Introduction

Getting Started With OS-9 contains the information you must

know to use the system. However, the handbook reveals only a

small part of OS-9's capabilities. To learn about all of its fea

tures, you need to know more about how OS-9 works. This intro

duction provides such basic background information.


The Kernel

At the center of the OS-9 system is a module (program) called a

kernel. (See the following illustration.) The kernel provides basic

system services, such as multitasking and memory management.

It links other system modules and serves as the system adminis

trator, supervisor, and resource manager.


Figure 1

Term is your keyboard and video.

T1 and T2 are additional terminals.

P is a printer.

M1, M2, and M3 are modems.



OS-9 Commands Reference
The Input/Output Manager

Although the kernel manages OS-9, it does not directly process

the input and output of data among the other modules and your

computer hardware (printers, disk drives, terminals, and so on).

Instead the kernel passes this responsibility to the input/output

manager, IOMAN.


IOMAN has three submanagers: a character file manager, a pipe

file manager, and a disk file manager. The responsibilities of

these managers are as follows:


The Character Handles the transfer of data between OS-9
 File Manager and character devices (devices that operate
 on a character-by-character basis, such as
 terminals, printers, or modems). The
 sequential character file manager (SCF) can
 handle any number or type of such devices.
 The Pipe File Handles communication between processes
 Manager or tasks. Pipes let you use the output of one
 process as the input of another process.
 The Disk File This Random Block File Manager (RBF)
 Manager handles the transfer of data to and from
 block-oriented, random access devices, such
 as a disk drive system.
 Device Drivers

CC310, PIPER, and CC3DISK are device drivers. These files con

tain code that transforms standard data into a form acceptable

to a particular device, whether it is a terminal, printer, modem,

disk drive, any other device, or another file. PIPES transfers

data between processes.


Device Descriptors

Term, T1, P, M1, D0, and so on, are device descriptors. These

files describe the devices connected to the system. They contain

device initialization data as well as code that directs OS-9 to the

physical addresses of the ports to which devices are connected.



The Shell

The kernel, in conjunction with IOMAN and its associated man

agers and modules, make up the OS-9 operating system. These

modules handle all of the system's functions. However, OS-9

needs directions before it can accomplish useful tasks.


Directions to the system have two sources: commands and appli

cations or computer language programs.


Before commands are useful to the kernel, the shell must inter

pret them. It analyzes commands and converts them into code

that the kernel can understand.


Some application programs and computer languages also use the

shell's functions. Others can access the kernel directly and do not

need to go through the shell.


Going On

Chapters 2 through 5 contain detailed information on the opera

tion of the OS-9 system illustrated in Figure 1. These chapters

more fully describe the composition of files and directories. They

tell about advanced features of commands and of the shell and

contain information on multiprogramming and memory

management.


Chapter 6 contains descriptions of the OS-9 commands. Chapter

7 tells you how to use OS-9's Macro Text Editor.


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