Atari 800 User Manual

182 User's Handbook to the Atari 400/ 800 Computers
100 TRAP 700
200 INPUT A
EXAMPLE
300 IF A = 0 THEN 999
400 PRINT A
500 GOTO 200
700 PRINT PEEK (195)
800 PRINT 256 * PEEK (187) + PEEK (186)
999 END
RUN
?A
8
200
READY
In
the preceding example, the TRAP statement in line 100 will
cause the program to branch to line 700 if an error is
encountered . In line 700, the error code is displayed. (Address
195 is used to store the error code.). In line 800 , the line number
where the error occurred is displayed. The following expression,
256 * PEEK(187) + PEEK(186)
returns the line number where the error occurred.
In our example, the data input in r es ponse to the INPUT
statement in line 200 was string. Since a numeric variable was
specified in line 200, error code 8 was generated. This was
displayed along with the line number where the error occurred
(200).
USR
USR is used to branch program control to a machine language
program.
CONFIGURATION
USR(address[, argument ... J)

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