ON ERROR

Function

ON ERROR is used to catch errors which would normally give a Basic Error message.

Syntax

ON ERROR GOTO [line no]

ON ERROR GOTO 0

Examples

10 ON ERROR GOTO 1000
20 INPUT A
30 A = SQR(A)
40 PRINT A
50 GOTO 20
1000 A=ABS(A)
1010 PRINT "NEGATIVE NUMBER CORRECTED"
1020 RESUME 30

This example will trap negative numbers and correct the condition.

Remarks

ON ERROR causes program execution to be diverted to an error handling subroutine.

Any error can be trapped. However, ON ERROR is normally used for correctable errors, e.g. magnitude errors, which could be caused by operator input etc.

An ON ERROR trap must be exited by either an RESUME statement or by ON ERROR GOTO 0 which will give the normal Basic error message.