Atari XL User Manual

110
The Ateri XL Handbook
case the destination is 6, which represents the
screen. This technique is commonly used to send
data to peripheral devices such as the cassette unit
(see Chapter 16) and here we are treating the
model screen as ifit were a peripheral device.
The colour and luminance of the message displayed
by the last program is controlled by colour register
0, and can be changed with the SETCOLOR
command. However it is possible to display
characters in up to four different colours on a mode
1 or 2 screen, as the following program
demonstrates.
10 GRAPHICS 1
20
PRINT#6;"REGISTER ZERO"
30 PRINT#6
40 PRINT#6;"register one"
50 PRINT#6
60 PRINT#6;"REGISTER TWO":REM
THIS TEXT IN REVERSE
70 PRINT#6
80 PRINT#6;"register three":REM
THIS TEXT IN REVERSE
Notice that regardless of the case specified in the
program, the messages on the screen are all in
upper case and those which would appear in
inverse video in mode 0 do not do so in mode 1. This
is because the additional information which would
affect case and inverse video in mode 0, is used to
select one of four colour registers to determine the
colour of the characters. The following table shows
which registers are selected by which type of text.
Characters can be positioned on the mode 1 and 2
screens using the POSITION command as in mode
0, but remember that because the characters are
larger than those in mode 0, the limits of screen
coordinates are correspondingly reduced.

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