Atari XL User Manual

198 The Afar; XL Handbook
In use, if an error is encounterd, the normal
mechanism whereby program execution is stopped
and an error message displayed is suspended.
Instead, program execution continues at the line
specified by the TRAP command. At this line
number you must include code to handle any
possible errors. You can determine what type of
error has occurred with the statement:
ERR = PEEK(195)
since location 195 contains the code number of the
error (see Appendix 2). The line number at which
the error occurred can be calculated with a
statement like:
LINE = PEEK(186)+256*PEEK(187)
The following program uses the TRAP command
to good effect by using it to display full error
messages rather than error codes which must be
looked up in a table.
1 GOSUB 32000:TRAP 32500
32000
DIM ERROR$(400):DIM
MESSAGE$(20)
32020 RESTORE 32100
32030 FOR ITEM =2 TO 21
32040 MESSAGE$="
":REM 20 SPACES
32050 READ MESSAGE$
32060 ERROR$«ITEM-2)*20+1)=MESSAGE$
32070 NEXT ITEM
32080 RESTORE
32090 RETURN
32100 DATA MEMORY INSUFFICIENT,
ILLEGAL VALUE,TOO MANY
VARIABLES,STRING LENGTH,OUT OF
DATA

Atari XL Specifications

General

Release Year	1983
CPU	MOS Technology 6502C
Graphics	ANTIC, GTIA
Sound	POKEY (4 channels)
Storage	Cassette tape
Ports	Cartridge
Operating System	Atari BASIC
CPU Speed	1.79 MHz
RAM	64 KB