Atari 800 User Manual

Atari BAS IC Reference Gu i de 165
EXAMPLE
10 GRAPHICS 2
20 PRINT #6; "ATAR I"
30 PRINT #6; "atari"
40 END
The
previous examp le contains a program that uses two PRINT
statement in graph i cs mode 2. At line 20, the PRINT statement
indicates I /O channe l number 6, w hich is used for graphics. To
determine which characters are to be printed, it is necessary to
consult Table 9-7 first. The upper case letters "ATARI" are
represented on Table 9-7 by the va lu es 65, 84, 65, 82, a nd 73. The
characters that correspond to these va lu es, on Table 9-4, are the
characters that wi ll be displayed. These values indi cate the
characters" AT ARI" in color register 0 from Table 9-4.
Similarly, the second PRI NT statement has the l ower case letters
"atari". These characters have the va lu es 97, 116 ,97, 114, a nd 105.
On Table 9-4, these va lu es correspond to the upper case letters
"ATAR I" in color register 1. As a r es ult of this program, the
message "ATAR I" appears in orange and in li ght green.
In graphics modes 3 throu gh 8, a PRINT statement illuminates
one picture ele ment for each character in the PRINT statement.
The co lor of the picture el ement is derived from the ASCII code
of the character. In the four-co l or grap hi cs modes (3 , 5, and 7),
the ASCI I codes is reduc ed modulo 4 to a number from 0 to 3.
This
value corresponds to the color value of the picture eleme nt.
In
the two-color graph i cs modes (4 , 6, and 8), the ASCI I code is
reduced modulo 2 to in dicate co l or va lue 0 or 1.
Atari 850 Interface
A PRINT statement for a serial port of an Atari 850 Int erface
module must be preced ed by an appropriate OPEN statement.
Also, the int erface module must be ready to operate. The
interface module will not operate unl ess it was turned on before
the computer console was turned on.

Atari 800 Specifications

General

Processor	MOS Technology 6502
Processor Speed	1.79 MHz
ROM	10 KB
Graphics	ANTIC and GTIA chips
Release Year	1979
Display Resolution	up to 320 x 192
Colors	128 colors
Sound	4 channels
Storage	Cartridge, cassette, floppy disk
Ports	Cartridge, serial, monitor
Operating System	Atari OS