INPUT DEVICES

Data must be provided in a suitable form for any computer system to process it.  ‘Input’ means to enter data, programs, commands and user responses into the memory of a computer.

Definition:  An input device is any device that transfers data from the outside world into a computer.

Input devices can be classified into two (2) groups:

1. Manual Data Entry Devices
2. Direct Data Entry Devices 

MANUAL DATA ENTRY DEVICES

KEYBOARD

A keyboard has a set of alphabet keys, number keys and various function keys, so the data entered is in the form of individual letters, words or numbers.  When you press a key on the keyboard, a number (code) is sent to the computer to tell it which key was pressed.

The keyboard has the disadvantage that it is easy to make mistakes by hitting the wrong keys.

MOUSE

The most common pointing input device is the mouse.  As you move it along a flat surface, the pointer on the screen moves in the same direction.  It usually has two buttons:

     1. the left button which selects text and opens files

     2. the right button which is used to access menus.

The mechanical mouse has a rubber ball underneath it to help it roll smoothly in all directions.

The optical mouse uses an optical system to track its movements.  It is not physically connected to the computer and uses infrared or radio waves to communicate with the computer.

Typical mouse techniques include:

1. Point - points at an object on the screen
2. Click - a single click of the left button, used to select an item
3. Double Click - two consecutive clicks of the left button, used to open files, folders and programs
4. Right Click - one click of the right button, brings up a pop-up menu
5. Drag and Drop - holding down the left button while moving the mouse, used to copy files from one location to another 

JOYSTICK

A  joystick is similar to a vehicle’s gear shift but with buttons to activate different commands.  Generally used in game playing but is also useful in virtual reality and controlling robot movements.

TOUCH SCREEN

Touch screens are specially mounted screens that are sensitive to touch, so there is no need for a keyboard or mouse.  Banks, malls and restaurants use touch screens to provide information to the public.

TOUCH PAD

A touch pad is a flat rectangular surface which senses movement of a finger on its surface.  These devices are usually found on notebook computers and are used instead of a mouse.

LIGHT PEN

Similar to a mouse, but you can move it over the screen and point at items on the screen to input data.

VOICE RECOGNITION SYSTEM

Data is input in audio (voice) form.  The input is analyzed for commands and is then processed.  This allows users to dictate text or give commands directly to the computer.

DIRECT DATA ENTRY DEVICES

SCANNER

A scanner allows the user to transfer pictures, graphics and text to a computer.  It scans the image from the top to the bottom, one line at a time and transfers it to the computer. The image can then be used or modified in the paint program, sent out as a fax or printed.

BARCODE READER

Barcodes are groups of bars of different widths and are found on almost every product you buy.  Different groups of bars represent different numbers which are often printed above or below the barcode.  These numbers represent its country of origin, manufacture and item code. The codes are read into the computer using a wand or a fixed scanner.

POINT OF SALE (POS) SYSTEM

Data collected from the barcodes is used to produce information and update a company’s or business database.  Goods are automatically re-ordered and large amounts of data can be input very quickly and accurately.

MAGNETIC INK CHARACTER RECOGNITION (MICR)

Banks process millions of cheques each day.  Every cheque has the cheque number, account number and branch code printed on it using magnetic ink.  The MICR reads this information, along with the value of the cheque into the bank’s information system so that cheques can be cashed.

Information printed in magnetic ink is very secure since it is not possible to change the information by writing over it with a pen.

OPTICAL CHARACTER RECOGNITION (OCR)

Another way of entering handwritten or printed text into a computer system is to scan the text using an OCR program.  The scanned text is turned into a file that can be edited, reformatted and reprinted by a word processor.

OPTICAL MARK RECOGNITION (OMR)

Similar to OCR, however, it relies on the presence or absence of precisely positioned marks on a pre-printed form being read by a special scanner.  This data can then be processed by the system. 

OMRs are mainly used for lotteries and multiple choice answer sheets issued by examination boards.