Intel 9800758-02 Error Simulation , Restarting Program Execution

Error Handling
4-4
Error Simulation
BASIC-SO provides a statement that can simulate any errors which produce an error
code. When the
ERROR statement is encountered during program execution,
BASIC-SO acts as if the specified error had occurred. The example below
demonstrates how
ERROR can be used to test an error handling routine.
10 ON ERROR GOTO 70
20 INPUT A
30 B = A * .3842
40 PRINT B
50 GOTO 20
70 IF 11 = ERR THEN PRINT "Division by zero"
80 RESUME NEXT
If line 40 is replaced with:
40 ERROR 11
Program control transfers to line 70 regardless of the result of the operation in line
30.
Restarting Program Execution
You can restart program execution after it has halted with the RUN or CONT
instruction, and after an error in an ON ERROR routine with the RESUME
instruction. Remember that RUN sets all variables to zero.
RUN restarts program execution at the lowest-numbered line of a program if no line
number
is specified, or at the specified line number. It can be used at any time.
CONT restarts execution at the line after a STOP, END, or CONTROL-C is en-
countered. CONT will also restart program execution after
an error, but it will try to
execute the erroneous line.
RESUME can only be used when the halt occurs in an ON ERROR routine. It is
given following the error-resolving routine pointed to by the ON ERROR instruc-
tion.
It can be used three ways: RESUME to begin execution at the erroneous line;
RESUME NEXT to begin execution at the line following the erroneous line;
RESUME followed by a line number to begin execution at any other line.
BASIC-SO