Main Input Devices of Computers

The following are the main input devices:
a) Keyboards:
The key board resembles a typewriter. But there are additional keys that handle control functions. The computer keyboard has three categories of keys.
=> Alphanumeric keys 
=> Special key
=> Function keys    
The Alphanumeric Keys comprises of alphabets (A-Z or a-z), numbers (0-9) and other characters, like space, ./ × ' ; : — ~ ! @ # $ % ^ & * ( ) - + = | \ { } [ ].

The Special Keys perform specific tasks. Some of the special keys are, Enter or the Return key, Backspace key, Del key, the Ins key, Shift keys, e Caps lock key, Num Lock key, Ctrl key and the Alt key.

The Function Keys are used to perform a set of operations by a single keystroke. The function keys can be used for various functions. They can be used as short hand for a sequence of keystrokes, configured accordingly.

Mouse: One of the most popular types of specialized input devices for terminals or micro computers is a mouse. Which is used as a pointing device, the mouse is a small box, about the size of a tape cassette with a round ball on the bottom and one or more buttons on the top. The mouse is attached to a terminal or micro computer by a cable. A mouse enables the user to manipulate a pointer or an arrow on a terminal or micro computer screen.
Joystick: Joysticks are designed in the shape of handles that swivel in 360 degree arcs, enabling their users to control screen figures.
Its utilization for commercial data processing applications is limited.  

Barcode Reader: Data can be coded in the form of light and dark bars with coded spacing’s and thickness. These are called barcodes which are commonly used to identify items. Each item is labeled with a Universal Product Code (UPC). The code is read by a wand or pen which transmits a laser beam and receives the reflection from the label. These pulses are compared with standard codes stored in the computer. A barcode is commonly seen on the back of any book published in recent times.

OMR: The Optical Mark Reader (OMR) is a device which can detect the presence or absence of a mark on a paper. Light is incident onto the paper and the reflected light is detected. The presence of a mark is detected due to intensity of light being reflected from the mark. OMR is used in reading answer sheets, questionnaires.
OCR: Optical Character Reader (OCR) is an improvement over OMR. This can not. Only detect a mark but can also recognize its shape and identify characters directly from source documents. The amount of light reflected differs depending on the shape of the character and the OCR can detect and interpret these minor differences.  
MICR: Magnetic Ink Character Recognition (MICR) systems use special ink which can be magnetized, to print characters that can then be read and decoded by special magnetic devices.
This system is widely used by banks for processing cheques. The cheque number, the bank and branch code and the account number are printed with ink containing magnet sable particles of iron oxide.

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