Input Unit

Input unit is responsible for taking input from outer world. This unit acts as an interface between user and the computer hardware. Input unit performs its job of taking input with the help of following input devices.

  • Keyboard
  • Mouse
  • Joy Stick
  • Track Ball
  • Light Pen
  • Scanner
  • Bar Code Reader (BCR)
  • Optical Character Reader (OCR)
  • Optical Mark Reader (OMR)
  • Magnetic Ink Character Reader (MICR)
  • Microphone

Let us take an overview one by one.

1 .Keyboard

Keyboard is the most popular input device used by every computer operator now a days. It is used to take input for further processing of the data. It is similar like a typewriter.

The following are the keys on a keyboard

  1. Typing keys ( A – Z , a-z, 0-9 )
  2. Numeric keys (0-9, +,-,*, /, etc) approx 17 keys.
  3. Function keys ( F1 to F12) .These keys are used to perform some specific task and is placed on the top row of the keyboard.
  4. Control keys (Up arrow, Down array, Left arrow, Right arrow, Page Up, Page Down, Home, End) are used to control screen of the computer.
  5. Special Purpose keys: These keys includes Enter, Caps Lock, Num Lock, Tab, and Print Screen.

A keyboard consists of 84 keys to 104 keys depending on its types. Some examples of keyboard are as under:

  • Windows Keyboard- 104 keys
  • AT Keyboard- 84 keys
  • Apple keyboard- 78 keys

The Layout the keyboard is known as QWERTY. The name comes from the first six keys on the top left letter of the keyboard.

2. Mouse

Mouse is the most popular pointing device. It is easy to use and fit into the palm due to its small size. Mouse allows a user to control the screen along the flat surface with help of cursor. With the help of mouse one can easily navigate between different menus and files and folders, etc.

Generally, mouse has two buttons (left and right) with a scroll button in mid center of the mouse. A mouse can be used to control the position of the cursor on the screen. Note: A mouse is never used to enter text into the computer. It works fast and is easy to handle cursor position in comparison to the arrow key of the keyboard.

3. Joystick

Joystick is also an input device that is used to control the movement of the cursor.

  • It consist of a vertical rod mounted on a base with one or two buttons.
  • Joystick is generally used for gaming and graphical purpose.
  • Joystick with the help of lever is capable to move in all directions and controls the movement of a pointer or some other display symbol.
  • A joystick is similar to a mouse, except that with a mouse the cursor stops moving as soon as you stop moving the mouse. With a joystick, the pointer continues moving in the direction the joystick is pointing. To stop the pointer, you must return the joystick to its upright position.

4. Trackball

A trackball is a pointing device which consist of a ball held by a socket containing sensors to response according to rotation of the ball. The user rolls the ball with the thumb, fingers or the palm of the hand to move a cursor.

A  trackball can be managed minutely in comparison to the mouse and can be easily cleaned by removing the track ball to make it dust free.

Trackball is generally used for photo editing and gaming purpose where a minute control is needed to perform the task.

A light pen is also an input device which is generally used to draw pictures, text and even interact with user interface on a computer screen or monitor. A light pen is a pointing device and similar like a pen.

5. Light pen

A light pen is a predecessor of the touch screen technology. Light pen works efficiently with CRT monitor electron beam rather than modern LCD screens.



6. Scanner

Scanner is an input device which works similarly like a photocopy machine. Scanner device is capable to scan documents, photographs and pages of text which are in the form of hard copy and convert them to digital format or electronically save them in the form of soft copy.

A scanner is said to be an input device because it performs image processing process to retrieve raw data to be processed as image, in the same way as keyboard and mouse for other application.