1. Chapter 7 Input/Output Technology

2. Chapter 7 Input/Output Technology
Chapter Outline
Basic Concepts of Print and Display
Technology Focus – Adobe Postscript and Portable Document Format
Video Display
Printers
Manual Input Devices
Optical Input Devices
Audio I/O Devices

3. 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
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

4. Chapter 7 Input/Output Technology

5. Basic Print and Display Concepts
Share many features
Character representation methods
Measurement systems
Methods of generating color

6. Matrix-Oriented Image Composition
Display surfaces
Fonts
Color
Numeric pixel content

7. 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)

9. 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

10. Color RGB (additive colors) Properly called “color”
Generates color by mixing red, green, and blue
CMY (subtractive colors)
Properly called “pigment”
Generates color using
cyan (absence of red)
magenta (absence of green)
yellow (absence of blue)
CMYK color
Four-dye scheme using a separate black dye (K)

11. Colors by Electromagnetic Wavelength and Frequency

12. Color Coding RGB One byte for each basic color

13. 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

14. 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)

15. 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 compression methods are lossy, resulting in some loss of image quality

16. 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

17. Vector Display

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

19. Adobe PostScript

20. Video Display Character-oriented video display terminals (VDTs)
Video controllers
Video monitors

21. 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

22. Video Display

23. Wyse Technology VDTs and Thin Clients

24. 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

25. Contains RAM, a microprocessor, and embedded software.
Video Controller
Contains RAM, a microprocessor, and embedded software.

26. Video Monitors Separate from keyboards Common types
Cathode ray tubes (CRTs)
Liquid crystal displays (LCDs)
Plasma displays

27. 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

28. 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

29. How
an LCD works

30. 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

31. Plasma Displays
Plasma displays have no backlight and no color filters; each pixel contains a gas that emits ultraviolet light when electricity is applied.

32. Printers Impact (dot matrix) Inkjet Laser Slow, noisy
Relatively poor-quality output
Inexpensive
Inkjet
Relatively slow
Excellent-quality output
Laser
Relatively fast

33. 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

34. Dot Matrix Printers

35. Daisy Wheel Printers

36. 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

37. Inkjet Printers
An inkjet printer has disposable print cartridges that contain ink reservoirs, a matrix of ink nozzles, and electrical wiring and contact points.

38. Lasar Printers

39. Lasar Printers
Laser printers operate with an electrical charge and the attraction of ink to that electrical charge.

40. Lasar Printers

41. Lasar Printers

42. Lasar Printers

43. 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

44. Manual Input Devices Keyboards Pointing devices Input pads
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

45. 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)

46. Pointing Devices Mouse Trackball Joystick
Input pads (e.g., digitizer tablet)
Infrared detector
Photosensor
Pressure-sensitive pad

47. Optical Input Devices
Detect light reflected off a printed surface or object into a photosensor
Categories
Mark and pattern sensors
Image capture devices

48. Mark Sensors and Bar-Code Scanners
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

49. Advanced scanning technology can now read two-dimensional bar codes.
PDF417 Bar Code
Advanced scanning technology
can now read two-dimensional bar codes.

50. 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

51. Digital Cameras
Employ optical scanning technology to capture single or still images and store them as raw compressed bitmaps

52. 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)

53. 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

54. Purposes of Sound Generation and Recognition
General-purpose sound output (e.g., warnings)
General-purpose sound input (e.g., digital recording for voice messages)
Voice command input
Speech recognition
Speech generation

55. 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

56. Speech Recognition

57. 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)

58. 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

59. Typical Sound Card Components and Connections

60. 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

61. 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
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