What an operating system does when it runs two or more programs simultaneously. From the point of view of the user, the programs appear to be executing at the same time, but from the operating system’s point of view, one of two things might be happening:
There are two basic types of multiprocessing on machines that run versions of the Windows operating system:
Windows NT supports symmetric multiprocessing (SMP) on multiprocessor machines, whereby the Windows NT kernel lets processors share memory and assign ready threads to the next available processor.
This SMP support ensures that no processor is ever idle or running a low-priority thread when a high-priority thread is waiting. Windows NT also supports soft affinity, whereby a thread tries to run on the same processor it last ran on, all things being equal. You can also use Task Manager to assign a specific process to a processor.