New Vocabulary

Process state                                Dispatch
Process Control Block                 Context switch
Ready queue                                Device queue
Job queue                                     Parent & child

As a process executes, it changes state.  The state of a process is defined in part by current activity of that process.  Each process may be in one of the following states:

• New:    The process is being created.
• Running:    Instruction are being executed.
• Waiting:    The process is waiting for some event to occur (such as an I/O completion or reception of signal).
• Ready:    The process is waiting to be assigned to a processor.
• Terminated:    The process has finished execution.

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It contains  many pieces of information associated with a specific process, including; process state, program counter, CPU register, CPU scheduling information, memory-management information, accounting information, I/O status information

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The processes that are residing in main memory and are ready and waiting to execute are kept on a list.  This queue is generally stored as a linked list.  It will contain pointers to the first and last PCBs in the list.

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This queue consists of all processes in the system.

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It is the module that gives control of the CPU to the process selected by the short-term scheduler.  This function involves:

- Switching context, Switching to user mode, Jumping to the proper location in the user program to restart that program.

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Switching the CPU to another process requires saving the state of the old process and loading the saved state for the new process.  This task is known as a context switch.

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A list of processes waiting for a particular I/O device is called a device queue.

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The creating process is called a parent process, whereas the new processes are called the children of that process.

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Any commends or questions

Email to: dtnguyen@neiu.edu

Chapter 4 - New Vocabulary Page
Created by Doan Nguyen
Last Update March 26, 1999