1 Chapter 7 Input/Output Technology. 2 Systems Architecture Chapter 7 Chapter Goals Describe manual input devices and how they are implemented. Explain.

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Chapter 7

Input/Output Technology

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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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Chapter Goals

• Identify the characteristics of audio I/O devices, and explain how they operate.

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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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Chapter Topics

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Manual Input Devices

• Keyboard Input• Pointing Devices

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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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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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Pointing Devices

• Mouse• Trackball• Joystick• Digitizer Tablet

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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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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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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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Basic Concepts of Print and Display• Matrix-Oriented Image Composition

– Fonts– Color– Pixel Content

• Image Storage Requirements• Image Description Languages

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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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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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• Font – a collection of characters of similar style and appearance.

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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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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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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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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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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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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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Technology Focus - Postscript

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Technology Focus - Postscript

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Video Display

• Character-Oriented Video Display Terminals• Graphic Video Display Devices

– CRTs– Flat Panel Displays

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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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Video Display

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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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Video Display

• Monitors operate as independent devices under control of a video controller attached to the system bus.

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Video Display

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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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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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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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Video Display

• Electroluminescent Displays – similar to construction of LCDs. Color is generated with three matrices of different colored phosphors.

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Printers and Plotters

• Dot Matrix Printers• Ink-Jet Printers• Laser Printers• Plotters

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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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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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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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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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Printers and Buffers

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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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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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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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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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• 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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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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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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Audio I/O Devices

Sound generation and recognition can be used in a number of ways.

– Speech Recognition– Speech Generation

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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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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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Audio I/O Devices

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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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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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General-Purpose Audio Hardware

Common names for general-purpose audio hardware are: – sound card– sound board – multimedia controller

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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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Musical Instrument Digital Interface (MIDI) – is a standard for storage and transport of control information among computers and electronic instruments.

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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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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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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

1 Chapter 7 Input/Output Technology. 2 Systems Architecture Chapter 7 Chapter Goals Describe manual input devices and how they are implemented. Explain.

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