Chapter 5 Using the ON statement

Whenever a runtime error occurs, the default action of your program depends on the type of the error. If the error results from a floating-point exception, the program will continue to execute. Other errors will cause it to abort.

As described in “Handling runtime exceptions”, the +fp_exception and +FP options provide control over how a program behaves when a runtime error occurs. The ON statement provides an additional level of control by enabling your program to handle floating-point and integer exceptions and +Ctrl-C interrupts. Before an exception can be handled, the flow of control must pass through an ON statement that specifies:

The action specified by the ON statement can only be changed by another ON statement that specifies the same exception.

This chapter describes how to use the ON statement. The syntax of the ON statement is described in the HP Fortran 90 Programmer's Reference. For detailed information about trapping math errors, see the HP-UX Floating-Point Guide.

	NOTE: If you include the ON statement in a program that you optimize at level 2 or higher and the program takes an exception, the results may vary from those you would get from an unoptimized program or from a program that didn't have the ON statement.