Atari 400 Basic Reference Manual

TRAP (T.)
22 Program Stateme nt s
and B, because of the RESTORE statement, will still equal 30. Therefore, the
PRINT statement in line 50 will display SUM TOTAL EQUALS 45.
Format:
Example:
TRAP aexp
100 TRAP 120
The TRAP statement is used to direct the program to a specified line number if
an error is detected . Without a TRAP statement, the program stops executing
when an error is encountered and displays an error message on the screen.
The TRAP statement works on any error that may occur after it has been ex-
ecuted, but once an error has been detected and trapped, it is necessary to reset
the trap with another TRAP command. This TRAP command may be placed at
the beginning of the section of code that handles input from the keyboard so
that the TRAP is reset after each error. PEEK(195) will give you an error
message (see Appendix B). 256 *PEEK(187)+ PEEK(186) will give you the number
of the line where the error occurred. The TRAP may be cleared by executing a
TRAP statement with an aexp whose value is from 32767 to 65535 (e.g., 40000).

Atari 400 Specifications

General

Manufacturer	Atari
Model	400
Type	Home Computer
Release Year	1979
CPU	MOS Technology 6502
CPU Speed	1.79 MHz
ROM	10 KB
Operating System	Atari OS
Keyboard	Membrane keyboard
RAM	8 KB (expandable to 48 KB)
Graphics	ANTIC and GTIA chips
Sound	4 channels
Display	RF output for connection to TV
Storage	Optional cassette tape drive or floppy disk drive
Ports	Cartridge
Display Resolution	320x192 (16 colors)