• The computer will be of no use if it is not communicating with the external world. Thus, a computer must have a system to receive information from the outside world and must be able to communicate results to the external world. Thus, a computer consists of input/output devices.
  • Input/output devices constitute a major part of a computer system. These are also called Peripheral Devices.
  • Without I/O devices, a user cannot communicate with the computer.
  • In computer, inputs are the signals and data received by the system and outputs are the signals and data which are generated from the system.
  • Input and output devices can also be called/written as I/O devices.
  • Input and output devices of a computer system are the devices that connect users to computer.
  • I/O devices are used to interact with the computer system.
  • Input and output devices allow the computer system to interact with the outside world by moving data into and out of the computer system. 
  • I/O devices are directly connected to an electronic module called I/O Module or Device Controller. For example – the speakers of a multimedia computer system are directly connected to a device controller called an audio card, which in turn is connected to the rest of the system.
  • Input and output devices are similar in operation but perform opposite functions. It is through the use of these devices that the computer is able to communicate with the outside world.


  • Inputs are data or signals received by the computer system through various input devices.


  • An Input unit takes the input and converts it into binary form, so that it can be understood by the computer.
  • They are required to enter data and instructions in a computer so that the computer can process that data and provide the result to the user through output devices.
  • Input devices are used to transfer data and user command into the computer system.
  • The speed of a processor is far more than the input devices, such as the keyboard of computer system.
  • The input data to a computer may include both numbers and characters.
  • Input data for the computer system could be in any of the following forms : –
    • Manual inputs from a keyboard or console.
    • Analog inputs from instruments or sensors.
    • Inputs from a storage device, such as pen-drive, CD’s and Floppy Drives.
  • Examples of some input devices are : –
      • Keyboard
      • Mouse
      • Graphics Tablet
      • Trackball
      • Joystick
      • Microphone
      • CD/DVD
      • Pick Devices
      • Source Data Entry Devices
  • Keyboard

    • The first keyboard was developed in the 18th century and was named as a QWERTY keyboard.
    • It is the most common input device used for entering data and information into the computer system.
    • This is the standard input device attached to all computers.
    • The keyboard is a primary device for inputting text by pressing a set of keys.
    • All the keys of keyboard are neatly mounted in a keyboard connected to the computer system.
    • The computer can recognize the electrical signals corresponding to the correct key combination and processing is done accordingly.
    • The user can enter data into the computer by pressing a set of keys on the keyboard.
    • In a keyboard, letters are printed on the keys.  
    • A computer keyboard includes control circuitry which converts the key pressed by the user into key codes so that the computer can understand it.
    • In general, a computer keyboard has following keys : –
1. Alphanumeric Keys : – It includes letters and numbers.
2. Punctuation Keys : – These include comma, period, semicolon etc.
3. Special Keys : – These can be control keys, Shift keys, Alternate key, arrow keys                                  and Caps lock keys etc.
4. Function Keys : –  It contains all the function keys from f1 to f12. Each function                                      key has unique operation in each application and also has                                          some common use in most of the applications.
    • Types of Keyboard – 

                          (A)  On the basis of use of keyboard, they are of two types – General purpose                                            keyboard and special purpose keyboard.

(a) General Purpose Keyboard –

          • They are standard keyboards used with most computer system.
          • They are called general purpose because that have enough keys to make them useful for any type of application.
          • The layout of keyboard is just like the traditional typewriter of the type QWERTY.
          • It also contains some extra command keys and function keys.
          • It contains a total of 101 to 104 keys.

(b) Special Purpose Keyboard –

      (B)  Keyboard devices again may be of two types, on the basis of its wired                             structure – Wired keyboard and Wireless keyboard.

(a) Wired keyboard –

(b) Wireless keyboard –

          • Now-a-days wireless keyboards are also being used which increase user freedom.
          • The wireless feature is achieved by infrared signals or by radio frequency.

(C) All the modern keyboards of computer are classified into three types –

(a) Normal/ Original PC keyboard  – having 84 keys

(b) Advance Technology (AT) Keyboard – having 101-104 keys

(c) Multimedia Keyboard – having 120 – 140 keys.


  • A Mouse is a handy device which can be moved on a smooth surface to cause the movement of a cursor on the screen.
  • It is a pointing device which is used to input data and information into the computer system by pointing on it.
  • Physically, a mouse contains a small case, held under one of the user’s hands with one or more buttons.
  • For GUI-based systems a mouse is an essential pointing-device. The cursor of the mouse moves in the same direction in which the mouse ball rolls.
  • The name mouse is derived from its shape, which looks a bit like a mouse, with its connecting wire that one can imagine to be the mouse’s tail.
  • A Mouse rolls on a small ball and has two or three buttons on the top. When we roll the mouse across a flat surface on the screen, sensors sense the mouse in the direction of mouse movement. The cursor moves very fast with a mouse giving you more freedom to work in any direction.
  • It is easier and faster to move through a mouse compared to movement using keys.
  • Types of Mouse –

 A modern mouse could be mechanical, optical or cordless types. 

(a) Mechanical Mouse :

    • Mechanical Mouse uses ball for the movement of cursor on the computer screen. When the ball is rolled in any direction, a sensor of the mouse detects it and also moves the mouse pointer in the same direction.

(b) Optical Mouse :

    • Optical Mouse uses Laser rays for the movement of cursor on the computer screen.
    • It is an advanced pointing device.
    • Movement is detected by sensing changes in the reflected light rather than the motion of a rolling sphere.

(c) Cord-Less Mouse :

    • Cord-Less Mouse is battery driven and does not need any wire for the physical connection with the motherboard.
    • It transmits data through infrared or radio signal.
    • Computer mice are very useful in designing pictures and graphs and computer and video games by multimedia designers.
    • A Mouse pad is required to move the mouse because it provides a smooth surface. However, an optical or laser mouse doesn’t require a mouse pad.

Digitizing/Graphic Tablet

  • These are used by architects, engineers and designers in Computer Aided Design (CAD) for designing purposes, such as buildings, cars, mechanical parts, robots etc.
  • Digitizing or Graphic tablet is a computer input device that allows one to hand-draw images and graphics, similar to the way one draws images with a pencil and paper.
  • These tablets may also be used to capture data of handwritten signatures.
  • Some tablets are intended as a general replacement for a mouse as the primary pointing and navigation device for desktop computers.
  • These are also used in Geographical Information System (GPS) for digitizing of maps.
  • Graphics tablet is most suited for artists and those who want the natural feel of a pen-like object to manipulate the cursor on their screen.
  • Wacom is the most well known manufacturer of graphics tablets, and is incredibly well respected.


  • Trackball is a movable ball mounted on a stationary device, which can be rotated manually by using fingers.
  • It is also a pointing device.
  • In a trackball, the ball is placed on the top along with buttons which can be rolled with the fingers. These are used in playing video games.
  • Mouse and mobile phones are equipped with trackballs to navigate addresses as well as play games.


  • Joystick is a remote control device for a computer which is used for playing video games to indicate the position.
  • It has a stick that pivots on a base and is used for controlling the action in video games.
  • The User moves a spherical ball with the help of a stick in the joystick as opposed to the trackball where fingers are used for moving the ball.
  • Joysticks are also used for controlling machines such as cranes, trucks, underwater unmanned vehicles, flight simulators, industrial robots etc.
  • The Joystick has a base and a handle for controlling the movement of the cursor on the screen.


  • A Microphone is an acoustic-to-electric transducer or sensor and is used to convert sound signals into electrical signals.
  • It was originally invented by Emile Berliner in 1877, and allows us to record voices or sounds and place them onto computers, generally as a wave file.
  • Voice Recording Microphone is used to record sound. To connect a microphone, we insert the plug of it into the back of the computer system.
  • Integrated microphones can be found on laptops and some desktop monitors.
  • These microphones are usually a small hole in front of the computer which when spoken into, will record your voice.

Pick Devices
  • Pick devices are used to select an object on the screen.
  • The selected object can be text or graphics.
  • Examples of pick devices are light pens and touch screens.There are several other pick devices such as microphones and speakers. 
Light Pens
    • A light pen can work with any CRT monitor but not with LCD monitors.
    • A Light pen is a pen like light-sensitive device.
    • It is connected by a wire to the computer terminal to detect the CRT beam when pointed towards the screen and generate a narrow electrical pulse that can be fed to the computer as an input signal.
    • It is used to draw on the screen or to point to the displayed objects.
    • It operates by detecting the light emitted by the screen phosphors.
    • It is used by architects and engineers for CAD applications and editing.
Touch Screens
    • Touch screens are monitors / electronic visual display screens which detect where they are being touched.
    • The user makes selections by directly touching the screen, rather than moving a cursor to the point on the screen with a mouse or joystick Now days touch screens are being used in ATM machines for making it user friendly and Kiosk machines are used for guiding the travelers about their travel plans.
    • Touch screens are also used in many of the modern cell phones.

Source Data Entry Devices

  • Entry of data into a computer system directly from the source, without transcription is called source data entry.
  • Source data entry devices have a lower probability of error in input data than standard keyboard entry.
  • Some of the common source data entry devices are –
Digital Camera
    • A Digital camera is an electronic device which takes video or still photographs or both, digitally by recording images via an electronic image sensor.
    • Digital cameras can do things which film cameras can’t, for example displaying images on screen immediately after they are recorded. Images recorded on a digital camera can be cropped for editing, deleted and various types of special effects can be created by using Photoshop software.
    • Digital cameras look like ordinary cameras but have sufficient memory in the form of chips to store thousands of images, rather than using photographic films.
    • Most digital cameras allow users to choose the resolution needed for a picture.
    • Most of digital camera connect directly to a computer to transfer data. A USB port is generally used for this purpose. A Wireless connection can also be used for connecting to a computer via Bluetooth.
    • Digital cameras use memory cards with flash memory to store images.
    • The joint photographing expert’s group standard (JPEG) is the most common file format used for storing data in a digital camera. Other formats include raw image format, DNG format etc.
    • A Scanner is an input device and is used to input data into the computer system in the form of pictures.
    • It optically scans images, printed text, handwriting, or an object, and converts it to a digital image.
    • Examples of scanners are a desktop or flatbed scanner.
    • In scanners, the document is placed on a glass window for scanning.
    • Mechanically driven scanners that move the document are typically used for large-formatted volume of documents.
    • Another type of scanner is a planetary scanner. This scanner takes photographs of books and documents.
    • Three dimensional scanners are used for producing three-dimensional models of objects.
Optical Mark Recognition (OMR)
  • Universities and colleges often use OMR for the evaluation of OMR sheets for competitive exams.
  • OMR is the scanning of paper to detect the presence or absence of a mark in a predetermined position.
  • Now days, it is used as an input device for source data entry purposes.
  • Universities and colleges often use OMR for the evaluation of OMR sheets for competitive exams.
  • OMR sheets consist of multiple choice question papers and students are required to make a mark to indicate their answers.
  • OMR is used in the evaluation of questionnaires, surveys and university exam OMR sheets.
Magnetic Ink Character Recognition (MICR)
  • Magnetic Ink Character Recognition is a character recognition system that uses special ink and characters. When a document that contains this ink needs to be read, it passes through a machine, which magnetizes the ink and then translates the magnetic information into characters.
  • MICR technology is used by banks for faster processing of large volumes of cheques.
  • Numbers and characters found on the bottom of checks (usually containing the check number, sort number, and account number) are printed using Magnetic Ink.
  • To print Magnetic Ink codes, we need a laser printer that accepts MICR toner.
  • MICR provides a secure, high-speed method of scanning and processing information.
  • This technology is used for processing large volume of data.
  • It speeds up data input for the bank because cheques can be directly fed into the input device as it also ensures accuracy of data entry.
  • The most commonly used character set by MICR devices are known as E13B font which consists of the numerals 0 to 9, and four special characters.
Bar Code Reader
  • A barcode reader is an electronic device which is used to read printed barcodes.
  • Barcodes represent alphanumeric data which is a combination of vertical lines (bars) that vary in width and length.
  • It is a fast and effective way to input data.
  • A Barcode reader uses a laser beam to read the series of thick and thin lines which represent the bar code number.
  • The bar code is 13 digits long and it has four main divisions. The First two digits of a bar code represent the country, the second part represents the manufacturer’s code (five digits) the third part represents the product code (five digits) and the last digit is a check digit.
Magnetic Stripe Reader
  • A magnetic reader is a hardware device which is used to read the information encoded in the magnetic stripe located at the back of a credit/debit card.
  • A bank card holds data about the owner of the card, bank account number and code of the bank branch, where the account is held.
  • A magnetic reader is a hardware device which is used to read the information encoded in the magnetic stripe located at the back of a credit/debit card. A bank card holds data about the owner of the card, bank account number and code of the bank branch, where the account is held.
  • Magnetic stripe readers are often used at supermarkets and in many different types of shops. In these machines data is read electronically and the point of sale is called Electronic Point of Sale (EPOS).

     347 total views,  1 views today


    Leave a Reply

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

    This site uses Akismet to reduce spam. Learn how your comment data is processed.