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Debugging Programs and Handling Errors
After you write a function or program, you can use several techniques to find
and correct errors. You can also build an error-handling command into the
function or program itself.
If your function or program allows the user to select from several options, be
sure to run it and test each option.
Techniques for Debugging
Run-time error messages can locate syntax errors but not errors in program
logic. The following techniques may be useful.
• Temporarily insert Disp commands to display the values of critical
variables.
• To confirm that a loop is executed the correct number of times, use Disp to
display the counter variable or the values in the conditional test.
• To confirm that a subroutine is executed, use Disp to display messages
such as “Entering subroutine” and “Exiting subroutine” at the beginning
and end of the subroutine.
• To stop a program or function manually,
- Windows®: Hold down the F12 key and press Enter repeatedly.
- Mac®: Hold down the F5 key and press Enter repeatedly.
- Handheld: Hold down the c key and press · repeatedly.
Error-handling Commands
Command Description
Try...EndTry
Defines a block that lets a function or program execute a
command and, if necessary, recover from an error generated
by that command.
ClrErr
Clears the error status and sets system variable errCode to
zero. For an example of using errCode, see the Try
command in the Reference Guide .
PassErr
Passes an error to the next level of the Try...EndTry block.
Getting Started with the Program Editor 509