L2-Process_Concept

L2-Process_Concept - Process Concepts CSIS0230A Lecture Two Process abstraction Process states and transitions Process Descriptor Process Control

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Process Concepts CSIS0230A Lecture Two Process abstraction Process states and transitions Process Descriptor Process Control Block Process control Interprocess communication
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Recommended Reading Chapter 3 of Operating Systems, 3 rd edition by Deitel et. al CSIS0230A Principles of Operating Systems 2
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References Chapter 3 of Operating Systems, 3 rd edition by Deitel et. al Chapter 3 of Operating System Principles, 7 th edition by Silberschatz et. al Chapter 3 of Operating Systems: Internal and Design Principles, 6 th edition by W. Stallings Chapter 5 of IA-32 Intel® Architecture Software Developer’s Manual, Volume 3A: System Programming Guide, Part 1 CSIS0230A Principles of Operating Systems 3
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Processes and Programs What is a 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 resources CSIS0230A Principles of Operating Systems 4
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Process an abstraction How to abstract a process? What ought to be kept in order to abstract an executing program? CSIS0230A Principles of Operating Systems 5 Memory space Resources in use Execution state Program code Data Register set Current process state I/O in use Physical memory
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Process Address Space A process has its own address space consisting of: Text region Stores the code that the processor executes Data region Stores global and static variables Heap Dynamically allocated memory Stack region Stores instructions and local variables for active procedure calls CSIS0230A Principles of Operating Systems 6
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Process Process States During its lifetime, a process moves through a series of discrete process states Process state - an indicator of the nature of the current activity in a process new: The process is being created running: The process is executing on a processor blocked: The process is waiting for some event (I/O) to happen before it can proceed ready: The process could execute on a processor and is waiting to be assigned to a processor terminated: The process has finished execution CSIS0230A Principles of Operating Systems 7
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When the time quantum expires, it transitions from running to ready Life Cycle of a Process CSIS0230A Principles of Operating Systems 8 Terminated Admitted Exit New Ready Running Blocked Dispatching Preemption I/O or event completion Resource or wait request When a process is dispatched to be executed by the CPU, it transitions from ready to running When a process blocks waiting for resources (e.g. I/O), it transitions from running to blocked When the waiting event occurs, it transitions from blocked to ready OS maintains a ready list and a blocked list to store references to processes not running
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CSIS0230A Principles of Operating Systems
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This note was uploaded on 12/01/2010 for the course CS 2342 taught by Professor Dr during the Spring '10 term at HKU.

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L2-Process_Concept - Process Concepts CSIS0230A Lecture Two Process abstraction Process states and transitions Process Descriptor Process Control

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