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Chapter 6

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  • 1. Chapter 6 Input and Output Devices 6.1 Input Devices 104 6.2 Output Devices 118
  • 2. 6.1 Input Devices (1)
    • Input Devices
      • Peripheral devices for entering data, instructions and user responses
      • Produce machine readable data
    • Online Operations
      • Data are directly input into the memory of the computer
    • Offline Operations
      • Punched cards were prepared with a keypunching machine before they are inputted into the computer
    Chapter 6 I/O Devices
  • 3. 6.1 Input Devices (2)
    • Input devices may be categorised into eight groups:
      • Keyboard
      • Pointing Devices
      • Scanner and Reader
      • Voice Input
      • Digital Camera
      • Video Input
      • Authentication Devices
      • Data-logger
    Chapter 6 I/O Devices
  • 4. 6.1.1 Keyboard (1)
    • Standard QWERTY Keyboard
      • Some Extra keys
        • like arrow key, function keys etc
      • Enter Key
        • Use in issuing command
      • Num-Lock and Insert Key
        • Toggle between 2 states
      • Special Keys (Shift, Ctrl and Alt)
        • Use with other keys to increase the function of a keyboard
    6.1 Input devices
  • 5. 6.1.1 Keyboard (2)
    • Cordless keyboard
      • Data is sent through radio or infrared radiation
      • So, requires a receiver
        • which is connected to a port on the system unit
      • Require a battery to operate
    • Non-standard keyboards
      • Point-of-sales (POS) terminals of supermarkets
        • to speed up data input
      • Keypads in automatic teller machines (ATM)
        • to limit users to certain keys only
    6.1 Input devices
  • 6. 6.1.2 Pointing Devices (1)
    • A pointing device
      • An input device
      • Controlling a pointer on the screen
        • A pointer can be
          • an arrow, an I-beam or a pointing hand
      • Used in Graphical user interface (GUI)
        • clicking buttons
        • selecting menu items
        • moving the insertion point
        • selecting text
        • drawing pictures
        • accepting handwriting script
          • which is later converted into typescript
    6.1 Input devices
  • 7. 6.1.2 Pointing Devices (2)
    • 1. Mouse
    • 2. Trackball
    • 3. Joystick and Wheels
    • 4. Graphic Tablets
    • 5. Touch Screen
    • 6. Touchpad
    • 7. Pointing Stick
    6.1 Input devices
  • 8. 6.1.2.1 Mouse (1)
      • Normally with two buttons and a small wheel
      • Moved under user’s palm
    • Mechanical mouse
      • Has a ball on its underside
      • A circuit converts movement into electrical signals
    • Optical mouse
      • Emits light and senses the reflected light to detect the mouse's movement.
      • Does not require cleaning, but
      • More expensive.
    6.1.2 Pointing Devices
  • 9. 6.1.2.1 Mouse (2)
    • Movement of mouse
      • Relative
        • The screen pointer moves from its current location.
      • Work by the point-and-click principle
    • Cordless mouse
      • Battery-powered
      • Use radio or infrared radiation to communicate with the system unit
    6.1.2 Pointing Devices
  • 10. 6.1.2.2 Trackball
      • An upside-down mechanical mouse
      • To control the screen pointer, no need to move the device
      • Rotate the ball with a finger
      • Requires frequent cleaning
    6.1.2 Pointing Devices
  • 11. 6.1.2.3 Joystick and Wheel
    • Joystick
      • used in computer games
      • consists of a vertical lever mounted on a base and some buttons
      • The lever allows movement in different directions
      • Buttons activate actions
        • e.g. jumping and firing.
    • Wheel
      • Control vehicle in driving simulation software
      • Sometimes include foot pedals for acceleration and braking actions
    6.1.2 Pointing Devices
  • 12. 6.1.2.4 Graphic tablet
      • also called digitiser
      • flat rectangular electronic board
      • used with a pen or cursor
    • Movement of the pen
      • Absolute
      • The x-y coordinates of the screen and the graphic tablet match with each other
    • Handwriting Recognition software
      • Inputting Chinese characters
      • translate scripts drawn on the screen into character codes
    6.1.2 Pointing Devices
  • 13. 6.1.2.5 Touch screen
      • Pressure-sensitive display
      • Allows selecting option with fingers
      • Suitable for small amount of data input
      • Examples
        • Kiosks located in stores, museums and airports
        • Modern pay-phone system uses touch screen to replace physical numeric keypads
      • Handheld computers (PDA) and tablet PC
        • Without keyboard or mouse
        • Mainly use pressure-sensitive computer screen
        • Handwriting recognition software translates handwritten letters and symbols into text
    6.1.2 Pointing Devices
  • 14. 6.1.2.6 Touchpad
      • Built-in pointing device of some notebook computers
      • Sensitive to pressure and motion
      • With buttons similar to the mouse buttons
      • May tap the touchpad to imitate mouse click
    6.1.2 Pointing Devices
  • 15. 6.1.2.7 Pointing stick
      • Built-in pointing device of some notebook computers
      • Look like a pencil eraser
      • Located between keys on the keyboard
      • Movement is controlled by a finger
    6.1.2 Pointing Devices
  • 16. 6.1.3 Scanners/Reading Devices
    • 1. Image Scanner
    • 2. OCR Reader
    • 3. OMR Reader
    • 4. Barcode Reader
    • 5. MICR Reader
    6.1 Input Devices
  • 17. 6.1.3.1 Image Scanner
    • Image Scanner
      • Light-sensitive input device
      • Reads printed text and photos by
        • sending a bright light on the document and detecting the light reflected from the document
      • Convert the document into digital images
    • Optical Character Recognition (OCR)
      • Analyse digital images
      • Translate the results into text characters
        • which can be edited by a word processor
    6.1.3 Scanner/Reader
  • 18. 6.1.3.2 OCR Reader
    • OCR reader
      • range from large machines to handheld wands
      • Some OCR devices can only read the OCR fonts
      • OCR-A is the widely used OCR font
    6.1.3 Scanner/Reader
  • 19. 6.1.3.3 OMR Reader
    • Optical Mark Recognition (OMR) Reader
      • detects pencil mark on paper
      • Commonly used in marking multiple-choice answer sheets
    6.1.3 Scanner/Reader
  • 20. 6.1.3.4 Bar code reader
    • Bar code
      • consists of a set of parallel lines and spaces of different widths
      • is an identification code, commonly used in
        • libraries, post offices, publishing companies, manufacturers etc.
    • Bar code readers
      • Highly accurate and fast
      • Printed with the letters that represent the code
        • for manual input when the bar code cannot be recognised
    6.1.3 Scanner/Reader
  • 21. 6.1.3.5 MICR Reader
    • Magnetic Ink Character Recognition (MICR) Reader
      • Read text printed with magnetised ink
      • Exclusively used by bank for cheque processing
    6.1.3 Scanner/Reader
  • 22. 6.1.4 Voice Input
    • Voice input
      • Input data by speaking to a microphone
      • Sound card converts sound waves into digital form
    • Voice recognition
      • Distinguishes spoken words
      • Matches the input wave patterns with the patterns stored inside the computer
      • Useful for physically handicapped people
    6.1 Input Devices
  • 23. 6.1.5 Digital Camera
    • Digital Camera
      • Take still pictures
      • Produce bitmap images, e.g. JPG
      • Storing in flash memory/card
      • Transferring to computer through card reader
      • The storage media can be reused
    6.1 Input Devices
  • 24. 6.1.6 Video Input (1)
    • 1. Video capture card
      • Converts image in analog form into digital form
    • 2. DV camera
      • also called camcorder
      • Records videos as digital signals
      • Signals transmitted directly to a computer or
      • stored in tapes
    6.1 Input Devices
  • 25. 6.1.6 Video Input (2)
    • 3. Web cam
      • Capture motions and send video signals to computer directly
      • Cannot be used alone (must be used with computer)
        • Commonly used in videoconferencing.
    • Videoconferencing
      • allows geographically separated people to meet one another, via Internet to transmit audio and video data.
      • Besides the videoconferencing software, user need
        • microphone
        • speaker and
        • Web cam/DV camera
    6.1 Input Devices
  • 26. 6.1.7 Authentication Devices
    • Authentication Devices
      • Verify the identity of a user
      • Input the identification code into the computer
    • 1. Magnetic Card Reader
    • 2. Smart Card Reader
    • 3. Fingerprint Scanner
    • 4. Other biometric Devices
    6.1 Input Devices
  • 27. 6.1.7.1 Magnetic Card Reader
    • Magnetic Card Reader
      • Reads the magnetic stripe on the back of a bank card
      • The magnetic stripe stores the customer's account number only
      • Updating is done at the bank's computer
    6.1.7 Authentication Devices
  • 28. 6.1.7.2 Smart Card Reader
    • Smart Card
      • embedded with a microprocessor and memory
      • Holding much more information than a magnetic card
    • A smart card can be programmed
      • If wrong passwords are entered several times, it would be self-destructed
      • More secure
      • Can be used in financial transactions, like
        • stored-value ticket for public transport, where it is loaded with digital money
    6.1.7 Authentication Devices
  • 29. 6.1.7.3 Fingerprint Scanners
    • Fingerprint Scanners
      • Biometric authentication device
      • Captures curves and indentations of a fingerprint
      • Sends the data into a computer for verification.
      • Some notebook computer uses this security technique to protect the computer
    6.1.7 Authentication Devices
  • 30. 6.1.7.4 Other biometric authentication devices
    • Biometric authentication devices
      • Fingerprint Scanner
      • Face Recognition System
      • Hand Geometry Detection
      • Voice Recognition
      • Iris Pattern Matching
    6.1.7 Authentication Devices
  • 31. 6.1.8 Data-loggers
    • Data-loggers
      • used in some school laboratories
      • collect and analyse data
      • replace some traditional apparatus
      • Consists of one or more sensors, such as
        • temperature sensor
        • pressure sensor
        • heartbeat rate sensor
      • Special data analysis software is needed
        • to display the captured data in digits, tables or graphs
    6.1 Input Devices
  • 32. 6.2 Output Devices
    • 1. Display Devices
    • 2. Printers
    • 3. Speakers and Headset
    Chapter 6 I/O Devices
  • 33. 6.2.1 Display Devices (1)
    • Visual Display Unit (VDU)
      • Most frequently used output device
      • Monitor is a separate unit
    • Two technologies for VDU:
      • Cathode Ray Tubes (CRT)
        • Produce images as electrons strike on a fluorescent screen
        • Operate at very high voltage
        • Require many electronic components.
      • Liquid Crystal Display (LCD)
        • Thin and light, known as flat-panel display
        • used in notebook computers, tablet PC, handheld computers and mobile devices
    6.2 Output Devices
  • 34. 6.2.1 Display Devices (2)
    • Display devices
      • Display information visually
    • Softcopy
      • Data is lost when the machine is powered off
    6.2 Output Devices
  • 35. 6.2.2 Display Devices (3)
    • Data projector
      • uses strong light beams to project images on a screen
      • Commonly used in classrooms to facilitate presentation.
    • Data projectors are of two types:
      • Liquid Crystal Display (LCD) projector
      • Digital Light Processing (DLP) projector
        • uses tiny mirrors to reflect light,
        • giving brighter, more colourful images
        • and usually more durable
    6.2 Output Devices
  • 36. 6.2.3 Printers (1)
    • Printer
      • Printing texts and graphics on paper or other physical medium , e.g. transparency film
      • Hardcopy
        • exists physically
        • more permanent than softcopy
    • Printers can be divided into two types:
      • Impact printers
      • Non-impact printers
    6.2 Output Devices
  • 37. 6.2.3 Printers (2)
    • Printers can be divided into two types:
      • Impact printers
    • 1 Dot Matrix Printer
      • Non-impact printers
    • 2 Inkjet Printer
    • 3 Laser Printer
    • 4 Thermal Printer
    • 5 Plotter/Large Format Printer
    6.2 Output Devices
  • 38. 6.2.3.1 Dot-matrix Printer
    • Dot-matrix printer
      • Typical impact printer
      • Characters are formed by dots:
        • A matrix of pins strike an inked ribbon against the paper.
      • Suitable for several layered paper
      • Use continuous-form paper with holes on both sides
    • Disadvantages
      • Slow and Noisy
    6.2.3 Printer
  • 39. 6.2.3.2 Ink-jet Printer
    • Ink-jet printer
      • Non-impact printer
      • Spraying tiny ink drops onto a page
      • High quality and low price
    • Disadvantages:
      • 1. The ink is soluble
      • 2. Need to wait until the ink is dried completely.
      • 3. Ink left behind will dry out and block the nozzle
      • 4. High running cost (Ink is expensive )
    6.2.3 Printer
  • 40. 6.2.3.3 激光打印機
    • Laser Printers
      • Non-impact printer
      • Using laser beam to create images onto a drum
      • Similar to photocopying machine
      • Expensive, but
      • Fast, high-quality and low running cost
    • Colour laser printer
      • Mixing toners of several colours to produce many different colours
    6.2.3 Printer
  • 41. 6.2.3.4 Thermal Printers
    • Thermal printers are of three types:
      • Direct thermal printer
        • Direct thermal printer produces images as a
        • Heating a heat-sensitive paper
        • Used in supermarkets for price label
        • Will never run out of ink
      • Thermal wax transfer printer
      • Dye sublimation printer.
    • Thermal printers are not very popular
      • Consumables (the wax-cartridges and the dyed ribbons) are quite expensive
    6.2.3 Printer
  • 42. 6.2.3.5 Plotters/Large-format printers
    • Pen plotter
      • Consists of several colour pens
      • The pens move up and down as the paper rolls
      • Images are drawn by a pen plotter on a paper
      • Mainly used in blueprints, maps and circuit
    • Large-format printer
      • Larger ink-jet printer
      • Handle paper with widths up to 60 inches
      • Used in producing posters, signs and large drawings
    6.2.3 Printer
  • 43. 6.2.3 Speaker and Headsets
    • Audio output device
      • Enables output from a computer to be heard
      • The two commonly used audio output devices
        • speakers
        • headsets
      • Both are connected to the sound card
    6.2 Output Devices