User`s manual

4-14
The ON ERROR GOTO statement can be disabled by executing an ON
ERROR GOTO 0. If you use this inside an error-trapping routine, BASIC will
handle the current error normally.
The error handling routine must be terminated by a RESUME statement.
See
RESUME.
RESUME
line number
Terminates an error handling routine by specifying where normal execution
is to resume.
RESUME without a line number and RESUME 0 cause the Computer to
return to the statement in which the error occurred.
RESUME followed by a line number causes the Computer to branch to the
specified line number.
RESUME NEXT causes the Computer to branch to the statement following
the point at which the error occurred.
Sample Program with an Error Handling Routine
5 ON ERROR GOTO 100
10 INPUT"SEEKING SQUARE ROOT OF";X
20 PRINT SQR(X)
30 GOTO 10
100 PRINT "IMAGINARY ROOT:";SQR(-X);"*I"
110 RESUME 10
RUN the program and try inputting a negative value.
You must place a RESUME statement at the end of your error trapping
routine, so that later errors may also be trapped.