Decimal Encoding Specification, version 1.01
Copyright (c) IBM Corporation, 2009. All rights reserved. ©
7 Apr 2009
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This document describes decimal encodings suitable for supporting the general purpose floating-point decimal arithmetic defined in the Decimal Arithmetic Specification,[1]  which allows fixed-point and integer decimal arithmetic as subsets.

The encodings are the product of discussions by a subcommittee of the IEEE committee (known as 754R) which revised the IEEE 754-1985[2]  and IEE 854-1987[3]  standards. These encodings are now included in the new IEEE-SA 754 standard approved in June 2008.

The primary audiences for this document are implementers and standards-makers, so examples and explanatory material are included. This informative material is identified as Notes, Examples, or footnotes, and is not part of the formal specification.

Additional rationale and explanatory material can be found in the paper A Decimal Floating-Point Specification.[4]  For further background details, please see the material at the associated web site:

Comments on this document are welcome. Please send any comments, suggestions, and corrections to the author, Mike Cowlishaw (


The author is indebted to David Bindel, Glenn Colon-Bonet, James Demmel, William Kahan, Dave Raggett, Andy Rawson, Jason Riedy, Fred Ris, Eric Schwarz, Ronald Smith, Charles Webb, and Dan Zuras, who have all directly contributed to this document.

Also, of course, thanks are due to all the contributors to standards work in the area – especially the members of the Radix-Independent Floating-Point Arithmetic Working Group of the Microprocessor Standards Subcommittee of the IEEE, the members of the X3 Secretariat/CBEMA (now NCITS) Subcommittee J18, and the members of the IEEE 754r committee.

[1] See
[2] ANSI/IEEE 754-1985 – IEEE Standard for Binary Floating-Point Arithmetic, The Institute of Electrical and Electronics Engineers, Inc., New York, 1985.
[3] IEEE 854-1987 – IEEE Standard for Radix-Independent Floating-Point Arithmetic, The Institute of Electrical and Electronics Engineers, Inc., New York, 1987.
[4] A Decimal Floating-Point Specification, Schwarz, Cowlishaw, Smith, and Webb, in the Proceedings of the 15th IEEE Symposium on Computer Arithmetic (Arith15), IEEE, June 2001.

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