APPENDIX FIFTEEN __________________________________________________________



XL/XE Graphics Modes
The new graphics modes are 12, 13, 14, and 15 in BASIC; ANTIC
modes 4, 5, 12 ($C), and 14 ($E), respectively. These have always
been available internally, but BASIC programmers had to trick the
OS to get at them.

GRAPHICS 12 is a four-color text mode (plus background). Each
character on the screen is the same height as a GRAPHICS 0 charac-
ter (8 scan lines), but only four pixels get displayed instead of eight.
The screen has 20 lines (24 with GRAPHICS 12 + 16) and 4 lines of
text, using 40 bytes of RAM per screen line.

GRAPHICS 13 is another four-color text mode (plus background), but
this time the characters are double the size of GRAPHICS 0 characters
(16 scan lines high), while only four pixels are displayed (the system
interprets the character set by bit pairs rather than single bits; see
below). The screen has 10 lines (12 with GRAPHICS 13 + 16), also
using 40 bytes per screen line.

Since both GRAPHICS 12 and 13 display only four bits in each line of
character definition, the color of the pixel displayed depends on the
bit pair in the byte being addressed:

Bit Pair   Color   RAM Location
   00      BAK         712
   01      PF0         708
   10      PF1         709
   11      This depends on bit 7 of the byte.
           If bit 7 = 0, then use PF2 (at 710),
           else use PF 3 (at 711).

Note that each line in a character set definition (eight lines, one byte
wide, form one character) can have different color combinations.
Since bit pairs (one color clock) are displayed, the normal character
set becomes unrecognizable. In order to use these modes, you should
build a character set in which each character is half a letter and
can be combined for display. Or build a 7 X 7 character set with a
blank row and column between each character.

The characters displayed are not the full character set. They are
only one half of the ATASCII set, depending on the value in location
756 ($2F4): 224 ($E0) for uppercase, 226 ($E2) for lowercase. When
using GET or PUT operations in these modes, the lower seven bits
(0-6) are used for character data (allowing a range from 0 to 127;
$7F), while the high bit is the color modifier (see the table above).

GRAPHICS 14 is a two-color mode with a resolution of 160 pixels
wide (half the horizontal distance of GRAPHICS 8) and 192 high (160
with text lines). Each screen line is one scan line high, compared