Multitasking Operating System
A Multitasking Operating System is an operating system where multiple tasks (also known as computer processes) are performed during the same period of time they are executed concurrently.
- Example(s):
- a Unix-Like OS.
- See: Real-Time Computing, Task (Computers), Computer Process, Concurrent Computing, Parallel Computing, Scheduling (Computing), Context Switch, Multiprocessor, Multicore, Multiprogramming.
References
2015
- (Wikipedia, 2015) ⇒ http://en.wikipedia.org/wiki/computer_multitasking Retrieved:2015-2-16.
- In computing, 'multitasking is a method where multiple tasks (also known as computer processes) are performed during the same period of time they are executed concurrently (in overlapping time periods, new tasks starting before others have ended) instead of sequentially (one completing before the next starts). The tasks share common processing resources, such as Central processing units (CPU) and the main memory.
Multitasking does not necessarily mean that multiple tasks are executing at exactly the same instant. In other words, multitasking does not imply parallel computing, but it does mean that more than one task can be part-way through execution at the same time, and more than one task is advancing over a given period of time.
In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is actively executing instructions for that task. Multitasking solves the problem by scheduling which task may be the one running at any given time, and when another waiting task gets a turn. The act of reassigning a CPU from one task to another one is called a context switch. When context switches occur frequently enough, the illusion of parallelism is achieved.
Even on multiprocessor or multicore, where more than one task can be executed at a given instant (one per CPU or core), multitasking allows many more tasks to be run than there are CPUs. The term multitasking has become an international term, as the same word is used in many other languages such as German, Italian, Dutch, Danish and Norwegian.
Operating systems may adopt one of many different scheduling strategies, which generally fall into the following categories:* In multiprogramming systems, the running task keeps running until it performs an operation that requires waiting for an external event (e.g. reading from a tape) or until the computer's scheduler forcibly swaps the running task out of the CPU. Multiprogramming systems are designed to maximize CPU usage.
- In time-sharing systems, the running task is required to relinquish the CPU, either voluntarily or by an external event such as a hardware interrupt. Time sharing systems are designed to allow several programs to execute apparently simultaneously.
- In real-time systems, some waiting tasks are guaranteed to be given the CPU when an external event occurs. Real time systems are designed to control mechanical devices such as industrial robots, which require timely processing.
- In computing, 'multitasking is a method where multiple tasks (also known as computer processes) are performed during the same period of time they are executed concurrently (in overlapping time periods, new tasks starting before others have ended) instead of sequentially (one completing before the next starts). The tasks share common processing resources, such as Central processing units (CPU) and the main memory.