preemptive multitasking

Preemptive multitasking is task in which a computer operating system uses some criteria to decide how long to allocate to any one task before giving another task a turn to use the operating system. The act of taking control of the operating system from one task and giving it to another task is called preempting. A common criterion for preempting is simply elapsed time (this kind of system is sometimes called time sharing or time slicing). In some operating systems, some applications can be given higher priority than other applications, giving the higher priority programs control as soon as they are initiated and perhaps longer time slices.