Cambridge O Level Computer Science · Syllabus 2210 · Software
Multitasking
What is Multitasking?
Multitasking is the operating-system function that allows more than one process to make progress at the same time by allocating processor time to each in turn, saving and restoring process state and switching between them rapidly so that they appear to run simultaneously.
This definition is part of the Software chapter in Cambridge O Level Computer Science.
Multitasking in context
An operating system is system software that manages the computer's hardware and resources and provides a platform on which application software can run. It is not one job but nine, carried out at the same time and constantly interacting: managing files, handling interrupts, providing an interface, managing peripherals and drivers, managing memory, managing multitasking, providing a platform for running applications, providing system security, and managing user accounts. Every one of those functions exists because a shared machine with limited resources needs someone to be in charge of them.
Common mistakes with Multitasking
- 5. Describing multitasking as literal simultaneity. Why it fails On a single processor core, only one instruction is executed at a time. The operating system allocates processor time to each process in turn and switches between them so quickly that they appear to run at the same time. Fix Use the words "allocates processor time", "saves and restores state" and "appears simultaneous". See OS function 6.
- M7. "Multitasking means a single core executes everything simultaneously." Why it fails A single processor core executes one instruction at a time. Describing genuine simultaneity removes the mechanism the question is actually testing — the switching. Corrected model The operating system allocates processor time to each process in turn, saves and restores state at each switch, and switches so rapidly that the processes appear to run at the same time. Exam-safe sentence "The operating system allocates processor time to each process in turn, saving and restoring their states, and switches between them so quickly that they appear to run simultaneously." Show the retrieval checkHide the check Check: Which single word keeps a multitasking answer honest?Answer: "Appear". The processes appear to run at the same time; a single core executes one instruction at a time.