OCR Computing A-Level Revision

Components of a Computer System

Key Terms (1.1.a)

Hardware - the physical components which make up the computer.
Software - the instructions and code that tells the computer what to do. There are two types of software, applications software and system software.
Input Device - a type of peripheral that can accept data, decode it, and send it as electrical pulses to the computer. For example: keyboards, mice, digital cameras, and microphones.
Storage Device - a memory device used to store operating systems, programs, and user data. Storage devices are non-volatile - they do not lose their data when they are unpowered. See 1.4.3 Memory and Storage.
Output Device - a device that turns computer signals into a human-readable form, like a screen, printer, or speaker.

Input, Storage, and Output Devices (1.1.b)

The purpose of an input device is to bring data into a computer for processing. For example, using a microphone to input sound for processing into an MP3, which will then be sold on the internet, or a digital camera to input images to be processed by graphics software, before being included in a word processing package.

An output device is used to turn the processed data into something useful, for example, turning a purchased MP3 into sound using a set of speakers, or turning a document in a word processing package into a physical document using a printer. Storage devices save user data, programs, and applications for later use.

There are all sorts of input devices, not just keyboards and mice. For example, a pressure sensor is an input device which could be used to detect if somebody had stood on a pressure sensitive plate, or a temperature sensor to detect if the temperature in a room goes outside of acceptable limits.

System Software and Application Software (1.1.c)

System software controls the hardware of the computer, such as providing a user interface, managing memory, and providing services such as printing and file handling. Application packages, on the other hand, are programs that allow to user to complete specific tasks, for example graphic design or word processor packages.