Atari XL User Manual

114
The Atari XL Handbook
bit distracting, and there is a way of removing the
mode 0 window, allowing the entire screen to be
given over to mode 1 or 2 displays. To achieve this
simply add 16 to the mode number, so that mode 1
without a mode 0 window is obtained by typing:
GRAPHICS 1+16
Try changing line 20 in the previous program to see
this. The penalty is that if the program is halted
for any reason, the XL will return to mode 0-
losing your display.
One drawback of being able to specify one of four
colours for a mode 1 or 2 display is that only 64
characters can be represented by codes 0 to 255.
This restricts us to using only upper case letters in
the previous examples, which is only half of the
available character set. To display the other half of
the character set, we must change the place from
which the XL obtains its characters by PO KEing
the character set pointer (location 7:56) with the
number 226 (its default value is 224). Don't worry
too much about what this means - all will become
clear later in this chapter.
The following program, in a romantic vein,
demonstrates the use of the other half of the
character set in mode 2.
10 MODE=2+16
20 GRAPHICS MODE
25 SETCOLOR 0,3,8
30 POKE 756,226
35 FOR CHAR=2 TO 17
40 READ DATA
50 COLOR DATA:PLOT CHAR,4
60 NEXT CHAR
65 REM LOOP TO FLASH MESSAGE
70 FOR LUM=O TO 14 STEP 2
80 SETCOLOR 1,12,LUM

Atari XL Specifications

General

Brand	Atari
Model	XL
Category	Desktop
Language	English