Atari XL - Page 140

130
The Atari XL Handbook
20030 PRINT"RELOCATING CHARACTER
SET"
20035 POSITION 5,22:PRINT "Please
wait approx. 25 seconds"
20040 CSET=256*PEEK(756)
20050 RAMSET=256*PEEK(106)
20060 FOR BYTE=O TO 1023
20070 POKE RAMSET+BYTE,PEEK
(CSET+BYTE)
20080 NEXT BYTE
20085 POKE 756,PEEK(106)
21000 DLIST=PEEK(560)+256*PEEK(561)
21010 SCRNST=PEEK(DLIST+4)+256*
PEEK(DLIST+5)
21020 GRIDST=SCRNST+245
25000 RETURN
The program allows you to redefine any character,
and to save character sets on tape and reload them.
You can use the new character sets with other
programs.
The first thing the progam does is create some
space for the character set and then copy the
character set into RAM. Lines 20020 to 20080 do
this. The rest of the lines in the setting up routine
find the start of screen memory (SCRNST) and
decide whereabouts on the screen the, character
grid is to be placed (GRIDST).
Lines 10000 to 10110 then display the menu,
giving you the option to change a character or to
load or save a character set. Pressing the ESC key
stops the program. -
The redefining of characters is controlled by the
routine from 200 to 550. When you input the code
of the character you wish to alter, the line 310 calls
the routine at lines 1000 to 1100 to store the data of