Tets

Topics: Interrupt, Central processing unit, X86 / Pages: 10 (2487 words) / Published: Apr 17th, 2013
Wolmer’s Trust High School for Girls

CAPE COMPUTER SCIENCE

Grade 11 Teacher: Mrs. McCallum-Rodney

Operating System Function – PROCESS MANAGEMENT

Introduction to Process Management

• A process does nothing unless its instructions are executed by the CPU.

• A process can be thought of as a program in execution.

• A process needs certain resources, including CPU time, memory, files and I/O devices, to accomplish its tasks. These resources are either given to the process when it is created, or allocated to it while it is running.

• In addition to physical and logical resources that a process obtains when it is created, some initialization data (input) may be passed along. For example, a process whose function is to display the status of a file on the screen of a terminal, will be given as an input the name of the file, and will execute the appropriate instructions and system calls to obtain the desired information and display it on the terminal.

• When the process terminates, the operating system will reclaim any reusable resources.

• A program by itself is not a process; a program is a passive entity, such as the contents of a file stored on a disk. A process is an active entity, with a program counter specifying the next instruction to be executed.

• The execution of a process must be executed sequentially.

• The CPU executes one instruction of the process after another, until the process is complete. At most one instruction is executed on behalf of the process. Therefore, although two processes may be associated with the same program, they are nevertheless considered two separate execution sequences. It is common to have a program that spawns many processes as it runs.

Note: A process is the unit of work in a system.

• Such a system consists of a collection of processes, some of which are operating-system processes (those that execute system codes) and the rest of which are user processes (those that

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