List any three input and three output devices of a computer and explain one each

01 c] List any three input and three output devices of a computer and explain one each.


Input Devices:-


  • Every computer supports a keyboard – either a physical or touchscreen.
  • The keyboard has a QWERTY layout and contains a large number of symbols.
  • Each letter, numeral, or symbol is known as a character, which represents the smallest piece of information.
  • Each character has a unique value called the ASCII (American Standard Code for Information Interchange) value.

Pointing Devices:

  • GUI (Graphical User Interfaces) like windows needs a pointing device to control the movement of a cursor on the screen.
  • This is implemented as a mouse on a desktop and a touchpad on a laptop. The earliest form has a rotating ball and two buttons.
  • The left button is used for selecting (by clicking once) and executing (by clicking twice).
  • The right button is used to check and change attributes.
  • The optical mouse uses infrared laser/LED, the wireless mouse uses radio frequency technology.


  • A scanner is a device that creates a digital image of a document by optically scanning it.
  • The flatbed scanner doesn’t exceed more than A4 size. It is operated by using special software.
  • The document to be scanned is placed on a glass plate covered by a lid.
  • Modern scanners have an OCR (Optical Character Recognition) facility which extracts the text as a stream of characters i.e. converting image file to text file and MICR (Magnetic Ink Character Recognition) reads the codes using handheld barcode readers.

Output Devices:-


  • The monitor is an integral part of the computer which displays both text and graphics.
  • The performance is measured in terms of image quality, resolution, and energy consumption.

CRT (Cathode Ray Tube) Monitors:

  • The CRT monitors have a rarefied tube containing three electron guns.
  • The guns emit electrons to create images.
  • They usually have a resolution of 640*840 pixels.
  • They are large, heavy, energy-efficient, and produce a lot of heat.

LCD (Liquid Crystal Display) Monitors:

  • The image is formed by applying a voltage to crystals.
  • The backlight is provided by fluorescent light.
  • They consume less power, generate less heat, and have an increased life span.

Impact Printers:

  • It produces the hard copy of the output.
  • The impact printers are old and noisy. But, still, the dot-matrix printer is in usage.

Dot-Matrix Printer:

  • The print head of the dot-matrix printer has either 9 or 24 pins.
  • When the pins fire against the ribbon, an impression is created on the paper.
  • The speed is 300 cps and doesn’t produce high-quality output.
  • It can produce multiple copies.

Daisy-wheel Printer:

  • It employs a wheel with separate characters distributed along its outer edge.
  • The wheels can be changed to obtain a different set of fonts.

Line Printer:

  • For heavy printing, the line printer is used. It uses a print chain containing the characters.
  • Hammers strike the paper to print and it rotates at the speed of 1200 lpm.
  • It is also noisy and is of low quality.

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