Types of operating system

Overview

Recall questions on distributed, embedded, multi-tasking, multi-user and real time operating systems, why real time is not simply fast, the advantages and drawbacks of each type, and choosing a type for a stated scenario.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is a distributed operating system, and what is a typical use?

   Model answer

   One operating system running across several networked computers, which presents them to the user as a single machine and shares work out between them transparently. A task submitted to it may be split across many nodes without the user knowing which node did what. Typical uses are computer clusters and supercomputers, film rendering farms and large-scale web and search infrastructure, where the workload is far too big for one machine.

2. 2

   What is an embedded operating system, and what is a typical use?

   Model answer

   An operating system written for one specific device and one narrow set of tasks, held in read-only memory or flash memory rather than loaded from a disk. It is small, uses little power and memory, is highly efficient and is generally not user-upgradeable. Typical uses are a washing machine controller, a car engine management unit, a digital camera, a set-top box or a smart thermostat.

3. 3

   What is a multi-tasking operating system, and what is a typical use?

   Model answer

   An operating system that allows several programs to appear to run at the same time on one processor, by using time slicing to switch rapidly between them so that each makes progress. Its typical use is any general-purpose desktop, laptop, tablet or smartphone, where a user expects to have a browser, a music player and a word processor all running at once.

4. 4

   What is a multi-user operating system, and what is a typical use?

   Model answer

   An operating system that allows several users to use one computer at the same time, each with their own session, files and permissions, with the scheduler sharing processor time between them. It needs account management, access rights and separation of each user's data. Typical uses are a mainframe, a school or university server with many terminals, and a shared web or file server.

5. 5

   What is a real time operating system, and what is a typical use?

   Model answer

   An operating system that guarantees a response to an input within a defined maximum time, every time. It is deterministic rather than merely fast: the worst case matters more than the average. It typically uses priority-driven pre-emptive scheduling and often has redundant hardware and fail-safes. Typical uses are aircraft flight control, anti-lock braking systems, pacemakers and medical monitors, and industrial process control.

6. 6

   Explain the difference between multi-tasking and multi-user.

   Model answer

   Multi-tasking is about several programs running at once for one user; multi-user is about several users using the machine at once. They are independent ideas: a phone is multi-tasking but single-user, and a multi-user system must also be multi-tasking in order to run every user's programs, but the extra requirement it adds is accounts, permissions and separation between people rather than between programs.

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