chapter03 - Major Requirements of an Operating System...

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1 Process Description and Control Chapter 3 Major Requirements of an Operating System Interleave the execution of several processes to maximize processor utilization while providing reasonable response time Allocate resources to processes Support interprocess communication and user creation of processes Concepts Computer platform consists of a collection of hardware resources. Computer applications are developed to perform some tasks. Inefficient for applications to be written directly for a given hardware platform. Operating system provides a convenient , feature rich, secure, and consistent interface for applications to use. OS provides a uniform, abstract representation of resources that can be requested and accessed by application. Manage Execution of Applications Resources made available to multiple applications Processor is switched among multiple applications so all will appear to be progressing The processor and I/O devices can be used efficiently Process A program in execution An instance of a program running on a computer The entity that can be assigned to and executed on a processor A unit of activity characterized by the execution of a sequence of instructions, a current state, and an associated set of system instructions Process Control Block Contains the process elements (entries in the figure). It is possible to interrupt a running process and later resume execution as if the interruption had not occurred. Created and managed by the operating system Allows support for multiple processes
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2 Process States Trace : the sequence of instruction that execute for a process. The behavior of the processor can be characterized by showing how the traces of the various processes are interleaved. Dispatcher : small program that switches the processor from one process to another. Example Execution Trace of Processes Two-State Process Model Process may be in one of two states Running Not-running Not-Running Process in a Queue
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3 Process Creation Submission of a batch job User logs on Created by OS to provide a service such as printing Process creates another process: Parent process Child process Process Termination There must be a means for a process to indicate its completion A batch job should include a HALT instruction or an explicit OS service call for termination For an interactive application, the action of the user will indicate when the process is completed (e.g. log off, quitting an application) A user may quit an application. A number of error and fault conditions can lead to the termination of a process. A process may be terminated by the process that created it or when the parent process is itself terminated. Reasons for Process Termination
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This note was uploaded on 11/26/2011 for the course CSE 410 taught by Professor Bonakdarpour during the Spring '08 term at Michigan State University.

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chapter03 - Major Requirements of an Operating System...

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