計(jì)算機(jī)專業(yè)英語（第3版）-練習(xí)及情境對話 課件 2 Reading Material（閱讀材料）

閱讀材料ReadingMaterial計(jì)算機(jī)專業(yè)英語chaptertwoComputerSystemMaintenanceMissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?HowComputerVirusesWork計(jì)算機(jī)專業(yè)英語Acomputervirus—anunwantedprogramthathasenteredyoursystemwithoutyouknowingaboutit—hasinfectorandthedetonator.Theyhavetwoverydifferentjobs.Oneofthefeaturesofacomputervirusthatseparateditfromotherkindsofcomputerprogramisthatitreplicatesitself,sothatitcanspread(fromcomputertocomputer,ornetworks)toothercomputers.Aftertheinfectorhascopiedtheviruselsewhere,thedetonatorperformsthevirus’smainwork.Generally,thatworkiseitherdamagingdataonyourdisks,alteringwhatyouseeonyourcomputerdisplay,ordoingsomethingelsethatinterfereswiththenormaluseofyourcomputer.MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?HowComputerVirusesWork計(jì)算機(jī)專業(yè)英語Don’tworrytoomuchaboutviruses.Youmayneverseeone.Therearejustafewwaystobecomeinfectedthatyoushouldbeawareof.Thesourcesseemtobeservicepeople,piratedgames,puttingfloppiesinpubliclyavailablePCswithoutwrite-protecttabs,commercialsoftware(rarely),andsoftwaredistributedovercomputerbulletinboardsystems(alsoquiterarely,despitemediamisinformation).Manyviruseshavespreadthroughpirated-illegallycopiedorbroken-games.Thisiseasyavoided.Payforyourgames,fairandsquare.IfyouuseasharedPCoraPCthathaspublicaccess,suchasoneinacollegePClaboralibrary,beverycarefulaboutputtingfloppiesintothatPC’sdrives,carryavirus-checkingprogramandscanthePCbeforelettingitwritedataontofloppies.MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?HowComputerVirusesWork計(jì)算機(jī)專業(yè)英語Despitethelowincidenceofactualviruses,itcan’thurttorunaviruscheckingprogramnowandthen.Thereareactuallytwokindsofantivirusprograms:virusesshieldsandvirusscanners.Virusesaresomethingtoworryabout,butnotalot.Alittlecommonsenseandtheoccasionalvirusscanwillkeepyouvirus-free.Rememberthesefourpoints:Virusescan’tinfectadataoratextfile.Beforerunninganantivirusprogram,besuretocold-bootfromawrite-protectedfloppy.Don’tbootfromfloppiesexceptreliableDOSdisksoryouroriginalproductiondisks.Stayawayfrompiratedsoftware.MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?FutureMemories計(jì)算機(jī)專業(yè)英語Chipmakersaresearchingforcheap,fast,“universal”memoriestoreplaceDRAM,SRAMandflash.For40years,systemdesignerhaveseenmemorydensitiesdoubleevery18～24monthswhilememorychippriceshaveremainedessentiallyflat,cuttingthecostperbitinhalfeachtime.Asthetechnicalchallengesofbuildingever-smallermemorycellsinsiliconhaveincreased,however,somememorymanufacturershavepredictedthatthecostcurvewillstarttoswingtheotherwaybeforetheendofthedecade.MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?FutureMemories計(jì)算機(jī)專業(yè)英語Researchersareworkingonseveralalternatetechnologiesthatcouldeventuallyreplacethoseinthethreememorytypescommonlyusedtoday:Low-costdynamicRAM(DRAM),usedinPCsandservers;faststaticRAM(SRAM),usedforprocessorcachesandmobiledevices;andnonvolatileflashmemory,usedineverythingfromcomputerBIOSstocellphones.ResearchersatIBM,IntelCorp.andothercompaniesenvisionthedevelopmentofauniversalmemorytechnologythatcouldsomedayreplaceallthree.Auniversalmemorytechnologycouldchangehowcomputersaredesigned.Forexample,nonvolatileRAMcouldallowcomputerstobootupandpowerdowninstantlybecausestoredinformationwouldn’tbelostwhenpowerwasdown.Buttheemergenceofauniversalmemorytechnologyisprobablyatleast10～15yearsaway.MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?FutureMemories計(jì)算機(jī)專業(yè)英語Othersarguethatauniversalmemoryisn’tpossiblebecauseonememorytypecan’tsatisfyallneeds.Forexample,nothingcouldbethefastestandcheapestatthesametime.Mostresearchtodayisfocusedonaddressingthelimitationsofonememorytechnologyatatime,suchasflash.Butsomeattributesoftoday’stechnologieswillbehardtobeat.MosttechnologieswillprobablynotbeabletocompeteonlowestcostperbitagainstDRAMorwiththefastestSRAM.Sotheywillfallintothatspaceinbetween.FerroelectricRAM(FRAM)andmagnetoresistiveRAM(MRAM)arethebest-fundedandmost-evolvedoftheemergingmemorytechnologies.FRAMisanonvolatileRAMthatwasdevelopedbyRamtronInternationalCorp.inColoradoSprings.MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?Futur