Computers: Tools for an Information Age

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ComputersTools for an Information Age

• Chapter 5
• Input and Output The User Connection

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Objectives

• Differentiate among various input devices
• Describe how a scanner works
• Describe how a digital camera works
• Describe the different methods of computer output
• Describe how a monitor works and the
  characteristics that determine quality
• Differentiate among different kinds of printers
• Describe how a laser printer works
• Explain the function of a computer terminal and
  describe the types of terminals

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Input Getting Data from the User to the Computer

• Keyboard
• Pointing devices
• Source data automation

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Keyboard

• Typing area
• Numeric keypad
• Function keys, special keys that issue commands

• Can be unique to an industry
• Keys on McDonalds keyboards represent Big Mac or
  large fries

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Ergonomic Keyboards

• Designed to reduce or minimize repetitive strain
  injury of wrists
• Provide more natural, comfortable position of
  wrists, arms, and hands

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Pointing Devices

• Used to position a pointer on the screen
• Communicate commands to operating system by
  clicking a button
• Common devices
• Mouse
• Devices used in laptops
• Devices used for games
• Others

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Mouse

• Pointing device controls movement of pointer,
  also called mouse pointer

• Mechanical mouse has rubber or metal ball on
  underside

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Mouse

• Optical mouse

• No moving mechanical parts inside
• Senses light to detect mouses movement
• More precise than mechanical mouse
• Connects using a cable, or wireless

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Mouse

• Trackball

• Stationary pointing device with a ball on its top
• To move pointer, rotate ball with thumb, fingers,
  or palm of hand

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Touchpad and Pointing Stick

• Touchpad
• Rectangular pressure-sensitive pad
• Sliding finger across pad moves pointer
• Tapping with finger recognized as click
• Pointing stick
• Small pressure-sensitive post mounted in center
  of keyboard
• Pushing post in any direction moves pointer

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Pointing Devices for Games

• Joystick is vertical lever mounted on a base
• Wheel is steering-wheel-type input device
• Pedal simulates car brakes and accelerator

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Other Pointing Devices

• Touch screen
• Allow user to touch items on screen
• Position of finger on screen determines item to
  be input into system
• Used at kiosks in public places, e.g. malls
• Graphics tablet
• Use pen-like stylus to input data
• Used to create or trace precise drawings

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Source Data Automation

• Use of special equipment to automatically collect
  data at the source
• Magnetic-ink character recognition (MICR)
• Uses a machine to read characters made of
  magnetized particles
• Optical recognition devices
• Uses a light beam to scan data and convert to
  electrical signals, e.g., Scanners
• Bar code readers

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MICR

• Banking industry
• Characters preprinted on lower left-hand side of
  check
• Amount added by MICR inscriber when check is
  cashed

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Optical Recognition - Scanners

• Flatbed scanner
• Typically scans one page at a time
• Can be used to scan large bound documents
• Sheeted scanner
• Motorized rollers feed sheet across scanner head
• Handheld scanner
• Smallest and least accurate

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How does a flatbed scanner work?
Step 1. Document to be scanned is placed face
down on the glass window.
Step 2. Bright light moves underneath scanned
document.
Step 3. Image of the document is reflected into
a series of mirrors.
Step 4. Light is converted to analog electrical
current that is converted to digital signal by an
analog-to-digital converter (ADC).
Step 6. Users can print image, e-mail it,
include it in a document, or place it on a Web
page.
Step 5. Digital information is sent to memory in
the computer to be used by illustration, desktop
publishing, or other software or it is stored on
disk.
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Bar Coder Reader

• Uses laser beams to read bar codes

• Universal Product Code (UPC)
• Identification code that consists of a set of
  vertical lines and spaces of different widths

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Widely Used Bar Codes
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Voice Input
Step 2. An analog-to-digital converter (ADC)
translates sound waves into digital measurements
computer can process. Measurements include pitch,
volume, silences, and phonemes. Phonemes are
sound units such as aw and guh.
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Digital Cameras

• Allows you to take digital pictures

• Images viewable immediately on camera
• Download to computer
• Post pictures to Web

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How does a digital camera work?
Step 1. Point to the image to photograph and
take picture. Light passes into the lens of the
camera.
Step 2. Image is focused on a chip called a
charge-coupled device (CCD).
Step 3. CCD generates an analog signal that
represents the image.
Step 4. Analog signal is converted to digital
signal by analog-to-digital converter (ADC).
Step 5. Digital signal processor (DSP) adjusts
quality of image and usually stores digital image
on miniature mobile storage media in the camera.
Step 6. Images are transferred to a computers
hard disk by plugging one end of the cable into a
camera and the other end into a computer or
images are copied to hard disk from storage media
used in the camera.
Step 7. Using software supplied with the camera,
images are viewed on screen, incorporated into
documents, edited, and printed.
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Digital Cameras

• What is resolution?

• Sharpness and clarity of image
• The higher the resolution, the better the image
  quality, but the more expensive the camera
• Pixel (picture element) is single point in
  electronic image
• Greater the number of pixels, the better the
  image quality

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How resolution affects the quality of an image?
96x96 pixels
128x128 pixels
196x196 pixels
64x64 pixels
48x48 pixels
32x32 pixels
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Video Input

• Process of entering full-motion images into
  computer

• Video capture card is adapter card that converts
  analog video signal into digital signal that
  computer can use

• Digital video (DV) camera records video as
  digital signals

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Video Input

• PC video camera and Web cam

• PC video cameraccDV camera used to capture video
  and still images, and to make video telephone
  calls on Internet
• Also called PC camera
• Web cam c cvideo camera whose output displays
  on a Web page

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Output Information for the User

• Monitors
• Printers
• Music output
• Voice output
• Microform

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Computer Screen Technology

• Screen is part of computers monitor
• Screen output known as soft copy
• Intangible and temporary
• Common forms
• Cathode ray tube (CRT)
• Flat-panel screens

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CRT Monitor

• Contains cathode-ray tube (CRT)

• Screen coated with tiny dots of phosphor material
• Each dot consists of a red, blue, and green
  phosphor
• Common sizes are 15, 17, 19, 21, and 22 inches
• Viewable size is diagonal measurement of actual
  viewing area

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How does video travel in a CRT monitor?

• Video card (also called a graphics card) converts
  digital output from computer into analog video
  signal

Step 5. Electron guns fire the three color
signals to the front of the CRT.
Step 1. The processor sends digital video data to
the video card.
Step 3. The analog signal is sent through a cable
to the CRT monitor.
Step 4. The CRT monitor separates the analog
signal into red, green, and blue signals.
Step 6. An image is displayed on the screen when
the electrons hit phosphor dots on the back of
the screen.
Step 2. The video cards digital-to-analog
converter (DAC) converts the digital video data
to an analog signal.
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Factors Affecting Performance

• Scan rate
• The frequency with which the image is refreshed
• Resolution (clarity) of screen
• Measured in pixels (picture elements)
• The more pixels, the higher the resolution
• Graphics standards
• Dot pitch
• The amount of space between dots
• The smaller the dot pitch, the sharper the image
• Video memory
• A high-speed form of RAM installed on graphics
  card

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Graphic Standards

• Agree on resolutions, colors, other issues
  related to displaying graphics
• Super Video Graphics Adapter (SVGA) is most
  common standard
• Provides 800 (horizontal) x 600 (vertical) pixels
  on the display
• Other varieties of SVGA exist
• XGA 1024x768, SXGA 1280x1024, UXGA 1600x1200
• Support 16 million colors
• The number of colors that can be displayed
  depends on amount of video memory

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Flat-Panel Screens

• Liquid crystal display (LCD)
• Originally used for laptops, but making their way
  to desktop computers
• Very thin (only a few inches)
• Produce sharper text images than CRTs
• Easier on eyes than CRTs

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LCD Technologies

• Active-matrix
• Uses many thin-film transistors (TFT)
• Produces brighter image and can be viewed from
  wider angles
• Passive-matrix
• Uses fewer transistors
• Cheaper and uses less power
• Gas plasma
• Supports very large displays
• Has brilliant color display
• Viewable at very wide angles

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Display Devices
Step 2. As light passes through liquid crystal,
electrical charge causes some of the cells to
twist, making light waves bend as they pass
through color filter.
Step 1. Panel of fluorescent tubes emits light
waves through polarizing glass filter, which
guides light toward layer of liquid crystal cells.
Liquid crystal cells
Step 3. When light reaches second polarizing
glass filter, light is allowed to pass through
any cells that line up at the first polarizing
glass filter. Absence and presence of colored
light cause image to display on the screen.
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Printers

• Produce information on paper output
• Printed output known as hard copy
• Orientation settings
• Portrait - vertical alignment
• Landscape - horizontal alignment
• Two ways of printing
• Impact printer
• Nonimpact printer

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Impact Printers

• Physical contact with paper required to produce
  image
• Dot-matrix printer
• Has print head consisting of one or more columns
  of pins
• Pins form characters and images as pattern of dots

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Nonimpact Printers

• Places an image on a page without physically
  touching the page
• Laser printer
• Uses light beam to help transfer images to paper
• Produces high-quality output at very fast speeds
• Ink-jet printer
• Sprays dots of ink from jet nozzles
• Can print in both black/white and color
• Requires high-quality paper so ink does not smear
• Less expensive than laser printers

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How does a laser printer work?
Step 2. Rotating mirror deflects low-powered
laser beam across surface of drum.
Step 1. After user sends an instruction to print
a document, drum rotates as gears and rollers
feed sheet of paper into printer.
Step 5. Set of rollers uses heat and pressure to
permanently fuse toner to paper.
Step 4. As drum continues to rotate and press
against paper, toner transfers from drum to paper.
Step 3. Laser beam creates a charge that causes
toner to stick to drum.
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Music Output

• Speakers placed on side of monitor
• Powered sub-woofers produce low-frequency sounds

• Musical Instrument Digital Interface (MIDI)
• Rules for connecting musical instruments,
  synthesizers, and computers
• Allows users to set up home studios that rival
  capabilities of professional recording studios

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Voice Output

• Voice synthesizers convert data to vocalized
  sounds
• Two approaches
• Synthesis by analysis - analyzes actual human
  voice, records and plays back as needed
• Synthesis by rule - uses linguistic rules to
  create artificial speech
• Used in automated telephone-based customer
  service applications
• Useful when an inquiry would be followed by a
  short reply, such as a balance inquiry

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Terminals

• Combine input and output capabilities
• Dumb terminal
• Keyboard for input and monitor for output
• No processing capability
• Intelligent terminal
• Has limited memory and a processor

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Terminals

• Point-of-sale (POS) terminal
• captures retail sales data when transaction takes
  place
• Automatic teller machine (ATM)
• self-service banking machine that connects to
  host computer through network