ICT

Output Devices

                     Output devices translate information processed by the computer into a from that either humans or other machines can understand.There are a variety of output devices,which can be connected to a computer.Some of the common output devices are explained in the following sections.

Monitor

                The most common from of output is the computer screen.It is more correctly called the ‘monitor’ and sometime referred to as the visual display unit or VDU.

The quality of computer monitor is based on the following properties:

·         Resolution: Resolution is the number of pixels,which the sceen can display.A’pixel’ is the ‘pictuer element’ and refers to the smallest area of the screen that the computer can change.

·         The number of colours it can display (dependent on the computer as well)

·         Radiation output.

Different types of display sceens

CRT monitor  –  A cathode-ray tube and associated electronics connected to the video output of computer.These have higher resolution than TVs.Larger monitors with high resolution are used for specialized application such as desktop publishing and CAD.

Liquid crystal display (LCD)  –  LCDs are screens made from two glass/plastic plates with liquid in between.LCDs are commonly used for calculators and laptop computers,as they are far flatter than is possible with cathode ray screens used in TVs and standard computer monitors.

Main differences of LCDs as compared with CRT monitors are :

·         Take s very little space

·         Small energy consumption

·         Sharp pictures

·         No flicker or geometric distortion

·         Fairly expencive

·         Limited viewing angle

·         Slower response time

Printers


             Many different types of printer are in use today.Two primary technologies used for printing are impact printing and non-impact Printers use a print head containing a number of metal pins which strike an inked ribbon placed between the print head and the paper.The non-impact printers are much quieter than impact printers as their printing head do not strike the paper.

Three most common printer types are :

EX:- Dot matrix printers,Inkjet printers and Laser printers.


Dot matrix Printers

         These printers work by firing of tiny pins(which are located in the print head),through a ribbon similar to that found on a typewriter.Such printers are cheap and have the lowest running cost compared to any other type of printer.As the head moves across the head moves across the paper the correct pins are fired out to hit an inked ribbon and from the shape of the number of pins,the higher the quality of the print.Dot matrix printers are impact printers and are used to print multipart stationary.So to print several copies of a document at the same time you will need to use a dot matrix printer.

Inkjet Printers
         Inkjet printers can produce high quality text and graphics.They are quieter than dot matrix printers.The technology involves ink flowing through the appropriate nozzles (usually in an array of 64) where it is then heated and a bubble is formed.This expands to release a tiny droplet of ink onto the paper.

Laser Printer

            These non-impact printers offer high-speed printing and an excellent quality of text and graphics.A laser beam is used to from an image on a rotating, charge metal drum.This then picks up toner cartridge and transfers it onto paper.Very soon afterwards heat and pressure are applied so the toner sticks to the paper.Slince they are page printers they are very fast.Color laser printers are now available and are mainly used for desktop publishing.Although they are expensive,they are likely eventually to come into widespread use.

Speakers / Headphones
                   Speakers or headphones may be used to get sound output from a computer.There are different types of speakers ranging from simple speakers, which provide simple sound to speakers, which can provide theater-like surround sound.