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chapter_02 - Operating System Overview Chapter 2 1...

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1 Operating System Overview Chapter 2
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2 Operating System A program that controls the execution of application programs An interface between applications and hardware
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3 Operating System Objectives Convenience Makes the computer more convenient to use Efficiency Allows computer system resources to be used in an efficient manner Ability to evolve Permit effective development, testing, and introduction of new system functions without interfering with service
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4 Layers of Computer System
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5 Services Provided by the Operating System Program development Editors and debuggers Program execution Access to I/O devices Controlled access to files System access
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6 Services Provided by the Operating System Error detection and response Internal and external hardware errors Memory error Device failure Software errors Arithmetic overflow Access forbidden memory locations Operating system cannot grant request of application
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7 Services Provided by the Operating System Accounting Collect usage statistics Monitor performance Used to anticipate future enhancements Used for billing purposes
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8 Operating System Responsible for managing resources Functions same way as ordinary computer software It is program that is executed Operating system relinquishes control of the processor
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9
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10 Kernel Portion of operating system that is in main memory Contains most frequently used functions Also called the nucleus
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11 Evolution of an Operating System Hardware upgrades plus new types of hardware New services Fixes
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12 Evolution of Operating Systems Serial Processing No operating system Machines run from a console with display lights, toggle switches, input device, and printer Schedule time Setup included loading the compiler, source program, saving compiled program, and loading and linking
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13 Evolution of Operating Systems Simple Batch Systems Monitors Software that controls the sequence of events Batch jobs together Program branches back to monitor when finished
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14 Job Control Language (JCL) Special type of programming language Provides instruction to the monitor What compiler to use What data to use
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15 Hardware Features Memory protection Do not allow the memory area containing the monitor to be altered Timer Prevents a job from monopolizing the system
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16 Hardware Features Privileged instructions Certain machine level instructions can only be executed by the monitor Interrupts Early computer models did not have this capability
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17 Memory Protection User program executes in user mode Certain instructions may not be executed Monitor executes in system mode Kernel mode Privileged instructions are executed Protected areas of memory may be accessed
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18 I/O Devices Slow
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19 Uniprogramming Processor must wait for I/O instruction to complete before preceding
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20 Multiprogramming When one job needs to wait for I/O, the processor can switch to the other job
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