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1、IT专业英语UNIT8 Operating SystemUNIT 8 OperatingSystemUNIT 8 OperatingSystemUNIT 8 OperatingSystem8-1 Technical Part 8-1-1 DefinitionAnoperatingsystemisaprogramdesignedtorunotherprogramsonacomputer.Acomputersoperatingsystemisitsmostimportantprogram.Itisconsideredthebackboneofacomputer,managingbothsoftwa
2、reandhardwareresources.Operatingsystemsareresponsibleforeverythingfromthecontrolandallocationofmemorytorecognizinginputfromexternaldevicesandtransmittingoutputtocomputerdisplays.Theyalsomanagefilesoncomputerharddrivesandcontrolperipherals,likeprintersandscanners.UNIT 8 OperatingSystem8-1-2 Introduct
3、ionsFunctionalities of Operating SystemTheoperatingsystemofalargecomputersystemhasevenmoreworktodo.Suchoperatingsystemsmonitordifferentprogramsandusers,makingsureeverythingrunssmoothly,withoutinterference,despitethefactthatnumerousdevicesandprogramsareusedsimultaneously.Anoperatingsystemalsohasavita
4、lroletoplayinsecurity.Itsjobincludespreventingunauthorizedusersfromaccessingthecomputersystem.Todaymostoperatingsystemsperformthefollowingimportantfunctions:UNIT 8 OperatingSystemUNIT 8 OperatingSystemUNIT 8 OperatingSystem3.FileManagementTheoperatingsystemalsohandlestheorganisationandtrackingoffile
5、sanddirectories(folders)savedorretrievedfromacomputerdisk.Thefilemanagementsystemallowstheusertoperformsuchtasksascreatingfilesanddirectories,renamingfiles,copingandmovingfiles,anddeletingfiles.Theoperatingsystemkeepstrackofwherefilesarelocatedontheharddrivethroughthetypeoffilesystem.Thetwomaintypes
6、offilesystemareFileAllocationtable(FAT)orNewTechnologyFilesystem(NTFS)UNIT 8 OperatingSystem4.HardwareManagementOperatingsystemsinterfacewithhardwaredriversthatmanagetheactualphysicalhardwaresuchasharddrives,modems,processors,memoryandprinters.Thehardwaredriversprovidealayerofabstractionsothattheope
7、ratingsystemdoesnothavetoknowaboutaspecificdevice,butratherhowtocommunicatewithitsdriver.Thedrivertypicallyhastoplaybycertainrulesthattheoperatingsystemexpects,allowingdriversoftwareupdateswithoutdisruption.UNIT 8 OperatingSystem5.UserInterfaceManagementTheoperatingsystemalsomanagestheuserinterface,
8、whethergraphicalortext-based.Thisfunctiondoesinvolvethehardwaremanagementcomponentmentionedabove,butonamoreadvancedlevel.Theuserinterfacemustrespondtotheusersdirectionsviamouse,keyboard,touchscreenorotherinputdevice.Thepartoftheoperatingsystemthatmanagesthisfunctionmusttranslatekeypresses,mouseclick
9、sandotheruseractionsintotheappropriatecommandstotheotherpartsofthecomputer.UNIT 8 OperatingSystem6.PriorityManagementTheoperatingsystemmustprioritizeandmanagetheschedulingofthevariousapplicationsrunningonthecomputer.Forinstance,ifyouaredownloadingalargefile,butwanttoworkonadocumentwhileitdownloads,t
10、heoperatingsystemslicestheprocessoravailabilitytogiveprioritytoyourinputactionswhilemanagingthedownloadinthebackground.Thisissometimescalledpreemptivescheduling,asanythingthattheuserdoestakespriorityandpreemptsotherlessimportanttasks.Thisabilitytocarveupprocessortimegiveswhatisactuallyasingle-taskin
11、gOStheappearanceofamulti-taskingOS.UNIT 8 OperatingSystem7.TaskManagementTheoperatingsystemperformsbasiccomputertasks,suchasmanagingthevariousperipheraldevicessuchasthemouse,keyboardandprinters.Forexample,mostoperatingsystemsnowareplugandplaywhichmeansadevicesuchasaprinterwillautomaticallybedetected
12、andconfiguredwithoutanyuserintervention.UNIT 8 OperatingSystemClassification of Operating SystemOperatingsystemscanbeclassifiedasfollows:1.MultiuserMultiuseroperatingsystemsallowtwoormoreuserstorunprogramsatthesametime.Someoperatingsystemspermithundredsoreventhousandsofconcurrentusers.Theoperatingsy
13、stemsofmainframesandminicomputersaremultiusersystem.UNIT 8 OperatingSystem2.MultiprocessingMultiprocessingreferstoacomputersystemabilitytosupportmorethanoneprocessatthesametime.Multiprocessingoperatingsystemsenableseveralprogramstorunconcurrently.MVSandUNIXaretwoofthemostwidelyusedmultiprocessingsys
14、tems,buttherearemanyothers,includingOS/2forhighendPCs.UNIT 8 OperatingSystem3.MultitaskingMultitaskingallowsmorethanoneprogramtorunconcurrently.Multitaskingistheabilitytoexecutemorethanonetaskatthesametime,ataskbeingaprogram.Thetermsmultitaskingandmultiprocessingareoftenusedinterchangeably,althoughm
15、ultiprocessingsometimesimpliesthatmorethanoneCPUisinvolved.UNIT 8 OperatingSystem4.MultithreadingMultithreadingallowsdifferentpartsofasingleprogramtorunconcurrently.Multithreadingistheabilityofanoperatingsystemtoexecutedifferentpartsofaprogramcalledthreads,simultaneously.UNIT 8 OperatingSystem5.Real
16、timeRealtimeoperatingsystemissystemsthatrespondtoinputimmediately.Thiscategoryincludesoperatingsystemsdesignedsubstantiallyforthepurposeofcontrollingandmonitoringexternalactivitieswithtimingconstraints.Theyareusedforsuchtasksasnavigation,inwhichthecomputermustreacttoasteadyflowofnewinformationwithou
17、tinterruption.UNIT 8 OperatingSystemSeveral Commonly Used Operating SystemOperatingsystemsprovideasoftwareplatformontopofwhichotherprograms,calledapplicationprograms,canrun.ItisshowninFigure8-1.Theapplicationprogramsmustbewrittentorunontopofaparticularoperatingsystem.Yourchoiceofoperatingsystem,ther
18、efore,determinestoagreatextenttheapplicationsyoucanrun.ForPCs,themostpopularoperatingsystemsareDOS,OS/2,andWindows,butothersareavailable,suchasLinux.UNIT 8 OperatingSystemFigure8-1PositionofoperatingsystemUNIT 8 OperatingSystem1.WindowsWindows,incomputerscience,isapersonalcomputeroperatingsystemsold
19、byMicrosoftCorporationthatallowsuserstoentercommandswithapoint-and-clickdevice,suchasamouse,insteadofakeyboard.TheWindowsoperatingsystemprovidesuserswithaGraphicalUserInterface(GUI),whichallowsthemtomanipulatesmallpictures,calledicons,onthecomputerscreentoissuecommands.Windowsisthemostwidelyusedoper
20、atingsystemintheworld.ItisanextensionofandreplacementforMicrosoftsDiskOperatingSystem(MS-DOS).UNIT 8 OperatingSystemTheWindowsGUIisdesignedtobeanatural,orintuitive,workenvironmentfortheuser.WithWindows,theusercanmoveacursoraroundonthecomputerscreenwithamouse.Bypointingthecursoraticonsandclickingbutt
21、onsonthemouse,theusercanissuecommandstothecomputertoperformanaction,suchasstartingaprogram,accessingadatafile,orcopyingadatafile.Othercommandscanbereachedthroughpull-downorclick-onmenuitems.Thecomputerdisplaystheactiveareainwhichtheuserisworkingasawindowonthecomputerscreen.Thecurrentlyactivewindowma
22、yoverlapwithotherpreviouslyactivewindowsthatremainopenonthescreen.ThistypeofGUIissaidtoincludeWIMPfeatures:windows,icons,menus,andpointingdevice(suchasamouse).UNIT 8 OperatingSystem2.UNIXUNIX,incomputerscience,isamultiuser,multitaskingoperatingsystemoriginallydevelopedbyKenThompsonandDennisRitchieat
23、AT&TBellLaboratoriesin1969foruseonminicomputers(SeeFigure8-2).UNIXexistsinvariousformsandimplementations;amongtheseareversionsdevelopedattheUniversityofCaliforniaatBerkeley(knownasBSDreleases)andversionsreleasedbyAT&T,themostrecentbeingAT&TSystemV.UNIT 8 OperatingSystemUNIXisconsideredapowerfulopera
24、tingsystemwhich,becauseitiswrittenintheClanguage,ismoreportablelessmachine-specificthanotheroperatingsystems.UNIXisavailableinseveralrelatedforms,includingAIX,aversionofUNIXadaptedbyIBM(torunonRISC-basedworkstations),A/UX(agraphicalversionfortheAppleMacintosh),andMach(arewrittenbutessentiallyUNIX-co
25、mpatibleoperatingsystemfortheNeXTcomputer).UNIT 8 OperatingSystemItspopularityisdueinlargeparttothegrowthoftheinterconnectedcomputernetworkknownastheInternet,thesoftwareforwhichinitiallywasdesignedforcomputersthatranUNIX.VariationsofUNIXincludeSunOS(distributedbySUNMicrosystemsInc.),Xenix(distribute
26、dbyMicrosoftCorporation),andLinux.UNIXanditsclonessupportmultitaskingandmultipleusers.Itsfilesystemprovidesasimplemeansoforganizingdiskfilesandletsusersprotecttheirfilesfromotherusers.ThecommandsinUNIXarenotintuitive,however,andmasteringthesystemisdifficult.UNIT 8 OperatingSystemFigure8-2UnixSystemI
27、nterfaceUNIT 8 OperatingSystem3.LinuxLinux(/5links/)isaUNIX-likecomputeroperatingsystemassembledunderthemodeloffreeandopensourcesoftwaredevelopmentanddistribution(SeeFigure8-3).ThedefiningcomponentofLinuxistheLinuxkernel,anoperatingsystemkernelfirstreleased5October1991byLinusTorvalds.UNIT 8 Operatin
28、gSystemLinuxwasoriginallydevelopedasafreeoperatingsystemforIntelx86-basedpersonalcomputers.Ithassincebeenportedtomorecomputerhardwareplatformsthananyotheroperatingsystem.Itisaleadingoperatingsystemonserversandotherbigironsystemssuchasmainframecomputersandsupercomputers:morethan90%oftodays500fastests
29、upercomputersrunsomevariantofLinux,includingthe10fastest.Linuxalsorunsonembeddedsystems(deviceswheretheoperatingsystemistypicallybuiltintothefirmwareandhighlytailoredtothesystem)suchasmobilephones,tabletcomputers,networkrouters,televisionsandvideogameconsoles;theAndroidsysteminwideuseonmobiledevices
30、isbuiltontheLinuxkernel.UNIT 8 OperatingSystemFigure8-3GraphicallogininterfaceofRedFlagLinuxUNIT 8 OperatingSystemThedevelopmentofLinuxisoneofthemostprominentexamplesoffreeandopensourcesoftwarecollaboration:theunderlyingsourcecodemaybeused,modified,anddistributedcommerciallyornon-commerciallybyanyon
31、eunderlicensessuchastheGNUGeneralPublicLicense.TypicallyLinuxispackagedinaformatknownasaLinuxdistributionfordesktopandserveruse.SomepopularmainstreamLinuxdistributionsincludeDebian(anditsderivativessuchasUbuntu),FedoraandopenSUSE.LinuxdistributionsincludetheLinuxkernel,supportingutilitiesandlibrarie
32、sandusuallyalargeamountofapplicationsoftwaretofulfillthedistributionsintendeduse.UNIT 8 OperatingSystem4.VxWorksVxWorksisareal-timeoperatingsystem(RTOS)thatcanbeusedinembeddedsystems(SeeFigure8-4).VxWorkscanbecustomizedeasilyandcanrunonmostprocessorsdesignedfordistributedcomputing.VxWorksisusedtocon
33、trolnetworkandcommunicationdevices,testandmeasurementequipment,computerperipherals,automotivesystems,avionics(aeronauticsandastronautics)equipmentanddiverseconsumerproducts.UNIT 8 OperatingSystemVxWorkshassomesimilaritiestoUNIXandincludesashell,debuggingfunctions,memorymanagement,performancemonitori
34、ngandsupportformultiprocessing.TheOSincludesakernelforpreemptivemultitasking,interruptresponse,interprocesscommunicationandafilesystem.ProgramminginVxWorkscanbedifficultfornovicesbecausetheprogrammermustwritethecodeonanas-neededbasis.However,thefactthatthereisminimalcontenttosaveandrestoremeansthatV
35、xWorksuseslessprocessingpowerthanUNIX,soitcanrunfaster.VxWorksisatrademarkofWindRiverSystems,acompanyspecializinginsoftwareoptimizationandbasedinAlameda,California,USA.UNIT 8 OperatingSystemFigure8-4DevelopmenttoolinterfaceofVxWorksUNIT 8 OperatingSystem8-1-3 Application Case or ExampleWindows 7 Ope
36、rating SystemWindows7isthecurrentreleaseofMicrosoftWindows,aseriesofoperatingsystemsproducedbyMicrosoftforuseonpersonalcomputers,includinghomeandbusinessdesktops,laptops,netbooks,tabletPCs,andmediacenterPCs.Windows7wasreleasedtomanufacturingonJuly22,2009,andreachedgeneralretailavailabilityworldwideo
37、nOctober22,2009,lessthanthreeyearsafterthereleaseofitspredecessor,WindowsVista.Windows7sservercounterpart,WindowsServer2008R2,wasreleasedatthesametime.UNIT 8 OperatingSystemUnlikeWindowsVista,whichintroducedalargenumberofnewfeatures,Windows7wasintendedtobeamorefocused,incrementalupgradetotheWindowsl
38、ine,withthegoalofbeingcompatiblewithapplicationsandhardwarewithwhichWindowsVistawasalreadycompatible.PresentationsgivenbyMicrosoftin2008focusedonmulti-touchsupport,aredesignedWindowsshellwithanewtaskbar,referredtoastheSuperbar,ahomenetworkingsystemcalledHomeGroup,andperformanceimprovements.UNIT 8 Op
39、eratingSystemSomestandardapplicationsthathavebeenincludedwithpriorreleasesofMicrosoftWindows,includingWindowsCalendar,WindowsMail,WindowsMovieMaker,andWindowsPhotoGallery,arenotincludedinWindows7;mostareinsteadofferedseparatelyatnochargeaspartoftheWindowsLiveEssentialssuite.OnlyseveralfunctionsofWin
40、dows7areshownbelow.UNIT 8 OperatingSystem1.Windows 7 Taskbar YoucandosomuchmorefromtheWindows7taskbar(SeeFigure8-5).Windows7staskbarisgreatlyimprovedintwoways.First,youcanpinprogramstoitindefinitelyforeasyquicklaunch.Second,onacrowdeddesktopcoveredwithwindows,usingthenewAeroPeekfeature,youcanpreview
41、individualwindowsfromgroupedtaskbarapplications,andevenclosedocumentsfromthethumbnailsthemselves.UNIT 8 OperatingSystemHoldyourmouseoverthethumbnailtoseeanevenlargerviewofthefile.Youcanalsorearrangeandorganizebuttonsonthetaskbar,includingpinnedprogramsandrunningprogramsthatarentpinned,sotheyappearin
42、theorderyouprefer.Torearrangetheorderofbuttonsonthetaskbar,dragabuttonfromitscurrentpositiontoadifferentpositiononthetaskbar&asoftenasyoulike.UNIT 8 OperatingSystemFigure8-5Windows7TaskbarUNIT 8 OperatingSystem2.ShowDesktopShowdesktoponfarrightcorner,butyoudontneedtoclick,justputyourmouseoverit.Ifyo
43、uwanttokeepthedesktop&minimizethefiles,justclickit(SeeFigure8-6).UNIT 8 OperatingSystemFigure8-6Windows7ShowDesktopUNIT 8 OperatingSystem3.StartMenuInWindows7,youhavemuchmorecontrolovertheprogramsandfilesthatappearontheStartmenu(SeeFigure8-7).TheStartmenuisessentiallyablankslatethatyoucanorganizeand
44、customizetosuityourpreferences.Findaprogramyouwanttoadd&rightmouseclick&chooseaddtostartmenu.UNIT 8 OperatingSystemClickontheStartbuttononleftbottomcorner.Figure8-7Windows7StartMenuUNIT 8 OperatingSystemTheStartMenuList(SeeFigure8-8)willappear&ifyouholdyourmouseovertheprogramyouwillseealistofrecentl
45、yopenedfilesusedbythatprogramontheright.Thisalsoshowsthelocationthatfilewassavedto.UNIT 8 OperatingSystemFigure8-8Windows7StartMenuListUNIT 8 OperatingSystem4.ShakeShakeonewindowtomaketheothersdisappear.Youcaninstantlysnapyourwindowstosize,andclearthedesktopinonemotion.Aswidescreenmonitorsbecomemore
46、common,easierside-by-sidewindowmanagementandWindows7hasitbuiltin.ThenewAeroShakefeatureletsyouclearthedesktopofallbackgroundwindowsbygrabbingthetopbaroftheactivewindowandmovingitbackandforthquickly.UNIT 8 OperatingSystem5.PinPinyourfavoriteprogramsrighttoyourtaskbar.Pinningprogramstothetaskbarcomple
47、mentspinningprogramstotheStartMenu,likeinearlierversionsofWindows.Whenyoupinafavoriteprogramtothetaskbar,youcanalwaysseeitthereandeasilyaccessitwithasingleclick.Windows7alsoincludesJumpLists,sothatinadditiontolaunchingaprogramfromthetaskbar,youcannowlaunchfavoriteandrecentitemsfromthatprogram,justby
48、clickingthesamebutton(SeeFigure8-9).Youcanalsomovethesearoundtobeintheorderyouwant.UNIT 8 OperatingSystemFigure8-9Windows7PinUNIT 8 OperatingSystem6.JumpListsJumpListsarelistsofrecentlyorfrequentlyopeneditems,suchasfiles,folders,tasks,orwebsites,organizedbytheprogramthatyouusetoopenthem(SeeFigure8-1
49、0).InadditiontobeingabletoopenrecentitemsusingaJumpList,youcanalsopinfavoriteitemstoaJumpListsoyoucanquicklygettotheitemsthatyouuseeveryday.UNIT 8 OperatingSystemOnthetaskbar,JumpListsappearforprogramsthatyouvepinnedtothetaskbarandprogramsthatarecurrentlyrunning.YoucanviewtheJumpListforaprogrambyrig
50、ht-clickingthetaskbarbutton,orbydraggingthebuttontowardthedesktop.YouopenitemsfromtheJumpListbyclickingonthem.UNIT 8 OperatingSystemFigure8-10Windows7JumpListsUNIT 8 OperatingSystem 8-2 Reading Material 8-2-1 Reading comprehensioniPhone Operating SystemiOS(previouslyiPhoneOS)isamobileoperatingsystem