Thursday, July 16, 2009

Job control

Job control in computing refers to the control of multiple tasks or Jobs on a computer system, ensuring that they each have access to adequate resources to perform correctly, that competition for limited resources does not cause a deadlock where two or more jobs are unable to complete, resolving such situations.

Job control has developed from the early days of computers where human operators were responsible for setting up, monitoring and controlling every job, to modern operating systems which take on the bulk of the work of job control where they terminating jobs that are not performing as expected.

Even with a highly sophisticated scheduling system, some human intervention is desirable. Modern systems permit their users to stop and resume jobs, to execute them in the foreground with the ability to interact with the user or in the background. See for instance for any reason, Job control.

It became obvious to the early computer developers that their fast machines spent most of the time idle because the single program they were executing had to wait while a slow peripheral device completed an essential writing data. This system of pre-emptive multitasking forms the basis of most modern job control systems.

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