Exceptions handled by the ON statement

Like the +fp_exception option, the ON statement enables traps for floating-point exceptions (by default, traps for floating-point exceptions are disabled on HP 9000 computers). When traps are enabled, an executing program that takes any of the following exceptions will abort, unless an ON statement specifies a different action:

These exceptions are defined by the IEEE standard for floating-point operations. The ON statement enables traps for these exceptions, regardless of whether the exception is taken by user code or by a call to a library routine. In addition, the ON statement also enables traps for integer division by zero, integer overflow, and +Ctrl-C interrupts. The +Ctrl-C interrupt occurs when the user presses +Ctrl-C during program execution.

The table below lists the exceptions handled by the ON statement and gives the keywords that must be specified in the ON statement to indicate the exception being handled. The first column indicates the type of exception. The second column gives the keywords that must appear in the ON statement, immediately following the word ON. The third column gives alternate keywords you can specify instead of those in the second column.

For example, the following ON statement will trap attempts to divide by zero with 8-byte floating-point operands:

ON REAL(8) DIV 0 CALL div_zero_trap

The next example ON statement does the same as the first but uses the alternate keywords from the third column of the table:

ON DOUBLE PRECISION DIV 0 CALL div_zero_trap