Atari 800 User Manual

152 User's Handbook to the Atari 400/ 800 Computers
At line 50, the display is opened as an I/ O device. The first
argument of the OPEN statement indicates the I/ O channel
number. The second argument indicates that the screen is used
for input and output. Also, a text window is present, and the
screen
is not cleared (Table 5-2). The third argument of the OPEN
statement indicates graphics mode 8.
At line 60, the cursor is positioned at the location of 5,5. The GET
statement at line 70 assigns the color number at the cursor
postion
to the variable X. Since the cursor is at location 5,5, the
color number at that location is 1 (5,5 is one of the points on the
line between 0,0 and 10 , 10) . The PRINT statement at line 80
displays the value of the variable X in the display window.
Atari 850 Interface Module
An OPEN statement for a serial port of an Atari 850 Interface
module requires the device name "R:" . The number of the port
is also necessary for ports 2 through 4. The first argument of the
OPEN statement is the I/ O channel. The second argument
determines the I/ O operation , as listed in Table 5-1. The third
argument is ignored. Although the third argument has no effect,
it must appear in the OPEN statement.
The interface
module must be ready to operate when the OPEN
statement is executed. It will not operate unless it was turned on
before the computer console was turned on . Also, the interface
module may not operate properly until the appropriat e XIO
statements have been executed.
The
following examples are correct OPEN statements for the
interface module.
EXAMPLES
OPEN #1 , 5, 0, "R2:"
OPEN # 2, 13, 0, "R :"
OPEN #4, 8, 0, "R4:"

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