The Art of Assembly Language

4.6 Floating-Point Exceptions

The IEEE floating-point standard defines certain degenerate conditions under which the floating-point processor (or software-implemented floating-point code) should possibly notify the application software. These exceptional conditions include the following:

• Invalid operation

• Division by zero

• Denormalized operand

• Numeric overflow

• Numeric underflow

• Inexact result

Of these, inexact result is the least serious, because most floating calculations will produce an inexact result. A denormalized operand also isn't too serious (though this exception indicates that your calculation may be less accurate as a result of less available precision). The other exceptions indicate a more serious problem, and you shouldn't ignore them.

How the computer system notifies your application of these exceptions depends on the CPU/FPU, operating system, and programming language, so we can't really go into how one might handle these exceptions. Generally, though, you can use the exception-handling facilities in your programming language to trap these conditions as they occur in your particular environment. Note that most computer systems require that you explicitly tell them to generate a notification for these exceptional conditions; otherwise , the system will not notify you when one of the exceptional conditions exist.