Multitasking is the execution of more than one task (executing process) at a time on a computer system. Multitasking should not be confused with multiple program loading, in which two or more tasks are present in random access memory (RAM) but only one task is given permission to execute at a time.
Unless a computer is equipped with two more processors, only one task can run at a time; however, an operating system (such as Linux, Windows 2000, Windows XP, and UNIX) creates the impression of simultaneous task execution by constantly switching among the various tasks that are competing for system resources. See cooperative multitasking, preemptive multitasking, protected memory, and task.