INPUT DEVICES

INPUT DEVICES

Input device are necessary to enter data and instruction into a computer. An input device converts input data instruction into suitable binary form (such as ASCII) which can be accepted by the computer. The commonly used input device is a keyboard. A number of input device such as mouse, joystick, light pen, track ball, touch screen etc. have also been develop which don't required typing for inputting information. In recent days voice input system have also been develop, microphone is used for that purpose. Some of the essential input devices are discussed below.

1. Keyboard:

Programs and data are entered into a computer through a keyboard which is attached to computer. A keyboard is analogous to the keyboard of typewriter. It contains alphabets; digits, special characters, and some control keys and function keys.
When a key is pressed an electronic signal is generated, which is detected by a electronic circuit called keyboard encode. A keyboard encoder may be special IC or a single chip micro-computer use as encoder. The function of an encoder is to detect which key has been pressed and to send a binary code (corresponding to the pressed key) to the computer. The binary code may be in ASCII, HEX code, etc.
There are actually three different PC Keyboard:
XT (Extended Technology):- Keyboard has 83 keys
AT (Advanced Technology):- Keyboard has 101 keys
Enhanced Keyboard:- Keyboard has 103 keys

2. Mouse:

The mouse is a palm size device with a bulb built into the bottom. The mouse may be connected to the computer by a cable and may have from one to four buttons (but usually 2). Mice (mouse) come in many shape and size. As we move the mouse in any direction on screen, mouse cursor follows the mouse movement. All movements are relative. Once the mouse pointer is in the correct position on the screen, you can press the mouse button to initiate an action or operation.
There are three different type of mouse:

Optical Mouse

Optical mouse uses a laser to direct the mouse movement. This type of mouse uses a special pad having a grid of alternating lights and dark line.

Mechanical Mouse

Mechanical mouse has a rubber or a metal ball on its bases side, which can roll in all direction. Mechanical sensor between LED and photo detector with in the mouse, detect the direction the balls in rolling and move the cursor accordingly.

Optical mechanical Mouse

It is same as mechanical mouse, it contain a ball which roll on two shafts. It uses optical sensor to detect motion of the ball

3. Microphone:

A microphone is an example of a transducer, a device that changes information from one form to another. Sound information exists as patterns of air pressure; the microphone changes this information into patterns of electric current. The recording engineer is interested in the accuracy of this transformation, a concept he thinks of as fidelity.
Microphones are used in many applications such as telephones, tape recorders hearing aids, motion picture production, live and recorded audio engineering, FRS radios, megaphones, in radio and television broadcasting and in computers for recording voice, speech recognition, VoIP, and for chatting.

4. Joystick:

Joystick is a pointing device one of the input device that are used to move the cursor on the screen. It has stick with balls at its upper and lower ends. We can move the stick in different direction like from left to right on forward or backward. Joystick is mostly used in playing computer games.

5. Light Pen :

Light pen is used as pointing device, which is vary sensitive to light. Light pen uses photoelectric (light sensitive) cell to communicate the screen position to the computer. When the light pen tip is placed against the screen, it is capable of sensing its position on the CRT. As the tip of the pen is moved over the surface of the screen its light sensitive elements detects the light emitted from the screen. We can select the desire option in the menu by touching light pen against desire option.

6. Touch Screen :

This is the easier way to enter data using the finger touch. Touch screen enable the user to select an option by passing a specific part of the screen. It is popular on laptop.

7. Track Ball :

Track ball is also a pointing device and contain a ball which can rotate in any direction. The user spin the ball in different direction to move the cursor on the screen. The associated electronic circuit detects the direction and speed of the spin. The information is sent to the processor. It is used in a laptop computer.

8. Scanner :

Using scanner drawing, graphics, photo, and text can be stored for computer processing by passing an optical scanning mechanism over the information to be stored. In other words, any image, whether text or graphics-typed, printed or drawn can be fed into a computer using a scanner that rather works like a photocopy (softcopy).

9. OCR (Optical Character Reader):

OCR is used for reading text from paper and translating the image into a form that the computer can manipulate. Eg:  into ASCII code. An OCR scan the documents using the photo-electric device to convert the shape into electric signals. OCR is widely use in airline, postal office, bank (for reading postal code), etc.

10. OMR (Optical Mark Reader):

This device can sense the present of a pencil or pen mark. It is widely used in scoring answer for multiple choice questions. The accuracy of an OMR depends on the mark being made properly, if a mark is too light or not solid enough it may be provide error reading.

11. Optical Bar Code Reader

Bar code is a printed series of parallel bar on line of varying width that is used for entering data in to a computer system. The bars are typically black on a white background. An optical barcode reader is a device which can read such bars and convert them electrical pulses to be proceed by a computer. The most commonly used barcode is UPC (Universal product Code). This devices are used in department stores, shopping complex, etc.

12. MICR (Magnetic Ink Character Reader)

MICR is widely used by bank to process large volume of cheque and deposited form written everyday. Especial ink called magnetic ink is used to write character on the cheque and deposit forms. The MICR reads the magnetic patterns of the written characters. MICR provides a secured, high speed method of scanning and processing information. It operates at the speed of reading 2400 characters per second.