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PCB是进程存在的唯一标识。
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下列关于进程控制块PCB的叙述中哪些是正确的 Ⅰ．系统利用PCB描述进程的基本静态特征 Ⅱ．PCB
Ⅰ和Ⅱ
Ⅱ和Ⅲ
Ⅰ和Ⅲ
全都正确
试说明PCB的作用为什么说PCB是进程存在的唯一标志
进程控制块PCB中包含多种信息以下信息中不是进程控制块中内容的是
优先级
标识
位置
页面大小
在下列叙述中正确的一条是______
分时系统中，时间片越小，响应时间越长
多道程序的引入，主要是为了提高CPU及其他资源的利用率
飞机票订票系统是分时系统
PCB是进程存在的唯一标志，而程序是系统感知进程存在的唯一实体
进程是程序的一次执行______是进程存在的唯一标志
程序
数据
进程控制块
进程标识符
在下列叙述中错误的一条是______
进程被撤销时，只需释放其跚就可以了，因为PCB是进程存在的唯一标志
进程的互斥和同步都能用P-V原语实现
用户程序中执行系统调用命令时，处理机的状态字将发生改变
设备独立性是指用户在编程时，所使用的设备与实际设备无关
系统判断进程的唯一实体是______
JCB
FCB
PCB
SJT
从静态的角度看进程是由DEF三部分组成其中F是进程存在的唯一标志当几个进程共享D时D应当是可重入代码
进程控制模块PCBProcessControlBlock随进程的产生而建立随进程的消亡 而撤消是系统
唯一标识
通用标识
通用名称
文件名
操作系统在控制和管理进程过程中进程存在的唯一标志涉及到的一个重要数据结构是
FCB
FIFO
PCB
FDT
下列关于进程控制块PCB的叙述中正确的是Ⅰ．系统利用PCB描述进程的基本静态特征Ⅱ．PCB可用于描述
Ⅰ和Ⅱ
Ⅱ和Ⅲ
Ⅰ和Ⅲ
全都正确
系统感知进程的唯一实体是
JCB
FCB
PCB
SJT
在下列叙述中错误的一条是______
进程被撤销时，只需释放其PCB就可以了，因为PCB是进程存在的唯一标志
进程的互斥和同步都能用P-V原语实现
用户程序中执行系统调用命令时，处理机的状态字将发生改变
设备独立性是指用户在编程时，所使用的设备与实际设备无关
UNIX系统给每个进程分配唯一的进程ID用户在进程存在期间用进程ID标识 一个进程
随进程的产生而建立随进程的消亡而撤消它是系统中进程的唯一标识
PCB有何作用为什么说PCB是进程存在的唯一标志
是进程存在的标志
程序段
数据
代码
进程控制块(PCB)
操作系统在控制和管理进程的过程中涉及到______这一重要数据结构这是进程存在的唯一标志
FCB
FIFO
FDT
PCB
系统感知进程的唯一实体是______
JCB
FCB
PCB
SJT
进程存在的标志是____________PCB
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有5个进程PaPbPcPd和Pe它们依次进入就绪队列它们的优先级和需要的处理机时间如表2-14所示表2-14进程—处理机—优先级表进程处理机时间优先级Pa103Pb11Pc23Pd14Pe52忽略进程调度等所花费的时间请回答下列问题1分别写出采用先来先服务和非抢占式的优先数优先数大优先级低调度算法选中进程执行的次序2分别计算出上述两种算法使各进程在就绪队列中的等待时间及两种算法下的平均等待时间3某单处理机系统中采用多道程序设计现有10个进程存在则处于运行阻塞和就绪状态的进程数量最小和最大值分别可能是多少
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ThemostthoroughlystudiedintellectualsinthehistoryoftheNewWorldaretheministersandpoliticalleadersofseventeenth-centuryNewEngland.AccordingtothestandardhistoryofAmericanphilosophynowhereelseincolonialAmericawas“somuchimportanceattachedtointellectualpursuits.”AccordingtomanybooksandarticlesNewEngland’sleadersestablishedthebasicthemesandpreoccupationsofanunfoldingdominantPuritantraditioninAmericanintellectuallife. TotakethisapproachtotheNewEnglandersnormallymeanstostartwiththePuritans’theologicalinnovationsandtheirdistinctiveideasaboutthechurch—importantsubjectsthatwemaynotneglect.ButinkeepingwithourexaminationofsouthernintellectuallifewemayconsidertheoriginalPuritansascarriersofEuropeancultureadjustingtoNewWorldcircumstances.TheNewEnglandcolonieswerethescenesofimportantepisodesinthepursuitofwidelyunderstoodidealsofcivilityandvirtuosity. TheearlysettlersofMassachusettsBayincludedmenofimpressiveeducationandinfluenceinEngland.BesidestheninetyorsolearnedministerswhocametoMassachusettschurchesinthedecadeafter1629therewerepoliticalleaderslikeJohnWinthropaneducatedgentlemanlawyerandofficialoftheCrownbeforehejourneyedtoBoston.ThesemenwroteandpublishedextensivelyreachingbothNewWorldandOldWorldaudiencesandgivingNewEnglandanatmosphereofintellectualearnestness. WeshouldnotforgethoweverthatmostNewEnglanderswerelesswelleducated.Whilefewcraftsmenorfarmersletalonedependentsandservantsleftliterarycompositionstobeanalyzeditisobviousthattheirviewswerelessfullyintellectualized.Theirthinkingoftenhadatraditionalsuperstitiousquality.AtailornamedJohnDanewhoemigratedinthelate1630sleftanaccountofhisreasonsforleavingEnglandthatisfilledwithsigns.Sexualconfusioneconomicfrustrationsandreligioushope—allcametogetherinadecisivemomentwhenheopenedtheBibletoldbasfatherthatthefirstlinehesawwouldsettlehisfateandreadthemagicalwords:"ComeoutfromamongthemtouchnouncleanthingandIwillbeyourGodandyoushallbemypeople."OnewonderswhatDanethoughtofthecarefulsermonsexplainingtheBiblethatheheardinPuritanchurches. MeanwhilemanysettlershadslighterreligiouscommitmentsthanDane’sasoneclergymanlearnedinconfrontingfolkalongthecoastwhomockedthattheyhadnotcometotheNewWorldfurreligion."Ourmainendwastocatchfish. ThestoryofJohnDaneshowsthatlesswell-educatedNewEnglanderswereoften
假设有一台多道程序的计算机每个作业都有相同的特征即在一个计算周期T里I/O占用第一和第四个1/4周期处理器占有第二和第三个1/4周期而各个作业占用的I/O设备各不相同如果计算机被任何一个作业单独占用的话完成作业总共需要1个计算周期假设使用时间片轮转进程调度策略而且I/O操作能与处理器操作重叠不同的I/O设备可以同时运行定义以下变量周转时间=完成一个作业的实际时间吞吐量=每周期T完成的作业的数量的平均值处理器使用率=处理器处于活动状态非等待的时间在总时间中占的百分比若有两个作业同时要求运行作业l的优先级较高作业都只运行一次进程状态转换时的操作系统开销忽略不计且时间片的大小远小于T计算1作业1和作业2各自的周转时间2从作业开始运行到两个作业都已完成的瞬间计算机系统的吞吐量和处理器使用率
假设一个计算机系统具有如下性能特征处理一次中断平均耗用1毫秒一次进程调度平均需要2毫秒将CPU分配给选中的进程又需要平均1毫秒再假设其定时器芯片每秒产生100次中断请回答1操作系统将百分之几的CPU时间用于时钟中断处理2如果操作系统采用轮转法调度10个时钟中断为1个时间片那么操作系统将百分之几的CPU时间用于进程调度包括调度分配CPU和引起调度的时钟中断处理时间
[A]Convenientpackaging [B]Healthandwellness [C]Skepticalcustomers [D]Enormousmarkets [E]Soaringsales [F]Trendydrink Inthelast40yearsthebottledwaterindustryhasgonefromabusinessprospectthatfewtookseriouslytoaglobalindustryworthbillionsofpounds.Thecommodityitselfremainssimple.Thewaywethinkaboutithaschangedfundamentally.Waterisnaturalpureandsourcedatminimalcost.Itsrealvalueliesinitsmarketingandbranding."Ithinkbottledwateristhemostrevealingsubstanceforshowingushowtheglobalcapitalistmarketworkstoday"saysRichardWilkprofessorofanthropologyatIndianaUniversity."Inasensewe’rebuyingchoicewe’rebuyingfreedom.That’stheonlythingthatcanexplainwhyyouwouldpaymoneyforabottleofsomethingthatyoucanotherwisegetforfree." 41.______ Throughaconfectionofadvertisingandmarketingbottledwaterhasbecomeoneofthebiggestsuccessstoriesinthemodernfoodandbeverageindustry."Thedemandforbottlewaterhasgrownexponentiallyinthelastfewdecades"saysDr.PeterGleickauthorofBottledandSold."It’sdoubledit’sdoubledagainandit’sdoubledagain.Andthebottlewatercompaniesseeenormousmarketsnotjustintherichcountriesbutalsointhepoorercountries." Noactualvariety Somepeoplethinkthatbottledwateristhehighpointofglobalcapitalismparticularlythepeopleinthebottledwaterbusiness."Ithinkbottledwateractuallyrepresentsakindofcaricatureoftheglobaleconomy.Itprovidespeopleinthedevelopedworldwith20or30varietiesofsomethingforwhichthereisnoactualvariety"saysCharlesFishmanauthorofTheBigThirst. 42.______. Atthebeginningtherereallywasnovarietyandthebottledwaterphenomenonbeganwithonebrand.Perrier佩绿雅矿泉水品牌wasatriumphofadvertisingcreatingabrandthatwastodefineageneration.AttheheartofthecampaigntomakethebrandpopularwasRichardWheatleyoftheLeoBurnettadvertisingagencybetween1979and1994."Perrierpopularisedbottledwater"hesays."Itmadeitacceptablemorethanacceptableitmadeit...desirable."Butitwasnotaninstantsuccess.WhenPerrierUKwaslookingtoincreaseitssalesintheearly1970’sitfacedaskepticalpublic.Manyquestionedwhyanyonewouldbuywaterwhenyoucouldgetitfreefromthetap. 43.______. FacedwithobstaclesPerrierturnedtoadvertisingwithacampaignthatwastochangeourconsumerlandscapeforever.Thecampaignwasamarketingcoupandsaleswentthroughtherooffrom12millionbottlesin1980to152millionbytheendofthedecade.Perrierwasnolongerjustabottleofwater.Themarketingandadvertisingteamshadestablishedacrucialemotionallinkbetweentheproductandtheconsumers."Perrierbecameabadge"saysMichaelBellaschairmanoftheBeverageMarketingCorporation."WhenyouheldaPerrierbottleupitsaidsomethingaboutyourselfitsaidyouweresophisticatedyouunderstoodwhatwashappeningintheworld.Itwasaperfectbeveragefortheyoungandcomingbusinessexecutivesthetrend-setters." 44.______. Inanageofinstantgratificationstillwaterinportablebottlesprovidedwhatpeopleneededexactlywhentheyneededit."Peopleingeneralaremoreandmoretimepressed"saysMr.Fishman."Wedon’tcookourownmealsanymoreweeatpreparedfoodsofallkinds.Andthere’snothingmoreappealingthanabottleofcoldwateratamomentwhenyou’rereallythirsty.ButIthinkbottledwaterisoneofthoseproductsthatonmanyoccasionswhenpeoplebuyitwhatthey’rebuyingisn’tthewatersomuchasthebottle.Thatisthepackageandtheconvenienceatthatmoment." 45.______. WhenpeopleboughtthisconveniencewhattheywerereallybuyingwasPolyethyleneTerephthalateorPETthesinglemostimportantinnovationintheindustry’shistory.StrongshatterproofandahighlyvaluedformofpolyesterPETisaby-productoftheoilindustry.Itisnowutilisedinthepackagingofeverythingfrompharmaceuticalsandsoaptoreadymeals.InyearstocometheenvironmentalimpactofPETwouldhaunttheindustryandraisequestionsaboutitsverysurvivalbutinthe1990sthiswasarevolution.AccordingtoMr.Bellasitwasbehindthesubsequentincrediblegrowthoftheindustry."StartingwiththeintroductionofthesmallpremiumPETwatersthecategorystartedtoexplode"saysMr.Bellas."ThebottledwaterindustrybeforePETonthelistofallbeveragecategorieswasnumberseven.WiththeadventofPETwaterjumpedtothenumbertwospotbehindcarbonatedsoftdrinks." Bybrandingandmarketingwaterbottledwaterhasbeentransformedfromsomethingthatmanyofustookforgrantedintoaproductthatnowmakesbillionsforglobalmultinationalcompanies. 41
某系统中进程有如图2-16所示的状态变化 请回答下列问题 把图中发生①～④的状态变化原因填入表2-12中
设系统中有下述解决死锁的办法1银行家算法2检测死锁终止处于死锁状态的进程释放该进程所占有的资源3资源预分配请问哪种办法允许最大的并发性即哪种办法允许更多的进程无等待地向前推进请按并发性从大到小对上述三种办法进行排序
进程控制块有哪些作用
ThemostthoroughlystudiedintellectualsinthehistoryoftheNewWorldaretheministersandpoliticalleadersofseventeenth-centuryNewEngland.AccordingtothestandardhistoryofAmericanphilosophynowhereelseincolonialAmericawas“somuchimportanceattachedtointellectualpursuits.”AccordingtomanybooksandarticlesNewEngland’sleadersestablishedthebasicthemesandpreoccupationsofanunfoldingdominantPuritantraditioninAmericanintellectuallife. TotakethisapproachtotheNewEnglandersnormallymeanstostartwiththePuritans’theologicalinnovationsandtheirdistinctiveideasaboutthechurch—importantsubjectsthatwemaynotneglect.ButinkeepingwithourexaminationofsouthernintellectuallifewemayconsidertheoriginalPuritansascarriersofEuropeancultureadjustingtoNewWorldcircumstances.TheNewEnglandcolonieswerethescenesofimportantepisodesinthepursuitofwidelyunderstoodidealsofcivilityandvirtuosity. TheearlysettlersofMassachusettsBayincludedmenofimpressiveeducationandinfluenceinEngland.BesidestheninetyorsolearnedministerswhocametoMassachusettschurchesinthedecadeafter1629therewerepoliticalleaderslikeJohnWinthropaneducatedgentlemanlawyerandofficialoftheCrownbeforehejourneyedtoBoston.ThesemenwroteandpublishedextensivelyreachingbothNewWorldandOldWorldaudiencesandgivingNewEnglandanatmosphereofintellectualearnestness. WeshouldnotforgethoweverthatmostNewEnglanderswerelesswelleducated.Whilefewcraftsmenorfarmersletalonedependentsandservantsleftliterarycompositionstobeanalyzeditisobviousthattheirviewswerelessfullyintellectualized.Theirthinkingoftenhadatraditionalsuperstitiousquality.AtailornamedJohnDanewhoemigratedinthelate1630sleftanaccountofhisreasonsforleavingEnglandthatisfilledwithsigns.Sexualconfusioneconomicfrustrationsandreligioushope—allcametogetherinadecisivemomentwhenheopenedtheBibletoldbasfatherthatthefirstlinehesawwouldsettlehisfateandreadthemagicalwords:"ComeoutfromamongthemtouchnouncleanthingandIwillbeyourGodandyoushallbemypeople."OnewonderswhatDanethoughtofthecarefulsermonsexplainingtheBiblethatheheardinPuritanchurches. MeanwhilemanysettlershadslighterreligiouscommitmentsthanDane’sasoneclergymanlearnedinconfrontingfolkalongthecoastwhomockedthattheyhadnotcometotheNewWorldfurreligion."Ourmainendwastocatchfish. Itissuggestedinparagraph2thatNewEnglanders
Researchersinvestigatingbrainsizeandmentalabilitysaytheirworkoffersevidencethateducationprotectsthemindfromthebrain’sphysicaldeterioration. 46Itisknownthatthebrainshrinksasthebodyagesbuttheeffectsonmentalabilityaredifferentfrompersontoperson.Interestinglyinastudyofelderlymenandwomenthosewhohadmoreeducationactuallyhadmorebrainshrinkage. "Thatmayseemlikebadnews"saidstudyauthorDr.EdwardCoffeyaprofessorofpsychiatryandofneurologyatHenryFordHealthSysteminDetroit.47Howeverheexplainedthefindingsuggeststhateducationallowspeopletowithstandmorebraintissuelossbeforetheirmentalfunctioningbeginstobreakdown. ThestudypublishedintheJulyissueofNeurologyisthefirsttoprovidebiologicalevidencetosupportaconceptcalledthe"reserve"hypothesisaccordingtotheresearchers.Inrecentyearsinvestigatorshavedevelopedtheideathatpeoplewhoaremoreeducatedhavegreatercognitivereservestodrawuponasthebrainages;inessencetheyhavemorebraintissuetospare. 48Examiningbrainscansof320healthymenandwomenaged66to90researchersfoundthatforeachyearofeducationthesubjectshadtherewasgreatershrinkageoftheouterlayerofthebrainknownasthecortex.Yetontestsofcognitionandmemoryallparticipantsscoredintherangeindicatingnormal. "Everyonehassomedegreeofbrainshrinkage."Coffeysaid."Peopleloseonaverage2.5percentperdecadestartinginadulthood." Thereishowevera"remarkablerange"ofshrinkageamongpeoplewhoshownosignsofmentaldeclineCoffeynoted.Overallhealthhesaidaccountsforsomedifferencesinbrainsize.Alcoholordruguseaswellasmedicalconditionssuchasdiabetesandhighbloodpressurecontributetobraintissuelossthroughoutadulthood. IntheabsenceofsuchmedicalconditionsCoffeysaideducationlevelhelpsexplaintherangeofbrainshrinkageexhibitedamongthementally-fitelderly.Themore-educatedcanwithstandgreaterloss. 49Coffeyandcolleaguesgaugedshrinkageofthecortexbymeasuringthecerebrospinalfluid脑脊液surroundingthebrain.Thegreatertheamountoffluidthegreaterthecortical脑皮层的shrinkage. Controllingforthehealthfactorsthatcontributetobraininjurytheresearchersfoundthateducationwasrelatedtotheseverityofbrainshrinkage.Foreachyearofeducationfromfirstgradeonsubjectshadanaverageof1.77milliliters11morecerebrospinalfluidaroundthebrain.Justhoweducationmightaffectbraincellsisunknown.50Intheirreporttheresearchersspeculatedthatinpeoplewithmoreeducationcertainbrainstructuresdeeperthanthecortexmaystayintacttocompensateforcorticalshrinkage. 47Howeverheexplainedthefindingsuggeststhateducationallowspeopletowithstandmorebraintissuelossbeforetheirmentalfunctioningbeginstobreakdown.
设某计算机系统有一块CPU一台输入设备一台打印机现有两个进程同时进入就绪状态且进程A先得到CPU运行进程B后运行进程A的运行轨迹为计算50毫秒打印信息100毫秒再计算50毫秒打印信息100毫秒结束进程B的运行轨迹为计算50毫秒输入数据80毫秒再计算100毫秒结束试说明进程A运行时有无等待现象若有在什么时候发生等待现象
某一个操作系统具有分时兼批处理的功能设计一个合理的队列调度策略使得分时作业响应快批作业也能及时得到处理
系统有同类资源10个进程P1P2和P3需要该类资源的最大数量分别为867它们使用资源的次序和数量如表2-11所示试给出采用银行家算法分配资源时进行第5次分配后各进程的状态及各进程占用资源的情况
试从物理概念上来说明记录型信号量和wait与signal操作
设有一个公有信箱和若干个私有信箱公有信箱可由所有人在其中存/取信件而私有信箱只能由特定拥有者使用在其中存/取信件显然信箱是有容量限制的选定一种信号量机制设计出相应的同步机制管理程序
某系统有R1R2和R3共3种资源在T0时刻P1P2P3和P4这4个进程对资源的占有和需求情况如表2-10所示此刻系统可用资源向量为212问题如果此时P1和P2均发出资源请求向量Request101为了保持系统安全性应该如何分配资源给这两个进程说明所采用的原因
进程和线程的主要区别是什么
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