Atari XL User Manual

Characters
107
higher the luminance number the brighter the
colour; so grey at luminance 0 will be black, but at
luminance 14 will appear white. Odd values for
luminance have the same effect as the lower even
number, so there is a choice of eight.
To see SETCOLOR in action, type in the following
program which cycles through the possible screen
and border colour combinations.
10 FOR COLR=O TO 15
20 FOR LUM=O TO 14 STEP 2
30
SETCOLOR 2,COLR,LUM
40 FOR
DELAY=O TO 200:NEXT DELAY
50 NEXT LUM
60 NEXT COLR
The program changes the contents of Register 2
which controls screen colour, if you change line 30
to:
30 SETCOLOR 4,COLR,LUM
the border colour will be affected. It is also possible
to al ter the luminance of the characters, by
altering register 1 as in this example, where
characters are made to flash by controlling their
luminance.
10 SETCOLOR 2,3,0
20 LUM = 14
30
SETCOLOR l,3,LUM
40 FOR PAUSE=O TO 100:NEXT PAUSE
50 LUM = 14-LUM
60
GOTO 30
38 OR 40 COLUMN SCREEN?
All our programs so far have used a screen display
of 38 columns by 24 rows, leaving a margin of two
characters at the left of the display. This margin is

Atari XL Specifications

General

Brand	Atari
Model	XL
Category	Desktop
Language	English