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1、TheEvolutionofCharacterCodes,1874-1968EricFischerenf@pobox.comAbstractÉmileBaudot'sprintingtelegraphwasthefirstwidelyadopteddevicetoencodeletters,numbers,andsymbolsasuniform-lengthbinarysequences.DonaldMurrayintroducedasecondsuccessfulcodeofthistype,thedetailsofwhichcontinuedtoevolveuntilversi
2、onsofBaudot'sandMurray'scodeswerestandardizedasInternationalTele-graphAlphabetsNo.1andNo.2,respectively.Thesecodeswereusedfordecadesbeforetheappearanceofcom-putersandthechangingneedsofcommunicationsrequiredthedesignandstandardizationofanewcode.YearsofdebateandcompromiseresultedintheECMA-6stan
3、dardinEurope,theASCIIstandardintheUnitedStates,andtheISO646andInternationalAlphabetNo.5standardsinternationally.ThisworkhasbeensubmittedtotheIEEEforpossiblepublication.Papercopies:Copyrightmaybetransferredwithoutnotice,afterwhichthisversionwillbesuperseded.Electroniccopies:Copyrightmaybetrans
4、ferredwithoutnotice,afterwhichthisversionmaynolongerbeaccessible.Introductionwerereceived,wouldprinttheminordinaryalpha-Todaywetakeitforgrantedthata``plaintext''beticcharactersonastripofpaper.Hereceivedafileonacomputercanbereadbynearlyanyprogram,patentforsuchasystemonJune17,1874.3,4,5printedon
5、anyprinter,displayedonanyscreen,trans-Baudot'swasnotthefirstprintingtelegraph,butitmittedoveranynetwork,andunderstoodequallyeas-madeconsiderablymoreefficientuseofcommunica-ilybyanyothermakeormodelofcomputer.PlaintionslinesthananearliersysteminventedbyDavidE.textisplain,though,onlybecauseofanear
6、-universalHughes.Hughes'sprintercontainedacontinuallyagreementaboutwhatsymbolsandactionscorre-rotatingwheelwithcharactersengravedonitinthespondtowhatarbitraryarrangementofbits,anagree-ordershowninFigure2.Acharactercouldbeprintedmentthatwasreachedonlyaftermanyyearsofdesignbysendingasinglepulse
7、overthetelegraphline,butwork,experimentation,andcompromise.dependingonthecurrentpositionofthewheelitThefirstportionofthepaperwillcovertheoriginsmighttakenearlyacompleterotationbeforethecor-ofInternationalTelegraphAlphabetNo.2(oftenrectcharacte
