Date of presentation of proposal:

Stephen Michell
Chair CAC-JTC1-SC22

 Standards Council of Canada

ISO/IEC JTC 1/SC 22 N 3719

A proposal for a new work item shall be submitted to the secretariat of the ISO/IEC joint technical committee concerned with a copy to the ISO Central Secretariat.

Presentation of the proposal - to be completed by the proposer Guidelines for proposing and justifying a new work item are given in ISO Guide 26.



Extensions for the programming language C to support decimal floating-point arithmetic. 


To define extensions to the programming language C, specified by the international standard ISO/IEC 9899:1999. These extensions will provide support for decimal floating-point arithmetic that is consistent with the decimal floating-point specification in IEEE-754R. 

Purpose and justification

The programming language C as specified by the International Standard ISO/IEC 9899:1999 does not require decimal floating-point support. 

Human computation and communication of numeric values almost always uses decimal arithmetic and decimal notations. Laboratory notes, scientific papers, legal documents, business reports and financial statements all record numeric values in decimal form. When numeric data are given to a program or are displayed to a user, binary to-and-from decimal conversion is required. There are inherent rounding errors involved in such conversions; decimal fractions cannot, in general, be represented exactly by binary floating-point values. These errors often cause usability and efficiency problems, depending on the application.

These problems are minor when the application domain accepts, or requires results to have, associated error estimates (as is the case with scientific applications). However, in business and financial applications, computations are either required to be exact (with no rounding errors) unless explicitly rounded, or be supported by detailed analyses that are auditable to be correct. Such applications therefore have to take special care in handling any rounding errors introduced by the computations.

The importance of this has been recognized by the IEEE. The IEEE 754 standard is currently being revised, and the major change in that revision is the addition of decimal floating-point formats and arithmetic. These decimal data types are almost as efficient as the binary types, and are especially suitable for hardware implementation; it is possible that they will become the most widely used primitive data types once hardware implementations are available.

Historically there has been a close relationship between IEEE-754 and the C programming language with respect to floating-point specification. With the revised IEEE-754 nearing the final approval stage, it is now the appropriate time for the ISO C Committee to consider adding decimal types and arithmetic to its specification.

The project also includes the production of the text for a Rationale document (either separate or as part of the project document).

Programme of work

If the proposed new work item is approved, which of the following document(s) is (are) expected to be developed?
____ a single International Standard more than one International Standard (expected number: ........ )
____ a multi-part International Standard consisting of .......... parts
____ an amendment or amendments to the following International Standard(s) ....................................
_X__ a technical report , type 2

Relevant documents to be considered

  • ISO/IEC 9899:1999 - Programming Language C
  • ISO/IEC JTC 1/SC22 WG14 N1016 - Extensions for the programming language C to support decimal floating-point arithmetic.
  • ISO/IEC 11404:1996 - Language-independent datatypes.
  • ANSI/IEEE 754-1985 - IEEE Standard for Binary Floating-Point Arithmetic. The Institute of Electrical and Electronic Engineers, Inc., New York, 1985.
  • ANSI/IEEE  854-1987 - IEEE Standard for Radix-Independent Floating-Point Arithmetic. - The Institute of Electrical and Electronic Engineers, Inc., New York, 1987.
  • ANSI/IEEE 754R - IEEE Standard for Floating-Point Arithmetic. The Institute of Electrical and Electronic Engineers, Inc. Draft.
  • A Decimal Floating-Point Specification, Schwarz, Cowlishaw, Smith, and Webb, in the Proceedings of the 15th IEEE Symposium on Computer Arithmetic (Arith 15), IEEE, June 2001.

Cooperation and liaison

All ISO/IEC JTC 1/SC22 Working groups that have an interest in supporting many natural languages, especially ISO/IEC JTC 1/SC22 WG21 (C++). 

Preparatory work offered with target date(s)

A PDTR document will be ready for registration 24 months after the approval of the project by JTC 1. 


Steven Michell
P-Member of JTC 1/SC 22 

Will the service of a maintenance agency or registration authority be required? .......NO.............
- If yes, have you identified a potential candidate? ................
- If yes, indicate name .............................................................

Are there any known requirements for coding? ..........NO.........
-If yes, please specify on a separate page

Are there any known requirements for cultural and linguistic adaptability? .....NO....
- If yes, please specify on a separate page

Does the proposed standard concern known patented items? .......NO..........
- If yes, please provide full information in an annex

Comments and recommendations of the JTC 1 Secretariat - attach a separate page as an annex, if necessary


Comments with respect to the proposal in general, and recommendations thereon:
It is proposed to assign this new item to JTC 1/SC22 WG14
The proposed project editor is Edison Kwok ( of Canada, a member of good standing of CAC/JTC1/SC22/WG14 of the Standards Council of Canada. The proposed backup project editor is P. J. Plauger ( of the United States, a member of good standing of NCITS J11.

Voting on the proposal - Each P-member of the ISO/IEC joint technical committee has an obligation to vote within the time limits laid down (normally three months after the date of circulation).


Date of circulation:

Closing date for voting:


Signature of JTC 1 Secretary:
Lisa A. Rajchel









A Business Requirement



A.1 Market Requirement

Essential ___
Desirable ___
Supportive ___


A.2 Regulatory Context

Essential ___
Desirable ___
Supportive ___
Not Relevant ___


B. Related Work



B.1 Completion/Maintence of current standards

Yes ___


B.2 Commitment to other organization

Yes ___


B.3 Other Source of standards

Yes ___


C. Technical Status



C.1 Mature Technology

Yes ___


C.2 Prospective Technology

Yes ___


C.3 Models/Tools

Yes ___


D. Conformity Assessment and Interoperability



D.1 Conformity Assessment

Yes ___


D.2 Interoperability

Yes ___


E. Other Justification



Notes to Proforma

A. Business Relevance. That which identifies market place relevance in terms of what problem is being solved and or need being addressed.

A.1. Market Requirement. When submitting a NP, the proposer shall identify the nature of the Market Requirement, assessing the extent to which it is essential, desirable or merely supportive of some other project.

A.2 Technical Regulation. If a Regulatory requirement is deemed to exist - e.g. for an area of public concern e.g. Information Security, Data protection, potentially leading to regulatory/public interest action based on the use of this voluntary international standard - the proposer shall identify this here.

B. Related Work. Aspects of the relationship of this NP to other areas of standardization work shall be identified in this section.

B.1 Competition/Maintenance. If this NP is concerned with completing or maintaining existing standards, those concerned shall be identified here.

B.2 External Commitment. Groups, bodies, or fora external to JTC1 to which a commitment has been made by JTC for cooperation and or collaboration on this NP shall be identified here.

B.3 External Std/Specification. If other activities creating standards or specifications in this topic area are known to exist or be planned, and which might be available to JTC1 as PAS, they shall be identified here.

C. Technical Status. The proposer shall indicate here an assessment of the extent to which the proposed standard is supported by current technology.

C.1 Mature Technology. Indicate here the extent to which the technology is reasonably stable and ripe for standardization.

C.2 Prospective Technology. If the NP is anticipatory in nature based on expected or forecasted need, this shall be indicated here.

C.3 Models/Tools. If the NP relates to the creation of supportive reference models or tools, this shall be indicated here.

D. Any other aspects of background information justifying this NP shall be indicated here.

D. Conformity Assessment and Interoperability

D.1 Indicate here if Conformity Assessment is relevant to your project. If so, indicate how it is addressed in your project plan.

D.2 Indicate here if Interoperability is relevant to your project. If so, indicate how it is addressed in your project plan.