Atari 800 User Manual

184 User's Handbook to the Atari 400/ 800 Computers
Illustration 5-2. USR Hardware Stack
Top of Stack
Bottom of Stack
XIO
USR Argument Count
First USR Argument
Second USR Argument
Final USR Argument
BASIC Program's
Return Address
Stack Contents Prior
to USR
EXAMPLE
050 DIM A$(50)
100
A$ = "57 A72B"
200 PRINT VAL(A$)
300 PRINT VAL(A$) + 2
RUN
57
59
The XIO statement is a generalized in put/output statement
which can perform a wide range of input and output operations.
These operations are summarized in Table 5-4.

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