1 Chapter 7 Input/Output Technology

2 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.

3 Systems Architecture Chapter 7 Chapter Goals Identify the characteristics of audio I/O devices, and explain how they operate.

4 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.

5 Systems Architecture Chapter 7 Chapter Topics

6 Systems Architecture Chapter 7 Manual Input Devices Keyboard Input Pointing Devices

7 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.

8 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.

9 Systems Architecture Chapter 7 Manual Input Devices Pointing Devices Mouse Trackball Joystick Digitizer Tablet

10 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.

11 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.

12 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.

13 Systems Architecture Chapter 7 Basic Concepts of Print and Display Matrix-Oriented Image Composition –Fonts –Color –Pixel Content Image Storage Requirements Image Description Languages

14 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.

15 Systems Architecture Chapter 7 Basic Concepts of Print and Display Matrix-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).

16 Systems Architecture Chapter 7 Basic Concepts of Print and Display

17 Systems Architecture Chapter 7 Basic Concepts of Print and Display Font – a collection of characters of similar style and appearance.

18 Systems Architecture Chapter 7 Basic Concepts of Print and Display

19 Systems Architecture Chapter 7 Basic Concepts of Print and Display

20 Systems Architecture Chapter 7 Basic Concepts of Print and Display Color 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.

21 Systems Architecture Chapter 7 Basic Concepts of Print and Display Color 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)

22 Systems Architecture Chapter 7 Basic Concepts of Print and Display Pixel 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.

23 Systems Architecture Chapter 7 Basic Concepts of Print and Display

24 Systems Architecture Chapter 7 Basic Concepts of Print and Display Image 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.

25 Systems Architecture Chapter 7 Basic Concepts of Print and Display Image Storage Requirements Compression Techniques: Graphics Interchange Format (GIF) Joint Photographic Experts Group (JPEG) Moving Pictures Experts Group (MPEG)

26 Systems Architecture Chapter 7 Basic Concepts of Print and Display Image 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.

27 Systems Architecture Chapter 7 Basic Concepts of Print and Display

28 Systems Architecture Chapter 7 Technology Focus - Postscript

29 Systems Architecture Chapter 7 Technology Focus - Postscript

30 Systems Architecture Chapter 7 Video Display Character-Oriented Video Display Terminals Graphic Video Display Devices –CRTs –Flat Panel Displays

31 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.

32 Systems Architecture Chapter 7 Video Display

33 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.

34 Systems Architecture Chapter 7 Video Display Monitors operate as independent devices under control of a video controller attached to the system bus.

35 Systems Architecture Chapter 7 Video Display

36 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.

37 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.

38 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.

39 Systems Architecture Chapter 7 Video Display Electroluminescent Displays – similar to construction of LCDs. Color is generated with three matrices of different colored phosphors.

40 Systems Architecture Chapter 7 Printers and Plotters Dot Matrix Printers Ink-Jet Printers Laser Printers Plotters

41 Systems Architecture Chapter 7 Printers and Plotters

42 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.

43 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.

44 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.

45 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.

46 Systems Architecture Chapter 7 Printers and Buffers

47 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.

48 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

49 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.

50 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.

51 Systems Architecture Chapter 7 Optical Input Devices

52 Systems Architecture Chapter 7 Optical Input Devices

53 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.

54 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.

55 Systems Architecture Chapter 7 Optical Input Devices

56 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

57 Systems Architecture Chapter 7 Audio I/O Devices Sound generation and recognition can be used in a number of ways. –Speech Recognition –Speech Generation

58 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.

59 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

60 Systems Architecture Chapter 7 Audio I/O Devices

61 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.

62 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.

63 Systems Architecture Chapter 7 General-Purpose Audio Hardware Common names for general-purpose audio hardware are: –sound card –sound board –multimedia controller

64 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

65 Systems Architecture Chapter 7 General-Purpose Audio Hardware

66 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.

67 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.

68 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.

69 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