ProcessDescAndControlJan15

- Chapter 3 The Process Model Page 1 Topics Review system call Introduce the process model To introduce the notion of a process a program in

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Page 1 The Process Model Chapter 3
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Page 2 Topics Review system call Introduce the process model To introduce the notion of a process -- a program  in execution, which forms the basis of all  computation To describe the various features of processes,  including scheduling, creation and termination,  and communication To describe communication in client-server  systems
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Page 3 A View of Operating System  Services
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Page 4 Traditional UNIX System  Structure
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Page 5 System Call Implementation Typically, a number associated with each system call System-call interface maintains a table indexed according to  these numbers The system call interface invokes intended system call in OS  kernel and returns status of the system call and any return  values The caller need know nothing about how the system call is  implemented Just needs to obey API and understand what OS will do as a  result call Most details of  OS interface hidden from programmer by  API   Managed by run-time support library (set of functions built  into libraries included with compiler)
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Page 6 API – System Call – OS  Relationship
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Page 7 Standard C Library Example C program invoking printf() library call, which calls  write() system call
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Page 8 Processes The Process Model Multiprogramming of four programs Conceptual model of 4 independent, sequential  processes Only one program active at any instant
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Page 9 What is a process? A process is simply a program in execution: an instance of a program  execution. Unit of work individually schedulable by an operating system. A process includes: program counter  stack data section OS keeps track of all the active processes and allocates system  resources to them according to policies devised to meet design  performance objectives. To meet process requirements OS must maintain many data  structures efficiently. The process abstraction is a fundamental OS means for management  of concurrent program execution. Example: instances of process  co- existing.
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Page 10 Process in Memory
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Page 11 Process creation Four common events that lead to a process  creation are: 1) When a new batch-job is presented for  execution. 2) When an interactive user logs in / system  initialization. 3) When OS needs to perform an operation 
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This document was uploaded on 10/15/2010.

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- Chapter 3 The Process Model Page 1 Topics Review system call Introduce the process model To introduce the notion of a process a program in

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