scope:

(This Foreword is not a part of ANSI/IEEE Std 854-1987, IEEE Standard for Radix-Independent Floating-Point Arithmetic.)

This standard is a product of the Radix-Independent Floating-point Arithmetic Working Group of the Microprocessor Standards Subcommittee. This work was sponsored by the Technical Committee on Microprocessors and Minicomputers of the IEEE Computer Society. It generalizes ANSI/IEEE Std 754-1985, IEEE Standard for Binary Floating-Point Arithmetic, to remove dependencies on radix and wordlength. The committee believes that, except for a possible conflict with the requirements in 5.6 and 7.2 that unrecognizable decimal input strings signal an exception, and in 6.3 that the sign of zero be preserved in certain conversion operations, any implementation conforming to ANSI/IEEE Std 754-1985, will also conform to this standard. In addition, the definition of logb has been enhanced in the Appendix, and two new functions, conv and nearbyinteger, have been added. Draft 1.0 of this standard was published to solicit public comments.¹

This standard defines a family of commercially feasible ways for new systems to perform floating-point arithmetic. Issues of retrofitting were not considered. Among the desiderata that guided the formulation of this standard were the following:

(1) Facilitate movement of existing programs from diverse computers to those that adhere to this standard.

(2) Enhance the capabilities and safety available to programmers who, though not expert in numerical methods, may well be attempting to produce numerically sophisticated programs. However, we recognize that utility and safety are sometimes antagonists.

(3) Encourage experts to develop and distribute robust and efficient numerical programs that are portable, via minor editing and recompilation, onto any computer that conforms to this standard and possesses adequate capacity.

(4) Provide direct support for

(a) execution-time diagnosis of anomalies,

(b) smoother handling of exceptions, and

(c) interval arithmetic at a reasonable cost.

(a) standard elementary functions like exp and cos,

(b) very high precision (multiword) arithmetic, and

(c) coupling of numerical and symbolic algebraic computation.

(5) Provide for development of

(6) Enable rather than preclude further refinements and extensions.

1.1 Implementation Objectives.

It is intended that an implementation of a floating-point system conforming to this standard can be realized entirely in software, entirely in hardware, or in any combination of software and hardware. It is the environment the programmer or user of the system sees that conforms or fails to conform to this standard. Hardware components that require software support to conform shall not be said to conform apart from such software.