1 Chapter 7 Input/Output Technology. 2 Systems Architecture Chapter 7 Chapter Goals Describe manual...
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Transcript of 1 Chapter 7 Input/Output Technology. 2 Systems Architecture Chapter 7 Chapter Goals Describe manual...
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Systems Architecture Chapter 7
Chapter Goals
• Describe manual input devices and how they are implemented.
• Explain the characteristics and implementation technology of video display devices.
• Understand printer characteristics and technology.
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Systems Architecture Chapter 7
Chapter Goals
• Identify the characteristics of audio I/O devices, and explain how they operate.
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Systems Architecture Chapter 7
Chapter Topics
• Describes the concepts, technology and hardware used in communication between people and computers.
• Understand the importance of I/O technology.
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Systems Architecture Chapter 7
Manual Input Devices
Keyboard Input
• Keyboard devices translate keystrokes directly into electrical signals.
• A keyboard controller is used to generate bit stream outputs.
• The controller generates a bit stream output according to an internal program or lookup table.
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Systems Architecture Chapter 7
Manual Input Devices
Keyboard Input
• A keyboard controller generates an output called a scan code.
• A scan code is a one or two-byte data element that represents a specific keyboard element.
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Systems Architecture Chapter 7
Manual Input Devices
Pointing Devices
• Mouse• Trackball• Joystick• Digitizer Tablet
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Systems Architecture Chapter 7
Manual Input Devices
Pointing Devices
Translates the spatial position of a pointer, stylus, or other selection device into numeric values within a system of two-dimensional coordinates.
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Systems Architecture Chapter 7
Manual Input Devices
Mouse – a pointing device that is moved on a flat surface such as a table, desk or rubber pad.
Trackball – a mouse with the roller ball on the top. The roller ball is moved by the fingertips, thumb or palm of the hand.
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Systems Architecture Chapter 7
Manual Input Devices
Joystick – used as an input device with computer games.
Digitizer Tablet – uses a pen, or stylus, and a digitizing tablet. The tablet is sensitive to the placement of the stylus at any point on its surface.
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Systems Architecture Chapter 7
Basic Concepts of Print and Display• Matrix-Oriented Image Composition
– Fonts– Color– Pixel Content
• Image Storage Requirements• Image Description Languages
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Systems Architecture Chapter 7
Basic Concepts of Print and Display
Matrix-Oriented Image Composition
• Display surfaces can be divided into rows and columns similar to a large table or matrix.
• Each cell in the table represents one component of the image.
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Systems Architecture Chapter 7
Basic Concepts of Print and DisplayMatrix-Oriented Image Composition
• One of the cells is a pixel.
• The resolution of the display is the number of pixels displayed per linear measurement unit.
• Resolution is stated in dots per inch(dpi).
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Systems Architecture Chapter 7
Basic Concepts of Print and Display
• Font – a collection of characters of similar style and appearance.
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Systems Architecture Chapter 7
Basic Concepts of Print and DisplayColor
• For video displays, color is generated directly by the display device.
• The video display industry has used red, green and blue as primary colors.
• A video display that generates color uses mixtures or these colors.
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Systems Architecture Chapter 7
Basic Concepts of Print and DisplayColor
• For print, color is light frequency reflected from the paper.
• The printing industry generates color using the inverse of the primary video display colors. (subtractive color)
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Systems Architecture Chapter 7
Basic Concepts of Print and DisplayPixel Content
• Pixel content must be described numerically.• A stored set of numeric pixel descriptions is
called a bit map.• A palette is a table of colors.• Color can also be produced using dithering.
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Systems Architecture Chapter 7
Basic Concepts of Print and DisplayImage Storage Requirements
• Image storage requirements apply to images stored in primary and secondary storage, and to buffers used in I/O devices.
• Image storage requirements can be reduced with image compression techniques.
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Systems Architecture Chapter 7
Basic Concepts of Print and DisplayImage Storage Requirements
Compression Techniques:• Graphics Interchange Format (GIF)• Joint Photographic Experts Group
(JPEG)• Moving Pictures Experts Group (MPEG)
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Systems Architecture Chapter 7
Basic Concepts of Print and DisplayImage Description Languages
• Use a symbolic language to describe primitive image components.
• Can use a vector list .• Describe the image components that are
straight-line segments or can be built from segments.
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Systems Architecture Chapter 7
Video Display
• Character-Oriented Video Display Terminals• Graphic Video Display Devices
– CRTs– Flat Panel Displays
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Systems Architecture Chapter 7
Video Displays
Character-Oriented Video Display Terminals• Commonly used during 1970s and 1980s.
• Terminal – consist of an integrated keyboard and television screen.
• Used today primarily in systems such as retail checkout counters and factory floor environments.
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Systems Architecture Chapter 7
Video Display
Graphic Video Display Devices
• Used for displaying diagrams such as construction blueprints, wireframe models, writing diagrams and to produce mathematical graphs.
• By the mid-1980s monitors were manufactured.
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Systems Architecture Chapter 7
Video Display
• Monitors operate as independent devices under control of a video controller attached to the system bus.
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Systems Architecture Chapter 7
Video Display
CRT
• Current monitors are implemented using cathode ray tubes.
• A CRT is an enclosed tube.• An electron gun in the rear of the tube
generates a stream of electrons.• Pixel illumination is controlled by pulsing the
electron beam.
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Systems Architecture Chapter 7
Video Display
• The number of times per second that the entire surface is scanned by the electron gun is called the refresh rate.
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Systems Architecture Chapter 7
Video Display
Flat Panel Display
• Liquid Crystal Display – is a flat panel matrix that consists of encapsulated liquid crystals sandwiched between two polarizing panels.
• Passive Active Matrix Display – shares transistors among rows and columns of pixels.
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Systems Architecture Chapter 7
Video Display
• Electroluminescent Displays – similar to construction of LCDs. Color is generated with three matrices of different colored phosphors.
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Systems Architecture Chapter 7
Printers and Plotters
• Dot Matrix Printers• Ink-Jet Printers• Laser Printers• Plotters
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Systems Architecture Chapter 7
Printers and Plotters
Dot Matrix Printers
• Generate images through mechanical contact with ink and papers.
• Character codes received by the print generator are transmitted as a series of control commands to the print head.
• Characters are generated one or two vertical rows at a time.
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Systems Architecture Chapter 7
Printers and Plotters
Ink-Jet Printers
• Uses a paper movement mechanism similar to that of a dot matrix printer.
• The print head of an ink-jet printer consists of an ink cartridge, a set of ink chambers and a set of ink nozzles.
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Systems Architecture Chapter 7
Printers and Plotters
Ink-Jet Printers
• Each ink nozzle can print a single pixel and nozzles are arranged in short vertical rows similar to those of a dot matrix printer.
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Systems Architecture Chapter 7
Printers and Plotters
Laser Printers
• Operates differently from other types of printers.
• No print head or ink ribbon is used.• An internal image of the entire page is stored
in an internal buffer as a bit map.• Once filled, the buffer contents are sent to the
print driver for generation.
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Systems Architecture Chapter 7
Printers and Plotters
Plotters
• A printer that generates line drawings on wide sheets or rolls of paper.
• Paper is mounted within a paper control mechanism that can move the paper up or down precisely.
• Can handle paper widths up to 60 inches.
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Systems Architecture Chapter 7
Optical Input Devices
Optical scanning devices can be differentiated by the following criteria:
• Input format requirements• Normal and maximum spatial resolution• Normal and maximum chromatic resolution• Embedded processing capacity
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Systems Architecture Chapter 7
Optical Input Devices
Mark Sensors and Bar Code Scanners
• Mark Sensors – scans for light or dark marks at specific locations on a page.
• The mark sensors uses preprinted bars on the edge of the page to establish reference points.
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Systems Architecture Chapter 7
Optical Input Devices
Mark Sensors and Bar Code Scanners
• A scanning laser sweeps a narrow laser beam back and forth across the bar code.
• Bars must have precise width and spacing, as well as high contrast for accurate decoding.
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Systems Architecture Chapter 7
Optical Input Devices
• Optical Scanners – generate bit map representations of printed images.
• A bright light is shone on the page and reflected light is detected by an array of photodetectors.
• Spatial resolution is determined by the size and spacing of the photodetectors.
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Systems Architecture Chapter 7
Optical Input Devices
Optical character recognition (OCR)
• Combine optical scanning technology with hardware or software interpretation of bit map content.
• The bit mapped representation is searched for patterns corresponding to printed characters.
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Systems Architecture Chapter 7
Audio I/O Devices
Sound generation and recognition can be used in a number of ways.
– General-purpose sound output, such as warnings, status indicators, and music
– General-purpose sound input, such as digital recording
– Voice command input
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Systems Architecture Chapter 7
Audio I/O Devices
Sound generation and recognition can be used in a number of ways.
– Speech Recognition– Speech Generation
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Systems Architecture Chapter 7
Audio I/O Devices
Speech recognition
• The process of recognizing and appropriately responding to the meaning embedded within human speech.
• Human speech consists of individual sounds called phonemes.
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Systems Architecture Chapter 7
Audio I/O Devices
A number of factors complicate the process of speech recognition:
– Speaker variability– Phoneme transitions and combinations– Real-time processing
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Systems Architecture Chapter 7
Audio I/O Devices
Speech Generation
• A device that generates spoken messages based on textual input is called audio response unit.
• Simple audio response units digitally store and play back words or word sequences.
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Systems Architecture Chapter 7
Audio I/O Devices
Speech Synthesis
• Individual vocal sounds, or phonemes, are stored within the system.
• Character outputs are sent to a processor within the output unit, which assembles corresponding groups of phonemes to generate synthetic speech.
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Systems Architecture Chapter 7
General-Purpose Audio Hardware
Common names for general-purpose audio hardware are: – sound card– sound board – multimedia controller
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Systems Architecture Chapter 7
General-Purpose Audio Hardware
Sound cards include:– an analog-to-digital converter (ADC)– a digital-to-analog converter– a low power amplifier – connector for the microphone– a speaker or headphones
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Systems Architecture Chapter 7
General-Purpose Audio Hardware
Musical Instrument Digital Interface (MIDI) – is a standard for storage and transport of control information among computers and electronic instruments.
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Systems Architecture Chapter 7
Summary
• Manual input devices include keyboards, mice and other pointing devices.
• Display surfaces can be divided input rows and columns similar to a large table or matrix.
• A stored set of numeric pixel descriptions is called a bit map.
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Systems Architecture Chapter 7
Summary
• Video display terminals consist of an integrated keyboard and television screen.
• Commonly used paper output devices include dot matrix printer, ink-jet printer, laser printers, and plotters.
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Systems Architecture Chapter 7
Summary
• Optical input devices include optical scanners, mark sensors, bar code readers, and optical character recognition devices.
• General-purpose speech recognition systems can be used for command and control, or for the input of large amounts of textual material.
• Sound cards include converters, amplifiers, microphone, speaker and headphone connectors