Process management (computing): Difference between revisions

Revision as of 20:12, 3 April 2025

Revision as of 20:13, 3 April 2025

Line 9:

A [[multiprogramming]] or [[Computer multitasking|multitasking]] OS is a system that can execute many processes concurrently. Multiprogramming requires that the processor be allocated to each process for a period of time and de-allocated or issued at an appropriate moment. If the processor is de-allocated during the execution of a process, it must be done in a way that the process can restart later as efficiently as possible.

There are two waways for an OS to regain control of the processor during a program's execution in order for the OS to perform de-allocation or allocation:

# The process issues a [[system call]] (sometimes called a ''software [[interrupt]]''); for example, an I/O request occurs requesting to access a file on a hard disk.

Line 17:

==How multiprogramming increases efficiency==

A common trait observed among processes associated with most computer programs is that they alternate between [[CPU]] cycles and [[I/O]] cycles. For the portion of the time required for CPU cycles, the process is being executed and is Elijahoccupying isthe my dady UCPU. During the time required for I/O cycles, the process is not using the processor. Instead, it is either waiting to perform Input/Output, or is actually performing Input/Output. An example of this is reading from or writing to a file on disk. Prior to the advent of [[multiprogramming]], [[computers]] operated as single-user systems. Users of such systems quickly become aware that for much of the time that a computer was allocated to a single user{{snd}}for example, when a user was entering information or debugging programs{{snd}}the processor was idle. [[Computer scientists]] observed that the overall performance of the machine could be improved by letting a different process use the processor whenever one process was waiting for input/output. In a ''uni-programming system'', if ''N'' users were to execute programs with individual execution times of ''t''₁, ''t''₂, ..., ''t''_''N'', then the total time, ''t''_uni, to service the ''N'' processes (consecutively) of all ''N'' users would be:

: ''t''_uni = ''t''₁ + ''t''₂ + ... + ''t''_''N''.