Input Devices of Computer

A computer in itself is an empty plastic box. What makes it truly function-able and useful are the output and input devices of computer. These parts are assembled, and work in sync to make a computer what it truly is. The components of the computer can be largely classified under-

  1. Input unit
  2. Memory unit
  3. Processing unit
  4. Output unit

In this article, we will discuss deeply the input unit and its devices.

What is an Input Device?

The data received by any computer goes through the input unit. The input unit comprises devices like a mouse, keyboard, barcode scanner, etc. Each of the input devices of computer acts as a mediator between the users and the computer.

The data that is to be processed is put through the input unit, the computer accepts the raw data in the binary form, processes the data, and produces the desired output.

Functions of an Input Device

The 3 major functions of the input unit are-

  • Take the data to be processed from the user
  • Convert the given data into machine-readable form.
  • Transmit the converted data into the main memory of the computer.

Its sole purpose is to connect the user and the computer and create easy communication between them.

Examples of Input Devices

Let us discuss about the different computer input its devices in detail.


The keyboard is an input device that is used to type and feed the data into the computer. The data can be in words, numbers, and symbols. It consists of mechanical buttons called the ‘keys’.

There are 5 different keys on the keyboard-

 1. Alphabetical keys from A-Z
 2. Numerical keys from 0-9
 3. There are 12 function keys on the top of the keyboard F1-F12. Each of which performs a special function.
4. There are control keys, which help in gaining control of the screen and the keyboard. These include 4 direction keys, home, end, delete, page-up, page-down, control(ctrl), alternate(alt), escape(ESC).
5. Then there are special keys which by the name you can figure, are used for special tasks. These include a print screen(PrtScr), Spacebar, Tab, Num Lock, shift, enter, and caps lock.

Working – The major part of the working of the keyboard is done by the ‘key matrix’. This is a grid that is beneath the keys of the keyboard. Each time a key is pressed, the broken circuit beneath each key gets completed. A tiny amount of current then flows through the matrix and information is received by the computer, which key has been pressed. This is a signal, what is to be displayed on the screen. 
The keyboard is attached to the computer by a cable. However, there are now wireless keyboards as well in the market which work on Bluetooth technology.


The mouse is the input device that is used to coordinate the pointer on the screen. The mouse is used to select, point, and display additional menus on the screen. It has typically two buttons. The left button is used to select or move items on the screen. The right button is used to display additional dropdowns.

The mouse is mainly classified as mechanical and optical. The mechanical mouse consists of a trackball beneath it, and are no longer in use. The optical mouse uses laser light for pointing and has more accuracy and speed than the mechanical one. 

Working – The traditional trackball mouse has been replaced by the optical mouse. This mouse has a LED installed underneath it along with a CMOS sensor. The LED emits light and then the light gets reflected by the surface of your desk. This reflected light is sensed by the CMOS sensor, which in turn sends the signal to a DSP. This DSP determines the pattern made and then sends the coordinates to the computer. Based on it the cursor on the display moves respectively.
There is now even a mouse specifically designed for gaming purposes. Such a mouse can contain numerous buttons designed to give control in the game. usually, the mouse is connected through a cable but, there are now Bluetooth-operated wireless mouses as well. However, the working remains the same.


The microphone is an input device used to feed audio in the computer. The microphone can be used for several purposes like-

  1. Chatting online
  2. Used to feed audios for presentations
  3. Used for VoIP(Voice Over Internet Protocol)
  4. For voice recognition system
  5. Record audio for different purposes

Microphones are a kind of transducers, as they convert mechanical energy to electrical energy(AC voltages). Let us understand its working

Working – The sound waves created are carried towards the microphone. Inside the microphones there exists a small plastic diaphragm, which starts moving when the sound hits it. This makes the coil attached to it move too. The permanent magnet wounded by the coil produces a magnetic field. After that, the movement of the coil in this magnetic field causes the flow of current through the coil. This electricity is then amplified and sent to the computer. And thus the sound can be stored or used by the computer.


A scanner is an input device and works similarly to a photocopy machine. It is used to scan documents and then display them on the screen. It is used to store a hardcopy in digital format on the computer.

Working – The scanning device is swept across the document placed on the glass panel. The device emits light which is then reflected from the surface of the document. This reflected light is passed through a series of lenses and glasses and then reaches a photosensitive device. The most commonly used one is CCD(charged coupled device). This device senses the light, converts it into an electrical signal, and then sends it to the computer. In this way, the digital image of the scanned document is procured.

Barcode Reader

The barcode reader is a type of optical scanner that is used to read barcodes and decode the data stored in them and send it to the computer. Just like a scanner this also consists of a light emitter, a series of lenses, and a photosensitive device installed inside it. In addition to this is a decoding circuitry attached to decode the barcodes. The working is the same as that of the flatbed scanner.


A webcam is a type of camera that streams still pictures or videos in real-time to the computer. Unlike our common digital cameras, these do not hold any special function key nor storage. They are connected to the computer and use the computer’s storage instead. Today webcams come embedded in laptops but they used to be connected through cables earlier. 
The webcams have an image sensor, a lens, and circuitry installed inside them. This is to capture the images and motion pictures.

Working – The camera obtains the picture through the lenses and is received by the photosensitive circuitry, mostly CCD. This then converts the image captured into the digital format and feeds it to the computer. The webcams are now also sometimes come with pre-installed microphones inside them, to capture both image and the audio.
The webcams can be used for video calling purposes, to capture images, record videos, and sometimes even stream online on the internet.


The stylus is also one of the common types of input devices nowadays. With the introduction of touch-screen desktops and laptops, the stylus has become common among users. The stylus is shaped like a pen and is used to write, draw, point on the screen. It has replaced the use of the keyboard and mouse.

In addition, it gives more precision in terms of pointing or drawing on the screen.

Earlier it was developed only for graphic designing purposes but now it is used even in mobile phones.

This completes our tutorial on – “input devices of computer”. I hope you liked it. Do let us know in the comments in case of any questions or suggestions.

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