review操作系统基础.docx

review操作系统基础.docx

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review操作系统基础

“A”representemphasesorchargecontent

“B”representfamiliarwithcontent

“C”representunderstandcontent

Chapter1:

Introduction

1.WhatisanOperatingSystem?

A

Aprogramthatactsasanintermediarybetweenauserofacomputerandthecomputerhardware.

Operatingsystemgoals:

Executeuserprogramsandmakesolvinguserproblemseasier.

Makethecomputersystemconvenienttouse.

Usethecomputerhardwareinanefficientmanner.

2.OperatingSystemDefinitionA

OSisaresourceallocator

Managesallresources

Decidesbetweenconflictingrequestsforefficientandfairresourceuse

OSisacontrolprogram

Controlsexecutionofprogramstopreventerrorsandimproperuseofthecomputer

“Everythingavendorshipswhenyouorderanoperatingsystem”isgoodapproximation

“Theoneprogramrunningatalltimesonthecomputer”isthekernel.Everythingelseiseitherasystemprogram（shipswiththeoperatingsystem）oranapplicationprogram

3.ComputerSystemStructureB

Computersystemcanbedividedintofourcomponents

Hardware–providesbasiccomputingresources

Operatingsystem：

Controlsandcoordinatesuseofhardwareamongvariousapplicationsandusers

Applicationprograms–definethewaysinwhichthesystemresourcesareusedtosolvethecomputingproblemsoftheusers

Users：

People,machines,othercomputers

4.ComputerSystemOrganizationB

Computer-systemoperation

OneormoreCPUs,devicecontrollersconnectthroughcommonbusprovidingaccesstosharedmemory

ConcurrentexecutionofCPUsanddevicescompetingformemorycycles

5.ComputerStartupA

bootstrapprogramisloadedatpower-uporreboot

TypicallystoredinROMorEPROM,generallyknownasfirmware

Initializatesallaspectsofsystem

Loadsoperatingsystemkernelandstartsexecution

6.CommonFunctionsofInterruptsA

Interrupttransferscontroltotheinterruptserviceroutinegenerally,throughtheinterruptvector,whichcontainstheaddressesofalltheserviceroutines.

Interruptarchitecturemustsavetheaddressoftheinterruptedinstruction.

Incominginterruptsaredisabledwhileanotherinterruptisbeingprocessedtopreventalostinterrupt.

Atrapisasoftware-generatedinterruptcausedeitherbyanerrororauserrequest.

Anoperatingsystemisinterruptdriven.

7.InterruptHandlingA

TheoperatingsystempreservesthestateoftheCPUbystoringregistersandtheprogramcounter.

Determineswhichtypeofinterrupthasoccurred:

polling

vectoredinterruptsystem

Separatesegmentsofcodedeterminewhatactionshouldbetakenforeachtypeofinterrupt

8.StorageHierarchyB

Storagesystemsorganizedinhierarchy.

Speed

Cost

Volatility

Caching–copyinginformationintofasterstoragesystem;mainmemorycanbeviewedasalastcacheforsecondarystorage.

9.DirectMemoryAccessStructureB

Usedforhigh-speedI/Odevicesabletotransmitinformationatclosetomemoryspeeds.

DevicecontrollertransfersblocksofdatafrombufferstoragedirectlytomainmemorywithoutCPUintervention.

Onlyoneinterruptisgeneratedperblock,ratherthantheoneinterruptperbyte.

10.OperatingSystemStructure（thedifferencebetweenmultiprogrammingandtimesharingmethods）B

Multiprogrammingneededforefficiency

SingleusercannotkeepCPUandI/Odevicesbusyatalltimes

Multiprogrammingorganizesjobs（codeanddata）soCPUalwayshasonetoexecute

Asubsetoftotaljobsinsystemiskeptinmemory

Onejobselectedandrunviajobscheduling

Whenithastowait（forI/Oforexample）,OSswitchestoanotherjob

Timesharing（multitasking）islogicalextensioninwhichCPUswitchesjobssofrequentlythatuserscaninteractwitheachjobwhileitisrunning,creatinginteractivecomputing

Responsetimeshouldbe<1second

Eachuserhasatleastoneprogramexecutinginmemoryprocess

IfseveraljobsreadytorunatthesametimeCPUscheduling

Ifprocessesdon’tfitinmemory,swappingmovestheminandouttorun

Virtualmemoryallowsexecutionofprocessesnotcompletelyinmemory

11.Operating-SystemOperationsA

Interruptdrivenbyhardware

Softwareerrororrequestcreatesexceptionortrap

Divisionbyzero,requestforoperatingsystemservice

Otherprocessproblemsincludeinfiniteloop,processesmodifyingeachotherortheoperatingsystem

Dual-modeoperationallowsOStoprotectitselfandothersystemcomponents

Usermodeandkernelmode

Modebitprovidedbyhardware

Providesabilitytodistinguishwhensystemisrunningusercodeorkernelcode

Someinstructionsdesignatedasprivileged,onlyexecutableinkernelmode

Systemcallchangesmodetokernel,returnfromcallresetsittouser

12.TransitionfromUsertoKernelModeA

Timertopreventinfiniteloop/processhoggingresources

Setinterruptafterspecificperiod

Operatingsystemdecrementscounter

Whencounterzerogenerateaninterrupt

Setupbeforeschedulingprocesstoregaincontrolorterminateprogramthatexceedsallottedtime

Chapter2:

Operating-SystemStructures

1.OperatingSystemServicesA

Onesetofoperating-systemservicesprovidesfunctionsthatarehelpfultotheuser:

Userinterface-Almostalloperatingsystemshaveauserinterface（UI）

VariesbetweenCommand-LineInterface（CLI）,GraphicsUserInterface（GUI）,andBatch

Functionsthatarehelpfultotheuserandtoprocesses:

Programexecution-Loadaprogramintomemoryandrunit

File-systemmanipulation-Move,copy,anddeletefiles,createdirectories,changepermissions,etc.

Communications–Processesmayexchangeinformation,onthesamecomputerorbetweencomputersoveranetwork

Communicationsmaybeviasharedmemoryorthroughmessagepassing（packetsmovedbytheOS）

AnothersetofOSfunctionsexistsforensuringtheefficientoperationofthesystemitselfviaresourcesharing

Resourceallocation-Whenmultipleusersormultiplejobsrunningconcurrently,resourcesmustbeallocatedtoeachofthem

Manytypesofresources-Some（suchasCPUcycles,mainmemory,andfilestorage）mayhavespecialallocationcode,others（suchasI/Odevices）mayhavegeneralrequestandreleasecode.

Accounting-Tokeeptrackofwhichusersusehowmuchandwhatkindsofcomputerresources

Protectionandsecurity-Theownersofinformationstoredinamultiuserornetworkedcomputersystemmaywanttocontroluseofthatinformation,concurrentprocessesshouldnotinterferewitheachother

2.UserOperatingSystemInterface-CLIA

CLIallowsdirectcommandentry

Sometimesimplementedinkernel,sometimesbysystemsprogram

Sometimesmultipleflavorsimplemented–shells

3.UserOperatingSystemInterface-GUIA

User-friendlydesktopinterface

Iconsrepresentfiles,programs,actions,etc.

Variousmousebuttonsoverobjectsintheinterfacecausevariousactions

4.SystemCallsA

ProgramminginterfacetotheservicesprovidedbytheOS:

Processcontrol,filemanagement,devicemanagement,informationservices,communications

Typicallywritteninahigh-levellanguage（CorC++）

Mostlyaccessedbyprogramsviaahigh-levelApplicationProgramInterface（API）ratherthandirectsystemcalluse

5.SystemCallImplementationA

Typicallyusingsoftwareinterrupt（trap）

Registerissettoanumberassociatedwiththesystemcall

System-callinterfacemaintainsatableindexedaccordingtothesenumbers（cf.interruptvector）

ThesystemcallinterfaceinvokesintendedsystemcallinOSkernelandreturnsstatusofthesystemcallandanyreturnvalues

6.OperatingSystemDesignandImplementationA

Importantprincipletoseparate

Policy:

Whatwillbedone?

Mechanism:

Howtodoit?

Mechanismsdeterminehowtodosomething,policiesdecidewhatwillbedone

Theseparationofpolicyfrommechanismisaveryimportantprinciple,itallowsmaximumflexibilityifpolicydecisionsaretobechangedlater

7.VirtualMachinesB

Avirtualmachinetakesthelayeredapproachtoitslogicalconclusion

Ittreatshardwareandtheoperatingsystemkernelasthoughtheywereallhardware

Avirtualmachineprovidesaninterfaceidenticaltotheunderlyingbarehardware

8.OperatingSystemGenerationC

Operatingsystemsaredesignedtorunonanyofaclassofmachines;thesystemmustbeconfiguredforeachspecificcomputersite

SYSGENprogramobtainsinformationconcerningthespecificconfigurationofthehardwaresystem

Booting–startingacomputerbyloadingthekernel

Bootstrapprogram–codestoredinROMthatisabletolocatethekernel,loaditintomemory,andstartitsexecution

Chapter3:

Processes

1.ProcessConceptA

Anoperatingsystemexecutesavarietyofprograms:

Batchsystem–jobs

Time-sharedsystems–userprogramsortasks

Textbookusesthetermsjobandprocessalmostinterchangeably

Process–aprograminexecution;processexecutionmustprogressinsequentialfashion

Aprocessincludes:

programcounter

stack

datasection

2.ProcessStateA

Asaprocessexecutes,itchangesstate

new:

Theprocessisbeingcreated

running:

Instructionsarebeingexecuted

waiting:

Theprocessiswaitingforsomeeventtooccur

ready:

Theprocessiswaitingtobeassignedtoaprocessor

terminated:

Theprocesshasfinishedexecution

DiagramofProcessStateA

3.ProcessControlBlock（PCB）A

Informationassociatedwitheachprocess

Processstate

Programcounter

CPUregisters

CPUschedulinginformation

Memory-managementinformation

Accountinginformation

I/Ostatusinformation

ProcessControlBlock（PCB）

4.ProcessSchedulingQueuesA

Jobqu