《IT专业英语》课件UNIT8

UNIT8OperatingSystem

8-1TechnicalPart8-2ReadingMaterial

8-1TechnicalPart

8-1-1Definition

Anoperatingsystemisaprogramdesignedtorunotherprogramsonacomputer.Acomputer’soperatingsystemisitsmostimportantprogram.Itisconsideredthebackboneofacomputer,managingbothsoftwareandhardwareresources.Operatingsystemsareresponsibleforeverythingfromthecontrolandallocationofmemorytorecognizinginputfromexternaldevicesandtransmittingoutputtocomputerdisplays.Theyalsomanagefilesoncomputerharddrivesandcontrolperipherals,likeprintersandscanners.8-1-2Introductions

FunctionalitiesofOperatingSystem

Theoperatingsystemofalargecomputersystemhasevenmoreworktodo.Suchoperatingsystemsmonitordifferentprogramsandusers,makingsureeverythingrunssmoothly,withoutinterference,despitethefactthatnumerousdevicesandprogramsareusedsimultaneously.Anoperatingsystemalsohasavitalroletoplayinsecurity.Itsjobincludespreventingunauthorizedusersfromaccessingthecomputersystem.Todaymostoperatingsystemsperformthefollowingimportantfunctions:

1. ProcessManagement

Aprocessisaprograminexecution.Aprocessneedscertainresources,includingCPUtime,memory,files,andI/Odevices,toaccomplishitstask.OSresponsibilitiesforprocessmanagementinclude:processcreationanddeletion;processscheduling,suspension,andresumption;processsynchronization,inter-processcommunication.

2. MemoryManagement

MemoryisalargearrayofaddressablewordsorbytesoradatarepositorysharedbytheCPUandI/Odevices.OSresponsibilityformemorymanagementinclude:

Allocateanddeallocatememoryspaceasrequested;

Keeptrackofwhichpartsofmemoryarecurrentlybeingusedandbywhom;

Efficientutilizationwhenthememoryresourceisheavilycompeted.

3.FileManagement

Theoperatingsystemalsohandlestheorganisationandtrackingoffilesanddirectories(folders)savedorretrievedfromacomputerdisk.Thefilemanagementsystemallowstheusertoperformsuchtasksascreatingfilesanddirectories,renamingfiles,copingandmovingfiles,anddeletingfiles.Theoperatingsystemkeepstrackofwherefilesarelocatedontheharddrivethroughthetypeoffilesystem.ThetwomaintypesoffilesystemareFileAllocationtable(FAT)orNewTechnologyFilesystem(NTFS)

4. HardwareManagement

Operatingsystemsinterfacewithhardwaredriversthatmanagetheactualphysicalhardwaresuchasharddrives,modems,processors,memoryandprinters.Thehardwaredriversprovidealayerofabstractionsothattheoperatingsystemdoesnothavetoknowaboutaspecificdevice,butratherhowtocommunicatewithitsdriver.Thedrivertypicallyhastoplaybycertainrulesthattheoperatingsystemexpects,allowingdriversoftwareupdateswithoutdisruption.

5. UserInterfaceManagement

Theoperatingsystemalsomanagestheuserinterface,whethergraphicalortext-based.Thisfunctiondoesinvolvethehardwaremanagementcomponentmentionedabove,butonamoreadvancedlevel.Theuserinterfacemustrespondtotheuser’sdirectionsviamouse,keyboard,touchscreenorotherinputdevice.Thepartoftheoperatingsystemthatmanagesthisfunctionmusttranslatekeypresses,mouseclicksandotheruseractionsintotheappropriatecommandstotheotherpartsofthecomputer.

6. PriorityManagement

Theoperatingsystemmustprioritizeandmanagetheschedulingofthevariousapplicationsrunningonthecomputer.Forinstance,ifyouaredownloadingalargefile,butwanttoworkonadocumentwhileitdownloads,theoperatingsystemslicestheprocessoravailabilitytogiveprioritytoyourinputactionswhilemanagingthedownloadinthebackground.Thisissometimescalledpreemptivescheduling,asanythingthattheuserdoestakespriorityandpreemptsotherlessimportanttasks.Thisabilitytocarveupprocessortimegiveswhatisactuallyasingle-taskingOStheappearanceofamulti-taskingOS.

7. TaskManagement

Theoperatingsystemperformsbasiccomputertasks,suchasmanagingthevariousperipheraldevicessuchasthemouse,keyboardandprinters.Forexample,mostoperatingsystemsnowareplugandplaywhichmeansadevicesuchasaprinterwillautomaticallybedetectedandconfiguredwithoutanyuserintervention.ClassificationofOperatingSystem

Operatingsystemscanbeclassifiedasfollows:

1. Multiuser

Multiuseroperatingsystemsallowtwoormoreuserstorunprogramsatthesametime.Someoperatingsystemspermithundredsoreventhousandsofconcurrentusers.Theoperatingsystemsofmainframesandminicomputersaremultiusersystem.

2. Multiprocessing

Multiprocessingreferstoacomputersystemabilitytosupportmorethanoneprocessatthesametime.Multiprocessingoperatingsystemsenableseveralprogramstorunconcurrently.MVSandUNIXaretwoofthemostwidelyusedmultiprocessingsystems,buttherearemanyothers,includingOS/2forhighendPCs.

3. Multitasking

Multitaskingallowsmorethanoneprogramtorunconcurrently.Multitaskingistheabilitytoexecutemorethanonetaskatthesametime,ataskbeingaprogram.Thetermsmultitaskingandmultiprocessingareoftenusedinterchangeably,althoughmultiprocessingsometimesimpliesthatmorethanoneCPUisinvolved.

4. Multithreading

Multithreadingallowsdifferentpartsofasingleprogramtorunconcurrently.Multithreadingistheabilityofanoperatingsystemtoexecutedifferentpartsofaprogramcalledthreads,simultaneously.

5. Realtime

Realtimeoperatingsystemissystemsthatrespondtoinputimmediately.Thiscategoryincludesoperatingsystemsdesignedsubstantiallyforthepurposeofcontrollingandmonitoringexternalactivitieswithtimingconstraints.Theyareusedforsuchtasksasnavigation,inwhichthecomputermustreacttoasteadyflowofnewinformationwithoutinterruption.SeveralCommonlyUsedOperatingSystem

Operatingsystemsprovideasoftwareplatformontopofwhichotherprograms,calledapplicationprograms,canrun.ItisshowninFigure8-1.Theapplicationprogramsmustbewrittentorunontopofaparticularoperatingsystem.Yourchoiceofoperatingsystem,therefore,determinestoagreatextenttheapplicationsyoucanrun.ForPCs,themostpopularoperatingsystemsareDOS,OS/2,andWindows,butothersareavailable,suchasLinux.Figure8-1Positionofoperatingsystem

1. Windows

Windows,incomputerscience,isapersonalcomputeroperatingsystemsoldbyMicrosoftCorporationthatallowsuserstoentercommandswithapoint-and-clickdevice,suchasamouse,insteadofakeyboard.TheWindowsoperatingsystemprovidesuserswithaGraphicalUserInterface(GUI),whichallowsthemtomanipulatesmallpictures,calledicons,onthecomputerscreentoissuecommands.Windowsisthemostwidelyusedoperatingsystemintheworld.ItisanextensionofandreplacementforMicrosoft’sDiskOperatingSystem(MS-DOS).

TheWindowsGUIisdesignedtobeanatural,orintuitive,workenvironmentfortheuser.WithWindows,theusercanmoveacursoraroundonthecomputerscreenwithamouse.Bypointingthecursoraticonsandclickingbuttonsonthemouse,theusercanissuecommandstothecomputertoperformanaction,suchasstartingaprogram,accessingadatafile,orcopyingadatafile.Othercommandscanbereachedthroughpull-downorclick-onmenuitems.Thecomputerdisplaystheactiveareainwhichtheuserisworkingasawindowonthecomputerscreen.Thecurrentlyactivewindowmayoverlapwithotherpreviouslyactivewindowsthatremainopenonthescreen.ThistypeofGUIissaidtoincludeWIMPfeatures:windows,icons,menus,andpointingdevice(suchasamouse).

2. UNIX

UNIX,incomputerscience,isamultiuser,multitaskingoperatingsystemoriginallydevelopedbyKenThompsonandDennisRitchieatAT&TBellLaboratoriesin1969foruseonminicomputers(SeeFigure8-2).UNIXexistsinvariousformsandimplementations;amongtheseareversionsdevelopedattheUniversityofCaliforniaatBerkeley(knownasBSDreleases)

andversionsreleasedbyAT&T,themostrecentbeingAT&TSystemV.

UNIXisconsideredapowerfuloperatingsystemwhich,becauseitiswrittenintheClanguage,ismoreportable—lessmachine-specific—thanotheroperatingsystems.UNIXisavailableinseveralrelatedforms,includingAIX,aversionofUNIXadaptedbyIBM(torunonRISC-basedworkstations),A/UX(agraphicalversionfortheAppleMacintosh),andMach(arewrittenbutessentiallyUNIX-compatibleoperatingsystemfortheNeXTcomputer).

ItspopularityisdueinlargeparttothegrowthoftheinterconnectedcomputernetworkknownastheInternet,thesoftwareforwhichinitiallywasdesignedforcomputersthatranUNIX.VariationsofUNIXincludeSunOS(distributedbySUNMicrosystemsInc.),Xenix(distributedbyMicrosoftCorporation),andLinux.UNIXanditsclonessupportmultitaskingandmultipleusers.Itsfilesystemprovidesasimplemeansoforganizingdiskfilesandletsusersprotecttheirfilesfromotherusers.ThecommandsinUNIXarenotintuitive,however,andmasteringthesystemisdifficult.Figure8-2UnixSystemInterface

3. Linux

Linux(/5linəks/)isaUNIX-likecomputeroperatingsystemassembledunderthemodeloffreeandopensourcesoftwaredevelopmentanddistribution(SeeFigure8-3).ThedefiningcomponentofLinuxistheLinuxkernel,anoperatingsystemkernelfirstreleased5October1991byLinusTorvalds.

LinuxwasoriginallydevelopedasafreeoperatingsystemforIntelx86-basedpersonalcomputers.Ithassincebeenportedtomorecomputerhardwareplatformsthananyotheroperatingsystem.Itisaleadingoperatingsystemonserversandotherbigironsystemssuchasmainframecomputersandsupercomputers:morethan90%oftoday’s500fastestsupercomputersrunsomevariantofLinux,includingthe10fastest.Linuxalsorunsonembeddedsystems(deviceswheretheoperatingsystemistypicallybuiltintothefirmwareandhighlytailoredtothesystem)suchasmobilephones,tabletcomputers,networkrouters,televisionsandvideogameconsoles;theAndroidsysteminwideuseonmobiledevicesisbuiltontheLinuxkernel.Figure8-3GraphicallogininterfaceofRedFlagLinux

ThedevelopmentofLinuxisoneofthemostprominentexamplesoffreeandopensourcesoftwarecollaboration:theunderlyingsourcecodemaybeused,modified,anddistributed—commerciallyornon-commercially—byanyoneunderlicensessuchastheGNUGeneralPublicLicense.TypicallyLinuxispackagedinaformatknownasaLinuxdistributionfordesktopandserveruse.SomepopularmainstreamLinuxdistributionsincludeDebian(anditsderivativessuchasUbuntu),FedoraandopenSUSE.LinuxdistributionsincludetheLinuxkernel,supportingutilitiesandlibrariesandusuallyalargeamountofapplicationsoftwaretofulfillthedistribution’sintendeduse.

4. VxWorks

VxWorksisareal-timeoperatingsystem(RTOS)thatcanbeusedinembeddedsystems(SeeFigure8-4).VxWorkscanbecustomizedeasilyandcanrunonmostprocessorsdesignedfordistributedcomputing.VxWorksisusedtocontrolnetworkandcommunicationdevices,testandmeasurementequipment,computerperipherals,automotivesystems,avionics(aeronauticsandastronautics)equipmentanddiverseconsumerproducts.

VxWorkshassomesimilaritiestoUNIXandincludesashell,debuggingfunctions,memorymanagement,performancemonitoringandsupportformultiprocessing.TheOSincludesakernelforpreemptivemultitasking,interruptresponse,interprocesscommunicationandafilesystem.ProgramminginVxWorkscanbedifficultfornovicesbecausetheprogrammermustwritethecodeonanas-neededbasis.However,thefactthatthereisminimalcontenttosaveandrestoremeansthatVxWorksuseslessprocessingpowerthanUNIX,soitcanrunfaster.

VxWorksisatrademarkofWindRiverSystems,acompanyspecializinginsoftwareoptimizationandbasedinAlameda,California,USA.Figure8-4DevelopmenttoolinterfaceofVxWorks8-1-3ApplicationCaseorExample

Windows7OperatingSystem

Windows7isthecurrentreleaseofMicrosoftWindows,aseriesofoperatingsystemsproducedbyMicrosoftforuseonpersonalcomputers,includinghomeandbusinessdesktops,laptops,netbooks,tabletPCs,andmediacenterPCs.Windows7wasreleasedtomanufacturingonJuly22,2009,andreachedgeneralretailavailabilityworldwideonOctober22,2009,lessthanthreeyearsafterthereleaseofitspredecessor,WindowsVista.Windows7’sservercounterpart,WindowsServer2008R2,wasreleasedatthesametime.

UnlikeWindowsVista,whichintroducedalargenumberofnewfeatures,Windows7wasintendedtobeamorefocused,incrementalupgradetotheWindowsline,withthegoalofbeingcompatiblewithapplicationsandhardwarewithwhichWindowsVistawasalreadycompatible.PresentationsgivenbyMicrosoftin2008focusedonmulti-touchsupport,aredesignedWindowsshellwithanewtaskbar,referredtoastheSuperbar,ahomenetworkingsystemcalledHomeGroup,andperformanceimprovements.

SomestandardapplicationsthathavebeenincludedwithpriorreleasesofMicrosoftWindows,includingWindowsCalendar,WindowsMail,WindowsMovieMaker,andWindowsPhotoGallery,arenotincludedinWindows7;mostareinsteadofferedseparatelyatnochargeaspartoftheWindowsLiveEssentialssuite.

OnlyseveralfunctionsofWindows7areshownbelow.1. Windows7Taskbar

YoucandosomuchmorefromtheWindows7taskbar(SeeFigure8-5).Windows7’staskbarisgreatlyimprovedintwoways.First,youcanpinprogramstoitindefinitelyforeasyquicklaunch.Second,onacrowdeddesktopcoveredwithwindows,usingthenewAeroPeekfeature,youcanpreviewindividualwindowsfromgroupedtaskbarapplications,andevenclosedocumentsfromthethumbnailsthemselves.

Holdyourmouseoverthethumbnailtoseeanevenlargerviewofthefile.Youcanalsorearrangeandorganizebuttonsonthetaskbar,includingpinnedprogramsandrunningprogramsthataren’tpinned,sotheyappearintheorderyouprefer.Torearrangetheorderofbuttonsonthetaskbar,dragabuttonfromitscurrentpositiontoadifferentpositiononthetaskbar&asoftenasyoulike.Figure8-5Windows7Taskbar

2. ShowDesktop

Showdesktoponfarrightcorner,butyoudon’tneedtoclick,justputyourmouseoverit.Ifyouwanttokeepthedesktop&minimizethefiles,justclickit(SeeFigure8-6).Figure8-6Windows7ShowDesktop

3. StartMenu

InWindows7,youhavemuchmorecontrolovertheprogramsandfilesthatappearontheStartmenu(SeeFigure8-7).TheStartmenuisessentiallyablankslatethatyoucanorganizeandcustomizetosuityourpreferences.Findaprogramyouwanttoadd&rightmouseclick&chooseaddtostartmenu.ClickontheStartbuttononleftbottomcorner.Figure8-7Windows7StartMenu

TheStartMenuList(SeeFigure8-8)willappear&ifyouholdyourmouseovertheprogramyouwillseealistofrecentlyopenedfilesusedbythatprogramontheright.Thisalsoshowsthelocationthatfilewassavedto.Figure8-8Windows7StartMenuList

4. Shake

Shakeonewindowtomaketheothersdisappear.Youcaninstantlysnapyourwindowstosize,andclearthedesktopinonemotion.Aswidescreenmonitorsbecomemorecommon,easierside-by-sidewindowmanagementandWindows7hasitbuiltin.ThenewAeroShakefeatureletsyouclearthedesktopofallbackgroundwindowsbygrabbingthetopbaroftheactivewindowandmovingitbackandforthquickly.

5. Pin

Pinyourfavoriteprogramsrighttoyourtaskbar.PinningprogramstothetaskbarcomplementspinningprogramstotheStartMenu,likeinearlierversionsofWindows.Whenyoupinafavoriteprogramtothetaskbar,youcanalwaysseeitthereandeasilyaccessitwithasingleclick.Windows7alsoincludesJumpLists,sothatinadditiontolaunchingaprogramfromthetaskbar,youcannowlaunchfavoriteandrecentitemsfromthatprogram,justbyclickingthesamebutton(SeeFigure8-9).Youcanalsomovethesearoundtobeintheorderyouwant.Figure8-9Windows7Pin

6. JumpLists

JumpListsarelistsofrecentlyorfrequentlyopeneditems,suchasfiles,folders,tasks,orwebsites,organizedbytheprogramthatyouusetoopenthem(SeeFigure8-10).InadditiontobeingabletoopenrecentitemsusingaJumpList,youcanalsopinfavoriteitemstoaJumpListsoyoucanquicklygettotheitemsthatyouuseeveryday.

Onthetaskbar,JumpListsappearforprogramsthatyou’vepinnedtothetaskbarandprogramsthatarecurrentlyrunning.YoucanviewtheJumpListforaprogrambyright-clickingthetaskbarbutton,orbydraggingthebuttontowardthedesktop.YouopenitemsfromtheJumpListbyclickingonthem.Figure8-10Windows7JumpLists8-2ReadingMaterial

8-2-1Readingcomprehension

iPhoneOperatingSystem

iOS(previouslyiPhoneOS)isamobileoperatingsystemdevelopedanddistributedbyAppleInc.Originallyreleasedin2007fortheiPhoneandiPodTouch,ithasbeenextendedtosupportotherAppledevicessuchastheiPadandAppleTV.UnlikeMicrosoft’sWindowsCE(WindowsPhone)andGoogle’sAndroid,AppledoesnotlicenseiOSforinstallationonnon-Applehardware.AsofJune12,2012

(2012-06-12),Apple’sAppStorecontainedmorethan650,000iOSapplications,whichhavecollectivelybeendownloadedmorethan30

billiontimes.Ithada23%shareofthesmart-phoneoperatingsystemunitssoldinthefirstquarterof2012,behindonlyGoogle’sAndroid.InJune2012,itaccountedfor65%ofmobilewebdataconsumption(includinguseonboththeiPodTouchandtheiPad).Atthehalfof2012,therewere410milliondevicesactivated.TheuserinterfaceofiOSisbasedontheconceptofdirectmanipulation,usingmulti-touchgestures.Interfacecontrolelementsconsistofsliders,switches,andbuttons.Theresponsetouserinputisimmediateandprovidesafluidinterface.InteractionwiththeOSincludesgesturessuchasswipe,tap,pinch,andreversepinch,allofwhichhavespecificdefinitionswithinthecontextoftheiOSoperatingsystemanditsmulti-touchinterface.Internalaccelerometersareusedbysomeapplicationstorespondtoshakingthedevice(onecommonresultistheundocommanD.orrotatingitinthreedimensions(onecommonresultisswitchingfromportraittolandscapemode).iOSisderivedfromOSX,withwhichitsharestheDarwinfoundation,andisthereforeaUnixoperatingsystem.IniOS,therearefourabstractionlayers:theCoreOSlayer,theCoreServiceslayer,theMedialayer,andtheCocoaTouchlayer.Thecurrentversionoftheoperatingsystem(iOS5.1.1)dedicates1-1.5GBofthedevice’sflashmemoryforthesystempartition,usingroughly800MBofthatpartition(varyingbymodel)foriOSitself(SeeFigure8-11).Figure8-11iOS5ScreenshotTakenfromiPhoneTheoperatingsystemwasunveiledwiththeiPhoneattheMacworldConference&Expo,January9,2007,andreleasedinJuneofthatyear.Atfirst,Applemarketingliteraturedidnotspecifyaseparatenamefortheoperatingsystem,statingsimplythatthe“iPhonerunsOSX”.Initially,third-partyapplicationswerenotsupported.SteveJobsarguedthatdeveloperscouldbuildwebapplicationsthat“wouldbehavelikenativeappsontheiPhone”.OnOctober17,2007,AppleannouncedthatanativeSoftwareDevelopmentKit(SDK)wasunderdevelopmentandthattheyplannedtoputit“indevelopers’handsinFebruary”.OnMarch6,2008,Applereleasedthefirstbeta,alongwithanewnamefortheoperatingsystem:“iPhoneOS”.

ApplehadreleasedtheiPodtouch,whichhadmostofthenon-phonecapabilitiesoftheiPhone.ApplealsosoldmorethanonemillioniPhonesduringthe2007holidayseason.OnJanuary27,2010,AppleannouncedtheiPad,featuringalargerscreenthantheiPhoneandiPodtouch,anddesignedforwebbrowsing,mediaconsumption,andreadingiBooks.

InJune2010,ApplerebrandediPhoneOSas“iOS”.Thetrademark“IOS”hadbeenusedbyCiscoforoveradecadeforitsoperatingsystem,IOS,usedonitsrouters.Toavoidanypotentiallawsuit,Applelicensedthe“IOS”trademarkfromCisco.

Words&Expressions

licensevt.发放许可

smart-phone智能手机

activatevt.激活

gesturen.手势

directmanipulation直接操作

responseto对……响应interactionwith与……交互作用

immediateadj.直接的

fluidadj.流畅的

definitionsn.定义

multi-touchinterface多点触摸界面

accelerometersn.感应器dimensionsn.维度

abstractionn.抽象

currentversion当前版本

flashmemory闪存

partitionn.分区

trademarkn.(注册)商标8-2-2Exercises

I.Fillineachoftheblankswithoneofthewordsgiveninthefollowinglist,makingchangesifnecessary.

operatingsystem,pointingdevice,point-and-clickdevice,pull-down,activewindow,manipulate,cursor,workenvironment,icons

Windows,incomputerscience,isapersonalcomputer

soldbyMicrosoftCorporationthatallowsuserstoentercommandswitha

,suchasamouse,insteadofakeyboard.TheWindowsoperatingsystemprovidesuserswithag