Atari XL User Manual

Characters 133
o
1
2
Memory 3
Location:
4
5
6
7
:
:
::
Bit: 765432 10
The Multicolour Character Grid
program,which puts a letter Q in the centre of a
mode 13 screen. Mode 13 is used for clarity, the
principles apply equally to mode 12.
10 GRAPHICS 13
20 POSITION 18,4
30 PRINT#6;"Q"
The Q is just recognisable, and if you look closely
comprises three different colours. To see how these
colours originate, let's look at the eight bytes
defining the letter Q in character memory.
The diagram shows how the data for letter Q is
stored in the XL. In mode 0, each pixel is
represented by a single bit. In modes 12 and 13 .
however, the computer treats this data as four
grou ps of two hits, each specifying the colour
register from which information concerning that
pixel is to he taken.
If we take one row (one byte) and examine it in
more detail we will see how colour information is

Atari XL Specifications

General

Release Year	1983
CPU	MOS Technology 6502C
Graphics	ANTIC, GTIA
Sound	POKEY (4 channels)
Storage	Cassette tape
Ports	Cartridge
Operating System	Atari BASIC
CPU Speed	1.79 MHz
RAM	64 KB