計(jì)算機(jī)科學(xué)-hw操作系統(tǒng)概念課后習(xí)題答案-ch10

ImportSettings:

BaseSettings:BrownstoneDefault

HighestAnswerLetter:D

MultipleKeywordsinSameParagraph:No

Chapter:Chapter10

MultipleChoice

L

AxA(n)fileisasequenceoffunctions,

/)

Btext

c\source

z)

DXobject

XIexecutable

Ar

:B

Feedback:10.1

Difficulty:Easy

z

A(n)fileisasequenceofbytesorganizedintoblocksunderstandablebythesystem's

Hn

AV不

-)

Btext

csource

Dxobject

7?executable

Ar

:C

Feedback:10.1

Difficulty:Easy

3.

A\A(n)fileisaseriesofcodesectionsthattheloadercanbringintomemoryandexecute,

7?

B\text

/!

c\source

/!

D\object

ZJexecutable

Ans:D

Feedback:10.1

Difficulty:Easy

4.Inanenvironmentwhereseveralprocessesmayopenthesamefileatthesametime,.

A)theoperatingsystemtypicallyusesonlyoneinternaltabletokeeptrackofopenfiles

B)theoperatingsystemtypicallyusestwointernaltablescalledthesystem-wideandper-disk

tablestokeeptrackofopenfiles

C)theoperatingsystemtypicallyusesthreeinternaltablescalledthesystem-wide,per-disk,

andper-partitiontablestokeeptrackofopenfiles

D)theoperatingsystemtypicallyusestwointernaltablescalledthesystem-wideand

per-processtablestokeeptrackofopenfiles

Ans:D

Feedback:10.1

Difficulty:Medium

5.Supposethattheoperatingsystemusestwointernaltablestokeeptrackofopenfiles.

ProcessAhastwofilesopenandprocessBhasthreefilesopen.Twofilesaresharedbetween

thetwoprocesses.Howmanyentriesareintheper-processtableofprocessA,theper-process

tableofprocessB,andthesystem-widetables,respectively?

A)5,5,5

B)2,3,3

C)2,3,5

D)2,3,1

Ans:B

Feedback:10.1

Difficulty:Difficult

6

Asharedlock.

A\

l

zbehaveslikeawriterlock

B\

J

/ensuresthatafilecanhaveonlyasingleconcurrentsharedlock

c\

7behaveslikeareaderlock

D\

l

zwillpreventallotherprocessesfromaccessingthelockedfile

A

r:C

Feedback:10.1

Difficulty:Easy

7

AXAnexclusivelock.

-Tbehaveslikeawriterlock

B\

ZJensuresthatafilecanhaveonlyasingleconcurrentsharedlock

ex

z)behaveslikeareaderlock

D

willpreventallotherprocessesfromaccessingthelockedfile

Ar

:A

Feedback:10.1

Difficulty:Easy

8.Thesimplestfileaccessmethodis.

A)sequentialaccess

B)logicalaccess

C)relativeaccess

D)directaccess

Ans:A

Feedback:10.2.1

Difficulty:Easy

9.AisusedonUNIXsystemsatthebeginningofsomefilestoroughlyindicatethetype

ofthefile.

A)fileextension

B)creatorname

C)hint

D)magicnumber

Ans:D

Feedback:10.1.3

Difficulty:Medium

lAoxWhichofthefollowingistrueofthedirect-accessmethod?

zl

BItisthemostcommonmodeofaccess.

J\

cZItallowsprogramstoreadandwriterecordsinnoparticularorder.

>\

D/Filesaremadeupofvariable-lengthrecords.

Itisnotagoodmethodforaccessinglargeamountsofdataquickly.

Ans:B

Feedback:10.2.2

Difficulty:Medium

U

Whichofthefollowingistrueofthetree-structureddirectorystructure?

A)Userscannotcreatetheirownsubdirectories.

B)Userscannotacquirepermissiontoaccessthefilesofotherusers.

C)

D)Directoriescansharesubdirectoriesandfiles.

ArItisthemostcommondirectorystructure.

D

Feedback:10.3.5

Difficulty:Medium

Anacyclic-graphdirectorystructure.

1A2x

l

Bzdoesnotallowthesharingoffiles.

allowsthesharingofsubdirectoriesandfiles.

c\

)

zislesscomplicatedthanasimpletree-structureddirectorystructure.

D\

l

yislessflexiblethanasimpletree-structureddirectorystructure.

Ans:B

Feedback:10.3.6

Difficulty:Medium

13.Thepathname/home/people/os-student/chap10.txtisanexampleof

A)arelativepathname

B)anabsolutepathname

C)arelativepathnametothecurrentdirectoryof/home

D)aninvalidpathname

Ans:B

Feedback:10.3.5

Difficulty:Medium

14,TheUNIXhiesystemuseswhichofthefollowingconsistencysemantics?

AWritestoanopenfilebyauserarenotvisibleimmediatelytootherusersthathavethefile

)atthesametime.

OP

BOnceafileisclosed,thechangesmadetoitarevisibleonlyinsessionsstartinglater.

)0Usersarenotallowedsharethepointerofcurrentlocationintothefile.

D)Writestoanopenfilebyauserarevisibleimmediatelytootherusersthathavethefileopen

atthesametime.

Ans:D

Feedback:10.5.3

Difficulty:Difficult

15A\Whichofthefollowingisakeypropertyofanimmutablefile?

zl

B\Thefilenamemaynotbereused.

/1

c\Thecontentsofthefilemaybealtered.

z)

D\Itisdifficulttoimplementinadistributedsystem.

/—Thefilenamemaybereused.

An

A

Feedback:10.5.3

Difficulty:Medium

16.Whichofthefollowingisnotconsideredaclassificationofusersinconnectionwitheach

file?

A)owner

B)currentuser

C)group

D)universe

Ans:B

Feedback:10.6.2

Difficulty:Easy

17.isasecure,distributednamingmechanism.

A)Lightweightdirectory-accessprotocol(LDAP)

B)Domainnamesystem(DNS)

C)Commoninternetfilesystem(CIFS)

D)Networkinformationservice(NIS)

Ans:A

Feedback:10.5

Difficulty:Medium

18.app.exeisanexampleofa(n).

A)batchfile

B)objectfile

C)executablefile

D)textfile

Ans:C

Feedback:10.1.3

Difficulty:Easy

19.Amountpointis.

A)arootofthefilesystem

B)alocationofasharedfilesystem

C)onlyappropriateforsharedfilesystems

D)thelocationwithinthefilestructurewherethefilesystemistobeattached.

Ans:D

Feedback:10.4

Difficulty:Medium

20.is/arenotconsideredadifficultywhenconsideringfilesharing.

A)Reliability

B)Multipleusers

C)Consistencysemantics

D)Remoteaccess

Ans:A

Feedback:10.5

Difficulty:Medium

21.Whichofthefollowingisnotconsideredafileattribute?

A)Name

B)Size

C)Resolution

D)Protection

Ans:C

Feedback:10.1.1

Difficulty:Easy

22.Thepathnameos-student/src/vm.cisanexampleof

A)arelativepathname

B)anabsolutepathname

C)arelativepathnametothecurrentdirectoryof/0S-Student

D)aninvalidpathname

Ans:A

Feedback:10.3.5

Difficulty:Medium

23.Whichofthefollowingstatementsregardingtheclient-servermodelistrue?

A)Aremotefilesystemmaybemounted.

B)Theclient-serverrelationshipisnotverycommonwithnetworkedmachines.

C)Aclientmayonlyuseasingleserver.

D)Theclientandserveragreeonwhichresourceswillbemadeavailablebyservers.

Ans:A

Feedback:10.5.2

Difficulty:Medium

Essay

24.Ifyouwerecreatinganoperatingsystemtohandlefiles,whatwouldbethesixbasicfile

operationsthatyoushouldimplement?

Ans:Thesixbasicfileoperationsinclude:creatingafile,writingafile,readingafile,

repositioningwithinafile,deletingafile,andtruncatingafile.Theseoperationscomprisethe

minimalsetofrequiredfileoperations.

Feedback:10.1.2

Difficulty:Medium

25.Whatarecommonattributesthatanoperatingsystemkeepstrackofandassociateswitha

file?

Ans:Theattributesofthefileare:1)thename——thehuman-readablenameofthefile,2)the

identifier-thenon-human-readabletagofthefile,3)thetypeofthefile,4)thelocationofthe

file,5)thefile'ssize(inbytes,words,orblocks),andpossiblythemaximumallowedsize,6)file

protectionthroughaccesscontrolinformation,and7)time,date,anduseridentification.

Feedback:10.1.1

Difficulty:Medium

26.Distinguishbetweenanabsolutepathnameandarelativepathname.

Ans:Anabsolutepathnamebeginsattherootandfollowsapathofdirectoriesdowntothe

specifiedfile,givingthedirectorynamesonthepath.Anexampleofanabsolutepathnameis

/home/osc/chap10/file.txt.Arelativepathnamedefinesapathfromthecurrentdirectory.Ifthe

currentdirectoryis/home/osc/,thentherelativepathnameof

chaplO/file.txtreferstothesamefileasintheexampleoftheabsolutepathname.

Feedback:10.3.5

Difficulty:Medium

27.Whatisthedifferencebetweenanoperatingsystemthatimplementsmandatorylocking

andonethatimplementsadvisoryfilelocking?

Ans:Mandatorylockingrequiresthattheoperatingsystemnotallowaccesstoanyfilethatis

locked,untilitisreleased,eveniftheprogramdoesnotexplicitlyaskforalockonthefile.An

advisoryfilelockingschemewillnotpreventaccesstoalockedfile,anditisuptothe

programmertoensurethatlocksareappropriatelyacquiredandreleased.

Feedback:10.1.2

Difficulty:Medium

28.Whataretheadvantagesofusingfileextensions?

Ans:Fileextensionsallowtheuserofthecomputersystemtoquicklyknowthetypeofafile

bylookingatthefile'sextension.Theoperatingsystemcanusetheextensiontodeterminehow

tohandleaparticularfile.

Feedback:10.1.3

Difficulty:Medium

29.Brieflyexplainthefunctionalityofextendedfileattributes.

Ans:Fileattributesaregeneralvaluesrepresentingthenameofafile,itsowner,size,and

permissions(tonameafew.)Extendedfileattributesrefertoadditionalfileattributessuchas

characterencoding,securityfeatures,andapplicationassociatedwithopeningthefile.

Feedback:10.1.4

Difficulty:Medium

30.Whydoallfilesystemssufferfrominternalfragmentation?

Ans:Diskspaceisalwaysallocatedinfixedsizedblocks.Wheneverafileiswrittentodisk,it

usuallydoesnotfitexactlywithinanintegernumberofblockssothataportionofablockis

wastedwhenstoringthefileontothedevice.

Feedback:10.1.5

Difficulty:Medium

31.Describethreecommonmethodsforremotefile-sharing.

Ans:Thefirstimplementedmethodinvolvesmanuallytransferringfilesbetweenmachinesvia

programslikeftp.Thesecondmajormethodusesadistributedfilesystem(DFS),inwhich

remotedirectoriesarevisiblefromalocalmachine.Inthethirdmethod,abrowserisneededto

accessremotefilesontheWorldWideWeb,andseparateoperations(essentiallyawrapperfor

ftp)areusedtotransferfiles.TheDFSmethodinvolvesamuchtighterintegrationbetweenthe

machinethatisaccessingtheremotefilesandthemachineprovidingthefiles.

Feedback:10.5

Difficulty:Medium

32.DescribehowtheUNIXnetworkfilesystem(NFS)recoversfromserverfailureina

remotefilesystem?

Ans:Inthesituationwheretheservercrashesbutmustrecognizethatithasremotelymounted

exportedfilesystemsandopenedfiles,NFStakesasimpleapproach,implementingastateless

DFS.Inessence,itassumesthataclientrequestforafilereadorwritewouldnothaveoccurred

unlessthefilesystemhadbeenremotelymountedandthefilehadbeenpreviouslyopen.The

NFSprotocolcarriesalltheinformationneededtolocatetheappropriatefileandperforinthe

requestedoperation,assumingthattherequestwaslegitimate.

Feedback:10.5.2

Difficulty:Difficult

33.Whataretheadvantagesanddisadvantagesofaccesscontrollists?

Ans:Accesscontrollistshavetheadvantageofenablingcomplexaccessmethodologies.The

mainproblemwithACLsistheirlength.Constructingthelistmaybeatedioustask.Space

managementalsobecomesmorecomplicatedbecausethedirectorysizeneedstobeofvariable

size.

Feedback:10.6.2

Difficulty:Medium

True/False

34.Windowssystemsemploymandatorylocking.

Ans:True

Feedback:10.1.2

Difficulty:Medium

35.Asageneralrule,UNIXsystemsemploymandatorylocks.

Ans:False

Feedback:10.1.2

Difficulty:Medium

36.Allfilesinasingle-leveldirectorymusthaveuniquenames.

Ans:True

Feedback:10.3.3

Difficulty:Easy

37.Arelativepathnamebeginsattheroot.

Ans:False

Feed