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Fundamentals of Computers - Chapter 2

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Fundamentals of Computers

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Fundamentals of Computers - Chapter 2

  1. 1. © Oxford University Press 2016. All rights reserved. Fundamentals of Computers Reema Thareja
  2. 2. © Oxford University Press 2016. All rights reserved. Chapter 2Chapter 2 Input and Output Devices
  3. 3. © Oxford University Press 2016. All rights reserved. An input device is used to feed data and instructions to the computer. Input Devices
  4. 4. © Oxford University Press 2016. All rights reserved. Keyboard • Main input device for computers • Most keyboards have between 80 and 110 keys, which include the following: Typing keys Numeric keys Function keys Control keys Advantage  Easy to use and low-priced Disadvantages  Cannot be used to draw figures  Moving the cursor to another position is very slow Keyboard
  5. 5. © Oxford University Press 2016. All rights reserved. Mouse • A pointing device that helps users to select items on screen by controlling the movement of pointer • Can be used to perform the following operations:  Point Click  Drag Scroll Advantages  Low-priced  Easy to use and can be used to quickly place the cursor Disadvantages  Needs extra desk space to be placed and moved easily  The ball must be cleaned to remove dust from it Mouse
  6. 6. © Oxford University Press 2016. All rights reserved. Trackball • A pointing device to control the position of the cursor on the screen • Usually used in notebook computers, where it is placed on the keyboard Advantages  Provides better resolution  Occupies less space  Easier to use as compared to a mouse as its use involves less hand-and-arm movements Disadvantage  The trackball chamber is often covered with dust, so it must be cleaned regularly Trackball
  7. 7. © Oxford University Press 2016. All rights reserved. Touchpad • A small, flat, rectangular stationary pointing device with a sensitive surface of 1.5’’–2’’ • Users have to slide their fingertips across the surface of the pad to point to a specific object on the screen • The surface translates the motion and position of the user’s fingers to a relative position on the screen Advantages  Occupies less space  Easy to use  Built in the keyboard so no need to carry an extra device Touchpad
  8. 8. © Oxford University Press 2016. All rights reserved. Handheld Devices Joystick • A cursor control device widely used in computer games and CAD/CAM applications Stylus • A pen-shaped device to enter information or write on the touch screen of a handheld device Touch screen • A display screen that can identify the occurrence and position of a touch inside the display region. The user can touch the screen by using either a finger or a stylus Handheld Devices
  9. 9. © Oxford University Press 2016. All rights reserved. Optical Input Devices • Use light as a source of input for detecting or recognizing different objects such as characters, marks, codes, and images • Some optical devices are: Barcode reader Image scanner Optical character recognition (OCR) devices Optical mark readers (OMR) Magnetic ink character recognition (MICR) devices Optical Input Devices
  10. 10. © Oxford University Press 2016. All rights reserved. Optical Input Devices • Works by directing a beam of light across the barcode and measuring the amount of light reflected back Advantages  Low-priced, portable, and easy to use Disadvantages  Must be handled with care  Can interpret information using a limited series of thin and wide bars. To interpret other unique identifiers, the bar display area must be widened Barcode Reader
  11. 11. © Oxford University Press 2016. All rights reserved. • Captures images, printed text, photographs, etc., and converts them into digital images for editing and display on computers Advantages  Any document can be scanned and stored in a computer for further processing  Scanned and stored document will never deteriorate in quality with time Disadvantages  Scanned documents are bigger in size as compared to other equivalent text files  Scanned documents are uneditable Image Scanner
  12. 12. © Oxford University Press 2016. All rights reserved. • The process of converting printed materials into text or word processing files that can be easily edited and stored Advantages  Printed documents can be converted into text files  These files occupy less space and are editable Disadvantages  Cannot recognize all types of fonts  Documents that are poorly typed or have strikeover cannot be recognized Optical Character Recognition (OCR)
  13. 13. © Oxford University Press 2016. All rights reserved. • The process of electronically extracting data from marked fields, such as checkboxes and fill-in fields, on printed forms Advantage  Works at very high speeds. Can read up to 9,000 forms per hour Disadvantages  Difficult to gather large amount of information  Some data may be missing in the scanned document  A sensitive device, it rejects an OMR sheet if it is folded, torn, or crushed Optical Mark Recognition (OMR)
  14. 14. © Oxford University Press 2016. All rights reserved. • Used to verify the legitimacy of paper documents, especially bank checks • Consists of magnetic ink printed characters that can be recognized by high-speed magnetic recognition devices Advantage  Ease of readability and high security Disadvantage  Expensive equipment Magnetic Ink Character Reader (MICR)
  15. 15. © Oxford University Press 2016. All rights reserved. Audio Input Devices • Used to either capture or create sound • Enable computers to accept music, speech, or sound effects for recording and/or editing • Some examples are microphones and CD players Video Input Devices • Used to capture video from the outside world into the computer • Some examples are digital cameras and web cameras Audio/Video Input Devices
  16. 16. © Oxford University Press 2016. All rights reserved. Electromechanical devices that accept digital data from the computer and convert them into human- understandable form Output Devices
  17. 17. © Oxford University Press 2016. All rights reserved. Soft Copy Output Devices • Produce an electronic version of an output. For example, a file that is stored on a hard disk, CD, or pen drive and is displayed on the computer screen Features :  Output can be viewed only when the computer is on  A user can easily edit soft copy output  It cannot be used by people without a computer  Searching for data in a soft copy is easy and fast  Electronic distribution of material is cheaper, easy, and fast Softcopy Output Devices
  18. 18. © Oxford University Press 2016. All rights reserved. Monitors • Used to display video and graphics information generated by the computer through the video card • Similar to television screens but they display information at a much higher quality • Come in three variants: Cathode ray tube (CRT) monitor Liquid crystal display (LCD) monitor Plasma monitor Monitors
  19. 19. © Oxford University Press 2016. All rights reserved. • Specialized vacuum tubes in which images are produced when an electron beam strikes a phosphorescent surface Advantages  Provide good quality images  Low-priced Disadvantages  Occupy a large space on the desk  Bigger in size and weight and therefore not easily portable  Power consumption is higher than in other monitors CRT Monitor
  20. 20. © Oxford University Press 2016. All rights reserved. • Thin, flat, electronic visual displays that use the light modulating properties of liquid crystals • Replacing CRT displays at a fast pace Advantages  Very compact and lightweight  Consume less power  Little or no flicker of images  Cause less eye fatigue Disadvantages  More expensive than CRTs  Images are not very clear when tried to view from an angle LCD Monitor
  21. 21. © Oxford University Press 2016. All rights reserved. • Thin and flat monitors widely used in televisions Advantages • The technology used in plasma monitors allows producing a very wide screen • Very bright images can be formed • Not heavy and are thus easily portable Disadvantages • Very expensive • High power consumption • Since the images are phosphor-based, at times, they may suffer from flicker visions Plasma Monitor
  22. 22. © Oxford University Press 2016. All rights reserved. Projectors • A device that takes an image from a digital source and projects it onto a screen or another surface • Can be broadly classified into two categories:  LCD projectors use their own light to display the image on the screen/wall. The room must be first darkened, else the image formed will be blurred.  Digital light processing (DLP) projectors use a number of mirrors to reflect light. When using a DLP projector, the room may or may not be darkened because it displays a clear image in both situations. Projectors
  23. 23. © Oxford University Press 2016. All rights reserved. Hard Copy Output Devices • Produce a physical form of output. For example, the content of a file printed on paper Features :  A computer is not needed to see the output  Editing and incorporating the edits in the hard copy is difficult  Output can be easily distributed to people who do not have a computer  Searching for data in a hard copy is a tiring and difficult job  Distribution of a hard copy is not only costly but slower as well Hard Copy Output Devices
  24. 24. © Oxford University Press 2016. All rights reserved. Printers • A device that takes text and graphics information obtained from a computer and prints it on a paper Printers
  25. 25. © Oxford University Press 2016. All rights reserved. • Print characters by striking an inked ribbon against the paper Advantages  Enable users to produce carbon copies  Low-priced Disadvantages  Slow  Poor print quality, especially in the case of graphics  Can be extremely noisy  Can print only using the standard font Impact Printers
  26. 26. © Oxford University Press 2016. All rights reserved. • Print characters as a pattern of dots • Have a print head (or hammer) that consists of pins representing the character or image • The print head prints by striking an ink-soaked cloth ribbon against the paper Dot Matrix Printers
  27. 27. © Oxford University Press 2016. All rights reserved. • The print head is a circular wheel • To print a character, the wheel is rotated in such a way that the character to be printed is positioned just in front of the printer ribbon Daisy Wheel Printers
  28. 28. © Oxford University Press 2016. All rights reserved. • Printing mechanism uses a metal loop or band to produce typed characters • The set of characters is permanently embossed on the band, and this set cannot be changed unless the band is replaced Band Printers
  29. 29. © Oxford University Press 2016. All rights reserved. • High-speed printers in which one typed line is printed at a time • Used in data centers and industrial environments Line Printers
  30. 30. © Oxford University Press 2016. All rights reserved. • Much quieter as their printing heads do not strike the paper • Offer better print quality, faster printing, and the ability to create prints that contain sophisticated graphics • Use either solid or liquid cartridge-based ink, which is either sprayed, dripped, or electrostatically drawn onto the page Advantages  Produce prints of good quality  Noiseless, fast  Can print text in different fonts Disadvantage  Expensive as ink cartridges used by them are costly Non-Impact Printers
  31. 31. © Oxford University Press 2016. All rights reserved. • The print head has several tiny nozzles, also called jets. As the paper moves past the print head, the nozzles spray ink onto it, forming characters and images • Cartridges have to be changed frequently Inkjet Printers
  32. 32. © Oxford University Press 2016. All rights reserved. • Work at very high speeds and produce high-quality text and graphics • A laser beam ‘draws’ the document on a drum which is coated with a photo-conductive material • After the drum is charged , it is rolled in a toner (a dry powder type of ink) • The toner sticks to the charged image on the drum and transferred onto a piece of paper Laser Printers
  33. 33. © Oxford University Press 2016. All rights reserved. Plotters • Used to print vector graphics with high-print quality • Widely used to draw maps, in scientific applications, and in CAD, CAM, and CAE Drum plotters • Used to draw graphics on paper that is wrapped around a drum • Usually used with mainframe and minicomputer systems Flatbed plotters • The paper is spread on the flat rectangular surface of the plotter, and the pen is moved over it • Less expensive, and are used in many small computing systems Plotters

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