Atari ST series Technical Reference Manual page 340

Value
0 Font is not monospaced, or size may vary due to special
effects.
1 Font is monospaced, and uses no special effects other than
thickening (boldface).
+ 072 to +073
The x coordinate of character to be printed in font form.
SOURCEX can usually be computed from information in the
font header:
ch = character to be printed - first_ade
SOURCEX = off_table[ch]
+ 074 to +075
The y coordinate of the character to be printed (usually 0).
+ 076 to +077
Horizontal screen position where character will be printed.
+ 078 to +079
Vertical screen position where character will be printed.
+ 080 to +081
Width of character. Can be computed from information in
the font header as follows:
ch = character to be printed - first__ade
SOURCEX = off_table[ch]
DELX = off_table[ch + 1] - SOURCEX
+082 to +083
Height of the character. Can be taken from the variable
form_height in the font header.
+ 084 to +087
The address of the font's character image data block. This ad-
332
APPENDIX H
Meaning
SOURCEX
SOURCEY
DESTX
DESTY
DELX
DELY
FBASE
( + $048 to + $049)
( + $04A to + $04B)
( + $04C to + $04D)
( + $04E to + $04F)
( + $050 to +$051)
( + $052 to +$053)
( + $054 to + $057)