In computing, multitasking is a concept of performing multiple tasks (also known as processes) over a certain period of time by executing them concurrently. New tasks start and interrupt already started ones before they have reached completion, instead of executing the tasks sequentially so each started task needs to reach its end before a new one is started. As a result, a computer executes segments of multiple tasks in an interleaved manner, while the tasks share common processing resources such as central processing units (CPUs) and main memory.

Multitasking does not necessarily mean that multiple tasks are executing at exactly the same time. In other words, multitasking does not imply parallel execution, but it does mean that more than one task can be part-way through execution at the same time, and that more than one task is advancing over a given period of time. Even on multiprocessor or multicore computers, which have multiple CPUs/cores so more than one task can be executed at once (physically, one per CPU or core), multitasking allows many more tasks to be run than there are CPUs.