referenced
by a segment, or base, number and an offset that is
added to it.  Contrast with flat address space.



SEI
(Software Engineering Institute, Pittsburg, PA)  An
organization associated with Carnegie Mellon
University that is devoted to the advancement of
software engineering.  Its Capability Maturity
Model (CMM) is used to assess an organization's
ability to manage its software development.  The
results are stated as adhering to one of five
levels: Initial, Repeatable, Defined, Managed and
Optimizing.  The more an organization depends on
formal rules to keep projects on schedule and
relies less on individual performers, the higher
the ranking.



Sel
(SELect)  A toggle switch on a printer that takes
the printer alternately between online and offline.



selection sort
A search for specific data starting at the
beginning of a file or list.  It copies each
matching item to a new file so that the selected
items are in the same sequence as the original
data.



selective calling
In communications, the ability of the transmitting
station to indicate which station in the network is
to receive the message.



selector channel
A high-speed computer channel that connects a
peripheral device (disk, tape, etc.) to the
computer's memory.



selector pen
Same as light pen.



Selectric typewriter
Introduced in 1961 by IBM, the first typewriter to
use a golf-ball-like print head that moved across
the paper, rather than moving the paper carriage
across the print mechanism.  It rapidly became one
of the world's most popular typewriters.  IBM has
always excelled in electromechanical devices.



self-booting
Refers to automatically loading the operating
system upon startup.



self-checking digit
See check digit.



self-clocking
Recording of digital data on a magnetic medium such
that the clock pulses are intrinsically part of the
recorded signal.  A separate timer clock is not
required.  Phase encoding is a commonly-used self-
clocking recording technique.



self-documenting code
Programming statements that can be easily
understood by the author or another programmer.
COBOL provides more self-documenting code than does
C, for example.



self-extracting file
One or more compressed files that have been
converted into an executable program which
decompresses its contents when run.



semantic error
In programming, writing a valid programming
structure with invalid logic.



semantic gap
The difference between a data or language structure
and the real world.  For example, in order
processing, a company can be both customer and
supplier.  Since there is no way to model this in a
hierarchical database, the semantic gap is said to
be large.  A network database could handle this
condition, resulting in a smaller semantic gap.



semantics
The study of the meaning of words.  Contrast with
syntax, which governs the structure of a language.



semaphore
(1) A hardware or software flag used to indicate
the status of some activity.

(2) A shared space for interprocess communications
(IPC) controlled by "wake up" and "sleep" commands.
The source process fills a queue and goes to sleep
until the destination process uses the data and
tells the source process to wake up.



semiconductor
A solid state substance that can be electrically
altered.  Certain elements in nature, such as
silicon, perform like semiconductors when
chemically combined with other elements.  A
semiconductor is halfway between a conductor and an
insulator.  When charged with electricity or light,
semiconductors change their state from
nonconductive to conductive or vice versa.

   The most significant semiconductor is the
transistor, which is simply an on/off switch.



semiconductor device
An elementary component, such as a transistor, or a
larger unit of electronic equipment comprised of
chips.



sensor
A device that measures or detects a real world
condition, such as motion, heat or light and
converts the condition into an analog or digital
representation.  An optical sensor detects the
intensity or brightness of light, or the intensity
of red, green and blue for color systems.



sequel
See SQL.



sequence check
Testing a list of items or file of records for
correct ascending or descending sequence based on
the item or key fields in the records.



Sequenced Packet Exchange
See SPX.



Sequent
(Sequent Computer Systems, Inc., Beaverton, OR)
A computer company founded in 1983 by 17 ex-
employees of Intel that specializes in
multiprocessing systems for the client/server
environment.  Sequent pioneered adapting SMP to
UNIX and, according to InfoCorp research for 1992
and 1993, is the worldwide market share leader for
large UNIX systems over $700,000.

   Sequent's SMP machines are all Intel based and
are scalable up to 30 Pentium processors.  Its
Symmetry series runs the UNIX-based DYNIX/ptx
operating system, and the WinServer series runs
Windows NT.



sequential
One after the other in some consecutive order such
as by name or number.



sequential access method
Organizing data in a prescribed ascending or
descending sequence.  Searching sequential data
requires reading and comparing each record,
starting from the top or bottom of file.



sequential scan
Same as non-interlaced.



serial
One after the other.



serial bus
A type of bus that transmits data serially.
Ethernet is an example of a serial bus on a
network.  Serial buses are also expected to become
popular for attaching multiple peripherals to
computers.

   Although both use serial transmission, a serial
bus differs from a serial port.  The serial port
connects the computer to one peripheral device.  A
serial bus allows for the connection of multiple
devices.



serial computer
A single-processor computer that executes one
instruction after the other.  Contrast with
parallel computer.



Serial Infrared
See SIR.



serial interface
A data channel that transfers digital data in a
serial fashion: one bit after the other.  Telephone
lines use serial transmission for digital data,
thus modems are connected to the computer via a
serial port.  So are mice and scanners.  Serial
interfaces have multiple lines, but only one is
used for data.

   For the difference between the serial and
parallel ports, see serial port.  Contrast with
parallel interface.  See RS-232



Serial Line IP
See SLIP.



serial mouse
A mouse that plugs into the serial port on a PC.
Serial mice are the most common type.  Contrast
with bus mouse.



serial number
A unique number assigned by the vendor to each unit
of hardware or software.  See signature.



serial port
A socket on a computer used to connect a modem,
mouse, scanner or other serial interface device to
the computer.  The Macintosh uses the serial port
to attach a printer, whereas the PC uses the
parallel port.  Transferring files between two
personal computers can be accomplished by cabling
the serial ports of both machines together and
using a file transfer program.

   The serial port uses DB-9 and DB-25 connectors.
On the back of most newer PCs is one 9-pin male
connector for serial port #1, named COM1 and
typically used for the mouse, as well as one 25-pin
male connector for serial port #2, named COM2 and
typically used for a modem.

   In a PC, serial port circuits are contained on a
small expansion card that plugs into an expansion
slot.  Typically two serial ports, one parallel
port and one game port are on the card.  These
ports are often also included on an IDE host
adapter card, which takes up only one expansion
slot and provides hard and floppy disk control as
well as I/O.  Contrast with parallel port.  See
serial interface and RS-232.


          Why Serial and Parallel Ports?
The serial port is designed primarily to accomodate
modems, which require a serial connection to the
telephone system.  Data bits are passed one after
the other (serially) over the single line provided
by the telephone wiring.

   On the other hand, local devices such as a
printer are not restricted to single-channel
transmission.  The parallel port, which contains
eight lines for transmitting an entire byte (eight
bits) simultaneously, provides a higher-speed
pathway between the computer and a peripheral
device.

   All other interfaces used in a computer, such as
SCSI and IDE as well as the ISA, EISA and Micro
Channel buses, are also parallel in design.  They
provide 8, 16 or 32 wires for simultaneous transfer
of data bits.



serial printer
A type of printer that prints one character at a
time, in contrast to a line or page at a time.  In
this context, serial has no relationship to a
serial or parallel interface that is used to attach
the printer to the computer.  See printer.



serial transmission
Transmitting data one bit at a time.  Contrast with
parallel transmission.



serialize
To convert a parallel signal made up of one or more
bytes into a serial signal that transmits one bit
after the other.



Series/1
An IBM minicomputer series introduced in 1976.  It
was used primarily as a communications processor
and for data collection in process control.



serif
Short horizontal lines added to the tops and
bottoms of traditional typefaces, such as Times
Roman.  Contrast with sans-serif.



serpentine recording
Tape recording format of parallel tracks in which
the data "snakes" back and forth from the end of
one track to the beginning of the next track.



server
A computer in a network shared by multiple users.
See file server and print server.



server application
(1) An application designed to run in a server.
See client/server.

(2) Any program that is run in the server, whether
designed as a client/server application or not.

(3) See OLE.



Server Message Block
See SMB.



service
Functionality derived from a particular software
program.  For example, network services may refer
to programs that transmit data or provide
conversion of data in a network.  Database services
provides for the storage and retrieval of data in a
database.



service bureau
An organization that provides data processing and
timesharing services.  It may offer a variety of
software packages, batch processing services (data
entry, COM, etc.) as well as custom programming.

   Customers pay for storage of data on the system
and processing time used.  Connection is made to a
service bureau through dial-up terminals, private
lines, or other networks, such as Telenet or
Tymnet.

   Service bureaus also exist that support desktop
publishing and presentations and provide
imagesetting, color proofing, slide creation and
other related services on an hourly or per item
basis.



Service Provider Interface
See SPI.



servo
An electromechanical device that uses feedback to
provide precise starts and stops for such functions
as the motors on a tape drive or the moving of an
access arm on a disk.



session
(1) In communications, the active connection
between a user and a computer or between two
computers.

(2) Using an application program (period between
starting up and quitting).



set theory
The branch of mathematics or logic that is
concerned with sets of objects and rules for their
manipulation.  UNION, INTERSECT and COMPLEMENT are
its three primary operations and they are used in
relational databases as follows.

   Given a file of Americans and a file of Barbers,
UNION would create a file of all Americans and
Barbers.  INTERSECT would create a file of American
Barbers, and COMPLEMENT would create a file of
Barbers who are not Americans, or of Americans who
are not Barbers.  See fuzzy logic.



set-top box
The cable TV box that "sits on top" of the TV set.
A variety of new set-top boxes are expected for
emerging video-on-demand and other interactive
cable services.



setup program
(1) Same as install program.

(2) In a PC, a built-in configuration program that
uses parameters in the CMOS RAM.  See CMOS RAM.



setup string
A group of commands that initialize a device, such
as a printer.  See escape character.



seven dwarfs
IBM's early competitors in the mainframe business:
Burroughs, CDC, GE, Honeywell, NCR, RCA and Univac.



seven-segment display
A common display found on digital watches and
readouts that looks like a series of 8s.  Each
digit or letter is formed by selective illumination
of up to seven separately addressable bars.



sex changer
See gender changer.



SGI
(Silicon Graphics, Inc., Mountain View, CA)  A
manufacturer of very high-end graphics
workstations, founded in 1982 by Jim Clark.  Its
UNIX-based operating system is IRIX.  SGI had been
using MIPS processors for a number of years and
acquired MIPS Computer Systems in 1992.  Its
current line is based on the MIPS R4000 64-bit CPUs
(see MIPS Computer).

   No matter how much better the graphics get on
personal computers, the graphics are always
superior on SGI workstations.  Running a flight
simulator on an SGI machine is considerably more
realistic than on a PC; however, SGI workstations
can cost from 20 to 50 times as much.  They are
naturally used in commercial graphics applications,
where the state of the art is always being pushed.



SGML
(Standard Generalized Markup Language)  An ISO
standard for defining the formatting in a text
document.  It is a comprehensive language that can
even define hypertext links.  In order to decipher
format commands in an SGML document, SGML uses
format definitions in a separately-created DTD
(Document Type Definition) file.  As a result, SGML
is often called a metalanguage, because it
describes another language; in this case, the
actual formatting commands that are embedded in the
text.



sh
(SHell)  A UNIX command that invokes a different
shell.  It can be used like a batch file to execute
a series of commands saved as a shell.



shadow batch
A data collection system that simulates a
transaction processing environment.  Instead of
updating master files (customers, inventory, etc.)
when orders or shipments are initiated, the
transactions are stored in the computer.  When a
user makes a query, the master record from the
previous update cycle is retrieved; but before it's
displayed, it's updated in memory with any
transactions that may affect it.  The up-to-date
master record is then displayed for the user.  At
the end of the day or period, the transactions are
then actually batch processed against the master
file.



shadow mask
A thin screen full of holes that adheres to the
back of a color CRT's viewing glass.  The electron
beam is aimed through the holes onto the phosphor
dots.



shadow RAM
A RAM copy of a PC's ROM BIOS.  In order to improve
performance, the BIOS, which is stored in a ROM
chip, is copied to and executed from RAM.  RAM
chips are accessed faster than ROMs.



shared DASD
A disk system accessed by two or more computers
within a single datacenter.  Disks shared in
personal computer networks are called file servers
or database servers.



shared logic
Using a single computer to provide processing for
two or more terminals.  Contrast with shared
resource. 



shared media LAN
A local area network that shares a common path
(line, cable, etc.) between all nodes.  The
bandwidth of the line is the total transmission
capacity of all transmitting stations at any given
time.  Contrast with a LAN that uses a switching
hub, in which any two stations have the full
bandwidth of the line.



shared resource
Sharing a peripheral device (disk, printer, etc.)
among several users.  For example, a file server
and laser printer in a LAN are shared resources.
Contrast with shared logic.



shareware
Software distributed on a trial basis through
BBS's, online services, mail-order vendors and user
groups.  Shareware is software on the honor system.
If you use it regularly, you're required to
register and pay for it, for which you will receive
technical support and perhaps additional
documentation or the next upgrade.  Paid licenses
are required for commercial distribution.

   There are tens of thousands of shareware
programs, some fantastic, some awful.  Shareware
vendors compile catalogs with hundreds and
thousands of products and sell them by mail or at
shows for a small fee.  That fee is not the
registration fee, but the fee for distributing the
shareware to you.  See freeware, public domain
software, ASP and ZiffNet.

   For a catalog of hand-picked shareware from
noted shareware expert, Alfred Glossbrenner, who
endorses one product from each category, contact:

            GLOSSBRENNER'S CHOICE
            699 River Road
            Yardley, PA 19067
            215/736-1213





shareware awards
Following are the PC Magazine and Computer Gaming
World shareware awards for 1994, reprinted with
permission of Ziff-Davis Interactive, PC Magazine
and Computer Gaming World.

   The following programs can be retrieved from
ZiffNet, the online shareware service of Ziff-Davis
Interactive.  ZiffNet can be accessed via PRODIGY
and other online services.  For information,
contact ZiffNet, 25 First Street, Cambridge, MA
02141, 800/666-0330, 617/252-5000.

   The "GO word" is the user command to enter a
particular forum, or section.  The library is a
further subdivision.


         1994 PC MAGAZINE SHAREWARE AWARDS


 Program           File name      GO word/Library
  Description
 (Win) = Windows program

                  BUSINESS & FINANCE

 Winner
 MONEY SMITH       MSMITH.ZIP  PBSPRO/Bus & Fin
  (Win) Friendly accounting, home & business
 CHECKMATE PLUS      CHKMT1.ZIP  PBSPRO/Bus & Fin
                     CHKMT2.ZIP
  (Win) Full-featured general ledger
 PAINLESS ACCOUNTING PNLSAC.ZIP  PBSPRO/Bus & Fin
  (Win) Professional double entry general ledger
 WPRO93              WPRO93.ZIP  PBSPRO/Bus & Fin
  (Win) Tax preparation
 --------------------------------------------------

                     EDUCATION

 Winner
 HIDE 'N SEEK      HDSK.ZIP    PBSARC/Puzzles
  (Win) Design your own word searches
 ANIMATED CLOCK      ACLOCK.ZIP  PBSHOME/Education
  Interactive time tutorial with sound
 ANIMATED CLOCK &
           DIVISION  AMAD.ZIP    PBSHOME/Education
  Will make 1st-3rd graders love math
 GRADEBOOK           GB4WIN.ZIP  PBSHOME/Education
  (Win) Customizable teacher's helper
 WINFLASH            WINFLS.ZIP  PBSHOME/Education
  (Win) Create flash cards with sound and graphics
 --------------------------------------------------

                      GRAPHICS

 Winner
 PAINT SHOP PRO    PSPRO.ZIP PBSSTUDIO/Media tool
  Sophisticated and flexible image editor
 ENVISON PUBLISHER   ENVIS2.ZIP PBSSTUDIO/MediaTool
  Easy-to-use DTP, great for newsletters
 GRAPHICS WORKSHOP   GWSWIN.ZIP PBSSTUDIO/MediaTool
  Works with bitmaps, all major formats
 IMAGECOMMANDER      IC.ZIP     PBSSTUDIO/Graphics
  (Win) Manage and view graphics in 21 formats
 TOP DRAW            TOPDRW.ZIP PBSSTUDIO/Graphics
 --------------------------------------------------

                    HOME & HOBBY

 Winner
 MOVIES TO GO      MOVIE.ZIP  PBSHOME/Home a/v
  1,000 reviews in searchable library
 CROSS-STITCH
           DESIGNER  CSD.ZIP    PBSHOME/Home hobby
  (Win) It's easy to design your own patterns
 GEOCLOCK            GEOCLK.ZIP PBSUTIL/DesktopTool
  Colored earth map shows time, sun's location
 GROCERY MANAGER     GROMAN.ZIP WINSOURCES/General
  Makes menu planning a snap              shareware
 VIDEO LIBRARIAN     VIDLIB.ZIP PBSHOME/Home a/v
  Database catalogue of video tapes
 --------------------------------------------------

               MULTIMEDIA/PRESENTATION

 Winner
 NEOBOOK PRO       NBOOKP.ZIP PBSAPPS/Windows
  Create and distribute electronic publications
 DEMO WORKSHOP       DWRK.ZIP   PBSSTUDIO/Graphics
  Easy-to-use tool for creating software demos
 NEOSHOW PRO         NSPRO.ZIP  PBSSTUDIO/MediaTool
  Create stand-alone executable files of slideshows
 QUICKSHOW LITE FOR
            WINDOWS  QSHOW.ZIP  PBSSTUDIO/MediaTool
  Create multimedia slideshows
 STORYMAKER+         STORY.ZIP  PBSHOME/Education
  Create multimedia books
 --------------------------------------------------

                  PIMS/CALENDARS

 Winner
 TIME & CHAOS     TCHAOS.ZIP PBSUTILITIES/Windows
  All the functions of commercial PIMs
 ADDRESS MANAGER    ADDMAN.ZIP PBSUTILITIES/Desktop
  Full-featured address book                  tools
 A PROJECT/EVENT
           PLANNER  APLANR.ZIP PBSUTILITIES/Windows
  (Win) Displays charts of plans, events, schedules
 SMART ADDRESS      SMTADR.ZIP PBSUTILITIES/Desktop
  Phone numbers/addresses a click away        tools
 VISUAL CALENDAR
           PLANNER  3DVCP.ZIP  PBSUTILITIES/Desktop
  (Win) Intuitive way to schedule appts.      tools
 --------------------------------------------------

                  UTILITIES/DOS

 Winner
 4DOS             4DOS1.ZIP  PBSUTILITIES/DOS
  DOS shell for power users
 DIRECTORY MAVEN    DMAV.ZIP   PBSUTILITIES/DOS
  Scan all drives, view any directory instantly
 GOHOME SCHEDULER   GOHOME.ZIP PBSUTILITIES/DOS
  Program scheduler, task automater
 INTEGRITY MASTER   I-MAST.ZIP PCCONTACT/Utilities/
  Virus, data integrity protection             Misc
 QUICK MENU         QWKMNU.EXE COMPSHOPPER/
  State-of-the-art menuing           Shareware Shop
 --------------------------------------------------

                UTILITIES/WINDOWS

 Winner
 DRAG & FILE      DRAGFL.ZIP PBSUTILITIES/Windows
  Powerful Windows file manager
 PLUG IN FOR
           WINDOWS  PLUGIN.ZIP PBSUTILITIES/Windows
  Program Manager enhancement
 WINFORMANT        WIN4MNT.ZIP PBSUTILITIES/Windows
  Seven powerful utilities in one
 WINUPD8R          UPD8R.ZIP   TIPS/ASP Shareware
  Synchronizes multiple PCs               utilities
 WOODY'S OFFICE
       POWER PACK  WOPR.ZIP   PBSUTILITIES/Addins/
  Top utilities/macros for Word for Windows   Tools
 --------------------------------------------------


    1994 COMPUTER GAMING WORLD SHAREWARE AWARDS

 Program           File name
  Description
 (Win) = Windows program

    All files are in the Shareware Sizzle Library
                   GO GAMEWORLD


             ACTION ADVENTURE GAMES

 Winner
 DOOM            DOOM.ZIP
  Virtual reality in a brutal 3-D world
 HOCUS POCUS       HOCUS.ZIP
  The quest to wizardry is full of surprises
 PICKLE WARS       PICKLE.ZIP
  Battle the invading pickles (all ages)
 RAPTOR            RAPTOR.ZIP
  You're a mercenary on high-tech missions
 SOLAR WINDS       SOLARW.ZIP
  You're a bounty hunter searching the galaxy
 ----------------------------------------------

                 ARCADE GAMES

 Winner
 EPIC PINBALL    SPIN.ZIP
  Pinball game - looks and feels real
 ANT RUN           ANTRUN.ZIP
  Steer ants through a maze (all ages)
 NIGHT RAID        NTRAID.ZIP
  Go ahead, shoot down smart bombs, paratroopers
 PRARIE DOG HUNT 2:
    JUDGEMENT DAY  PDH2JD.ZIP
  (Win) How many prarie dogs can you shoot?
 --------------------------------------------------

                  CARD GAMES

 Winner
 MVP BRIDGE      MVPBR.ZIP
  For novice or expert, the best shareware bridge
 ULTIMATE GIN      ULTGIN.ZIP
  Fully animated, talking players - Watch Tex deal!
 ULTIMATE BLACKJACK UBJ.ZIP
  Animated casino with up to 4 computer opponents
 --------------------------------------------------

                    PUZZLES

 Winner
 ANIMATED VGA MEMORY   AMEMV.ZIP
  Elegant, addictive game with great graphics
 WORLD SEARCH MANIA      WWS.ZIP
  (Win) Over 75 puzzles to print and solve
 ORDER OUT OF CHAOS      OOOC.ZIP
  (Win) Quick thinking for puzzler's marathon
 --------------------------------------------------

              STRATEGY & WAR GAMES

 Winner
 HEXXAGON              HEXX.ZIP
  Addictive board game - remember to eat and sleep
 BATTTLES IN A DISTANT DESERT  BDD.ZIP
  (Win) The Gulf War
 COLOR CROSS             CLX.ZIP
  Two-player game of strategy
 WORLD EMPIRE            WE2.ZIP
  (Win) Risk-style game - 139 countries to conquer
 --------------------------------------------------


             End of Shareware Awards





sheet-fed scanner
A scanner that allows only paper to be scanned
rather than books or other thick objects.  It moves
the paper across a stationary scan head.  Contrast
with flatbed scanner, hand-held scanner and drum
scanner.



sheet feeder
A mechanical device that feeds stacks of cut forms
(letterheads, legal paper, etc.) into a printer.



shelfware
Products that remain unsold on a dealer's shelf or
unused by the customer.



shell
An outer layer of a program that provides the user
interface, or way of commanding the computer.
Shells are typically add-on programs created for
command-driven operating systems, such as UNIX and
DOS.  It provides a menu-driven or graphical icon-
oriented interface to the system in order to make
it easier to use.  Starting with DOS 4.0, DOS comes
with its own optional shell called DOSshell.



shell out
To temporarily exit an application, go back to the
operating system, perform a function and then
return to the application.



shell script
A file of executable UNIX commands created by a
text editor and made executable with the Chmod
command. It is the UNIX counterpart to a DOS batch
file.



shielded twisted pair
See twisted pair.



shift register
A high-speed circuit that holds some number of bits
for the purpose of shifting them left or right.  It
is used internally within the processor for
multiplication and division, serial/parallel
conversion and various timing considerations.



short
In programming, an integer variable.  In C, a long
is two bytes and can be signed (-32K to +32K) or
unsigned (64K).  Contrast with long.



short card
In a PC, a plug-in printed circuit board that is
half the length of a full-size board.  Contrast
with long card.



short-haul modem
In communications, a device that transmits signals
up to about a mile.  Similar to a line driver that
can transmit up to several miles.



shrink-wrapped software
Refers to store-bought software, implying a
standard platform that is widely supported.



SI
See systems integration, Norton SI and Macintosh.



sideband
In communications, the upper or lower half of a
wave.  Since both sidebands are normally mirror
images of each other, one of the halves can be used
for a second channel to increase the data-carrying
capacity of the line or for diagnostic or control
purposes.



SideBar
A Windows shell from Quarterdeck Office Systems
that streamlines the Windows desktop.  It can
replace Program Manager and File Manager or stay
synchronized with them.  SideBar was originally
developed by Mike McCue of Paper Software.



Sidekick
A PC desktop utility program from Borland.
Introduced in 1984, it was the first popup (TSR)
program for the PC.  It includes a calculator,
WordStar-compatible notepad, appointment calendar,
phone dialer and ASCII table.  Sidekick Plus (1988)
adds more notepad commands, calendar alarms,
scientific and programming calculators, limited
file management and an outliner.



SIDF
(System Independent Data Format)  A tape format
designed as a standard for tape backup systems.  If
widely used, tapes created by one backup software
vendor on one platform would be readable by another
vendor's software on another platform.

   Using a Field Identifier (FID) that identifies
the operating system the data was created on, the
SIDF format can be extended to support future file
systems.  Originating from Novell's Storage
Management Services (SMS) and governed by the SIDF
Association based in Arlington Heights, IL, SIDF is
expected to become an international standard.



Siemens
See SNI.



Sieve of Eratosthenes
A benchmark program used to test the mathematical
speed of a computer.  The program calculates prime
numbers based on Eratosthenes's algorithm.



SIG
(Special Interest Group)  A group of people that
meets and shares information about a particular
topic of interest.  It is usally a part of a larger
group or association.



SIGGRAPH
A special interest group on computer graphics that
is part of the ACM.



sign
A symbol that identifies a positive or negative
number.  In digital code, it is either a separate
character or part of the byte.  In ASCII, the sign
is kept in a separate character typically
transmitted in front of the number it represents
(+ and - is 2B and 2D in hex).

   In EBCDIC, the minus sign can be stored as a
separate byte (hex 60), or, more commonly, as half
a byte (+ and - is C and D in hex), which is stored
in the high-order bits of the least significant
byte.  For packed decimal, it is in the low-order
bits of the least significant byte.



sign on/sign off
Same as log-on/log-off.



signal
Any electrical or light pulse or frequency.



signal converter
A device that changes the electrical or light
characteristics of a signal.



signal processing
See DSP.



signal to noise ratio
The ratio of the amplitude (power, volume) of a
data signal to the amount of noise (interference)
in the line.  Usually measured in decibels, it
measures the clarity or quality of a transmission
channel, audio signal or electronic device.



signaling in/out of band
In communications, signaling "in band" refers to
sending control signals within the same frequency
range as the data signal.  Signaling "out of band"
refers to sending control signals outside of the
frequency range of the data signal.



signature
(1) A unique number built into hardware or software
for identification.

(2) (Signature)  The successor to the XyWrite III
Plus word processor.  See XyWrite III Plus.



significant digits
Those digits in a number that add value to the
number.  For example, in the number 00006508, 6508
are the significant digits.



silica
Same as silicon dioxide.



silica gel
A highly absorbent form of silicon dioxide often
wrapped in small bags and packed with equipment to
absorb moisture during shipping and storage.



silicon
(Si)  The base material used in chips.  Next to
oxygen, it is the most abundant element in nature
and is found in a natural state in rocks and sand.
Its atomic structure and abundance make it an ideal
semiconductor material.  In chip making, it is
mined from rocks and put through a chemical process
at high temperatures to purify it.  To alter its
electrical properties, it is mixed (doped) with
other chemicals in a molten state.



silicon compiler
Software that translates the electronic design of a
chip into the actual layout of the components.



silicon dioxide
(SiO2)  A hard, glassy mineral found in such
materials as rock, quartz, sand and opal.  In MOS
chip fabrication, it is used to create the
insulation layer between the metal gates of the top
layer and the silicon elements below.



silicon disk
A disk drive that is permanently simulated in
memory.  Typically used in laptops for weight
reduction, it requires constant power from a
battery to maintain its contents.



silicon foundry
An organization that makes chips for other
companies that have only design, but not
manufacturing facilities.  It is typically a large
chip maker that uses excess manufacturing capacity
in this manner.



Silicon Graphics
See SGI.



silicon nitride
(Si3N4)  A silicon compound capable of holding a
static electric charge and used as a gate element
on some MOS transistors.



silicon on sapphire
See SOS.



Silicon Valley
The area around San Jose (south of San Francisco)
noted for its large number of high-tech companies.



SIM
(Society for Information Management)  An
organization of MIS professionals founded as the
Society for MIS in 1968.  It is an exchange for
technical information and offers educational and
research programs, competitions and awards to its
members.  Address: 111 East Wacker Dr., Suite 600,
Chicago, IL 60601.



SimCity 2000
A popular educational game for kids and adults for
DOS and Macintosh from Maxis, Orinda, CA.  The
purpose is to create a city that literally expands
itself if the infrastructure is well designed.
After installing a power plant, electric lines,
highways and setting up residential and commercial
zones, the people come and build up the city.  You
can influence the politics, taxation, even
determine how much natural disaster befalls the
citizens.  It's quite amazing!



SIMD
(Single Instruction stream Multiple Data stream) 
A computer architecture that performs one operation
on multiple sets of data, for example, an array
processor.  One computer or processor is used for
the control logic and the remaining processors are
used as slaves, each executing the same
instruction.  Contrast with MIMD.



SIMM
(Single In-line Memory Module)  A narrow printed
circuit board from three to four inches long that
holds some number of memory chips.  It plugs into a
SIMM socket on the circuit board.

   The first SIMM format that became popular on
personal computer motherboards uses a 30-pin
connector.  A larger format that uses 72-pins
contains from one to 64 megabytes of RAM.

   PCs use either nine-bit memory (eight bits and a
parity bit) or eight-bit memory without parity. 
Macintoshes use eight-bit memory without parity.


                30-pin SIMMs
 Configuration
          Capacity    Chip layout
    1x3     1MB   Two 4Mb chips, one 1Mb chip
    1x9     1MB   Nine 1Mb chips
    2x9     2MB   Nine 2Mb chips
    4x9     4MB   Nine 4Mb chips
   16x9    16MB   Nine 16Mb chips

    1x2     1MB   Two 4Mb chips (no parity)
    1x8     1MB   Eight 1Mb chips (no parity)
    2x8     2MB   Eight 2Mb chips (no parity)
    4x8     4MB   Eight 4Mb chips (no parity)
   16x8    16MB   Eight 8Mb chips (no parity)

               72-pin SIMMs
 Configuration
          Capacity    Chip layout
  256x36    1MB   The number of chips on a 72-pin
  512x36    2MB   SIMM is not expressed in its
    1x36    4MB   designation.  For example, 8x36
    2x36    8MB   means only that 8 million 36-bit
    4x36   16MB   words are available to the
    8x36   32MB   motherboard.
   16x36   64MB
    1x32    4MB   (no parity)
    2x32    8MB   (no parity)
    4x32   16MB   (no parity)
    8x32   32MB   (no parity)
   16x32   64MB   (no parity)


               The Speed of the Chip
A number, typically from 50 to 80, following the
above designation is chip speed; for example,
1x9-60 means 60 nanosecond 1MB SIMMs.


          Multiple SIMMs May Be Required
On PCs, SIMMs are installed in multiples of two on
286s and 386SXs, and multiples of four on 386DXs
and up.  On 486s and up, the number that must be
installed at one time depends on the motherboard.





Simple Mail Interface
See SMI.



Simple Mail Transfer Protocol
See SMTP.



Simple Network Managment Protocol
See SNMP.



simplex
One way transmission.  Contrast with half-duplex
and full-duplex.



SIMSCRIPT
A programming language used for discrete
simulations.



simulation
(1) The mathematical representation of the
interaction of real-world objects.  See scientific
application.

(2) The execution of a machine language program
designed to run in a foreign computer. 



sine
In a right triangle, the ratio of the side opposite
an acute angle (less than 90 degrees) and the
hypotenuse.  The cosine is the ratio between the
adjacent side and the hypotenuse.  These angular
functions are used to compute circular movements.



sine wave
A uniform wave that is generated by a single
frequency.



single board computer
A printed circuit board that contains a complete
computer, including processor, memory, I/O and
clock.



single density disk
The first-generation floppy disk.



Single Document Interface
See SDI.



single-ended configuration
Electrical signal paths that use a common ground,
which are more susceptible to noise than
differential configuration.



single in-line memory module
See SIMM.



single in-line package
See SIP.



single large expensive disk
See SLED.



single-mode fiber
An optical fiber with a core diameter of less than
10 microns, used for high-speed transmission and
long distances.  It provides greater bandwidth than
multimode fiber, but its smaller core makes it more
difficult to couple the light source.  Contrast
with multimode fiber.



single precision
The use of one computer word to hold a numeric
value for calculation.  Contrast with double
precision.



single session
See Photo CD.



single sided disk
A floppy disk that stores data on only one side.



single-system image
An operational view of multiple networks,
distributed databases or multiple computer systems
as if they were one system.



single threading
Processing one transaction to completion before
starting the next.



sink
A device or place that accepts something.  See heat
sink and data sink.



SIP
(1) (Single In-line Package)  A type of chip module
that is similar to a SIMM, but uses pins rather
than edge connectors.  SIPs are sometimes called
SIPPs (Single In-Line Pin Package).

(2) (SMDS Interface Protocol)  The protocol used to
support SMDS service.  It is composed of the Level
3 Protocol Data Unit (L3_PDU), which contains
source and destination addresses and an information
field up to 9188 bytes long.  See SMDS.

(3) (Software Integration Platform)  A
specification that provides a common format and
interface for storing and retrieving geographic
data for the petroleum industry.



SIR
(Serial InfraRed)  An infrared (IR) technology from
HP that allows wireless data transmission between
two devices up to one meter apart.  Both devices
must be lined up to each other.  Future
enhancements will allow greater distances and wider
angles.  It is expected that SIR ports will be come
standard on laptops by 1995.



SISD
(Single Instruction stream Single Data stream) 
The architecture of a serial computer.  Contrast
with SIMD and MIMD.



site license
A license to use software within a facility.  It
provides authorization to make copies and
distribute them within a specific jurisdiction.



SIXEL
A graphics language from Digital that supersedes
ReGIS.  ReGIS to SIXEL conversion programs are
available.



skew
(1) The misalignment of a document or punched card
in the feed tray or hopper that prohibits it from
being scanned or read properly.

(2) In facsimile, the difference in rectangularity
between the received and transmitted page.

(3) In communications, a change of timing or phases
in a transmission signal.

(4) See cylinder skew and head skew.



sky wave
A radio signal transmitted into the sky and
reflected back down to earth from the ionosphere.



SkyTel
(SkyTel Corporation, Washington, DC)  A paging
service provider.  In 1987, it was the first to
provide nationwide paging.  The SkyPager service
transmits a 12-digit number.  SkyTalk beeps the
pager, and the user dials in to listen to voice
messages.  SkyWord transmits text to the
recipient's paging device.



SL
See 386SL and 486SL.



SL Enhanced
The designation from Intel for its family of power-
saving "SL" CPU chips.



slang
See Lessons slang.



slave
A computer or peripheral device controlled by
another computer.  For example, a terminal or
printer in a remote location that only receives
data is a slave.  When two personal computers are
hooked up via their serial or parallel ports for
file exchange, the file transfer program may make
one computer the master and the other the slave.



slave tube
A display monitor connected to another monitor in
order to provide an additional viewing station.



SLC
See 386SLC.



SLED
(Single Large Expensive Disk)  The traditional disk
drive.  Contrast with RAID.



sleep
(1) In programming, an inactive state due to an
endless loop or programmed delay.  A sleep
statement in a programming language creates a delay
for some specified amount of time.

(2) The inactive status of a terminal, device or
program that is awakened by sending a code to it.



slew rate
(1) How fast paper moves through a printer (ips).

(2) The speed of changing voltage.



sliding window
(1) A communications protocol that transmits
multiple packets before acknowledgement.  Both ends
keep track of packets sent and acknowledged (left
of window), those which have been sent and not
acknowledged (in window) and those not yet sent
(right of window).

(2) A view of memory that can be instantly shifted
to another location.



SLIP
(Serial Line IP)  A TCP/IP protocol that allows IP
packets to be transmitted over a serial link, such
as a dial-up or private telephone line.  A SLIP or
PPP connection on the Internet allows users to dial
into the Internet, yet have their own Internet
location/domain name.  Their Internet addresses
would look the same as direct connections, such as
the aol.com and delphi.com addresses for the
America Online and DELPHI online services.  See
PPP.



slipstream
To fix a bug or add enhancements to software
without identifying such inclusions by creating a
new version number.



slot
(1) A receptacle for additional printed circuit
boards.

(2) A receptacle for inserting and removing a disk
or tape cartridge.

(3) In communications, a narrow band of
frequencies.  See time slot.

(4) May refer to reserved space for temporary or
permanent storage of instructions, data or codes.



slot mask
The Sony Trinitron counterpart to the shadow mask.
It uses vertical rectangular slots instead of
holes.



slow scan TV
The transmission of still video frames over
telephone lines.  Not realtime transmission, it
takes several seconds to transmit one frame.  Also
called electronic still photography (ESP).



slug
A metal bar containing the carved image of a letter
or digit that is used in a printing mechanism.



SMA
(1) (Software Maintenance Association)  A non-
profit professional organization founded in 1985
and dedicated to enhance understanding of software
maintenance and to advance those concerned with it.
Active chapters are in major cities worldwide.
Annual conference is held in the spring.  Address:
Ms. Robin Gross, Box 12004, Vallejo, CA 94590,
707/643-4423.

(2) (Systems Management Architecture)  An IBM
network management repository.

(3) (Spectrum Manufacturers Association)  A DBMS
standard for application compatibility.



SMA connector
A fiber-optic cable connector that uses a plug
which is screwed into a threaded socket.  It was
the first connector for optical fibers to be
standardized.  See ST connector and SC connector.



small office/home office
See SOHO.



small outline gullwing
Same as SOIC.



small outline IC
See SOIC.



small outline J lead
See SOJ.



Smalltalk
An operating system and object-oriented programming
language that was developed at Xerox Corporation's
Palo Alto Research Center.  As an integrated
environment, it eliminates the distinction between
programming language and operating system.  It also
allows the programmer to customize the user
interface and behavior of the system.

   Smalltalk was the first object-oriented
programming language and was used on Xerox's Alto
computer, which was designed for it.  It was
originally used to create prototypes of simpler
programming languages and the graphical interfaces
that are so popular today.



Smalltalk V
A version of Smalltalk for PCs from Digitalk, Inc.,
Los Angeles.  Versions for DOS, OS/2, Windows and
the Mac are also available.



smart cable
A cable with a built-in microprocessor used to
connect two devices.  It analyzes incoming signals
and converts them from one protocol to another.



smart card
A credit card with a built-in microprocessor and
memory used for identification or financial
transactions.  When inserted into a reader, it
transfers data to and from a central computer.  It
is more secure than a magnetic stripe card and can
be programmed to self-destruct if the wrong
password is entered too many times.  As a financial
transaction card, it can store transactions and
maintain a bank balance.



smart hub
See intelligent hub.



smart install program
An install program that configures itself
automatically based on the hardware environment.



smart terminal
A video terminal with built-in display
characteristics (blinking, reverse video,
underlines, etc.).  It may also contain a
communications protocol.  The term is often used
synonymously with intelligent terminal.  See
intelligent terminal and dumb terminal.



Smartcom
A family of communications programs for PCs and
Macs from Hayes Microcomputer Products, Inc.,
Atlanta, GA.  Versions emulate a several terminals
and support a variety of protocols, including the
Hayes V-series.  Smartcom EZ is for the novice.



Smartdrive
A disk cache program that comes with DOS and
Windows.  In DOS 4.0 and Windows 3.0, the name of
the driver file is SMARTDRV.SYS.  Starting with DOS
5 and Windows 3.1, the name of the driver is
SMARTDRV.EXE.



SmartKey
A PC keyboard macro processor from No Brainer
Software, Midvale, UT.  It was one of the first
macro processors that let users eliminate
repetitive typing by creating a macro for an
occurrence of text or a series of commands.



SmartSuite
A suite of Windows applications from Lotus that
includes the 1-2-3 spreadsheet, Ami Pro word
processor, Freelance Graphics, Approach database,
Organizer PIM and Adobe Type Manager.  Also
included is a common toolbar for launching all the
applications and selecting predefined macros that
provide tighter integration between the
applications.



SmartWare
An integrated software package for PCs and various
UNIX-based systems from Informix Software, Inc.,
Menlo Park, CA, that includes a programming
language.



SMB
(Server Message Block)  A message format derived
from the Microsoft/3Com file sharing protocol.  It
provides services at the application layer (layer 7
of the OSI model) and is used with NetBIOS and
NetBEUI protocols in networks such as LAN Manager,
LAN Server and Windows NT.  It is used to transfer
file requests (open, close, read, write, etc.)
between clients and servers as well as within the
server for internal operations.  For network
transfer, SMBs are carried within the NetBIOS
network control block (NCB) packet.



SMD
(1) (Storage Module Device)  A high-performance
hard disk interface used with minis and mainframes
that transfers data in the 1-4 MBytes/sec range
(SMD-E provides highest rate).  See hard disk.

(2) (Surface Mount Device)  A surface mounted chip.



SMDS
(Switched Multimegabit Data Service)  A high-speed,
switched data communications service offered by the
local telephone companies for interconnecting LANs
in different geographic locations.  It was
introduced in 1992, and generally available
nationwide by 1995.

   Connection to an SMDS service can be made from a
variety of devices, including bridges, routers,
CSU/DSUs as well as via frame relay and ATM
networks.  SMDS is a service that can employ
various networking technologies.  Early
implementations use the IEEE 802.6 DQDB MAN
technology at rates up to 45 Mbps.  ATM is also
expected to be used.

   Data is framed for transmission using the SMDS
Interface Protocol (SIP), which packages data as
Level 3 Protocol Data Units (L3_PDU).  The L3_PDU
contains source and destination addresses and a
data field that holds up to 9188 bytes.



SMF
(1) (Standard Messaging Format)  An electronic mail
format for Novell's MHS messaging system.  The
application puts the data into this format in order
to send an e-mail message.  NGM (NetWare Global
Messaging) is based on SMF-71, which supports long
addresses and synchronized directories.

(2) (Standard MIDI file)  See MIDI file.

(3) See single-mode fiber.



SMI
(1) (Simple Mail Interface)  A subset of functions
within the VIM messaging protocol used by
applications to send e-mail and attachments.
Future versions of VIM will use the CMC API rather
than SMI.

(2) (Structure of Management Information)  A
definition for creating MIBs in the SNMP protocol.

(3) (System Management Interrupt)  A hardware
interrupt in Intel SL Enhanced 486 and Pentium CPUs
used for power management.  This interrupt is also
used for virus checking.



SMM
(System Management Mode)  An energy conservation
mode built into Intel SL Enhanced 486 and Pentium
CPUs.  During inactive periods, SMM initiates a
sleep mode that turns off peripherals or the entire
system.  It retains the computer's status in a
protected area of memory called the SMRAM (System
Management RAM).



smoke test
A test of new or repaired equipment by turning it
on.  If there's smoke, it doesn't work!



smoothed data
Statistical data that has been averaged or
otherwise manipulated so that the curves on its
graph are smooth and free of irregularities.



smoothing circuit
An electronic filtering circuit in a DC power
supply that removes the ripples from AC power.



SMP
(Symmetric MultiProcessing)  A multiprocessing
computer system in which multiple CPUs, residing in
one cabinet, share the same memory.  SMP systems
provide scalability.  As business increases,
additional CPUs can be added to absorb the
increased transaction volume.

   SMP systems range from two to as many as 32 or
more processors.  However, if one CPU fails, the
entire SMP system, or node, is down.  Clusters of
two or more SMP nodes are used to provide high
availability, or fault resilience, in case of
failure.  The other nodes continue to operate in
the event that one fails.

   A single CPU generally boots the system and
loads the SMP operating system, which brings the
other CPUs online.  There is only one instance of
the operating system and one instance of the
application in memory.  The operating system uses
the CPUs as a pool of processing resources, all
executing simultaneously, either processing data or
in an idle loop waiting to do something.  The
operating system's multithreading capability allows
it to control multiple CPUs.

   Clusters of SMP nodes are also used to increase
processing capability.  However, when SMP is used
in this manner, it functions as a massively
parallel processor (MPP).  MPP systems use
different programming paradigms, because there are
not only multiple CPUs, but multiple memories each
with a copy of the operating system and
application.  It requires a problem to be split
into smaller pieces that can be solved
simultaneously.

   For example, in the commercial world, a parallel
data query (PDQ) breaks down a query into multiple
searches so that several parts of the database can
be searched simultaneously.  The Oracle Parallel
Server software was the first DBMS to allow
multiple instances of itself, each in a different
CPU, to access a common database.

   Sequent, Pyramid and Encore pioneered SMP on
UNIX platforms.  SMP servers are also available
from IBM, HP, AT&T GIS, Unisys and others.  Many
versions of UNIX as well as proprietary operating
systems, such as Windows NT, OS/2 and NetWare, have
been designed for or are being revamped for SMP.
SMP usage is expected to grow rapidly.



SMPTE
(Society for Motion Picture and TV Engineers)  An
organization that prepares standards and
documentation for TV production.  SMPTE time code
records hours, minutes, seconds and frames on audio
or videotape for synchronization purposes.
Address: 595 W. Hartsdale Ave., White Plains, NY
10607, 914/761-1100.



SMR
(Specialized Mobile Radio)  Communications services
used by taxicabs, trucks and other mobile
businesses.  Throughout the U.S., approximately
3,000 independent operators are licensed by the FCC
to provide this service.



SMRAM
See SMM.



SMS
(1) (Storage Management System)  Software used to
routinely back up and archive files.  See SMS
definition below and HSM.

(2) (Storage Management Services)  Software from
Novell that allows data to be stored and retrieved
on NetWare servers independent of the file system
the data is maintained in (DOS, OS/2, Mac, etc.).
It is used to back up data from heterogeneous
clients on the network.  Various third-party backup
products are SMS compliant.  See SIDF.

(3) (Systems Management Server)  Systems management
software from Microsoft that runs on Windows NT
Server 3.5.  It requires a Microsoft SQL Server
database and is used to distribute software,
monitor and analyze network usage and perform
various network administration tasks.  It is
expected by late 1994.



SMT
(1) See surface mount.

(2) (Station ManagemenT)  An FDDI network
management protocol that provides direct
management.  Only one node requires the software.



SMTP
(Simple Mail Transfer Protocol)  A messaging
protocol used in TCP/IP networks.



SNA
(Systems Network Architecture)  IBM's mainframe
network standards introduced in 1974.  Originally a
centralized architecture with a host computer
controlling many terminals, enhancements, such as
APPN and APPC (LU 6.2), have adapted SNA to today's
peer-to-peer communications and distributed
computing environment.  Following are some of SNA's
basic concepts.

               Nodes and Data Links
In SNA, nodes are end points or junctions, and data
links are the pathways between them.  Nodes are
defined as Type 5 (hosts), Type 4 (communications
controllers) and Type 2 (peripheral; terminals, PCs
and midrange computers).

   Type 2.0 nodes can communicate only with the
host, and Type 2.1 nodes can communicate with other
2.1 nodes (peer-to-peer) without going to the host.

   Data links include high-speed local channels,
the SDLC data link protocol and Token Ring.


                SSCPs, PUs and LUs
The heart of a mainframe-based SNA network is the
SSCP (System Services Control Point) software that
resides in the host.  It manages all resources in
its domain.

   Within all nodes of an SNA network, except for
Type 2.1, there is PU (Physical Unit) software that
manages node resources, such as data links, and
controls the transmission of network management
information.  In Node Type 2.1, Control Point
software performs these functions.

   In order to communicate user data, a session
path is created between two end points, or LUs
(Logical Units).  When a session takes place, an
LU-LU session is established between an LU in the
host (CICS, TSO, user appliction, etc.)  and an LU
in the terminal controller or PC.

   An LU 6.2 session provides peer-to-peer
communication and lets either side initiate the
session.


                   VTAM and NCP
VTAM (Virtual Telecommunications Access Method)
resides in the host and contains the SSCP, the PU
for the host, and establishes the LU sessions
within the host.

   NCP (Network Control Program) resides in the
communications controller (front end processor) and
manages the routing and data link protocols, such
as SDLC and Token Ring.


                    SNA Layers
SNA is implemented in functional layers with each
layer passing control to the next layer.  This
layering is called a protocol stack.


      User
        
  Ŀ
  Transaction  Program to program communications
 7  Services   for e-mail, file sharing, etc.
               (DIA, SNA/DS, DDM, etc.)
  Ĵ
 6Presentation Formats data for terminal.
    Services   (3270 screens, APPC, etc.)
              
  Ĵ
 5 Data flow   Assigns sequence nos., controls
    Control    direction, groups related data.
               Provides end user acknowledgment.
  Ĵ
  Transmission Logical end-to-end.  Checks packet
 4  Control    sequence, handles encryption and
               paces transmission.
  Ĵ
     Path                      Path control Ŀ
 3  Control     Physical end-to-end (routing).  
                                                
  Ĵ                                  
   Data link    Error detection and             
 2  Control     correction. (Local channel,     
                SDLC, Token Ring, X.25, etc.)   
  Ĵ                                  
 1  Physical    Wires, signals.                 
    Control     (RS232, 802.5, etc.)          
  
        
        
  Ŀ
 1  Physical  
        
        
   Back up the
   hierarchy to
   the other user.


                    SNA vs OSI
SNA had major influence on the international OSI
model; however, OSI does not implement every layer
exactly the same.


               SNA              OSI
         Ŀ  Ŀ
          Transaction    Application 
         Ĵ  Ĵ
         Presentation   Presentation 
         Ĵ  Ĵ
           Data flow       Session   
         Ĵ  Ĵ
         Transmission     Transport  
         Ĵ  Ĵ
         Path control      Network   
         Ĵ  Ĵ
          Data link       Data link  
         Ĵ  Ĵ
           Physical       Physical   
           





SNA-A
See SNA Over Async.



SNA Over Async
Software that allows SNA applications to hook into
an SNA network via modem.  With the SNA Over Async
(SNA-A) program in a remote computer and the
connecting network node, applications that normally
run on a LAN or through 3270 emulation can connect
over a telephone line without modification.



SNADS
(SNA Distribution Services)  An IBM messaging
protocol used by IBM office automation products
such as DISOSS and AS/400 Office.  Various
messaging gateways and messaging switches support
SNADS.



snap to
A feature in a drawing program that moves a text or
graphic element to the closest grid line.



snapshot
The saved current state of memory including the
contents of all memory bytes, hardware registers
and status indicators.  It is periodically taken in
order to restore the system in the event of
failure.



snapshot dump
A memory dump of selected portions of memory.



snapshot program
A trace program that provides selected dumps of
memory when specific instructions are executed or
when certain conditions are met.



snd
(SouND resource)  A Macintosh resource fork that
contains sound information, including compression
ratios if used and sampling rate.



sneakernet
Carrying floppy disks from one machine to another
to exchange information, when you don't have a
network.



SNI
(1) (Subscriber Network Interface)  The point of
interface between the customer's equipment (CPE)
and a communications service from a common carrier.

(2) (SNA Network Interconnection)  Using a
mainframe as a gateway between two independent SNA
networks.

(3) (Siemens Nixdorf Information Systems - Siemens
Nixdorf Informationssysteme AG)  The new name of
this German computer company after the 1990 merger
of Nixdorf AG and Siemens AG.  AG is the German
acronymn for corporation (AktienGesellshaft).



sniffer
Software and/or hardware that analyzes traffic and
detects bottlenecks and problems in a network.



SNMP
(Simple Network Management Protocol)  A widely-used
network monitoring and control protocol.  Data is
passed from SNMP agents, which are hardware and/or
software processes reporting activity in each
network device (hub, router, bridge, etc.) to the
workstation console used to oversee the network.
The agents return information contained in a MIB
(Management Information Base), which is a data
structure that defines what is obtainable from the
device and what can be controlled (turned off, on,
etc.).

   SNMP 2 provides enhancements including security
and an RMON (Remote Monitoring MIB), which provides
continuous feedback without having to be queried by
the SNMP console.  Originating in the UNIX
community, SNMP has spread to VMS, DOS and other
environments.



SNOBOL
(StriNg Oriented symBOlic Language)  One of the
first list processing languages (Bell Labs; early
1960s).  It was used for text processing and
compiler development.



snow
The flickering snow-like spots on a video screen
caused by display electronics that are too slow to
respond to changing data.



SNR
See signal to noise ratio.



Society for Information Management
See SIM.



Society for Motion Picture and TV Engineers
See SMPTE.



socket
(1) A receptacle which receives a plug.

(2) See UNIX socket.



socket services
Low-level software that manages a PCMCIA
controller.  See PCMCIA.



soft
Flexible and changeable.  Software can be
reprogrammed for different results.  The computer's
soft nature is its greatest virtue; however, the
reason it takes so long to get new systems
developed has little to do with the concept.  It is
based on how systems are developed (file systems vs
database management), the programming languages
used (assembly vs high-level), combined with the
skill level of the technical staff, compounded by
the organization's bureaucracy.



soft boot
Same as warm boot.



soft copy
Refers to data displayed on a video screen.
Contrast with hard copy.



soft error
A recoverable error, such as a garbled message that
can be retransmitted.  Contrast with hard error.



soft font
A set of characters for a particular typeface that
is stored on the computer's hard disk, or in some
cases the printer's hard disk, and downloaded to
the printer before printing.  Contrast with
internal font and font cartridge.



soft hyphen
A hyphen that prints if it winds up at the end of
the line, but does not print otherwise.  Contrast
with hard hyphen.  See discretionary hyphen.



soft key
A keyboard key that is simulated by an icon on
screen.



soft patch
A quick fix to machine language currently in memory
that only lasts for the current session.



soft return
A code inserted by the software into a text
document to mark the end of the line.  When the
document is printed, the soft return is converted
into the end-of-line code required by the printer.
Soft returns are determined by the right margin and
change when the margins are changed.

   In graphics-based environments, such as in the
Macintosh, soft returns are not used as the text
must be free to change within movable windows.

   With PCs, soft return codes differ; for example,
WordPerfect uses a return (ASCII 13) and WordStar
uses a line feed (ASCII 10).

   Contrast with hard return.



soft sectored
A common method of identifying sectors on a disk by
initially recording sector information on every
track with a format program.  Contrast with hard
sectored.



Soft-Switch
E-mail switching software and hardware from Soft-
Switch, Inc., Wayne, PA, that provides an e-mail
backbone for organizations with diverse e-mail
systems.  It directly supports X.400, SNADS and
SMTP and provides gateways to other e-mail systems.
Soft-Switch Central is software for IBM MVS and VM
mainframes, and its EMX 88000-based e-mail server
connects to Token Ring, Ethernet, X.25 and SDLC.



SoftKey
(SoftKey International, Inc., Cambridge, MA)  A
software company that was originally founded in
1984 in Toronto.  In 1994, it came to the U.S. with
a merger of Spinnaker Software and Wordstar
International.




SoftPC
A family of PC emulation programs from Insignia
Solutions, Inc., Andover, MA, that allow DOS and
Windows programs to run on Macintosh, UNIX
workstations and the PowerPC.



Softstrip
An optical scanner that read a unique, printed,
encoded pattern that contained 50 to 600 bytes of
data per inch.



SoftSwitch
See Soft-Switch.



software
Instructions for the computer.  A series of
instructions that performs a particular task is
called a program.

   The two major categories are system software and
application software.  System software is made up
of control programs, including the operating
system, communications software and database
manager.

   Application software is any program that
processes data for the user (inventory, payroll,
spreadsheet, word processor, etc.).

   A common misconception is that software is also
data.  It is not.  Software tells the hardware how
to process the data.

        "Software is "run."

            Data is "processed."



software architecture
The design of application or system software that
incorporates protocols and interfaces for
interacting with other programs and for future
flexibility and expandability.  A self-contained,
stand-alone program would have program logic, but
not a software architecture.



software bug
A problem that causes a program to abend (crash) or
produce invalid output.  Problems that cause a
program to abend are invalid data, such as trying
to divide by zero, or invalid instructions, which
are caused by bad logic that misdirects the
computer to the wrong place in the program.

   A program with erroneous logic may produce bad
output without crashing, which is the reason
extensive testing is required for new programs.
For example, if the program is supposed to add an
amount, but instead, it subtracts it, bad output
results.  As long as the program performs valid
machine instructions on data it knows how to deal
with, the computer will run.



Software Carousel
A DOS task switching program from SoftLogic
Solutions, Inc., Manchester, NH, that allows the
user to have up to a dozen applications open at the
same time and switch back and forth between them.



software codec
A compression/decompression routine that is
implemented in software only without requiring
specialized DSP hardware.  See codec.



software configuration management
See SCM.



software developer's kit
See SDK.



software engineering
The design, development and documentation of
software.  See CASE, systems analysis & design,
programming, object-oriented programming, software
metrics and Systemantics.



Software Engineering Institute
See SEI.



software failure
The inability of a program to continue processing
due to erroneous logic.  Same as crash, bomb and
abend.



software house
An organization that develops customized software
for a customer.  Contrast with software publisher,
which develops and markets software packages.



software IC
An object-oriented programming class packaged for
sale.  The term was coined by The Stepstone
Corporation.



software interface
Same as API.



software interrupt
An interrupt caused by an instruction in the
program.  See interrupt.



Software Maintenance Association
See SMA.



software metrics
Software measurements.  Using numerical ratings to
measure the complexity and reliability of source
code, the length and quality of the development
process and the performance of the application when
completed.



software package
An application program developed for sale to the
general public.



software program
A computer program (computer application).  All
computer programs are software.  Usage of the two
words together is redundant, but common.



software programmer
Same as systems programmer.



software protection
See copy protection.



software publisher
An organization that develops and markets software.
It does market research, production and
distribution of software.  It may develop its own
software, contract for outside development or
obtain software that has already been written.



Software Publishers Association
See SPA.



software stack
A stack that is implemented in memory.  See stack.



software tool
A program used to develop other software.  Any
program or utility that helps a programmer design,
code, compile or debug sofware can be called a
tool.



software vendors
Following is Software Magazine's ranking of the
Top 100 Independent Software Vendors for calendar
1993.  The total revenues of 19.5 billion dollars
from all the companies in the list come from
packaged software sales worldwide.  Consulting,
custom services and programming revenues are
excluded.

   See also hardware vendors and vendors.


        TOP 100 INDEPENDENT SOFTWARE VENDORS
   Ranked by Software Package Revenues Worldwide

    Reprinted with the permission of Software
    Magazine, July 1994, Sentry Publishing
    Company, Inc., 1900 West Park Drive,
    Westborough, MA 01581.


               (* = privately held)


        Total number employeesĿ  1993 Packaged
    COMPANY NAME                 Software revenue
    HQ city (date founded)       ($ millions)
                               
  1 MICROSOFT CORP.
    Redmond, WA (1975)       14000   3780
  2 COMPUTER ASSOCIATES INT'L., INC.
    Islandia, NY (1976)       7200   2055
  3 ORACLE CORP.
    Redwood Shores, CA(1977) 10661   1315
  4 NOVELL, INC.
    Provo, UT (1983)          4429   1036

  5 LOTUS DEVELOPMENT CORP.
    Cambridge, MA (1982)      4909    981
  6 WORDPERFECT CORP.*
    Orem, UT (1979)           5500    672
  7 BORLAND INT'L. INC.
    Scotts Valley, CA (1983)  2033    460
  8 SAS INSTITUTE, INC.*
    Cary, NC (1976)           2897    420

  9 LEGENT CORP.
    Vienna, VA (1989)         2400    417
 10 SAP AG (SAP AMERICA)
    Lester, PA (1972)         3600    414
 11 SYBASE, INC.
    Emeryville, CA (1984)     2537    361
 12 DUN & BRADSTREET SOFTWARE
    Atlanta, GA (1990)        2500    352

 13 SOFTWARE AG*
    Reston, VA (1969)         4500    350
 14 INFORMIX SOFTWARE, INC.
    Menlo Park, CA (1980)     1718    284
 15 BMC SOFTWARE, INC.
    Sugar Land, TX (1980)      965    274
 16 SYMANTEC CORP.
    Cupertino, CA (1982)      1193    262

 17 STERLING SOFTWARE, INC.
    Dallas, TX (1981)         2850    258
 18 AMERICAN MANAGEMENT SYSTEMS
    Arlington, VA (1970)      3780    238
 19 CANDLE CORP.*
    Santa Monica, CA (1977)    985    209
 20 COMPUWARE CORP.
    Farmington Hills, MI('73) 2076    207

 21 ALDUS CORP.
    Seattle, WA 98104 (1984)  1100    207
 22 THE ASK GROUP
    Mountain View, CA (1972)  2300    203
 23 INFORMATION BUILDERS INC.*
    New York, NY (1975)       1800    200
 24 SYSTEM SOFTWARE ASSOCIATES INC.
    Chicago, IL (1981)        1500    180

 25 CLARIS CORP.
    Santa Clara, CA (1987)     650    161
 26 THE SANTA CRUZ OPERATION*
    Santa Cruz, CA (1979)     1100    157
 27 CINCOM SYSTEMS, INC.*
    Cincinnati, OH (1968)     1389    156
 28 J.D. EDWARDS & CO.*
    Denver, CO (1977)         1380    131

 29 ATTACHMATE CORP.*
    Bellevue, WA (1984)        993    123
 30 MICRO FOCUS INC.
    Palo Alto, CA (1976)       698    122
 31 KNOWLEDGEWARE, INC.
    Atlanta, GA (1979)         875    120
 32 BOOLE & BABBAGE, INC.
    Sunnyvale, CA (1967)       648    115

               (* = privately held)

 33 MARCAM CORP.
    Newton, MA (1980)         1200    109
 34 COGNOS, INC.
    Ottawa, Ontario (1969)    1000    103
 35 PROGRESS SOFTWARE CORP.
    Bedford, MA (1981)         850     99
 36 COMSHARE, INC.
    Ann Arbor, MI (1966)       776     96

 37 BANYAN SYSTEMS, INC.
    Westborough, MA (1983)     692     94
 38 INTERLEAF, INC.
    Waltham, MA (1981)         884     93
 39 ANDERSEN CONSULTING*
    Chicago, IL (1954)       29296     92
 40 SOFTWARE PUBLISHING CORP.
    Mountain View, CA (1980)   466     90

 41 IRI SOFTWARE
    Waltham, MA (1982)         850     88
 42 FILENET CORP.
    Costa Mesa, CA (1981)      885     82
 43 INTERSOLV, INC.
    Rockville, MD (1991)       480     81
 44 SOFTWARE ENGINEERING OF AMERICA, INC.*
    Lake Success, NY (1982)    300     81

 45 UNIFACE CORP.*
    Alameda, CA 94501          500     78
 46 CHEYENNE SOFTWARE, INC.
    Roslyn Heights, NY (1983)  320     73
 47 WALKER RICHER & QUINN, INC.*
    Seattle, WA (1981)         299     66
 48 WALL DATA, INC.
    Redmond, WA (1982)         388     65

 49 SOFTLAB, INC.
    Atlanta, GA (1971)         800     63
 50 BAAN INTERNATIONAL, INC.*
    Grand Rapids, MI (1978)    820     62
 51 PLATINUM TECHNOLOGY, INC.
    Oakbrook Terrace, IL ('87) 333     58
 52 GUPTA CORP.
    Menlo Park, CA (1984)      337     56

 53 FTP SOFTWARE INC.
    North Andover, MA (1986)   400     56
 54 AMERICAN SOFTWARE
    Atlanta, GA (1970)         840     55
 55 LUCAS MANAGEMENT SYSTEMS
    Fairfax, VA (1977)         550     53
 56 IMRS
    Stamford, CT (1981)        461     53

 57 ROSS SYSTEMS INC.
    Redwood City, CA (1972)    670     52
 58 SAPIENS USA
    Cary, NC (1991)            450     51
 59 PEOPLESOFT, INC.
    Walnut Creek, CA (1987)    362     49
 60 FRAME TECHNOLOGY CORP.
    San Jose, CA (1986)        381     46

 61 LANDMARK SYSTEMS CORP.*
    Vienna, VA (1982)          204     43
 62 QUARTERDECK OFFICE SYSTEMS
    Santa Monica, CA (1982)    277     42
 63 SYNON CORP.*
    Larkspur, CA (1983)        376     42
 64 CADRE TECHNOLOGIES, INC.*
    Beaverton, OR (1982)       311     42

               (* = privately held)

 65 POWERSOFT CORP.
    Burlington, MA (1974)      365     41
 66 SOFTWARE 2000, INC.*
    Hyannis, MA (1981)         425     40
 67 RATIONAL*
    Santa Clara, CA (1980)     334     40
 68 INTEGRAL
    Walnut Creek, CA (1972)    400     40

 69 WALKER INTERACTIVE SYSTEMS, INC.
    San Francisco, CA (1969)   482     39
 70 TRINZIC CORP.
    Palo Alto, CA (1992)       280     39
 71 LAWSON SOFTWARE*
    Minneapolis, MN (1975)     375     38
 72 SPSS, INC.*
    Chicago, IL (1975)         366     38

 73 PLATINUM SOFTWARE CORP.
    Irvine, CA (1984)          n/a     36
 74 MACRO 4, INC.
    Parsippany, NJ (1968)      189     35
 75 RAXCO, INC.*
    Rockville, MD (1977)       275     33
 76 ALSYS*
    San Diego, CA (1980)       280     33

 77 BGS SYSTEMS, INC.
    Waltham, MA (1975)         180     31
 78 GROUP 1 SOFTWARE, INC.
    Lanham, MD (1981)          185     30
 79 VISUAL NUMERICS INC.
    Houston, TX (1992)         167     30
 80 CYBORG SYSTEMS, INC.*
    Chicago, IL (1974)         257     30

 81 VMARK SOFTWARE INC.
    Framingham, MA (1984)      185     29
 82 PRAXIS INTERNATIONAL, INC.*
    Cambridge, MA (1965)       250     29
 83 SEER TECHNOLOGIES*
    Cary, NC (1990)            463     28
 84 CODA, INC.*
    Manchester, NH (1979)      324     28

 85 DATASTORM TECHNOLOGIES, INC.*
    Columbia, MO (1985)        153     27
 86 BACHMAN INFORMATION SYSTEMS, INC.
    Burlington, MA (1983)      300     26
 87 MUST SOFTWARE INT'L.*
    Norwalk, CT (1987)         280     26
 88 COMPUTRON TECHNOLOGIES CORP.*
    Rutherford, NJ (1982)      255     26

 89 CAERE CORP.
    Los Gatos, CA (1973)       189     26
 90 MANUGISTICS GROUP INC.
    Rockville, MD (1969)       300     25
 91 INFORMATION DIMENSIONS, INC.*
    Dublin, OH (1986)          225     24
 92 LBMS
    Houston, TX (1977)         425     23

 93 SYSTEMS UNION INC.*
    White Plains, NY (1981)    212     23
 94 4TH DIMENSION SOFTWARE
    Irvine, CA (1983)          318     23
 95 INTERACTIVE DEVELOPMENT ENVIRONMENTS*
    San Francisco, CA (1983)   180     23
 96 CONSILIUM, INC.
    Mountain View, CA (1978)   235     23

 97 WIND RIVER SYSTEMS*
    Alameda, CA (1983)         160     22
 98 VERDIX CORP.
    Herndon, VA (1982)         155     22
 99 DATAEASE INTERNATIONAL, INC.*
    Trumbull, CT (1982)        250     22
100 NEXT COMPUTER INC.
    Redwood City, CA (1985)    250     22

               (* = privately held)


             End of Software Vendors.





SoftWindows
Windows emulation software for the PowerPC and
various UNIX platforms from Insignia Solutions.
See PowerMac.



SOG
(Small Outline Gullwing)  Same as SOIC.



SOHO
(Small Office/Home Office)  Refers to the small
business or business-at-home user.  This market
segment demands as much or more than the large
corporation.  The small business entrepreneur
generally wants the latest, greatest and fastest
equipment, and this market has always benefited
from high technology, allowing it to compete on a
level playing ground with the bigger companies.



SOIC
(Small Outline IC)  A small-dimension, surface
mount DIP that uses gullwing-shaped pins extending
outward.



SOJ
(Small Outline J lead)  A small-dimension, surface
mount DIP that uses J-shaped pins extending inward.



Solaris 2.0
A multitasking, multiprocessing distributed
computing environment from SunSoft for SPARC
computers, 386s and up and the PowerPC.  Solaris
2.0 for SPARC machines is backward compatible with
Solaris 1.0, and includes the SunOS 5.0 operating
system (based on UNIX SVR4), Sun's ONC networking
products (NFS, NIS, etc.), OpenWindows (Sun's
version of X Windows) and Sun's Open Look graphical
interface with DeskSet utilities that provide
multimedia mail and drag & drop capability.

   Solaris 2.0 for x86 machines runs applications
written for Solaris and Sun's INTERACTIVE UNIX for
x86 machines.

   Solaris optionally includes Sun's Wabi emulator,
which runs Windows applications by turning Windows
calls into X Window calls.  DOS emulation is
provided by third-party products.  Sun is also
developing a version of Solaris for the PowerPC.

   Solaris provides an enterprise-wide networking
environment that can manage up to 40,000 nodes from
one central station.



solder mask
An insulating pattern applied to a printed circuit
board that exposes only the areas to be soldered.



solenoid
A magnetic switch that closes a circuit, often used
as a relay.



solid logic
Same as solid state.



solid modeling
A mathematical technique for representing solid
objects.  It is the least abstract form of CAD.
Unlike wireframe and surface modeling, solid
modeling systems ensure that all surfaces meet
properly and that the object is geometrically
correct.  A solid model can also be sectioned (cut
open) to reveal its internal features.  Solids
allow interference checking, which tests to see if
two or more objects occupy the same space.



solid state
An electronic component or circuit made of solid
materials, such as transistors, chips and bubble
memory.  There is no mechanical action in a solid
state device, although an unbelievable amount of
electromagnetic action takes place within.

   For data storage, solid state devices are much
faster and more reliable than mechanical disks and
tapes, but are more expensive.  Although solid
state costs continually drop, disks, tapes and
optical disks also continue to improve their
cost/performance ratio.

  The first solid state device was the "cat's
whisker" of the 1930s.  A whisker-like wire was
moved around on a solid crystal in order to detect
a radio signal.



solid state disk
A disk drive made of memory chips used for high-
speed data access or in hostile environments.
Solid state disks are used in battery-powered,
hand-held devices as well as in desktop units with
hundreds of megabytes of storage that contain their
own UPS systems.

   Different types of storage chips are used for
solid state disks, both volatile and non-volatile.
However a solid state disk looks like a standard
disk drive to the operating system, not a
proprietary one that requires additional drivers.
See flash disk.



solid state memory
Any transistorized, semiconductor or thin film
memory that contains no mechanical parts.



solid state relay
A relay that contains no mechanical parts.  All
switching mechanisms are semiconductor or thin film
components.



solver
Mathematical mechanisms that allow spreadsheets to
perform goal seeking.



SOM
(1) (System Object Model)  An object architecture
from IBM that provides a full implementation of the
CORBA standard.  SOM is language independent and is
supported by a variety of large compiler and
application development vendors.

   It is expected that IBM will promote SOM heavily
because its future operating systems are built
around objects.  DSOM, for distributed SOM, allows
objects to be used across the network.

(2) (Self Organizing Map)  A two-dimensional map
that shows relationships in a neural network.



SONET
(Synchronous Optical NETwork)  A fiber optic
transmission system for high-speed digital traffic.
Employed by telephone companies and common
carriers, SONET speeds range from 51 megabits to
multiple gigabits per second.  SONET is an
intelligent system that provides advanced network
management, a standard optical interface and more
flexibility than the T1 and T3 lines now in common
use.  Although it is expected to eventually
obsolete T-carrier lines, SONET can be used to
carry existing T-carrier traffic in the meantime.

   SONET is specified in the Broadband ISDN (BISDN)
standard.  The European counterpart is SDH.
Following are the levels of service.  The STS
(Synchronous Transport Signal) designation refers
to the electrical signal, and OC (Optical Carrier)
refers to the optical signal, which is identical
because it is a one-to-one conversion.


              SONET CIRCUITS

       Service             Speed (Mbps)
   STS-1    OC-1      51.84 (28 DS1s or 1 DS3)
   STS-3    OC-3     155.52 (3 STS-1s)
   STS-3c   OC-3c    155.52 (concatenated)
   STS-12   OC-12    622.08 (12 STS-1s, 4 STS-3s)
   STS-12c  OC-12c   622.08 (12 STS-1s, 4 STS-3c's)
   STS-48   OC-48   2488.32 (48 STS-1s, 16 STS-3s)
   STS-192  OC-192  9953.28 (192 STS-1s, 64 STS-3s)





sort
To reorder data into a new sequence.  The operating
system can typically sort file names and text
lists.  Word processors typically allow lines of
text to be reordered, and database programs sort
records by one or more fields, often generating a
new file.



sort algorithm
A formula used to reorder data into a new sequence.
Like all complicated problems, there are many
solutions that can achieve the same results.  One
sort algorithm can resequence data faster than
another.  In the early 1960s, when tape was "the"
storage medium, the sale of a computer system may
have hinged on the sort algorithm, since without
direct access capability, every transaction had to
be sorted into the sequence of the master file.



sort field
Same as sort key.



sort key
A field or fields in a record that dictate the
sequence of the file.  For example, the sort keys
STATE and NAME arrange the file alphabetically by
name within state.  STATE is the major sort key,
and NAME is the minor key.



sorter
(1) A sort program.

(2) A person who manually puts data into a specific
sequence.

(3) An early tabulating machine that routed punched
cards into separate stackers based on the content
of a card column.  The complete operation required
passing the cards through the machine once for each
column sorted.



SOS
(1) (Silicon On Sapphire)  An MOS chip-fabrication
method that places a thin layer of silicon over a
sapphire substrate (base).

(2) (Sophisticated Operating System)  The operating
system used on the Apple III.



sound bandwidth
A range of sound frequencies.  The human ear can
perceive approximately from 20 to 20,000Hz, but
human voice is confined to within 3,000Hz.



Sound Blaster
A family of sound cards from Creative Labs, Inc.,
Milpitas, CA.  The Sound Blaster protocol has
become a de facto audio standard for PCs.



sound board
Same as sound card.



sound card
Also called sound board and audio adapter, it is a
personal computer expansion board that records and
plays back sound, providing outputs directly to
speakers or an external amplifier.  Many sound
cards also include MIDI capability.

   Standards
   The three major standards in the PC world for
   sound are SoundBlaster, Ad Lib and Windows.
   Some cards support all three, which is more
   desirable if you have a mix of DOS and Windows
   multimedia applications.


   Sampling Rates and Sampling Sizes
   Sampling rates of 11.025, 22.05 and 44.1KHz
   define the number of times per second analog
   sound is turned into a number.  Sampling sizes
   of 8-bit and 16-bit define the granularity, or
   fineness, of the sample.  An 8-bit size means
   each sample is measured on a scale of 256
   increments; a 16-bit sample is 65,536
   increments.  The larger the number in both
   cases, the more precise the sample and the more
   realistically musical passages can be captured.

      The MPC Level 1 specification requires the
   card to be able to record sound at 8-bits and
   11.025KHz.  It must be able to play back at
   11.025 and 22.05KHz.  See MPC.

      The MPC Level 2 specification requires the
   card to be able to record and play back at 16
   bits at all three sampling rates.


   SND, WAV and MIDI Files
   Sound files, (.SND extension) and Windows wave
   files (.WAV extension) are digital sound files.
   Analog sound has been converted into digital
   form, and these files take up a lot of disk
   space.  Without compression, ten seconds of
   high-fidelity sound (16-bit stereo at 44.1KHz)
   can take more than 5MB.

      MIDI files (.MID extendion) contain a coded
   representation of the musical notes as played on
   an instrument; for example, middle C on a piano.
   MIDI files take up considerably less space than
   SND and WAV files, but require a MIDI
   synthesizer on the sound card.  MPC requires
   MIDI on the board.

       There are two kinds of MIDI sound
   reproduction methods used in sound cards.  FM
   synthesis simulates musical notes.  Wave table
   synthesis (or waveform synthesis) actually holds
   digitized samples of the notes and produces
   richer sound.

      Another MIDI feature is the number of voices,
   or notes, that can be played back
   simultaneously.  MPC requires an 8-voice
   synthesizer, but high-quality sound cards can
   have up to 32 MIDI voices.


   Compression Standards
   Compression for wave files helps reduce disk
   space, but can cause some loss in fidelity.
   Some sound cards provide built-in compression,
   but there are various methods that are used.
   The MPC Council recommends the ADCPM compression
   method adopted by the Interactive Multimedia
   Association (IMA).


                Multimedia Speakers
Speakers placed in close proximity to CRT screens
must be shielded, or you will see visible
interference on the screen.  All speakers designed
for personal computer use are shielded.





source
(1) The source of current in a MOS transistor.
Same as emitter in a bipolar transistor.

(2) (The Source)  An online information service in
McLean, VA, launched in 1979 and purchased by
CompuServe in 1989.



source code
A program in its original form as written by the
programmer.  It is not executable by the computer
directly.  It must be converted into machine
language by compilers, assemblers and interpreters.

   In some cases, source code can be converted into
another dialect or a different language by a
conversion program.



source code compatible
Able to run a program on a different platform by
recompiling its source code into that machine code.



source computer
The computer in which a program is being assembled
or compiled.  Contrast with object computer.



source data
The original data that is handwritten or printed on
a source document or typed into the computer system
from a keyboard or terminal.



source data acquisition
Same as source data capture.



source data capture
Capturing data electronically when a transaction
occurs; for example, at the time of sale.



source directory
The directory from which data is obtained.



source disk
The disk from which data is obtained.  Contrast
with target disk.



source document
The paper form onto which data is written.  Order
forms and employment applications are examples.



source drive
The disk or tape drive from which data is obtained.
Contrast with target drive.



source language
The language used in a source program.  Contrast
with target language and machine language.  See
source code.



source program
A program in its original form, as written by the
programmer.  See source code.



source routing
A communications protocol in which stations are
aware of bridges in the network and route messages
via the bridges.  Contrast with transparent
bridging.  See SRT.



source statement
An instructional phrase in a programming language
(source language).



SP2
A UNIX-based massively parallel computer system
from IBM that supports from two to 512 nodes.  It
uses IBM's POWERparallel architecture and includes
a communications system between nodes called the
High-Performance Switch.  In 1994, the University
of New Mexico's Maui High Performance Computing
Center installed a 400-node SP2, which provides 100
gigaflops of computational power.



SPA
(Software Publishers Association)  A trade
organization of the personal computer software
industry that supports legislation for copyright
enforcement.  It conducts raids on organizations
suspected of illegal copying and files lawsuits
against violators.

   To blow the whistle on a company that has a
policy of making illegal copies, call 800/388-PIR8.
Address: 1730 M St., N.W., Washington, DC 20036,
202/452-1600.



space
In digital electronics, a 0 bit.  Contrast with
mark.



space/time
The following units of measure are used to define
storage and transmission capacities.

S P A C E                           Bits or bytes
Kilo (K)  Thousand                          1,024
Mega (M)  Million                       1,048,576
Giga (G)  Billion                   1,073,741,824
Tera (T)  Trillion              1,099,511,627,776
Peta (P)  Quadrillion       1,125,899,906,842,624


T I M E                        Fraction of second
Millisecond (ms)  Thousandth              1/1,000
Microsecond (s)  Millionth           1/1,000,000
Nanosecond  (ns)  Billionth       1/1,000,000,000
Picosecond  (ps)  Trillionth  1/1,000,000,000,000
Femtosecond (fs)  Quadrillionth
                            1/100,000,000,000,000


Storage/channel capacity measured in:
CPU word size           Bits
Bus size                Bits
Disk, tape              Bytes
MEMORY
 Overall capacity       Bytes
 SIMM or SIP module     Bytes
 Individual chip        Bits

Transmission speed measured in:
Network line/channel       Bits per second
Disk transfer rate         Bits or bytes per second
Disk access time           Milliseconds
Memory access time         Nanoseconds
Machine cycle              Microseconds/Nanoseconds
Instruction execution      Microseconds/Nanoseconds
Transistor switching       Nanoseconds, Picoseconds
                            and Femtoseconds



spaghetti code
Program code written without a coherent structure.
The logic moves from routine to routine without
returning to a base point, making it hard to
follow.  It implies excessive use of the GOTO
instruction, which directs the computer to branch
to another part of the program without a guarantee
of returning.

   In structured programming, functions are used,
which are subroutines that guarantee a return to
the instruction following the one that called it.



SPARC
(Scalable Performance ARChitecture)  A 32-bit RISC
CPU developed by Sun and licensed by SPARC
International, Menlo Park, CA.



spatial data
Data that is represented as 2-D or 3-D images.



spawn
To launch another program from the current program.
The DOS TSR version of this database is called
POPGLOSS.EXE.  It resides in RAM and "spawns"
GLOSS.EXE when the hotkey is pressed.



spec
See specs and specification.



Spec 1170
See X/Open.



spec sheet
A detail listing of the components of a system.



SPECfp
See SPECmark.



special character
Non-alphabetic or non-numeric character, such as @,
#, $, %, &, * and +.



special-purpose computer
A computer designed from scratch to perform a
specific function.  Contrast with general-purpose
computer.



special-purpose language
A programming language designed to solve a specific
problem or class of problems.  For example, LISP
and Prolog are designed for and used extensively in
AI applications.  Even more specific are languages
such as COGO, for civil engineering problems, and
APT for directing machine tools.  Contrast with
general-purpose language.



specialized mobile radio
See SMR.



specification
A definition (layout, blueprint, design) of
hardware or software.  See specs and functional
specification.



SPECint
See SPECmark.



SPECmark
(Systems Performance Evaluation Cooperative MARK)
A suite of 10 benchmarks that test integer and
floating point performance of a computer.  Results
are reported as SPECint and SPECfp numbers.

   A VAX-11\780 is a one-SPECmark machine, and
SPECmarks closely track VUPs ratings from Digital's
internal benchmarks.



specs
(SPECificationS)  The details of the components
built into a device.  See specification.



spectral color
In computer graphics, the color of a single
wavelength of light, starting with violet at the
low end and proceeding through indigo, blue, green,
yellow and orange and ending with red.



spectral response
The variable output of a light-sensitive device
that is based on the color of the light it
perceives.



spectrum
A range of electromagnetic frequencies.  See
electromagnetic spectrum and radio.



speech recognition
Same as voice recognition.



speech synthesis
Generating machine voice by arranging phonemes (k,
ch, sh, etc.) into words.  It is used to turn text
input into spoken words for the blind.  Speech
synthesis performs realtime conversion without a
pre-defined vocabulary, but does not create human-
sounding speech.  Although individual spoken words
can be digitized into the computer, digitized voice
takes a lot of storage, and resulting phrases still
lack inflection.



speed buffering
A technique that compensates for speed differences
between input and output.  Data is accepted into
the buffer at high speed and transferred out at low
speed, or vice versa.



Speed Doubler
The name of Intel's clock-doubled DX2 chips.



speed of electricity/light
Electricity and light travel at approximately
186,000 miles per second, which is seven times
around the equator per second.  This inherent speed
of Mother Nature is why computers are so fast.
Within the tiny chip, electricity has to flow only
a couple of millimeters, and, within an entire
computer, only a few feet.

   As fast as that is, it's never fast enough.
There is resistance in the lines, and even though
transistors switch in billionths of a second, CAD,
image processing and scientific applications are
always exhausting the fastest computers.



Speedo
A scalable font technology from Bitstream Inc.,
Cambridge, MA.  See FaceLift.



Speedware
A development system from Speedware Corporation,
Toronto, Ontario, that creates programs for the HP
3000, RS/6000 and AS/400.  Applications can also be
ported to run on DOS and Windows machines with
runtime versions of Speedware for those platforms.



spelling checker
A separate program or word processing function that
tests for correctly-spelled words.  It can test the
spelling of a marked block, an entire document or
group of documents.  Advanced systems check for
spelling as the user types and can correct common
typos and misspellings on the fly.

   Spelling checkers simply compare words to a
dictionary of words, and the wrong use of a
correctly-spelled word cannot be detected.  See
grammar checker.



spherization
In computer graphics, turning an image into a
sphere.



SPI
(Service Provider Interface)  The programming
interface for developing Windows drivers under
WOSA.  In order to provide common access to
services, the application (query, word processor,
e-mail program, etc.) is written to a particular
WOSA-supported interface, such as ODBC or MAPI, and
the developer of the service software (database
manager, document manager, print spooler, etc.)
writes to the SPI for that class of service.



spike
Also called a transient, a spike is a burst of
extra voltage in a power line that lasts only a
fraction of a second.  Contrast with sag.  See
power surge.



spindle
A rotating shaft in a disk drive.  In a fixed disk,
the platters are attached to the spindle.  In a
removable disk, the spindle remains in the drive.



SpinRite
A popular low-level formatting program for PCs from
Gibson Research, Aliso Viejo, CA, that reformats
without erasing data.  It rewrites only sector ID,
which may have drifted over time.  Version 3.0 can
low-level format IDE drives, which have typically
required proprietary format programs.



SPL
(1) (Systems Programming Language)  The assembly
language for the HP 3000 series.  See assembly
language for an SPL program example.

(2) (Structured Programming Language)  See
structured programming.



spline
In computer graphics, a smooth curve that runs
through a series of given points.  The term is
often used to refer to any curve.  See Bezier and
B-spline.



split screen
The display of two or more sets of data on screen
at the same time.  It implies that one set of data
can be manipulated independently of the other.
Split screens, or windows, are usually created by
the operating system or application software,
rather than the hardware.



spooler
See print spooler and spooling.



spooling
(Simultaneous Peripheral Operations OnLine)  The
overlapping of low-speed operations with normal
processing.  It originated with mainframes in order
to optimize slow operations such as reading cards
and printing.  Card input was read onto disk and
printer output was stored on disk.  In that way,
the actual business data processing was done at
high speed, since all I/O was on disk.

   Today, spooling is used to buffer data for the
printer as well as remote batch terminals.  See
print spooler.



spot color
A color that is printed from one printing plate
which contains that particular ink.  Contrast with
process color.



spread spectrum
A radio transmission that continuously changes
carrier frequency according to a unique pattern in
both sending and receiving devices.  It is used for
security as well as to allow multiple wireless
transmissions in the same space.



spreadsheet
Software that simulates a paper spreadsheet, or
worksheet, in which columns of numbers are summed
for budgets and plans.  It appears on screen as a
matrix of rows and columns, the intersections of
which are identified as cells.  Spreadsheets can
have thousands of cells and can be scrolled
horizontally and vertically in order to view them.

   The cells are filled with:

             1. labels
             2. numeric values
             3. formulas

   The labels, can be any descriptive text, for
example, RENT, PHONE or GROSS SALES.

   The values are the actual numeric data used in
the budget or plan, and the formulas command the
spreadsheet to do the calculations; for example,
SUM CELLS A5 TO A10.

   Formulas are easy to create, since spreadsheets
allow the user to point to each cell and type in
the arithmetic operation that affects it.  Roughly
speaking, a formula is created by saying "this cell
PLUS that cell TIMES that cell."

   The formulas are the spreadsheet's magic.  After
numbers are added or changed, the formulas will
recalculate the data either automatically or with
the press of a key.  Since the contents of any cell
can be calculated with or copied to any other cell,
a total of one column can be used as a detail item
in another column.  For example, the total from a
column of expense items can be carried over to a
summary column showing all expenses.  If data in
the detail column changes, its column total
changes, which is then copied to the summary
column, and the summary total changes.

   Done manually, each change would require
recalculating, erasing and changing the totals of
each column.  The automatic ripple effect allows
users to create a plan, plug in different
assumptions and immediately see the impact on the
bottom line.  This "what if?" capability makes the
spreadsheet indispensable for budgets, plans and
other equation-based tasks.

   The spreadsheet originated with VisiCalc in 1978
for the Apple II, and was followed by SuperCalc,
Multiplan, Lotus 1-2-3 and a host of others.


              CLASSES OF SPREADSHEETS

                        2-D
Every spreadsheet can create a two-dimensional
matrix of rows and columns.  In order to summarize
data, totals from various parts of the spreadsheet
can be summed to another part of the spreadsheet.


                        3-D
Each cell in the spreadsheet has an X, Y and Z
reference.  For example, a spreadsheet of expense
items by month uses two dimensions, but expense
items by month by department requires three.

   While this method is superior for consolidating
and summarizing data, it lacks some of the
flexibility required by sophisticated applications.
In addition, all data typically resides in one file
as with a standard 2-D spreadsheet.


                 Multidimensional
Multidimensional spreadsheets support more than
three axes and allow the data and the relationships
to be viewed from different perspectives.  Data is
not stored by cell references (A1, B2, etc.), but
by name.  Formulas are not placed into cells as in
a traditional spreadsheet, but are defined
separately as in a modeling language; for example,
"gross profit=gross sales-cost of goods."

   With name references, data can be used in
multiple spreadsheets with greater accuracy, and
new spreadsheets can be created more easily.
However, since data isn't tied to cell references,
this method lacks the flexibility and ease of use
that caused the traditional 2-D spreadsheet to
revolutionize the computer industry.


            Analytical Database Engine
This method stores the data separate and apart from
the formulas.  Data is stored in a central
database, but the formulas are stored in a
spreadsheet in the traditional manner.  When the
spreadsheet is called up, the values from the
database are displayed in the spreadsheet, which
functions as a viewer into the database.  This
method is the best of both worlds.  It allows for
multiple dimensions to be easily created while
maintaining consistency with the ease of use of the
traditional spreadsheet for creating the viewing
models.



spreadsheet compiler
Software that translates spreadsheets into stand-
alone programs that can be run without the
spreadsheet package that created them.



Spreadsheet Connector
See TM/1.



sprite
An independent graphic object controlled by its own
bit plane (area of memory).  Commonly used in video
games, sprites move freely across the screen,
passing by, through and colliding with each other
with much less programming.



sprocket feed
Same as pin feed.



SPS
(Standby Power System)  A UPS system that switches
to battery backup upon detection of power failure.



SPS Association
A nonprofit organization dedicated to an open
PostScript standard.  Address: 7 Stuart Road,
Chelmsford, MA 01824.



SPSS
A statistical package from SPSS, Inc., Chicago,
that runs on PCs, most mainframes and minis and is
used extensively in marketing research.  It
provides over 50 statistical processes, including
regression analysis, correlation and analysis of
variance.  Originally named Statistical Package for
the Social Sciences, it was written by Norman Nie,
a professor at Stanford.  In 1976, he formed SPSS,
Inc.



spt
(Sectors Per Track)  The number of sectors in one
track.



SPX
(Sequenced Packet EXchange)  The NetWare
communications protocol used to control the
transport of messages across a network.  SPX
ensures that an entire message arrives intact and
uses NetWare's IPX protocol as its delivery
mechanism.  Application programs use SPX to provide
client/server and peer-to-peer interaction between
network nodes.  SPX provides services at layer 4 of
the OSI model.



SQL
(Structured Query Language)  Pronounced "SQL" or
"see qwill," a language used to interrogate and
process data in a relational database.  Originally
developed by IBM for its mainframes, all database
systems designed for client/sever environments
support SQL.  SQL commands can be used to
interactively work with a database or can be
embedded within a programming language to interface
to a database.  Programming extensions to SQL have
turned it into a full-blown database programming
language.

   Some of the major database management systems
(DBMSs) that support SQL are DB2, SQL/DS, Oracle,
Sybase, SQLbase, INFORMIX and CA-OpenIngres
(Ingres).

   The following SQL query selects customers with
credit limits of at least $5,000 and puts them into
sequence from highest credit limit to lowest.  The
bold words are SQL verbs.


       SELECT NAME, CITY, STATE, ZIPCODE
       FROM CUSTOMER
       WHERE CREDITLIMIT > 4999
       ORDER BY CREDITLIMIT DESC



                 SQL - A Standard?
The American National Standards Institute (ANSI)
has standardized the SQL language, but it does not
cover all the bases.  Each database management
system (DBMS) has its own enhancements, quirks and
tricks that, for all intents and purposes, makes
SQL non standard.  Moving an application from one
SQL database to another generally requires hand
tailoring to convert some of the SQL statements.
So what's new?  See CLI, ODBC and IDAPI.





SQL/DS
(SQL/Data System)  A full-featured relational DBMS
from IBM for VSE and VM environments that has
integrated query and report writing facilities.



SQL engine
A program that accepts SQL commands and accesses
the database to obtain the requested data.  Users'
requests in a query language or database language
must be translated into an SQL request before the
SQL engine can process it.



SQL Forms
An earlier version of Oracle Forms, an application
development tool for client/server systems.  See
CDE.



SQL precompiler
Software that turns SQL commands written within a
source program into the appropriate function calls
for the database management system (DBMS) being
used.  After the SQL precompiler stage, the
resulting program is translated into machine
language by the COBOL compiler or the compiler of
whatever language the program is written in.  See
embedded SQL.



SQL Server
A relational DBMS from Sybase, Inc., Emeryville,
CA, that runs on OS/2 and Windows NT PCs, NetWare
servers, VAXs and UNIX servers.  It is designed for
client/server use and is accessed by applications
using SQL or via Sybase's own QBE and decision
support utilities.

   SQL Server is also available through Microsoft
as Microsoft SQL Server for OS/2 and Microsoft SQL
Server for Windows NT.  Since Microsoft also sells
SQL Server, it has become customary to refer to
Sybase SQL Server as simply the Sybase database or
Sybase DBMS.



SQL Windows
See SQLWindows.



SQL*Forms
See SQL Forms.



SQLBase
Officially known as Gupta SQLBase Server, it is a
relational DBMS for DOS, OS/2, NetWare, NT and Sun
servers from Gupta Corporation, Menlo Park, CA.  It
is one of the leading database programs on servers
running OS/2 and NetWare.  SQLBase has been Gupta's
flagship product since the company was founded in
1984.  See SQLWindows.



SQLWindows
Officially known as Gupta SQLWindows, it is a high-
level application development system for Windows
from Gupta Corporation, Menlo Park, CA.  It is used
to write Windows applications that access SQL
databases in a client/server environment.
SQLWindows Solo is a demonstration version that
provides all of the functionality of SQLWindows,
but works only on a single machine.  See SQLBase.



square wave
A graphic image of a digital pulse as visualized on
an oscilloscope.  It appears square because it
rises quickly to a particular amplitude, stays
constant for the duration of the pulse and drops
fast at the end of it.



SQUID
(Superconducting Quantum Interference Device)  An
electronic detection system that uses Josephson
junctions circuits.  It is capable of detecting
extremely weak signals.



SRAM
See static RAM.



SRPI
(Server Requester Programming Interface)  An IBM
programming interface that allows a PC to interact
with a mainframe.  See ECF.



SRT
(Source Routing Transparent)  An IEEE-standard
technology that allows bridging between Ethernet
and token ring networks (Token Ring, FDDI).
Existing token ring bridges are not compatible with
SRT bridges, but Proteon's (Westborough, MA)
Adaptive SRT bridges are compatibile with the
installed base.  See source routing.



SS/DD
(Single Sided/Double Density)  Refers to earlier
floppy disk formats that store data on only one
side of the disk.



SSA
(Serial Storage Architecture)  A peripheral
interface from IBM that transfers data at
20MBytes/sec in one direction, but can operate
full-duplex.  SSA's ring configuration allows
remaining devices to function if one fails.  SCSI
software can be mapped over SSA allowing existing
SCSI devices to be used.  SSA is expected to gain
momentum in 1995.



SSCP
(System Services Control Point)  A controlling
program in an SNA domain.  It resides in the host
and is a component within VTAM.



SSD
See solid state disk.



SSE
A Protected Mode full-screen editor in OS/2.



SSI
(Small Scale Integration)  Up to 100 transistors on
a chip.  See MSI, LSI, VLSI and ULSI.



SSP
(System Support Program)  A multiuser, multitasking
operating system from IBM that is the primary
control program for System/34 and System/36.



ST
A personal computer series from Atari that uses a
Motorola 68000 CPU and includes the GEM interface,
ROM-based TOS operating system, a MIDI interface
and a three-voice sound chip.  The 520ST has 512K
RAM; the 1040ST has 1MB.  Display is 640x200, 16
colors.  The current model is the 1040STE.



ST connector
A fiber-optic cable connector that uses a bayonet
plug and socket.  It was the first de facto
standard connector for optical fibers for most
commercial wiring.  See SMA connector and ST
connector.



ST412
An enhancement to the ST506 standard that buffers
track-to-track commands for a continuous seek to
the required track.  All new ST506
drives/controllers incorporate this, thus ST412,
ST506/412 and current ST506 units are the same.



ST506
A hard disk interface commonly used in drives of
40MB and less.  It transfers data at 625 KBytes/sec
and uses the MFM encoding method.  See ST412 and
hard disk.



ST506 RLL
(ST506 Run-Length Limited)  A hard disk interface
(also called RLL interface) that increases capacity
and speed by 50% over ST506 MFM drives and
transfers data at 937 KBytes/sec.  With MFM drives
certified for increased capacity, the ST506 MFM
controller can be replaced with an ST506 RLL
controller and the drive can be reformatted.  See
hard disk.



stack
(1) A set of hardware registers or a reserved
amount of memory used for arithmetic calculations
or to keep track of internal operations.  Stacks
keep track of the sequence of routines called in a
program.  For example, one routine calls another,
which calls another and so on.  As each routine is
completed, the computer returns control to the
calling routine all the way back to the first one
that started the sequence.  Stacks used in this way
are LIFO based: the last item, or address, placed
(pushed) onto the stack is the first item removed
(popped) from the stack.

   Stacks are also used to hold interrupts until
they can be serviced.  Used in this manner, they
are FIFO stacks, in which the first item onto the
stack is the first one out of the stack.  See DOS
Stacks.

   An "internal stack failure" is a fatal error
which means that the operating system has lost
track of its next operation.  Restarting the
computer usually corrects this, otherwise the
operating system may have to be re-installed.

(2) See protocol stack and HyperCard.



stack overflow
An error condition that occurs when there is no
room in the stack for a new item.  Contrast with
stack underflow.

   In DOS, a Stack overflow error message means
that there is not enough room on the stack to
handle hardware interrupts.  Increase the number of
stacks in the STACKS= command in the CONFIG.SYS
file (see DOS Stacks).

   You can also get this message when other things
go haywire; for example, a bad expansion board or
one that isn't seated properly in the slot can
cause erratic signals eventually leading to this
message.



stack pointer
An address that identifies the location of the most
recent item placed on the stack.



stack underflow
An error condition that occurs when an item is
called for from the stack, but the stack is empty.
Contrast with stack overflow.



stacker
(1) An output bin in a document feeding or punched
card machine.  Contrast with hopper.

(2) (Stacker)  A realtime compression program from
Stac Electronics, Carlsbad, CA, that doubles
(approximately) the disk capacity of a PC and is
transparent to the user.  A coprocessor board is
optionally available.



stackware
A HyperCard application that is made up of a
HyperCard stack (data) and HyperTalk programming.



STAIRS
(STorage And Information Retrieval System)  An IBM
text document management system for mainframes.  It
allows users to search for documents based on key
words or word combinations.



standard
A specification for hardware or software that is
either widely used and accepted (de facto) or is
sanctioned by a standards organization (de jure).
See standards & compatibility.



standard cell
The finished design of an electronic function ready
for chip fabrication.  It can be as small as a
clock circuit or as large as a microprocessor.  It
is used to make custom-designed chips.



standard data format
See SDF.



standard deviation
In statistics, the average amount a number varies
from the average number in a series of numbers.



Standard Messaging Format
See SMF.



Standard Mode
Windows operation mode.  See Windows.



standards & compatibility
  Machine Languages
  Data Codes/Character Codes
  Hardware Interfaces
  Storage Media
  Operating Systems
  Communications & Networking

Standards is the most important issue in the
computer field.  As an unregulated industry, we
have wound up with thousands of data formats and
languages, but very few standards that are
universally used.  This subject is as heated as
politics and religion to vendors and industry
planners.

   No matter how much the industry talks about
compatibility, new formats and languages appear
routinely.  The standards makers are always trying
to cast a standard in concrete, while the
innovators are trying to create a new one.  Even
when standards are created, they are violated as
soon as a new feature is added by the vendor.

   If a format or language is used extensively and
others copy it, it becomes a de facto standard and
may become as widely used as official standards
from ANSI and IEEE.  When de facto standards are
sanctioned by these organizations, they become
stable, at least, for a while.

   In order to truly understand this industry, it
is essential to understand the categories for which
standards are created.



                 MACHINE LANGUAGES
Machine language is the fundamental standard for
hardware compatibility.  It is the language the CPU
understands.  All programs that are presented to
the computer for execution must be in the machine
language of that particular CPU family.

   Vendors may produce systems with different
machine languages.  IBM's mainframe family differs
from its AS/400 midrange series, which is also
different than its RS/6000 series.  Digital's newer
Alpha line of computers does not understand the
machine language of the many earlier VAX computers
that have been installed.  For all the major
hardware platforms, see hardware platforms.

   After a program is written, it must be
translated (assembled, compiled or interpreted)
into the machine language the computer understands.
In order to run in a different machine, the program
must be reassembled or recompiled into a different
machine language.

   Since the late 1960s, companies seeking a chunk
of the IBM market have designed computers that run
the same machine language as the IBM mainframes.
RCA's Spectra 70 was the first IBM-compatible
mainframe, and companies, such as Amdahl, Itel,
National Advanced Systems, Hitachi and Fujitsu have
introduced IBM-compatible mainframes at one time or
another.

   IBM PC machine language compatibility is
achieved by using a processor from Intel's 8086
family of microprocessors or one of the Intel clone
chips.

   Machine language compatibility can also be
achieved by emulation.  An emulator is software (or
hardware or both) that executes the machine
language of another computer directly.  With DOS
and Windows emulation in a UNIX workstation or a
PowerMac, users can run non-native programs in
their computer.

   Emulation goes back to the 1950s and 1960s when
IBM built a 1401 emulator in its System/360 to ease
migration from the very popular 1401s to the new
360s.  The terms simulator and emulator are used
interchangeably.





            DATA CODES/CHARACTER CODES
The data code built into the computer determines
how each letter, digit or special character ($, %,
#, etc.) is represented in binary code.
Fortunately, there are only two methods in wide
use: EBCDIC and ASCII.  IBM minis and mainframes
use EBCDIC.  ASCII is used for most everything
else, including all PCs and Macs.

   ASCII is a 7-bit code placed into an 8-bit
storage unit.  The seven bits provide the basic set
of 128 ASCII characters.  The 8th bit adds storage
for another 128 symbols, and these symbols vary
from font to font and system to system.  For
example, the DOS symbol set contains line drawing
and foreign language characters.  The ANSI symbol
set places the foreign language characters in
different locations.  In the Mac, the upper 128
symbols can be custom drawn.

   When systems are moved from one computer to
another, converting between ASCII and EBCDIC is
just a small part of the data conversion process.
It is done in conjunction with converting file
formats from the old to the new systems.

   The following is a sample of ASCII and EBCDIC
code.  See ASCII chart, hex chart and EBCDIC chart.

        Character  ASCII    EBCDIC
         space   01000000  00100000
         period  01001011  00101110
         < sign  01001100  00111100
         + sign  01001110  00101011
         $ sign  01011011  00100100
         A       11000001  01000001
         B       11000010  01000010





                HARDWARE INTERFACES
The hardware interface specifies the plugs,
sockets, cables and electrical signals that pass
through each line between the CPU and a peripheral
device or communications network.

   Common hardware interfaces for personal
computers are the Centronics parallel interface
used for printers and the RS-232 interface,
typically used for modems, graphics tablets, mice
and printers.  In addition, the IDE and SCSI
interfaces are commonly used for disks and tapes,
and the GPIB IEEE 488 standard is used for process
control instruments.

   The bus in a computer's motherboard, into which
additional printed circuit boards are inserted, is
a hardware interface.  For example, the Micro
Channel in IBM's PS/2 series accepts a physically
different board than the original PC bus.

   LANs, such as Ethernet and Token Ring, also
dictate the hardware interface as part of their
specifications.





                   STORAGE MEDIA
There are many varieties of disk packs, disk
cartridges, floppy disks, reel-to-reel tapes, tape
cartridges and tape cassettes.  Each one has its
own unique shape and size and can be used only in
drives designed to accommodate them.

   With removable media, the physical standard is
half the compatibility issue.  The other half is
the recording pattern, which is invisible to the
human eye.  Magnetic tapes and disks fresh out of
the box are blank.  The recording tracks are placed
onto the surface by the read/write head of the
storage drive.  Thus, the same floppy disk that
stores 720K bytes in one disk drive, can hold 800K
if formatted for another.  If the computer reads an
incompatible tape or reads and writes and
incompatible disk, it will signal a read/write
error.

   For minicomputers and mainframes, half-inch
magnetic tape reels and cartridges are the common
interchangeable medium.  For personal computers,
the 3.5" floppy disk is the standard.





                 OPERATING SYSTEMS
An operating system is a master control program
that manages the running of the computer system.
In all environments, except for specialized
scientific and process control applications, the
operating system interacts with the application
programs.  The application programs must "talk" to
the operating system.

   If application programs are moved to a different
computing environment, they have to be converted to
interface with a different operating system.  If a
new operating system is installed that is not
compatible with the old one, the application
programs have to be converted to the new operating
system.





            COMMUNICATIONS & NETWORKING
Transmitting between two personal computers is
relatively simple.  All that's required is a modem
and communications program in each computer that
uses the same file transfer protocol.  Most comm
programs support several protocols and are widely
used to upload and download files and gain access
to a BBS or online service.  Connecting to a major
online service, such as America Online or
CompuServe, is even more straightforward when you
use the service's front-end software.

   Communications within the enterprise is far more
complex.  Over the years, organizations have
developed islands of computer systems, each with
their own networking protocols and access methods.
The enterprise is faced with tying mainframes,
minis and PCs together for file sharing, electronic
mail and routine data processing.

   It is a duanting task connecting client machines
running DOS, Windows, Mac and Motif with servers
that run DOS, Windows, Mac, VMS, MVS and UNIX via
protocols such as TCP/IP, IPX and NetBIOS over
topologies such as Ethernet, Fast Ethernet,
Switched Ethernet, Token Ring, FDDI and ATM using
devices such as bridges, routers, hubs, switches
and gateways, and there you have it.  Oh, add
interfacing between multiple mail and messaging
systems and managing the entire process from one
management console.

   To understand the layers of protocols required
to transmit a message from one machine to another,
review the layers of the OSI model.  OSI is a
seven-layer reference model for worldwide
communications defined by the International
Standards Organization (ISO).  Originally thought
to be the future standard for communications, it
was never widely supported.  However, it does serve
as a teaching model to line up other protocols
against.  See enterprise networking, client/server
and OSI model.

   See next definition for more.





standards (continued)
  Programming Languages
  File Management Systems
  Database Management Systems
  Text Systems
  Graphics Systems



               PROGRAMMING LANGUAGES
Every software program is written in a programming
language, and there is at least one programming
language for every major CPU series.  There is
typically an assembly language and a number of
high-level languages for each family.  Assembly
languages are machine specific, and the machine
language they generate runs on only one CPU family.
Unless the machine languages are very similar, it
is difficult to translate an assembly language
program from one CPU series into another.

   The high-level programming language was created
to eliminate this machine dependency.  Programming
languages, such as COBOL, FORTRAN and BASIC are
designed to run on many different computers.
However, due to dialects of each language,
compatibility is always an issue.  Each compiler
vendor keeps adding new features to its language
thereby making it incompatible with previous or
other versions.

   By the time a new feature becomes a standard, a
dozen new features have been already implemented.
For example, dBASE became a de facto standard
business programming language.  Since 1981, dBASE
spawned competitive products, such as Clipper,
QuickSilver, Force III, dbXL and Foxbase, all of
which are incomplete versions of dBASE.  None of
them provides every command in dBASE, and they all
provide features not found in dBASE.

   There's no rule of thumb for translating one
dialect of a programming language into another.
The job may be difficult or easy.  At times,
software is written to translate one dialect into
another, as well as one programming language into
another.  If the translation program cannot
translate the program entirely, then manual
tailoring is necessary.  In these cases, it is
often easier to rewrite the program from scratch.

   Compatibility can be achieved when a programming
language conforms to the ANSI (American National
Standards Institute) standard for that language.
If the same version of an ANSI COBOL compiler is
available for two different CPUs, a program written
in ANSI COBOL will run on both machines.

   Beyond traditional programming languages such as
COBOL and C, known as third-generation languages,
or 3GLs, there are more than a hundred software
environments used to develop client/server
applications on LANs (see client/server development
system).  Each of them attempts to provide less
programming-like and more English-like syntax,
which is considered a fourth-generation language,
or 4GL.

   They also provide visual development tools to
build the graphical user interface by "drawing" the
screen and dragging and dropping symbols on it.
They may provide the ability to point and click and
drag and drop symbols to link objects together
rather than by writing programming code.  But,
these software-building tools are proliferating and
producing even more standards to be dealt with.
The programming pools are becoming increasingly
fragmented.  It's no longer just COBOL or dBASE or
C.  Now it's PowerBuilder, SQLWindows, ObjectView,
DYNASTY, OMNIS and JAM, etc. etc.





              FILE MANAGEMENT SYSTEMS
In its simplest form, a data file uses fields of
the same length for each item of data, for example,
a plain EBCDIC or ASCII file would look like:

Chris Smith   34 Main St.     Bangor      ME18567
Pat Jones     10 W. 45 St.    New York    NY10002


A common format created by BASIC programming
languages is an ASCII comma delimited file; for
example, the data above would look as follows:

"Chris Smith","34 Main St.","Bangor","ME","18567"
"Pat Jones","10 W. 45 St.","New York","NY","10002"


Both file formats above are simple, contain only
data (except for quotes and commas) and can be
easily manipulated by a word processor.  However,
data files may also contain special codes that
identify the way the data is structured within the
file.  For example, variable length records require
a code in each field indicating the size of the
field.

   Whether fixed or variable length fields, the
data in non-DBMS systems is linked directly to the
processing.  The program must know the layout of
the fields in each record that it processes, and it
cannot accept records in a different format.  In
order to process a different file format, the
program must be changed.

   Incompatible file formats often exist within the
same organization when developed separately.  The
following fixed-length records are incompatible
even though they contain the same data.  The
program that processes the first file structure
would have to be changed to process the second.

Ŀ
 Name         Address        City     StZip  

Ŀ
 Name      Address      City     StZip  






        DBMSs (DATABASE MANAGEMENT SYSTEMS)
DBMSs have their own proprietary formats for
storing data.  For example, a header record with a
unique format that contains identification data is
typically placed at the beginning of each file.
Codes may also be embedded in each record.

   Most DBMSs have an import and export capability
that converts popular database formats into their
proprietary format.  If not, the program usually
can import and export a plain EBCDIC or ASCII file,
which is stripped of all proprietary codes and can
be used as a common denominator between both
systems.  If conversion facilities cannot be found,
a custom program can be written to convert one
database format into another if documentation
describing the old format is available.

   The application program interface (API), or
language used by the application program to "talk"
to the database, is typically a proprietary
language in every DBMS.  However, SQL has become
the de facto standard database language for
client/server environments.  In theory, that means
any application program requesting data in the SQL
language would work with any DBMS that supports
SQL.  Like everything else however, there are
dialects of SQL.





                   TEXT SYSTEMS
Although the basic structure of an English-language
text file is standard throughout the world: word,
sentence, paragraph, page; every word processing,
desktop publishing and typesetting program uses its
own codes to set up the layout within a document.
For example, the code that turns on boldface in
WordPerfect Version 5.0 is [BOLD]; in WordStar,
it's ^PB.

   The codes that define a header, footer,
footnote, page number, margin, tab setting, indent
and font change are unique to the word processing
program in which the document was created or the
desktop publishing program into which the text file
is converted.  Even the codes to end a line or
paragraph are not the same.

   Document conversion is accomplished with special
conversion programs or black boxes.  Although every
word processing program has a search and replace
capability, it may not be effective for converting
embedded layout codes from one format to another.
In some programs, the search & replace simply does
not handle layout codes.  In addition, while some
systems use one code to turn a function on and
another code to turn it off, other systems use the
same code for on and off, requiring manual
verification and tailoring when using the search &
replace function.





                 GRAPHICS SYSTEMS
There are many formats for storing a picture in a
computer; but, unlike text and data files, which
are primarily made up of alphanumeric characters,
graphics formats are more complex.

   To begin with, there are the two major
categories of graphics: vector graphics (objects
made up of lines) and raster graphics (TV-like
dots).  Images stored in vector format can be moved
to another vector system typically without loss of
resolution.  There are 2-D vector formats as well
as 3-D vector formats.

   In transferring raster images among different
devices, resolution is a major concern.  Such
transfers can occur without loss of resolution as
long as the new format has the same or higher
resolution as the older one.

   Standard graphics formats allow graphics data to
be moved from machine to machine, while standard
graphics languages let graphics programs be moved
from machine to machine.  For example, GKS and
PHIGS are major graphics languages that have been
adopted by high-performance workstation and CAD
vendors.  Apple's consistent use of its QuickDraw
language helped the Macintosh become popular in
graphics-oriented applications.

   High-resolution graphics has typically been
expensive to implement due to its large storage and
fast processing requirements.  However, as personal
computers become more powerful, graphics are
becoming widely used in business applications.  The
ability to see a person's face or a product's
appearance on screen is becoming as commonplace as
text and data.



                    THE FUTURE
After 30 some years of computing, we've managed to
create more than 3,000 languages, formats and
programming interfaces in the computer business.
While some of them become bona fide standards
endorsed by recognized standards organizations,
some of the most widely used are simply de facto
standards.  The PC is the perfect example.

   The problem of standards is a never-ending
dilemma.  How do you forge ahead with new standards
if they have to cling to the old designs for
compatibility?  At some point, the new has to be a
break from the past, because the previous
infrastructure is not usable.  It seems to be the
way of things.

   For a list of standards organizations, see
Lessons Associations.





standards bodies
See Lessons Associations.



standby power system
See SPS.



Star
The Xerox workstation that formally introduced the
graphical user interface and desktop metaphor in
1981.  Although unsuccessful, it was inspiration
for Xerox's subsequent computers and for Apple's
Lisa and Macintosh.  See Alto.



star network
A communications network in which all terminals are
connected to a central computer or central hub.
PBXs are prime examples as well as IBM's Token Ring
and AT&T's Starlan LANs.



Starlan
A local area network from AT&T that uses twisted
pair wire, the CSMA/CD access method, transmits at
1 Mbps and uses a star or bus topology.  In 1988,
Starlan was renamed Starlan 1, and Starlan 10 was
introduced, a 10 Mbps Ethernet version that uses
twisted pair or optical fibers.



start bit
In asynchronous communications, the bit transmitted
before each character.



start/stop transmission
Same as asynchronous transmission.



startup routine
A routine that is executed when the computer is
booted or when an application is loaded.  It is
used to customize the environment for its
associated software.



STARTUP.CMD
(STARTUP.CoMmanD)  An OS/2 file that is executed
immediately upon startup.  It contains instructions
that can initialize operating system settings and
call in a specific application program.  The DOS
counterpart is AUTOEXEC.BAT.



stat mux
(STATistical MUltipleXor)  See statistical
multiplexor.



state-of-the-art
The most advanced technique or method used.



statement
In a high-level programming language, a descriptive
phrase that generates one or more machine language
instructions in the computer.  In a low-level
assembly language, programmers write instructions
rather than statements, since each source language
instruction is translated into one machine language
instruction.



static binding
Same as early binding.



static column memory
A type of page mode memory that requires less
electronic pulsing in order to access the memory
bits.



static electricity
A stationary electrical charge that is the result
of intentional charging or of friction in low-
humidity environments.



static RAM
A memory chip that requires power to hold its
content.  Static RAM chips have access times in the
10 to 30-nanosecond range.  Dynamic RAMs are
usually above 30, and Bipolar and ECL memories are
under 10.

     A static RAM bit is made up of a pretzel-like
flip-flop circuit that lets current flow through
one side or the other based on which one of two
transistors is activated.  Static RAMs do not
require refresh circuitry as do dynamic RAMs, but
they take up more space and use more power.



static SQL
See embedded SQL.



station
A computer, workstation or terminal in a network.
Same as node.



statistical multiplexor
In communications, a device that combines several
low-speed channels into a single high-speed channel
and vice versa.  A standard multiplexor is set to a
fixed interleaving pattern, but the statistical
multiplexor can analyze the traffic load and
dynamically switch to different channel patterns to
speed up transmission.



status line
An information line displayed on screen that shows
current activity.



STD bus
A bus architecture used in medical and industrial
equipment due to its small size and rugged design.
Originally an 8-bit bus, extensions have increased
it to 16 and 32 bits.



stealth virus
A virus that is able to keep itself from being
detected.  See polymorphic virus.



step frame
To capture video images one frame at a time.  If a
computer is not fast enough to capture analog video
in realtime, the video can be forwarded and
processed one frame at a time.



stepper motor
A motor that rotates in small, fixed increments and
is used to control the movement of the access arm
on a disk drive.  Contrast with voice coil.



stereophonic
Sound reproduction that uses two or more channels.
Contrast with monophonic.



stick font
Same as vector font.



stick model
A picture made of lines, or vectors.  For example,
in biomedical applications, the limbs of a person
or animal are converted into lines so that the
motion can be visually observed and graphically
plotted and analyzed.



stiction
(STatic frICTION)  A type of hard disk failure in
which the read/write heads stick to the platters.
The lubricant used on certain drives heats up and
liquifies.  When the disk is turned off, it cools
down and can become like a glue.



STN
See LCD.



stop bit
In asynchronous communications, a bit transmitted
after each character.



storage device
A hardware unit that holds data.  In this database,
the term refers only to external peripheral
equipment, such as disk and tape, in contrast with
memory (RAM).



storage hierarchy
The range of memory and storage devices within the
computer system.  The following list runs from
lowest to highest speed.

  Low     Punched cards
 Speed    Punched paper tape
         Removable cartridge mass storage
          devices (non-disk)
         Magnetic tape
         Floppy disks
         CD-ROM and optical disks
         Magnetic disks (movable heads)
         Magnetic disks (fixed heads)
         Bubble memory
         Low-speed bulk memory
         Main memory
         Cache memory
 High     Microcode
 Speed    Registers





storage management
Administration of a backup and archival program
that moves less-timely information to more
economical storage media; for example, from
magnetic disk to optical disk to magnetic tape.
See SMS and HSM.



Storage Management Services
See SMS.



storage media
Refers to disks, tapes and bubble memory
cartridges.



store and forward
The temporary storage of a message for transmission
to its destination at a later time.  Store and
forward techniques allow for routing over networks
that are not accessible at all times.  For example,
messages crossing time zones can be forwarded
during daytime at the receiving side, or messages
can be forwarded at night in order to obtain off-
peak rates.  See messaging protocol.



store-and-forward switch
A switching device that stores a complete incoming
data packet before it is sent out.  Such switches
are used when incoming and outgoing speeds differ.
Contrast with cut-through switch.



stored procedure
In a database management system (DBMS), it is an
SQL program that is stored in the database which is
executed by calling it directly from the client or
from a database trigger.  When the SQL procedure is
stored in the database, it does not have to be
replicated in each client.  This saves programming
effort especially when different client user
interfaces and development systems are used.
Triggers and stored procedures are built into DBMSs
used in client/server environments.



stored program concept
The fundamental computer architecture in which the
computer acts upon (executes) internally-stored
instructions.  See von Neumann architecture.



STP
(Shielded Twisted Pair)  Telephone wire that is
wrapped in a metal sheath to eliminate external
interference.  See twisted pair.



Strand88
A parallel processing programming language
developed by AI Ltd., England.



Stratus
(Stratus Computer, Inc., Marlboro, MA)  A
manufacturer of fault-tolerant computers founded in
1980.  It supports both the VOS and FTX UNIX
operating systems on its XA/R line of i860-based
systems.  Its earlier XA/2000 line was Motorola
680x0 based.  Future systems will use HP's PA-RISC
architecture.



stream
(1) A contiguous group of data.

(2) The I/O management in the C programming
language.  A stream is a channel through which data
flows to/from a disk, keyboard, printer, etc.



stream-oriented file
A type of file, such as a text document or digital
voice file, that is more openly structured than a
database file.  Text and voice files contain
continuous streams of characters, whereas database
files contain many small repeating structures
(records).



streaming data
Data that is structured and processed in a
continous flow, such as digital audio and video.



streaming tape
A high-speed magnetic tape drive that is frequently
used to make a backup copy of an entire hard disk.



Streamline
A Macintosh tracing program from Adobe Systems
Inc., Mountain View, CA.  It converts scanned or
MacPaint images into PostScript files, which can be
modified in Illustrator 88.



STREAMS
A feature of UNIX System V that provides a standard
way of dynamically building and passing messages up
and down a protocol stack.  NetWare 3.x and Windows
NT also support the STREAMS interface.  STREAMS
passes messages from the application "downstream"
through the STREAMS modules to the network driver
at the end of the stack.  Messages are passed
"upstream" from the driver to the application.  A
STREAMS module would be a transport layer protocol
such as TCP and SPX or a network layer protocol
such as IP and IPX.

   STREAMS modules can be dynamically changed
(pushed and popped) at runtime, allowing the stack
to be used for multiple protocols.  Two important
STREAMS components are the TLI and LSL interfaces,
which provide common languages to the transport and
data link layers.  See TLI, LSL, ODI and OSI.



Streettalk
A directory service in the VINES network operating
system.



STRETCH
The code name for IBM's first "supercomputer," the
7030, which was started in 1955 and completed in
1961.  The first of eight units was delivered to
the Los Alamos Scientific Laboratory and was in use
for 10 years.  STRETCH was IBM's first attempt at
building transistorized computers and was designed
to "stretch" the speed of its current vacuum tube
models by a factor of 100.

   The machine was very sophisticated for its time,
providing simultaneous execution of business
instructions with floating point arithmetic.  It
was estimated that IBM lost 40 million dollars in
developing STRETCH, but that the knowledge gained
led to huge profits with its subsequent computers.



stretch blt
An enhanced type of bitblt used for resizing video
images.  The function expands or contracts the
number of bits while moving them from main memory
to the display memory.  See bitblt.



string
(1) In programming, a contiguous set of
alphanumeric characters that does not contain
numbers used for calculations.  Names, addresses,
words and sentences are strings.  Contrast with
numeric data.

(2) Any connected set of structures, such as a
string of bits, fields or records.



string handling
The abilty to manipulate alphanumeric data (names,
addresses, text, etc.).  Typical functions include
the ability to handle arrays of strings, to left
and right align and center strings and to search
for an occurrence of text within a string.



Stringy Floppy
A tape drive for the Radio Shack TRS-80 personal
computer that used a continuous loop cartridge of
1/16" tape from a company called Exatron in
Sunnyvale, CA.  It was faster than the audio
cassettes used for data storage in the early days
of personal computing.  The company claimed it sold
a few thousand of these "tape wafers."  However,
soon after, the floppy disk became the norm.

   Why not have some fun with such a unique name.
Ask your systems people if they've seen the new
"Stringy Floppy" on the market, and watch the
puzzled expression.  Keep a straight face now!



striping
Interleaving or multiplexing data to increase
speed.  See disk striping.



stroke
(1) In printing, the weight, or thickness, of a
character.  For example, in the LaserJet, one of
the specifications of the font description is the
stroke weight from -3 to +3.

(2) In computer graphics, a pen or brush stroke or
to a vector in a vector graphics image.



stroke font
Same as vector font.



stroke weight
The thickness of lines in a font character.  The HP
LaserJet III manual defines stroke weights from
Ultra Thin (-7) to Ultra Black (+7), with Medium,
or Text, as normal (0).



stroke writer
Same as vector display.



structured analysis
Techniques developed in the late 1970s by Yourdon,
DeMarco, Gane and Sarson for applying a systematic
approach to systems analysis.  It included the use
of data flow diagrams and data modeling and
fostered the use of implementation-independent
graphical notation for documentation.



structured design
A systematic approach to program design developed
in the mid 1970s by Constantine, Yourdon, et al,
that included the use of graphical notation for
effective documentation and communication, design
guidelines and recipes to help programmers get
started.



structured programming
Techniques that impose a logical structure on the
writing of a program.  Large routines are broken
down into smaller, modular routines.  The use of
the GOTO statement is discouraged (see spaghetti
code).

   Certain programming statements are indented in
order to make loops and other program logic easier
to follow.  Structured walkthroughs, which invite
criticism from peer programmers, are also used.

   Structured languages, such as Pascal, Ada and
dBASE, force the programmer to write a structured
program.  However, unstructured languages such as
FORTRAN, COBOL and BASIC require discipline on the
part of the programmer.



structured query language
See SQL.



stub
A small software routine placed into a program that
provides a common function.  Stubs are used for a
variety of purposes.  For example, a stub might be
installed in a client machine, and a counterpart
installed in a server, where both are required to
resolve some protocol, remote procedure call (RPC)
or other interoperability requirement.



Stuffit
A Macintosh shareware program from Aladdin Systems,
Aptos, CA, that compresses files onto multiple
floppies.  A commercial version adds a scripting
language, file viewing and supports multiple
compression techniques.  It was originally
developed by Raymond Lau at age 16.



style sheet
In word processing and desktop publishing, a file
that contains layout settings for a particular
category of document.  Style sheets include such
settings as margins, tabs, headers and footers,
columns and fonts.



stylus
A pen-shaped instrument that is used to "draw"
images or point to menus.  See light pen and
digitizer tablet.



subarea node
In an SNA network, a system that contains network
controlling functions.  It refers to a host
computer or a communications controller and its
associated terminals.



subdirectory
A disk directory that is subordinate to (below)
another directory.  In order to gain access to a
subdirectory, the path must include all directories
above it.



submarining
The temporary visual loss of the moving cursor on a
slow display screen such as found on a laptop
computer.  See active matrix LCD.



submenu
An additional list of options within a menu
selection.  There can many levels of submenus.



subnet
See subnetwork.



subnetwork
A division of a network into an interconnected, but
independent, subgroup, or domain, in order to
improve performance and security.



subnotebook
A laptop computer that weighs less than four
pounds.  Subnotebooks may use an external floppy
disk to reduce weight.  If you need to exchange
data via diskettes in remote locations, this may be
inconvenient.  For features of a portable computer,
see laptop computer.



subroutine
A group of instructions that perform a specific
task.  A large subroutine is usually called a
module or procedure; a small one, a function or
macro, but all terms are used interchangeably.



subschema
Pronounced "sub-skeema."  In database management,
an individual user's partial view of the database.
The schema is the entire database.



subscript
(1) In word processing and mathematical notation, a
digit or symbol that appears below the line.
Contrast with superscript.

(2) In programming, a method for referencing data
in a table.  For example, in the table PRICETABLE,
the statement to reference a specific price in the
table might be PRICETABLE (ITEM), ITEM being the
subscript variable.  In a two-dimensional table
that includes price and discount, the statement
PRICETABLE (ITEM,DISCOUNT) could reference a
discounted price.  The relative locations of the
current ITEM and DISCOUNT are kept in two index
registers.



subset
A group of commands or functions that do not
include all the capabilities of the original
specification.  Software or hardware components
designed for the subset will also work with the
original.  However, any component designed for the
full original specification will not operate with
the subset product.  Contrast with superset.



substrate
The base material upon which integrated circuits
are built.  Silicon is the most widely used
substrate for chips.



substring
A subset of an alphanumeric field or variable.  The
substring function in a programming language is
used to extract the subset; for example, the
programming expression  substr(prodcode,4,3)
extracts characters 4, 5 and 6 out of a product
code field or variable.



subtract
In relational database, an operation that generates
a third file from all the records in one file that
are not in a second file.



suite of applications
See application suite.



SUM II
(Symantec Utilities for Macintosh)  A set of
Macintosh utilities from Symantec Corporation,
Cupertino, CA, that provides hard disk
optimization, analysis and repair and security
capabilities.



Summit
The code name for IBM's ES/9000 models.  Since
water cooled models below the 820 are re-
architected 3090 J models, the term may stay in
usage to refer to the top-end models (820, 860,
900).



Sun
(Sun Microsystems, Inc., Mountain View, CA)  A
manufacturer of network-based, high-performance
workstations founded in 1982.  Product lines
include stand-alone and networked systems, diskless
workstations and file servers that feature its
SPARC microprocessor architecture.

   Sun supports an open systems model of computing
throughout its product line that allows it to
interact in networks of computer systems from other
vendors.  Its ONC (Open Network Computing) software
is supported by over 300 vendors, and its NFS
(Network File System) software, which allows data
sharing across the network, has become an industry
standard.

   In 1991, Sun split its business into the
following wholly-owned subsidiaries:

     Sun Microsystems - Systems
     SunSoft - System software
     SunPro  - Programmer productivity tools
     SunPics - Printing and imaging
     SunConnect - Network integration
     SunExpress - Distribution





SunSoft
See Sun.



super floppy
(1) A PC 3.5" floppy disk that holds 2.88MB and is
compatible with the 1.44MB and 720KB formats.

(2) A very-high-capacity floppy disk in the 20MB
range.  See Floptical.

(3) (SuperFloppy)  A Superdrive-compatible floppy
disk for older Macintoshes from Peripheral Land,
Inc., Fremont, CA.



Super VGA
See VGA and PC display modes.



SuperCalc
A PC spreadsheet from Computer Associates.  It was
one of the first spreadsheets following in
VisiCalc's footsteps in the early 1980s.
SuperCalc5 (1988) provides 3-D capability, enhanced
graphics and can link up to 256 spreadsheets.



supercomputer
The fastest computer available.  It is typically
used for simulations in petroleum exploration and
production, structural analysis, computational
fluid dynamics, physics and chemistry, electronic
design, nuclear energy research and meteorology.
It is also used for realtime animated graphics.



superconductor
A material that has little resistance to the flow
of electricity.  Traditional superconductors
operate at -459 Fahrenheit (absolute zero).

   Thus far, the major use for superconductors,
made of alloys of niobium, is for high-powered
magnets in medical imaging machines that use
magnetic fields instead of x-rays.

   Using experimental materials, such as copper
oxides, barium, lanthanum and yttrium, IBM's Zurich
research lab in 1986 and the University of Houston
in 1987 raised the temperature of superconductivity
to -59 degrees Fahrenheit.  If superconductors can
work at reasonable temperatures, they will have a
dramatic impact on the future of computing.  See
Josephson junction.



SuperDrive
The floppy disk drive used in the Macintosh.  It
stores 1.44MB of data in its high-density format.
It also reads and writes earlier Mac 400 and 800KB
disks, as well as Apple II ProDOS, MS-DOS and OS/2
formats.



superframe
A T1 transmission format made up of 12 T1 frames
(superframe) and 24 frames (extended superframe).
See D4.



SuperKermit
See Kermit.



SuperKey
A PC keyboard macro processor from Borland that
lets users create keyboard macros, rearrange the
keyboard and encrypt data and programs.



supermini
A large-scale minicomputer.  Terminology is really
a point of view.  If you're a mini maker, your
largest machine is "super."  If you're a mainframe
maker, your smallest machine isn't worth talking
about!

   Note: Supermini is not the same as mini-
supercomputer.



superscaler
A CPU architecture that allows more than one
instruction to be executed in one clock cycle.



superscript
Any letter, digit or symbol that appears above the
line.  Contrast with subscript.



superserver
A high-speed network server with very large RAM and
disk capacity.  Superservers typically support
multiprocessing.



superset
A group of commands or functions that exceed the
capabilities of the original specification.
Software or hardware components designed for the
original specification will also operate with the
superset product.  However, components designed for
the superset will not work with the original.
Contrast with subset.



supertwist
An LCD technology that twists liquid molecules
greater than 90 in order to improve contrast and
viewing angle.  See LCD.



supervisor
Same as operating system.



supervisor call
The instruction in an application program that
switches the computer to supervisor state.



supervisor control program
The part of the operation system that always
resides in memory.  Same as kernel.



supervisor state
Typically associated with mainframes, it is a
hardware mode in which the operating system
executes instructions unavailable to an application
program; for example, I/O instructions.  Contrast
with program state.



suppliers
See hardware vendors, software vendors, vendors,
and online services.



support
(1) The assistance provided by a hardware or
software vendor in installing and maintaining its
product.

(2) Software or hardware designed to include or
work with some other software or hardware product.
For example, if a word processor "supports the
LaserJet," it can activate special features of that
printer.  If a computer "supports multiprocessing,"
it can host more than one CPU internally.  If a
development system "supports Windows," it is used
to create applications for Windows.  If a system
"supports the major databases," it provides
interfaces to those databases.



SUPRA
A relational DBMS from Cincom Systems, Inc.,
Cincinnati, OH, that runs on IBM mainframes and
VAXs.  It includes a query language and a program
that automates the database design process.



surface
In CAD, the external geometry of an object.
Surfaces are generally required for NC (numerical
control) modeling rather than wireframe or solids.



surface modeling
In CAD, a mathematical technique for representing
solid-appearing objects.  Surface modeling is a
more complex method for representing objects than
wireframe modeling, but not as sophisticated as
solid modeling.

   Although surface and solid models can appear the
same on screen, they are quite different.  Surface
models cannot be sliced open as can solid models.
In addition, in surface modeling, the object can be
geometrically incorrect; whereas, in solid
modeling, it must be correct.



surface mount
A circuit board packaging technique in which the
leads (pins) on the chips and components are
soldered on top of the board, not through it.
Boards can be smaller and built faster.



surfing
Scanning online material, such as databases, news
clips and forums.  The term originated from
"channel surfing," the rapid changing of TV
channels to find something of interest.



surge
See power surge.



surge protector
A device that protects a computer from excessive
voltage (spikes and power surges) in the power
line.  See voltage regulator and UPS.



surge suppressor
Same as surge protector.



suspend and resume
To stop an operation and restart where you left
off.  In portable computers, the hard disk is
turned off, and the CPU is made to idle at its
slowest speed.  All open applications are retained
in memory.



SV
(Scientific Visualization)  See visualization.



SVC
(Switched Virtual Circuit)  A Network connection
from sender to recipient that is established at the
time the transmission is required.  This is what
occurs in a switched public network.  Contrast with
PVC.



SVGA
(Super VGA)  See VGA.



SVID
(System V Interface Definition)  An AT&T
specification for the UNIX System V operating
system.  SVID Release 3 specifies the interface for
UNIX System V Release 4.



SVR4
See System V Release 4.0.



swap file
A disk file used to temporarily save a program or
part of a program running in memory.  See Windows
swap file.



swapping
Replacing one segment of a program in memory with
another and restoring it back to the original when
required.  In virtual memory systems, it is called
paging.



switch
(1) A mechanical or electronic device that directs
the flow of electrical or optical signals from one
side to the other.  Switches with multiple input
and output ports such as a PBX are able to route
traffic."  See data switch and transistor.

   With regard to a simple on/off switch,
remember...

         Open is "off."  Closed is "on."

(2) In programming, a bit or byte used to keep
track of something.  Sometimes refers to a branch
in a program.

(3) A modifier of a command.  See DOS switch.



switch-to-computer
To integrate voice telephone and database access.
For example, in customer service applications,
using telephone services, such as automatic number
identification (ANI) and automatic call
distribution (ACD), an incoming call can retrieve
and route the customer's file to the next available
human agent.



Switched 56
A digital service at 56Kbits/sec provided by the
local telephone companies and long distance
carriers.  It works like the dial-up telephone
system, only for digital data.  You pay a monthly
charge plus so much per minute of digital traffic.
The rates are similar to voice calls on the analog
network.  For connection, a DSU/CSU is used instead
of a modem.



switched Ethernet
An Ethernet network that runs through a high-speed
switch.  Switched Ethernet is easily installed in
an existing 10BaseT network, because the network
adapters (NICs) in each machine are still used.
The Ethernet hub is changed to an Ethernet switch,
and the medium is no longer shared, rather there is
dedicated bandwidth between any two stations.  The
switch, which is capable of handling hundreds of
megabits per second, allows each user the full
Ethernet bandwidth of 10 Mbps to another node.  See
FDSE.



switched line
In communications, a link that is established in a
switched network, such as the international dial-up
telephone system, a Switched 56 digital line or
ISDN.



switched multimegabit data service
See SMDS.



switched network
(1) The international dial-up telephone system.

(2) A network in which a temporary connection is
established from one point to another for either
the duration of the session (circuit switching) or
for the transmission of one or more packets of data
(packet switching).



switched virtual circuit
See SVC.



switching hub
A device that acts as a central switch or PBX,
connecting one line to another.  In a local area
network (LAN), a switching hub gives any two
stations on the network the full bandwidth of the
line.  Contrast with shared media LAN, in which all
stations share the bandwidth of a common
transmission path.  See hub.



SX
See 386SX, 486SX and LaserJet.



Sybase database
See SQL Server.



Sybase System
A family of SQL development tools from Sybase,
Inc., Emeryville, CA, that includes SQL Server, SQL
Toolset (design, development and control) and
Client/Services Interfaces (distributed database
architecture).  See SQL Server.



SYLK file
(SYmbolic LinK file)  A spreadsheet file format
originating with Multiplan that is used by a number
of spreadsheet programs.



Symantec
(Symantec Corporation, Cupertino, CA)  A software
company founded in 1982 by Dr. Gary Hendrix.  It
was acquired by Gordon Eubanks in 1984 and released
its Q&A file manager the following year.  In 1990,
it merged with Peter Norton Computing, Inc.,
developer of the well-known Norton Utilities and
Norton Desktop programs.  Since then, it has
acquired more than a dozen other software
companies, including Central Point Software, maker
of PC Tools, and Zortech, developer of of C++
compilers.



symbol
In data compression, a unit of data (byte, floating
point number, spoken word, etc.) that is treated
independently.



symbol set
In printing, a group of symbols that are extensions
to standard characters for use in a particular
country or specific application.  Symbol sets
provide codes for the non-standard upper half of
the ASCII character set.



symbolic language
(1) A programming language that uses symbols, or
mnemonics, for expressing operations and operands.
All modern programming languages are symbolic
languages.

(2) A language that manipulates symbols rather than
numbers.  See list processing.



symmetric multiprocessing
See SMP.



Symphony
An Integrated software package for PCs from Lotus
that includes word processing, database management,
speadsheet, business graphics, communications and a
macro language.



sync character
In synchronous communications systems, a special
character transmitted to synchronize timing.



sync generator
A device that supplies synchronization signals to a
series of cameras to keep them all in phase.



synchronous
(1) A sequence of fixed or concurrent events.  See
synchronous transmission.

(2) Completing the current I/O operation before the
next one is started.

(3) In SCSI, the transfer of data without immediate
acknowledgment of each byte.

(4) Contrast with asynchronous.



synchronous protocol
A communications protocol that controls a
synchronous transmission, such as bisync, SDLC and
HDLC.  Contrast with asynchronous protocol.



synchronous transmission
The transmission of data in which both stations are
synchronized.  Codes are sent from the transmitting
station to the receiving station to establish the
synchronization, and data is then transmitted in
continuous streams.

   Modems that transmit at 1200 bps and higher
often convert the asynchronous signals from a
computer's serial port into synchronous
transmission over the transmission line.  Contrast
with asynchronous transmission.



SynOptics
See Bay Networks.



syntax
The rules governing the structure of a language
statement.  It specifies how words and symbols are
put together to form a phrase.



syntax error
An error that occurs when a program cannot
understand the command that has been entered.  See
parse.



synthesize
To create a whole or complete unit from parts or
components.



synthesizer
A device that generates sound by creating waveforms
electronically (FM synthesis) or from stored
samples of musical instruments (wave table
synthesis).  See MIDI and speech synthesis.



sysgen
(SYStem GENeration)  The installation of a new or
revised operating system.  It includes selecting
the appropriate utility programs and identifying
the peripheral devices and storage capacities of
the system the operating system will be
controlling.



sysop
(SYStem OPerator) Pronounced "siss-op."  A person
who runs an online communications system or
bulletin board.  The sysop may also act as mediator
for system conferences.



Sysplex
IBM System/390 multiprocessing.  The Sysplex Timer
external clock is used to synchronize time-of-day
clocks in multiple processors.  If failure occurs
in a multiprocessor complex, precise transaction
time stamps are required for accurate rollback and
recovery.



SysReq key
(SYStem REQuest key)  A keyboard key on a terminal
keyboard that is used to get the attention of the
central computer.  The key exists on PC keyboards,
but is rarely used by applications.



system
(1) A group of related components that interact to
perform a task.

(2) A computer system is made up of the CPU,
operating system and peripheral devices.

(3) An information system is made up of the
database, all the data entry, update, query and
report programs and manual and machine procedures.

(4) "The system" often refers to the operating
system.



System 2000
(1) A hierarchical, network and relational DBMS
from the SAS Institute, Cary, NC, that runs on IBM,
CDC and Unisys computers.  It has been integrated
into the SAS System.

(2) See FTS 2000.



System/3
A batch-oriented minicomputer from IBM.  Introduced
in 1969, it introduced a new punched card about
half the size of previous ones.  With the addition
of the Communications Control Program (CCP), it
could handle interactive terminals.



System/32
A batch-oriented minicomputer from IBM.  Introduced
in 1975, it provided a single terminal for operator
use.  It was superseded by the System/34, which
could run System/32 applications in a special mode.



System/34
A multiuser, multitasking minicomputer from IBM,
introduced in 1977.  The typical system had from a
handful to a dozen terminals and could run
System/32 programs in a special mode.  Most large
System/34 users migrated to the System/38, while
small users migrated to the System/36.



System/36
A multiuser, multitasking minicomputer from IBM
that was introduced in 1983.  It superseded the
System/34 and is mostly compatible with it.
System/34 programs run in the System/36 after
recompilation.  The typical system supports from a
handful to a couple of dozen terminals.

   Although superseded by the AS/400, System/36
applications have to be recompiled to run on it.
As a result, as of late 1994, a large number of
System/36s still remain in use.  With the
announcement of the AS/400 Advanced System/36,
which runs System/36 applications natively, it is
expected that System/36s will finally begin to fade
into history.



System/360
IBM's first family of computer systems introduced
in 1964.  It was the first time in history that a
complete line of computers was announced at one
time.  Although considerable enhancements have been
made, much of the 360 architecture is still carried
over in current-day IBM mainframes.  See IBM
mainframes.



System/370
The mainframe product line introduced in 1970 by
IBM (superseding System/360), which added virtual
memory and other enhancements.  Subsequent series
include the 303x, 43xx, 308x, 309x and 9370, all
370-architecture machines.  The 370 architecture
was brought down to the PC level in 1983 with the
PC XT/370, and then again in 1989 with the VM/SP
Technical Workstation.  See IBM mainframes.



System/38
A minicomputer from IBM that includes an operating
system with an integrated relational database
management system.  Introduced in 1978, it was an
advanced departure from previous System/3x
computers.  The typical system handles from a dozen
to several dozen terminals.  It has been superseded
by the AS/400.



System/390
The mainframe product line introduced in 1990 by
IBM (superseding System/370) that features ESA/390
architecture and operating systems, ES/9000
hardware (18 models introduced), ESCON fiber optic
channels, Sysplex multiprocessing and SystemView.



System/3x
Refers to IBM System/34, System/36 and System/38
midrange computers.



System 7
(1) A major upgrade of the Macintosh operating
system (1991).  It includes virtual memory,
increased memory addressing, hot links (Publish &
Subscribe), multitasking (MultiFinder no longer
optional), TrueType fonts and a variety of
enhancements to the user interface.

(2) (System/7) A sensor-based minicomputer from IBM
introduced in 1970 and used for process control.
It was superseded by the Series/1.



System 7 Pro
Extensions to the System 7 operating system from
Apple that include PowerTalk communications, the
AppleScript scripting language and QuickTime for
sound, movies and animation.



System/88
A family of fault-tolerant midrange computers from
IBM used for online transaction processing.  Uses
the System/88 virtual memory and System/88 FTX
(Fault Tolerant UNIX) operating systems.  Includes
4579 and 4576 multiprocessor series and 4593 entry-
level models.



system administrator
A person who manages a multiuser computer system.
Responsibilities are similar to that of a network
administrator.  A system administrator would
perform systems programmer activities with regard
to the operating system and other network control
programs.



System Application Architecture
See SAA.



system BIOS
On a PC, a part of the operating system that is
coded into a memory chip on the motherboard.  The
system BIOS has traditionally been stored in a ROM
chip, which cannot be updated and must be replaced
if new functions are required.  Increasingly, the
system BIOS is stored in a flash memory chip, which
can be updated in place on the motherboard.  It is
expected that all BIOSs that are stored in chips
will eventually be updatable in place.  See ROM
BIOS.



system board
A printed circuit board that contains the primary
CPU.  In a personal computer, it is also called the
motherboard.



system development cycle
The sequence of events in the development of an
information system (application), which requires
mutual effort on the part of user and technical
staff.

   1. SYSTEMS ANALYSIS & DESIGN
       feasibility study
       general design
       prototyping
       detail design
       functional specifications

   2. USER SIGN OFF

   3. PROGRAMMING
       design
       coding
       testing

   4. IMPLEMENTATION
       training
       conversion
       installation

   5. USER ACCEPTANCE



system development methodology
The formal documentation for the phases of the
system development cycle.  It defines the precise
objectives for each phase and the results required
from a phase before the next one can begin.  It may
include specialized forms for preparing the
documentation describing each phase.



system disk
A hard or floppy disk that contains part or all of
the operating system or other control program.



system failure
A hardware or operating system malfunction.



system file
A machine language file that is part of the
operating system or other control program.  It may
also refer to a configuration file used by such
programs.



system folder
The operating system folder in the Macintosh that
contains the System, Finder and MultiFinder,
printer drivers, fonts, desk accessories, INITs and
cdevs.



system font
The primary font used by the operating system or
other control program to display messages and menus
unless otherwise directed.



system image
The current contents of memory, which includes the
operating system and running programs.



system level
An operation that is performed by the operating
system or some other control program.



system life cycle
The useful life of an information system.  Its
length depends on the nature and volatility of the
business, as well as the software development tools
used to generate the databases and applications.
Eventually, an information system that is patched
over and over no longer is structurally sound
enough to be expanded.

   Tools like DBMSs allow for changes more readily,
but increased transaction volumes can negate the
effectiveness of the original software later on.



system management
See systems management.



System Management Interrupt
See SMI.



System Management Mode
See SMM.



system memory
The memory used by the operating system.



System Network Architecture
See SNA.



System Object Model
See SOM.



system program
A component of system software.



system prompt
An on-screen symbol that indicates the operating
system is ready for a command.  See DOS prompt.



System Resources
See Windows memory limitations.



system software
Programs used to control the computer and develop
and run application programs.  It includes
operating systems, TP monitors, network operating
systems and database managers.  Contrast with
application program.

   The following diagram shows the flow between
system software and application software residing
in memory in a multiuser computer.  The operating
system (OS), TP monitor, database manager and
interpreter are considered system software.  The
applications and interactive DBMS query and edit
would be considered application software.


 to/from terminals (RAM)ͻ
Ŀ   Ŀ   
 Comm.      TP Monitor (Multiuser)      
 Access        
 Methods       Ŀ Ŀ 
Ĵ      Application Application  
               in COBOL,   in DBMS      
               Pascal, C,  language.    
               assembly    Paradox,     
               lang., etc. dBASE, etc.  
                 
   OS    ......................... .......
         .Ŀ   Ŀ .
         .Interactive:     Interpreter .
         .enter, edit,      .
         .query, reports                .
Ĵ.                .
 Disk    .  Ŀ.
 Access         Database manager       .
 Methods .  .
...............DBMS ................
 to/from disk ͼ



   Following are the major categories of system
software.  See application software for a list of
major application software categories.


      Operating System
      Manages the computer system.  Provides file,
      task and job management.  All application
      programs "talk to" the operating system.

      DOS, Windows, OS/2, UNIX, VMS, MVS, VM and
      Windows NT are examples.

      Database Management System (DBMS)
      Manages the storage, retrieval, security and
      integrity of the database.  A DBMS may
      provide interactive data entry, updating,
      query and reporting or rely entirely on the
      application program for such functions.  The
      DBMS may reside in a mainframe or in a file
      server in a client/server architecture.
      Popular DBMSs support the SQL query language.
      Many DBMSs provide a complete programming
      language for application development.

      Examples of popular mainframe and
      client/server DBMSs are DB2, Oracle, Sybase,
      Rdb, Informix, Ingres and Progress.  dBASE
      and Paradox are used for many PC
      applications.

      TP Monitor
      Mainframe/midrange program that distributes
      input from multiple terminals to the
      appropriate application.  This functions is
      also provided in LAN operating systems.

      CICS is widely used in IBM mainframes, and
      Tuxedo is widely used in UNIX systems.

      Network Operating System
      Manage traffic and security between client
      workstations and file servers in a network.
      Examples are NetWare, LAN Manager, LAN
      Server, VINES, NFS (UNIX), Windows NT and
      LANtastic.

      Communications Protocol
      Set of rules, formats and functions for
      sending data across the network.  There are
      many protocol layers starting at the top
      application layer to the bottom physical
      layer (see OSI model).

      Popular transport protocols are NetBIOS,
      NetBEUI, IPX/SPX and TCP/IP.  Popular data
      link protocols, or access methods, used to
      transmit data from point to point are
      Ethernet, Token Ring, SDLC and RS-232.

      Messaging Protocol
      Set of rules, formats and functions for
      sending, storing and forwarding e-mail in a
      network.  The major messaging protocols are
      SNADS, MHS, SMTP, X.400 and the proprietary
      protocols used in cc:Mail and Microsoft Mail.

      Driver
      Software that supports a peripheral device,
      such as a display adapter or CD-ROM.  The
      driver contains the detailed machine language
      necessary to activate all functions in the
      device.  The operating system commands the
      driver, which in turn commands the hardware
      device.

      BIOS
      (Basic Input/Output System)  The part of the
      operating system that manages the essential
      peripherals such as the keyboard, monitor and
      disks.  It also contains internal functions
      such as the system timer and realtime clock.
      See ROM BIOS.

      Programming Language
      Translate source language into machine
      language using assemblers, compilers,
      interpreters and application generators.  All
      system software and application software must
      be programmed in a programming language and
      turned into machine language for execution.

      Examples of programming languages are
      assembly language, BASIC, FORTRAN, C, C++,
      Pascal, dBASE, Paradox, Visual Basic and
      COBOL.


  See application software for a list of major
application software categories.




system test
Running a complete system for testing purposes.
See unit test.



system time/date
The on-going time of day in the computer, which is
maintained by a battery when the computer is turned
off.  It is used to time stamp all newly-created
files and activate time-dependent processes.



System V Interface Definition
See SVID.



System V Release 4.0
A unified version of UNIX released in 1989.  See
UNIX.



System V.4
See System V Release 4.0.



SYSTEM.INI
(SYStem INItialization)  A Windows configuration
file that describes the current state of the
computer system environment.  It contains hundreds
of entries and is read by Windows on startup.  It
identifies such things as the drivers in the
system, how DOS applications are handled and
provides immense detail about internal Windows
settings.

   The information in SYSTEM.INI is updated by
Windows when you change various defaults; however,
in order to tweak system performance, the file can
be edited with a text editor or a word processor
that imports ASCII files.

   Most of the time, users do not deal with
SYSTEM.INI; however, on occasion, a line in the 386
Enhanced section ([386Enh]) may have to be
modified.  Sometimes an EMMExclude= statement is
added or changed to exclude a section of upper
memory used by a new peripheral from the general
pool of memory that Windows uses.  WIN.INI is
another major configuration file read by Windows at
startup.  See WIN.INI.



Systemantics
An insightful book on the systems process by John
Gall (1977).  The following is copied with
permission from Random House.


         A Concise Summary of the Field of
               General Systemantics
Systems are seductive.  They promise to do a hard
job faster, better, and more easily than you could
do it by yourself.  But if you set up a system, you
are likely to find your time and effort now being
consumed in the care and feeding of the system
itself.  New problems are created by its very
presence.  Once set up, it won't go away, it grows
and encroaches.  It begins to do strange and
wonderful things.  Breaks down in ways you never
thought possible.  It kicks back, gets in the way,
and opposes its own proper function.  Your own
perspective becomes distorted by being in the
system.  You become anxious and push on it to make
it work.  Eventually you come to believe that the
misbegotten product it so grudgingly delivers is
what you really wanted all the time.  At that point
encroachment has become complete...

    you have become absorbed...

      you are now a systems person!



systems
A general term for the department, people or work
involved in systems analysis & design activities.



systems administrator
See system administrator.



systems analysis & design
The examination of a problem and the creation of
its solution.  Systems analysis is effective when
all sides of the problem are reviewed.  Systems
design is most effective when more than one
solution can be proposed.  The plans for the care
and feeding of a new system are as important as the
problems they solve.  See system development cycle
and Systemantics.



systems analyst
The person responsible for the development of an
information system.  They design and modify systems
by turning user requirements into a set of
functional specifications, which are the blueprint
of the system.  They design the database or help
design it if data administrators are available.
They develop the manual and machine procedures and
the detailed processing specs for each data entry,
update, query and report program in the system.

   Systems analysts are the architects, as well as
the project leaders, of an information system.  It
is their job to develop solutions to user's
problems, determine the technical and operational
feasibility of their solutions, as well as estimate
the costs to develop and implement them.

   They develop prototypes of the system along with
the users, so that the final specifications are
examples of screens and reports that have been
carefully reviewed.  Experienced analysts leave no
doubt in users' minds as to what is being
developed, and they insist that all responsible
users review and sign off on every detail.

   Systems analysts require a balanced mix of
business and technical knowledge, interviewing and
analytical skills, as well as a good understanding
of human behavior.  See Systemantics.



systems disk
A disk pack or disk drive reserved only for system
software, which includes the operating system,
assemblers, compilers and other utility and control
programs.



systems engineer
Often a vendor title for persons involved in
consulting and pre-sales activities related to
computers.  See systems analyst, systems
programmer, programmer analyst and application
programmer.



systems house
An organization that develops customized software
and/or turnkey systems for customers.  Contrast
with software house, which develops software
packages for sale to the general public.  Both
terms are used synonymously.



systems integration
Making diverse components work together.  See NASI.



systems integrator
An individual or organization that builds systems
from a variety of diverse components.  With
increasing complexity of technology, more customers
want complete solutions to information problems,
requiring hardware, software and networking
expertise in a multivendor environment.  See OEM,
VAR and NASI.



systems management
(1) The management of systems development, which
includes systems analysis & design, application
development and implementation.  See system
development cycle.

(2) Software that manages computer systems in an
enterprise, which may include any and all of the
following functions: software distribution, version
control, backup & recovery, printer spooling, job
scheduling, virus protection and performance and
capacity planning.  Network management may be an
integrated component of systems management.



Systems Management Server
See SMS.



systems program
See system program and system software.



systems programmer
(1) In the IS department of a large organization, a
technical expert on some or all of the computer's
system software (operating systems, networks,
DBMSs, etc.).  They are responsible for the
efficient performance of the computer systems.

   They usually don't write programs, but perform a
lot of technical tasks that integrate vendors'
software.  They also act as technical advisors to
systems analysts, application programmers and
operations personnel.  For example, they would know
whether additional tasks could be added to the
computer and would recommend conversion to a new
operating or database system in order to optimize
performance.

   In mainframe environments, there is one systems
programmer for about 10 or more application
programmers, and systems programmers generally have
considerably higher salaries than application
programmers.  In smaller environments, users rely
on vendors or consultants for systems programming
assistance.  In fact, end users are actually
performing systems programmer functions when they
install new software or hardware on their own
personal computers.  See system administrator.

(2) In a computer hardware or software
organization, a person who designs and writes
system software.  In this case, a systems
programmer is a programmer in the traditional
sense.



Systems Programming Language
See SPL.



SystemView
An IBM architecture for computer systems management
introduced with System/390 that provides an
enterprise-wide approach for controlling multiple
systems and networks.  It will be implemented in
stages through the 1990s.  NetView is a major
component.



systolic array
An array of processing elements (typically
multiplier-accumulator chips) in a pipeline
structure that is used for applications such as
image and signal processing and fluid dynamics.
The "systolic," coined by H. T. Kung of Carnegie-
Mellon, refers to the rhythmic transfer of data
through the pipeline like blood flowing through the
vascular system.



SYZYGY
Pronounced "SIZE-uh-gee."  PC workgroup software
from Information Research Corporation,
Charlottesville, VA.  Used for coordinating
schedules, resources and budgets for group projects
and includes e-mail and a calendar with to-do and
activity blists.



T
See tera.



T-byte
See terabyte.



T-carrier
A digital transmission service from a common
carrier.  Introduced by AT&T in 1983 as a voice
service, its use for data has grown steadily.

   T-carrier service requires multiplexors at both
ends that merge the various signals together for
transmission and split them at the destination.
Multiplexors analyze the traffic load and vary
channel speeds for optimum transmission.  See DS.



T1
A 1.544 megabit T-carrier channel that can handle
24 voice or data channels at 64 Kbits/sec.  The
standard T1 frame is 193 bits long, which holds 24
8-bit voice samples and one synchronization bit.
8,000 frames are transmitted per second.  See DS,
D4 and ESF.



T2
A 6.312 megabit T-carrier channel that can handle
96 voice or data channels at 64 Kbits/sec.  See DS.



T3
A 44.736 megabit T-carrier channel that can handle
672 voice or data channels at 64 Kbits/sec.  T3
requires fiber optic cable.  See DS.



tab
(1) To move the cursor on a display screen or the
print head on a printer to a specified column (tab
stop).  There are both horizontal and vertical tab
characters in the ASCII character set.  See tab
stop.

(2) A small flap used for identification and quick
access that projects out from a page of paper or
file folder.  Its electronic equivalent on screen
can be clicked to launch a program or function or
to access a record or document.



tab character
A control character in a document that represents
movement to the next tab stop.  In the ASCII
character set, a horizontal tab is ASCII 9, and a
vertical tab is ASCII 11.  See ASCII chart.



tab delimited
A text format that uses tab characters as
separators between fields.  Unlike comma delimited
files, alphanumeric data is not surrounded by
quotes.



tab key
A keyboard key that moves the cursor to the next
tab stop.



tab stop
A location on a horizontal line that has been
defined to begin a column of text.  Tab stops are
necessary for multiple columns when proportional
fonts are used.  Pressing the space bar several
times to move to the next column provides proper
alignment only with monospaced characters.  With
proportional fonts, although the space bar moves a
fixed amount, the varying widths of text in one
column cause misalignment to the column on the
right.

   With typewriters, tab stops are mechanical
gizmos that halt the movement of the carriage.  In
word processing, they are column numbers that are
maintained by the software.



tabbing
See tab.



table
(1) In programming, a collection of adjacent
fields.  Also called an array, a table contains
data that is either constant within the program or
is called in when the program is run.  See decision
table.

(2) In a relational database, the same as a file; a
collection of records.



table lookup
Searching for data in a table, commonly used in
data entry validation and any operation that must
match an item of data with a known set of values.



table view
A screen display of several items or records in
rows and columns.  Contrast with form view.



tablet
See digitizer tablet.



tabular form
Same as table view with respect to printed output.



tabulate
(1) To arrange data into a columnar format.

(2) To sum and print totals.



tabulating equipment
Punched card machines, including keypunches,
sorters, collators, interpreters, reproducers,
calculators and tabulators.



tabulator
A punched card accounting machine that prints and
calculates totals.



Tadpole
(Tadpole Technology, Inc., Austin, TX)  Founded in
1988, it is a wholly-owned subsidiary of the
British company, Tadpole Technology plc, which was
founded in 1984.  Until 1992, its focus was board
level products and related software to OEM
customers.  In 1992, it began the introduction of
workstation-class notebooks, starting with the Sun-
compatible SPARCbook.  Tadpole developed IBM's
RS/6000 notebook, and Tadpole's Alpha- and Pentium-
based notebooks are expected in 1995.



tag
(1) A set of bits or characters that identifies
various conditions about data in a file and is
often found in the header records of such files.

(2) A name (label, mnemonic) assigned to a data
structure, such as a field, file, paragraph or
other object.

(3) The key field in a record.

(4) A brass pin on a terminal block that is
connected to a wire by soldering or wire wrapping.



tag RAM
A specialized bank of static RAM used to hold
addresses.  When a stored address matches an input
address, a signal is output to perform a function.
It is used with hardware devices such as CPU caches
to keep track of which memory addresses are stored
in the cache.



tag sort
A sorting procedure in which the key fields are
sorted first to create the correct order, and then
the actual data records are placed into that order.



TalAE
See Taligent.



Taligent
(Taligent, Inc., Cupertino, CA)  A joint venture of
IBM, Apple and HP involved in developing a next-
generation operating system.  Apple's object-
oriented operating system, code named Pink, and
Carnegie Mellon's Mach are the basis of the
product.

   The complete operating system, TalOS, is
expected in 1996.  In the meantime, the Taligent
Application Environment (TalAE), a set of object-
oriented application frameworks for AIX, OS/2, HP-
UX and the PowerMac are expected in 1995.  Also
planned for 1995 is the Taligent Development
Environment (TalDE), which contains compilers and
development tools for the target environments.



talk-off
An unintentional command activation when a human
voice generates the same tone as a control signal.



TalOS
See Taligent.



Tandem
(Tandem Computers Inc., Cupertino, CA)  A
manufacturer of fault-tolerant computers founded in
1974 by James Treybig.  It was the first company to
address the transaction processing (OLTP) market
for online reservations and financial transfers by
providing computers designed from the ground up for
fault-tolerant operation.

   Tandem's flagship fault-tolerant product is its
MIPS-based Himalaya series which runs the NonStop
Kernel operating system, compatible with Tandem's
Guardian OS.  The Himalaya holds the world's record
for number of transactions processed per second.
Tandem also offers its Integrity line of MIPS-based
servers that run NonStop-UX (UNIX).



tandem processors
Two processors hooked together in a multiprocessor
environment.



Tandy
(Tandy Corporation, Ft. Worth, TX)  A manufacturer
of PCs and electronics that started as a family
leather business in 1919.  In 1963, it acquired the
nine Radio Shack stores in Boston.  Today, it has
over 7,000 company-owned stores and franchises.

   In 1977, it introduced one of the first personal
computers, the TRS-80 Model I.  Tandy's Model 100
and 200 lightweight portables were also inspiration
to the laptop generation.  Its first computers were
proprietary, and its initial PCs were non-standard.
However, starting with the Model 1000 in 1984,
Tandy offered a full line of IBM-compatible PCs.

   In 1993, Tandy sold its PC manufacturing
facilities to AST and began to eliminate using the
Tandy brand name on its machines.  Radio Shack
stores currently offer a variety of machines from
AST, IBM and others.



tap
In communications, a connection onto the main
transmission medium of a local area network.  See
transceiver.



tape
See magnetic tape and paper tape.



tape backup
The use of magnetic tape for storing duplicate
copies of hard disk files.  QIC drives are the most
widely used, but DAT and 8mm (Exabyte) formats are
gaining ground.  See QIC, DDS (3), DATA/DAT, D/CAS
and Exabyte.



tape drive
A physical unit that holds, reads and writes the
magnetic tape.  See magnetic tape.



tape dump
A printout of tape contents without any report
formatting.



tape mark
A control code used to indicate the end of a tape
file.



tape transport
The mechanical part of a tape drive.



TAPI
(Telephony API)  A programming interface from
Microsoft and Intel that is part of Microsoft's
WOSA architecture.  It allows Windows client
applications to access voice services on a server.
TAPI is designed to provide interoperability
between PCs and telephone equipment, including
phone systems and PBXs.  See WOSA.



tar
A UNIX utility for archiving files, often used in
conjunction with "compress."



Targa
A raster graphics file format developed by
Truevision, Inc., Indianapolis, IN.  It uses the
.TGA file extension and handles 16-, 24- and 32-bit
color.  It is also the trade name of a line of
video graphics boards used in high-resolution
imaging.



target computer
The computer into which a program is loaded and
run.  Contrast with source computer.  See cross
assembler/compiler.



target directory
The directory into which data is being sent.
Contrast with source directory.



target disk
The disk onto which data is recorded.  Contrast
with source disk.



target drive
The drive containing the disk or tape onto which
data is recorded.  Contrast with source drive.



target language
The language resulting from a translation process
such as assembling or compiling.  Contrast with
source language.



target machine
Same as target computer.



tariff
A schedule of rates for common carrier services.



task
An independent running program.  See multitasking.



task management
The part of the operating system that controls the
running of one or more programs (tasks) within the
computer at the same time.



task swapping
Switching between two applications by copying the
current running program to disk or other high-speed
storage device (auxiliary memory, EMS, etc.) and
loading another program into that program space.



task switching
Switching between active applications.  See context
switching.



TAXI
(Transparent Asynchronous Transmitter/Receiver
Interface)  A 100 Mbps/sec ATM transmission
standard defined by the ATM Forum.



Tazz
Short for Tasmanian Devil, Tazz is a code name for
a Windows 95 telephone application from Microsoft.
It uses Microsoft's TAPI interface and a third-
party speech-recognition engine.  It will control
new multimedia modems that handle both voice and
data.  Tazz is expected to be introduced after the
release of Windows 95.




TB, Tb
See terabyte and terabit.



Tbit
See terabit.



Tbits/sec
(TeraBITS per SECond)  Trillion bits per second.



TBps, Tbps
(TeraBytes Per Second, TeraBits Per Second)
Trillion bytes per second.  Trillion bits per
second.



TByte
See terabyte.



Tbytes/sec
(TeraBYTES per SECond)  Trillion bytes per second.



TC
See true color.



TCAM
(TeleCommunications Access Method)  IBM
communications software widely used to transfer
data between mainframes and 3270 terminals.  See
access method.



TCM
(1) (Trellis-Coded Modulation/Viterbi Decoding)  A
technique that adds forward error correction to a
modulation scheme by adding an additional bit to
each baud.  TCM is used with QAM modulation, for
example.

(2) (Thermal Conduction Module)  An IBM circuit
packaging technique that seals chips, boards and
components into a module that serves as a heat
sink.  TCMs are mostly water cooled, although some
are air cooled.



TCO
Refers to the Swedish Confederation of Professional
Employees, which has set stringent standards for
devices that emit radiation.  See MPR II.



TCP/IP
(Transmission Control Protocol/Internet Protocol)
A communications protocol developed under contract
from the U.S. Department of Defense to internetwork
dissimilar systems.  It is a de facto UNIX
standard, but is supported on almost all computer
systems.  TCP/IP is the protocol of the Internet.

   File Transfer Protocol (FTP) and Simple Mail
Transfer Protocol (SMTP) provide file transfer and
e-mail.  The Telnet protocol provides terminal
emulation for all types of computers in the
network.  TCP controls data transfer.  IP provides
the routing.

   The combination of TCP/IP, NFS and NIS comprise
the primary networking components of UNIX.

   The following chart compares the TCP/IP layers
with the Department of Defense and Open System
Interconnection models.


   TCP/IP          DOD            OSI
Ŀ Ŀ Ŀ
Application              Application 
                         Ĵ
(FTP, SMTP    Process    Presentation
  Telnet)                Ĵ
                           Session   
Ĵ Ĵ Ĵ
 Transport  Host to Host  Transport  
   (TCP)                             
Ĵ Ĵ Ĵ
 Internet     Internet     Network   
   (IP)                              
Ĵ Ĵ Ĵ
  Network                 Data link  
 Interface    Network    Ĵ
 (IEEE 802     Access      Physical  
   X.25)                             
  





TCP/IP stack
An implementation of the TCP/IP protocol.  Network
architectures designed in layers, such as TCP/IP,
OSI and SNA, are called stacks.



TCSEC
See NCSC.



TCU
(Transmission Control Unit)  A communications
control unit controlled by the computer that does
not execute internally stored programs.  Contrast
with front end processor, which executes its own
instructions.



TDM
(Time Division Multiplexing)  A technique that
interleaves several low-speed signals into one
high-speed transmission.  For example, if A, B & C
are three digital signals of 1,000 bps each, they
can be mixed into one 3,000 bps as follows:
AABBCCAABBCCAABBCC.  The receiving end divides the
single stream back into its original signals.

   TDM is the technology used in T-carrier service
(DS0, DS1, etc.), which are the leased lines common
in wide area networks (WANs).  Contrast with FDM.
See baseband.



TDMA
(Time Division Multiple Access)  A cellular
telephone technology that triples the capacity of
the original analog method (FDMA).  It divides each
channel into three subchannels providing service to
three users instead of one.  See FDMA, CDMA and
CDPD.



tear-off menu
An on-screen menu or palette that can be moved off
of its primary position and relocated to any part
of the screen.



tech support
Technical assistance from the hardware manufacturer
or software publisher.  Unless you have a simple,
straightforward question, in order to get help from
a tech support representative, place your telephone
call while you are at your computer.  Intermittent
problems are very difficult to resolve.  If you
cannot recreate the problem on screen, there may be
very little a tech support person can do to help
you.



tech writer
A person who is responsible for writing
documentation for a hardware or software product.



Technical Office Protocol
See TOP.



telco
(TELephone COmpany)  A company that provides
telephone services.  It generally refers to the
local telephone companies rather than the long-
distance suppliers.



tele
Operations performed remotely or by telephone.



telecom
(TELECOMmunications)  Telecom generally refers to
the telephone industry.  See telecommunications.



telecommunications
Communicating information, including data, text,
pictures, voice and video over long distance.  See
communications.



Telecommunications Industry Association
See TIA.



telecommunity
A society in which information can be transmitted
or received freely between all members without
technical incompatibilities.



telecommuting
Working at home and communicating with the office
by electronic means.



teleconferencing
(1) Video teleconferencing, or videoconferencing,
is having a TV conference with several people at
the same time.  It is provided by video cameras and
monitors inhouse or in a public conferencing
center.

   Full-screen, full-motion video at 30 frames per
second requires a high-bandwidth network.  However,
due to improving compression techniques, it is
expected that a videoconferencing window will
become commonplace on desktop computers within the
next five years.

(2) Audio teleconferencing is having a telephone
conversation with several people at the same time.
It is provided by a conference function on a PBX or
multiline telephone or by the telephone companies.

(3) Computer teleconferencing is having a
simultaneous conference with several people at the
same time at their computers.  It is provided by
software in a host computer or BBS.



telecopying
(long distance copying)  The formal term for fax.



telefax
The european term for a fax machine.



telegraph
A low-speed communications device that transmits up
to approximately 150 bps.  Telegraph grade lines,
stemming from the days of Morse code, can't
transmit a voice conversation.



telemanagement
Management of an organization's telephone systems,
which includes maintaining and ordering new
equipment and monitoring the expenses for all
telephone calls.



telemarketing
Selling over the telephone.



telematics
The convergence of telecommunications and
information processing.



telemetry
Transmitting data captured by instrumentation and
measuring devices to a remote station where it is
recorded and analyzed.  For example, data from a
weather satellite is telemetered to earth.



Telenet
A value-added, packet switching network that
enables many varieties of terminals and computers
to exchange data.  It is a subsidiary of US Sprint.
See also Telnet.



telephone channel
See voice grade.



telephone wiring
See twisted pair.



telephony
The science of converting sound into electrical
signals, transmitting it within cables or via radio
and reconverting it back into sound.



Telephony API
See TAPI.



Telephony Server NLM
A NetWare NLM that provides an interface between a
NetWare server and a PBX.  The physical connection
is made by cabling the PBX to a card in the server.
The NLM provides an open programming interface that
allows PBX manufacturers to write drivers for their
products.

   The first implementation of this is AT&T's
Definity PBX, which physically connects via an AT&T
card in the NetWare server and allows all network
users with AT&T phones to have access to the PBX
through their PCs.



Telephony Services API
See TSAPI.



teleprinter
A typewriter-like terminal with a keyboard and
built-in printer, often a portable unit.  Contrast
with video terminal.



teleprocessing
An early IBM term for data communications.  It
means "long distance" processing.



teleprocessing monitor
See TP monitor.



Telescript
A programming language and software for
communications from General Magic.  It embeds
intelligence in e-mail and other applications
allowing them to cooperate with one another and
allows messages to move intelligently through
diverse public and private networks.  Telescript
can be added to existing and future operating
systems.  See Magic Cap.



teleservices
(TELEphone SERVICES)  An umbrella term for products
and services that integrate telephones and
computers.  See audiotex.



Teletex
See Telex.



teletext
A broadcasting service that transmits text to a TV
set that has a teletext decoder.  It uses the
vertical blanking interval of the TV signal (black
line between frames when vertical hold is not
adjusted) to transmit about a hundred frames.  See
videotex.



Teletype
The trade name of Teletype Corporation, which
refers to a variety of teleprinters used for
communications.  The Teletype was one of the first
communications terminals in the U.S.



teletype interface
See teletype mode.



teletype mode
Line-at-a-time output like a typewriter.  Contrast
with full-screen mode.



teletypewriter
A low-speed teleprinter, often abbreviated "TTY."


televaulting
Continuous transmitting of data to vaults for
backup purposes.  The term was coined by TeleVault
Technology Inc.



Telex
An international dial-up communications service
that uses teleprinters and transmits Baudot code at
50 bps (66 words/minute).  In the U.S., it is
administered by Western Union, which in 1971
purchased the Bell System's TWX service and
connected it to the Telex network.

   In the early 1980s, a new service called Teletex
was initiated that provides higher speeds and upper
and lowercase text to subscribers using intelligent
terminals and personal computers.  Group 3 fax
machines quickly supplanted Telex transmission.



TeLink
An Xmodem protocol with batch file transfer
designed for the Fido BBS.  It sends file name,
date and size in the first block.



Telnet
A terminal emulation protocol commonly used on the
Internet.  It allows a user to log onto and run a
program from a remote terminal or computer.  Telnet
was originally developed for ARPAnet and is part of
the TCP/IP communications protocol.

   Although most computers on the Internet require
users to have an established account and password,
there are many that allow public access to certain
programs, typically, search utilities, such as
Archie or WAIS.  See also Telenet.



Telon
See CA-Telon.



TEMPEST
Security against external radiation from data
processing equipment.  Equipment and cables that
meet TEMPEST requirements have extra shielding in
order to prevent data signals from escaping and
being picked up by unauthorized listeners.



template
(1) A plastic or stiff paper form that is placed
over the function keys on a keyboard to identify
their use.

(2) The programmatic and descriptive part of a
programmable application; for example, a
spreadsheet that contains only descriptions and
formulas or a HyperCard stack that contains only
programming and backgrounds.  When the template is
filled with data, it becomes a working application.



temporary font
A soft font that remains in the printer's memory
until the printer is reset manually or by software.
Contrast with permanent font.



ter
Third version.



tera
Trillion.  Abbreviated "T."  It often refers to the
precise value 1,099,511,627,776 since computer
specifications are usually binary numbers.  See
binary values and space/time.



terabit
One trillion bits.  Also Tb, Tbit and T-bit.  See
tera and space/time.



terabyte
One trillion bytes.  Also TB, Tbyte and T-byte.
See tera and space/time.



teraflops
(tera FLoating point OPerations per Second)  One
trillion floating point operations per second.



terminal
(1) An I/O device for a computer that usually has a
keyboard for input and a video screen or printer
for output.

(2) An input device, such as a scanner, video
camera or punched card reader.

(3) An output device in a network, such as a
monitor, printer or card punch.

(4) A connector used to attach a wire.



terminal emulation
Using a computer to simulate the type of terminal
required to gain access to another computer.  See
virtual terminal.



terminal mode
An operating mode that causes the computer to act
like a terminal; ready to transmit typed-in
keystrokes and ready to receive transmitted data.



terminal server
A computer or controller used to connect multiple
terminals to a network or host computer.



terminal session
The time in which a user is working at a terminal.



terminal strip
An insulated bar that contains a set of screws to
which wires are attached.



terminate and stay resident
See TSR.



terminator
(1) A character that ends a string of alphanumeric
characters.

(2) A hardware component that is connected to the
last peripheral device in a series or the last node
in a network.



terrestrial link
A communications line that travels on, near or
below ground.  Contrast with satellite link.



test automation software
Software used to test new revisions of software by
automatically entering a predefined set of commands
and inputs.



test data
A set of data created for testing new or revised
programs.  It should be developed by the user as
well as the programmer and must contain a sample of
every category of valid data as well as many
invalid conditions.



testing
Running new or revised programs to determine if
they process all data properly.  See test data.

   For testing as it pertains to professional
certification, see CCP, NetWare certification and
Microsoft Certified Professional.



TeX
A typesetting language used in a variety of
typesetting environments.  It uses embedded codes
within the text of the document to initiate changes
in layout including the ability to describe
elaborate scientific formulas.



Texas Instruments
See TI.



text
Words, sentences and paragraphs.  Contrast with
data, which are defined units, such as name and
amount due.  Text may also refer to alphanumeric
data, such as name and address, to distinguish it
from numeric data, such as quantity and dollar
amounts.  A page of text takes about 2,000 to 4,000
bytes.  See text field.



text based
Also called character based, the display of text
and graphics as a fixed set of predefined
characters.  For example, 25 rows of 80 columns.
Contrast with graphics based.



text box
An on-screen rectangular frame into which you type
text.  Text boxes are used to add text in a drawing
or paint program.  The flexibility of the text box
is determined by the software.  Sometimes you can
keep on typing and the box expands to meet your
input.  Other times, you have to go into a
different mode to widen the frame, then go back to
typing in more text.



text editing
The ability to change text by adding, deleting and
rearranging letters, words, sentences and
paragraphs.



text editor
Software used to create and edit files that contain
only text; for example, batch files, address lists
and source language programs.  Text editors produce
raw ASCII or EBCDIC text files, and unlike word
processors, do not usually provide word wrap or
formatting (underline, boldface, fonts, etc.).

   Editors designed for writing source code may
provide automatic indention and multiple windows
into the same file.  They may also display the
reserved words of a particular programming language
in boldface or in a different font, but they do not
embed format codes in the file.  See DOS Editor.



text entry
Entering alphanumeric text characters into the
computer.  It implies typing the characters on a
keyboard.  See data entry.



text field
A data structure that holds alphanumeric data, such
as name and address.  If a text field holds large,
or unlimited, amounts of text, it may be called a
memo field.  Contrast with numeric field.



text file
A file that contains only text characters.  See
ASCII file.  Contrast with graphics file and binary
file.



text management
The creation, storage and retrieval of text.  It
implies flexible retrieval capabilities that can
search for text based on a variety of criteria.
Although a word processor manages text, it usually
has limited retrieval capabilities.



text mode
(1) A screen display mode that displays only text
and not graphics.

(2) A program mode that allows text to be entered
and edited.



text-to-speech
Converting text into voice output using speech
synthesis techniques.  Although initially used by
the blind to listen to written material, it is now
used extensively to convey financial data and other
information via telephone for everyone.



texture mapping
In computer graphics, the creation of a special
surface.  With algorithms, all kinds of textures
can be produced: the rough skin of an orange, the
metallic surface of a can and the irregularity of a
brick.  It can also be done by electronically
wrapping a secondary image around an object.



TFT
(Thin Film Transistor)  See thin film.



TFT LCD
(Thin Film Transistor LCD)  See LCD.



TFTP
(Trivial File Transfer Protocol)  A version of the
TCP/IP FTP protocol that has no directory or
password capability.



TGA
See Targa.



the Web
See Worldwide Web.



thermal dye transfer
Also called dye sublimation and thermal dye
diffusion, this is a printing process similar to
thermal wax transfer except that dyes are used
instead of ink.  The printhead heats the ribbon
causing the dye to turn from a solid to a gas and
condense on special coated paper.  The more heat,
the denser the image.  Unlike other printing
techniques which simulate shades of colors by
dithering, thermal dye transfer creates
photographic quality color.



thermal printer
A low-cost, low- to medium-resolution non-impact
printer that uses heat-sensitive paper.  Where the
heated pins of the print head touch the paper, the
paper darkens.  See printer.



thermal wax transfer
A printing process that transfers a waxlike ink
onto paper.  For example, in a color printer, a
mylar ribbon is used that contains several hundred
repeating sets of full pages of black, cyan,
magenta and yellow ink.  A sheet of paper is
pressed against each color and passed by a line of
heating elements that transfers the dots, or
pixels, of ink onto the paper.



thick Ethernet
See 10Base5 and Ethernet.



thick film
A layer of magnetic, semiconductor or metallic
material that is thicker than the microscopic
layers of the transistors on a chip.  For example,
metallic thick films are silk screened onto the
ceramic base of hybrid microcircuits.  Contrast
with thin film.



ThickNet
See 10Base5 and Ethernet.



ThickWire
See 10Base5 and Ethernet.



thimble printer
A letter quality printer similar to a daisy wheel
printer.  Instead of a wheel, characters are formed
facing out and around the rim of a thimble-shaped
cup.  For example, the NEC Spinwriters are thimble
printers.



thin Ethernet
See 10Base2 and Ethernet.



thin film
A microscopically thin layer of semiconductor or
magnetic material that is deposited onto a metal,
ceramic or semiconductor base.  For example, the
layers that make up a chip and the surface coating
on high-density magnetic disks are called thin
films.



thin film head
A read/write head for high-density disks that is
made from thin layers of a conducting film
deposited onto a nickel-iron core.



ThinkPad
A family of IBM notebook computers that include
large screens and a built-in TrackPoint pointing
device located between the G, H and B keys on the
keyboard.  See IBM PC for ThinkPad specifications.



ThinNet
See 10Base2 and Ethernet.



ThinWire
See 10Base2 and Ethernet.



third-generation computer
A computer that uses integrated circuits, disk
storage and online terminals.  The third generation
started roughly in 1964 with the IBM System/360.



third-generation language
Also known as a 3GL, it refers to a high-level
programming language such as FORTRAN, COBOL, BASIC,
Pascal and C.  It is a step above assembly language
and a step below fourth-generation language (4GL).
For an example of the difference between a 3GL and
a 4GL, see fourth-generation language.



third normal form
See normalization.



THOR
(Tandy High-intensity Optical Recorder)  An
erasable audio CD recorder from Tandy that was
scheduled for the early 1990s, but has yet to come
to fruition.



thrashing
Excessive paging in a virtual memory computer.  If
programs are not written to run in a virtual memory
environment, the operating system may spend
excessive amounts of time swapping program pages in
and out of the disk.

   The goal of virtual memory is to increase
internal memory capacity, not to waste time
reloading program segments over and over.  However,
a well-designed virtual memory system tracks page
usage and prevents the most-often-used modules from
being swapped to disk.



thread
One transaction or message in a multithreaded
system.



threading
See multithreading.



three-state logic element
An electronic component that provides three
possible outputs: off, low voltage and high
voltage.



three-tier client/server
A three-way interaction in a client/server
environment, in which the user interface is stored
in the client, the bulk of the business application
logic is stored in one or more servers, and the
data is stored in a database server.  See two-tier
client/server.



throughput
The speed with which a computer processes data.  It
is a combination of internal processing speed,
peripheral speeds (I/O) and the efficiency of the
operating system and other system software all
working together.



thumb
See elevator.



thumbnail
A miniature representation of a page or image.  A
thumbnail program may be stand-alone or part of a
desktop publishing or graphics program.  Thumbnails
take considerable time to generate, but provide a
convenient way to browse through multiple images
before retrieving the one you need.  Programs often
let you click on the thumbnail to retrieve it.



thunk
In PCs, to execute the instructions required to
switch between segmented addressing of memory and
flat addressing.



THz
(TeraHertZ)  One trillion cycles per second.



TI
(Texas Instruments, Inc., Dallas, TX)  A leading
semiconductor manufacturer founded in 1930 as
Geophysical Service, Inc., to provide services to
the petroleum industry.  During the war, GSI
manufactured electronics for the Navy and later
added them to its product line.

   In 1951, GSI was renamed Texas Instruments and
soon after entered the semiconductor business.  TI
was the first to commercialize the silicon
transistor, pocket radio, integrated circuit, hand-
held calculator, single-chip computer and the LISP
chip.

   In the early 1980s, TI sold a large number of
its low-priced 99/4a home computers.  It later
introduced desktop PCs, but today offers only a
line of notebook PCs.

   With 1993 revenues of $8.5 billion, TI's
strength is integrated circuits.  However, it also
creates computer systems for AI applications,
composite metals, electrical control products and
consumer electronics, including its well-known line
of calculators and educational math and reading
machines.



TI-RPC
(Transport-Independent-Remote Procedure Call)  A
functions from Sun for executing procedures on
remote computers.  It is operating system and
network independent and allows the development of
distributed applications in multivendor
environments.



TIA
(Telecommunications Industry Association)  A
membership organization founded in 1988 that sets
standards for physical level interfaces (RS-232,
RS-422, etc.) as well as cellular radio.  It was
originally an EIA working group that was spun off
and merged with the USTSA (U.S. Telecommunications
Suppliers Association), sponsors of the annual
Supercomm conference.  TIA is involved with setting
telecommunications standards worldwide.  Address:
2001 Pennsylvania Ave., N.W., Washington, DC 20006,
202/457-4912.



TIA/EIA-232
See RS-232.



TIC
(Token Ring Interface Card)  A TLA for a Token Ring
NIC (network interface card).



tickler
A manual or automatic system for reminding users of
scheduled events or tasks.  It is used in PIMs,
contact management systems and scheduling and
calendar systems.



TIES
(Time-Independent Escape Sequence)  A modem escape
sequence that uses three pluses like the Hayes
sequence, but does not require a pause before and
after them.  If a valid AT command code and a
return follows the +++, it is considered a
legitimate command.  See Hayes Smartmodem.



TIF
A file extension used for TIFF files; for example,
image1.tif.  See TIFF.



TIFF
(Tagged Image File Format)  A widely-used raster
graphics file format developed by Aldus and
Microsoft that handles monochrome, gray scale, 8-
and 24-bit color.  Since 1986, there have been six
versions of TIFF.  It uses several compression
methods: LZW provides ratios of about 1.5:1 to 2:1.
Ratios of 10:1 to 20:1 are possible for documents
with lots of white space using ITU-TSS Group III &
IV compression methods (fax).  See JPEG.



TIGA
(Texas Instruments Graphics Architecture)  A
graphics standard from TI that provides a
resolution-independent interface between a program
and the graphics coprocessor.  See 34010.



Tiger
Code name for Microsoft's multimedia video-on-
demand software that runs on Windows NT.  It is
expected in late 1994 or early 1995.



tightly coupled
Refers to two or more computers linked together and
dependent on each other.  One computer may control
the other, or both computers may monitor each
other.  For example, a database machine is tightly
coupled to the main processor.  Two computers tied
together for multiprocessing are tightly coupled.
Contrast with loosely coupled, such as personal
computers in a LAN.



tiled
A display of objects side by side; for example,
tiled windows cannot be overlapped on top of each
other.



timbre
A quality of sound that distinguishes one voice or
musical instrument from another.  For example, MIDI
synthesizers are multi-timbral, meaning that they
can play multiple instruments simultaneously.



time base generator
An electronic clock that creates its own timing
signals for synchronization and measurement
purposes.



time-division multiplexing
See TDM.



Time Sharing Option
See TSO.



time slice
A fixed interval of time allotted to each user or
program in a multitasking or timesharing system.



time slot
Continuously repeating interval of time or a time
period in which two devices are able to
interconnect.



timer interrupt
An interrupt generated by an internal clock.  See
interrupt.



timesharing
A multiuser computer environment that lets users
initiate their own sessions and access selected
databases as required, such as when using online
services.  A system that serves many users, but for
only one application, is technically not
timesharing.



timing clock
See clock.



timing signals
Electrical pulses generated in the processor or in
external devices in order to synchronize computer
operations.  The main timing signal comes from the
computer's clock, which provides a frequency that
can be divided into many slower cycles.  Other
timing signals may come from a timesharing or
realtime clock.

   In disk drives, timing signals for reading and
writing are generated by holes or marks on one of
the platters, or by the way the digital data is
actually recorded.



tin
(Threaded Internet Newsreader)  A newsreader for
reading the messages in a newsgroup on the
Internet.  See USENET.



Tiny BASIC
A subset of BASIC that has been used in first
generation personal computers with limited memory.



TIRIS
(Texas Instruments Registration and Identification
System)  An RF/ID system from TI that uses a
3.6x29mm cylindrical tag.  Reading can be done from
as far as 40 inches away.



TLA
(Three Letter Acronym)  The epitome of acronyms!
While two-, four- and five-letter acronyms exist,
there are more three-letter acronyms.  Obviously,
three words to describe a concept or product is the
most popular.



TLI
(Transport Level Interface)  A common interface for
transport services (layer 4 of the OSI model).  It
provides a common language to a transport protocol
and allows client/server applications to be used in
different networking environments.

   Instead of directly calling NetWare's SPX for
example, the application calls the TLI library.
Thus, any transport protocol that is TLI compliant
(SPX, TCP, etc.) can provide transport services to
that application.  TLI is part of UNIX System V.
It is also supported by NetWare 3.x.  See STREAMS.



TM/1
(Tables Manager/1)  An analytical database engine
for DOS and Windows from Sinper Corporation,
Warren, NJ, that allows data to be viewed in up to
eight dimensions.  The data is kept in a database,
and the formulas are kept in a spreadsheet, which
is used as a viewer into the database.  TM/1 makes
it easy to display different slices of the data,
and it is designed to import and cross tab large
amounts of data.

   TM/1 Pespectives is a spreadsheet add-in that
lets Excel or 1-2-3 provide the user interface to a
TM/1 database.  Spreadsheet Connector is the server
version.



TN
(Twisted Nematic)  The first LCD technology that
twisted liquid crystal molecules 90 between
polarizers.  TN displays require bright ambient
light and are still used for low-cost applications.
See LCD.



TNT
(1) (Transparent Network Transport)  Services from
the telephone companies and common carriers that
provide Ethernet and Token Ring transmission over
MANs and WANs.

(2) DOS extender from Phar Lap Software that allows
DOS applications to use various Win32 features,
including memory allocation, DLLs and threads.

(3) Code name for Apple's second generation of
PowerMacs expected in early 1995.  It includes
improved video and uses the PCI bus.



TOF
(Top Of Form)  The beginning of a physical paper
form.  To position paper in many printers, the
printer is turned offline, the forms are aligned
properly and the TOF button is pressed.



toggle
To alternate back and forth between two states.



token bus network
A LAN access method that uses the token passing
technology.  Stations are logically connected in a
ring but are physically connected by a common bus.
All tokens are broadcast to every station in the
network, but only the station with the destination
address responds.  After transmitting a maximum
amount of data, the token is passed to the next
logical station in the ring.  The MAP factory
automation protocol uses this method.  See token
passing.



token passing
A communications network access method that uses a
continuously repeating frame (the token) that is
transmitted onto the network by the controlling
computer.  When a terminal or computer wants to
send a message, it waits for an empty token.  When
it finds one, it fills it with the address of the
destination station and some or all of its message.

   Every computer and terminal on the network
constantly monitors the passing tokens to determine
if it is a recipient of a message, in which case it
"grabs" the message and resets the token status to
empty.  Token passing uses bus and ring topologies
(see token bus network and token ring network).



Token Ring adapter
A Token Ring network adapter.  See network adapter.



token ring network
(1) A LAN access method that uses the token passing
technology in a physical ring.  Each station in the
network passes the token on to the station next to
it.  Token Ring and FDDI LANs use the token ring
access method.  See token passing.

(2) (Token Ring Network)  A LAN access method from
IBM that conforms to the IEEE 802.5 token ring
standard.  It connects up to 255 nodes in a star
topology at 4 or 16 Mbits/sec.  All stations
connect to a central wiring hub called the Multi-
station Access Unit, or MAU, using special twisted
wire cable.  The central hub makes it easier to
troubleshoot failures.

   Token Ring is a data link protocol and functions
at the data link and physical levels of the OSI
model (1 and 2).  See data link protocol and OSI
model.



TokenTalk
Software for the Macintosh from Apple that
accompanies its TokenTalk NB board and adapts the
Mac to Token Ring Networks.



toner
An electrically charged ink used in copy machines
and laser printers.  It adheres to an invisible
image that has been charged with the opposite
polarity onto a plate or drum or onto the paper
itself.



tool
(1) An on-screen function in an interactive
program; for example, a line draw, circle draw or
paintbrush option in a graphics program.

(2) A program used for software development or
system maintenance.  Virtually any program or
utility that helps programmers or users develop
applications or maintain their computers can be
called a tool.  Visual programming products,
editors, debuggers and libraries of specialized
routines are examples.

   In client/server development, tools are
application generators, GUI builders, 4GLs, 3GLs
and any supporting software.



tool palette
A collection of on-screen functions, typically
graphics related, that are grouped in a menu
structure for interactive selection.



toolbar
A row or column of on-screen buttons used to
activate various functions of the application.  The
bar is typically movable so it can be placed close
to the object being worked on in order to quickly
switch modes and options.  Toolbars can often be
customized allowing buttons to be added and deleted
as necessary for a user's own requirements.



ToolBook
An application development system for Windows from
Asymetrix Corporation, Bellevue, WA, that uses a
"page and book" metaphor analogous to HyperCard's
"card and stack."  Its OpenScript language is
similar to HyperTalk.



toolbox
See toolkit and toolbar.



toolkit
A set of software routines that allow a program to
be written for and work in a particular
environment.  The routines are called by the
application program to perform various functions,
for example, to display a menu or draw a graphic
element.



TOP
(Technical Office Protocol)  A communications
protocol for office systems from Boeing Computer
Services.  It uses the Ethernet access method and
is often used in conjunction with MAP, the factory
automation protocol developed by GM.  TOP is used
in the front office, and MAP is used on the factory
floor.  TOP uses the CSMA/CD access method, while
MAP uses token bus.



top of file
The beginning of a file.  In a word processing
file, it is the first character in the document.
In a data file, it is either the first record in
the file or the first record in the index.  For
example, in a dBASE file that is indexed on name,
goto top might go to physical record #608 if record
#608 is AARDVARK.



topdown design
A design technique that starts with the highest
level of an idea and works its way down to the
lowest level of detail.



topdown programming
A programming design and documentation technique
that imposes a hierarchical structure on the design
of the program.  See structured programming.



topics
See industry topics and lessons.



topology
(1) In a communications network, the pattern of
interconnection between nodes; for example, a bus,
ring or star configuration.

(2) In a parallel processing architecture, the
interconnection between processors; for example, a
bus, grid, hypercube or Butterfly Switch
configuration.



TOPS
(1) A multiuser, multitasking, timesharing, virtual
memory operating system from Digital that runs on
its PDP-6, DECsystem 10 and DECsystem 20 series.

(2) (Transparent OPerating System)  A peer-to-peer
LAN from Sitka Corporation, Alameda, CA, that uses
the LocalTalk access method and connects Apple
computers, PCs and Sun workstations.  Its Flashcard
plugs LocalTalk capability into PCs.



TOPVIEW
IBM's first PC windowing environment.  It never
caught on.



TOTAL
An early network DBMS from Cincom Systems that ran
on a variety of minis and mainframes.



total bypass
Bypassing local and long distance telephone lines
by using satellite communications.



touch screen
A touch-sensitive display screen that uses a clear
panel over on the screen surface.  The panel is a
matrix of cells that transmit pressure information
to the software.



tower
(1) A floor-standing cabinet taller than it is
wide.  Desktop computers can be made into towers by
turning them on their side and inserting them into
a floor-mounted base.

(2) (Tower)  Series of UNIX-based single and
multiprocessor computer systems from NCR that use
the Motorola 68000 family of CPUs.



TP monitor
(TeleProcessing monitor or Transaction Processing
monitor)  A control program that manages the
transfer of data between multiple local and remote
terminals and the application programs that serve
them.  It may also include programs that format the
terminal screens and validate the data entered.

   In a distributed client/server environment, a TP
monitor provides integrity by ensuring that
transactions do not get lost or damaged.  It may be
placed in a separate machine and used to balance
the load between clients and various application
servers and database servers.  It is also used to
create a high availability system by switching a
failed transaction to another machine.

   Examples of popular TP monitors are CICS, a
veteran TP monitor used on IBM mainframes and the
UNIX-based Tuxedo and Encina products.



TP-PMD
(Twisted Pair-Physical Medium Dependent)  An ANSI
standard for an FDDI network that uses UTP instead
of optical fiber.  See CDDI.



TP0-TP4
(Transport Protocol Class 0 to Class 4)  The grades
of OSI transport layers from least to most complete
and specific.  TP4 is a full connection-oriented
transport protocol.



TPA
(Transient Program Area)  See transient area.



tpi
(Tracks Per Inch)  The measurement of the density
of tracks recorded on a disk or drum.



TPS
(1) (Transactions Per Second)  The number of
transactions processed within one second.

(2) (Transaction Processing System)  Originally
used as an acronym for such a system, it now refers
to the measurement of the system (#1 above).



tpsA
(TPS A-Benchmark)  A transaction per second
benchmark as specified by the Transaction
Processing Council.  Performance is rated as the
number of TPS as well as the cost of the system per
single TPS; for example, 100 tpsA and $8,100 per
tpsA.



trace
See autotrace.



track
A storage channel on disk or tape.  On disks,
tracks are concentric circles (hard and floppy
disks) or spirals (CDs and videodiscs).  On tapes,
they are parallel lines.  Their format is
determined by the specific drive they are used in.
On magnetic devices, bits are recorded as reversals
of polarity in the magnetic surface.  On CDs, bits
are recorded as physical pits under a clear,
protective layer.  See magnetic disk.



trackball
An input device used in video games and as a mouse
alternative.  It is a stationary unit that contains
a movable ball rotated with the fingers or palm
and, correspondingly, moves the cursor on screen.



tractor feed
A mechanism that provides fast movement of paper
forms through a printer.  It contains pins on
tractors that engage the paper through perforated
holes in its left and right borders.  Contrast with
sheet feeder.



Tradacoms
A European EDI standard developed by the Article
Numbering Association.  See X12 and EDIFACT.



trade shows
See PC EXPO, COMDEX and Computex.



trailer
In communications, a code or set of codes that make
up the last part of a transmitted message.  See
trailer label.



trailer label
The last record in a tape file.  May contain number
of records, hash totals and other ID.



train printer
A line printer mechanism similar to a chain
printer, but uses unconnected type slugs that ride
in a track rather than a connected chain of type.
The slugs are pushed around the track by engaging
with a drive gear at one end.  Slugs and track come
as a replaceable cartridge.



training
(1) Teaching the details of a subject.  With regard
to software, training provides instruction for each
command and function in an application.  Contrast
with education.

(2) In communications, the process by which two
modems determine the correct protocols and
transmission speeds to use.

(3) In voice recognition systems, the recording of
the user's voice in order to provide samples and
patterns for recognizing that voice.



transaction
An activity or request.  Orders, purchases,
changes, additions and deletions are typical
business transactions stored in the computer.
Queries and other requests are also transactions,
but are usually just acted upon and not saved.
Transaction volume is a major factor in figuring
computer system size and speed.



transaction file
A collection of transaction records.  The data in
transaction files is used to update the master
files, which contain the subjects of the
organization.  Transaction files also serve as
audit trails and are usually transferred from
online disks to the data library after some period
of time.

   As optical disks become more economical,
transaction files will remain online in the
computer so that an organization's history will be
immediately available for ad hoc queries.  See
information system.

   Following are the kinds of fields that make up a
typical transaction record in a business
information system.  There can be many more fields
depending on the organization.  The "key" fields
below are the ones that are generally indexed for
fast matching against the master record.  The
account number is usually the primary key, but name
may also be used as a primary key.  See master file
for examples of typical master records.


       EMPLOYEE PAYROLL RECORD
  key  Employee account number
       Today's date
       Hours worked

       ORDER RECORD
  key  Customer account number
       Today's date
       Quantity
       Product number

       PAYMENT RECORD
  key  Customer number
       Today's date
       Invoice number
       Amount paid
       Check number

       PURCHASE ORDER
  key  Purchase order number
       Today's date
       Department
       Authorizing agent
       Vendor account number
       Quantity
       Product number
       Due date
       Total cost

       WAREHOUSE RECEIPT
  key  Purchase order number
  key  Invoice number
       Today's date
       Quantity
       Product number





transaction monitor
See TP monitor.



transaction processing
Processing transactions as they are received by the
computer.  Also called online or realtime systems,
transaction processing means that master files are
updated as soon as transactions are entered at
terminals or received over communications lines.

   If you save receipts in a shoebox and add them
up at the end of the year for taxes, that's batch
processing.  However, if you buy something and
immediately add the amount to a running total,
that's transaction processing.

   Organizations increasingly rely on computers to
keep everything up-to-date all the time.  A manager
might need to know how many items are left on the
shelf, what the latest price of a stock is or what
the value of a financial portfolio is at any given
moment.

   Transaction processing is often called online
transaction processing, or OLTP.  The OLTP market
is a demanding one.  If a business depends on
computers for its day-to-day operations, the
computers must stay up and running during business
hours.  See mission critical, industrial strength
and fault tolerant.



transceiver
A transmitter and receiver of analog or digital
signals. It comes in many forms; for example, a
transponder or network adapter.



transcribe
To copy data from one medium to another; for
example, from one source document to another, or
from a source document to the computer.  It often
implies a change of format or codes.



transducer
A device that converts one energy into another; for
example, a read/write head converts magnetic energy
into electrical energy and vice versa.  In process
control applications, it is used to convert
pressure into an electrical reading.



transfer
To send data over a computer channel or bus.
"Transfer" generally applies to transmission within
the computer system, and "transmit" refers to
transmission outside the computer over a line or
network.

   Transfers are actually copies, since the data is
in both locations at the end of the transfer.
Input, output and move instructions activate data
transfers in the computer.



transfer protocol
See file transfer protocol.



transfer rate
Also called data rate, the transmission speed of a
communications or computer channel.  Transfer rates
are measured in bits or bytes per second.



transfer time
The time it takes to transmit or move data from one
place to another.  It is the time interval between
starting the transfer and the completion of the
transfer.



transformer
A device that changes AC voltage.  Also called a
power adapter.  It is made of steel laminations
wrapped with two coils of wire.  The coil ratio
derives the voltage change.  For example, if the
input coil has 1,000 windings, and the output has
100, 120 volts is changed to 12.  In order to
create direct current (DC), the output is passed
through a rectifier.



transient
A malfunction that occurs at random intervals; for
example, a rapid fluctuation of voltage in a power
line or a memory cell that intermittently fails.



transient area
An area in memory used to hold application programs
for processing.  The bulk of a computer's main
memory is used as a transient area.



transient state
The exact point at which a device changes modes,
for example, from transmit to receive or from 0 to
1.



transistor
A semiconductor device used to amplify a signal or
open and close a circuit.  In a computer, it
functions as an electronic switch.  In its normal
state, it is non-conductive.  When voltage is
applied at the gate, it becomes conductive and
current flows from source to drain.

   Transistors, resistors, capacitors and diodes,
make up logic gates.  Logic gates make up circuits,
and circuits make up electronic systems.

            Source  Gate  Drain
                       
                    
                
              
                     
                  Switch

      Conceptual View of A Transistor





transistor transistor logic
See TTL.



translate
(1) To change one language into another; for
example, assemblers, compilers and interpreters
translate source language into machine language.

(2) In computer graphics, to move an image on
screen without rotating it.

(3) In telecommunictions, to change the frequencies
of a band of signals.



TransLISP PLUS
A version of LISP for PCs from Solution Systems,
Inc., Wellesley, MA.  It provides an interface to
Microsoft C that allows a C routine to be added to
the LISP library as a function.



transmission
The transfer of data over a communications channel.



transmission channel
A path between two nodes in a network.  It may
refer to the physical cable, the signal transmitted
within the cable or to a subchannel within a
carrier frequency.  In radio and TV, it refers to
the assigned carrier frequency.



transmission control unit
See TCU.



transmit
To send data over a communications line.  See
transfer.



transmitter
A device that generates signals.  Contrast with
receiver.



transparent
Refers to a change in hardware or software that,
after installation, causes no noticeable change in
operation.



transparent bridging
A communications protocol in which the stations are
unaware of bridges in the network.  Ethernet uses
this method.  Contrast with source routing.



transponder
A receiver/transmitter on a communications
satellite.  It receives a microwave signal from
earth (uplink), amplifies it and retransmits it
back to earth at a different frequency (downlink).
A satellite has several transponders.



transport layer
See transport protocol.



Transport Level Interface
See TLI.



transport protocol
A communications protocol responsible for
establishing a connection and ensuring that all
data has arrived safely.  It is defined in layer 4
of the OSI model.  Often, the term transport
protocol implies transport services, which includes
the lower level data link protocol that moves
packets from one node to another.  See OSI model
and transport services.



transport services
The collective functions of layers 1 through 4 of
the OSI model.



transputer
(TRANSistor comPUTER)  A computer that contains a
CPU, memory and communications capability on a
single chip.  Chips are strung together in
hypercube or grid-like patterns to create large
parallel processing machines, used in scientific,
realtime control and AI applications.



trap
To test for a particular condition in a running
program; for example, to "trap an interrupt" means
to wait for a particular interrupt to occur and
then execute a corresponding routine.  An error
trap tests for an error condition and provides a
recovery routine.  A debugging trap waits for the
execution of a particular instruction in order to
stop the program and analyze the status of the
system at that moment.



trapdoor
A secret way of gaining access to a program or
online service.  Trapdoors are built into the
software by the original programmer as a way of
gaining special access to particular functions.
For example, a trapdoor built into a BBS program
would allow access to any BBS computer running that
software.



trash can
An icon of a garbage can used for deleting files.
The icon of a file is dragged to the trash can and
released.  In the Mac, the trash can is also used
to eject the floppy disk.



trashware
Software that is so poorly designed that it winds
up in the garbage can.



tree
A hierarchical structure.  See directory tree.



Trellis-coded modulation
See TCM.



trends
See hot topics.



trichromatic
In computer graphics, the use of red, green and
blue to create all the colors in the spectrum.



trigger
A mechanism that initiates an action when an event
occurs such as reaching a certain time or date or
upon receiving some type of input.  A trigger
generally causes a program routine to be executed.

   In a database management system (DBMS), it is an
SQL procedure that is executed when a record is
added or deleted.  It is used to maintain
referential integrity in the database.  A trigger
may also execute a stored procedure.  Triggers and
stored procedures are built into DBMSs used in
client/server environments.  See intelligent
database.



trillion
One thousand times one billion or 10 to the 12th
power.  See tera and picosecond.



Trilogy
A company founded in 1979 by Gene Amdahl to
commercialize wafer scale integration and build
supercomputers.  It raised a quarter of a billion
dollars, the largest startup funding in history,
but could not create its 2.5" superchip.  In 1984,
it abandoned supercomputer development and later
the superchip project.  In 1985, Trilogy acquired
Elxsi Corporation, a manufacturer of VAX-compatible
systems, and eventually merged itself into Elxsi.



triple precision
The use of three computer words to hold a number
used for calculation, providing an enormous amount
of arithmetic precision.



triple twist
A supertwist variation that twists crystals to 260
for improved clarity.  See LCD.



troff
(Typesetting RunOFF)  A UNIX utility that formats
documents for typesetters and laser printers.
Using a text editor, troff codes are embedded into
the text and the troff command converts the
document into the required output.  See nroff.



Trojan horse
A program routine that invades a computer system by
being secretly attached to a valid program that
will be downloaded into the computer.  It may be
used to locate password information, or it may
alter an existing program to make it easier to gain
access to it.  A virus is a Trojan horse that
continues to infect programs over and over.



TRON
(The Realtime Operating System Nucleus)  An
advanced realtime computer architecture and
operating system under development by Japanese
universities and corporations.  Its goal is a
common architecture and user interface from the
smallest consumer appliance to the largest
supercomputer.  TRON-based intelligent cars and
houses are under research.

   CTRON (Central TRON) is an OSI-compliant
communications system for network file servers;
BTRON (Business TRON) for accounting applications;
ITRON (Industrial TRON) for intelligent machinery;
MTRON (Macro TRON) for intelligent objects and
networks (housing and urban development); ITRON
(Micro ITRON) runs on 8-bit computers for home
appliances.  Address: P.O.Box 23990, Tempe, AZ
85285.



TRS
(Tandy Radio Shack)  An early Tandy trade name.  In
1977, the TRS-80 was one of the three first
personal computers.  TRS-DOS was its operating
system.  See personal computer.  Also see TSR.



True BASIC
An ANSI-standard structured-programming version of
BASIC for the PC, Mac and Amiga from True BASIC,
Inc., West Lebanon, NH.  Developed in 1984 by
BASIC's creators, John Kemeny and Thomas Kurtz, it
includes many enhancements over original BASIC.  It
comes in both interpreter and compiler form.



true color
(1) The ability to generate 16,777,216 colors (24-
bit color).  See high color.

(2) The ability to generate photo-realistic color
images (requires 24-bit color minimum).



TrueImage
An enhanced PostScript interpreter from Microsoft
that prints PostScript Type 1 and TrueType fonts.



TrueType
A scalable font technology that renders fonts for
both the printer and the screen.  Originally
developed by Apple, it was enhanced jointly by
Apple and Microsoft.  TrueType fonts are used in
Windows, starting with Windows 3.1, as well as in
the Mac System 7 operating system.

   Unlike PostScript, in which the algorithms are
maintained in the rasterizing engine, each TrueType
font contains its own algorithms for converting the
outline into bitmaps.  The lower-level language
embedded within the TrueType font allows unlimited
flexibility in the design.  See TrueImage.



truncate
To cut off leading or trailing digits or characters
from an item of data without regard to the accuracy
of the remaining characters.  Truncation occurs
when data is converted into a new record with
smaller field lengths than the original.



trunk
A communications channel between two points.  It
often refers to large-bandwidth telephone channels
between major switching centers, capable of
transmitting many simultaneous voice and data
signals.



truth table
A chart of a logical operation's inputs and
outputs.  The following example is a Boolean AND
truth table:

         Inputs  Output
        Ŀ
         0   0   0  
         0   1   0  
         1   0   0  
         1   1   1  
        





TSAPI
(Telephony Services API)  A telephony programming
interface from Novell and AT&T.  Based on the
international CSTA standard, TSAPI is designed to
interface a telephone PBX with a NetWare server to
provide interoperability between PCs and telephone
equipment.



TSAT
See VSAT.



Tseng Labs
(Tseng Labs, Inc., Newtown, PA)  A manufacturer of
chipsets used in VGA graphics adapters.  Since
1986, its ET3000 and ET4000 chips have been used in
over 17 million video cards.  Tseng's W32 family,
introduced in 1993, provides graphics acceleration.



TSO
(Time Sharing Option)  Software that provides
interactive communications for IBM's MVS operating
system.  It allows a user or programmer to launch
an application from a terminal and interactively
work with it.  The TSO counterpart in VM is called
CMS.  Contrast with JES, which provides batch
communications for MVS.



TSOP
(Thin Small Outline Package)  One-millimeter-thick
package used to house dynamic RAM chips.



TSR
(Terminate and Stay Resident)  Refers to programs
that remain in memory so they can be instantly
popped up over the current application by pressing
a hotkey.  The program is displayed either as a
small window on top of the existing text or image,
or it takes the full screen.  When the program is
exited, previous screen contents are restored.

   On DOS PCs, TSRs provide quick access to a
calculator, calendar or dictionary; however,
conflicts may arise when multiple TSRs are loaded.
Older ones may not always work with newer ones.

   Task switching environments such as Windows and
DESQview, provide the ability to switch back and
forth between applications, thus making all
programs function as a TSR.

   The term refers to loading a program,
terminating its action but not removing it from
memory.



TSS
See ITU-TSS.



TTFN
(Ta Ta For Now)  An e-mail "goodbye" acronym.



TTL
(Transistor Transistor Logic)  A digital circuit in
which the output is derived from two transistors.
Although TTL is a specific design method, it often
refers generically to digital connections in
contrast with analog connections.  For example, a
TTL input on a monitor requires digital output from
the display board rather than analog output.



TTY
(TeleTYpewriter)  See teletypewriter.



TTY protocol
A low-speed asynchronous communications protocol
with limited or no error checking.



tube
See CRT and vacuum tube.



tuner
An electronic part of a radio or TV that locks on
to a selected carrier frequency (station, channel)
and filters out the audio and video signals for
amplification and display.



tuple
In relational database management, a record, or
row.  See relational database.



Turbo C
A C compiler from Borland used to create a wide
variety of commercial products.  It is known for
its well-designed debugger.  Borland's object-
oriented versions of C are Turbo C++ and Borland
C++.

   The DOS version of this database is written in
Turbo C.  The Windows version is written in
Microsoft C.



Turbo Mouse
A Macintosh trackball from Kensington Microware,
Ltd., San Mateo, CA.  If the ball is moved slowly,
the cursor moves slowly, but if moved quickly, the
same spatial ball movement moves the cursor a
greater distance on the screen.  Its PC counterpart
is called the Expert Mouse.



Turbo Pascal
A pascal compiler for DOS from Borland used in a
wide variety of applications from accounting to
complex commercial products.  Turbo Pascal for
Windows provides an object-oriented programming
environment for Windows development.  Borland is
responsible for moving the Pascal language from the
academic halls to the commercial world.



TURBOchannel
A 32-bit data bus from Digital introduced in 1990.
It has a peak transfer rate of 100 MBytes/sec.



turnaround document
A paper document or punched card prepared for re-
entry into the computer system.  Paper documents
are printed with OCR fonts for scanning  Invoices
and inventory stock cards are examples.



turnaround time
(1) In batch processing, the time it takes to
receive finished reports after submission of
documents or files for processing.  In an online
environment, turnaround time is the same as
response time.

(2) In half-duplex transmission, the time it takes
to change from transmit to receive and vice versa.



turnkey system
A complete system of hardware and software
delivered to the customer ready-to-run.



turnpike effect
In communications, a lock up due to increased
traffic conditions and bottlenecks in the system.



Turtle Beach
(Turtle Beach Systems, York, PA)  A manufacturer of
sound cards that is noted for its quality sound.
Its Multisound card won many awards.  Subsequent
products have merged quality sound with Windows
multimedia and DOS game compatibility.



turtle graphics
A method for creating graphic images in Logo.  The
turtle is an imaginary pen that is given drawing
commands, such as go forward and turn right.  On
screen, the turtle is shaped like a triangle.



tutorial
An instructional book or program that takes the
user through a prescribed sequence of steps in
order to learn a product.  Contrast with
documentation, which, although instructional, tends
to group features and functions by category.



TUV
(Technischer berwachungs-Verein)  Literally
"Technical Watch-Over Association."  A German
certifying body involved with product safety for
the European Community.  The "TV Rheinland" mark
is placed on tested and approved electrical and
electronic devices like our UL (Underwriters
Laboratory) seal.



Tuxedo
A TP monitor from Novell that runs on a variety of
UNIX-based computers.  Originally developed by AT&T
and sold as source code, Novell has enhanced the
product and is offering it as shrink-wrapped
software for various UNIX servers.  Tuxedo and
Transarc's Encina are the major TP monitors in the
UNIX client/server environment.




TWAIN
A programming interface that lets a graphics
application, such as a desktop publishing program,
activate a scanner, frame grabber or other image-
capturing device.



tweak
To make minor adjustments in an electronic system
or in a software program in order to improve
performance.



tweening
An animation technique that, based on starting and
ending shapes, creates the necessary "in-between"
frames.  See morphing.



twinax
See twinaxial.



twinax card
An expansion board in a personal computer that
emulates a 5250 terminal, the common terminal on an
IBM midrange system (AS/400, System/3x).



TwinAxcess
An IBM midrange terminal emulation system for the
Macintosh from Andrew/KMW, Austin, TX.  It includes
a controller card and software that emulates the
5250 terminal used on System/3x and AS/400s.  It
allows the user to have seven concurrent sessions
broadcast over LocalTalk, EtherTalk or TokenTalk
networks.



twinaxial
A type of cable similar to coax, but with two inner
conductors instead of one.  It is used in IBM
midrange (AS/400, System/3x) communications
environments.



TWIP
(TWentIeth of a Point)  Equal to 1/1440th of an
inch.



twisted nematic
See TN.



twisted pair
A thin-diameter wire (22 to 26 guage) commonly used
for telephone wiring.  The wires are twisted around
each other to minimize interference from other
twisted pairs in the cable.  Twisted pairs have
less bandwidth than coaxial cable or optical fiber.

   The two major types are unshielded twisted pair
(UTP) and shielded twisted pair (STP).  UTP is
popular because it is very pliable and doesn't take
up as much room in ductwork as does shielded
twisted pair and other cables.

   Shielded twisted pair is wrapped in a metal
sheath for added protection against external
interference.  See cable categories.



two-out-of-five code
A numeric code that stores one decimal digit in
five binary digits in which two of the bits are
always 0 or 1 and the other three are always in the
opposite state.



two-phase commit
A technique for ensuring that a transaction
successfully updates all appropriate files in a
distributed database environment.  All DBMSs
involved in the transaction first confirm that the
transaction has been received and is recoverable
(stored on disk).  Then each DBMS is told to commit
the transaction (do the actual updating).



two-tier client/server
A two-way interaction in a client/server
environment, in which the user interface is stored
in the client and the data is stored in the server.
The application logic can be in either the client
or the server.  See fat client, fat server and
three-tier client/server.



two-wire lines
A transmission channel made up of only two wires,
such as used in the common dial-up telephone
network.



TWX
(TeletypeWriter eXchange Service)  A U.S. and
Canadian dial-up communications service that uses
teleprinters and transmits 5-bit Murray code or 7-
bit ASCII code at up to 150 bps.  Originally part
of the Bell System, it was sold to Western Union in
1971 and interconnected with Telex.



TXD
(Transmitting Data)  See modem.



TXT file
See ASCII file.



Tymnet
(BTC Tymnet) A value-added, packet switching
network that enables many varieties of terminals
and computers to exchange data.  It is a subsidiary
of  British Telecom Corporation.



type
(1) In data or text entry, to press the keys on the
keyboard.

(2) In programming, a category of variable that is
determined by the kind of data stored in it.  For
example, integer, floating point, string, logical,
date and binary are common data types.

(3) (Type) In DOS and OS/2, a command that displays
the contents of a text file.



Type 1 font
See PostScript.



Type 3 font
See PostScript.



type ball
A golf ball-sized element used in typewriters and
low-speed teleprinters that contains all the print
characters on its outside surface.  It was
introduced with IBM's Selectric typewriter.



type family
See typeface family.



type font
A set of print characters of a particular design
(typeface), size (point size) and weight (light,
medium, heavy).  See font.



type scaler
See font scaler.



typeahead buffer
See keyboard buffer.



typeface
The design of a set of printed characters, such as
Courier, Helvetica and Times Roman.  The following
chart shows common typeface measurements.

    
                               Ascender area
           
 Point                      
  size                        x-height
                      
           BASELINE
                                 Descender area
 ͳ  
      
 ͳ
      
  Leading (in points, from baseline to baseline)
      
      
      
      
 BASELINE





typeface family
A group of typefaces that include the normal, bold,
italic and bold-italic variations of the same
design.



typematic
A keyboard feature that contiues to repeat a key as
long as it is held down.  The speed of the
repeating key as well as the time interval before
the repeat begins can be set by the DOS Mode
command and the Macintosh Control Panel.  See DOS
Mode.



typeover mode
In word processing and data entry, a state in which
each character typed on the keyboard replaces the
character at the current cursor location.  Contrast
with insert mode.



typesetter
See phototypesetter and imagesetter.



U.S. Robotics
(U.S. Robotics, Inc., Skokie, IL)  A modem
manufacturer highly regarded for its quality
modems.  The company manufactures its own chipsets
(data pumps) and often leads the industry with
innovations.  Its HST protocol was a high-speed and
reliable modem protocol before V.32bis became a
standard.



UAE
(Uninterruptible Application Error)  An application
program abend in Windows 3.0.  See GPF.



UART
(Universal Asynchronous Receiver Transmitter)  An
electronic circuit that transmits and receives data
on the serial port.  It converts bytes into serial
bits for transmission, and vice versa, and
generates and strips the start and stop bits
appended to each character.

   The older 8250A and 16450 UART chips provide a
one-byte buffer for storing data.  The 16550 UART
provides two 16-byte buffers for incoming data and
is essential for receiving at 9,600 bps and higher
rates, especially under Windows or when running the
communications program in the background.  See UART
overrun.



UART overrun
A condition in which a UART cannot process the byte
that just came in fast enough before the next one
arrives.



UCR
(Under Color Removal)  A method for reducing amount
of printing ink used.  It substitutes black for
gray color (equal amounts of cyan, magenta and
yellow).  Thus black ink is used instead of the
three CMY inks.  See GCR and dot gain.



UCSD p-System
(University of California at San Diego p-System) 
A software development system designed for
portability.  Source programs (BASIC, Pascal, etc.)
are compiled into an interim "p-code," which is
executed by an interpreter in the target machine.



UDP
(User Datagram Protocol)  A TCP/IP protocol that
allows an application to send a message to one of
several applications running in the destination
machine.  The application is responsible for
reliable delivery.



UHF
(Ultra High Frequency)  The range of
electromagnetic frequencies from 300MHz to 3GHz.



UI
See UNIX International and user interface.



UIMX
(User Interface Management System for X Window)
Software from Visual Edge Software, Ltd., St.
Laurent, Quebec, that allows a user to design and
modify Open Look and Motif interfaces.



ULSI
(Ultra Large Scale Integration)  More than one
million transistors on a chip.  See SSI, MSI, LSI
and VLSI.



ultrafiche
Pronounced "ultra feesh."  A microfiche that holds
up to 1,000 document pages per 4x6" sheet of film.
Normal microfiche stores around 270 pages.



ultraviolet
An invisible band of radiation at the high-
frequency end of the light spectrum.  It takes
about 10 minutes of ultraviolet light to erase an
EPROM chip.



ULTRIX
Digital's version of UNIX for its PDP-11 and VAX
series.



UMA
(Upper Memory Area)  PC memory between 640K and
1024K.  See PC memory map, PC conflicts and DOS
Dos.



UMB
(Upper Memory Block)  Unused blocks in the UMA
(640K-1M).  A UMB provider, such as EMM386.EXE, is
software that can load and manage drivers and TSRs
in these unoccupied areas.  See PC memory map, PC
conflicts, DOS Dos and DOS EMM386.EXE.



unary
Meaning one; a single entity or operation, or an
expression that requires only one operand.



unbundle
To sell components in a system separately.
Contrast with bundle.



UNC
(Universal Naming Service)  A standard for
identifying servers, printers and other resources
in a network.



unconditional branch
In programming, a GOTO, BRANCH or JUMP instruction
that passes control to a different part of the
program.  Constrast with conditional branch.



undelete
To restore the last delete operation that has taken
place.  There may be more than one level of
undelete, allowing several or all previous
deletions to be restored.  See DOS Undelete.



under cover removal
See UCR.



underflow
(1) An error condition that occurs when the result
of a computation is smaller than the smallest
quantity the computer can store.

(2) An error condition that occurs when an item is
called from an empty stack.



underscan
Within the normal rectangular viewing area on a
display screen.  Contrast with overscan.



undo
To restore the last editing operation that has
taken place.  For example, if a segment of text has
been deleted or changed, performing an undo will
restore the original text.  Programs may have
several levels of undo, including being able to
reconstruct the original data for all edits
performed in the current session.



Unibus
A bus architecture from Digital that was introduced
in 1970 with its PDP-11 series.  Unibus peripherals
can be connected to a VAX through Unibus
attachments on the VAXs.



unicast
To transmit from one station to another, such as
from client to server or server to server.
Contrast with multicast.



Unicode
A superset of the ASCII character set that uses two
bytes for each character rather than one.  Able to
handle 65,536 character combinations rather than
just 256, it can house the alphabets of most of the
world's languages.  ISO defines a four-byte
character set for world alphabets, but also uses
Unicode as a subset.



unidirectional
The transfer or transmission of data in a channel
in one direction only.



UNIFACE
An application development system for client/server
environments from Uniface Corporation, Alameda, CA.
It is a repository-driven system that imports a
variety of CASE tools.  It supports Windows, Mac
and OS/2 clients and VMS and UNIX servers.  UNIFACE
is known for its scalability and deployment on
large enterprise-wide applications.  Uniface
Corporation is part of Uniface International, which
was acquired by Compuware of Farmington Hills, MI.



UniForum
A membership association of computer professionals
dedicated to advancing open systems.  Membership
includes the "UniForum Monthly" magazine and other
technical and standards publications, discounts on
products and services and eligibility to serve on
committees and the Board of Directors.  Address:
2901 Tasman Drive, Santa Clara, CA 95054, 800/255-
5620.



UNIFY 2000
A relational DBMS for UNIX platforms from Unify
Corporation, Sacramento, CA.  Introduced in 1982,
it was the first commercially available RDBMS for
UNIX.



Unify VISION
An application development system for client/server
environments from Unify Corporation, Sacramento,
CA.  Introduced in 1993, it provides visual
programming tools and supports a variety of UNIX
platforms and databases.  It provides automated
application partitioning for developing three-tier
client/server architectures.  Other Unify
Corporation products are the ACCELL/SQL 4GL and
UNIFY 2000 relational DBMS.



uninstall
To remove hardware or software from a computer
system.  In order to remove a software application
from a PC, an uninstall program, also called an
uninstaller, deletes all the files that were
initially copied to the hard disk and restores the
AUTOEXEC.BAT, CONFIG.SYS, WIN.INI and SYSTEM.INI
files if they were modified.

   Many applications come with their own uninstall
utility.  Otherwise, a generic uninstall program
can be used to uninstall any application.  It must
be used when the application is first installed,
because it works by monitoring and recording all
changes made to the computer system.



uninterruptible power supply
See UPS.



union
In relational database, the joining of two files.
See set theory.



UniSQL
An object-oriented DBMS from UniSQL, Austin, TX.
UniSQL/X is a relational and object-oriented DBMS
for UNIX servers that provides SQL and object
access to the database.  UniSQL/M adds object-
oriented capability to SQL Server, Oracle, Ingres
and other relational DBMSs.



Unisys
(Unisys Corporation, Blue Bell, PA)  A computer
manufacturer formed in 1986 as a merger of
Burroughs and Sperry corporations.  This was the
largest computer merger in history.

   Sperry started in 1933 in navigational guidance
and control equipment.  In 1955, it merged with
Remington Rand, creator of the UNIVAC I, and became
Sperry Rand.  Sperry became known for its large-
scale mainframes and for providing communications
and realtime systems to the military and NASA.  In
1971, it absorbed RCA's Spectra 70 computer line
and supported it until it phased out.

   Burroughs started as a maker of calculating
machines and cash registers in 1886.  It was first
involved with computers by supplying memory for the
ENIAC in 1952.  A decade later, it introduced the
B5000 computer, which was hailed for its advanced
operating system.  Burroughs computers became well
established in the banking and finance industries.

   Today, Unisys' A Series and 2200 line, ranging
from desktops to high-end mainframes, are current
versions of product lines originating from both
companies.  A full range of UNIX systems, PCs and
CTOS-based machines are also available.  In
addition, Unisys provides integrated solutions for
vertical markets as well as business consulting
services.



unit record equipment
See tabulating equipment.



unit test
Running one component of a system for testing
purposes.  See system test.



UNIVAC I
(UNIVersal Automatic Computer)  The first
commercially-successful computer, introduced in
1951 by Remington Rand.  Over 40 systems were sold.
Its memory was made of mercury-filled acoustic
delay lines that held 1,000 12-digit numbers.  It
used magnetic tapes that stored 1MB of data at a
density of 128 cpi.  In 1952, it predicted
Eisenhower's victory over Stevenson, and UNIVAC
became synonymous with computer (for a while).



UniVBE
(UNIveral VESA BIOS Extension)  A SciTech Software
VESA driver from TR Consulting, San Jose, CA, that
supports VGA adapters from more than 20 different
vendors.  It allows DOS applications that are
written to the VESA BIOS Extension standard to work
with most of the display adapters on the market.



Univel
A joint venture of Novell and USL, which created
UnixWare.  In 1993, Novell acquired USL and merged
Univel and USL into Novell's Unix Systems Group.



universal product code
See UPC.



UNIX
A multiuser, multitasking operating system
originally developed by AT&T.  UNIX is written in
C, also developed by AT&T, which can be compiled
into many different machine languages, causing UNIX
to run in a wider variety of hardware than any
other operating system.  UNIX has thus become
synonymous with "open systems."

   UNIX is made up of the kernel (fundamental
tasks), the file system (hierarchical directory for
organizing the disk) and the shell (interface that
processes user commands).  The major command-line
interfaces are the Bourne shell, C shell and Korn
shell.  The UNIX vocabulary is exhaustive with over
600 commands that manipulate data and text every
way conceivable.  Many commands are cryptic (see
comparison below), but just as Windows hides the
DOS prompt, graphical user interfaces, such as
OSF/Motif and Open Look, are presenting a
friendlier image to UNIX users.

      Command         UNIX   DOS
    List directory     ls    dir
    Copy a file        cp    copy
    Delete a file      rm    del
    Rename a file      mv    rename
    Display contents   cat   type
    Print a file       lpr   print
    Check disk space   df    chkdsk



                The History of UNIX
UNIX was developed in 1969 by Ken Thompson at AT&T,
who scaled down the sophisticated MULTICS operating
system for the PDP-7.  The named was coined for a
single-user version (un) of MULT "ICS" (ix).  More
work was done by Dennis Ritchie, and, by 1974, UNIX
had matured into a state-of-the-art operating
system primarily on PDPs.  UNIX became very popular
in scientific and academic environments.

   Considerable enhancements were made to UNIX at
the University of California at Berkeley, and
versions of UNIX with the Berkeley extensions
became widely used.  By the late 1970s, commercial
versions of UNIX, such as IS/1 and XENIX, became
available.

   In the early 1980s, AT&T began to consolidate
the many UNIX versions into standards which evolved
into System III and eventually System V.  Before
divestiture (1984), AT&T licensed UNIX to
universities and other organizations, but was
prohibited from outright marketing of the product.
After divestiture, it began to market UNIX
aggressively.

   In 1989, UNIX Software Operation (USO) was
formed as an AT&T division.  USO introduced System
V Release 4.0 (SVR4), which incorporated XENIX,
SunOS, Berkeley 4.3BSD and System V into one UNIX
standard.  The System V Interface Definition (SVID)
was introduced, which defined UNIX compatibility.
In 1990, USO was turned into UNIX System
Laboratories, Inc. (USL), an AT&T subsidiary.  In
1993, USL was acquired by Novell and merged into
Novell's Unix Systems Group.

   Although every major hardware vendor has a
version of UNIX, X/Open and POSIX are industry
associations that govern UNIX standards, commonly
referred to as "open systems."  The Open Software
Foundation (OSF) also promotes software for
universal adoption.

   More attempts at unifying UNIX into one standard
have been made than for any other operating system.
Over the years various industry consortia have
tried to make UNIX a shrink-wrapped standard like
DOS, Windows and the Mac.  However, since UNIX runs
on so many different hardware platforms, the only
way the same UNIX software package can ever run on
all of them is by the use of a pseudo language,
such as proposed by the OSF (see ANDF in the OSF
definition).  While possible in theory, this is
highly unlikely in the near future.

   What UNIX application developers really hope for
is a single UNIX programming interface (API) so
that they only have to recompile the source code
for each platform, rather than maintain different
versions of the source code.  See Spec 1170.

   Nevertheless, with all of its versions, UNIX has
evolved into the archetype operating system for
industrial-strength processing in a distributed
environment.  TCP/IP communications protocols are
used in the Internet, the world's largest network
of networks.  SMTP provides e-mail, NFS allows
files to be distributed across the network, NIS
provides a "Yellow Pages" directory, Kerberos
provides network security, and X Window allows a
user to run applications on other machines in the
network simultaneously.  See X/Open, OSF, POSIX,
COSE and BSD UNIX.



UNIX International
A non-profit industry association that was founded
to provide direction for UNIX System V.  It was
disbanded at the end of 1993 after Novell purchased
UNIX from AT&T.



UNIX socket
A UNIX communications interface that lets an
application access a network protocol by "opening a
socket" and declaring a destination.  Sockets are
very popular because they provide a simple way to
direct an application onto the network (TCP/IP
protocol).  NetWare 3.x also supports sockets as
one of the common transport interfaces.



UNIX to UNIX copy
See UUCP.



UnixWare
An operating system for 386s and up from Novell
based on UNIX System V Release 4.2.  UnixWare
Personal Edition is a single-user version that
provides client access to NetWare and runs UNIX,
DOS and Windows applications.  It also includes the
Motif and Open Look graphical interfaces.

   UnixWare Application Server provides a multiuser
UNIX application server in a NetWare LAN.  It
supports TCP/IP and X Window.

   UnixWare was originally developed by Univel, a
joint venture of Novell and USL; however, in 1993,
Novell acquired USL outright.  Thus, Novell has
made a major commitment to UNIX, and UnixWare is
now the trade name of its family of UNIX products.



unload
To remove a program from memory or take a tape or
disk out of its drive.



UNMA
(Unified Network Management Archicture)  A network
strategy from AT&T for managing multi-vendor
networks.



unmark
(1) In word processing, to deselect a block of
text, which usually removes its highlight.

(2) To deselect an item that has been tagged for a
particular purpose.



unpack
See pack.



unshielded twisted pair
See twisted pair.



unzip
To decompress a file with PKUNZIP.  See PK
software.



up
Refers to a device that is working.



UPC
(Universal Product Code)  The standard bar code
printed on retail merchandise.  It contains the
vendor's identification number and the product
number, which is read by passing the bar code over
a scanner.



update
To change data in a file or database.  The terms
update and edit are often used synonymously.



uplink
A communications channel from an earth station to a
satellite.  Contrast with downlink.



upload
See download.



upper CASE
See front-end CASE.



Upper Memory Area
See UMA.



Upper Memory Block
See UMB.



UPS
(Uninterruptible Power Supply)  Backup power used
when the electrical power fails or drops to an
unacceptable voltage level.  Small UPS systems
provide battery power for a few minutes; enough to
power down the computer in an orderly manner.
Sophisticated systems are tied to electrical
generators that can provide power for days.

   A UPS system can be connected to a file server
so that, in the event of a problem, all network
users can be alerted to save files and shut down
immediately.

   An online UPS provides a constant source of
electrical power from the battery, while the
batteries are being recharged from AC power.  An
offline UPS, also known as a standby power system
(SPS), switches to battery within a few
milliseconds after detecting a power failure.

   A surge protector filters out surges and spikes,
and a voltage regulator maintains uniform voltage
during a brownout, but a UPS keeps a computer
running when there is no electrical power.  UPS
systems typically provide surge suppression and may
also provide voltage regulation.

             UPS - Now More Than Ever
In order to improve performance, personal computers
are increasingly using write back caches, which
means that updated data intended for the disk is
temporarily stored in RAM.  If a power failure
occurs, there is more of a chance that new data
will be lost, thus UPS systems are becoming
important for commonplace desktop computers.



uptime
The time during which a system is working without
failure.  Contrast with downtime.



upward compatible
Also called forward compatible.  Refers to hardware
or software that is compatible with succeeding
versions.  Contrast with downward compatible.



used computers
The following list of used computer prices is a
monthly "Index of Computer Prices" from the
American Computer Exchange (AmCoEx), Atlanta, GA.
This information is reprinted with permission of
AmCoEx.

   Equipment is sent from the seller to AmCoEx
where it is inspected and then sent on to the
buyer.  For more information, call 800/786-0717 or
FAX 404/250-1399.  For telephone numbers of other
computer exchanges, see computer exchange.


                The AmCoEx Index of
               Used Computer Prices
                   Jan. 6, 1995

                                        Change from
                             Avg    Avg        last
     Machine                 Bid    Ask Close month
IBM PS/2 70, 60MB             350   600   425  -25
IBM PS/2 90, 160MB           1000  1500  1125 -125
IBM PS/1 486DX2/50, 253MB     900  1350  1000 -100
IBM ThinkPad 350C            1900  2400  2100  -50
IBM ThinkPad 700             1000  1700  1175  -75
IBM ThinkPad 720             1600  2000  1650  -75

AST 486SX/25, 170MB           700  1250   825  -50
AST 486DX/66, 340MB          1050  1650  1200 +125
Dell 386/33, 100MB            600  1000   700  ---
Dell 486DX/33, 240MB          850  1500  1025  -75
Gateway 386/25, 80MB          400   800   575  -50
Gateway 486/33, 120MB         800  1200   950  +25

Clone Notebook 386SX, 40MB    500   900   675  -50
Clone 386/33, 80MB, VGA       450   900   575  -75
Clone 486/25, 120MB, VGA      700  1200   950  -25
Clone 486DX/33, 240MB, VGA    800  1425  1050  -75

Compaq LTE 286, 40MB          250   675   350  -50
Compaq Contura 320, 60MB      500  1000   900  ---
Compaq Contura 4/25, 120MB   1100  1600  1075  -25
Compaq Deskpro 386/20e,100MB  500   800   575  -75
Compaq Deskpro 486/33,120MB  1100  1650  1025  -75

Macintosh Classic II, 80MB    400   800   525  -75
Macintosh IIsi, 160MB         500   900   575  -75
Macintosh IIcx, 80MB          300   700   375  -25
Macintosh IIci, 80MB          500   950   675  +75
Macintosh IIfx, 80MB          700  1250   850 -100
Macintosh Quadra 700, 230MB  1100  1600  1300 -100
Macintosh Quadra 800, 500MB  2000  2700  2250 -100

PowerBook 140, 40MB           700  1100   775  -75
PowerBook 170, 40MB           800  1350  1125  +25
PowerBook 180, 80MB          1200  1850  1775  -50

Toshiba 1900, 120MB           800  1200   900  -50
Toshiba 3200SXC, 120MB       1850  2950  1925 -125
Toshiba 3300SL, 120MB        1050  1600  1025  -75
Toshiba 5200, 100MB           750  1050   825  -50

HP LaserJet II                350   850   575  -50
HP LaserJet IIIP              350   950   475  -25
HP LaserJet III               600   950   700  ---
HP LaserJet 4                 900  1300  1000  ---
Apple LaserWriter Pro 630    1300  1775  1475  -75


                End of AmCoEx List.





USENET
(USEr NETwork)  A public access network on the
Internet that provides user news and e-mail.  It is
a giant, dispersed bulletin board that is
maintained by volunteers willing to provide news
and mail feeds to other nodes.  It began in 1979 as
a bulletin board between two universities in North
Carolina.

   In 1994, the daily volume from all USENET
newsgroups and conferences exceeded 50MB of data.
All the news that travels over the Internet is
called NetNews, and a newsgroup is a running
collection of messages about a particular subject.
There are some 10,000 newsgroups on the Internet.

   In order to read the text of a newsgroup, you
need a newsreader, such as nn, rn or tin.



user
Any individual who interacts with the computer at
an application level.  Programmers, operators and
other technical personnel are not considered users
when working in a professional capacity on the
computer.



user area
A reserved part of a disk or memory for user data.



User Datagram Protocol
See UDP.



user defined
Any format, layout, structure or language that is
developed by the user.



user friendly
A system that is easy to learn and easy to use.
This term has been so abused that many vendors are
reluctant to use it.



user group
An organization of users of a particular hardware
or software product.  Members share experiences and
ideas to improve their understanding and use of a
particular product.  User groups are often
responsible for influencing vendors to change or
enhance their products.



user interface
The combination of menus, screen design, keyboard
commands, command language and help screens, which
create the way a user interacts with a computer.
Mice, touch screens and other input hardware is
also included.  A well-designed user interface is
vital to the success of a software package.  In
time, interactive video, voice recognition and
natural language understanding will be included.



USL
(UNIX System Laboratories, Inc.)  An AT&T
subsidiary formed in 1990, responsible for
developing and marketing UNIX.  In 1993, USL was
acquired by Novell and merged into Novell's Unix
Systems Group.



USO
(UNIX Software Operation)  AT&T's UNIX division
before it turned into USL.  See UNIX.



USRobotics
See U.S. Robotics.



USRT
(Universal Synchronous Receiver Transmitter)  An
electronic circuit that transmits and receives data
on the serial port.  It converts bytes into serial
bits for transmission, and vice versa, and
generates the necessary signals for synchronous
transmission.



utilities
See utility program.



utility program
A program that supports using the computer.
Utility programs, or "utilities," provide file
management capabilities, such as sorting, copying,
comparing, listing and searching, as well as
diagnostic and measurement routines that check the
health and performance of the system.  Since it is
easy to forget where a file has been saved, another
useful utility is a "file find," which searches all
directories for matching file names.



UTP
See twisted pair.



UTP Ethernet
(1) Same as twisted pair Ethernet.  See Ethernet.

(2) May refer to pre-IEEE standard twisted pair
Ethernet networks.



UTS
(Universal Timesharing System)  Amdahl's version of
UNIX System V.  Release 4.0 is POSIX compliant.



UUCP
(UNIX to UNIX CoPy)  A UNIX utility that copies a
file from one computer to another.  It is commonly
used as a mail transfer.  Unlike TCP/IP, which is a
routable communications protocol, UUCP provides a
point-to-point transmission where a user at one
UNIX computer dials up and establishes a session
with another UNIX computer.



UUNET
(UNIX to UNIX NETwork)  An information and
communications network from UUNET Technologies,
Inc., Falls Church, VA, that provides news, mail
service and an extensive library of UNIX software.
Custom networking for companies is available
through its AlterNet service.



v-mail
(Video mail)  The ability to send video clips along
with e-mail messages.  This is not the same as
video conferencing, which requires realtime
capabilities between sender and receiver, but it
does require high-speed computers and networks.



V Series
A series of of small to medium-scale mainframes
from Unisys that were the Burroughs B2500 and B3500
product lines, originally introduced in 1966.



V.110
An ITU-TSS standard (1984) that specifies how data
terminal equipment (DTE) with asynchronous or
synchronous serial interfaces can be supported on
an ISDN network.  It uses rate adaption, which
involves a bit-by-bit alignment between the DTE and
the ISDN B channel.



V.120
An ITU-TSS standard (1988) that specifies how DTEs
with asynchronous or synchronous serial interfaces
can be supported on an ISDN network using a
protocol (similar to LAP-D) to encapsulate the data
to be transmitted.  It includes the capability of
using statistical multiplexing to share a B channel
connection between multiple DTEs.



V.17
An ITU-TSS fax standard (1991) that uses TCM
modulation at 12000 and 14400 bps for Group 3.  It
adds TCM to the V.29 standard at 7200 and 9600 bps
to allow transmission over noisier lines.  It also
defines special functions (echo protection, turn-
off sequences, etc.) for half-duplex operation.
Modulation use is a half-duplex version of V.32bis.



V.21
An ITU-TSS standard (1964) for asynchronous 0-300
bps full-duplex modems for use on dial-up lines.
It uses FSK modulation.



V.22
An ITU-TSS standard (1980) for asynchronous and
synchronous 600 and 1200 bps full-duplex modems for
use on dial-up lines.  It uses DPSK modulation.



V.22bis
An ITU-TSS standard (1984) for asynchronous and
synchronous 2400 bps full-duplex modems for use on
dial-up lines and two-wire leased lines, with
fallback to V.22 1200 bps operation.  It uses QAM
modulation.



V.23
An ITU-TSS standard (1964) for asynchronous and
synchronous 0-600 and 0-1200 bps half-duplex modems
for use on dial-up lines.  It has an optional
split-speed transmission method with a reverse
channel of 0-75 bps (1200/75, 75/1200). It uses FSK
modulation.



V.24
An ITU-TSS standard (1964) that defines the
functions of all circuits for the RS-232 interface.
It does not describe the connectors or pin
assignments; those are defined in ISO 2110.  In the
U.S., EIA-232 incorporates the control signal
definition of V.24, the electrical characteristics
of V.28 and the connector and pin assignments
defined in ISO 2110.



V.25
An ITU-TSS standard (1968) for automatic calling
and/or answering equipment on dial-up lines.  It
uses parallel circuits and is similar in function
to RS-366 and Bell 801 autodialers used in the U.S.
The answer tone defined in V.25 is the first thing
heard when calling a modem.  It serves a dual
function of identifying the answering equipment as
being a modem and also disabling the echo
suppression and echo cancellation equipment in the
network so that a full-duplex modem will operate
properly.



V.25bis
An ITU-TSS standard (1968) for automatic calling
and/or answering equipment on dial-up lines.  It
has three modes: asynchronous (rarely used),
character-oriented synchronous (bisync) and bit-
oriented synchronous (HDLC/SDLC).  Both synchronous
versions are used in IBM AS/400 and other small-to-
medium sized computers that do automatic dialing
for remote job entry.

   Due to the popularity of the Hayes AT Command
Set, V.25bis is not used as widely in North
America.  It does not perform modem configuration
functions and is limited to dialing and answering
calls.



V.26
An ITU-TSS standard (1968) for synchronous 2400 bps
full-duplex modems for use on four-wire leased
lines.  It uses DPSK modulation and includes an
optional 75 bps back channel.



V.26bis
An ITU-TSS standard (1972) for synchronous 1200 and
2400 bps full-duplex modems for use on dial-up
lines.  It uses DPSK modulation and includes an
optional 75 bps back channel.



V.26ter
An ITU-TSS standard (1984) for asynchronous and
synchronous 2400 bps full-duplex modems using DPSK
modulation over dial-up and two-wire leased lines.
It includes a 1200 bps fallback speed and uses echo
cancellation, permitting a full-duplex modem to
send and receive on the same frequency.



V.27
An ITU-TSS standard (1972) for synchronous 4800 bps
full-duplex modems for use on four-wire leased
lines.  It uses DPSK modulation.



V.27bis
An ITU-TSS standard (1976) for synchronous 2400 and
4800 bps full-duplex modems using DPSK modulation
for use on four-wire leased lines.  The primary
difference between V.27 and V.27bis is the addition
of an automatic adaptive equalizer.



V.27ter
An ITU-TSS standard (1976) for synchronous 2400 and
4800 bps half-duplex modems using DPSK modulation
on dial-up lines.  It includes an optional 75 bps
back channel.  V.27ter is used in Group 3 fax
transmission without the back channel.



V.28
An ITU-TSS standard (1972) that defines the
functions of all circuits for the RS-232 interface.
In the U.S., EIA-232 incorporates the electrical
signal definitions of V.28, the control signals of
V.25 and the connector and pin assignments defined
in ISO 2110.



V.29
An ITU-TSS standard (1976) for synchronous 4800,
7200 and 9600 bps full-duplex modems using QAM
modulation on four-wire leased lines.  It has been
adapted for Group 3 fax transmission over dial-up
lines at 9600 and 7200 bps.



V.32
An ITU-TSS standard (1984) for asynchronous and
synchronous 4800 and 9600 bps full-duplex modems
using TCM modulation over dial-up or two-wire
leased lines.  TCM encoding may be optionally
added.  V.32 uses echo cancellation to achieve
full-duplex transmission.



V.32bis
An ITU-TSS standard (1991) for asynchronous and
synchronous 4800, 7200, 9600, 12000 and 14400 bps
full-duplex modems using TCM and echo cancellation.
Supports rate renegotiation, which allows modems to
change speeds as required.



V.32terbo
An AT&T standard for 19200 bps modems adopted by
some modem manufacturers.  See V.34.



V.33
An ITU-TSS standard (1988) for synchronous 12000
and 14400 bps full-duplex modems for use on four-
wire leased lines using QAM modulation.  It
includes an optional time-division multiplexor for
sharing the transmission line among multiple
terminals.



V.34
An ITU-TSS standard (1994) for 28800 bps modems.
Before V.34, AT&T's V.32terbo and Rockwell
International's V.FC modems came on the market to
provide greater speed than the V.32bis 14400 bps
standard.



V.35
An ITU-TSS standard (1968) for group band modems
that combine the bandwidth of several telephone
circuits to achieve high data rates.  V.35 has
become known as a high-speed RS-232 interface
rather than a type of modem.  The large,
rectangular V.35 connector was never specified in
V.35, but has become a de facto standard for a
high-speed interface.



V.42
An ITU-TSS standard (1989) for modem error checking
that uses LAP-M as the primary protocol and
provides MNP Classes 2 through 4 as an alternative
protocol for compatibility.



V.42bis
An ITU-TSS standard (1989) for modem data
compression.  It uses the British Telecom Lempel
Ziv technique to achieve up to a 4:1 ratio.
V.42bis implies the V.42 error checking protocol.



V.54
An ITU-TSS standard (1976) for various loopback
tests that can be incorporated into modems for
testing the telephone circuit and isolating
transmission problems.  Operating modes include
local and remote digital loopback and local and
remote analog loopback.



V.56
An ITU-TSS standard (1972) for a method of testing
modems to compare their performance.  Newer
procedures are currently under study.



V.Fast Class
See V.FC.



V.FC
(V.Fast Class)  A modem technology for 28800 bps
from Rockwell International endorsed by many modem
vendors before V.34 was finalized.  V.FC is very
similar to V.34, but V.FC modems require an
upgraded chip for full compatibility.



V20, V30
An 8088- and 8086-compatible processors from NEC.
Versions running at 16MHz were introduced in 1991.



VAC
(Volts Alternating Current)  See volt and AC.



vacuum tube
An electronic device that controls the flow of
electrons in a vacuum, used as a switch, amplifier
or display screen.  Used as on/off switches, they
allowed the first computers to perform digital
computations.  Today, it is primarily the CRT in
monitors and TVs.



VAD
(Value Added Dealer)  Same as VAR (value added
reseller).



VAFC
See VESA Advanced Feature Connector.



validity checking
Routines in a data entry program that tests the
input for correct and reasonable conditions, such
as numbers falling within a range and correct
spelling, if possible.  See check digit.



value
(1) The content of a field or variable.  It can
refer to alphabetic as well as numeric data.  For
example, in the expression, state = "PA", PA is a
value.

(2) In spreadsheets, the numeric data within the
cell.



value-added network
A communications network that provides services
beyond normal transmission, such as automatic error
detection and correction, protocol conversion and
message storing and forwarding.  Telenet and Tymnet
are examples of value-added networks.



Value Added Process
See VAP.



value added reseller
See VAR.



VAN
See value-added network.



VAP
(Value Added Process)  Software that enhances or
provides additional server functions in a NetWare
286 server.  Support for different kinds of
workstations, database engines, fax and print
servers are examples.  The NetWare 386 counterpart
is the NLM.



vaporware
Software that has been advertised but not
delivered.



VAR
(Value Added Reseller)  An organization that adds
value to a system and resells it.  For example, it
could purchase a CPU and peripherals from different
vendors, graphics software from another and package
it all together as a specialized CAD system.
Although VARs typically repackage products, they
might also include programs they have developed
themselves.  The terms VAR and ISV are often used
interchangeably.  See OEM, ISV and systems
integrator.



variable
In programming, a structure that holds data and is
uniquely named by the programmer.  It holds the
data assigned to it until a new value is assigned
or the program is finished.

   Variables are used to hold control values.  For
example, the C statement for (x=0; x<5; x++)
performs the instructions following it five times.
X is a variable set to zero (x=0), incremented
(x++) and tested to reach five (x<5).  Variables
also hold data temporarily that is being processed.

   Variables are usually assigned with an equal
sign; for example, counter = 1, places a 1 in
COUNTER.  Numeric data is unquoted: counter = 1,
character data requires quotes: product="abc4344".
In some languages, the type of data must be
declared before it is assigned; for example, in C,
the statement, int counter; creates a variable that
will only hold whole numbers.

   A local variable is one that is referenced only
within the subprogram, function or procedure it was
defined in.  A global variable can be used by the
entire program.



variable length field
A record structure that holds fields of varying
lengths.  For example, PAT SMITH would take nine
bytes and GEORGINA WILSON BARTHOLOMEW would take 27
plus a couple of bytes that would define the length
of the field.  If fixed length fields were used, at
least 27 bytes would have to be reserved for both
names.

   There's more programming with variable length
fields, because every record has to be separated
into fixed length fields after it is brought into
memory.  Conversely, each record has to be coded
into the variable length format before it is
written to disk.

   The same storage savings can be achieved by
compressing data stored on disk and decompressing
it when retrieved.  All blank spaces in fixed
length fields would be filtered out.  For
acceptable performance, this method must be well
integrated into the operating system.  See realtime
compression.



variable length record
A data record that contains one or more variable
length fields.



varname
(VARiable NAME)  An abbreviation for specifying the
name of a variable.



VAX
(Virtual Address eXtension)  A family of 32-bit
computers from Digital introduced in 1977 with the
VAX-11/780 model.  VAXes range from desktop
personal computers to mainframes all running the
same VMS operating system.  Large models can be
clustered in a multiprocessing environment to serve
thousands of users.  Software compatibility between
models caused the VAX family to achieve outstanding
success during the 1980s.  VAXes also provide PDP
emulation.



VAXcluster
A group of VAXs coupled together in a
multiprocessing environment.



VAXELN
A realtime operating environment for VAXs from
Digital.  It runs under VMS and provides
application development in Pascal and other
languages.  Resulting programs are downloaded into
the target systems.



VAXmate
A partially IBM-compatible PC from Digital
introduced in 1986, which has been superseded by
the DECstation 200 and 300 series in 1989.



VAXstation
A single-user VAX computer that runs under VMS
introduced in 1988.



VB
See Visual Basic.



VBA
(Visual Basic for Applications)  A subset of Visual
Basic that provides a common macro language for
Microsoft applications.  VBA lets power users and
programmers extend the functionality of programs
such as Word, Excel and Access.



VBE
See VESA BIOS Extension.



VBE/AI
See VESA BIOS Extension/Audio Interface.



Vbox
(Video box)  A hardware interface from Sony that
attaches up to seven VCRs, videodiscs and
camcorders to the serial port.  Devices must have
the Control-L (LANC) connector.



VBX
A dynamic link library file that contains user-
developed controls for Visual Basic applications.



VCPI
(Virtual Control Program Interface)  A DOS extender
specification for 386s and up that allows DOS
extended programs to run with Real Mode programs.
VCPI allows for example, Paradox 386, a DOS-
extended program, to run cooperatively with
DESQview, which runs multiple Real Mode programs in
Virtual 8086 mode.  Developed by Quarterdeck, Phar
Lap Software, et al, it was the first DOS extender
standard.  See DPMI.


               XMS Versus VCPI/DPMI
XMS, VCPI and DPMI all deal with extended memory.
However, XMS allows data and programs to be stored
in and retrieved from extended memory, whereas the
VCPI and DPMI interfaces allow programs to "run" in
extended memory.



VCR
(Video Cassette Recorder)  A videotape recording
and playback machine that comes in the following
formats:

   One inch tape is used for mastering video
recordings.  Sony Umatic 3/4" tape was widely used
in commercial training.  VHS 1/2" tape, first used
only in the home, has mostly replaced the 3/4"
tape.  Sony's 1/2" Beta tape, the first home VCR
format, is defunct.

   Although VCRs are analog recording machines,
adapters allow them to store digital data for
computer backup.



VDE
(1) (Video Display Editor)  A WordStar and
WordPerfect-compatible shareware word processor
written by Eric Meyer.

(2) (Verband Deutscher Elektrotechniker)  The
German counterpart of the U.S. Underwriters Lab.



Vdeck
(video deck)  A frame-accurate, Super 8mm tape
drive from Sony for serial-port connection to a
personal computer.  It contains an internal Vbox,
is controlled by the ViSCA language and has no
external play buttons.



VDI
(1) (Video Device Interface)  An Intel standard for
speeding up full-motion video performance.  See
DCI.

(2) (Virtual Device Interface)  An ANSI standard
format for creating device drivers.  VDI has been
incorporated into CGI.



Vdisk
See DOS RAM disks.



VDM
(Virtual DOS Machine)  A DOS session created by
OS/2 and Windows NT in order to emulate a DOS
environment and run DOS and 16-bit Windows
applications.  Each application runs in a separate
VDM, each one simulating an individual DOS-based
PC.  VDMs are multitasked along with native
applications.  Also see CGM.



VDS
(Virtual DMA Services)  A programming interface
that lets bus mastering devices cooperatively
manage DMA channels.



VDT
(Video Display Terminal)  A terminal with a
keyboard and display screen.



VDT radiation
The electromagnetic radiation emitted from a
computer display screen.  Exhaustive testing so far
seems inconclusive, but vendors recommend keeping
the face at least 18 to 20 inches from the screen.



VDU
(Video Display Unit)  Same as VDT.



vector
(1) In computer graphics, a line designated by its
end points (x-y or x-y-z coordinates).  When a
circle is drawn, it is made up of many small
vectors.  See vector graphics and graphics.

(2) In matrix algebra, a one-row or one-column
matrix.



vector display
A display terminal that draws vectors on the
screen.  Contrast with raster display.



vector font
A scalable font made of vectors (point-to-point
line segments).  It is easily scaled as are all
vector-based images, but lacks the hints and
mathematically-defined curves of outline fonts,
such as Adobe Type 1 and TrueType.



vector graphics
In computer graphics, a technique for representing
a picture as points, lines and other geometric
entities.  See graphics.  Contrast with raster
graphics.



vector processor
A computer with built-in instructions that perform
multiple calculations on vectors (one-dimensional
arrays) simultaneously.  It is used to solve the
same or similar problems as an array processor;
however, a vector processor passes a vector to a
functional unit, whereas an array processor passes
each element of a vector to a different arithmetic
unit.  See pipeline processing and array processor.



vector to raster
See rasterize.



Vectra
A family of PCs from HP.  Vectras are noted for
their ruggedness and reliability.



veesa
See VESA.



vendors
There are thousands of companies comprising the
computer industry.  The following hardware,
software, consulting and service vendors represent
all the majors and some of the more widely known.
Many are individual entries in this database.  See
hardware vendors and software vendors.


  ACER AMERICA CORP., San Jose, CA, 800/SEE-ACER
  Complete line of PCs under Acer and Acros brands.


  ADOBE SYSTEMS, INC., Mtn. View, CA, 800/833-6687
  PostScript language and Type 1 and Type 3 font
  technologies.


  ADVANCED LOGIC RESEARCH, Irvine, CA, 800/257-1230
  Complete line of PCs. "ALR" pioneered upgradable
  CPU architecture.


  ADVANCED MICRO DEVICES, Sunnyvale, CA, 800/2929-
  AMD; Intel-compatible CPU chips.


  ALDUS CORP., Seattle, WA, 800/332-5387
  Pioneered desktop publishing with PageMaker,
  originally on the Mac.


  AMDAHL CORP., Sunnyvale, CA, 800/538-8460
  First successful IBM-compatible mainframe
  manufacturer.


  AMERICAN MEGATRENDS, INC., Norcross, GA
  800/828-9264; "AMI" PC motherboards, ROM BIOS.


  APPLE COMPUTER, INC., Cupertino, CA, 800/776-2333
  Macintosh series and Apple IIe. Largest non-IBM
  compatible personal computer manufacturer.
  Pioneered the microcomputer revolution.


  ARTISTOFT, INC., Tucson, AZ, 800/TINYRAM
  Lantastic network operating system. Major
  success in peer-to-peer networking.


  AST RESEARCH, INC., Irvine, CA, 714/727-4141
  Complete line of PCs sold through the dealer
  channel. Revenues of one billion in 1992.


  ATARI, INC., Sunnyvale, CA, 408/745-2000
  ST and Falcon personal computers. Founded in 1972
  by Nolan Bushnell. Known for its video games.


  AUSTIN COMPUTER SYSTEMS, Austin, TX, 800/752-1577
  Complete line of PCs and network servers direct
  and via dealers. Subsidiary of IPC.


  AUTODESK, INC., Sausalito, CA, 800/964-6432
  AutoCAD software, one of the first major
  CAD programs for personal computers.


  BOLT, BARANEK & NEWMAN, Cambridge, MA, 800/422-
  2359; Consulting, software, research. "BBN"
  has been at the forefront of major projects.


  BORLAND INT'L. INC., Scotts Valley, CA
  800/331-0877  Programming languages, dBASE,
  Paradox, Quattro Pro, Sidekick. First to
  commercialize Pascal (Turbo Pascal).


  BULL HN, Billerica, MA, 800/999-2181
  Mini and mainframe manufacturer originally
  started as Honeywell's computer division, later
  merged with Groupe Bull of France and NEC of
  Japan.


  CLARIS CORP., Santa Clara, CA, 800/325-2747
  Software subsidiary of Apple Computer
  MacDraw, MacWrite, FileMaker Pro, HyperCard, etc.


  COMMODORE BUSINESS MACHINES, INC., West Chester,
  PA, 800/66-AMIGA; Amiga personal computer line.
  Founded in 1977 and introduced the PET, one of
  the first personal computers.


  COMPAQ COMPUTER CORP., Houston, TX, 800/345-1518
  Complete line of PCs. First to successfuly clone
  IBM PC. First portable PC. First American
  company to reach $111 million sales in a year.


  COMPUSERVE, INC., Columbus, OH, 800/848-8990
  Widely-used online information service.


  COMPUTER ASSOCIATES INT'L, INC., Islandia, NY
  800/CALL-CAI  Software from micro to mainframe.
  Founded in 1976 by Charles Wang.


  CONNER PERIPHERALS, INC., San Jose, CA
  408/456-4500  Manufacturer of disk drives.


  CONTROL DATA SYSTEMS, INC., Arden Hills, MN
  612/482-2401  One of the first computer
  companies. Founded in 1957 under Bill Norris.
  No longer makes proprietary hardware.
  Specializes in open systems integration.


  CRAY RESEARCH, INC., Egan, MN, 800/284-2729
  Supercomputers originally designed by Seymour
  Cray, leading architect at Control Data.


  D&B SOFTWARE, Atlanta, GA, 800/234-3867
  1990 merger of MSA and McCormack & Dodge
  mainframe software companies.


  DATA GENERAL CORP., Westboro, MA, 800/328-2436
  One of the pioneers in minicomputers. Founded
  in 1968 by Edson De Castro.


  DELL COMPUTER CORP., Austin, TX, 800/289-3355
  Complete line of mail-order PCs. Originally
  "PCs Limited" brand. First to legitimize mail-
  order PCs with quality telephone support.


  DIALOG INFORMATION SERVICES, Palo Alto, CA
  800/334-2564  Online service. Largest collection
  of databases in the world.


  DIGITAL EQUIPMENT CORP., Maynard, MA, 800/344-
  4825; "DEC" pioneered the minicomputer industry
  under leadership of Ken Olsen who retired in
  1992. Complete line of PCs, minis and mainframes.
  Founded in 1957.


  DIGITAL RESEARCH, INC., Monterey, CA, 800/274-
  4DRI; Creator of CP/M, first common operating
  system for personal computers. Later DOS-
  compatible DR DOS. Founded in 1976 by Gary
  Kildall. Acquired by Novell in 1991.


  ELECTRONIC DATA SYSTEMS CORP., Maryland Hgts, MO
  314/344-5900  Pioneered facilities management.
  Founded in 1962 by Ross Perot. Acquired by GM.


  EVEREX SYSTEMS, INC., Fremont, CA, 800/356-8486
  Complete line of PCs, high-end servers.


  GATEWAY 2000, N. Sioux City, SD, 800/846-2000
  Complete line of mail-order PCs. Became very
  successful in early 1990s.


  GENIE, Rockville, MD, 800/638-9636
  Online service. Wide variety of databases.


  HAYES MICROCOMPUTER PRODUCTS, INC., Atlanta, GA
  404/840-9200  Pioneered the personal computer
  modem. Hayes AT command set is de facto standard
  modem language.


  HEWLETT-PACKARD CO., Palo Alto, CA, 800/752-0900
  HP was one of the first minicomputer companies.
  Complete line of PCs, workstations and minis plus
  10,000 electronic products. Founded in 1939 by
  William Hewlett & David Packard.


  HITACHI AMERICA (various locations in U.S.)
  Monitors, CD-ROM players, computers.


  INTERNATIONAL BUSINESS MACHINES CORP., Armonk, NY
  800/426-2468; "IBM" is the world's largest
  computer company. Complete line of mainframes,
  minis and PCs. Founded in 1911. Renamed IBM in
  1924 under leadership of T. J. Watson, Sr.


  INTEL CORP., Santa Clara, CA, 800/538-3373
  Maker of x86 CPU chips used in PCs.


  LOTUS DEVELOPMENT CORP., Cambridge, MA
  800/343-5414; First spreadsheet (Lotus 1-2-3)
  for the PC, Ami Pro, Lotus Notes, etc. Founded in
  1981 by Mitch Kapor.


  MAXTOR CORP., San Jose, CA, 800/262-9867
  Disk drives manufacturer.


  MICRONICS COMPUTERS, INC., Fremont, CA
  510/651-2300  PC motherboards, electronics,
  laptops.


  MICROSOFT CORP., Redmond, WA, 800/227-4679
  DOS, Windows, programming langauges and
  applications. Founded in 1975 by Bill Gates and
  Paul Allen.


  MOTOROLA, INC., Schaumburg, IL, 708/576-5000
  Maker of 68xxx CPU chips used in Macintoshes
  and various workstations.


  NCR CORP., Dayton, OH, 800/CALL-NCR
  One of the first computer companies. Leading
  cash register company dating back to 1884 under
  John Henry Patterson. Acquired by AT&T in 1991.


  NEC TECHNOLOGIES, INC., Boxborough, MA
  800/343-4418; Pioneered multifrequency monitor
  with its MultiSync line.


  NEXT COMPUTER, INC., Redwood City, CA, 800/848-
  NEXT; NeXTstep operating environment. Founded by
  Steve Jobs, co-founder of Apple.


  NORTHGATE COMPUTER SYSTEMS, INC., Minneapolis, MN
  800/548-1993; Complete line of mail-order PCs.
  Known for its Omnikey keyboards. Founded in 1987.


  NOVELL, INC., Provo, UT, 800/453-1267
  NetWare operating systems. Most widely-used
  networking software. Founded in 1983 by Ray
  Noorda. Acquired USL in 1993.


  OPEN SOFTWARE FOUNDATION, Cambridge, MA
  617/621-8700  UNIX-based open systems
  software for distributed computing.


  ORACLE CORP., Redwood Shores, CA, 800/ORACLE-1
  Oracle database system runs on more platforms
  than any other DBMS. Founded in 1977.


  PACKARD BELL, INC., Chatsworth, CA, 818/886-4600
  Complete line of PCs and peripherals. Founded
  in 1986.


  PHOENIX TECHNOLOGIES, INC., Norwood, MA
  800/344-7200  PC ROM BIOS chips, electronics.


  POWERSOFT CORPORATION, Concord, MA
  508/287-1500  Publisher of PowerBuilder
  application development software.


  PRODIGY, White Plains, NY, 800/776-3449
  Online service for home and office computing.
  Shopping, news, databases.


  QUARK, INC., Denver, CO., 800/788-7835
  QuarkXpress desktop publishing for
  Mac and Windows.


  SANTA CRUZ OPERATION (THE), Santa Cruz, CA
  800/SCO-9694; UNIX and XENIX operating systems.


  SEAGATE TECHNOLOGY, INC., Scotts Valley, CA
  800/468-3472; Largest independent
  manufacturer of disk drives.


  SEQUENT COMPUTER SYSTEMS, INC., Beaverton, OR
  800/243-6768; UNIX and Windows NT multiprocessing
  systems.


  SILICON GRAPHICS, INC., Mountain View, CA
  800/800-4744; High-end CAD and graphics
  workstations. Acquired MIPS Computer in 1992.


  SOFTWARE PUBLISHING CORP., Santa Clara, CA
  800/447-7991; Harvard Graphics, Superbase
  and other applications.


  SONY CORP. OF AMERICA, San Jose, CA, 800/352-7669
  Monitors, CR ROM players, disk drives and
  diskettes.


  SUN MICROSYSTEMS, INC., Mtn. View, CA, 800/821-
  4643; Complete line of workstations using Sun's
  SPARC CPU. Largest supplier of UNIX-based
  systems. Founded in 1982 by Bill Joy.


  SYMANTEC CORP., Cupertino, CA, 800/441-7234
  Q&A, Norton Utilities and other applications.


  TANDEM COMPUTERS, INC., Cupertino, CA
  800/538-3107; First to make fault-tolerant
  computer systems. Founded in 1974 by James
  Treybig.


  TANDON CORP., Moorpark, CA, 800/800-8850
  Complete line of PCs, peripherals.


  TANDY CORP., Ft. Worth, TX, 817/390-3011
  Complete line of PCs and electronics through
  Radio Shack chain originally acquired in 1963.
  TRS-80 was one of the first personal computers.


  TEXAS INSTRUMENTS, INC., Dallas, TX, 800/527-3500
  Chips, electronics, computer systems. Founded in
  1930 as Geophysical Service. Renamed TI in 1951.


  TOSHIBA AMERICA INFO. SYSTEMS, INC., Irvine, CA
  800/334-3445; Complete line of high-end, quality
  portable PCs. Pioneered laptop revolution.


  UNISYS CORP., Blue Bell, PA, 800-448-1424
  1986 merger of Sperry and Burroughs, two of the
  oldest computer companies. Complete line of PCs,
  minis and mainframes.


  UNIX SYSTEMS LABORATORIES, INC., Summit, NJ
  800/828-8649; Novell subsidiary responsible for
  developing and marketing UNIX System V.


  WANG LABORATORIES, INC., Lowell, MA, 800/835-9264
  Early minicomputer company and leader in WP in
  the 1970s. Founded by Dr. An Wang in 1951.


  WESTERN DIGITAL CORP., Irvine, CA, 800/832-4778
  Manufacturer of disk drives, controllers and
  electronics. "Paradise" display boards.


  WORDPERFECT CORP., Orem, UT, 800/321-5906
  WordPerfect is the most widely-used word
  processing software. Founded in 1979.


  WORDSTAR INT'L. INC., Novato, CA, 800/227-5609
  WordStar was the first full-featured word
  processor for personal computers. Founded in
  1978.


  ZEOS INTERNATIONAL, Minneapolis, MN, 800/554-7172
  Complete line of mail-order PCs and peripherals.


  ZENITH DATA SYSTEMS CORP., Buffalo Grove, IL
  800/227-3360  Complete line of PCs, monitors.
  Pioneered laptop revolution.


                  End of vendors.






Venn diagram
A graphic technique for visualizing set theory
concepts using overlapping circles and shading to
indicate intersection, union and complement.



Ventura Publisher
See Corel VENTURA.



verify
In data entry operations, to compare the keystrokes
of a second operator with the files created by the
first operator.



Veronica
A program that searches the Internet for specific
resources by description, not just file name.
Using Boolean searches (this AND this, this OR
this, etc.), users can search Gopher servers to
retrieve a selected group of menus that pertain to
their area of interest.  See Gopher.



VersaCAD
A family of CAD systems for PCs and the Macintosh
from Computervision, Bedford, MA, that features 2-D
geometric and construction drafting and 3-D
modeling with 16 viewports.  It features complete
programmability and universal CAD communications.
The Mac version includes CAD-oriented HyperCard
stacks.



version control
The management of source code, bitmaps, documents
and related files in a large software project.
Version-control software provides a database that
is used to keep track of the revisions made to a
program by all the programmers and developers
involved in it.  See configuration management.



version number
The identification of a release of software.  The
difference between Version 2.2 and 2.3 can be night
and day, since new releases not only add features,
but often correct bugs.  What's been driving you
crazy may have been fixed!

   Numbers, such as 3.1a or 3.11, often indicate a
follow-up release only to fix a bug in the previous
version, whereas 3.1 and 3.2 usually mean routine
enhancements.  Version "1.0" drives terror into the
hearts of experienced users.  The program has just
been released, and bugs are still to be uncovered.



vertical bandwidth
See vertical scan frequency.



vertical market software
Software packages that are designed for a
particular industry such as banking, insurance or
manufacturing.  Contrast with horizontal market
software.



vertical recording
A magnetic recording method that records the bits
vertically instead of horizontally, taking up less
space and providing greater storage capacity.  The
vertical recording method uses a specialized
material for the construction of the disk.



vertical redundancy checking
See VRC.



vertical refresh
See vertical scan frequency.



vertical resolution
Number of lines (rows in a matrix).  Contrast with
horizontal resolution.



vertical scaling
In multiprocessing, adding more CPUs within the
same computer system.  Contrast with horizontal
scaling.



vertical scan frequency
The number of times an entire display screen is
refreshed, or redrawn, per second.  Measured in
Hertz, display systems range from 45 to over 100Hz.
For example, VGA in the U.S. is generally 56 to
60Hz; in Europe, 70Hz and above.  TV is refreshed
60 half-frames/sec (interlaced) resulting in 30
full frames/sec.  Contrast with horizontal scan
frequency.



vertical software
See vertical market software.



VESA
(Video Electronics Standards Association)  An
organization of major PC vendors dedicated to
improving video and multimedia standards (see VESA
standards following this definition).  Address:
2150 N. 1st St., San Jose, CA 95131, 408/435-0333.



VESA Advanced Feature Connector
Also known as VAFC, it is an enhanced VGA feature
connector that uses 80-pins instead of 26 and
increases the channel up to 32 bits.  See VGA
feature connector.



VESA BIOS
A BIOS chip on a VGA display adapter that conforms
to the VESA BIOS Extension standard.



VESA BIOS Extension
Also known as VBE, it is a standard programming
interface for Super VGA adapters.  IBM set the
original VGA standard, but many vendors created
proprietary cards with higher resolutions and more
colors, all under the Super VGA umbrella.

   In Windows, applications call Windows to display
everything.  Windows then calls the display driver
to draw the screen, thus, card vendors solve their
incompatibilities by including their own display
drivers for Windows.

   In DOS, applications draw the screens
themselves.  Since vendors of DOS games and
graphics applications increasingly want to use
higher resolutions and more colors, VBE provides a
standard interface to write to, including a way to
query an adapter for its capabilities and to set
resolution and color depth.  In order to provide
this capability, a software driver, commonly called
a VESA driver, is provided by the card vendor or
the game vendor.  See UniVBE.

   As of VBE Version 2.0, this standard must be
implemented in the VGA card's ROM BIOS, not as a
software driver.  In addition, resolutions are also
selectable by pixels (640x480, 800x600, etc.), not
just mode number.  The VBE can be taken further.
Since the card can be interrogated, it is possible
to create a universal display driver that asks for
and then uses the commands of the card it is
driving.

   Most VBE modes are outlined below.  Look up PC
display modes for the complete list.


     Mode no.       Colors  Video
      (hex) Resolution     RAM used
       101  640x480   256   300K
       110  640x480   32K   600K
       111  640x480   64K   600K
       112  640x480   16M   900K

       103  800x600   256   469K
       113  800x600   32K   938K
       114  800x600   64K   938K
       115  800x600   16M  1406K

       105  1024x768  256   768K
       116  1024x768  32K  1536K
       117  1024x768  64K  1536K
       118  1024x768  16M  2304K

       107  1280x1024 256  1280K
       119  1280x1024 32K  2560K
       11A  1280x1024 64K  2560K
       11B  1280x1024 16M  3840K





VESA BIOS Extension/Audio Interface
Also known as VBE/AI, it is a standard from VESA
for sound cards.  It also allows sound cards to be
programmed using 32-bit instructions.  Like the VBE
for display adapters (see above), its goal is to
provide a standard sound card interface across all
platforms and environments.



VESA Display Data Channel
Also known as DDC, it is a standard from VESA for a
communications channel between the display adapter
and the monitor.  It requires an additional wire in
the cable.  The first level implementation provides
a unidirectional channel that lets the monitor
inform the host of its capabilities.  A second bi-
directional level allows the host to adjust the
monitor.  For example, the monitor's switch
settings could be put into a software control
panel.  The DDC is expected to gain momentum in
1995.



VESA display modes
See PC display modes.



VESA Display Power Management Signalling
Also known as DPMS, it is a standard from VESA for
signalling the monitor to switch into energy
conservation modes.  It provides for two low energy
modes: standby and suspend.



VESA driver
See VESA BIOS Extensions.



VESA/EISA
Refers to an EISA-bus motherboard or system that
contains from one to three VL-bus slots.



VESA/ISA
Refers to an ISA-bus motherboard or system that
contains from one to three VL-bus slots.



VESA local bus
See VL-bus.



VESA Media Channel
Known as the VM Channel, it is a high-speed bus
endorsed by VESA for handling digital video in a
personal computer.  It bypasses the system bus
(ISA, PCI, etc.) and provides direct connections
from video capture and videoconferencing boards to
the display adapter.



VESA modes
See VESA BIOS Extension.



VESA screen modes
See VESA BIOS Extension and PC display modes.



vesicular film
A film used to make copies of microforms.  It
contains its own developer and creates a pink
negative or positive copy when exposed to a
negative master through ultraviolet light.



VFAT
(Virtual File Allocation Table)  A file system used
in Windows for Workgroups and Windows 95.  It
provides higher-speed, 32-bit Protected Mode access
for file manipulation.  It also supports file names
up to 255 characters in length compared to DOS' 8.3
file names (name-8, extension-3).



VFW
See Video for Windows.



VGA
(Video Graphics Array)  An IBM video display
standard that originated with its PS/2 models.  VGA
has become the minimum standard for PC display.
VGA supports previous CGA and EGA modes and
requires an analog monitor.  Its highest resolution
was originally defined by IBM at 640x480 with 16
colors, but VGA vendors boosted resolution and
colors to so-called "Super VGA" resolutions.  VESA
later standardized Super VGA modes up to 1280x1024
with 16M colors.  See VESA BIOS Extension and PC
display modes.



VGA adapter
A display adapter that provides VGA resolution.
Most VGA adapters are capable of 640x480, 800x600
and 1024x768 resolutions with at least 256 colors.
Many go up to 1280x1024 with color depth to 16M
colors (true color).  Most VGA adapters today also
include graphics acceleration in order to provide
respectable scrolling and display under Windows.  A
VGA card that does not have a graphics accelerator
should not be used under Windows.  See VGA and
graphics accelerator.



VGA feature connector
A port on a VGA adapter that is used to pass clock
signals and palette information to another board in
the computer that processes video in some manner.
For example, a board that displays TV on screen may
require synchronization from the VGA adapter.  The
feature connector uses a 26-pin male connector or a
26-pin (13 per side) edge connector at the top of
the VGA board.  See VESA Advanced Feature
Connector.



VGA HC
(VGA HiColor)  A VGA board that provides 32K or 64K
colors using Tseng Labs' ET4000 chip or equivalent.



VGA pass through
A feature of a high-resolution display adapter that
couples internally with a standard VGA adapter.
High-resolution adapters in PCs typically have
drivers for Windows and major DOS applications such
as AutoCAD and WordPerfect.  When those
applications are not being used, the high-
resolution board is disabled, and regular VGA
signals are passed through to the monitor.



VHD
(Very High Density)  Floppy disk technologies that
place 20MB and more of data on a 3.5" disk.  See
Floptical.



VHF
(Very High Frequency)  The range of electromagnetic
frequencies from 30MHz to 300MHz.



VHS
A VCR format introduced by JVC in 1976 to compete
with Sony's Beta format.  VHS has become the
standard for home and industry, and Beta is now
obsolete.  SVHS (Super VHS) is a subsequent format
that improves resolution.



VHSIC
(Very High Speed Integrated Circuit)  Pronounced
"vizik."  Ultra-high-speed chips employing LSI and
VLSI technologies.



vi
(Visual Interface)  A UNIX full-screen text editor
that can be run from a terminal or the system
console.  It is a fast, programmer-oriented
utility.



video
An audio/visual playback and recording technology
used in TV.  It also refers to computer screens and
terminals.  However, there is only one TV/video
standard in the U.S., but there are dozens of
computer/video display standards.



video adapter
See video capture board, video graphics board and
display adapter.



video bandwidth
The maximum display resolution of a video screen,
measured in MHz, and calculated by horizontal x
vertical resolution x refreshes/sec.  For example,
800x600x60 = 28.8MHz.  Traditional TV studio
recording is limited to 5MHz, and TV broadcasting
is limited to 3.58Mhz.



video board
Now that full-motion digital video is deployed on
personal computers, the term "video board" can
refer to either (1) a display adapter (VGA, Super
VGA, etc.), or (2) a video capture board that
digitizes full-motion video into the computer.



video camera
A camera that takes continuous pictures and
generates a signal for display or recording.  It
captures images by breaking down the image into a
series of lines.  The U.S. and Canadian standard
(NTSC) is 525 scan lines.  Each line is scanned one
at a time, and the continuously varying intensities
of red, green and blue light across the line are
filtered out and converted into a variable signal.
Most video cameras are analog, but digital video
cameras are also available.  See digital camera.



video capture board
An expansion board that digitizes full-motion video
from a VCR, camera or other NTSC video source.  The
board may also provide digital to analog conversion
for recording onto a VCR.



video card
Same as display adapter.



Video CD
Video playback on a CD.  Developed by Matsushita,
Philips, Sony and JVC, Video CD holds 74 minutes of
VHS-quality video, including CD-quality sound.
Video CD movies are compressed using the MPEG I
method and require an MPEG decoder.  Sigma Design's
ReelMagic is one of the first Video CD boards for a
PC.

   With the addition of an adapter, Video CD can be
played on audio CD players that have a data-only
output.  It can also be played on equipped CD-I and
3DO players.  Specficiations for this format are
defined in the "White Book."



video codec
A hardware circuit that converts NTSC video into
digital code and vice versa.  It incorporates a
compression technique, such as MPEG, Indeo, Cinepak
or Video1 to reduce the amount of digital data that
is generated.

   Video codec often refers to only the compression
and decompression processing, which can be done in
software or in hardware.



video conferencing
See teleconferencing.



video controller
(1) A device that controls some kind of video
function.

(2) Same as display adapter.



Video Device Interface
See VDI.



video digitizer
Same as frame grabber.



video display board
See display adapter and video graphics board.



video display card
See display adapter and video graphics board.



video display terminal/unit
Same as video terminal.



video editing
See nonlinear video editing.



video editor
A dedicated computer that controls two or more
videotape machines.  It keeps track of frame
numbers in its own database and switches the
recording machine from playback to record.  The
video editor reads SMPTE time codes provided on
professional tape formats.



video effects
See digital video effects.



Video Electronics Standards Association
See VESA.



Video for Windows
A video driver and utilities from Microsoft for
Windows 3.1 and higher.  It supports the AVI movie
file format and three video compression methods
(Microsoft Video 1, Microsoft RLE and Intel's
Indeo).   The following utilities are included:

       VidCap   - video capture
       VidEdit  - video editor
       BitEdit  - bitmap editor
       PalEdit  - palette editor
       WaveEdit - sound editor
       Media Player - video playback

   The quality of Video for Windows playback
depends on PC performance.  It is a tradeoff
between resolution and frame speed.  At 30 frames
per second (fps), the eye perceives a totally
smooth animated sequence.  At rates below 10 fps,
the image is jerky.  Following is the typical
playback frame rate based on CPU speed and the
resolution of the video window.


             Frames per Second

               Video playback window
   CPU       160x120  320x240  640x480

  486/25       30       15        1
  486/66       30       30       10
  Pentium      30       30       20





Video Graphics Array
See VGA.



video graphics board
A video display board that generates text and
graphics and accepts video from a camera or VCR.
Truevision's Targa board and Vision Technologies
Vision board are examples.

   The terms video graphics board and video display
board sound alike, but video display boards are
generally VGA-only display adapters and do not
handle NTSC video.



video overlay card
(1) A graphics controller that accepts NTSC video
from an analog video source, such as a TV tuner or
VCR, and displays it on screen combined with the
regular display adapter output.

(2) A graphics controller that decompresses digital
video and sends the output to the display adapter.



video port
A socket on a computer used to connect a monitor.
On a PC, the standard video port is a 15-pin VGA
connector.  See VGA.



video RAM
Also called VRAM, it is a type of memory in a
display adapter that is used to create the image
that appears on the video screen.  It uses dual-
ported memory, which allows simultaneous reads and
writes and is faster than dynamic RAM (DRAM).



video teleconferencing
See videoconferencing.



video terminal
A data entry device that uses a keyboard for input
and a display screen for output.  Although the
display screen resembles a TV, it usually does not
accept TV/video signals.



Video Toaster
A popular video production system for the Amiga
computer from NewTek, Inc., Topeka, KS.  The
Toaster includes hardware and software that
provides video functions such as digital effects,
character generation and 3-D animation.  The
Toaster/Amiga combination is considered the most
affordable broadcast-quality video system on the
market.



video window
The display of full-motion video (TV) in an
independent window on a computer screen.



Video1
A video compression/decompression algorithm from
Microsoft and Media Vision that is used to compress
movie files.



videoconferencing
See teleconferencing.



videodisc
An optical disc used for full-motion video.  See
LaserDisc and Video CD.



videographer
A person involved in the production of video
material.



videotape
A magnetic tape used for recording full-animation
video images.  The most widely used videotape
format is the 1/2" wide VHS cassette.  VHS has all
but obsoleted earlier videotape formats for home
and commercial use.



videotex
An interactive information technology for home
shopping, banking, news, weather and e-mail.  It is
delivered by telephone line to a subscriber's TV
through a decoder box and attached keyboard.
Information is broadcast and stored in the decoder
as predefined frames that are retrieved by menu.
Videotex delivers simple graphics and limited
animation.  Used in several countries worldwide, it
has yet to catch on in the U.S.



view
(1) To display and look at data on screen.

(2) In relational database management, a special
display of data, created as needed.  A view
temporarily ties two or more files together so that
the combined files can be displayed, printed or
queried; for example, customers and orders or
vendors and purchases.  Fields to be included are
specified by the user.  The original files are not
permanently linked or altered; however, if the
system allows editing, the data in the original
files will be changed.



Viewdata
The British term for videotex.



viewer
See file viewer.



viewport
(1) In the Macintosh, the entire scrollable region
of data that is viewed through a window.

(2) Same as window.



VIM
(Vendor Independent Messaging Interface)  A
programming interface developed by Lotus, Novell,
IBM, Apple, Borland, MCI, WordPerfect and Oracle.
In order to enable an application to send and
receive mail over a VIM-compliant messaging system
such as cc:Mail, programmers write to the VIM
interface.



VINES
(VIrtual NEtworking System)  A UNIX System V-based
network operating system from Banyan Systems Inc.,
that runs on DOS and OS/2-based servers.  It
provides internetworking of PCs, minis, mainframes
and other computer resources providing information
sharing across organizations of unlimited size.

   Incorporating mainframe-like security with a
global directory service called Streettalk, VINES
allows access to all network users and resources.
Options include printer sharing, e-mail, remote PC
dial-in, bridges and gateways.



virtual
An adjective applied to almost anything today that
expresses a condition without boundaries or
constraints.



Virtual 8086 Mode
An operational mode in Intel 386s and up that
allows it to perform as multiple 8086 CPUs.  Under
direction of a control program, each virtual
machine runs as a stand-alone 8086 running its own
operating system and applications, thus DOS, UNIX
and other operating systems can be running
simultaneously.  All virtual machines are
multitasked together.

   This mode divides up the computer into multiple
address spaces and maintains virtual registers for
each virtual machine.  This is not the same as the
386's virtual memory mode, which extends main
memory to disk.



virtual circuit
The resulting pathway created between two devices
communicating with each other in a switched
communications system.  A message from New York to
Los Angeles may actually start in New York and go
through Atlanta, St. Louis, Denver and Phoenix
before it winds up in Los Angeles.

   It can also be confined to smaller geography,
say within a building or campus, in which case the
virtual circuit traverses some number of switches,
hubs and other network devices.  See PVC and SVC.



virtual desktop
An infinitely-large desktop, which is provided
either by a virtual screen capability or a shell
program that enhances the user interface.



virtual device
See virtual peripheral and VxD.



virtual device driver
See VxD.



Virtual Device Interface
See VDI.



virtual disk
Same as RAM disk.



Virtual DOS Machine
See VDM.



virtual image
In graphics, the complete graphic image stored in
memory, not just the part of it that is displayed
at the current time.



virtual machine
(1) A computer that runs an operating system that
can host other operating systems or multiple copies
of itself.  Each operating system runs its own set
of applications timeshared equally or in some
priority with all the other operating systems.
Computers can be built with hardware circuits that
support a virtual machine environment; for example,
the Virtual 8086 Mode in the PC starting with the
386.  See VM and Virtual 8086 Mode.

(2) A computer that has built-in virtual memory
capability.



Virtual Machine Manager
See VMM.



virtual memory
Simulating more memory than actually exists,
allowing the computer to run larger programs or
more programs concurrently.  It breaks up the
program into small segments, called pages, and
brings as many pages into memory that fit into a
reserved area for that program.  When additional
pages are required, it makes room for them by
swapping them to disk.  It keeps track of pages
that have been modified, so that they can be
retrieved when needed again.

   If a program's logic points back and forth to
opposite ends of the program, excessive disk
accesses, or thrashing, can slow down execution.

   Virtual memory can be implemented in software
only, but efficient operation requires virtual
memory hardware.  Programs sometimes claim virtual
memory capability by bringing additional parts of
the program in as needed; however, true virtual
memory is a hardware and operating system
implementation that works with all applications.



virtual monitor
In the Macintosh, the ability to dynamically
configure to any monitor type and to use multiple
monitors of different types including displaying
the same object across two or more screens.



virtual network
An interconnected group of networks (an internet)
that appear as one large network to the user.
Optionally, or perhaps ideally, a virtual network
can be centrally managed and controlled.

   Banyan Systems, creator of VINES, which stands
for VIrtual NEtworking System, defines virtual
networking as "the ability for users to
transparently communicate locally and remotely
across similar and dissimilar networks through a
simple and consistent user interface."



virtual operating system
An operating system that can host other operating
systems.  See virtual machine.



virtual peripheral
A peripheral device simulated by the operating
system.



virtual printer
A simulated printer.  If a program is ready to
print, but all printers are busy, the operating
system will transfer the printer output to disk and
keep it there until a printer becomes available.



virtual private network
See VPN.  Remember... try the acronymn first!



virtual processing
A parallel processing technique that simulates a
processor for applications that require a processor
for each data element.  It creates processors for
data elements above and beyond the number of
processors available.



virtual processor
A simulated processor in a virtual processing
system.



virtual reality
An artificial reality that projects the user into a
3-D space generated by the computer.  It requires
the use of a unique kind of glove, called a data
glove, and stereoscopic goggles, which are both
wired to the computer.  The glove lets users point
to and manipulate computer-generated objects that
are displayed on tiny monitors inside the goggles.

   Virtual reality, or VR, can be used to create an
illusion of any reality or imagined reality and is
used both for entertainment and training.  See
cyberspace.



virtual route
Same as virtual circuit.



virtual screen
A viewing area that is larger than the physical
borders of the screen.  It allows the user to
scroll very large documents or multiple documents
side by side by moving the mouse pointer beyond the
edge of the screen.  For example, you might look
through an 800x600 screen resolution into a
2048x2048 virtual screen.



virtual storage
Same as virtual memory.



virtual terminal
Terminal emulation that allows access to a foreign
system.  Often refers to a personal computer
gaining access to a mini or mainframe.



virtual toolkit
Development software that creates programs for
several computer environments.  Its output may
require additional conversions or translations to
produce executable programs.



virtualize
(1) To activate a program in virtual memory.

(2) To create a virtual screen.



virus
Software used to infect a computer.  After the
virus code is written, it is buried within an
existing program.  Once that program is executed,
the virus code is activated and attaches copies of
itself to other programs in the system.  Infected
programs copy the virus to other programs.

   The effect of the virus may be a simple prank
that pops up a message on screen out of the blue or
the actual destruction of programs and data.

   A virus cannot be attached to data.  It must be
attached to a runnable program that is downloaded
into or installed in the computer.  The virus-
attached program must be executed in order to
activate the virus.  See polymorphic virus, stealth
virus and worm.


               Be Careful Out There!
Before you run a shareware, public domain or
freeware program, check it with a virus detection
program first!





virus signature
The binary pattern of the machine code of a
particular virus.  Antivirus programs use virus
signatures for fast detection of known viruses.



VIS
(Voice Information Service)  A variety of voice
processing service applications.



visa
See VESA.



ViSCA
(VIdeo System Control Architecture)  A Sony
protocol for synchronized control of multiple video
peripherals.  ViSCA is the software interface.
Control-L is the hardware interface.  A ViSCA-
compatible VCR can be controlled directly by video
capture software.



VisiCalc
The first electronic spreadsheet.  It was
introduced in 1978 for the Apple II.  Conceived by
Dan Bricklin, a Harvard student, and programmed by
a friend, Bob Frankston, it became a major success.
It launched an industry and was almost entirely
responsible for the Apple II being used in
business.  Thousands of $3,000 Apples were bought
to run the $150 VisiCalc.

   VisiCalc was a command-driven program that was
followed by SuperCalc, MultiPlan, Lotus 1-2-3 and a
host of others, each improving the user interface.
Spreadsheets have also been implemented on minis
and mainframes.  It all started with VisiCalc.



Visual AppBuilder
See AppWare.



Visual Basic
A version of BASIC from Microsoft specialized for
developing Windows applications.  It is similar to
Microsoft's QuickBASIC, but is not 100% compatible
with it.  User interfaces are developed by dragging
objects from the Visual Basic Toolbox onto the
application form.

   Visual Basic has become a very popular Windows
programming language and is often used to write
client front ends for client/server applications.
Visual Basic for Applications (VBA), a subset of
Visual Basic, is a common macro language that
Microsoft includes with many of its applications.



Visual C++
A C and C++ development system for DOS and Windows
applications from Microsoft.  It includes Visual
Workbench, an integrated Windows-based development
environment and Version 2.0 of the Microsoft
Foundation Class Library (MFC), which provide a
basic framework of object-oriented code to build an
application upon.

   Introduced in 1993, the Standard Edition of
Visual C++ replaces QuickC for Windows and the
Professional Edition includes the Windows SDK and
replaces Microsoft C/C++ 7.0.



visual programming
Developing programs with tools that allow menus,
buttons and other graphics elements to be selected
from a palette and drawn and built on screen.  It
may include developing source code by creating
and/or interacting with flow charts that
graphically display the logic paths and associated
code.



Visual Workbench
See Visual C++.



visualization
In computer graphics, the converting of numeric
data into picture form to allow humans to recognize
patterns that are difficult to identify in numeric
form.  It is used especially in research
situations, both theoretical and practical.



VL-bus
(VESA Local-BUS)  A local bus for PCs standardized
by VESA that provides a high-speed data path
between the CPU and peripherals (video, disk,
network, etc.).  Up to three VL-bus slots can be
placed onto the motherboard.  See local bus.

   The VL-bus runs at speeds up to 40MHz or up to
66MHz for controllers built directly on the
motherboard.  It is currently a 32-bit bus with 64-
bit capability forthcoming to handle the Pentium
CPU.  The VL-bus expansion slot uses one 32-bit
Micro Channel slot placed adjacent to the standard
ISA, EISA or Micro Channel slot, allowing vendors
to design boards that use only the local bus or
both buses at the same time.  VL-bus also supports
bus mastering.



VLB
See VL-bus.



VLF
(Very Low Frequency)  See low radiation.



VLSI
(1) (Very Large Scale Integration)  Between 100,000
and one million transistors on a chip.  See SSI,
MSI, LSI and ULSI.

(2) (VLSI Technology, Inc., Tempe, AZ)  A designer
and manufacturer of custom chips.



VM
(1) (Virtual Machine)  An IBM mainframe operating
system, originally developed by its customers and
eventually adopted as an IBM system product
(VM/SP).  It can run multiple operating systems
within the computer at the same time, each one
running its own programs.  CMS (Conversational
Monitor System) provides VM's interactive
capability.

(2) (Virtual Machine)  One instance of a virtual
machine in a virtual machine environment.  See
virtual machine.



VM/386
(Virtual Machine/386)  A multiuser operating system
for 386s and up from IGC Corporation, San Jose, CA.
It allows one PC to serve as a central computer to
multiple workstations, each capable of running
several DOS and Windows programs simultaneously.



VM Channel
See VESA Media Channel.



VM/SP
See VM.



VMEbus
(VersaModule Eurocard bus)  A 32-bit bus developed
by Motorola, Signetics, Mostek and Thompson CSF.
It is widely used in industrial, commercial and
military applications with over 300 manufacturers
of VMEbus products worldwide.  VME64 is an expanded
version that provides 64-bit data transfer and
addressing.



VMM
(1) (Virtual Machine Manager)  The underlying
operating system component of Windows.  It manages
the computer's memory and virtual machines.  The
services in the VMM are not directly called by
Windows applictions, but are accessible by virtual
device drivers (VxDs).

(2) (Virtual Memory Manager)  The software that
manages virtual memory in a computer.



VMS
(1) (Virtual Memory System)  A multiuser,
multitasking, virtual memory operating system for
the VAX series from Digital.  VMS applications will
run on any VAX from the MicroVAX to the largest
VAX.

(2) (Voice Messaging System)  See voice mail.



VMTP
(Virtual Message Transaction Protocol)  A datagram
communications protocol that provides efficient and
reliable transmission across networks.



voice
See MIDI voices.



voice channel
A transmission channel or subchannel that carries
human voice.



voice coil
A type of motor used to move the access arm of a
disk drive in very small increments.  Like the
voice coil of a speaker, the amount of current
determines the amount of movement.  Contrast with
stepper motor, which works in fixed increments.



voice grade
Refers to the bandwidth required to transmit human
voice, which is usually about 4,000Hz.



voice information service
See VIS.



voice mail
A computerized telephone answering system that
digitizes incoming voice messages and stores them
on disk.  It usually provides auto attendant
capability, which uses prerecorded messages to
route the caller to the appropriate person,
department or mail box.



voice menu
A series of options and the corresponding number to
press that are announced to the listener in an
audiotex or voice processing system.



voice messaging
Using voice mail as an alternative to electronic
mail, in which voice messages are intentionally
recorded, not because the recipient was not
available.



voice processing
The computerized handling of voice, which includes
voice store and forward, voice response, voice
recognition and text to speech technologies.



voice recognition
The conversion of spoken words into computer text.
Speech is first digitized and then matched against
a dictionary of coded waveforms.  The matches are
converted into text as if the words were typed on
the keyboard.

   Speaker-dependent systems must be trained before
using, by taking samples of actual words from the
person who will use it.  Speaker-independent
systems can recognize limited vocabularies such as
numeric digits and a handful of words.  In the
telephone companies, these systems will begin to
replace the human operator for services, such as
collect and credit card calls, for example.

   In the future, voice recognition systems will be
able to understand large vocabularies from just
about anybody; however, it could be well past the
turn of the century before voice recognition is
part of every computer system.



voice response
The generation of voice output by computer.  It
provides pre-recorded information either with or
without selection by the caller.  Interactive voice
response allows interactive manipulation of a
database.  See audiotex.



voice store and forward
The technology behind voice mail and messaging
systems.  Human voice is digitized, stored in the
computer, routed to the recipient's mailbox and
retrieved by the user when required.



volatile memory
A memory that does not hold its contents without
power.  A computer's main memory, made up of
dynamic RAM or static RAM chips, loses its content
immediately upon loss of power.



volt
A unit of measurement of force, or pressure, in an
electrical circuit.  The common voltage of an AC
power line is 120 volts of alternating current
(alternating directions).  Common voltages within a
computer are from 5 to 12 volts of direct current
(one direction only).



volt-amps
The measurement of electrical usage that is
computed by multiplying volts times amps.  See
watt.



voltage regulator
A device used to maintain a level amount of voltage
in the electrical line.  Contrast with surge
suppressor, which filters out excessive amounts of
current, and contrast with UPS, which provides
backup power in the event of a power failure.



volume
(1) A physical storage unit, such as a hard disk,
floppy disk, disk cartridge or reel of tape.

(2) A logical storage unit, which is a part of one
physical drive or one that spans several physical
drives.



volume label
(1) A name assigned to a disk (usually optional).

(2) An identifying stick-on label attached to the
outside of a tape reel or disk cartridge.

(3) See header label.



von Neumann architecture
The sequential nature of computers: an instruction
is analyzed, data is processed, the next
instruction is analyzed, and so on.  Hungarian-born
John von Neumann (1903-1957), an internationally
renowned mathematician, promoted the stored program
concept in the 1940s.



VOS
An operating system used in Stratus computers.  FTX
is Stratus' UNIX operating system.



voxel
(VOlume piXEL)  A three-dimensional pixel.  A voxel
represents a quantity of 3-D data just as a pixel
represents a point or cluster of points in 2-D
data.  It is used in scientific and medical
applications that process 3-D images.



VP/ix
See SCO VP/ix.



VP Planner
A Lotus-compatible relational spreadsheet from
Paperback Software.  In 1991, it was taken off the
market due to settlement of Lotus' copyright
lawsuit.



VP ratio
(Virtual Processor ratio)  The number of virtual
processors that a physical processor is simulating.



VPC
(Virtual Processor Complex)  An IBM mainframe
multiprocessing that uses several computers under
tight central control.



VPN
(Virtual Private Network)  A wide area
communications network provided by a common carrier
that provides what seems like dedicated lines when
used, but backbone trunks are shared among all
customers as in a public network.  It allows a
private network to be configured within a public
network.  See PVC.



VPS
(Vectors Per Second)  The measurement of the speed
of a vector or array processor.



VR
See virtual reality.



Vr4400
A CPU chip manufactured by NEC Technologies, Inc.,
that is based on the MIPS R4400 architecture.  It
is being used in PCs that run Windows NT.  Initial
models run at 150MHz internally.



VRAM
See video RAM.



VRC
(Vertical Redundancy Check)  An error checking
method that generates and tests a parity bit for
each byte of data that is moved or transmitted.



VS
(1) (Virtual Storage)  Same as virtual memory.

(2) (Virtual Storage)  A family of minicomputers
from Wang introduced in 1977, which use virtual
memory techniques.



VSAM
(Virtual Storage Access Method)  An IBM access
method for storing data, widely used in IBM
mainframes.  It uses the B+tree method for
organizing data.



VSAT
(Very Small Aperture satellite Terminal)  A small
earth station for satellite transmission that
handles up to 56 Kbits/sec of digital transmission.
VSATs that handle the T1 data rate (up to 1.544
Mbits/sec) are called TSATs.



VSE
(Disk Operating System/Virtual Storage Extended)
An IBM multiuser, multitasking operating system
that typically runs on IBM's 43xx series.  It used
to be called DOS, but due to the abundance of DOS
PCs, it is now referred to as VSE.



VSX
(Verification Suite for X/Open)  A testing
procedure from X/Open that verifies compliance with
their endorsed standards.  VSX3 has over 5,500
tests for compliance with XPG3.



VT100, 200, 300
A series of asynchronous display terminals from
Digital for its PDP and VAX computers.  Available
in text and graphics models in both monochrome and
color.



VTAM
(Virtual Telecommunications Access Method)  Also
called ACF/VTAM (Advanced Communications
Function/VTAM), software that controls
communications in an IBM SNA environment.  It
usually resides in the mainframe under MVS or VM,
but may be offloaded into a front end processor
that is tightly coupled to the mainframe.  It
supports a wide variety of network protocols,
including SDLC and Token Ring.  VTAM can be thought
of as the network operating system of SNA.



VTOC
(Volume Table Of Contents)  A list of files on a
disk.  The VTOC is the mainframe counterpart to the
FAT table on a PC.



VTR
(VideoTape Recorder)  A video recording and
playback machine that uses reels of magnetic tape.
Contrast with VCR, which uses tape cassettes.



VUE
See HP-VUE.



VUP
(VAX Unit of Performance)  A unit of measurement
equal to the performance of the VAX 11/780, the
first VAX machine.



VxD
(Virtual Device Driver)  A special type of Windows
driver for 386 Enhanced Mode.  VxDs run at the most
priviledged CPU mode (ring 0) and allow low-level
interaction with the hardware and internal Windows
functions, such as memory management.  WIN386.EXE,
the 386 Enhanced Mode kernel of Windows, is itself
made up of VxDs.



 W32
See Tseng Labs.



W5086
A Weitek chip set that accelerates graphics
performance.



WAA
(Wide Area Adapter)  Any of a variety of ports or
adapters that connect to a wide area network (WAN),
including RS-232, RS-422 and V.35.



Wabi
(Windows ABI)  Software from SunSoft that emulates
Windows applications under UNIX by converting the
calls made by Windows applications into X Window
calls.  Since it executes native code, it runs
Windows applications at the same or higher
performance level than a Windows machine.  Wabi is
an option for Sun's Solaris environment as well as
for OEM products.



wafer
(1) The base material in chip making.  It is a
slice, approx. 1/30" thick, from a salami-like
silicon crystal from 3 to 6" in diameter.  The
wafer goes through a series of photomasking,
etching and implantation steps.  See chip.

(2) A small, continuous-loop magnetic tape
cartridge that is used for the storage of data.



wafer scale integration
The evolution in semiconductor technology that
builds a gigantic circuit on an entire wafer.  Just
as the integrated circuit eliminated cutting apart
thousands of transistors from the wafer only to
wire them back again on circuit boards, wafer scale
integration eliminates cutting apart the chips.
All the circuits for an entire computer are
designed onto one super-sized chip.

   Thus far, wafer scale integration has not come
to fruition (see Trilogy); however, the multichip
module (MCM), in which several chips are connected
closely together in a single package, is expected
to be widely used instead.



WAIS
(Wide Area Information Server)  A database on the
Internet that contains indexes to documents that
reside on the Internet.  Using the Z39.50 query
language, text files can be searched based on key
words.

   Information resources on the Internet are called
"sources."  A directory of WAIS servers and sources
is avalable from Thinking Machines Corporation,
Cambridge, MA, at address quake.think.com.  See
Archie and Gopher.



wait state
The time spent waiting for an operation to take
place.  It may refer to a variable length of time a
program has to wait before it can be processed, or
to a fixed duration of time, such as a machine
cycle.

   When memory is too slow to respond to the CPU's
request for it, wait states are introduced until
the memory can catch up.



wallpaper
A pattern or picture used to represent the desktop
surface (screen background) in a graphical user
interface.  GUIs comes with several wallpaper
choices, and third-party wallpaper files are
available.  You can also scan in your favorite
picture and make it wallpaper.

   If you wonder why you cover a desktop with
wallpaper, don't.  Very little makes sense in this
industry, why should this?



WAN
(Wide Area Network)  A communications network that
covers a wide geographic area, such as state or
country.  A LAN (local area network) is contained
within a building or complex, and a MAN
(metropolitan area network) generally covers a city
or suburb.  Following are the typical WAN
networking technologies and services available.

                   WAN SERVICES

     Non-switched

     Analog private line
     Digital private line (DDS)
     Fractional T1 private line
     T1 private line
     T3 private line
     Frame relay
     ATM


     Switched

     Dial-up via modem
     ISDN
     Packet switched (X.25)
     Frame relay
     SMDS
     ATM





WAN analyzer
See network analyzer.



wand
A hand-held optical reader used to read typewritten
fonts, printed fonts, OCR fonts and bar codes.  The
wand is waved over each line of characters or codes
in a single pass.



Wang Labs
(Wang Laboratories, Inc., Lowell, MA)  A computer
manufacturer and applications developer.  Founded
in 1951 by Dr. An Wang, the company specialized in
electronic devices.  Its desktop calculator became
a standard in the late 1960s.

   In the 1970s, Wang introduced various systems
that later evolved into the WPS word processors and
the VS minicomputer line.  By 1978, it was North
America's largest supplier of small business
computers and the world's largest supplier of CRT-
based word processors.  Throughout the 1980s, Wang
developed integrated voice and data networks and
imaging systems.  Its plan for the 1990s is to
continue enhancing its VS line while specializing
in software and services for the client/server
market.

    Dr. Wang came from China in 1945 to study
applied physics at Harvard.  Six years later, he
started Wang Labs.  In 1988, two years before he
died, he was inducted into the National Inventors
Hall of Fame for his 1948 invention of a pulse
transfer device that let magnetic cores be used for
computer memory.  The Hall of Fame has recognized
an elite group including Edison, Pasteur and Bell.



Wangnet
A broadband LAN from Wang that handles data, voice
and video.



warm boot
Restarting the computer by performing a reset
operation (pressing reset, Ctrl-Alt-Del, etc.).
See boot, cold boot and clean boot.



warm start
Same as warm boot.



Warnier-Orr diagram
A graphic charting technique used in software
engineering for system analysis and design.



WARP
(1) See OS/2 Warp.

(2) A parallel processor developed at Carnegie-
Mellon University that was the predecessor of
iWARP.



Watcom compilers
C and FORTRAN compilers for PCs from Watcom
International Corporation, Waterloo, Ontario, noted
for generating fast, compact code.  WATCOM C/386
was the first 32-bit compiler for extended DOS,
Windows, OS/2 2.0 and AutoCAD ADS and ADI
applications.  The corporate mission is to provide
advanced compilers for x86 environments.  Watcom is
a subsidiary of Powersoft Corporation, makers of
PowerBuilder.



Watcom SQL
A relational database management system (DBMS) for
DOS, Windows, Windows NT, NetWare and OS/2 from
Watcom International Corporation, Waterloo,
Ontario.  Watcom SQL is also packaged with
Powersoft's PowerBuilder products.



watt
The measurement of electrical power.  One watt is
one ampere of current flowing at one volt.  Watts
are typically rated as AMPS x VOLTS; however, AMPS
x VOLTS, or VOLT-AMP (V-A) ratings and watts are
only equivalent when powering devices that absorb
all the energy such as electric heating coils or
incandescent light bulbs.  With computer power
supplies, the actual watt rating is only 60 to 70%
of the VOLT-AMP rating.



WAV
A Windows sound file, which uses the .WAV
extension.  Wave files take up a lot of disk space.
Depending on sampling frequency and rate, one
minute of audio, without compression, can take from
644KB to 5MB.  See sound card.



wave
The shape of radiated energy.  All radio signals,
light rays, x-rays, and cosmic rays radiate an
energy that looks likes rippling waves.  To
visualize waves, take a piece of paper and start
drawing an up and down line very fast while pulling
the paper perpendicular to the line.



wave file
See WAV.



wave table synthesis
A MIDI technique for creating musical sounds by
storing digitized samples of the actual
instruments.  It provides more realistic sound than
the FM synthesis method, which generates the sound
waves entirely via electronic circuits.  The more
notes sampled in the wave table method, the better
the resulting sound recreation.



waveform
The pattern of a particular sound wave or other
electronic signal in analog form.



waveform synthesis
Same as wave table synthesis.



waveguide
A rectangular, circular or elliptical tube through
which radio waves are transmitted.



wavelength
The distance between crests of a wave, computed by
speed divided by frequency (speed / Hz).
Wavelength in meters of electromagnetic waves
equals 300,000,000 / Hz.  Wavelength in meters for
sound travelling through the air equals 335 / Hz.



wavelength-division multiplexing
See WDM.



ways
See WAIS.



WDM
(Wavelength-Division Multiplexing)  A high-speed
optical fiber transmission technique that carries
multiple signals, each within its own wavelength
(color) of light.



weak typing
Programming languages that allow different types of
data to be moved freely among data structures, as
is found in Smalltalk and other earlier object-
oriented languages.



Web
See Worldwide Web.



Weitek coprocessor
A high-performance math coprocessor from Weitek
Corporation.  Since 1981, Weitek has been making
coprocessors for CAD and graphics workstations.  In
order to use a coprocessor, the software must be
written to activate it.



well behaved
Refers to programs that do not deviate from a
standard.



well mannered
Same as well behaved.



Wellfleet
See Bay Networks.



wetware
A biological system.  It typically refers to the
human brain and nervous system.



WFW
See Windows for Workgroups.



what if?
Using a spreadsheet as a planning tool.  When new
data is entered, results are calculated based upon
the formulas.  Assumptions can be plugged in that
ripple through to the bottom line.  For example,
"what if hourly pay is increased $2?"  "What if
interest rates are lowered a half a point?"



Whetstones
A benchmark program that tests floating point
operations.  Results are expressed in Whetstones
per second.  Whetstone I tests 32-bit, and
Whetstone II tests 64-bit operations.  See
Dhrystones.



White Book
The documentation for the technical specification
of Video CDs.  See Video CD.



white noise
Same as Gaussian noise.



white pages
A directory list.  See DIB.



whiteboard
The electronic equivalent of chalk and blackboard.
Whiteboards allow participants across a network to
simultaneously view one or more users drawing on
the computer.



WHOIS
An Internet utility used to query a host and find
out if a certain user is registered on that system.



wide area adapter
See WAA.



Wide Area Information Server
See WAIS.



wide area network
See WAN.



widget set
A group of screen structures (menu, button, scroll
bar, etc.) provided in a graphical interface.



widow & orphan
A widow is the last line of a paragraph that
appears alone at the top of the next page, and an
orphan is the first line of a paragraph that
appears alone at the bottom of a page.  Widow and
orphan settings are usually set for a minimum of
two lines.



width table
A list of horizontal measurements for each
character in a font, used by word processing and
desktop publishing programs.



wild cards
Symbols used to represent any value when naming
files.  In DOS and UNIX, the asterisk (*)
represents any name, and the question mark (?)
represents any single character.  See DOS wild
cards.



wimp interface
(Windows, Icons, Menus and a Pointing device)  Same
as GUI.



Win abc's
The Windows abc's and the Windows entries that
follow provide a brief overview of the Windows
environment and how to perform basic functions.

   To learn more about Windows, Windows provides an
online help system that covers most Windows
operations (press F1 after loading Windows).
However, a good book on the subject is also very
worthwhile.  If you want to become an accomplished
Windows user, read "Windows 3.1 Secrets" by Brian
Livingston, InfoWorld's renowned Windows columnist.
It's published by IDG Books (ISBN 1-878058-43-6).


                 What's a Window?
A window is a rectangular area on screen surrounded
by a window frame with a title centered at the top.
When you launch a Windows application, it is
displayed in its own window.  A major Windows
feature is that you can have multiple windows
active at the same time.  The maximum number
depends on how much memory you have in your
computer.  You get an "Out of memory" message when
you try to launch another application, and there's
no room for another window.

         windowĿ
                                   
  windowĿ   
                                  
               windowĿ     
                                
                                
                             
  Ĵ            
                            
                

   You can change the appearance of a window by
making it smaller or larger.  On large screens, you
can keep them side by side.  On smaller screens,
you can overlap them or have one window take up the
entire screen.  The latter is called "maximizing"
the window.

   DOS applications can also run under Windows, and
they either run full screen as they always have,
or, unless you use a 286, they can run in a window
side by side with Windows applications.


              How to Talk to Windows
Windows operations are performed by selecting
options from menus and by pressing on-screen
buttons, as follows:

 1. DOUBLE CLICK
    Double clicking the mouse causes some action
    to take place.  For example, to launch an
    application, in Program Manager, point to the
    icon of the program you want to run and press
    the mouse button twice in rapid succession.

 2. CLICK ON A MENU
    To select a menu operation, move the mouse
    pointer to a menu and click once.  For
    example, to open a document within your
    application, click once on the word "File"
    on the menu bar (top left).  A menu will drop
    down offering you several options.  Point to
    and click on "Open."

 3. CLICK ON A BUTTON
    To "push" an on-screen button, move the mouse
    pointer onto the button and click once.

 4. DRAG AND DROP
    To move or resize an object, move the mouse
    pointer to an icon or window frame and lock
    onto it by holding down the mouse button.
    Then move the object to a new location and
    release the mouse button when finished.

    For example, to resize a window, move the
    pointer to the bottom right corner, watching
    for the pointer to change to a slanted double
    arrow.  Click the mouse button and move the
    mouse.  Let go of the mouse when the corner is
    in the new location.

 3. THE KEYBOARD
    There are keyboard alternatives to all mouse
    movements.  See Win Keyboard commands.


          Program Manager & File Manager
The two major Windows components are Program
Manager and File Manager.  Program Manager is the
launching pad for your applications.  File Manager
lets you copy and delete files and organize your
directories.  See Win Program Manager and Win File
Manager.



Win Change window appearance
In Windows, you can move, resize and overlap
windows on screen.


          HOW TO CHANGE WINDOW APPEARANCE


  Move Window Around Screen
    Point to window title bar and drag.


  Change One Side of a Window
    Point to a side.  When pointer changes to a
    double arrow, drag to new location.


  Change Two Sides of a Window
    Point to a corner.  When pointer changes to an
    angled double arrow, drag to new location.


  Turn Window into an Icon on the Desktop
    Click once on   Ŀ
    Minimize button    (top right corner)
                    


  Turn Desktop Icon back into a Window (Maximize)
    Double click on icon on desktop.  This is
    outside of the Program Manager window frame.


  Make Window Cover Entire Screen
    Click once on   Ŀ
    Maximize button    (top right corner)
                    


  Restore Window to Previous Size
    Click once on   Ŀ
    Restore button     (top right corner)
                      
                    



Win Clipboard
See Win Copy between windows.



Win Copy between windows
To copy text or an image from one window to
another, highlight the text or select the image by
whatever selection method is used in your program.
Then select COPY from the EDIT menu.  Your selected
item will be copied into the clipboard.  Then
switch to your destination window.  For text,
locate the cursor where you want the text or image
to appear.  Then select PASTE from the EDIT menu.

   To move an object from one window to another,
select CUT from the EDIT menu.  Then paste the
object into the destination window as in the above
example.

   To copy or move without a mouse, see Win
Keyboard commands.

   To copy or move data from a DOS window, see Win
Running DOS programs



Win File Manager
File Manager (FileMan icon) lets you create
directories and copy, move and delete files.  It
displays your disk directories in a graphical tree.
If you're not familiar with the hierachical
directory structure of a disk, see DOS directories.

   Copying and moving files is performed by
dragging file icons to a destination drive or
directory.  Using File Manager is easy, and help is
online (pressing F1 calls help).

   Like all windows, you can keep File Manager open
during your Windows session.  However, each active
window takes up memory and other resources, so you
may want to close it when you're done with it.


                  HOW TO DO BASIC
                   FILE MANAGER
                    OPERATIONS

  Create directory
    Click once on icon of directory to which the
    new directory will be attached, and select
    CREATE DIRECTORY from the FILE menu.


  Delete directory
    Click once on directory icon and select DELETE
    from the FILE menu.


  Switch Drives
    Click once on the drive icon.


  Display Directory Contents
    Double click on directory icon.


  Copy File on Same Drive
    Hold Ctrl down, drag file icon and drop on
    directory icon.


  Copy File to Another Drive
    Drag file icon and drop on drive icon.


  Move File on Same Drive
    Drag file icon and drop on directory icon.


  Move File to Another Drive
    Hold Alt down, drag file icon and drop on
    drive icon.


  Select Multiple Files
    Hold Ctrl down and click on file names.


               What's the [..] Mean?
The strange looking double dot symbol refers to the
directory one level higher than the directories
currently displayed.  Double click on it to go back
one level in the directory hierarchy.


            Lonely for the DOS Prompt?
If you are an experienced DOS user, you can use
familiar DOS commands for file manipulation.  To
get the DOS prompt, double click on the DOS prompt
icon in the Main group window in Program Manager.
The DOS prompt becomes another active application
to Windows.

   When finished, you can keep the DOS prompt
active and go to another window by pressing Alt-
Tab, or you can end the DOS prompt session by
typing exit.



Win Keyboard commands
Following are the ways to command Windows without a
mouse:

                KEYBOARD COMMANDS
 MENUSĿ
  All menus are selectable by pressing Alt     
  and the UNDERLINED letter of the menu title. 
  For example, Alt-F for File menu.            
                                               
  MENU OPTIONS                                 
  All menu options are selectable by pressing  
  the UNDERLINED letter of thier name.         
  Most of the time, it is the first letter.    
  However, if two menu options start with the  
  same letter, one of them will use a letter in
  the middle of the name as a keyboard command.
                                               
  CANCEL MENU  Esc                             
                                               
  HELP MENU  F1                                
                                               
 START/STOPĴ
  LAUNCH APPLICATION FROM ICON  Enter          
  CLOSE WINDOW  Alt-F4  or  Alt-spacebar, C.   
                                               
 SWITCH/CHANGE WINDOWSĴ
  SWITCH BETWEEN ALL WINDOWS  Alt-Tab-Tab...   
  SWITCH BETWEEN LAST TWO  Alt-Tab             
  DISPLAY TASK LIST  Ctrl-Esc                  
  CYCLE TO ICONS ON DESKTOP  Alt-Tab-Tab...    
  SWITCH BETWEEN GROUP WINDOWS  Ctrl-Tab       
  SWITCH BETWEEN ICONS  Arrow keys             
  MOVE WINDOW  Alt-spacebar, M.  Cursor to new 
   location and press Enter.                   
  RESIZE WINDOW  Alt-spacebar, S.  Cursor to   
   new size and press Enter.                   
                                               
 MINIMIZE/MAXIMIZEĴ
  DISPLAY CONTROL MENU  Alt-spacebar           
  MAXIMIZE  Alt-spacebar  X                    
  MINIMIZE  Alt-spacebar  N                    
                                               
 CLIPBOARDĴ
  COPY SELECTED ITEM INTO CLIPBOARD  Ctrl-C    
  CUT SELECTED ITEM INTO CLIPBOARD  Ctrl-X     
  PASTE FROM CLIPBOARD  Ctrl-V                 
  HIGHLIGHT TEXT  Hold Shift down while moving 
   the cursor keys.                            
                                               
 MISCELLANEOUSĴ
  UNDO LAST OPERATION  Ctrl-Z or Alt-backspace 
  TOGGLE DOS FULL SCREEN & WINDOW  Alt-enter   
 



Win Minimize windows
To remove some of the clutter of your open windows,
you can "minimize" a window, turning it into an
icon on the desktop.  The desktop is the area
outside of the Program Manager window frame.
Minimized applications are placed on the desktop at
the bottom of the screen.

   To minimize your open window, click on the 
button at the top right corner of the window.  The
minimized application remains active but out of
your way.  To turn it back into a window or
"maximize" it, double click on the desktop icon or
select it using Alt-Tab-Tab-etc.

   If your desktop is not visible, and you'd like
to see it, you can either raise up the bottom
border of the Program Manager window or minimize
Program Manager itself.

   If you forget you have a minimized application
on your desktop and you double click on the icon
back in Program Manager, you will actually launch
another copy of the application from scratch.



Win-OS/2
(WINdows-OS/2)  The Windows functionality in OS/2
Version 2.x.  OS/2 Version 2.x contains the
original Windows source code.



Win Print screen
To print your current Windows screen, you have to
copy it to the clipboard, then paste the clipboard
into a graphics or desktop publishing program and
print it from there.

   To copy the current window into the clipboard,
press Alt-PrintScreen.  To copy the entire screen
with all the windows showing into the clipboard,
press PrintScreen.  If this doesn't work, press
PrintScreen twice or press Shift-PrintScreen.

   Then, launch a paint program or desktop
publishing program, and paste the clipboard image
into a new document by selecting PASTE from the
EDIT menu.  Now you can print the document.



Win Program Manager
Program Manager is Windows' launching pad for
applications.  When you start Windows, the Program
Manager is displayed.  It appears as a screenful of
small windows that contain tiny pictures called
icons.  The icons represent applications (programs)
to be run, and if you double click on the icon, the
program is launched.

   After working with one application, you may want
to launch another and still keep the first one
active.  To get back to Program Manager, press Alt-
Tab, launch the second one and so on.

   You start and end Windows with Program Manager.
When you're ready to quit, save your data in each
application and close each one (see below).
Program Manager will then come back into view, and
you can exit Windows.  Some applications, such as
"Electronic Computer Glossary," do not have to be
closed individually.  Closing Windows will close
them automatically.


                   Group Windows
The small windows in Program Manager are group
windows, which help to visually organize your
application icons.  Some of these group windows
were set up by Windows, others by your
applications' install programs.  You can reorganize
your icons and group windows if you wish.


                  HOW TO DO BASIC
                  PROGRAM MANAGER
                    OPERATIONS


  Start Windows Application by Icon
    Double click on an icon in Program Manager.


  Start Windows Application by Name
    Select RUN from the FILE menu and type in the
    path to the program.  To learn more about DOS
    paths, see DOS path name and DOS directories.


  Exit Windows or Windows Application
    Double click on      Ŀ
    Control Menu button.    (top left corner)
                         

  Move Icon to Another Group Window
    Drag icon to another group window.


  Copy Icon to Another Group Window
    To make a copy of the icon in another group
    window, hold Control down and drag it.


  Find Out What Program the Icon Represents
    Click once on the icon, then select
    PROPERTIES from the FILE menu.


  Delete Icon
    Click once on icon, then select DELETE from
    the FILE menu.


  Delete Empty Group Window
    Click once in group window, then select
    DELETE from the FILE menu.


  Delete Group Window Full of Icons
    1. Click in group window.
    2. Minimize group window.  Click on .
    3. Click on group window icon once.
    4. Press Esc to cancel menu.
    5. Select DELETE from FILE menu.


  Install Windows Application Icon
    1. Click in group window to put the icon.
    2. Select NEW from the FILE menu.  Click OK.
    3. Make up a descriptive name and type it
       into the DESCRIPTION line.
    4. Tab to COMMAND LINE and type in the path
       of the Windows program.
    5. Select OK.



Win Run DOS programs
In Windows, you can run and keep DOS programs
active along with Windows programs.  Pressing Alt-
Tab will switch you between all active
applications, whether Windows or DOS.

   DOS programs can be run two ways.  If you have a
286, Windows runs in Standard Mode and DOS programs
take up the full screen as they normally do.  If
you have a 386, 486 or Pentium, you are most likely
running in 386 Enhanced Mode, in which case, you
can run your DOS program full screen or in a
window.  (Select HELP ABOUT in Program Manager to
find out what mode Windows is in.)

   The advantage of running a DOS program in a
window is that you can display a DOS window side by
side or overlapped with a Windows windows.  Also,
you can cut and paste text to and from a DOS
window.  You could even, for example, copy text
between two DOS programs that have no normal cut
and paste capabilities.

   If you have trouble running a DOS application in
Windows, you may have to create a PIF file, which
provides Windows with more details about the DOS
application.


                    HOW TO RUN
                   DOS PROGRAMS


  Start DOS Application by Name
    Select RUN from the FILE menu in Program
    Manager.  Type in path to program.


  Start DOS Application from an Icon
    Double click on icon in Program Manager.


  Assign an Icon to a DOS Application
    1. Switch to the Program Manager group window
       you want the icon to be displayed in.
    2. Select NEW from the FILE menu.  Click OK.
    3. Make up a descriptive name and type it
       into the DESCRIPTION line.
    4. Tab to COMMAND LINE and type in the path
       of the DOS program.
    5. Select CHANGE ICON and scroll through the
       available icons (in Windows 3.0,select VIEW
       NEXT) until you have the one you like.
    6. Click OK twice.


  End DOS Application
    End your DOS application as you normally would.


  Run DOS Program in a Window
    Press Alt-Enter to toggle between full screen
    and window modes.


  Copy Text from a DOS Window
   1. Click once on         Ŀ
      Control menu button      (top left corner)
      and select EDIT MARK. 

   2. Highlight the text with the mouse.


  Copy Text to a DOS Window
    Click once on           Ŀ
    Control menu button        (top left corner)
    and select EDIT PASTE.  





Win Run Windows programs


                    HOW TO RUN
                 WINDOWS PROGRAMS


  Start Windows Application by Icon
    Double click on an icon in Program Manager.


  Start Windows Application by Name
    From Program Manager, select RUN from the FILE
    menu and type in the path to the program name.
    To learn more about DOS path names, see DOS
    path name and DOS directories.


  End Windows Application
    Double click on      Ŀ
    Control Menu button.    (top left corner)
                         





Win Start & stop
To start your Windows session, type win at the DOS
prompt.  If you have to force Windows to run in
Standard Mode, type win /s.

   To end your Windows session, save all the data
in your active windows and close each application.
Then with Program Manager as your active window,
press Alt-F4 or double click on the Control menu
button, which is in the top left corner of the
window:  Ŀ
           
         





Win Switch windows
In Windows, it's easy to switch between active
windows.  Also remember that the Program Manager is
an active window too.


  Toggle Between ALL Windows
    Press Alt-Tab-Tab...  Hold Alt down while
    pressing Tab.  Release Alt when the title of
    the window you want is displayed.
  or
    Press Ctrl-Esc for a list of open windows
    called the Task List.  Double click on the
    title of the window you want to go to.


  Toggle Between LAST TWO Windows
    Press Alt-Tab once.


  Switch Between Groups in Program Manager
    Click inside the group window.


  Switch Between Icons
    Click on icon once.


  You Can Click on Any Visible Part of the Window
You can switch to another window by clicking on any
part of it.  If any side or corner is visible,
simply click on it to make it the current topmost
window.


       Your Window Did Not Go Away Forever!
When you switch windows, the other windows may be
temporarily out of view.  They did not disappear
for good.  Just press Alt-Tab-Tab.. and look at the
window titles as they appear one after the other.

   Alternately, press Ctrl-Esc to get a list of all
currently-open windows.



Win Typing special characters
In Windows, you can type in special characters that
are part of the font, but are not individual keys
on the keyboard by entering their ASCII numbers.
To see what characters are available, select the
Character Map utility in the Accessories group
window in Program Manager.

   All available characters in the current font
will be displayed on screen.  Go to an individual
character by clicking on it or using the Arrow
keys.  Note the keystroke numbers at the bottom
right side of the window.  For example, if Alt+0171
appears, you would enter that character by holding
down the Alt key and pressing 0, 1, 7 and 1 on the
right-hand, numeric keypad portion of your
keyboard.  To change fonts, select a different font
from the Font menu at the top left.

   You can copy a series of characters from the
Character Map to the clipboard and paste them into
your document.  Press the Select button to add a
character to the Characters to Copy input box at
the top right.  Press the Copy button to copy the
characters to the clipboard.  Go into your
document, move the cursor to the appropriate
location, and press Paste from the Edit menu.



Win Undo
To undo a Windows operation, press Ctrl-Z or Alt-
Backspace to go back a step and start over.



WIN.INI
(WINdows INItialization)  A Windows configuration
file that describes the current state of the
Windows environment.  It contains hundreds of
entries and is read by Windows on startup.  It
tells Windows such things as which programs to load
or run automatically, if any, what the various
screen, keyboard and mouse settings are, what the
desktop looks like (icon spacing, wallpaper,
colors, etc.) and what fonts are used.

   Information in WIN.INI is grouped by section
headers, which are names enclosed in brackets.  For
example, the [Colors] section contains the colors
selected by the user for window borders, titles,
backgrounds and so forth.

   The information in WIN.INI is updated by Windows
when you change various defaults; however, the file
can also be edited with a text editor or a word
processor that imports ASCII files.  Sections in
WIN.INI are added by many application install
programs under their own section header and are
used to inform the application about the current
defaults.  SYSTEM.INI is another major Windows
configuration file that is read at startup.  See
SYSTEM.INI.



Win32
A programming interface (API) for the 386's 32-bit
mode fully supported in Windows NT.  Many functions
are also supported in Windows 3.1, and applications
can be written to the Win32 subset (Win32s) to gain
improved performance on a 386 or up running Windows
3.1 or higher.  Windows 3.1 translates the 32-bit
calls in a Win32s application into its native 16-
bit calls.

   The Win32c subset includes almost all Windows NT
functions except for security.  Win32s applications
are native Windows NT and Windows 95 applications.
Windows NT runs 16-bit Windows applications via a
translation layer.  Windows 95 is expected to do
the same.

     API            Supported by
    Win16    Windows NT, Windows 3.0 and up
    Win32s   Windows NT, Windows 3.1 and up
    Win32    Windows NT, Windows 95 and up





Winbench
A series of tests that analyze computer performance
from Ziff-Davis' PC Labs.  See Winmark.



Winchester disk
An early removable disk from IBM that put the heads
and platters in a sealed unit for greater speed.
Its dual 30MB modules, or 30-30 design, caught the
"Winchester rifle" nickname.  The term later
referred to any fixed hard disk.



WinDisk
A driver from Future Domain Corporation that
converts Windows 3.1 FastDisk accesses into the
SCSI CAM standard supported on its SCSI host
adapters.



window
(1) A scrollable viewing area on screen.  Windows
are generally rectangular, although round and
polygonal windows are used in specialized
applications.  A window may refer to a part of the
application, such as the scrollable index window or
the text window in the electronic versions of this
database, or it may refer to the entire application
in a window.  See GUI and Win abc's.

(2) A reserved area of memory.

(3) A time period.



window manager
Software incorporated into all popular GUIs, which
displays a window with accompanying menus, buttons
and scroll bars.  It allows the windows to be
relocated, overlapped, resized, minimized and
maximized.  See desktop manager.



windowing software
Same as windows program.



Windows
A graphics-based windows environment from Microsoft
that integrates with and interacts with DOS.  It
provides a desktop environment similar to the
Macintosh, in which applications are displayed in
re-sizable, movable windows on screen.

   In order to use all the features of Windows,
applications must be written for it.  However,
Windows also runs DOS applications and is
increasingly being used as the primary operating
environment from which all programs are launched.

   For fundamentals on how to work with Windows,
see Win abc's and various "Win" topics.  Also see
Windows Resource Kit.


            Windows 3.x Operating Modes

 REAL MODE (Windows 3.0 only)
   For computers with less than 1MB memory.
   Provides compatibility with earlier Windows
   applications (Windows 1.x, 2.x).

 STANDARD MODE  (Windows 3.0 and 3.1)
   Used when running on a 286.  Also used in
   Windows 3.0 on 386s because it runs faster.
   Provides access to extended memory and allows
   users to run full-screen DOS applications.

 386 ENHANCED MODE  (386 and up)
   Uses the 386's virtual machine and virtual
   memory capabilities and is the common mode
   for 386s under Windows 3.1.  Can multitask DOS
   applications (program continues running in the
   background), and DOS applications can be run
   within a movable window, and text can be copied
   between DOS applications.

      In 386 Enhanced Mode, Windows can manage up
   to 16MB of memory (Windows 3.0) and 256MB of
   memory (Windows 3.1).


                 Windows Evolution
Windows 1.x, introduced in 1985, Windows 286 (2.x)
and Windows/386 were the first versions of the
product.  However, it wasn't until Windows 3.0 in
1990 that Windows took off and created an industry
due to its enhanced user interface and ability to
break DOS' infamous 1MB memory barrier.  Windows
contains its own DOS extender, which allows it to
manage extended memory.

   Windows 3.1, introduced in 1992, is more stable
and faster, supports multimedia, TrueType fonts and
drag & drop commands.  Compound documents (OLE) are
added and Real Mode is eliminated.

   Windows applications are 16-bit programs that
run on all x86 CPUs.  Windows applications can also
be written that exploit the 386's native 32-bit
instructions.  These "Win32s" applications require
Windows 3.1 and will also run under Windows 95 and
Windows NT (see Win32).


                    Windows 95
Windows 95, code named Chicago, is a major upgrade
of Windows, expected by mid 1995.  It is a 32-bit
self-contained operating system that requires a 386
minimum.  It has a different interface than 3.1 and
a variety of new features.  See Windows 95.


               WIN.INI & SYSTEM.INI
WIN.INI and SYSTEM.INI are text files used to
configure Windows.  WIN.INI contains environment
information (desktop, fonts, sounds, etc.) as well
as individual applications.  SYSTEM.INI contains
hardware information.

   Install programs and Windows' own SETUP.EXE
program modify these files, but they can be edited
manually in Notepad or any text editor.  When an
application is installed, it often adds text to
WIN.INI, which it may modify from time to time.  If
the application is deleted by the user, the lines
of text remain, but have no purpose.

   A useful utilty, called SYSEDIT.EXE, resides in
the \WINDOWS\SYSTEM directory and opens all four
files: WIN.INI, SYSTEM.INI, AUTOEXEC.BAT and
CONFIG.SYS, for editing.


               Advantages of Windows
Windows' windowing capability is its major feature.
Keeping multiple applications open is more
productive than having to close the one you are
working on in order to use another.  In addition,
data can be copied between applications via the
Windows clipboard.

   Windows applications provide a measure of
consistency.  Users know how to select from menus
and open, close, copy, move and paste data in all
applications.  All applications use the same help
system, which provides help windows that can be
left open to read the instructions while trying out
an operation (see Windows help system).

   Windows' centralized printer and font management
is far better than DOS.  DOS applications are
invidually responsible for controlling the printer.
When a DOS application is installed, it must be
told what printer is connected.  If a user changes
printers, each DOS application must be notified of
the change.

   When Windows is notified that a new printer is
installed, that printer is made available to all
Windows applications.  The same goes for fonts.  In
DOS, fonts are often duplicated.  The fonts that
work for one application do not work in any other.
In Windows, fonts are installed in one place and
are available to all programs.

   Windows DDE (dynamic data exchange) and OLE
(object linking and embedding) allow for
information in one database to automatically update
information in another.  Windows multimedia
provides a consistent way to manage audio and
video.  In general, Windows provides much more
integration and standardization than DOS.

   Microsoft's Windows Open System Architecture
(WOSA) provides standards between client
applications and server software so that any WOSA-
supported client program can access any WOSA-
supported server program.  This system-level
interoperability is vitally needed in any
environment as complex as the distributed,
heterogeneous networks commonly implemented in
today's organizations.  See WOSA.

   Microsoft had designed its future around
Windows, and there is little doubt that Windows
will be around for a long time.


             Disadvantages of Windows
Windows is a complicated operating environment that
has its roots in DOS, which was developed for the
first PCs.  Fine tuning Windows on a fully-loaded
PC that is running a mix of DOS and Windows
applications can be a daunting task, requiring
knowledge of the CONFIG.SYS, AUTOEXEC.BAT, WIN.INI
and SYSTEM.INI configuration files.

   Windows applications can be just as intimidating
as DOS applications.  Windows' graphics-based
environment allows for enormous creativity in the
design of the user interface.  Too often however,
the myriads of fancy buttons with cryptic symbols
are more difficult to understand than simple menus
with straightforward titles.

   In addition, Windows doesn't enforce the use of
common symbols for common tasks.  One application
uses the Character menu to change fonts, while
another uses the Paragraph menu.  Windows
popularity is extremely high, which tends to
overshadow the fact that a Windows interface
guarantees only a certain amount of consistency,
not a well-designed application.



Windows 1.0
The original version of Microsoft Windows
introduced in late 1985, which provided a graphical
interface and windowing environment under DOS.  It
displayed tiled windows (side by side) and was not
popular.  See Windows.



Windows 2.0
A major upgrade to Windows introduced in 1988.  It
supported overlapping and tiled windows and was
later renamed Windows/286.  Control of Windows was
very DOS oriented with programs being launched from
an "MS-DOS Executive" window that displayed
directory lists not all that different than the DOS
Dir command.  All display elements (windows, scroll
bars, etc.) were two dimensional.

   Windows 2.0 ran DOS applications full screen or
in a window and supported expanded memory for
internal use.  Although popular in several circles
and adopted by some large organizations, it was not
widely used.  See Windows 3.0 and Windows.



Windows 3.0
A complete overhaul of Microsoft Windows introduced
in 1990.  It was widely supported because of its
improved interface and ability to manage large
amounts of memory.  Windows 3.0 runs 16-bit Windows
and DOS applications on 286s and above.  Windows
3.0 substituted the MS-DOS Executive with Program
Manager and File Manager.  Display elements
(windows, scroll bars, etc.) were changed to a
three-dimensional appearance.  See Windows.



Windows 3.1
The first upgrade of Windows 3.0, introduced in
1992, which provided a more stable environment for
running 16-bit Windows and DOS applications than
did Windows 3.0.  It supports multimedia, TrueType
fonts, compound documents (OLE) and drag & drop
capabilities.  Windows 3.1 also runs 32-bit Win32s
applications by translating them into 16-bit calls.
See Windows, Windows 95 and Win32.



Windows 3.11
An upgrade to Windows 3.1.  It is expected to be
the final release of Windows 3.1 due to the
introduction of Windows 95.



Windows/386
An early version of Windows for the 386.  Using the
Virtual 8086 Mode, it was the forerunner of the 386
Enhanced Mode in Windows 3.x.



Windows 4.0
See Windows 95.



Windows 4GL
A client/server development tool for Windows and X
terminals from Computer Associates.  It was
originally developed by Ingres Corporation, which
was acquired by the Ask Group, and later CA.  CA
has enhanced and renamed the product CA-OpenRoad.
See CA-OpenRoad.



Windows 95
A major upgrade of Windows 3.1 designed to replace
Windows 3.11, Windows for Workgroups 3.11 and MS-
DOS.  Expected by mid 1995, it is an object-
oriented 32-bit operating system that requires a
386 minimum and will not run in a 286.  It is a
self-contained operating system that does not rely
on a separate pre-installed version of DOS.  It
includes various parts of DOS, which are built in.

   Windows 95 runs Windows 95, Windows 3.x and DOS
applications.  The user interface provides
foldering capabilities similar to the Macintosh.
Also like the Mac, the focus is more on the
document rather than the application that created
it.  The Windows 3.x Program Manager and File
Manager have been eliminated.

   Windows 95 includes Plug and Play capabilities
and built-in networking allowing it to fit into a
NetWare, UNIX or VINES network.  The Windows
resource memory limitation is expected to be
improved.

   Additional features are the ability to use file
names longer than eight characters and to make
icons and buttons larger.  The latter is a welcome
addition for users that run large monitors at high
resolutions, causing application windows and their
controls to appear much smaller on screen.

   Windows 95 was code named "Chicago" and was
originally thought to be named Windows 4.0.  In
September 1995, Microsoft announced the Windows 95
name.



Windows accelerator
A graphics accelerator with a driver for Windows.
See graphics accelerator.



windows environment
Any operating system, operating system extension or
application program that provides multiple windows
on screen.  DESQview, Windows, PM, MultiFinder and
X Window are examples.



Windows for Workgroups
Also known as WFW, it is a version of Windows 3.1
that includes built-in peer-to-peer networking and
electronic mail.  Its networking takes as little as
4KB of RAM when used as a client, and no more than
15KB when used as a client and server.  WFW also
includes 32-bit file access, which bypasses DOS and
replaces SmartDrive with another disk cache for
increased performance.  This is not the same as
Windows' 32-bit disk access, which drives the disk
controller directly (see FastDisk).



Windows help system
Windows provides a help system that almost all
software developers use to provide online help to
users.  The help screens appear in windows so that
instructions can be displayed side by side with the
application itself.  You can keep the help on
screen as long as you need it.  The help index is
displayed by pressing F1 in all applications.

   Help screens can be developed by technically-
oriented users as well as programmers.  The text is
written in a word processor, such as Word for
Windows, which can import and export RTF files.
Common word processing formatting, such as
underlined text, hidden text and footnotes, is used
to create links from one item to another.  The RFT
file is compiled into final form by the Windows
help compiler, which is part of the Windows SDK.



Windows memory limitation
No matter how much memory you have in your PC, you
never seem to have enough with Windows 3.x.  The
more you get used to Windows, the more you want to
keep all the applications open that you use during
the day.  Unfortunately, each one takes up a
certain amount of memory.

   If you get an "Out of Memory" message often,
there are several things you can do as a routine.

   Keep windows minimized rather than full screen.

   Keep the clipboard empty.

   Turn off the desktop wallpaper in Control Panel.
Wallpaper uses memory.

   Check your permanent swap file.  The larger the
swap file, the more applications can be "rolled
out" to disk temporarily.

   If all else fails, closing one or more
applications should give you enough room to open up
another application.


                 System Resources
No matter how much real or virtual (swap file)
memory you have, Windows 3.x uses only two 64K
regions of memory to keep track of its active
applications.  When an application is active in a
window, each of the application's components
(windows, dialog boxes, icons, buttons, etc.) uses
up several bytes of this "System Resources" memory.

   You may have a lot of real memory left, but
Windows will tell you that there is "Not enough
memory..." when either of the regions get close to
full.  There's nothing you can do but unload one or
more applications.

   In addition, when these System Resources memory
regions are filled more than half way, strange
things can occur.  Select About from your Program
Manager's Help menu, and look at System Resources.
When this number gets below 30%, watch out,
anything can happen.

   This problem should be cleared up in Windows 95
as more memory is expected to be alloted to these
resources.



Windows Metafile
A Windows file format that holds vector graphics,
bitmaps and text.  It uses the .WMF file extension.
The Windows Metafile is Windows' preferred vector
format, since it contains actual Windows commands
(GDI calls) to draw the images.  It is also used by
programs to hold data between sessions, and,
Windows sometimes uses it for temporary storage.

   The Aldus Placeable Metafile is a PageMaker
variation that contains a header indicating into
what size rectangle the object will be rendered.



Windows NT
(Windows New Technology)  An advanced 32-bit
operating system from Microsoft for 386s and up,
MIPS, Alpha and PowerPC CPUs.  Introduced in 1993,
NT does not use DOS, it is a self-contained
operating system.  NT runs NT-specific applications
as well as DOS and Windows applications.

   Features include peer-to-peer networking,
preemptive multitasking, multithreading,
multiprocessing, fault tolerance and support for
the Unicode character set.  NT provides extensive
security features and continually tests the
validity of application requests even after the
application has been opened.

   Windows NT supports 2GB of virtual memory for
applications and 2GB for its own use.  Windows NT
and Windows NT Workstation are the first and second
releases of the client version.  Windows NT
Advanced Server (NTAS) and Windows NT Server (NTS)
are first and second releases of the server
version, which supports symmetric multiprocessing
and provides transaction processing for hundreds of
online users.  NT supports a dual boot feature.

   In its first year on the market, the client
version of NT has not caught on, but the server
versions are increasingly being used.  It is
expected that Windows NT will become a predominant
server operating system in the future.



Windows out of memory
See Windows memory limitation.



windows program
(1) Software that adds a windows capability to an
existing operating system.

(2) An application program written to run under
Windows.



Windows requirements
Windows places far more demands of a PC than does
DOS.  Don't forget to include a graphics adapter
with a graphics accelerator.  This is just as
important as a fast CPU.  Following are the minimum
and recommended requirements.

                Minimum     Recommended

     CPU        486/25      486/66, DX4 or Pentium
     Bus        ISA         ISA plus local bus
     RAM (MB)   4           8+
     Hard disk  200MB       500MB+
     VGA        Windows accelerator





Windows Resource Kit
Windows technical documentation from Microsoft
written for support personnel.  It is a
comprehensive document with over 500 pages of
technical details that includes flow charts and a
chapter on troubleshooting.  The text has been
licensed by WUGNET, the Windows Users Group
Network, and compiled into a Windows help system
with hypertext links.  See WUGNET.



Windows Resources
See Windows memory limitation.



Windows SDK
A set of development utilities for writing Windows
applications in Microsoft C.  It provides tools for
creating custom cursors, fonts and icons, bitmaps,
menus and online help.



Windows shell
An add-on user interface for Windows.  There are
many Windows shells available that streamline the
Windows interface by providing such features as
foldering, customized toolbars and quick access to
the DOS command line.  Windows shells can replace
Program Manager and File Manager or coexist with
them side by side.  They often come with a variety
of utility programs.

   Popular shells are Norton Desktop for Windows,
PC Tools for Windows and HP's Dashboard.



Windows SNA APIs
Programming interfaces that allow Windows
applications to communicate with SNA protocols and
functions, such as HLLAPI and APPC.



Windows swap file
A disk file used to store applications temporarily
when there isn't enough memory to hold all active
applications.  On setup, Windows creates a
permanent swap file for running in 386 Enhanced
Mode (SPART.PAR file and 386SPART.PAR hidden file).
If these files are not present, or if Windows is in
Standard Mode, Windows creates temporary swap files
as needed.

   To free up disk space, you can delete or reduce
the size of the permanent swap file.  In Windows
3.0, load Windows in Real Mode (win /r) and run the
SWAPFILE program.  In Windows 3.1, select Control
Panel/386 Enhanced/Virtual Memory/Change.



Windows Telephony
See TAPI.



WINDOWS WORLD
A computer exposition sponsored by The Interface
Group.  Its first show was in 1991.  WINDOWS WORLD
is often scheduled with COMDEX.  See COMDEX.


                   1995 Schedule

  WINDOWS WORLD/Spring COMDEX - Atlanta, Apr. 24-27
  WINDOWS WORLD/COMDEX Canada - Toronto, Jul. 12-14
  WINDOWS WORLD               - Chicago, Jul. 26-28
  WINDOWS WORLD/Networks Expo - Dallas, Sep. 12-14





WinG
(WINdows Games)  A programming interface (API) that
lets Windows application developers access the
video frame buffer directly.  It allows game
programs to be written to run as fast in Windows as
they do under DOS.  Application programmers use
WinG, while programmers writing drivers for the
adapter vendors write to the DCI interface.



WINGZ
A presentation-oriented Macintosh spreadsheet from
Informix Software., Menlo Park, CA.  Text, graphs
and charts, scanned images, freehand illustration
and spreadsheet data can be combined.  When data is
updated, related graphics and numerical references
within the text are changed.



WinJet
A high-speed PostScript emulation system for
Windows and LaserJet printers from LaserMaster
Corporation, Eden Prarie, MN.  It generates
PostScript output, including Type 1 and TrueType
fonts, and sends it directly to the LaserJet video
input.  It also includes a refined print manager
that queues print jobs.

   Unlike PostScript printers where the page
rasterization is done in the printer, this process
is done by the CPU using WinJet software.  Printing
speed is improved when the computer system is
upgraded.  WinJet 300 and 800 provide 300 and 800
dpi for LaserJet II/III models.  WinJet 1200
provides 1200 dpi for LaserJet 4 models.



Winmark
A unit of performance based on Ziff-Davis' PC Labs
Winbench tests.  Graphics Winmarks rate Windows
video performance as a weighted average of 12
benchmarks.  Common VGA adapters are rated around
two million Winmarks.  Fast graphics accelerators
using local buses can achieve 50 million Winmarks
and more.

   Winbench Version 3.1 provides more accurate
Winmark tests and avoids slanted results from
"benchmark-aware" drivers used in some graphics
accelerator boards.  It is necessary to know which
Winmark version is being used for the test.
Version 4.0 reports fewer Winmarks for the same
performance than Version 3.1.

   Disk Winmarks rate the speed of disks and disk
caching.  See DOSmark.



Winsock API
(WINdows SOCKets API)  A Windows programming
interface for TCP/IP software.  Since most TCP/IP
software for Windows supports the Winsock API,
writing a client/server application to this
specification allows it to be used on different
TCP/IP stacks across the network.



WinWord
See Microsoft Word.



wire wrap
An early method of wiring circuit boards.  A tool
strips the end of the wire and coils it.  The coil
is pressed onto a metal prong on the board.



wireframe modeling
In CAD, a technique for representing 3-D objects,
in which all surfaces are visibly outlined in
lines, including the opposite sides and all
internal components that are normally hidden from
view.  Compared to surface and solid modeling,
wireframe modeling is the least complex method for
representing 3-D images.



wireless
Radio transmission via the airwaves.  Various
communications techniques are used to provide
wireless transmission including infrared line of
sight, cellular, microwave, satellite. packet radio
and spread spectrum.  See Ardis, Mobitex, FDMA,
TDMA, CDMA and CDPD.



wiring closet
The central distribution or servicing point for
cables in a network.



wizard
Instructional help that guides the user through a
series of steps to accomplish a task.



wizzy wig
See WYSIWYG.



WK1
Lotus 1-2-3 Version 2.0 file extension.



WKS
Lotus 1-2-3, Version 1A file extension.



WMF
See Windows Metafile.



word
(1) The computer's internal storage unit.  Refers
to the amount of data it can hold in its registers
and process at one time.  A word is often 16 bits,
in which case 32 bits is called a double word.
Given the same clock rate, a 32-bit computer
processes four bytes in the same time it takes a
16-bit machine to process two.

(2) The primary text element, identified by a word
separator (blank space, comma, etc.) before and
after a group of contiguous characters.

(3) See Microsoft Word.



word addressable
A computer that can address memory only on word
boundaries.  Contrast with byte addressable.



Word for Windows
See Microsoft Word.



word processing
The creation of text documents.  Except for labels
and envelopes, it has replaced the electric
typewriter in most offices, because of the ease in
which documents can be edited, searched and
reprinted.

   Advanced word processors function as elementary
desktop publishing systems.  Although there are
still machines dedicated only to word processing,
most word processing is performed on general-
purpose computers using word processing software.

    Functions of a Full-featured Word Processor

TEXT EDITING
Text can be changed by deleting it, typing over it
or by inserting additional text within it.

WORD WRAP AND CENTERING
Words that extend beyond the right margin are
wrapped around to the next line.  Text can be
centered between left and right margins.

SEARCH & REPLACE, MOVE AND COPY
Any occurrence of text can be replaced with another
block of text.  You can mark a block of text and
move it elsewhere in the document or copy it
throughout the document.

LAYOUT SETTINGS
Margins, tabs, line spacing, indents, font changes,
underlining, boldface and italics can be set and
reset anywhere within the document.

HEADERS, FOOTERS AND PAGE NUMBERING
Headers and footers are common text printed on the
top and bottom of every page.  Headers, footers and
page numbering can be set and reset anywhere within
the doucment.  Page numbering in optional Roman
numerals or alphabetic letters is common.

STYLE SHEETS
After designing a document, its format can be used
again.  Layout codes (margins, tabs, fonts, etc.)
can be stored in a style sheet file and applied to
a new document.

MAIL MERGE
Creates customized letters from a form letter and a
list of names and addresses.  The list can be
created as a document or can be imported from
popular database formats.

MATH AND SORTING
Columns of numbers can be summed and simple
arithmetic expressions can be computed.  Lines of
text can be reordered into ascending (A-Z) or
descending (Z-A) sequence.

PREVIEW, PRINT AND GROUP PRINT
A document can be previewed before it is printed to
show any layout change that may not normally show
on screen (page breaks, headers, footers, etc.).
Documents can be printed individually or as a group
with page numbers consecutively numbered from the
first to the last document.

FOOTNOTES
Footnote entries can be made at any place in the
document, and the footnotes printed at the end of a
page or document.

SPELLING CHECKER AND THESAURUS
Spelling for an individual word, marked block of
text or an entire document can be checked.  When
words are in doubt, possible corrections are
suggested.  Advanced systems can correct the
misspellings automatically the next time.  A
thesaurus displays synonyms for the word at the
current cursor location.

FILE MANAGEMENT
Documents can be copied, renamed and deleted, and
directories, or folders, can be created and deleted
from within the program.  Advanced systems set up a
purge list of names or glimpses of document
contents in order to allow a user to easily rid the
disk of unwanted files.


                Advanced Functions

WINDOWS
Allows two or more documents to be worked on at the
same time.  Text can be moved or copied from one
document to the other.

COLUMNS
Columns can be created in all word processors by
tabbing to a tab stop.  However, true column
capability wraps words to the next line within each
column.  Columns are required for writing resumes
with employer information on the left and work
history on the right.  Script writing also requires
column capability.  Magazine-style columns flow
words from the bottom of one column to the top of
the next.

TABLES OF CONTENTS AND INDEXES
Tables of contents and indexes can be generated
from entries typed throughout the document.

DESKTOP PUBLISHING
Graphics can be merged into the text and either
displayed on screen with the text or in a preview
mode before printing.  A graphic object can be
resized (scaled), rotated and anchored so that it
remains with a particular segment of text.  Rules
and borders can also be created within the text.


           Graphics-based Vs Text-based
Graphics-based programs (Windows, Macintosh, etc.)
show a close facsimile on screen of the typefaces
that will be printed.  Text-based programs always
show the same type size on screen.

   Graphics-based systems are far superior for
preparing newsletters and brochures that contain a
variety of font sizes.  Text-based screens are fine
for office typing or for documents with a simple
format.  They are also very responsive and good for
creative writing.


                 Format Standards
Every major word processing program generates its
own proprietary codes for layout settings.  For
example, in WordStar, ^PB turns on and off
boldface.  In WordPerfect 5.x, [BOLD] turns
boldface on, and [bold] turns it off.

   Conversion programs are used to translate
documents from one format to another.  If a
conversion program doesn't exist for the two
required formats, multiple search & replace
commands can be performed on the original document.
However, if the same code turns a mode on as well
as off, as in the WordStar example above, the codes
have to be changed manually one at a time.


                The User Interface
Word processing programs run from the ridiculous to
the sublime.  Some of the most awkward programs
have sold well.  As a novice, it's difficult to
tell a good one from a bad one.  It takes time to
explore the nuances.  Also, what's acceptable for
the slow typist can be horrendous for the fast
typist.

   Repetitive functions such as centering and
changing display attributes (boldface, italics,
etc.) should be a snap.  Changing margins, tabs,
indents and fonts should also be easy.

   The most important components in word processing
hardware are the keyboard and screen.  The feel of
a keyboard is personal, but proper key placement is
critical.  Display screens should have the highest
resolution possible, and color screens are better
than monochrome as long as the program allows the
user to change colors.



word processing machine
A computer that is specialized for only word
processing functions.



word processor
(1) Software that provides word processing
functions on a computer.

(2) A computer specialized for word processing.
Until the late 1970s, word processors were always
dedicated machines.  Today, personal computers have
replaced almost all dedicated word processors.



word separator
A character that separates a word, such as a blank
space, comma, period, -, ? and !.



word wheel
A lookup method in which each character that is
typed in moves the on-screen index to the closest
match.  By watching the index move character by
character, you can easily tell if you have made a
typo.  In addition, you can get to the beginning of
a word group quickly and then scroll to the word or
phrase you are looking for.  The DOS and Windows
versions of this database use a word wheel.



word wrap
A word processing feature that moves words to the
next line automatically as you type based on the
current right margin setting.  Some word processing
programs allow word wrap to be turned off for
writing source code.



WordBASIC
A subset of Microsoft QuickBASIC with added word
processing functions used to customize Microsoft
Word word processors.



WordPerfect
A full-featured word processing program from
WordPerfect Corporation.  Introduced in 1980 for
the Data General mini, WordPerfect is the most
widely used word processor in the world, running on
all major personal computers and workstations.

   Version 5.0 introduced significant improvements
that included desktop publishing features and a
WYSIWYG preview mode.  Version 5.1 added menus.

   A Windows version was introduced as Version 5.1
to keep it in sync with the DOS version.  In 1993,
Version 6.0 for DOS added significant features
including new graphics modes, scalable fonts, and
built-in fax, e-mail and spreadsheet functions.  As
of January 1994, WordPerfect indicated that, except
for interim releases to keep it file compatible
with the Windows version, WordPerfect for DOS will
not be upgraded.



WordPerfect Corporation
(WordPerfect Corporation, Orem, UT)  Founded in
1979 as Satellite Software International by Alan
Ashton, Bruce Bastian and Don Owens.  Its first
product, SSI*WP, was a word processor for the Data
General minicomputer.  In 1980, W. E. Pete
Peterson, Bastian's brother-in-law, joined the
company as office manager and later became
executive vice president.

   In 1982, WordPerfect was introduced, a version
of SSI*WP for the IBM PC.  At the time, WordStar
was number one, and there were several other word
processors available for the PC.  Yet, over time,
WordPerfect outsold them all.  In 1986, SSI was
renamed WordPerfect Corporation.

   For an interesting inside story by Pete Peterson
of how the company got started and grew without
external financing into the software giant it is
today, read his book, "AlmostPerfect," published by
Prima Publishing, Rocklin, CA 95677, 916/786-0426,
ISBN 1-55958-477-7.

   In 1994, WordPerfect was acquired by Novell.



WordPerfect Office
See GroupWise.



WordStar
A full-featured PC word processing program from
SoftKey International, Inc, Cambridge, MA.
Introduced in 1978 for CP/M machines, it was the
first program to give full word processing
capabilities to personal computer users at far less
cost than the dedicated word processors of the
time.  Many WordStar keyboard commands have become
de facto standards.



workflow automation
Automatically routing data and documents over the
network to the users responsible for working with
them.  A workflow automation system keeps track of
the processes a document goes through and alerts
users when operations are overdue.



workgroup
Two or more individuals who share files and
databases.  LANs designed around workgroups provide
electronic sharing of required data.  See groupware
and workflow automation.



working directory
See current directory.



Workplace
A set of strategies and system software
technologies from IBM that will guide its desktop
products into the next century.  It is based on
Carnegie-Mellon's Mach operating system that is
scalable from PDA to mainframe and designed to host
multiple user interfaces or "personalities."

   It incorporates user interfaces based on the
OS/2 Workplace Shell combined with multimedia,
handwriting and voice recognition.  It includes
object-oriented technologies based on SOM and
OpenDoc.  Workplace also supports open interfaces
for distributed computing such as OSF's DCE and
DME.



Workplace Shell
The primary component of the OS/2 2.x user
interface, which provides the equivalent
functionality of Program Manager and File Manager
in Windows.  The Workplace Shell is extensible and
application developers may use Workplace Shell
library functions when developing programs.



worksheet
Same as spreadsheet.



worksheet compiler
Same as spreadsheet compiler.



workstation
(1) A high-performance, single-user microcomputer
or minicomputer that is used for graphics, CAD,
CAE, simulation and scientific applications.  It is
typically a RISC-based computer that runs under
some variation of UNIX.

(2) A personal computer in a network.  In this
context, a workstation is the same as a client.
Contrast with server and host.

(3) In the telecom industry, a combined telephone
and computer.

(4) Any terminal or personal computer.



Worldwide Web
An Internet service that links documents by
providing hypertext links from server to server.
It allows a user to jump from document to related
document no matter where it is stored on the
Internet.  Worldwide Web client programs, such as
Mosaic and Cello, allow users to browse "the Web."

   The Web differs from the Gopher system on the
Internet.  The Web links everything via hypertext,
whereas Gopher provides hierarchical menus of items
and services.



worm
(1) A destructive program that replicates itself
throughout disk and memory, using up the computers
resources and eventually putting the system down.
See virus and logic bomb.

(2) A program that moves through a network and
deposits information at each node for diagnostic
purposes or causes idle computers to share some of
the processing workload.

(3) (WORM) (Write Once Read Many)  An optical disk
that can be recorded only once.  Updating requires
destroying the existing data (all 0s made 1s), and
writing new data to an unused part of the disk.



WOSA
(Windows Open System Architecture)  Umbrella term
from Microsoft for a variety of programming
interfaces that are designed to provide application
interoperability across the Windows environment.
It provides standards between Windows clients and
servers, allowing Windows applications to access
services on the network from any software provider
(database manager, document manager, network
services, etc.) that supports the WOSA interface.

   If WOSA-supported software is widely developed,
WOSA will become an important strategy for
Microsoft, as it provides a common denominator for
front-end Windows applications to access back-end
services from different vendors.  For example, any
WOSA-supported query program from one vendor can
gain access to any WOSA-supported DBMS from any
another vendor.  A WOSA-supported word processing
program can store its documents in a WOSA-supported
document management system.  One e-mail program can
send messages to a different e-mail program and so
on.  See SPI.

   Following are WOSA interfaces currently planned
or implemented.

  Interface            Provides access to

    ODBC             Databases (DBMSs)
    MAPI             Messaging (supports X.400 CMC)
    TAPI             Telephone network services
    LASPI            Software licensing
    Windows SNA      IBM SNA networks
    Windows Sockets  Sockets-based applications on
                       UNIX platforms
    Microsoft RPC    Run remote procedures
                       (DCE-compatible)
    Financial
      Services       Banking services (card
                       readers, PIN pads, etc.)
    WOSA/XRT         Live market data (stocks,
                       news, etc.)





WP
See word processing and WordPerfect.



WPcom
See write precompensation.



WPS
See Workplace Shell.



Wrist Pro
A wrist support from Wrist Pro, St. Louis, MO, that
provides a multi-level platform that keeps the
wrist in a neutral wrist position.



wrist rest
A platform used to raise the wrist to keyboard
level for typing.



wrist support
A product that prevents and provides a therapy for
carpal tunnel syndrome by keeping the hands in a
neutral wrist position.



write
To store data in memory or record data onto a
storage medium, such as disk and tape.  Read and
write is analogous to play and record on an audio
tape recorder.



write access
Authorization to record or update data stored in
the computer.



write back cache
A disk or memory cache that handles writing.  Data
written into the high-speed cache memory from the
CPU is written onto disk or into real memory during
idle machine cycles.



write cycle
The operation of writing data into a memory or
storage device.



write error
The inability to store into memory or record onto
disk or tape.  Malfunctioning memory cells or
damaged portions of the disk or tape's surface will
cause those areas to be unusable.



write only code
Jokingly refers to source code that is difficult to
understand.



write precompensation
Using a stronger magnetic field to write data in
sectors that are closer to the center of the disk.
In CAV recording, in which the disk spins at a
constant speed, the sectors closest to the spindle
are packed tighter than the outer sectors.

   One of the hard disk parameters stored in a PC's
CMOS RAM is the WPcom number, which is the track
where precompensation begins.



write protect
A mode that restricts erasing or editing a disk
file.  See file protection.



Write protect error
A DOS error message that means the floppy disk has
been protected and data cannot be recorded on it.
Either unprotect it or use another disk.  See file
protection.



write protect notch
A small, square cutout on the side of a floppy disk
used to prevent it from being written and erased.
On 5.25" floppies, the notch must be covered for
protection.  To protect a 3.5" diskette, press the
slide lever toward the edge of the disk uncovering
a hole (upper left side viewed from the back).

   You "cover" the notch on 5.25" disks; you
"uncover" the hole on 3.5" disks.  The two common
formats use exact opposite methods.



WSI
See wafer scale integration.



WUGNET
(Windows Users Group NETwork)  An organization of
Windows users and developers founded in 1988.  It
provides technical information, software resources
and tools, CompuServe forums and newsletters.
Address: 126 E. State St., Media, PA 19063,
215/565-1861.



WWW
See Worldwide Web.



WXmodem
(Window Xmodem)  A faster version of the Xmodem
protocol that allows the sending system to transmit
data without waiting for the receiving system to
acknowledge the transfer.



WYSIWYG
(What You See Is What You Get)  Pronounced "wizzy-
wig."  Refers to text and graphics appearing on
screen the same as they print.  To have WYSIWYG
text, a screen font must be installed that matches
each printer font.  Otherwise, a 24-point font may
display in correct size relationship to a 10-point
font, but it won't look like the printed typeface.

   It is almost impossible to get 100% identical
representation, because screen and printer
resolutions rarely match.  Even a 300 dpi printer
has a higher resolution than almost every monitor.



WYSIWYG MOL
(WYSIWYG More Or Less)  Quite often what you get,
when what you want is WYSIWYG!



x
(1) In programming, symbol used to identify a
hexadecimal number.  For example, 0x0A and \x0A
specify the hex number 0A.

(2) See X Window.



x-axis
See x-y matrix.



X-based
See X Window and Xbase.



x-height
In typography, the height of the letter x in lower
case.  Point size includes the x-height, the height
of the ascender and the height of the descender.
See typeface.



X Image Extension
See XIE.



X library
See Xlib.



X/Open
A consortium of international computer vendors
founded in 1984 to resolve standards issues.
Incorporated in 1987 and based in London, North
American offices are in San Francisco.  Its purpose
is to integrate evolving de facto and international
standards in order to achieve an open environment,
or CAE (Common Application Environent).  XPG
defines X/Open's specification, and VSX defines its
testing and verification procedure.

   In late 1993, Spec 1170 was announced, a
specification that contains over 1,100 APIs.  Spec
1170 is designed to provide a unified programming
interface for the UNIX operating system.  For
information, call 415/323-7992; in the U.K. 44-734-
508311.



X/Open Portability Guide
Known as the XPG, it is a set of standards that
specify compliance with X/Open's Common Application
Environment (CAE).  XPG3 (Release 3), introduced in
1989, specifies standards for UNIX System V Release
4.0.



X protocol
The message format of the X Window System.



X server
The receiving computer in an X Window system.  The
X server displays the application that is running
on a remote machine, which is the X client.  See X
Window.



X standard
See X Window and X.400.



X terminal
A terminal with built-in X server capability.



X toolkit
Development software for building X Window
applications.  Typically includes a widget set, X
Toolkit Intrinsics (Xt) libraries for managing the
widget set and the X Library (Xlib).



X Window
Formally "X Window System," also called "X Windows"
and "X," it is a windowing system developed at MIT,
which runs under UNIX and all major operating
systems.  X lets users run applications on other
computers in the network and view the output on
their own screen.

   X generates a rudimentary window that can be
enhanced with GUIs, such as Open Look and Motif,
but does not require applications to conform to a
GUI standard.  The window manager component of the
GUI allows multiple resizable, relocatable X
windows to be viewed on screen at the same time.

   X client software resides in the computer that
performs the processing and X server software
resides in the computer that displays it.  Both
components can also be in the same machine.  This
seems opposite to today's client/server
terminology, but the concept is that the server is
"serving up" the image.  See XIE.



x-y matrix
A group of rows and columns.  The x-axis is the
horizontal row, and the y-axis is the vertical
column.  An x-y matrix is the reference framework
for two-dimensional structures, such as
mathematical tables, display screens, digitizer
tablets, dot matrix printers and 2-D graphics
images.



x-y monitor
In graphics, the display screen of a vector display
terminal.  The entire vector display comprises the
monitor and vector graphics controller.



x-y plotter
Same as plotter.



x-y-z matrix
A three-dimensional structure.  The x and y axes
represent the first two dimensions; the z axis, the
third dimension.  In a graphic image, the x and y
denote width and height; the z denotes depth.



X.12
See X12.



X.21
An ITU-TSS standard protocol for a circuit
switching network.



X.25
An ITU-TSS standard (1976) for the protocols and
message formats that define the interface between a
terminal and a packet switching network.  See
packet switching.



X.28
An ITU-TSS standard (1977) for exchange of
information between a DTE and a PAD; commonly known
as PAD commands.



X.29
An ITU-TSS standard (1977) for exchange of
information between a local PAD and a remote PAD;
procedures for interworking between PADs.



X.3
An ITU-TSS standard (1977) for a PAD (packet
assembler/disassembler), which divides a data
message into packets for transmission over a
packet-switched network and reassembles them at the
receiving side.



X.32
An ITU-TSS standard (1984) for connecting to an
X.25 network by dial up.  It defines how the
network identifies the terminal for billing and
security purposes and how default parameters are
negotiated for the connection.



X.400
An OSI and ITU-TSS standard messaging protocol.  It
is an application layer protocol (layer 7 in the
OSI model).  X.400 has been defined to run over
various network transports including Ethernet,
X.25, TCP/IP and dial-up lines.  See messaging
protocol and CMC.

   The format of an X.400 address is:

     c=  /admd=  /prmd=  /o=  /s=  /g=

     c   country
  admd   administrative management domain
           (public e-mail service)
  prmd   private management domain
           (inhouse e-mail)
     o   organization
     s   surname
     g   given name

See X.400 API Association and messaging protocol.





X.400 API Association
Known as the XAPIA, it is a consortium dedicated to
standardizing X.400 and other specifications, such
as the CMC messaging API.  For information, contact
Leslie Schroeder Press Relations, 10151 Western
Drive, Cupertino, CA 95014, 408/446-9158.



X.500
An OSI protocol for managing online directories of
users and resources.  X.500 can be used to support
X.400 and other messaging systems, but it is not
restricted to e-mail usage.  It provides a
hierarchical structure that fits the world's
classification system: countries, states, cities,
streets, houses, families, etc.  The goal is to
have a directory that can be used globally.

   An X.500 directory is called a Directory
Information Base (DIB) or white pages.  The program
that maintains the DIBs is called a Directory
Server Agent (DSA).  A Directory Client Agent (DCA)
is used to search DSA sites for names and
addresses.

   The X.500 specification was published in 1988,
and the 1993 edition is interoperable with it.  The
1993 edition includes replication and access
control.  Using the Directory Information Shadowing
Protocol (DISP), replication allows a portion of
the Directory Information Tree (DIT) to be copied
between nodes.

   Access control provides a method to allow or
deny access to a particular attribute of a
directory entry based on the identity of the
requesting user.



X.75
An ITU-TSS standard for connecting X.25 networks.



X.PC
A communications protocol developed by McDonnell
Douglas for connecting a PC to its Tymnet packet-
switched public data network.



X11
The current version of the X Window System.  X11R5
(Version 11, Release 5, Sept. 1991) provides a
stable and feature-rich environment.



X12
An ANSI standard protocol for EDI.  See Tradacoms
and EDIFACT.



x86
Refers to the Intel 8086 CPU family (8086, 8088,
80186, 80286, 386, 486, Pentium).  Starting with
the 386, Intel has dropped the "80" prefix in its
reference manuals.  Same as 80x86.


              x86 CPU SPECIFICATIONS

               Bus size (bits)       Typical
CPU#    Clock            Max Floppy Hard Disk
(Word   Speed            RAM  Disk   (MB)
 Size)  (MHz)   MIPS    (------Bytes------)  OS

 8088    5    .33    8 1M5.25"  10-20 DOS
 (16)                      360K      
                         3.5"        DR DOS
                           720K      
 8086   5-10 .33-.6616 1M  1.44M10-40
 (16)                                
                         Ĵ     
 286    6-12 1.2-2.41616M5.25"  20-80 DOS
 (16)                      360K      DR DOS
                           1.3M       OS/2
                                     Ver 1.x
                         3.5"        
 386DX 16-40 6-15   32 4G  720K 80-  
 (32)                      1.44M  200 DOS
                           2.88M     
 386SX 16-33 2.5-5  1616M       60-  DR DOS
 (32)                             100
                                      OS/2
 386SL 20-25 3.2-4  1632M       60-  Ver 1.x
 (32)                             100Ver 2.x
                                     
 486DX 25-10020-80  32 4G       100-  UNIX
 (32)                            2000
                                     Windows
 486SX 20-25 16.5-2032 4G       80-    NT
 (32)                             500
                                     
Pentium60-100100-16864 4G       400- 
 (32)                            5000





x86 clone
A CPU chip that is compatible with various models
of the Intel x86 family.  Companies such as AMD,
Cyrix and NexGen make x86 clones.



XA
See CD-ROM XA and 370/XA.



XAPIA
See X.400 API Association.



Xbase
Refers to dBASE-like languages such as Clipper and
FoxPro.  Originally almost identical to dBASE, new
commands and features over the years have made
Xbase languages only partially dBASE compatible.



XCMD
(eXternal CoMmanD)  A user-developed HyperCard
command written in a language such as C or Pascal.
See XFCN.



Xcopy
A DOS and OS/2 utility that copies files and
subdirectories.  See DOS Xcopy.



XDB Enterprise Server
A relational database management system (DBMS) for
DOS, Windows, Windows NT and OS/2 from XDB Systems,
Inc., Laurel, MD.  XDB is fully compatible with
IBM's DB2 database.



XDOS
Software from Hunter Systems, Inc., Mountain View,
CA, that converts Intel x86 executable code into
Motorola 68020 code ready to run under UNIX.  A PC
program can be translated into a running program on
a UNIX-based 68020 computer.



XDR
(EXternal Data Representation)  A data format
developed by Sun that is part of its networking
standards.  It deals with integer size, byte
ordering, data representation, etc. and is used as
an interchange format.  Different systems convert
to XDR for sending and from XDR upon receipt.



xe file
See EXE file.



XENIX
See SCO XENIX.



xerography
See electrophotographic.



Xerox Network Services
See XNS.



XFCN
(eXternal FunCtioN)  A user-developed HyperCard
function that is written in a language, such as C
or Pascal.  XFCNs usually return a value.  See
XCMD.



xfr
Often used as an abbreviation for "transfer" in may
electronic and communications terms and phrases.



XGA
(EXtended Graphics Array)  An IBM video display
standard (1990) optimized for graphical user
interfaces.  It adds 132 column text to VGA, plus
additional resolutions up to 1024x768 with 256
colors interlaced.  XGA-2 (1992) provides non-
interlaced 1024x768x64K.



XGML
A family of text manipulation software for PCs,
Macs, IBM mainframes, UNIX and others from Software
Exoterica Corporation, Ottawa, Ontario.  With
strong support for SGML, it includes XTRAN, a
language that translates, matches and links text.



XIE
(X Image Extension)  Extensions to the X Window
system that enhance its graphics capability.  It
allows the desktop terminal or PC (the server) to
retrieve various types of compressed images from
the client and be able to manipulate them.

   Remember, in X, the client and server are the
opposite of what they are in client/server.  See X
Window.



XIP
(Execute In Place)  The ability to execute a
program directly from a memory card.



XL
See Excel.



Xlib
(X LIBrary)  Functions in the X Window System.  See
X toolkit.



XLISP
A microcomputer version of the LISP programming
language that has been in the public domain for a
number of years.



XMI
A high-speed bus from Digital used in large VAX
machines.



Xmodem
The first widely-used file transfer protocol for
personal computers, developed by Ward Christensen
for CP/M machines.  Early versions used a checksum
to detect errors.  Later versions use the more
effective CRC method (Xmodem-CRC).  Programs
typically include both methods and drop back to
checksum if CRC is not present at the other end.

   Xmodem transmits 128-byte blocks.  Xmodem-1K
improves speed by transmitting 1,024-byte blocks.
Xmodem-1K-G transmits without acknowledgment (for
error-free channels or when modems are self
correcting), but transmission is cancelled upon any
error.



XMP
(X/Open Management Protocol)  A high-level network
management protocol governed by X/Open.  Network
management software written to the XMP interface is
shielded from the details of the underlying SNMP or
CMIP protocols.



XMS
(eXtended Memory Specification)  A programming
interface that allows DOS programs to use extended
memory in 286s and up.  It provides a set of
functions for reserving, releasing and transferring
data to and from extended memory without conflict,
including the high memory area (HMA).  See
HIMEM.SYS and DOS extender.

               XMS Versus VCPI/DPMI
XMS, VCPI and DPMI all deal with extended memory.
However, XMS allows data and programs to be stored
in and retrieved from extended memory, whereas the
VCPI and DPMI interfaces allow programs to "run" in
extended memory.





XMT
In communications, an abbreviation for transmit.



XNS
(Xerox Network Services)  An early networking
protocol suite developed at Xerox's Palo Alto
Research Center (PARC).  XNS has been the basis for
many popular network architectures including
Novell's NetWare, Banyan's VINES and 3Com's 3+.


                        XNS      OSI       NetWare
  XNS Layers         Protocols  Layers    Protocols

  4 - Application                 7
  3 - Control                    5,6
  2 - Transport      SPP, PEP     4         SPX
  1 - Internet       IDP          3         IPX
  0 - Transmission   Ethernet    1,2





xon-xoff
In communications, a simple asynchronous protocol
that keeps the receiving device in synchronization
with the sender.  When the buffer in the receiving
device is full, it sends an x-off signal (transmit
off) to the sending device, telling it to stop
transmitting.  When the receiving device is ready
to accept more, it sends the sending device an x-on
signal (transmit on) to start again.



Xopen
See X/Open.



XPG
See X/Open Portability Guide.



XT
(1) (EXtended Technology)  The first IBM PC with a
hard disk, introduced in 1983.  See PC.

(2) (Xt)  See X toolkit.



XT bus
See PC bus.



XT class
Refers to first-generation PCs, which includes the
first floppy-disk PC, the actual "XT" PC with a
hard disk and all compatibles that use the 8088 or
8086 or compatible CPU and an 8-bit bus.



XT interface
See XT bus.



XTP
(Xpress Transfer Protocol)  A research transport
protocol designed by Greg Chesson of Silicon
Graphics.  It is a type of lightweight protocol
designed for high-speed networks and provides
services at layers 3 and 4 of the OSI model.

   XTP is flexible and can select rate and flow
control.  In order to handle different traffic; for
example, transactions versus realtime video, XTP's
"universal receiver" has the transmitting station
tell the receiver when to acknowledge.  ANSI's
version is called HSTP (High Speed Transport
Protocol).



XTRAN
See XGML.



XTreeGold
File manager programs for DOS and Windows from
Symantec (originally Central Point Software).
Introduced in 1985 for DOS by the Xtree Co., Xtree
was the first program to help users manage hard
disks by providing a hierarchical display of
directories.  Along with its file management
functions, XtreeGold includes file viewers for over
100 formats.



Xtrieve
A menu-driven query language and report writer from
Novell that accesses Btrieve files.



XVT
(EXtensible Virtual Toolkit)  A developers toolkit
for creating user interfaces across multiple
environments from XVT Software, Inc., Boulder, CO.
Programmers create the XVT functions, which are
translated to DOS, Windows, OS/2, PM or the Mac.



XWindows
See X Window.



XyWrite
Pronounced "zy-write."  PC word processing programs
from The Technology Group (XYQUEST division),
Baltimore, MD.  XyWrite word processors, including
XyWrite III and XyWrite III Plus, have been used
extensively by major newspapers and magazines
throughout the country.  XyWrite was noted for its
typesetting orientation long before it was common
to have the variety of fonts found in today's
software.

   XyWrite differs from most word processors in
that it generates a pure ASCII file like a text
editor.  Format commands are embedded within two
extended ASCII characters ( and ), which can be
revealed or kept hidden.  When hidden, the format
command displays as a triangle ().  XyWrite is
also noted for its complete customizability.  Using
a programmer-oriented macro language, you can cause
XyWrite to perform almost any text processing task.
Menus and keyboard commands can also be customized.
Up to nine document windows can be displayed on
screen at the same time.

   Signature, a version jointly developed by
XYQUEST (Billerica, MA) and IBM, was designed to be
the successor to XyWrite III Plus and IBM's
DisplayWrite.  It recognized XyWrite, DisplayWrite
and DCA documents directly.  XyWrite 4.0 for DOS
and XyWrite for Windows, which also have this
ability, are successors to both XyWrite III Plus
and Signature.

   Nota Bene, originally developed by Dragonfly
Software, adds indexed text retrieval,
bibliographic and citation management to XyWrite.
It is a self-contained product using the XyWrite
engine and is available separately.  In 1992, The
Technology Group acquired all of these products and
created the XYQUEST division.



y-axis
See x-y matrix.



yacc
(Yet Another Compiler Compiler)  A UNIX compiler
that is used to create C compilers.  Part of its
code is included in the generated compiler.  See
bison.



Yellow Book
The standard for the physical format of a CD-ROM
disk.  The ISO 9660 standard defines the logical
format for the disk.  See CD.



Yellow Pages
See NIS and naming service.



YIQ
The color model used for color TV.  The Y stands
for luminosity or lightness, which was the original
black and white TV signal.  The I and Q were added
to make color TV backward compatible with the black
and white standard.  Known as chromacity, the I and
Q signals are the color differences that are
derived from the difference between red, blue and
the luminosity (I=red-Y, Q=blue-Y).



Ymodem
A file transfer protocol identical to Xmodem-1K
plus batch file transfer (also called Ymodem
Batch).  It is faster than standard Xmodem and
sends the file name before sending the data.
Ymodem-G transmits without acknowledgment for
error-free channels or when modems are self
correcting, but transmission is cancelled upon any
error.



Z
A mathematical language used for developing the
functional specification of a software program.
Developed in the late 1970s at Oxford University,
IBM's CICS software is specified in Z.



z-axis
The third dimension in a graphics image.  The width
is the x-axis and the height is the y-axis.



Z180
See Z80.



Z280
See Z80.



Z380
A 16-bit version of the Z80 microprocessor from
Zilog Corporation.



Z39.50
An ANSI standard query language that is a
simplified version of SQL.  It is used on the
Internet to search for documents.  See WAIS.



Z80
An 8-bit microprocessor from Zilog Corporation that
was the successor to the Intel 8080.  The Z80 was
widely used in first-generation personal computers
that used the CP/M operating system.  Subsequent
Z180 and Z280 chips have also been widely used in
embedded systems with more than a half billion
shipped as of late 1994.



Z8000
A 16-bit microprocessor from Zilog Corporation that
was the successor to the Z80.  It was not widely
used.



zap
A command that typically deletes the data within a
file but leaves the file structure intact so that
new data can be entered.



ZBR
(Zone Bit Recording)  A technique that records more
bits on a disk.  The tracks on a disk become longer
the farther they are from the center.  However, on
regular disks, the clock rate that records the bits
doesn't change, which results in the outer tracks
being less densely packed than the inner tracks.
With ZBR, the clock rate is changed based on which
track is being written, and each track is filled to
capacity.



zenix
See SCO XENIX.



zero-slot LAN
Refers to transmitting between computers over a
serial or parallel port, thus freeing up an
expansion slot normally used by LAN cards (NICs).



zero wait state
Refers to a high-speed memory that transfers its
data immediately upon being accessed without
waiting one or more machine cycles to respond.



ZIF socket
(Zero Insertion Force socket)  A chip socket that
is easy to plug a chip into.  Intel has popularized
this type of socket with its OverDrive upgrades.
The chip is dropped into the socket's holes and a
small lever is turned to lock them in.



ZiffNet
An online information service for PC users from
Ziff-Davis Interactive, a division of Ziff-Davis
Publishing Company.  It provides a wide of variety
of shareware and public domain software as well as
technical forums and information.  ZiffNet can be
accessed via PRODIGY and CompuServe.  Address: 25
First St., Cambridge, MA 02141, 617/252-5000.  See
online services.



zinc air
A rechargeable battery technology that provides
more charge per pound than nickel cadmium or nickel
hydride and does not suffer from the memory effect.
It uses a carbon membrane that absorbs oxygen, a
zinc plate and potassium hydroxide as the
electrolyte.  AER Energy Systems, Smyrna, GA, is
the pioneer in this emerging battery technology.



zip
(1) To compress a file with PKZIP.  See PK
software.

(2) (ZIP) (Zig-Zag Inline Package)  Similar to a
DIP, but smaller and tilted on its side for
mounting on boards with limited space.

(3) (ZIP) A proprietary messaging protocol from
IBM.  PROFS uses ZIP for its e-mail transport.



Zmodem
A file transfer protocol that has become very
popular because it handles noisy and changing line
conditions very well, including satellite
transmission.  It sends file name, date and size
first, uses variable length blocks and CRC error
correction.  If a download is interrupted using
Zmodem or Ymodem, Zmodem will transmit only the
remainder of the file on the next try.  This is
great insurance when sending extremely long files.



zone bit recording
See ZBR.  Remember... try the acronym first!



Zoo
A freeware compression program, including source
code, used in UNIX, DOS and other environments.



zoom
To change from a distant view to a more close-up
view (zoom in) and vice versa (zoom out).  An
application may provide fixed or variable levels of
zoom.  A video display board (graphics adapter) may
also have built-in zoom, which provides zoom
capability for everything that is displayed
independent of and in addition to the application's
zoom levels.



Zortech compilers
A series of C and C++ compilers from Zortech Inc.,
which was acquired by Symantec in 1991.  Zortech
compilers are now called Symantec compilers.



zywrite
See XyWrite.



0K
(Zero Kilobytes)  Typically references motherboards
that do not include memory as priced.



0x
In programming, the symbol for a hexadecimal
number.  See x.



1-2-3
See Lotus 1-2-3.



1-bit DAC
(1-bit Digtal to Analog Converter)  A serial method
of converting digital samples back into analog form
for amplification.  Each bit of the sample is
converted into its analog weight rather than all
bits of the sample converted in parallel.  See
ladder DAC.



1.2M
Refers to the 1.2MB high-density 5.25" floppy disk
used in PCs.



1.44M
Refers to the 1.44MB high-density 3.5" disk used in
PCs.



100BaseT
See Fast Ethernet.



100BaseVG
See Fast Ethernet.



100VG-AnyLAN
See Fast Ethernet.



1024x768
Standard super VGA resolution of 1,024 columns by
768 rows (lines).  In the specification
1024x768x64K, the 64K is the number of colors.  See
resolution.



10Base2
An Ethernet standard that uses a thin coaxial
cable.  It attaches to the network nodes via BNC
connectors in the adapter cards.  Also called thin
Ethernet, ThinWire and ThinNet.  See Ethernet.



10Base5
The original Ethernet standard that uses a thick
coaxial cable.  It attaches to the network nodes
via transceivers that tap into the cable and
provide a line to a 15-pin plug in the adapter card
called an AUI connector.  Also called thick
Ethernet, ThickWire and ThickNet.



10BaseF
An Ethernet standard that uses optical fibers.  All
stations connect in a star configuration to a
repeater or to a central concentrator.  Connections
are made via ST or SMA fiberoptic connectors.
Adapter cards with AUI connectors are connected to
10BaseF networks via a fiber optic transceiver.

   The 10BaseFL standard defines the link between
the concentrator and a station; 10BaseFP defines a
star-coupled network; 10BaseFB defines a fiber
backbone.  See Ethernet.



10BaseT
An Ethernet standard that uses twisted wire pairs
(telephone wire).  All stations connect in a star
configuration to a central hub, also known as a
multiport repeater.  10BaseT is widely used due to
the lower cost and flexibility of installing
twisted pair.  See Ethernet.



123
See Lotus 1-2-3.



1280x1024
Standard super VGA resolution of 1,280 columns by
1,024 rows (lines).  In the specification
1280x1024x64K, the 64K is the number of colors.
See resolution.



1284
See IEEE 1284.



1401
A second-generation IBM computer introduced in 1959
and used until the late 1960s.  It had 16K of core
memory, six tape drives and used punched cards for
input.  It was an outstanding success due to its
reliability (18,000 installed).  For migration,
1401 emulators were built into IBM's 360 series.



16-bit
See bit specifications.



16-bit sample
A sample of a sound wave based on measuring the
wave on a scale of 65,536 increments.  A "16-bit
sound card" should mean that it takes 16-bit
samples; however, it could also mean that it
generates 8-bit samples, but fits into a 16-bit
slot.  See 8-bit sample.



16450, 16550
See UART.



24-bit color
Also called true color, it refers to using 24 bits,
or three bytes, per pixel to represent a color
image in a computer.  The 24 bits allows up to
16,777,216 colors to be stored and displayed.  See
bit depth and bit specifications.



2780, 3780
Standard communications protocols for transmitting
batch data.  The numbers originated with early IBM
remote job entry (RJE) terminals that included a
card reader and a printer.



286
The successor to the 8088 CPU used in the first PC
(XT-class).  Refers to the Intel 80286 CPU chip or
to a PC (AT class) that uses it.  It is more
responsive than an XT and isn't limited to its
infamous one-megabyte barrier, but is still
sluggish for Windows and graphics-intensive
applications.  See PC and x86.

              286 CPU Technical Specs
A 16-bit multitasking microprocessor in a 68-pin
PGA, PLCC or LCC package.  Has 15 16-bit registers
including eight general-purpose.  Operational
modes:  "Real Mode" performs as a fast 8086 CPU and
addresses 1MB memory.  "Protected Mode" addresses
16MB physical and 1GB virtual memory and provides
access to memory protection capabilities.  Contains
130,000 transistors.



286/12, 286/16...
The designation of CPU speed for a 286.  The second
number is the clock rate: 286/12 means 12MHz.



3 C's
See "PROCESSING" under computer.



3-D sound
A variety of sound reproduction systems that
produce a more realistic or higher quality sound.
Some methods produce delays or special effects in
one or more of the speakers.  Virtual reality
systems may use speakers above and below as well as
on the sides.



3.3v
(3.3 Volts)  Refers to the amount of voltage
required by the chips on newer personal computer
motherboards.  See 5v.



3.5"
(1) Refers to the common 3 1/2 inch microfloppy
disk used in personal computers.

(2) Refers to disk drives and other devices with a
3 1/2 inch horizontal form factor.



303x
A series of medium to large-scale IBM mainframes
introduced in 1977, which includes the 3031, 3032
and 3033.  See IBM mainframes.



308x
A series of large-scale IBM mainframes introduced
in 1980, which includes the 3081, 3083 and 3084.
See IBM mainframes.



3090
A series of large-scale IBM mainframes introduced
in 1986.  Before the ES/9000 models (System/390),
3090s were the largest mainframes in the System/370
line.  Models 120, 150 and 180 are single CPUs.
Models 200 through 600 are multiprocessor systems
(first digit indicates the number of CPUs).  The E,
S and J models represent increased speed
respectively.  See IBM mainframes.



32-bit color
Using 24 bits per pixel to represent a color image
in a computer, plus an additional eight bits for an
alpha channel.  See 24-bit color, alpha channel,
bit depth and bit specifications.



32-bit disk access
See FastDisk.



32-bit file access
See Windows for Workgroups.



32-bit processing
In a PC with a 386 or higher CPU, this refers to
programs written for the 386's 32-bit mode, which
is its fastest mode of operation.  Starting with
the 386, Intel CPUs have a split personality in
order to maintain backward compatibility with
previous CPUs.  They can process 16-bits, or two
bytes at a time, or process 32-bits, or four bytes
at a time.

   In the 386's Real Mode, a program can execute
16-bit instructions.  In Protected Mode, a program
has access to both 16-bit and 32-bit instructions,
the maximum amount of RAM, virtual memory and
virtual machine capabilities as well as memory
protection, which keeps one program from crashing
another.

   DOS applications run in Real Mode, while Windows
switches back and forth between Real Mode and
Protected Mode.  OS/2, UNIX, Windows NT, Windows 95
and other 32-bit operating systems run in the
machine's Protected Mode to take advantage of the
CPU's advanced capabilities.



3270
A family of IBM mainframe terminals and related
protocols (includes 3278 mono and 3279 color
terminal).  See 3270 emulator.



3270 Data Stream
The format for transmitting data from an
application to a 3270-type terminal.



3270 emulator
A plug-in board that converts a personal computer
or workstation into an IBM mainframe terminal.  The
first 3270 emulator was the Irma board from DCA,
Inc.



34010, 34020
General-purpose microprocessors from TI that are
optimized for graphics and conform to the TIGA
interface.



3480, 3490
Two series of 1/2" magnetic tape cartridge drives
from IBM that are used with mainframes and AS/400s.
The 3480 units store two bytes from top to bottom
on 18 parallel tracks at 38000 bpi.  The 3490s
store two or four bytes on 18 or 36 parallel tracks
at 38000 bpi.



360
See System/360.



360K
May refer to the 360K 5.25" minifloppy disk used
with PCs.



370
See System/370.



370 architecture
Refers to a computer that will run IBM mainframe
applications.  See System/370 and IBM mainframes.



370/XA
(370 EXtended Architecture)  A major enhancement
(1981) to System/370 architecture which improved
multiprocessing, introduced a new I/O system and
increased addressing from 24 to 31 bits (16MB to
2GB).



3770
The standard communications protocol for batch
transmission in an IBM SNA environment.



3780
See 2780, 3780.



37xx
IBM communications controllers that includes the
3704, 3705, 3720, 3725 and 3745 models.  The 3704
and 3705 are early units, and the 3745 models are
newer and more versatile.  The 3745 includes a
cluster controller that can connect 512 terminals,
eight token ring networks and 16 T1 lines.



386
The successor to the 286.  Also known as the 386DX,
it refers to the Intel 386 CPU chip or to a PC that
uses it.  The 386 is faster than the 286 and
provides a more sophisticated method for running
multiple DOS programs.  It is more responsive than
the 286, but is still relatively slow for Windows
and graphics-based applications.  The 386
architecture has been followed in all of Intel's
subsequent CPUs (486, Pentium, etc.).

   The 386 addresses more memory than the 286, and
provides enhanced memory management by allowing
both extended and expanded (EMS) memory to be
allocated on demand.  See PC and x86.


              386 CPU Technical Specs
A 32-bit multitasking microprocessor in a 132-pin
PGA package.  Supports 8, 16 and 32-bit data types.
Has 32 32-bit registers including eight general-
purpose.  Operational modes:  "Real Mode" performs
as a fast 8086 CPU and addresses 1MB memory.
"Protected Mode" addresses 4GB physical and 64TB
virtual memory and provides access to memory
management, paging and memory protection
capabilities (see 32-bit processing).  "Virtual
8086 Mode" is a Protected Mode subset that runs
tasks as if each were in an individual 8086 CPU.
See Virtual 8086 mode.

   The 386 uses 1.5 micron technology (transistor
elements are as small as 1.5 microns).


                 386 CPU Family

   386 Version  Clock  Bus           Number
   (Word size   Speed  Size Maximum    of
      in bits)  (MHz) (bits)  RAM  Transistors
   
     386DX     16-40  32   4G   275,000
      (32)                     
                               
     386SX     16-33  16   16M  275,000
      (32)                     
                               
     386SL     20-25  16   32M  857,000
      (32)                     





386/25, 386/33...
The designation of CPU speed for a 386.  The second
number is the clock rate: 386/25 means 25MHz.



386 Enhanced Mode
An operational mode in Windows.  See Windows.



386DX
See 386.



386MAX
A DOS memory manager for 386s and up from Qualitas,
Inc., Bethesda, MD, noted for its advanced
capabilities.  BlueMAX is a version for PS/2
models.



386SL
A version of the 386SX designed for laptops.   It
has built in power management, and its variable
clock rate allows it to idle for long suspend and
resume periods.  Except for memory and video
controller, the 386SL and the 82360SL chip make up
almost the entire computer.  See x86.



386SLC
An IBM version of the 386SX that includes an
internal 8KB memory cache.  It includes power
management capabilities and runs as fast as a
386DX.



386SX
A version of the 386 from Intel that runs at slower
speeds than the 386DX, addresses only 16MB of
memory (not 4GB) and supports only a 16-bit data
bus (not 32).  It uses less power and dispells less
heat than the 386DX.  See 386SL and x86.



387
Math coprocessor for the 386.



390
See System/390.



3Com 3+
A network operating systems from 3Com Corporation,
Santa Clara, CA.  3+Share is a DOS-based system
that supports PC and Mac clients.  3+Open is OS/2
based and supports DOS, OS/2 and Mac clients.

   In 1993, 3Com discontinued its network operating
systems business to remain in hardware, offering a
wide variety of network adapters, hubs and related
products.  3Com was founded in 1979 by Bob
Metcalfe.



3DO
A multimedia and video game technology from 3DO
Company, Mountain View, CA.  It is licensed to
manufacturers and developers.  The first 3DO player
is Panasonic's REAL (Realistic Entertainment Active
Learning) Multiplayer, which plays audio CDs and
can be fitted for Video CDs.

   3DO developers are able to create games from a
large library of royalty-free sound effects, music,
stills, clip art and film.  The technology provides
very high speeds for animation and can also provide
a 3-D capability that is viewed through glasses.

   3DO was founded by Trip Hawkins, one of Apple's
earliest employees and founder of Electronic Arts
software company.  In 1990, Hawkins left Electronic
Arts to start 3DO.



3GL
See third-generation language.



4004
The first microprocessor.  Designed by Marcian E.
"Ted" Hoff at Intel, it was a 4-bit, general-
purpose CPU initially developed for the Japanese
Busicom calculator.



43xx
A series of medium-scale IBM mainframes initially
introduced in 1979, which include the 4300, 4321,
4331, 4341, 4361 and 4381.



486
Also known as the 486DX, it refers to the Intel 486
CPU chip or to a PC that uses it.  It is the
successor to the 386 and has become the entry-level
machine in the Intel x86 line.  Depending on clock
rates, it runs from two to five times as fast as a
386 and provides the minimum speed necessary for
Windows, CAD and other graphics-intensive
applications.  Its built-in math coprocessor is
often required by CAD applications.

   Intel has improved the performance of the 486 by
offering versions with double and triple the
internal speed while maintaining the same external
speeds and connections (see DX2 and DX4).  See
OverDrive chip, PC and x86.

              486 CPU Technical Specs
A 32-bit multitasking microprocessor in a 168-pin
PGA package.  It uses the same registers and
operational modes as the 386 (see 386 and 32-bit
processing).  It obtains its speed from an internal
8KB memory cache that it quickly fills in burst
mode.

   The 486DX chip contains 1.2 million transistors;
the 486SX contains 1.1 million.  Both use 1.0
micron technology (transistor elements are as small
as one micron).



486/25, 486/33...
The designation of CPU speed for a 486.  The second
number is the clock rate: 486/25 means 25MHz.  CPUs
beyond 33MHz may have different internal and
external speeds as noted in the following table.
See 486.

               Internal           External
              Clock Speed        Clock Speed
              (calculate,        (to RAM and
              compare, etc.)     external bus)

    486/25        25MHz            25MHz
    486/33        33MHz            33MHz
    486/50        50MHz            50MHz
    486/50DX2     50MHz            25MHz
    486/66        66MHz            33MHz
    DX4/75        75MHz            25MHz
    DX4/100      100MHz            33MHz





486DLC
A 486SX-compatible CPU from Cyrix Corporation that
is pin compatible with the 386DX.  Designed for
upgrading 386s, it comes in a variety of speeds
including clock doubling versions.



486DX
See 486.



486DX2
See 486.



486SL
A version of the 486 from Intel designed for
laptops.  It runs on 3.3 volts (instead of 5) and
includes power management features like the 386SL.



486SLC
(1) A 486SX-compatible CPU from Cyrix Corporation
that is pin compatible with the 386SX, has a 1K
cache and uses a 16-bit bus.  It provides an
upgrade path for 386SXs.

(2) The IBM version of the 486SX.



486SX
A version of the 486 from Intel that runs at slower
clock speeds than the 486DX and does not include
the math coprocessor.  486SXs can be upgraded to
486DX2s with Intel's OverDrive chip, which includes
the coprocessor.  The DX2 chip is plugged into the
empty coprocessor socket, disabling the original
CPU.  See 486.



487
The math coprocessor for the 486.



4DOS
A popular DOS command processor from JP Software
Inc., East Arlington, MA, that replaces DOS'
COMMAND.COM file.  It includes enhanced commands
that allow multiple files to be referenced with a
single command.  For example, you can copy several
files with different names with one copy statement,
which would require a copy statement for each file
in DOS.



4GL
See fourth-generation language.



4mm tape
See DAT.



5.25"
(1) Refers to the common 5 1/4 inch floppy disk
used in personal computers.

(2) Refers to disk drives and other devices with a
5 1/4 inch horizontal form factor.



5100
The first IBM desktop computer (1974).  It came
with up to 64K of RAM, a built-in tape drive and
used APL or BASIC.  Eight inch floppy disks became
available in 1976.



5250
A family of terminals and related protocols for IBM
midrange computers (System 3x, AS/400).



5250 emulator
Same as twinax card.



586
See Pentium.



5v
(5 Volts)  Refers to the amount of DC electricity
required by the chips on most personal computer
motherboards.  The power supply converts 120v
alternating current (AC) into 5v direct current
(DC).  It also generates 12v for the disk drives.
See 3.3v.



601
The first model of the PowerPC.  See PowerPC.



603
A low-power PowerPC chip designed for notebooks and
portable applications.  See PowerPC.



604
The second model of the PowerPC.  It is expected to
be up to four times as fast as the 601.  See
PowerPC.



615
An IBM version of the PowerPC that provides x86
emulation on the chip itself.  It is expected that
the 615 will run DOS and Windows applications at
the rate of a 486/66.  The chip is expected in
1995.



620
A third model of the PowerPC chip.  See PowerPC.



64-bit
See bit specifications.



640K
(640 Kilobytes)  Typically refers to the first 640
kilobytes of memory in a PC, known as conventional
memory.  See PC memory and PC memory map.



640x480
Standard VGA resolution of 640 columns by 480 rows
(lines).  In the specification 640x480x16, the 16
is the number of colors.  See resolution.



650
IBM's first major computer success.  Introduced in
1954, it used magnetic drum memory, magnetic tape
and punched cards.  By the end of the 1950s, there
were an estimated 1,800 units installed, making it
the most widely used computer in the world.



6502
An 8-bit microprocessor from Rockwell International
Corporation used in the Apple II and earlier Atari
and Commodore computers.



6800
An 8-bit microprocessor from Motorola.  The 6801 is
a computer-on-a-chip version.



68000
A family of microprocessors from Motorola that are
the CPUs in Macintoshes and a variety of
workstations.  It is also known as the 68K or 680x0
series.

68000 - 32-bit CPU that can address up to 16MB of
        memory and uses a 16-bit data bus.

68020 - 32-bit CPU that can address up to 4GB of
        memory and uses a 32-bit data bus.

68030 - 32-bit CPU that can address up to 4GB of
        memory and uses a 32-bit data bus.  The
        68030 runs at higher clock speeds than the
        68020 and has built-in cache memory.

68040 - Redesigned version of the 68030 that can
        run up to three times as fast.





680x0
Refers to the Motorola 68000 family of CPU chips or
to applications that are written for that chip.
See 68000.



686
See P6.



68K
See 68000.



7-bit ASCII
Refers to transferring ASCII text in which an 8-bit
byte holds the ASCII character plus a parity bit.
Some PBXs allow only 7-bit transmission.



7-track
Refers to older magnetic tape formats that record
6-bit characters plus a parity bit.



720K
May refer to the 720K microfloppy disk used in PCs.



750
See i750.



786
See P6.



8-bit
See bit specifications.



8-bit sample
A sample of a sound wave based on measuring the
wave on a scale of 256 increments.  See 16-bit
sample.



8-N-1
(8 bits, No parity, 1 stop bit)  Common parameters
for modem transmission.



800x600
Standard super VGA resolution of 800 columns by 600
rows (lines).  In the specification 800x600x256,
the 256 is the number of colors.  See resolution.



80186/80188
An integrated version of the 8086/8088 CPU that
includes additional system components, such as the
clock, DMA and interrupt controller, on the same
chip.



802.1
An IEEE standard for network management.  See IEEE
802.



802.12
An IEEE standard for a demand priority local area
network access method, which is implemented in Fast
Ethernet.  See IEEE 802 and Fast Ethernet.



802.2
An IEEE standard that specifies the data link layer
for various media access methods.  See IEEE 802.



802.3
An IEEE standard for a CSMA/CD local area network
access method, which is widely implemented in
Ethernet.  See IEEE 802.



802.4
An IEEE standard for a token bus local area network
access method, which is used in the MAP factory
automation protocol.  See IEEE 802.



802.5
An IEEE standard for a token ring local area
network access method, which is widely implemented
in Token Ring.  See IEEE 802.



802.6
An IEEE standard for a DQDB metropolitan area
network access method.  See IEEE 802.



80286
See 286.



80287
See 286.



80386
See 386.



80386DX
See 386.



80386SL
See 386SL.



80386SX
See 386SX.



80387
See 386.



80486
See 486.



80486DX
See 486.



80486SX
See 486SX.



80487
See 486SX.



8080
An Intel 8-bit CPU chip introduced in 1974.  It was
the successor to the first commercial 8-bit
microprocessor (8008) and precursor to the x86
family.  It contained 4,500 transistors and other
electronic components.



8086
Introduced in 1978, the CPU chip that defines the
base architecture of Intel's x86 family (XT, AT,
386, 486, Pentium).  8086s are used in some XT-
class machines.  See PC and x86.


             8086 CPU Technical Specs
A 16-bit microprocessor in a 40-pin CERDIP package.
Has 14 16-bit registers including eight general-
purpose.  Addresses 1MB memory using base addresses
contained in segment registers.  Contains 29,000
transistors.



80860
See 860.



8087
The math coprocessor for the 8086/8088.



8088
The Intel CPU chip used in first-generation PCs (XT
class).  It is a slower version of the 8086, chosen
for migration from CP/M programs, the predominate
business applications of the early 1980s.  See PC
and x86.

             8088 CPU Technical Specs
Same as the 8086 CPU except that is uses an 8-bit
data bus instead of a 16-bit data bus.  Designed to
ease conversion from 8-bit, Z80-based CP/M
programs.  Contains 25,000 transistors.



80x86
See x86.



8100
An IBM minicomputer introduced in 1978 that was
designed for departmental computing and used the
DPPX/SP operating system.



82385
An Intel controller chip that manages the memory
cache in 386 and 486 CPUs.



82489DX
Known as the Advanced Programmable Interrupt
Controller, it is the successor to the 8259A
interrupt controller.  The 82489DX is enhanced for
multiprocessing.  See IRQ and PIC.



8250A
See UART.



8259A
Known as a Programmable Interrupt Controller, it is
the interrupt controller chip used in a PC.  It is
superseded by the 82489DX chip.  See IRQ and PIC.



8514
The IBM monitor used with its 8514/A display
adapter.



8514/A
An IBM high-resolution display adapter that
provides an interlaced display of 1024x768 with 256
colors or 64 shades of gray.  It contains an on-
board coprocessor for performing 2-D graphics and
it is designed to coexist with VGA for dual monitor
capability.  Introduced on Micro Channel machines,
third-party vendors provide non-interlaced versions
for the ISA bus.



860
See i860.



88000
A family of 32-bit RISC microprocessors from
Motorola.  The 88100 is the first processor in the
88000 family.  Introduced in 1988, it incorporates
four built-in execution units that allow up to five
operations to be performed in parallel.  Although
the 88000 processors are very sophisticated chips,
they never took off in the marketplace.  See
88Open.



88K
See 88000.



88Open
A consortium founded in 1988 that provides
information and certification for the Motorola
88000-based platform.  Companies such as Data
General, Encore and Harris offer products using the
88K chips.



8mm tape
A tape format used in high-capacity tape drives for
backup.  See Exabyte.



9-track
Refers to magnetic tape that records 8-bit bytes
plus parity, or nine parallel tracks.  This is the
common format for 1/2" tape reels.



9370
A series of IBM entry-level mainframes introduced
in 1986 that use the 370 architecture.  In 1990,
the Enterprise System models (ES/9370) were
introduced, which use the Micro Channel bus and a
386 for I/O processing.  The ES/9370 Model 14
biprocessor system adds a second 386 that can run
DOS and OS/2 applications.  A high-speed link is
available between the 386 and 370 processors.



9660
See ISO 9660.




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