pre-emptive multitasking

operating system, parallel A type of multitasking where

the scheduler can interrupt and suspend ("swap out") the

currently running task in order to start or continue running

("swap in") another task. The tasks under pre-emptive

multitasking can be written as though they were the only task

and the scheduler decides when to swap them. The scheduler

must ensure that when swapping tasks, sufficient state is

saved and restored that tasks do not interfere.

The length of time for which a process runs is known as its

"time slice" and may depend on the task's priority or its

use of resources such as memory and I/O.

OS/2, Unix and the Amiga use pre-emptive multitasking.

This contrasts with cooperative multitasking where each task

must include calls to allow it to be descheduled

periodically.

(1995-03-20)