Chapter 6 Input and Output Devices

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Chapter 6 Input and Output Devices

• 6.1 Input Devices 104
• 6.2 Output Devices 118

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6.1 Input Devices (1)
Chapter 6 I/O Devices

• 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

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6.1 Input Devices (2)
Chapter 6 I/O Devices

• Input devices may be categorised into eight
  groups
• Keyboard
• Pointing Devices
• Scanner and Reader
• Voice Input
• Digital Camera
• Video Input
• Authentication Devices
• Data-logger

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6.1.1 Keyboard (1)
6.1 Input devices

• 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

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6.1.1 Keyboard (2)
6.1 Input devices

• 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

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6.1.2 Pointing Devices (1)
6.1 Input devices

• 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

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6.1.2 Pointing Devices (2)
6.1 Input devices

• 1. Mouse
• 2. Trackball
• 3. Joystick and Wheels
• 4. Graphic Tablets
• 5. Touch Screen
• 6. Touchpad
• 7. Pointing Stick

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6.1.2.1 Mouse (1)
6.1.2 Pointing Devices

• Normally with two buttons and a small wheel
• Moved under users 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.

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6.1.2.1 Mouse (2)
6.1.2 Pointing Devices

• 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

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6.1.2.2 Trackball
6.1.2 Pointing Devices

• 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

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6.1.2.3 Joystick and Wheel
6.1.2 Pointing Devices

• 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

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6.1.2.4 Graphic tablet
6.1.2 Pointing Devices

• 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

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6.1.2.5 Touch screen
6.1.2 Pointing Devices

• 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

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6.1.2.6 Touchpad
6.1.2 Pointing Devices

• 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

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6.1.2.7 Pointing stick
6.1.2 Pointing Devices

• 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

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6.1.3 Scanners/Reading Devices
6.1 Input Devices

• 1. Image Scanner
• 2. OCR Reader
• 3. OMR Reader
• 4. Barcode Reader
• 5. MICR Reader

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6.1.3.1 Image Scanner
6.1.3 Scanner/Reader

• 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

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6.1.3.2 OCR Reader
6.1.3 Scanner/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

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6.1.3.3 OMR Reader
6.1.3 Scanner/Reader

• Optical Mark Recognition (OMR) Reader
• detects pencil mark on paper
• Commonly used in marking multiple-choice answer
  sheets

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6.1.3.4 Bar code reader
6.1.3 Scanner/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

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6.1.3.5 MICR Reader
6.1.3 Scanner/Reader

• Magnetic Ink Character Recognition (MICR) Reader
• Read text printed with magnetised ink
• Exclusively used by bank for cheque processing

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6.1.4 Voice Input
6.1 Input Devices

• 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

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6.1.5 Digital Camera
6.1 Input Devices

• 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

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6.1.6 Video Input (1)
6.1 Input Devices

• 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

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6.1.6 Video Input (2)
6.1 Input Devices

• 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

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6.1.7 Authentication Devices
6.1 Input 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

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6.1.7.1 Magnetic Card Reader
6.1.7 Authentication Devices

• 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

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6.1.7.2 Smart Card Reader
6.1.7 Authentication Devices

• 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

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6.1.7.3 Fingerprint Scanners
6.1.7 Authentication Devices

• 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

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6.1.7.4 Other biometric authentication devices
6.1.7 Authentication Devices

• Biometric authentication devices
• Fingerprint Scanner
• Face Recognition System
• Hand Geometry Detection
• Voice Recognition
• Iris Pattern Matching

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6.1.8 Data-loggers
6.1 Input Devices

• 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

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6.2 Output Devices
Chapter 6 I/O Devices

• 1. Display Devices
• 2. Printers
• 3. Speakers and Headset

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6.2.1 Display Devices (1)
6.2 Output Devices

• 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

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6.2.1 Display Devices (2)
6.2 Output Devices

• Display devices
• Display information visually
• Softcopy
• Data is lost when the machine is powered off

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6.2.2 Display Devices (3)
6.2 Output Devices

• 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

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6.2.3 Printers (1)
6.2 Output Devices

• 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

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6.2.3 Printers (2)
6.2 Output Devices

• 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

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6.2.3.1 Dot-matrix Printer
6.2.3 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

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6.2.3.2 Ink-jet Printer
6.2.3 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 )

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6.2.3.3 ?????
6.2.3 Printer

• 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

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6.2.3.4 Thermal Printers
6.2.3 Printer

• 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

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6.2.3.5 Plotters/Large-format printers
6.2.3 Printer

• 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

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6.2.3 Speaker and Headsets
6.2 Output Devices

• 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