Input devices

An input unit of a computer system performs the following functions:

It accepts (or reads) instructions and data from outside world
It converts these instructions and data in computer acceptable form
It supplies the converted instructions and data to the computer system for further processing
Provide means of communication between a computer and outer world
Also known as peripheral devices because they surround the CPU and memory of a computer system
Input devices are used to enter data from the outside world into primary storage
Output devices supply results of processing from primary storage to users

Role of I/O Devices

Commonly Used Input Devices

Keyboard Devices

Allow data entry into a computer system by pressing a set of keys (labeled buttons) neatly mounted on a keyboard connected to a computer system
101-keys QWERTY keyboard is most popular

Point-and-Draw Devices

Used to rapidly point to and select a graphic icon or menu item from multiple options displayed on the Graphical User Interface (GUI) of a screen
Used to create graphic elements on the screen such as lines, curves, and freehand shapes
Some commonly used point-and-draw devices are mouse, track ball, joy stick, light pen, and touch screen

Mouse

Trackball

Joystick

Commonly used for video games, flight simulators, training simulators, and for controlling industrial robots

Electronic Pen

Pen-based point-and-draw device
Used to directly point with it on the screen to select menu items or icons or directly draw graphics on the screen
Can write with it on a special pad for direct input of written information to a system
Pressure on tip of a side button is used to cause same action as right-button-click of a mouse

Touch Screen

Most simple, intuitive, and easiest to learn of all input devices
Enables users to choose from available options by simply touching with their finger the desired icon or menu item displayed on the screen
Most preferred human-computer interface used in information kiosks (unattended interactive information systems such as automatic teller machine or ATM)

Data Scanning Devices

Input devices that enable direct data entry into a computer system from source documents
Eliminate the need to key in text data into the computer
Due to reduced human effort in data entry, they improve data accuracy and also increase the timeliness of the information processed
Demand high quality of input documents
Some data scanning devices are also capable of recognizing marks or characters
Form design and ink specification usually becomes more critical for accuracy

Image Scanner

Input device that translates paper documents into an electronic format for storage in a computer
Electronic format of a scanned image is its bit map representation
Stored image can be altered or manipulated with an image-processing software

Optical Character Recognition (OCR) Device

Scanner equipped with a character recognition software (called OCR software) that converts the bit map images of characters to equivalent ASCII codes
Enables word processing of input text and also requires less storage for storing the document as text rather than an image
OCR software is extremely complex because it is difficult to make a computer recognize an unlimited number of typefaces and fonts
Two standard OCR fonts are OCR-A (American standard) and OCR-B (European standard)

Optical Mark Reader (OMR)

Scanner capable of recognizing a pre-specified type of mark by pencil or pen
Very useful for grading tests with objective type questions, or for any input data that is of a choice or selection nature
Technique used for recognition of marks involves focusing a light on the page being scanned and detecting the reflected light pattern from the marks

Bar-code Reader

Scanner used for reading (decoding) bar-coded data
Bar codes represent alphanumeric data by a combination of adjacent vertical lines (bars) by varying their width and the spacing between them
Scanner uses laser-beam to stroke across pattern of bar code. Different patterns of bars reflect the beam in different ways sensed by a light-sensitive detector
Universal Product Code (UPC) is the most widely known bar coding system

Magnetic-Ink Character Recognition (MICR)

MICR is used by banking industry for faster processing of large volume of cheques
Bank’s identification code (name, branch, etc.), account number and cheque number are pre-printed (encoded) using characters from a special character set on all cheques
Special ink is used that contains magnetizable particles of iron oxide
MICR reader-sorter reads data on cheques and sorts them for distribution to other banks or for further processing

Digitizer

Input device used for converting (digitizing) pictures, maps and drawings into digital form for storage in computers
Commonly used in the area of Computer Aided Design (CAD) by architects and engineers to design cars, buildings medical devices, robots, mechanical parts, etc.
Used in the area of Geographical Information System (GIS) for digitizing maps available in paper form

Electronic-card Reader

Electronic cards are small plastic cards having encoded data appropriate for the application for which they are used
Electronic-card reader (normally connected to a computer) is used to read data encoded on an electronic card and transfer it to the computer for further processing
Used together as a means of direct data entry into a computer system
Used by banks for use in automatic teller machines (ATMs) and by organizations for controlling access of employees to physically secured areas

Speech Recognition Devices

Input device that allows a person to input data to a computer system by speaking to it
Today’s speech recognition systems are limited to accepting few words within a relatively small domain and can be used to enter only limited kinds and quantities of data

Vision-Input Systems

Allow computer to accept input just by seeing an object.
Input data is normally an object’s shape and features in the form of an image
Mainly used today in factories for designing industrial robots that are used for quality-control and assembly processes