The IEEE standard for floating-point arithmetic defines a number of exception (or error) conditions that might require special care to avoid or recover from. The following topics are intended to help you make your programs work safely in the presence of such exception conditions while sacrificing the minimum amount of performance.
The floating-point hardware always detects a number of floating-point exception conditions (which the IEEE standard rigorously defines): overflow, underflow, zerodivide, invalid, and inexact.
By default, the only action that occurs is that a status flag is set. The program continues without a problem (although the results from that point on may not be what you expect). If you want to know when an exception occurs, you can arrange for one or more of these exception conditions to generate a signal.
The signal causes a branch to a handler routine. The handler receives information about the type of signal and the state of the program when the signal occurred. It can produce a core dump, display a listing showing where the exception occurred, modify the results of the calculation, or carry out some other processing that you specify.
The XL Fortran compiler uses the operating system facilities for working with floating-point exception conditions. These facilities indicate the presence of floating-point exceptions by generating SIGFPE signals.