Microsoft® Windows® XP Unleashed

Multitasking and Symmetric Multiprocessing

MS-DOS and other simple operating systems allow you to run only a single program at a time. A multitasking operating system allows you to run multiple programs at the same time. Actually, in a single CPU system, only one process is active and running at any particular point in time. Processes can be further subdivided into units of instructions called threads, each performing tasks that can be run in parallel with other tasks that the application requires. Each thread is given what at first appears to be a very short amount of time in which to run, measured in milliseconds. However, keep in mind that today's fast CPUs can run millions of instructions per second, so even a small time slice granted to ...