Atari XL - Page 127

Characters
INTERNAL CHARACTER CODES
117
The XL makes reference to the eight bytes defining
a character by assigning a code, known as the
Internal Character Code to each one. This is
different from the ASCII code, so to find the eight
bytes defining a character we must first convert the
ASCII code of that character to internal code. This
is done with the following formula:
INTERNAL=ASCII+{{ASCII<32)*64)-
({ASCII>31 AND ASCII<96)*32)
What this means is that the internal code is the
same as ASCII for codes greater than 95; for codes
less than 32 the internal code is greater by 64, and
for ASCII codes between 31 and 96, the internal
code is 32 less than ASCII.
Having worked out the internal code of a character,
to find the eight bytes which define it, we multiply
the internal code by eight, and add the start
address of the character set:
CHARACTER LOCATION =(INTERNAL
CODE*8)+{256*PEEK{756»
So the defini tion of the letter X (ASCII Code = 88;
Internal Code = 56) in the standard character set
is to be found at location:
56*8+{256*{PEEK(756» = 57792
This short program will display the eight numbers
defining any character.
1 REM DISPLAY CHARACTER DATA
5 OPEN#1,4,0,"K:"
10 PRINT"