Input and output devices of computer

By | May 14, 2019

Any hardware devices used in the computer system that receives the data and information from the environment and sends them to the storage unit are called input devices whereas the device used to show the result produced by the computer is called an output device. 

Input Devices:

Any hardware devices used in the computer system that receives the data and information from the environment and sends them to the storage unit are called input devices:

An input system performs the following tasks:

  • It reads the data and instructions given by the user.
  • Then converts the accepted data and instructions in computer acceptable format.
  • Then finally it supplies the converted data and instructions to the computer system for further processing.

some commonly used input devices are: keyboard, mouse, trackball, joystick, touch screen, scanner, optical scanner, OCR, OMR, OBCR, MICR, etc.


A keyword is the most commonly used input device. Basically, it comes into importance when one has to type a document. For typing a document the keyboard has a set of alphanumeric keys and some functional special symbols and control keys.

pic: keyboard


Mouse is a most commonly used pointing device which is adjustable in our hand and moved across a small flat surface.The cursor moves on the computer screen according to the movement of mouse on the flat surface. It has two click buttons: left and right click. an icon on the screen is selected by a single click and opened by double click.

fig: mouse


A trackball is a pointing device similar to the mechanical mouse except it has the roller ball placed on the top of mouse. To move the cursor of the screen it is not necessary to move the trackball. As the whole device need not be moved for moving the cursor on the screen trackball requires less space then a mouse and is often built into the keyboard.Trackballs built into the keyboard are commonly used in laptop computers.

fig: trackball


joystick is also a pointing device that is used to move the cursor on the screen. its function is similar to mouse and trackball. it is mostly used in computer gaming. A joystick device consists of a stick with a ball at its lower end and a click button at its upper end. The stick is placed in a socket. The stick can be moved in different directions to move the cursor on the screen in desired direction. The click button mounted on the stick is clicked to select an option on the screen.

fig: joystick

Touch Screen:

Touch screen is the most popular and widely used input device today. A touch screen is sensitive to a finger. The user can easily select the required option by just touching that. touch screen is widely used in devices such as mobile, computer, watch, GPS etc.


A scanner is an input device that provides us an easy input method. it is used to read and store images, printed and handwritten material, pictures directly into the computer. There is no need for manual entry. data read by a scanner can be edited by some special graphics program. Some important type of scanner are: Optical scanner and Magnetic link Character Reader.

fig: scanner

Optical Scanner:

Most of the information which is a typewritten, pencil marks, bar codes etc. can be scanned by the optical scanner. The optical scanner reads such information by employing light source and light sensors. The commonly use d optical scanners are OCR(Optical Character Reader), OMR(Optical Mark Reader), OBCR(optical bar code reader) etc.

Optical Character Reader(OCR)

A general scanner inputs a printed or handwritten material and store them as an image, thus it is not possible to do any word processing task on the input document, because the computer cannot interpret the stored document as letters, numbers, and special character. To overcome this limitation, a scanner is equipped with special software called OCR.

Fig: Optical character reader

Optical Mark Reader(OMR)

Any mark made by pencil or pen is detected by optical mark reader. Generally, in multiple-choice question-answer, several options are given and one has to choose the correct answer by marking a square or circle with a pencil or pen. Then the sheet is submitted to the optical mark reader Then optical mark reader reads the presence or absence of a mark.

fig: optical mark reader

Optical Bar code reader(OBCR):

Data coded in the form of lines are known as bar codes. The bar code represents alphanumeric data by a combination of adjacent bars bu varying their width and the spacing between them. They are used particularly for the unique identification of different products such as books and other goods. An optical bar code reader can read such bars and convert them into electrical pulses to be processed by the computer

fig: optical bar code reader

Output device:

The device used to show the result produced by the computer is called an output device. output device produces either hardcopy or softcopy output. the output in printed form is called hardcopy output. it is permanent in nature whereas softcopy device is not permanent in nature. the output shown on the monitor is an example of softcopy output. the commonly used output devices are monitors, printers, plotters, speakers, headphones, projector etc.


Monitors are the most commonly used output device today which are commonly used to produce soft copy output from the computer. The monitor is similar to the television screen. there are two basic types of monitors: CRT(cathode ray tube) monitors and LCD(liquid crystal display) monitors.

fig: monitor


The printer is the most commonly used output device to produce a hardcopy output. They are generally used to plot images and documents into a paper. According to the technology used by a printer, it can be classified into two broad categories: impact and non-impact printer. Impact printer uses electromechanical technology whereas non-impact printer uses spraying technology for printing a document.

fig: printer


The plotter is the output device similar to the printer which is used for the purpose of printing vector graphics. Plotter interprets command from a computer in sequence manner and draws a line on paper according to the command given to it.

fig: plotter


Speaker is the commonly use audio output device. the main purpose of speaker is to produce audio output that can be heard by listener. Speaker converts analog audio signals into the equivalent air vibrations to make audible sound which can be listened by peoples.

fig: speaker


Headphones are the pair of small loudspeaker drivers used over a user’s ears. They are also an output device similar to the speaker which converts analog audio signals into the equivalent air vibrations to make an audible sound which can be listened by peoples. They are generally connected to electronic devices such as laptop, phone to produce sound.

fig: headphone


A projector is a commonly used optical output device that projects an image or moving image into a projection screen. projector is generally used with laptop or desktop computers. projector with computer is used in classroom for showing slides, pictures, videos etc.

fig: projector

Leave a Reply

Your email address will not be published. Required fields are marked *