Introduction to Computers

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Introduction to Computers

• Lesson 2-3

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Keyboard

• Primary input device for entering text and numbers

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Keyboard

• Alphanumeric keys
• Modifier keys (Alt, Ctrl, Shift)
• Numeric keypad
• Function keys
• Cursor-movement keys
• Special-purpose keys (ESC, Pause, Start,)

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The Keyboard
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How the Computer Accepts Input from the Keyboard

• Keyboard controller
• Keyboard buffer
• Scan code
• Interrupt request
• Repeat rate

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From the Keyboard to the Computer
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The Mouse

• An input device that rolls around on a flat
  surface and controls the pointer

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Pointer

• Also called the mouse pointer
• An on-screen object (usually an arrow) for
  selecting text accessing menus and interacting
  with programs, files, or data

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Examples of Mouse Maneuvers

• Pointing
• Clicking
• Double-clicking
• Dragging
• Right-clicking

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Mouse Variants

• Trackball
• Trackpad, also called a touchpad
• Joystick, also called an integrated pointing
  device, 3-D point stick, or TrackPoint
  (space-saving )

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Review Questions

• What are the kinds of keys on a keyboard?
• What is a mouse?
• What are examples of mouse maneuvers?
• What are the three mouse variants?

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Alternative Input Devices

• Devices for the hand
• Optical devices
• Audiovisual devices

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Input Devices for the Hand

• Pen, sometimes called a stylus
• Touch screen
• Game controller

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Optical Input Devices

• Bar code reader
• Image scanner and optical character recognition
  (OCR)

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Audiovisual Input Devices

• Microphones and Speech Recognition Software
  sound card analog digital audio
  recording software
• Video Input (video-conferencing) PC video
  camera video capture card VCRs PC
• Digital Cameras

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Review Questions

• What are the three hand input devices?
• What is another term for pen?
• What are the two optical input devices?
• What are the two video input devices?

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Output -- Monitors

• Cathode ray tube (CRT) big, requires a
  lot of power to run
• Flat-panel. Most common flat-panel is the liquid
  crystal display (LCD) monitor difficult to
  see in bright light limited viewing angle

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Monitor Categories Based on Color Display

• Monochrome One color on a black background
• Grayscale Shades of gray on a white or off-white
  background
• Color From 16 to 16 million unique colors

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CRTs

• In CRT monitors, electrons are fired at phosphor
  dots on the screen.
• Pixel, short for picture element, is the smallest
  number of phosphor dots that the electron gun
  inside the monitor can focus on
• color CRTs, each pixel contains a red, green, and
  blue dot.

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Two Main LCD Categories

• Passive matrix LCDgrid the location of each
  pixeluses a transistor for each row and column
  of pixels.
• Active matrix LCDuses a transistor for each
  pixel on the screen.
• Thin-film transistor displays use multiple
  transistors for each pixel.

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Other Kinds of Monitors

• Plasma/gas plasma displayCreated by sandwiching
  a special gas between two sheets of glass.
• Paper-white displayhigh contrast between the
  monitors white background and text or graphics
• Electroluminescent (ELD) displayUse a
  phosphorescent film held between two sheets of
  glass

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Four Things to Consider When Monitor Shopping

• Size
• Resolution
• Refresh rate
• Dot pitch

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The Video Controller

• Intermediary device between the CPU and the
  monitor
• Controls how things look on-screen
• Built-in video RAM
• Built-in microproessor

(VGA card)(super)SVGA
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Digital Light Projectors

• Connects to a computer and is used to project
  images on a large screen
• LCD-based projectors room to be darkened
• DLP digital light processing technology use
  a microchip containing tiny mirrors to produce
  very sharp, bright images.

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Sound Card

• Translates digital sounds into the electric
  current that is sent to the speakers
• The moving speaker cone creates pressure
  vibrations in the air -- sound

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How a Sound Card Works
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Printers

• Output hard copy
• Impact Creates an image by using pins or
  hammers to press an inked ribbon against the
  paper. Most common impact printer is the dot
  matrix.
• Nonimpact ink jet and laser printers

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Dot Matrix Printer Terms

• Print head
• Characters per second (cps)

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Dot Matrix Printer
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Ink Jet Printer

• Creates an image directly on the paper by
  spraying ink through tiny nozzles

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Inkjet Printer
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Laser Printer

• A laser is at the heart of this printer that uses
  technology similar to that in photocopiers

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Laser Printer
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Four Things to Consider When Printer Shopping

• Image quality, measured in dots per inch (dpi)
• Speed, measured in pages per minute (ppm) or
  lines per minute (lpm)
• Initial cost
• Cost of operation

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Review Questions

• What are the two categories of printers?
• What are the four things to consider when
  shopping for a printer?
• How does an ink jet printer work?
• How does a laser printer work?