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1、IEEE Std 1541-2002 IEEE Standards 1541 TM IEEE Trial-Use Standard for Prefixes for Binary Multiples Published by The Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue, New York, NY 10016-5997, USA 12 February 2003 IEEE Standards Coordinating Committee 14 Sponsored by the IEEE Sta
2、ndards Coordinating Committee 14 on Quantities, Units, and Letter Symbols IEEE Standards Print: SH95036 PDF: SS95036 Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007
3、08:36:02 MDTNo reproduction or networking permitted without license from IHS -,-,- The Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue, New York, NY 10016-5997, USA Copyright 2003 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Published 12 F
4、ebruary 2003. Printed in the United States of America. IEEE is a registered trademark in the U.S. Patent +1 978 750 8400. Permission to photocopy portions of any individual standard for educational classroom use can also be obtained through the Copyright Clearance Center. Note: Attention is called t
5、o the possibility that implementation of this standard may require use of subject matter covered by patent rights. By publication of this standard, no position is taken with respect to the existence or validity of any patent rights in connection therewith. The IEEE shall not be responsible for ident
6、ifying patents for which a license may be required by an IEEE standard or for conducting inquiries into the legal validity or scope of those patents that are brought to its attention. Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicense
7、e=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 08:36:02 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright 2003 IEEE. All rights reserved. iii Introduction (This introduction is not part of IEEE Std 1541-2002, IEEE Trial-Use Standard for Prefi xes
8、 for Binary Multiples.) Modern computers use binary logic for computation and addressing, and binary logic inevitably leads to addresses expressed in binary arithmetic. The size of such an address space is inevitably a power of two. Thus, when computer memories and disks were tiny (in terms of capac
9、ity), it became common practice to use “kilo” as a prefi x denoting multiplication by 1024 (= 2 10 ). In the 1960s and 1970s this created no problem because there is not much difference between 1000 and 1024, and within the community of persons who used computers, everybody understood what was meant
10、. Thus decimal prefi xes came to be applied on the grounds that it would have been senseless, in the computer fi eld, to interpret them as anything other than binary multiples, i.e., it would have seemed illogical to size a small memory in multiples of 1000 when the size of the address space was 102
11、4. As the capacity of memories and disks has grown larger, the issue of correspondence with the size of the address space became less important than the issue of total capacity requirements. In addition, the disparity between binary and decimal multiples is larger with the larger prefi xes. Data sto
12、rage specialists now work with terabytes. If one purchases a terabyte of storage, can one store 10 12 bytes or 2 40 bytes? The difference is roughly 10%. Personal computers have become ubiquitous in the twenty-fi rst century, and the use of decimal prefi xes where binary multiplication is intended c
13、auses real confusion. Most computer users today are not specialists. They know that a kilometer is 1000 meters and, having no familiarity with powers of 2, assume that a kilobyte is 1000 bytes. The result is confusion and occasional misunderstanding. This IEEE standard defi nes new prefi xes for bin
14、ary multiples and thereby makes precise and unambiguous communication possible. A similar standard, IEC 60027-2 B1, has already been adopted by the International Electrotechnical Commission. The working group that prepared this standard had the following membership: James R. Frysinger, Chair The fol
15、lowing members of the balloting committee voted on this standard. Balloters may have voted for approval, disapproval, or abstention. Publication of this trial-use standard for comment and criticism has been approved by the Institute of Electrical and Electronics Engineers. Trial-use standards are ef
16、fective for 24 months from the date of publication. Comments for revision will be accepted for 18 months after publication. Suggestions for revision should be directed to the Secretary, IEEE-SA Standards Board, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331, and should be received no later
17、than 10 December 2004. It is expected that following the 24-month period, this trial-use standard, revised as necessary, shall be submitted to the IEEE-SA Standards Board for approval as a full-use standard. Gordon J. Aubrecht Bruce B. Barrow Stanley L. Ehrlich David Goldman (deceased) Stan Jakuba J
18、oseph Langenstein James W. Moore John Scott Ralph M. Showers Barry N. Taylor Lorelle M. Young Allan Zuckerwar William W. Aird O. C. Amrhyn Gordon J. Aubrecht Bruce B. Barrow Norman B. Belecki Stanley L. Ehrlich James R. Frysinger Ronald B. Goldfarb Dee S. Long Jack M. Loudon James McCracken James W.
19、 Moore Ralph M. Showers Barry N. Taylor Theodore Wildi Lorelle M. Young Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 08:36:02 MDTNo reproduction or networking per
20、mitted without license from IHS -,-,- iv Copyright 2003 IEEE. All rights reserved. When the IEEE-SA Standards Board approved this standard on 11 December 2002, it had the following membership: James T. Carlo, Chair James H. Gurney, Vice Chair Judith Gorman, Secretary *Member Emeritus Also included a
21、re the following nonvoting IEEE-SA Standards Board liaisons: Alan Cookson, NIST Representative Satish K. Aggarwal, NRC Representative Noelle D. Humenick IEEE Standards Project Editor Sid Bennett H. Stephen Berger Clyde R. Camp Richard DeBlasio Harold E. Epstein Julian Forster* Howard M. Frazier Tosh
22、io Fukuda Arnold M. Greenspan Raymond Hapeman Donald M. Heirman Richard H. Hulett Lowell G. Johnson Joseph L. Koepfi nger* Peter H. Lips Nader Mehravari Daleep C. Mohla William J. Moylan Malcolm V. Thaden Geoffrey O. Thompson Howard L. Wolfman Don Wright Copyright The Institute of Electrical and Ele
23、ctronics Engineers, Inc. Provided by IHS under license with IEEELicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 08:36:02 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright 2003 IEEE. All rights reserved. v Contents 1.Overview 1 1.1 Scope 1 1
24、.2 Purpose. 1 2.Definitions 1 3.Prefixes for binary multiples 2 4.Principles of usage. 2 4.1 The SI prefixes. 2 4.2 Application of the prefixes for binary multiples 2 Annex A (informative) Bibliography. 4 Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under lic
25、ense with IEEELicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 08:36:02 MDTNo reproduction or networking permitted without license from IHS -,-,- vi Copyright 2003 IEEE. All rights reserved. Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IH
26、S under license with IEEELicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 08:36:02 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright 2003 IEEE. All rights reserved. 1 IEEE Trial-Use Standard for Prefi xes for Binary Multiples 1. Overview Thi
27、s standard is divided into four clauses. Clause 1 states the scope and purpose of the standard. Clause 2 quotes relevant standard defi nitions. Clause 3 defi nes the prefi xes for binary multiples. Clause 4 provides principles for the application of these prefi xes. 1.1 Scope This standard defi nes
28、names and letter symbols for prefi xes that denote multiplication of a unit by the binary multiplier 2 10 n , where n = 1, 2, 3, 4, 5, or 6. Although the prefi xes may be used with all units in all fi elds where multiplication by a binary multiplier is found to be appropriate, their primary use is i
29、n the fi eld of information technology. The prefi xes given here have also been adopted by the International Electrotechnical Commission, IEC 60027-2 B1. 1 1.2 Purpose In recent years confusion has resulted from the fact that the SI prefi xeskilo, mega, giga, etc.have been used sometimes with their
30、correct meaning as decimal multipliers and sometimes with a special meaning as binary multipliers. The purpose of this standard is to establish prefi xes for binary multiples in order to make precise and unambiguous communication possible, especially within the fi elds of data processing and informa
31、tion systems. 2. Defi nitions For the purposes of this standard, the following terms and defi nitions, taken from reference IEEE 100 B2, apply. IEEE 100 should be referenced for terms not defi ned in this clause. 2.1 byte (B): A group of adjacent binary digits operated on as a unit; usually eight bi
32、ts. 2.2 octet (o): A byte composed of eight bits. 1 The numbers in brackets correspond to those of the bibliography in Annex A. Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=NASA Technical Standards 1/9972545001 Not for Resale,
33、04/20/2007 08:36:02 MDTNo reproduction or networking permitted without license from IHS -,-,- IEEE Std 1541-2002IEEE TRIAL-USE STANDARD FOR 2 Copyright 2003 IEEE. All rights reserved. 3. Prefi xes for binary multiples The prefi xes given in Table 1 shall be used to indicate multiplication by 2 10 n
34、, where n = 1, 2, 3, 4, 5, or 6. 4. Principles of usage 4.1 The SI prefi xes The SI prefi xes shall not be used to denote multiplication by powers of two. 4.2 Application of the prefi xes for binary multiples This standard is prepared with two goals in mind: (1) to preserve the SI prefi xes as unamb
35、iguous decimal multipliers and (2) to provide alternative prefi xes for those cases where binary multipliers are needed. The fi rst goal affects the general public, the wide audience of technical and nontechnical persons who use computers without much concern for their construction or inner working.
36、 These persons will normally interpret kilo, mega, etc., in their proper decimal sense. The second goal speaks to specialiststhe prefi xes for binary multiples make it possible for persons who work in the information sciences to communicate with precision. The following two examples illustrate some
37、of the current confusion. Example 1: The common 90 mm diskette, as formatted for PC use, is usually advertised as containing 1.44 megabytes. 2 It is actually formatted for 1440 kibibytes, and the “mega” in this application is neither a proper SI prefi x nor a binary prefi x. The resulting hybrid “me
38、gabyte” is equal to 10 3 2 10 bytes. Example 2: The following “frequently asked question” appears in an instruction manual widely distributed in 1999: Q: The formatted capacity of my hard drive seems smaller than what was ordered. Why? A: Your operating system assumes that 1 MB equals 1 048 576 byte
39、s. Drive manufacturers consider 1 MB as equal to 1 000 000 bytes. Thus, if the drive is advertised as 6.4 gigabytes (6 400 000 000 bytes), the operating system sees it as approximately 6.1 GB (6 400 000 000)/(1 048 576 000) = 6.1035. Note that in this example, the PC vendor creates a hybrid “gigabyt
40、e” that is equal to 10 3 2 20 bytes. Table 1Prefi xes FactorNameSymbolOrigin Related SI prefi xesExamples 2 10 kibiKikilobinary: (2 10 )kilo: (10 3 ) kKib = 1.024 kb 2 20 mebiMimegabinary: (2 10 ) 2 mega: (10 3 ) 2 MMiB 1.0486 MB 2 30 gibiGigigabinary: (2 10 ) 3 giga: (10 3 ) 3 GGio 1.0737 Go 2 40 t
41、ebiTiterabinary: (2 10 ) 4 tera: (10 3 ) 4 TTib 1.0995 Tb 2 50 pebiPipetabinary: (2 10 ) 5 peta: (10 3 ) 5 PPiB 1.1259 PB 2 60 exbiEiexabinary: (2 10 ) 6 exa: (10 3 ) 6 EEio 1.1529 Eo 2 The 90 mm diskette has been known by its trade size 3.5 in. Copyright The Institute of Electrical and Electronics
42、Engineers, Inc. Provided by IHS under license with IEEELicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 08:36:02 MDTNo reproduction or networking permitted without license from IHS -,-,- IEEE PREFIXES FOR BINARY MULTIPLESStd 1541-2002 Copyright 2003 IEEE. All rights reserved
43、. 3 The fi rst example represents more of a curiosity than a real problem, for the difference between the advertised “1.44 MB” and the more accurate 1.47 MB is of little practical importance. The second example, however, calls attention to an area where there has been real misunderstanding between b
44、uyers and sellers of hard drives. The difference between a gigabyte and a gibibyte is approximately 7.5%. Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 08:36:02 MD
45、TNo reproduction or networking permitted without license from IHS -,-,- IEEE PREFIXES FOR BINARY MULTIPLESStd 1541-2002 Copyright 2003 IEEE. All rights reserved. 4 Annex A (informative) Bibliography B1 IEC 60027-2, Letter symbols to be used in electrical technology, Part 2: Telecommunications and el
46、ec- tronics, Amendment 2, 1999-01. B2 IEEE 100, The Authoritative Dictionary of IEEE Standards Terms, Seventh Edition, New York, Institute of Electrical and Electronics Engineers, Inc. 3 B3 IEEE Std 260.1 -2002, American National Standard Letter Symbols for Units of Measurement (SI Units, Customary
47、Inch-Pound Units, and Certain Other Units). B4 IEEE/ASTM SI 10 -2002, American National Standard for Use of the International System of Units (SI): The Modern Metric System. 3 The IEEE standards or products referred to in Annex A are trademarks owned by the Institute of Electrical and Electronics Engineers, Incorporated. Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 08:36:02 MDTNo reproduction or networking permitted without license from IHS -,-,-