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ch01-introduction.pdf

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Introduction OperatingSystemConcepts–8thEdition,ModifiedbyM.Rebaudengo-2012Silberschatz,GalvinandGagne©2009 WhatisanOperatingSystem? „Aprogramthatactsasanintermediarybetweena userofacomputerandthecomputerhardware „Operatingsystemgoals: zExecuteuserprogramsandmakesolvinguser problemseasier zMakethecomputersystemconvenienttouse zUsethecomputerhardwareinanefficientmanner OperatingSystemConcepts–8thEdition1.2Silberschatz,GalvinandGagne©2009 ComputerSystemStructure „Computersystemcanbedividedintofourcomponents zHardware–providesbasiccomputingresources CPU,memory,I/Odevices zOperatingsystem Controlsandcoordinatesuseofhardwareamongvarious applicationsandusers zApplicationprograms–definethewaysinwhichthesystem resourcesareusedtosolvethecomputingproblemsofthe users Wordprocessors,compilers,webbrowsers,database systems,videogames zUsers People,machines,othercomputers OperatingSystemConcepts–8thEdition1.3Silberschatz,GalvinandGagne©2009 FourComponentsofaComputerSystem OperatingSystemConcepts–8thEdition1.4Silberschatz,GalvinandGagne©2009 OperatingSystemDefinition „Fromthecomputer'spointofview,theoperatingsystemistheprogram mostinvolvedwiththehardware „OSisaresourceallocator zManagesallresources(CPUtime,memoryspace,file-storagespace, I/Odevices,etc.) zresourceallocationisimportantwheremanyusersaccessthesame computer zDecidesbetweenconflictingrequestsforefficientandfairresourceuse „OSisacontrolprogram zControlsexecutionofprogramstopreventerrorsandimproperuseof thecomputer zItisespeciallyconcernedwiththeoperationandcontrolofI/Odevices. OperatingSystemConcepts–8thEdition1.5Silberschatz,GalvinandGagne©2009 OperatingSystemDefinition(Cont.) „Nouniversallyaccepteddefinitionofwhatispartoftheoperatingsystem „Theoneprogramrunningatalltimesonthecomputer zusuallycalledkernel „Everythingelseiseitherasystemprogram(shippedwiththeoperating system)oranapplicationprogram. OperatingSystemConcepts–8thEdition1.6Silberschatz,GalvinandGagne©2009 ComputerSystemOrganization