IEEE754 标准

IEEEStd754™-2008(RevisionofIEEEStd754-1985)IEEEStandardforFloating-PointArithmeticIEEE3ParkAvenueNewYork,NY10016-5997,USA29August2008IEEEComputerSocietySponsoredbytheMicroprocessorStandardsCommittee754TMAuthorizedlicenseduselimitedto:TIANJINUNIVERSITY.DownloadedonJuly13,2009at05:08fromIEEEXplore.Restrictionsapply.Authorizedlicenseduselimitedto:TIANJINUNIVERSITY.DownloadedonJuly13,2009at05:08fromIEEEXplore.Restrictionsapply.IEEEStd754™-2008(RevisionofIEEEStd754-1985)IEEEStandardforFloating-PointArithmeticSponsorMicroprocessorStandardsCommitteeoftheIEEEComputerSocietyApproved12June2008IEEE-SAStandardsBoardAuthorizedlicenseduselimitedto:TIANJINUNIVERSITY.DownloadedonJuly13,2009at05:08fromIEEEXplore.Restrictionsapply.Abstract:Thisstandardspecifiesinterchangeandarithmeticformatsandmethodsforbinaryanddecimalfloating-pointarithmeticincomputerprogrammingenvironments.Thisstandardspecifiesexceptionconditionsandtheirdefaulthandling.Animplementationofafloating-pointsystemconformingtothisstandardmayberealizedentirelyinsoftware,entirelyinhardware,orinanycombinationofsoftwareandhardware.Foroperationsspecifiedinthenormativepartofthisstandard,numericalresultsandexceptionsareuniquelydeterminedbythevaluesoftheinputdata,sequenceofoperations,anddestinationformats,allunderusercontrol.Keywords:arithmetic,binary,computer,decimal,exponent,floating-point,format,interchange,NaN,number,rounding,significand,subnormalTheInstituteofElectricalandElectronicsEngineers,Inc.3ParkAvenue,NewYork,NY10016-5997,USACopyright©2008bytheInstituteofElectricalandElectronicsEngineers,Inc.Allrightsreserved.Published29August2008.PrintedintheUnitedStatesofAmerica.IEEEisaregisteredtrademarkintheU.S.Patent&TrademarkOffice,ownedbytheInstituteofElectricalandElectronicsEngineers,Incorporated.PDF:ISBN978-0-7381-5752-8STD95802Print:ISBN978-0-7381-5753-5STDPD95802Nopartofthispublicationmaybereproducedinanyform,inanelectronicretrievalsystemorotherwise,withoutthepriorwrittenpermissionofthepublisher.Authorizedlicenseduselimitedto:TIANJINUNIVERSITY.DownloadedonJuly13,2009at05:08fromIEEEXplore.Restrictionsapply.IEEEStandardsdocumentsaredevelopedwithintheIEEESocietiesandtheStandardsCoordinatingCommitteesoftheIEEEStandardsAssociation(IEEE-SA)StandardsBoard.TheIEEEdevelopsitsstandardsthroughaconsensusdevelopmentprocess,approvedbytheAmericanNationalStandardsInstitute,whichbringstogethervolunteersrepresentingvariedviewpointsandintereststoachievethefinalproduct.VolunteersarenotnecessarilymembersoftheInstituteandservewithoutcompensation.WhiletheIEEEadministerstheprocessandestablishesrulestopromotefairnessintheconsensusdevelopmentprocess,theIEEEdoesnotindependentlyevaluate,test,orverifytheaccuracyofanyoftheinformationorthesoundnessofanyjudgmentscontainedinitsstandards.UseofanIEEEStandardiswhollyvoluntary.TheIEEEdisclaimsliabilityforanypersonalinjury,propertyorotherdamage,ofanynaturewhatsoever,whetherspecial,indirect,consequential,orcompensatory,directlyorindirectlyresultingfromthepublication,useof,orrelianceuponthis,oranyotherIEEEStandarddocument.TheIEEEdoesnotwarrantorrepresenttheaccuracyorcontentofthematerialcontainedherein,andexpresslydisclaimsanyexpressorimpliedwarranty,includinganyimpliedwarrantyofmerchantabilityorfitnessforaspecificpurpose,orthattheuseofthematerialcontainedhereinisfreefrompatentinfringement.IEEEStandardsdocumentsaresupplied“ASIS”.TheexistenceofanIEEEStandarddoesnotimplythattherearenootherwaystoproduce,test,measure,purchase,market,orprovideothergoodsandservicesrelatedtothescopeoftheIEEEStandard.Furthermore,theviewpointexpressedatthetimeastandardisapprovedandissuedissubjecttochangebroughtaboutthroughdevelopmentsinthestateoftheartandcommentsreceivedfromusersofthestandard.EveryIEEEStandardissubjectedtoreviewatleasteveryfiveyearsforrevisionorreaffirmation.Whenadocumentismorethanfiveyearsoldandhasnotbeenreaffirmed,itisreasonabletoconcludethatitscontents,althoughstillofsomevalue,donotwhollyreflectthepresentstateoftheart.UsersarecautionedtochecktodeterminethattheyhavethelatesteditionofanyIEEEStandard.Inpublishingandmakingthisdocumentavailable,theIEEEisnotsuggestingorrenderingprofessionalorotherservicesfor,oronbehalfof,anypersonorentity.NoristheIEEEundertakingtoperformanydutyowedbyanyotherpersonorentitytoanother.Anypersonutilizingthis,andanyotherIEEEStandardsdocument,shouldrelyuponhisorherindependentjudgmentintheexerciseofreasonablecareinanygivencircumstancesor,asappropriate,seektheadviceofacompetentprofessionalindeterminingtheappropriatenessofagivenIEEEstandard.Interpretations:Occasionallyquestionsmayariseregardingthemeaningofportionsofstandardsastheyrelatetospecificapplications.WhentheneedforinterpretationsisbroughttotheattentionofIEEE,theInstitutewillinitiateactiontoprepareappropriateresponses.SinceIEEEStandardsrepresentaconsensusofconcernedinterests,itisimportanttoensurethatanyinterpretationhasalsoreceivedtheconcurrenceofabalanceofinterests.Forthisreason,IEEEandthemembersofitssocietiesandStandardsCoordinatingCommitteesarenotabletoprovideaninstantresponsetointe