Nonpreemptive multitasking

A multitasking environment in which an application gives up control of the CPU to another application only at certain points, such as when it is ready to accept keyboard input. Under this method, one program performing a large number of calculations can dominate the machine and cause other programs to have limited access to the CPU. For example, if a communications program is running in the background and another application has usurped the CPU, the comm program cannot keep up with the incoming data.

Cooperation Is Necessary

Also called "cooperative multitasking," programs must be designed to yield to each other regularly in order to work effectively in this environment. Windows, prior to Windows 95, and the Mac, prior to Mac OS X, were non-preemptive multitasking operating systems. Contrast with preemptive multitasking. See multitasking.

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Nonpreemptive multitasking is a style of computer multitasking in which the operating system never initiates a context switch from a running process to another process. Such systems are either statically scheduled, most often periodic systems, or exhibit some form of cooperative multitasking, in which case the computational tasks can self-interrupt and voluntarily give control to other tasks. When non preemptive is used, a process that receive such resources can not be interrupted until it is finished

Cooperative multitasking (Preemptive algorithm) is a type of multitasking in which the process currently controlling the CPU must offer control to other processes. It is called “cooperative” because all programs must cooperate for it to work. In contrast, preemptive multitasking forces applications to share the CPU whether they want to or not.

See also

• Scheduling
• Preemption

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