Texas Instruments TITANIUM TI-89 User Manual

Page 636

Programming

636

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

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.