Character Decimal Code Hexadecimal Code

1 49 31 ~,

2 50 32

3 51 33

4 52 34

5 53 35

6 54 36

7 55 37

8 56 38

9 57 39

' 58 3A

' 59 3B

< 60 3C

= 61 3D

> 62 3E

63 3F

@ 64 40

A 65 41

B 66 42

C 67 43

D 68 44

E 69 45

F 70 46

G 71 47

H 72 48

I 73 49

74 4A

K 75 4B

L 76 4C

M 77 4D

N 78 4E

O 79 4F

P 80 50

Q 81 51

R 82 52

S 83 53

T 84 54

U 85 55

V 86 56

W 87 57

X 88 58

Y 89 59

Z 90 5A

C ( s Hi~ 0) 91 5B

9-2

Displaying Text and Graphics l 9

Character Decimal Code Hexadecimal Code

\ ( SHIFf CLEAR ) 92 5C

( sHm 0) 93 5D

94 5E

-~ ( sHm CED 95 5F

96 60

a 97 61

b 98 62

c 99 63

d 100 64

e 101 65

f 102 66

g 103 67

h 104 68

i 105 69

j 106 6A

k 107 6B

1 108 6C

m 109 6D

n 110 6E

0 111 6F

p 112 70

q 113 71

r 114 72

s 115 73

t 116 74

u 117 75

v 118 76

w 119 77

x 120 78

y 121 79

z 122 7A

{ 123 7B

124 7C

} 125 7D

126 7E

127 7F

You can generate the characters in this chart by pressing the appropriate key, or you can generate them from BASIC09 using the CHR$ function.

In addition to alphanumeric characters, low-resolution graphics also offers graphic characters. Generate these characters by pressing ACT at the same time you press a keyboard character. The graphics character codes are in the range 128-255.

Pressing ACT while pressing another key, causes OS-9 to add 128 to the ASCII value of the second key. (For the technically minded, OS-9 sets the high bit of the character code.) Therefore, if you press ACT 0, you produce graphics character 193. You can also generate graphics characters from BASIC09 using the CHR$ function, and you can PRINT them in the same manner as other characters.

Low-level graphics characters follow a pattern that repeats every 16 characters. Table 9.2 shows the first set of graphic characters, 128-143. Subsequent characters produce the same series of configurations but display in different colors, as shown in Table 9.3.

Table 9.2

Low-Resolution Graphic Character Set

128 132 136 140

129

135

138

9-4

Table 9.3

Low-Resolution Graphics Color Set

ASCII Code Graphics Block Color

128 - 143 Black and Green

144 - 159 Black and Yellow

160 - 175 Black and Blue

176 - 191 Black and Red

192 - 207 Black and Buff

208 - 223 Black and Light Blue

224 - 239 Black and Cyan

240 - 254 Black and Orange

255 Green

To calculate a character that has orange at Sections 8 and 1, add the section values to the first value in the orange group, 240, like this:

The following diagram shows how you might block out a large letter O on the screen. The shaded portions of the characters are colored. The unshaded portions are black. In this case we want the colored portions to be green (the same color as the screen). You can do this using the color set 1,28 - 143.

Because Section 1 in the upper left character is to be colored, add 1 to the initial character value of 128. The first character value is 129. Moving right, Sections 2 and 1 are colored in the second character. Add 3 to 128 to get a second character value of 131. Calculate all 15 characters in this manner.

You could create a letter O in a BASIC09 procedure by printing each of the five rows of three characters. You could use DATA lines to store the ASCII codes for each character, then use loops to read and display the characters they represent.

Although low-level graphics is very rough, it can be useful, and it lets you mix graphics with text.

The following procedure not only creates the letter O, it adds the letter S and the number 9 to display the name of your operating system.

9-6

143

High-resolution graphics does not have graphic characters but it does have other international and special characters. These characters are represented by ASCII codes 128 through 159 as shown in the following table:

Table 9.4

High-Resolution Special Characters

80 128 0 90 144

u 81 129 Be 91 145

e 82 130 AE 92 146

83 131 0 93 147

a 84 132 6 94 148

a 85 133 0 95 149

a 86 134 a 96 150

87 135 a 97 151

e 88 136 0 98 152

e 89 137 O 99 153 ,, ,,

e 8A 138 0 9A 154

i 8B 139 § 9B 155

i 8C 140 £ 9C 156

13 8D 141 ± 9D 157

A 8E 142 9E 158

A 8F 143 f 9F 159

For more sophisticated graphics operations, OS-9 has built-in graphics interface modules that provide a convenient way to access the graphics and joystick functions of the Color Computer 3. The required module for medium-resolution graphics is named GFX. It must be in your execution directory or resident in memory when called by BASIC09.

You can either install GFX in memory using the LOAD command, or wait until BASIC09 calls it for a graphics function. Once loaded, GFX resides in memory until you remove it using the OS-9 UNLINK command or the BASIC09 KILL command.

JOYSTK Returns the joystick button and X- and Ycoordinate status.

X- and Y-coordinates.

9-9

In medium-resolution graphics, you have a choice of two formats. Format 0 provides 256 horizontal points by 192 vertical points. In this format, you can have only two colors on the screen at a time.

Format 1 provides a 128 by 192 point screen and a maximum of four colors on the screen at a time. OS-9 medium-resolution graphics treats the screen as if it were a grid, with coordinate 0,0 at the lower left corner as shown in the following illustration. All points on the grid are positive.

Y-coordinate,0 - I

I I I I I I I I I I I I I I I I I

0, X-coordinate

BASIC09 defines colors with numbers or color codes. Many GFX functions allow or require color codes as parameters. BASIC09 also divides the color codes into color sets. Specifying a color code outside the current color set automatically initializes the new set.

Color

Set

Format 0

Format 1

Table 9.5

Use the preceding charts to chose colors for those functions that let you specify foreground or background colors. For instance, to initialize a Format 1 graphics screen with a green background and a red foreground, you type:

The following reference section describes all the medium-resolution graphics functions, and provides examples and sample programs. To understand the organization of the commands reference, see "The Syntax Line" in Chapter 11.

9-11

BASIC09 Reference

The Draw Pointer

Medium-resolution graphics uses a draw pointer, or invisible graphics cursor, to determine what area of the screen is affected by graphics operations. When you establish a graphics screen, the draw pointer is located at coordinates 0,0. Some graphic functions automatically change the pointer location on the screen. Fbr instance, the LINE function moves the draw pointer from the beginning coordinates to the end coordinates.

Because some functions begin at the draw pointer, you need to keep track of its location and make certain it is placed properly. Use the MOVE function to set the draw pointer to new locations.

9-12
Displaying Text and Graphics / 9

ALPHA Select alphanumeric screen

tax: RUN GFX("ALPHA")

Function: Switches from the graphics screen to the alphanumeric (text) screen. The current graphics screen remains intact.

Parameters: None

RUN GFX("ALPHA")

Sample Program:

This procedure lets you choose to draw a circle or rectangle of
the size you select. Once you choose the shape and size, it uses the MODE function to select a graphics screen. When the shape is complete, you press ENTER to return to a text screen. The procedure uses the ALPHA function to return to the original menu.

PROCEDURE alpha
ODIM XCOR,YCOR,SIDE1,SIDE2,RADIUS,T,X,Y,Z:INTEGER
ODIM RESPONSE:STRINGL1J
10 REPEAT
OSHELL "DISPLAY 0C"
OPRINT "Do you want to draw"
OPRINT "1) A rectangle"
OPRINT "2) A circle"

OPRINT " -Press 1 or 2..."
OGET #O,RESPONSE
pPRINT
OI F RESPONSE="1 " THEN

OINPUT "Length of Side 1...",SIDE1
OINPUT "Length of Side 2...",SIDE2
ORUN GFX("MODE",0,0)
ORUN GFXC"CLEAR")
OXCOR-10
DYCOR=10
ORUN GFX("LINE",XCOR,YCOR,XCOR+SIDE1,YCOR,1)

9-13
BASIC09 Reference

pRUN GFXC"LINE",XCOR+SIDE1,YCOR,XCOR+SIDE1,YCOR+
SIDE2,1 )
ORUN GFXC"LINE",XCOR+SIDE1,YCOR+SIDE2,XCOR,YCOR+
SIDE2,1 )
ORUN GFXC"LINE",XCOR,YCOR+SIDE2,XCOR,YCOR,1)
DINPUT RESPONSE
pELSE
OIF RESPONSE="2" THEN
OINPUT "What radius?...",RADIUS
ORUN GF X C "MODE" , 0 , 1 )
ORUN GFXC"CLEAR")
ERUN GFXC"CIRCLE",128,90,RADIUS)
DINPUT RESPONSE
pEND I F
pENDIF
OUNTIL RESPONSE<>"1" AND RESPONSEc>"2"
pRUN GFXC"ALPHA")
OGOTO 1 0
OEND

9-14

Displaying Text and Graphics l 9

CIRCLE Draw a circle

Syntax: RUN GFX("CIRCLE"[,xcorycor],radius [,color])

Function: Draws a circle of a given radius. If you do not specify a color, BASIC09 uses the current foreground color. If you do not specify X- and Y-coordinates, CIRCLE uses the current graphics cursor position as the circle's center.

Parameters:
radius The radius of the circle you want to draw.
color The code of the color you want the circle to be.
See the chart earlier in this section for color
information.
xcor,ycor The X- and Y-coordinates for the center of the
circle. Specifying coordinates outside the X
coordinate range of 0-255 or outside the Y
coordinate range of 0-191 causes an error.
Examples:
RUN GFX("CIRCLE",100)
RUN GFX("CIRCLE",100,3)
RUN GFX("CIRCLE",125,100,100)
RUN GFXC"CIRCLE", 1 25, 1 00, 1 00,2)

Sample Program:

This procedure uses CIRCLE to draw and erase a circle. The location of the circle changes before each draw/erase operation, causing the circle to move. When it hits the edge of the screen, it reverses its direction at a random angle and bounces.

PROCEDURE circles
ODIM RADIUS,XCOR,YCOR:INTEGER
ODIM XTEMP,YTEMP:INTEGER
ODIM PATH1,PATH2:INTEGER
ODIM FLAG:INTEGER

9-15

BASIC09 Reference

OFLAG=1
OXCOR=5
OYCOR=5
OPATH1 =RNDC1 5)+2
OPATH2=RNDC10)+2
OXTEMP-249
OYTEMP =185
ORUN GF X C "MODE" , 0 ,1 )
ORUN GFXC"CLEAR")
OFOR T=1 TO 200
OWHILE XCOR<250 AND XCOR>4 AND YCOR<186 AND YCOR>4
DO
ORUN GFXC"CIRCLE",XTEMP,YTEMP,3,0)
ORUN GFXC"CIRCLE",XCOR,YCOR,3,1)
OXTEMP=XCOR
OYTEMP=YCOR
OXCOR=XCOR+PATH1
OYCOR=YCOR+PATH2
OENDWHILE
pPATH1 =RNDC 1 5)+2
OPATH2=RNDC 1 0)+2
OIF XCOR>249 THEN
OXCOR=249
OEND I F
OIF XCOR<5 THEN
OXCOR=5
OEND I F
OI F YCOR> 185 THEN
EIYCOR-185
OENDIF
OIF YCOR<5 THEN
OYCOR=5
OEND I F
OFLAG=FLAG*-1
OIF FLAG<0 THEN
OPATH1 =PATH1 *-1
OPATH2=PATH2*-1
OENDI F
ONEXT T
OEND

9-16

Displaying Text and Graphics l 9

CLEAR Clear the screen

Syntax: RUN GFX("CLEAR"[,color])

Function: Clears the current graphics screen. If you do not specify a color, CLEAR sets the entire screen to the current background color. CLEAR also sets the graphics cursor at coordinates 0,0, the lower left corner of the screen.

Parameters:

color A code indicating the color to set the screen.

Examples:
RUN GFXC"CLEAR") RUN GFXC"CLEAR",14)

9-17
BASIC09 Reference

COLOR Change the foreground color

Syntax: RUN GFX("COLOR", color)

Function: Changes the foreground color (and possibly the color set). COLOR does not change the graphics format or the cursor position.

Parameters:

color A code indicating the color you want for the
foreground. See the chart earlier in this chap
ter for color information.
Examples:

RUN GFX("COLOR",10)

Sample Program:

This procedure connects a series of differently colored circles to produce a necklace effect.

PROCEDURE necklace
pDIM COLOR,T,U,J,R,FLAG,XCOR,YCOR:INTEGER
ORUN GFX("MODE",1,0)
pRUN GFX("CLEAR"
0COLOR=1
OX COR=1
OYCOR=1
OR=2
OFOR T=1 TO 6
pFOR J=1 TO 40
OXCOR=XCOR+1 _
OYCOR=YCOR+.8
OIF FLAG<O THEN
[]R=R-1
FlELSE
[]R=R+1
EIENDIF
0COLOR=COLOR+1
DIF COLOR>3 THEN COLOR=1

9-18

Displaying Text and Graphics / 9

OEND I F
ORUN GFXC"CIRCLE",XCOR,YCOR,R,COLOR)
ONEXT J
OFLAG=FLAG -1
ONEXT T
OFOR U=1 TO 10000
ONEXT U
REND

9-19
BASIC09 Reference

GLOC Find the graphics screen location

Syntax: RUN GFX("GLOC",storage)

Function: Determines the location of the graphics screen in memory and returns the address in the specified variable. When you know the graphic screen address, you can use PEEK and POKE to perform special functions not available in the GFX module, such as filling a portion of the screen with a color or saving a graphics screen to disk.

OS-9 Level Two maps display screens into a program's address space before PEEK and POKE can operate on a display screen. This means that you must have at least eight kilobytes of free memory in the user's address space. Program and data memory requirements must not exceed 56 kilobytes.

Parameters:

storage An integer or byte type variable in which
GLOC stores the memory address of the
graphics screen.
Examples:

RUN GFX("GLOC",location)

Sample Program:

This procedure uses the GLOC function to locate the current graphics screen, then uses POKE to paint a series of boxes on the screen.

PROCEDURE boxin
ODIM LOCATION,PLACE,COLOR,HEGIN,QUIT,X,TERMINATE,
LINE,T,J:INTEGER
ORUN GF X ("MODE" , 1 , 0 )
ORUN GFX("CLEAR")
RUN GFX("GLOC",LOCATION)
pLOCATION=LOCATION+100 \ PLACE=LOCATION
CHEGIN=1
pQUIT=80

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Displaying Text and Graphics l 9

oCOLOR=255 OTERM I NATE=1 0 OLINE=32 OFOR X=1 TO 4 OFOR Tml TO QUIT OFOR J=BEGIN TO TERMINATE OPOKE PLACE+J,COLOR ONEXT J OPLACE=PLACE+LINE ONEXT T OLOCATION=LOCATION+160 OBEGIN=BEGIN+1 OPLACE=LOCATION OQUIT=QUIT-1 0 OTERMINATE=TERMINATE-1 OCOLOR=COLOR-85 ONEXT X DI NPUT Z$ REND

9-21
BASIC09 Reference

JOYSTK Get joystick status

Syntax: RUN GFX ("JOYST K", stick,fire,xcor, ycor)

Function: Determines the status of the specified joystick fire button and the X,Y position of the specified joystick handle. Use this function only with a standard joystick or mouse, not with the high-resolution mouse adapter.

Parameters:

stick The joystick (0 or 1) for which you want to
determine the status. 0 indicates the right joy
stick, 1 indicates the left joystick.
fire A variable in which JOYSTK returns the sta
tus of the specified fire button. Fire can be
byte, integer, or Boolean type. A value other
than 0 or TRUE indicates the button is
pressed.
xcor,ycor Byte or integer type variables in which
JOYSTK stores the X- and Y-coordinates of
the joystick handle position. The coordinate
range is 0-63.
Examples:

RUN GFXC"JOYSTK",0,5hoot,x,y)

9-22

Displaying Text and Graphics / 9

Sample Program:

This procedure uses the JOYSTK function to draw on the screen with the right joystick.

PROCEDURE joydraw
ODIM STICK,FIRE,XCOR,YCOR,XTEMP,YTEMP:INTEGER
RUN GF X C "MODE" , 0 ,1 )
ORUN GFXC"CLEAR")
OJOY=0 \XCOR=0 \YCOR=0
OREPEAT
OXTEMP=XCOR
OYTEMP=YCOR
ORUN GFXC"JOYSTK",O,FIRE,XCOR,YCOR)
OXCOR=XCOR*4
OYCOR=YCOR*4
ORUN GFXC"LINE",XTEMP,YTEMP,XCOR,YCOR)
OUNTIL FIRE<>0
REND

w
BASIC09 Reference

LINE Draw a line

Syntax: RUN GFX ("LINE"[,xcorl, ycorl],xcor2, ycor2
[,color] )

Function: Draws a line in the current or specified foreground color in one of the following ways:

· From the current draw position to the specified X,Ycoordinates.

· From the specified beginning X- and Y-coordinates to the specified ending X,Y-coordinates.

Parameters:
xcorl,ycorl Are LINE's beginning X- and Y-coordinates.
xcor2,ycor2 Are LINE's ending X- and Y-coordinates.
color A code indicating the color you want the line
to be. See the chart earlier in this section for
color information.
Examples:
RUN GFXC"LINE",192,128)
RUN GFXC"LINE",0,0,192,128)
RUN GFXC"LINE",0,0,192,128,2)

9-24

Displaying Text and Graphics / 9

Sample Program:

This procedure draws a sine wave of vertical lines across the screen.

PROCEDURE waves
ODIM A,H,C,D,X,Y,Z:INTEGER
pCALC=0 \ A=100
pRUN GFXC"mode", 0, 1 )
ORUN GFXC"CLEAR")
ORUN GFXC"COLOR",2)
OFOR X=0 TO 255 STEP 1
pCALC=CALC+.05
DY=A-SINCCALC)*15
pZ=Y+25
ORUN GFXC"LINE",X,Y,X,Z)
ONEXT X
SEND

9-25
BASIC09 Reference

MODE Switch to graphics screen

Syntax: RUN GFX("MODE",forma t, color)

Function: Switches the screen from alphanumeric (text) to graphics, selecting the screen format and color code. You must run MODE before you can use any other graphics function. When you do, BASIC09 allocates a six-kilobyte block of memory for graphics. If your system does not have this amount of memory available, OS-9 returns an error message.

Parameters:

format Either 0 (a two-color 256 by 192 pixel screen)
or 1 (a four-color, 128 by 192 pixel screen).
color A code indicating the color to set the screen.
See the chart earlier in this chapter for infor
mation on color sets.
Examples:

RUN GFXC"MODE",1,2)

9-26