Types of Input Devices

Keyboard

A keyboard is the most widely used input device, which converts input data as typed by user into electronic binary codes suitable for computer to understand. A keyboard is very similar to an electronic typewriter. It consists of all the alphanumeric keys similar to typewriter besides it consists of extra keys. The other keys that a keyboard consists are as follows

a.                   Numeric keypads similar to calculator.

b.                  Special Keys like Alt, Ctrl, delete, home, arrow keys etc.

c.                   Function keys.

Mouse

A mouse is a hand held pointing device that is usually moved on a flat surface to produce a corresponding movement of a cursor on the screen. It is used to replace hard to learn key combination with easy to learn “point and click” operation. The mouse is also useful for graphical programs that allow us to draw pictures just as the way we use pen, pencil or paintbrush.

On the bottom of most mice there is a ball, which rotates as mouse is moved on the flat surface. Inside mouse there are two sensors, which detects the vertical and horizontal movement of the mouse. It also contains several (usually two) buttons on the top for different click operation. There are several types of mice. They are mechanical, optomechanical and optical.

Usually mouse is connected to a computer through serial port or PS/2 port. Although wireless mouse is also available nevertheless the function of mouse is same.

Trackballs

A trackball is essentially a mouse turned upside down so that ball is rotated directly instead of moving a mouse to rotate the ball. All the bottoms are placed next to the ball. Since the trackball device does not require movement it consumes less space relatively to the mouse. It is also a popular in portable devices like laptops.

Joystick

A joystick is also a pointing device commonly used in games. It provides more realistic control for games than that with key board and mouse. It consists of a hand held stick that pivots on one end and can be rotated in any directions.

Light pen

A light pen is also an input device used for pointing or selecting objects on the screen. It is a pen like device, which consists of a photosensitive detector at its tip. As the pen is placed or moves on the screen it detects light from the screen.  It is generally used for drawing and in Computer Aided Design (CAD).

Touch Screen

In a touch screen usually external devices for pointing are not required. A user can use their own finger to select items. There are two types of Touch screens: Photonic and touch sensitive.

In touch sensitive screen, the display is covered with touch sensitive material. The user must make contact with the screen to select an item.

In photonic type a matrix of beams covers the screen in the horizontal and vertical dimensions. These beams are interrupted as user touches the screen. Interrupted beams determine the exact position of touch.

Scanner

The scanner is like an office copier (Photo copy machine), except it creates a file instead of a paper copy. The quality of scanner is measured in dpi (dots/inch), which the ability of scanner to scan smallest portion of picture. Most modern scanner have several features like optical character recognition (OCR). They can even send scanned images directly to printer or fax the scanned image.