Input devices

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
  • Point-and-draw devices
  • Data scanning devices
  • Digitizer
  • Electronic cards based devices
  • Speech recognition devices
  • Vision based 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

  • Commonly used in personal computers and workstations

Trackball

  • Commonly used in laptop (notebook) computers

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

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