Docstoc

TDC 311 Input Output Technology

Document Sample
TDC 311 Input Output Technology Powered By Docstoc
					                            Chapter Goals
• Describe common concepts of text and image
  representation and display including digital
  representation of grayscale and color, bitmaps, and
  image compression techniques
• Describe the characteristics and implementation
  technology of video display devices
• List and describe the three predominant manual
  input technologies

Systems Architecture, Fifth Edition                 2
        Chapter Goals (continued)
• Understand printer characteristics and technology
• Describe various types of optical input devices
  including mark sensors, bar code readers,
  scanners, and digital cameras
• Identify the characteristics of audio I/O devices,
  and explain how they operate



Systems Architecture, Fifth Edition                    3
Systems Architecture, Fifth Edition   4
  Basic Print and Display Concepts
• Share many features
      – Character representation methods
      – Measurement systems
      – Methods of generating color




Systems Architecture, Fifth Edition        5
                 Matrix-Oriented Image
                     Composition
• We’ll take a look at:
      –   Display surfaces
      –   Fonts
      –   Color
      –   Numeric pixel content




Systems Architecture, Fifth Edition      6
                            Display Surface
• Commonly used: paper, cathode ray tubes, flat panel
  displays
• Divided into rows and columns similar to a large matrix
      – Each cell (pixel) represents one simple component of an
        image
• Resolution
      – Number of pixels displayed per linear measurement unit
      – Stated in dots per inch (dpi)



Systems Architecture, Fifth Edition                               7
Systems Architecture, Fifth Edition   8
                                      Fonts
• Collection of characters of similar style and
  appearance
• Usually measured in points (one seventy-second
  of an inch), which refers to height of characters




Systems Architecture, Fifth Edition                   9
                                      Color
• RGB (additive colors)
      – Generates color by mixing red, green, and blue
• CMY (subtractive colors)
      – Generates color using cyan (absence of red),
        magenta (absence of green), and yellow (absence
        of blue)
• CMYK color
      – Four-dye scheme using a separate black dye (K)

Systems Architecture, Fifth Edition                       10
              Numeric Pixel Content
• Bitmap
      – Stored set of numeric pixel descriptions
• Monochrome display
      – Displays one of two colors
      – Requires only one bit per pixel
• Grayscale display
      – Displays black, white, and shades of gray


Systems Architecture, Fifth Edition                 11
              Numeric Pixel Content
• Palette
      – A table of colors
      – Number of bits used to represent each pixel
        determines table size
• Dithering
      – Generates color approximations by placing small
        dots of different colors in an interlocking pattern
      – Half-toning (grayscale dithering)

Systems Architecture, Fifth Edition                           12
    Image Storage Requirements
• Depends on number of bits that represent each
  pixel and on image height and width in pixels
• Can be reduced with bitmap compression
      – Graphics Interchange Format (GIF)
      – Joint Photographic Experts Group (JPEG)
      – Moving Pictures Experts Group (MPEG)
• All above compression methods are lossy,
  resulting in some loss of image quality

Systems Architecture, Fifth Edition               13
   Image Description Languages
              (IDL)
• Address drawbacks of bitmaps (large size and
  device dependence) by storing images compactly
• Can represent image components in several ways
      – Embedded fonts
      – Vectors, curves, and shapes
      – Embedded bitmaps



Systems Architecture, Fifth Edition                14
Systems Architecture, Fifth Edition   15
     Adobe PostScript and Portable
          Document Format
PostScript                            PDF
• Used in printing and                • Ability to distribute
  publishing and as graphic             compressed documents
  file interchange format and           with complete authorial
  embedded printer                      control over exact format of
  technology                            the printed and displayed
• Lacks features needed to              document, regardless of end
  generate and manage                   user’s specific computer,
  documents as an integrated            OS, or printer
  whole

Systems Architecture, Fifth Edition                               16
                             Video Display
• Character-oriented video display terminals
  (VDTs)
• Video controllers
• Video monitors




Systems Architecture, Fifth Edition            17
            Character-Oriented VDTs
• Integrated keyboard and video display surface
• VDTs
      – Most common form of video display in 1970s and
        much of 1980s (until PCs)
• Network computers or thin clients
      – New class of VDT in 1990s
      – Limited processing capabilities


Systems Architecture, Fifth Edition                      18
Systems Architecture, Fifth Edition   19
Systems Architecture, Fifth Edition   20
                        Video Controller
• Enables communication between computer system
  and monitor
      – Accepts commands and data transmitted via a bus
        from the CPU
      – Generates TV-style analog video signal, which is
        transmitted to the monitor
• Refresh cycle and refresh rate; video RAM; dual
  porting; graphics accelerators

Systems Architecture, Fifth Edition                        21
A video controller
contains RAM, a
microprocessor, and
embedded software.


 Systems Architecture, Fifth Edition   22
                          Video Monitors
• Separate from keyboards
• Common types
      – Cathode ray tubes (CRTs)
      – Liquid crystal displays (LCDs)
      – Plasma displays




Systems Architecture, Fifth Edition        23
                                      CRT
• Enclosed vacuum tube; electron beam is focused
  toward front surface of the tube, which is coated in
  phosphor
• Technology relatively old; has disadvantages
      – Physical size and weight
      – Power consumption




Systems Architecture, Fifth Edition                 24
                                      LCD
• Contains matrix of liquid crystals sandwiched
  between two polarizing filter panels
• Active and passive matrix displays
• Manufactured with thin film transistor (TFT)
  technology
• Compared with CRTs
      – Less contrast
      – Reduced size, weight, and power consumption
      – Higher cost
Systems Architecture, Fifth Edition                   25
How an LCD works

Systems Architecture, Fifth Edition   26
                         Plasma Displays
• Combine elements of CRT and LCD technology
• Flat panel, active matrix devices
• Actively generate colored light near surface of the
  display; good brightness and viewing
• Require more power than LCDs, less than CRTs
• Shortcomings
      – Limited operational lifetime
      – Larger pixel size reduces comparative image
        quality when viewed from short distances
Systems Architecture, Fifth Edition                   27
Plasma displays have no backlight and no color filters;
each pixel contains a gas that emits ultraviolet light when
electricity is applied.
  Systems Architecture, Fifth Edition                   28
                                      Printers
Impact (dot matrix) •                  Slow, noisy
                    •                  Relatively poor-quality output
                    •                  Inexpensive
Inkjet              •                  Relatively slow
                    •                  Excellent-quality output
Laser                                 • Relatively fast
                                      • Excellent-quality output

Systems Architecture, Fifth Edition                                29
                            Inkjet Printers
• Most common printing technology
• Prints with liquid ink placed directly onto paper
• Uses mechanical movement or heat to force ink
  out of nozzle
• Paper is drawn past moving print head
• Resolution is up to 600 dpi



Systems Architecture, Fifth Edition                   30
An inkjet printer has disposable print cartridges that
contain ink reservoirs, a matrix of ink nozzles, and
electrical wiring and contact points.
 Systems Architecture, Fifth Edition                     31
            Printer Communication
• Impact printers
      – ASCII or Unicode characters
• Inkjet and laser printers
      – Use pixels as fundamental output unit
      – Have relatively large buffers
• IDLs are commonly used to improve printer
  performance


Systems Architecture, Fifth Edition             32
Laser printers operate with an electrical charge and
the attraction of ink to that electrical charge.
Systems Architecture, Fifth Edition                    33
                                      Plotters
• Printers that generate line drawings on wide sheets
  or rolls of paper
• Use inkjet technology
• Ideal for blueprints and other engineering
  drawings
• Also called large format printers



Systems Architecture, Fifth Edition                34
                Manual Input Devices
 Keyboards                       • For entering text and commands
 Pointing devices • For pointing and selecting buttons or
                    menu items
                  • For drawing
                  • For moving the position of cursor
 Input pads                      • For many of same functions as mice
                                 • Also used for signature pads and touch
                                   screens

Systems Architecture, Fifth Edition                                         35
                                  Keyboards
• Translate keystrokes directly into electrical signals
• Generate bit stream outputs (scan code) with a
  keyboard controller
• Can connect to computer in various ways
  (e.g., PS/2, USB, wireless)




Systems Architecture, Fifth Edition                  36
                         Pointing Devices
•   Mouse
•   Trackball
•   Joystick
•   Input pads (e.g., digitizer tablet)
      – Infrared detector
      – Photosensor
      – Pressure-sensitive pad


Systems Architecture, Fifth Edition         37
                Optical Input Devices
• Detect light reflected off a printed surface or
  object into a photosensor
• Categories
      – Mark and pattern sensors
      – Image capture devices




Systems Architecture, Fifth Edition                 38
         Mark Sensors and Bar-Code
                 Scanners
• Mark sensor
      – Scans for light or dark marks at specific locations
        on a page (e.g., standardized multiple-choice test)
• Bar code scanner
      – Detects specific patterns of vertical bars of varying
        thickness and spacing
      – Typically used to track large numbers of inventory
        items

Systems Architecture, Fifth Edition                           39
       Advanced scanning technology can now read
       two-dimensional bar codes.



Systems Architecture, Fifth Edition                40
                        Optical Scanners
• Generate bitmap representations of printed images
• Bright white light shines on the page; reflected
  light is detected by an array of photosensors
• Optical character recognition (OCR) devices
      – Combine optical scanning technology with
        intelligent interpretation of bitmap content




Systems Architecture, Fifth Edition                    41
                         Digital Cameras
• Employ optical scanning technology to capture
  single or still images and store them as raw
  compressed bitmaps




Systems Architecture, Fifth Edition               42
 Portable Data Capture Devices
• Combine a keyboard, mark or bar-code scanner,
  and wireless communications to a wired base
  station or computer system
• Provide rapid data capture (e.g., warehouse
  inventory control, package routing and tracking)




Systems Architecture, Fifth Edition                  43
                      Audio I/O Devices
• Sound: an analog waveform that can be sampled
  and stored as digital data
• Various mathematical transformations convert
  complex sounds to a single numeric representation
• Sampling and playback rely on analog-to-digital
  converters (ADC) and digital-to-analog converters
  (DAC)
• Monophonic versus polyphonic

Systems Architecture, Fifth Edition               44
Purposes of Sound Generation and
           Recognition
• General-purpose sound output (e.g., warnings)
• General-purpose sound input (e.g., digital
  recording for voice email messages)
• Voice command input
• Speech recognition
• Speech generation



Systems Architecture, Fifth Edition               45
                    Speech Recognition
• Conceptually simple, but complicated by speaker
  variability, phoneme transitions and combinations,
  and real-time processing
• Most current systems are speaker dependent
• Digital signal processor (DSP)
      – Specialized to process continuous streams of audio
        or graphical data
      – Commonly embedded in audio and video hardware

Systems Architecture, Fifth Edition                      46
Systems Architecture, Fifth Edition   47
                     Speech Generation
• Audio response unit
      – Generates spoken messages based on textual input
        (e.g., automated call routing)
• Speech synthesis
      – Stores individual phonemes within the system
• General-purpose audio hardware (sound card,
  multimedia controller)


Systems Architecture, Fifth Edition                        48
General-Purpose Audio Hardware
• Typically packaged as an expansion card that
  connects to the system bus of a workstation
• Sound cards include an ADC, DAC, low-power
  amplifier, and connectors (jacks) for microphone,
  speaker, or headphone
• Musical Instrument Digital Interface (MIDI)
      – Compact storage format


Systems Architecture, Fifth Edition                   49
Systems Architecture, Fifth Edition   50
                                      Summary
• Concepts, technology, and hardware used in
  communication between people and computers
      –   Print and display concepts
      –   Video display devices
      –   Printers
      –   Manual input devices
      –   Optical input devices
      –   Audio I/O devices

Systems Architecture, Fifth Edition             51

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:19
posted:5/19/2012
language:English
pages:51
fanzhongqing fanzhongqing http://
About