HP-UX Floating-Point Guide

Chapter 2 35
Floating-Point Principles and the IEEE Standard for Binary Floating-Point Arithmetic
What Is the IEEE Standard?
What Is the IEEE Standard?
The IEEE standard was approved in 1985. Its main purpose is to define
specifications for representing and manipulating floating-point values so
that programs written on one IEEE-conforming machine can be moved to
another conforming machine with predictable results. In addition, the
standard is specifically designed to make it easier for programmers to
write useful and robust floating-point programs. The standard defines
the following:
• Formats for representing floating-point numbers
• Representations of special values (for example, infinity, very small
values, and non-numbers)
• Five types of exception conditions, when they occur, and what
happens when they do occur
• Four rounding modes (different algorithms for rounding values)
• A minimum set of operations that can be performed on floating-point
values, precisely defined so that they yield the same results for the
same operands on any standard-conforming system
All HP 9000 systems comply with the IEEE standard. A complete
understanding of the IEEE standard and your system’s implementation
of the standard is helpful for writing robust floating-point programs.