Programming 620
Debugging Techniques
Run-time error messages can locate syntax errors but not errors in program logic. The
following techniques may be useful.
• During testing, do not use local variables so that you can check the variable values
after the program stops. When the program is debugged, declare the applicable
variables as local.
• Within a program, temporarily insert
Disp and Pause commands to display the
values of critical variables.
-
Disp and Pause cannot be used in a user-defined function. To temporarily
change the function into a program, change
Func and EndFunc to Prgm and
EndPrgm. Use Disp and Pause to debug the program. Then remove Disp and
Pause and change the program back into a function.
• To confirm that a loop is executed the correct number of times, display the counter
variable or the values in the conditional test.
• To confirm that a subroutine is executed, display messages such as
Entering
subroutine
and Exiting subroutine at the beginning and end of the subroutine.
Error-Handling Commands
Command Description
Try...EndTry Defines a program block that lets the program execute a
command and, if necessary, recover from an error
generated by that command.
ClrErr Clears the error status and sets the error number in system
variable Errornum to zero.
PassErr Passes an error to the next level of the Try...EndTry block.
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