1. Introduction.pptx - Introduction Chapter #1 Nausheen...

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IntroductionCourse Instructor: Nausheen ShoaibChapter#1
Marks Distribution?Mid1: 15%?Mid2: 15%?Class activities+ Assignment+Projects: 20%?Final: 50%?Book:Opertaing System Concepts byAbraham Silberschatz 10thEdition
What is an Operating System??A program that acts as an intermediarybetween a user of a computer and thecomputer hardware
Computer System Structure?Computer system can be divided intofour components:Hardware – provides basic computingresourcesOperating systemApplication programsUsers
Four Components of a Computer System
Operating System Definition?OS is aresource allocatorManages all resourcesDecides between conflicting requests for efficientand fair resource use?OS is acontrol programControls execution of programs to prevent errors andimproper use of the computer“The one program running at all times on thecomputer” is thekernel.
Computer Startup?bootstrap programis loaded at power-upor rebootTypically stored in ROM or EPROM, generallyknown asfirmwareInitializes all aspects of systemLoads operating system kernel and startsexecution
Computer System Organization?Computer-system operationOne or more CPUs, device controllers connectthrough common bus providing access toshared memoryConcurrent execution of CPUs and devicescompeting for memory cycles
Computer-System Operation?I/O devices and the CPU can execute concurrently?Each device controller is in charge of a particulardevice type?Each device controller has a local buffer?CPU moves data from/to main memory to/fromlocal buffers?I/O is from the device to local buffer of controller?Device controller informs CPU that it has finishedits operation by causing aninterrupt
Common Functions of InterruptsInterrupt transfers control to the interruptservice routine generally, through theinterruptvector, which contains theaddresses of all the service routinesInterrupt architecture must save the addressof the interrupted instructionAtraporexceptionis a software-generated interrupt caused either by anerror or a user requestAn operating system isinterrupt driven
Interrupt Handling?The operating system preserves the state ofthe CPU by storing registers and the programcounter?Determines which type of interrupt hasoccurred:pollingvectoredinterrupt system?

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