計(jì)算機(jī)專業(yè)英語（第3版）-練習(xí)及情境對(duì)話 課件 5 chapter5 Reading Material（閱讀材料）

閱讀材料ReadingMaterial計(jì)算機(jī)專業(yè)英語chapterfive

ProgrammingLanguageMissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?Today’sDatabaseLandscape計(jì)算機(jī)專業(yè)英語Computingtechnologyhasmadeapermanentchangeinthewaysbusinessesworkaroundtheworld.Informationthatwasatonetimestoredinwarehousesfulloffilingcabinetscannowbeaccessedinstantaneouslyatthelickofamousebutton.Ordersplacedbycustomersinforeigncountriescannowbeinstantlyprocessedonthefloorofamanufacturingfacility.Although20yearsagomuchofthisinformationhadbeentransportedontocorporatemainframedatabases,officesstilloperatedinabatch-processingenvironment.Ifaqueryneededtobeperformed,someonenotifiedthemanagementinformationsystems(MIS)department;therequesteddatawasdeliveredassoonaspossible(thoughoftennotsoonenough).MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?Today’sDatabaseLandscape計(jì)算機(jī)專業(yè)英語Inadditiontothedevelopmentoftherelationaldatabasemodel,twotechnologiesledtotherapidgrowthofwhatarenowcalledclient/serverdatabasesystems.Thefirstimportanttechnologywasthepersonalcomputer.Inexpensive,easy-to-useapplicationssuchasLotus1-2-3andWordPerfectenabledemployees(andhomecomputerusers)tocreatedocumentsandmanagedataquicklyandaccurately.Usersbecameaccustomedtocontinuallyupgradingsystemsbecausetherateofchangewassorapid,evenasthepriceofthemoreadvancedsystemscontinuedtofall.MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?Today’sDatabaseLandscape計(jì)算機(jī)專業(yè)英語Thesecondimportanttechnologywasthelocalareanetwork(LAN)anditsintegrationintoofficesacrosstheworld.Althoughuserswereaccustomedtoterminalconnectionstoacorporatemainframe,nowwordprocessingfilescouldbestoredlocallywithinanofficeandaccessedfromanycomputerattachedtothenetwork,AftertheAppleMacintoshintroducedafriendlygraphicaluserinterface,computerswerenotonlyinexpensiveandpowerfulbutalsoeasytouse,Inaddition,theycouldbeaccessedfromremotesites,andlargeamountsofdatacouldbeoff-loadedtodepartmentaldataservers,duringthistimeofrapidchangeandadvancement,anewtypeofsystemappeared,calledclient/serverdevelopmentbecauseprocessingissplitbetweenclientcomputersandadatabaseserver,thisnewbreedofapplicationwasaradicalchangefrommainframe-basedapplicationprogramming.Amongthemanyadvantagesofthistypeofarchitectureare:MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?Today’sDatabaseLandscape計(jì)算機(jī)專業(yè)英語Reducedmaintenancecost.Reducednetworkload(processingoccursondatabaseserverorclientcomputer).Multipleoperatingsystemsthatcaninteroperateaslongastheyshareacommonnetworkprotocol.Improveddataintegrityowingtocentralizeddatalocation.InImplementingClient/ServerComputing,BernardH.Boardefinesclient/servercomputingasfollows:Client/Severcomputingisaprocessingmodelinwhichasingleapplicationispartitionedbetweenmultipleprocessors(front-endandback-end)andtheprocessorscooperate(transparenttotheenduser)tocompletetheprocessingasasingleunifiedtask.ImplementingClient/ServerComputingAclient/serverbondproducttiestheprocessorstogethertoprovideasinglesystemimage(illusion).Shareableresourcesarepositionedasrequestorclientsthataccessauthorizedservices.Thearchitectureisendlesslyrecursive;MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?Today’sDatabaseLandscape計(jì)算機(jī)專業(yè)英語inturn,serverscanbecomeclientsandrequestservicesofotherserversonthenetwork,andsoonandsoon.Thistypeofapplicationdevelopmentrequiresanentirelynewsetofprogrammingskills.Userinterfaceprogrammingisnowwrittenforgraphicaluserinterfaces,whetheritisMSWindows,IBMOS/2,AppleMacintosh,ortheUNIXX-Windowsystem.UsingSQLandanetworkconnection,theapplicationcaninterfacetoadatabaseresidingonaremoteserver.Theincreasedpowe