Operating systems: need, function and purpose

Overview

Recall questions on what an operating system is and why one is needed, its functions including user interfaces, resource, file and security management, the kernel, kernel and user mode, and system versus application software.

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 an operating system?

   Model answer

   A collection of system software that manages the computer's hardware and resources and provides an environment in which application software can run. It sits between the user and applications on one side and the hardware on the other, so that programs do not have to control the hardware directly.

2. 2

   Why do we need an operating system at all? Could a program not just talk to the hardware itself?

   Model answer

   It could, but every program would then have to contain its own code for every possible processor, memory layout, disk, keyboard and printer, and two programs running at once would fight over the same hardware. The operating system provides one shared, tested layer that hides hardware differences, shares resources fairly between programs and stops one program corrupting another.

3. 3

   Describe five functions carried out by an operating system.

   Model answer

   Any five of: memory management (deciding where programs and data sit in RAM and moving pages in and out); processor scheduling (deciding which process gets the CPU and for how long); file management (organising storage into a directory structure, handling create, read, write and delete); input and output device management through device drivers; interrupt handling; providing a user interface; security and user account management, including permissions and logging in; providing utilities for maintenance.

4. 4

   What is meant by a 'user interface' as a function of the operating system, and name the two main kinds.

   Model answer

   The means by which a human interacts with the machine. A graphical user interface (GUI) uses windows, icons, menus and a pointer and is easy for a non-expert; a command line interface (CLI) takes typed text commands, which is harder to learn but faster for experienced users, uses fewer resources and can be scripted and automated.

5. 5

   Explain the term 'resource management' in the context of an operating system.

   Model answer

   The operating system controls access to limited resources - processor time, memory, storage, and input and output devices - and allocates them between competing processes. It decides who gets what and when, reclaims resources when a process finishes, and prevents two processes using the same resource in a way that would corrupt data.

6. 6

   How does an operating system provide a 'platform' for application software?

   Model answer

   It exposes a consistent set of services and interfaces (often called an application programming interface) that applications call instead of controlling hardware. A word processor asks the operating system to save a file; it does not need to know whether the storage is a hard disk drive, a solid state drive or a network share.

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