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1、17ComputeranalysisMostmanufacturersofcomputerhardware,andmanysuppliersofcomputersoftware,havewrittenprogramsforanalysingcriticalpathnetworksusingcomputers.Whilethevariouscommerciallyavailableprogramsdifferindetail,theyallfollowabasicpattern,andgive,byandlarge,asimila
2、rrangeofoutputs.Incertaincircumstancesacontractormaybeobligedbyhiscontractualcommitmentstoprovideacomputer-izedoutputreportforhisclient.Indeed,whenaclientorganizationhasstandardizedonapartic-ularprojectmanagementsystemforcontrollingtheoverallproject,thecontractormayw
3、ellberequiredtousethesameproprietarysystemsothatthecontractor’sreportscanbeintegratedintotheoverallprojectcontrolsystemonaregularbasis.HistoryThedevelopmentofnetworkanalysistechniquesmoreorlesscoincidedwiththatofthedigitalcomputer.Theearlynetworkanalysisprogramswere,
4、therefore,limitedbythestorageandprocessingcapacityofthecomputeraswellastheinputandoutputfacilities.ProjectPlanningandControlThetechniquesemployedmainlyinvolvedproducingpunchedcards(onecardforeachactivity)andfeedingthemintothemachineviaacardreader.Theseproceduresweret
5、imeconsumingandtedious,and,becausethepunchingofthecardswascarriedoutbyanoperatorwhousuallyunderstoodlittleoftheprogramoritspurpose,mistakesoccurredwhichonlybecameapparentaftertheprintoutwasproduced.Eventhen,theerrorwasnotimmediatelyapparent–onlytheeffect.Itthenoftent
6、ookhourstoscanthroughthereamsofprintoutsheetsbeforetheactualmistakecouldbelocatedandrectified.Toaddtothefrustrationoftheplanner,thenewprintoutmaystillhavegivenridiculousanswersbecauseaseconderrorwasmadeonanothercard.Inthiswayitoftenrequiredseveralrunsbeforeasatisfact
7、oryoutputcouldbeissued.Inanendeavourtoeliminatepunchingerrorsattemptsweremadetousetwoseparateoperators,whopunchedtheirownsetofinputcards.Thecardswerethenautomaticallycomparedand,ifnotidentical,werethrownout,indicatinganerror.Needlesstosay,suchapracticecosttwiceasmuch
8、inmanpower.Becausetheseearlycomputerswerelargeandveryexpensive,usuallyrequiringtheirownair-conditioningequipmentandateamofoperators
