Atari XL Handbook page 151

Graphics
141
program uses mode 10, which is a nine-colour
mode. Mode 10 is explained later in the chapter.
10 REM ABSTRACT XIO
20 GRAPHICS 10
30 XMAX=79: YMAX=191
40 POKE 704, 56
50
POKE 705, 24
60 POKE 706, 168
70 POKE 707, 88
80 SETCOLOR 0, 4, 10
90 SETCOLOR 1, 10, 8
100 SETCOLOR 2, 12, 4
110 SETCOLOR 3, 13, 14
120 SETCOLOR 4, 14, 6
200 X
=
RND(O)
*
XMAX
210 Y
=
RND(O)
*
YMAX
220 X2 = X+RND(O)
*
(XMAX - X)
230 Y2 = Y+RND(O)
*
(YMAX - Y)
240 C
=
RND(O)
*
8
250 COLOR C
260 PLOT X2, Y2
270 DRAWTO X2, Y
280 DRAWTO X, Y
290 POSITION X, Y2
300 POKE 765, C
310 XIO 18, #6, 0, 0,
"5:"
320 GOTO 200
The final graphics command is LOCATE. This
command moves the invisible graphics cursor to a
point on the screen and reads the colour of the pixel
at that point into a variable.
LOCATE X, Y, C
stores the colour (the colour register number) at X,
Y into C. The next program plots a point in a