IEEE 1541-2002 en Trial-Use Standard for Prefixes for Binary Multiples《二进制复接用前缀的查验标准》.pdf

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17、2323#2323#2323#2323#2323#2323#2323#2323#2323g55g48;#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323;#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323;#2323#2323#2323#2323#2323#2

18、323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323;#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323The Institute of Electrical and Electronics Engineers, Inc.Three Park Avenue, New York, NY 10016-5997, USACopyr

19、ight 2009 by the Institute of Electrical and Electronics Engineers, Inc.All rights reserved. Published 18 September 2009. 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 educati

20、onal classroom use can also be obtained through the Copyright Clearance Center. Copyright 2009 IEEE. All rights reserved. iiiIntroduction(This introduction is not part of IEEE Std 1541-2002, IEEE Standard for Prefixes for Binary Multiples.)Modern computers use binary logic for computation and addres

21、sing, and binary logic inevitably leads toaddresses 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 capacity), it became common practice touse “kilo” as a prefix denoting multiplication by 10

22、24 (= 210). In the 1960s and 1970s this created noproblem because there is not much difference between 1000 and 1024, and within the community of personswho used computers, everybody understood what was meant. Thus decimal prefixes came to be applied onthe grounds that it would have been senseless,

23、in the computer field, to interpret them as anything other thanbinary multiples, i.e., it would have seemed illogical to size a small memory in multiples of 1000 when thesize of the address space was 1024. As the capacity of memories and disks has grown larger, the issue ofcorrespondence with the si

24、ze of the address space became less important than the issue of total capacityrequirements. In addition, the disparity between binary and decimal multiples is larger with the largerprefixes. Data storage specialists now work with terabytes. If one purchases a terabyte of storage, can onestore 1012by

25、tes or 240bytes? The difference is roughly 10%.Personal computers have become ubiquitous in the twenty-first century, and the use of decimal prefixeswhere binary multiplication is intended causes real confusion. Most computer users today are not specialists.They know that a kilometer is 1000 meters

26、and, having no familiarity with powers of 2, assume that akilobyte is 1000 bytes. The result is confusion and occasional misunderstanding. This IEEE standard definesnew prefixes for binary multiples and thereby makes precise and unambiguous communication possible. Asimilar standard, IEC 60027-2 B1,

27、has already been adopted by the International ElectrotechnicalCommission.The working group that prepared this standard had the following membership:James R. Frysinger, ChairThe following members of the balloting committee voted on this standard. Balloters may have voted forapproval, disapproval, or

28、abstention. Gordon J. AubrechtBruce B. BarrowStanley L. EhrlichDavid Goldman (deceased)Stan JakubaJoseph LangensteinJames W. MooreJohn ScottRalph M. Showers Barry N. TaylorLorelle M. YoungAllan ZuckerwarWilliam W. AirdO. C. AmrhynGordon J. AubrechtBruce B. BarrowNorman B. BeleckiStanley L. EhrlichJa

29、mes R. FrysingerRonald B. GoldfarbDee S. LongJack M. LoudonJames McCrackenJames W. MooreRalph M. ShowersBarry N. TaylorTheodore WildiLorelle M. Youngiv Copyright 2009 IEEE. All rights reserved.When the IEEE-SA Standards Board approved this standard on 11 December 2002, it had the followingmembership

30、:James T. Carlo, ChairJames H. Gurney, Vice ChairJudith Gorman, Secretary*Member EmeritusAlso included are the following nonvoting IEEE-SA Standards Board liaisons:Alan Cookson, NIST RepresentativeSatish K. Aggarwal, NRC RepresentativeNoelle D. HumenickIEEE Standards Project EditorSid BennettH. Step

31、hen BergerClyde R. CampRichard DeBlasioHarold E. EpsteinJulian Forster*Howard M. FrazierToshio FukudaArnold M. GreenspanRaymond HapemanDonald M. HeirmanRichard H. HulettLowell G. JohnsonJoseph L. Koepfinger*Peter H. LipsNader MehravariDaleep C. MohlaWilliam J. MoylanMalcolm V. ThadenGeoffrey O. Thom

32、psonHoward L. WolfmanDon WrightCopyright 2009 IEEE. All rights reserved.vContents1. Overview 11.1 Scope 11.2 Purpose. 12. Definitions 13. Prefixes for binary multiples 24. Principles of usage . 24.1 The SI prefixes. 24.2 Application of the prefixes for binary multiples 2Annex A (informative) Bibliog

33、raphy. 4viCopyright 2009 IEEE. All rights reserved.Copyright 2009 IEEE. All rights reserved.1IEEE StandardforPrefixes for Binary Multiples1. OverviewThis standard is divided into four clauses. Clause 1 states the scope and purpose of the standard. Clause 2quotes relevant standard definitions. Clause

34、 3 defines the prefixes for binary multiples. Clause 4 providesprinciples for the application of these prefixes.1.1 ScopeThis standard defines names and letter symbols for prefixes that denote multiplication of a unit by the binarymultiplier 210n, where n= 1, 2, 3, 4, 5, or 6. Although the prefixes

35、may be used with all units in all fieldswhere multiplication by a binary multiplier is found to be appropriate, their primary use is in the field ofinformation technology. The prefixes given here have also been adopted by the InternationalElectrotechnical Commission, IEC 60027-2 B1.11.2 PurposeIn re

36、cent years confusion has resulted from the fact that the SI prefixeskilo, mega, giga, etc.have beenused sometimes with their correct meaning as decimal multipliers and sometimes with a special meaning asbinary multipliers. The purpose of this standard is to establish prefixes for binary multiples in

37、 order to makeprecise and unambiguous communication possible, especially within the fields of data processing andinformation systems.2. DefinitionsFor the purposes of this standard, the following terms and definitions, taken from reference IEEE 100 B2,apply. IEEE 100 should be referenced for terms n

38、ot defined in this clause.2.1 byte (B):A group of adjacent binary digits operated on as a unit; usually eight bits.2.2 octet (o):A byte composed of eight bits.1The numbers in brackets correspond to those of the bibliography in Annex A.IEEEStd 1541-2002 IEEE STANDARD FOR 2Copyright 2009 IEEE. All rig

39、hts reserved.3. Prefixes for binary multiplesThe prefixes given in Table 1 shall be used to indicate multiplication by 210n, where n= 1, 2, 3, 4, 5, or 6. 4. Principles of usage4.1 The SI prefixesThe SI prefixes shall not be used to denote multiplication by powers of two.4.2 Application of the prefi

40、xes for binary multiplesThis standard is prepared with two goals in mind: (1) to preserve the SI prefixes as unambiguous decimalmultipliers and (2) to provide alternative prefixes for those cases where binary multipliers are needed. Thefirst goal affects the general public, the wide audience of tech

41、nical and nontechnical persons who usecomputers without much concern for their construction or inner working. These persons will normallyinterpret kilo, mega, etc., in their proper decimal sense. The second goal speaks to specialiststhe prefixesfor binary multiples make it possible for persons who w

42、ork in the information sciences to communicate withprecision. The following two examples illustrate some of the current confusion.Example 1:The common 90 mm diskette, as formatted for PC use, is usually advertised as containing 1.44megabytes.2It is actually formatted for 1440 kibibytes, and the “meg

43、a” in this application is neither a properSI prefix nor a binary prefix. The resulting hybrid “megabyte” is equal to 103210bytes.Example 2:The following “frequently asked question” appears in an instruction manual widely distributedin 1999:Q:The formatted capacity of my hard drive seems smaller than

44、 what was ordered. Why?A: Your operating system assumes that 1 MB equals 1 048 576 bytes. Drive manufacturers consider 1 MB asequal to 1 000 000 bytes. Thus, if the drive is advertised as 6.4 gigabytes (6 400 000 000 bytes), theoperating system sees it as approximately 6.1 GB (6 400 000 000)/(1 048

45、576 000) = 6.1035.Note that in this example, the PC vendor creates a hybrid “gigabyte” that is equal to 103220bytes.Table 1PrefixesFactor Name Symbol Origin Related SI prefixes Examples210kibi Ki kilobinary: (210) kilo: (103) k Kib = 1.024 kb220mebi Mi megabinary: (210)2mega: (103)2M MiB 1.0486 MB23

46、0gibi Gi gigabinary: (210)3giga: (103)3G Gio1.0737 Go240tebi Ti terabinary: (210)4tera: (103)4T Tib 1.0995 Tb250pebi Pi petabinary: (210)5peta: (103)5P PiB 1.1259 PB260exbi Ei exabinary: (210)6exa: (103)6E Eio 1.1529 Eo2The 90 mm diskette has been known by its trade size 3.5 in.IEEEPREFIXES FOR BINA

47、RY MULTIPLES Std 1541-2002Copyright 2009 IEEE. All rights reserved.3The first example represents more of a curiosity than a real problem, for the difference between theadvertised “1.44 MB” and the more accurate 1.47 MB is of little practical importance. The second example,however, calls attention to

48、 an area where there has been real misunderstanding between buyers and sellers ofhard drives. The difference between a gigabyte and a gibibyte is approximately 7.5%.Copyright 200 9 IEEE. All rights reserved.4Annex A(informative) BibliographyB1 IEC 60027-2, Letter symbols to be used in electrical tec

49、hnology, Part 2: Telecommunications and elec-tronics, Amendment 2, 1999-01.B2 IEEE 100,The Authoritative Dictionary of IEEE Standards Terms,Seventh Edition, New York, Instituteof Electrical and Electronics Engineers, Inc.3B3 IEEE Std 260.1-2002, American National Standard Letter Symbols for Units of Measurement (SIUnits, Customary 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.3The IEEE standards or products referred