Information & Communication Technology 1996-2003

GCSE Revision


Computer Hardware - Input Devices

Input devices are pieces of equipment that are used to put data into a computer.


Keyboard - the commonest way to enter data into a computer. Each key is simply a switch, which when pressed, results in a digital code being sent to the computer. For example, pressing the 'A' key produces the code 01100001 representing the lower case letter 'a'. Holding down the shift key at the same time produces the code 01000001 representing the upper case letter 'A'.

Mouse - the movement of the mouse over a flat surface is mirrored by a pointer on the monitor screen. Under the mouse is a ball which rolls and turns two shafts, one for each direction - left/right & up/down. Buttons on the mouse enable selections to be made from menus, movement of objects around the screen, and painting or drawing.

Joystick - works in similar way to a mouse but usually used for playing action games. The "fire" button or trigger is used to shoot at the targets provided in the game.

Microphone - for the input of voice in place of using the keyboard and mouse. Special software is used to convert voice into text or to activate menu options. This requires fast processing and a lot of memory and will become more common as the technology improves.

Digital Camera - light received through the lens is converted to digital signals by sensors, rather than stored by chemical change on a film as in a normal camera. The resulting "photograph" can then be stored on a computer and used just like any clipart files.

Video Digitiser - enables video signals from a standard video camera or cassette recorder to be read into a computer. The video can then be stored as a file, displayed on screen and edited. Still images can be captured and printed or used as clipart.

Midi Instruments - normal musical instruments which have a midi port for input into a midi interface in the computer. The music can then be stored as a file, displayed on screen and edited ready for playback.

Scanner - like a photocopier it scans a full page with laser light but instead of printing copies, it transmits the image to the computer as digital code, which can be saved as a file. In effect, it performs the exact opposite function to a printer by converting a printed page into a computer file. There are also hand held scanners which can be wiped over the page but they have to be used very slowly and carefully for good results.

Graphics Tablet - a flat pad which you can write or draw on with a pressure sensitive stylus (like a pen). Movement across the pad is mirrored by drawing on the monitor screen. Used for art work and computer aided design.

Sensor - chemical responses to the physical environment or movement can be converted to electrical signals in the sensor that can be translated and used by the computer. Various sensors can be used to measure heat, light, sound, pressure, strain, acidity (pH), oxygen concentration, humidity, pulse, water level, water flow, speed, tilt or simply whether something like a door or a valve is open or shut.

Remote Control - emits a beam of infra red light which carries data signals. Commonly used for input to TVs and VCRs and now becoming used by computers as a "wireless" method of communication.

Light Pen - the pen works directly on the screen. Touch sensitive screens and electronic whiteboards that respond to the touch of a finger are now replacing these.

Bar Code Reader - almost everything you buy has a bar code either on it or on its packaging. The bar coded item is wiped over a laser scanner or a wand is wiped over the bar code to read in the data. It is the same as a scanner but due to the simple nature of the bar code the scanning is very rapid. Used at supermarket checkouts and some libraries.

Braille Keyboard - the keys are marked with raised dots as an aid for the blind.

Concept Keyboard - a flatbed of contact switches covered by a flexible membrane over which can be placed an overlay marked with whole words, pictures or symbols. The computer is then programmed to respond appropriately to these. Used in education as an early-learning aid, in restaurants so the operator does not need to know the prices, and in messy places where a normal keyboard would be at risk.

Optical Character Recognition (OCR) - uses an ordinary scanner to take a photographic image of printed or even hand-written text. Special software then looks at the image, recognises each character and converts it into a text file. This can then be edited using a word processor. It is also used to automatically recognise post codes on letters at sorting offices.

Optical Mark Reader (OMR) - similar to a bar code reader but uses infra-red light to scan pencil marks on prepared forms such as multiple-choice examination answer sheets or lottery tickets.

Magnetic Ink Character Recognition (MICR) - uses ink containing magnetic particles. This method is used by banks to print on a cheque the amount that it is made out for, then it is scanned into a computer.


BackUp Page last updated 30/03/2002 I.D.Lee, Didcot Girls' School
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