Multitasking and Multiprocessing

Multitasking and multiprocessing are related concepts, but it is important to understand the distinctions between then. Multitasking is the ability to handle several different tasks at once. Multiprocessing is the ability of a computer to use more than one processor simultaneously. Typically, if multiple processors are available in a multitasking environment, then tasks can be divided among the processors. In such cases, tasks can run simultaneously. For example, if you have a large image that you need to manipulate with a filter, you can break up the image into sections, and then assign a task to process each section. If the user's computer contains multiple processors, several tasks can be executed simultaneously, reducing the overall execution time. If only one processor exists, then the tasks are preempted in turn to give each access to the processor.

Note

Because multitasking allows an operating system to attend to several different operations at the same time, these operations may appear to occur simultaneously on even a single-processor system, due to the speed of the processor.

Multiple processor support is transparent in Multiprocessing Services. If multiple processors exist, then Multiprocessing Services divides the tasks among all the available processors to maximize efficiency (a technique often called symmetric multiprocessing). If only one processor exists, then Multiprocessing Services simply schedules the available tasks with the processor to make sure that each task receives attention.

© 1999 Apple Computer, Inc. – (Last Updated 17 Nov 99)