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Understanding User Input and Output: Key Concepts in Computer Interaction

This chapter explores the fundamental relationship between users and computer systems focusing on input and output processes. It explains how data is entered into computers using various input devices such as keyboards and pointing devices, and describes how the monitor functions and its quality characteristics. Additionally, the chapter outlines the different output methods, discusses various printer types, and details the roles and varieties of computer terminals, enhancing the understanding of the human-computer interaction landscape.

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Understanding User Input and Output: Key Concepts in Computer Interaction

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  1. Input and Output:The User Connection Chapter 5

  2. Objectives • Describe the user relationship with computer input and output • Explain how data is input to a computer system and differentiate among various input equipment • Describe how a monitor works and the characteristics that determine quality • List and describe the different methods of computer output • Differentiate among different kinds of printerExplain the function of a computer terminal and describe the types of terminals

  3. Contents • Input and Output • Input • Output • Terminals • Computer Graphics • Ethics and Data

  4. Input and Output Input • Users submit input data Output • Users get processed information

  5. Input • Data from the user to the computer • Converts raw data into electronic form

  6. Diversity of Input Methods • Zebra-striped bar codes on supermarket items • Word commands operate a forklift truck • An order is entered using a pen on a special pad • Time clock generates paycheck • Data on checks are read and used to prepare a monthly bank statement • Charge-card transactions generate customer bills

  7. Keyboard • Traditional • Looks like typewriter with extra keys • Non-traditional • Fast food restaurants • Each key represents a food item rather than a character

  8. Function Keys Give commands Software specific Main Keyboard Typewriter keys Special command keys Keyboard

  9. Keyboard • Numeric Keys • Num Lock – toggle • On – numeric data & math symbols • Off – cursor movement • Cursor Movement Keys

  10. Shift Caps Lock Ctrl Alt Esc Enter Windows Shortcut KeyboardSpecial Keys

  11. Pointing Devices • Position a pointer / cursor on the screen • Controls drawing instruments in graphics applications • Communicate commands to a program

  12. Pointing Devices Mouse • Types • Mechanical • Optical • Wireless • Features • Palm-sized • 1 or 2 buttons • Wheel

  13. Other Pointing Devices • Trackball • Upside-down mouse • Ball on top • Roll ball with hand • Laptop computers • Touchpad • Pressure-sensitive pad • Cursor moves as you slide your finger • Laptop computers

  14. Other Pointing Devices Pointing stick • Pressure-sensitive post • Mounted between G and H keys on keyboard • Apply pressure in a direction to move cursor Joystick • Short lever • Handgrip • Distance and speed of movement control pointer position

  15. Graphics Tablet • Digitizing tablet • Rectangular board • Invisible grid of electronic dots • Write with stylus or puck • Sends locations of electronic dots as stylus moves over them • Creates precise drawings • Architects and engineers

  16. Touch Screens • Human points to a selection on the screen • Types • Edges emit horizontal and vertical beams of light that crisscross the screen • Senses finger pressure • Light pen for pointing

  17. Touch Screens • Kiosks • Self-help stations • Easy to use • Where found • Malls • Disney World • Government offices

  18. Pen-based Computing • Small hand-held devices • Electronic pen (stylus) • Pointer • Handwritten input • Personal Digital Assistants (PDA)

  19. Source Data Automation • Special equipment to collect data at the source • Sent directly to a computer • Avoids need to key data • Related input areas • Magnetic-Ink Character Recognition • Scanners • Optical recognition devices • Voice

  20. MICRMagnetic-Ink Character Recognition • Read characters made of magnetic particles • Numbers on the bottom of checks • MICR inscriber – adds characters to check that show amount cashed

  21. Optical Scanners • Optical recognition • Light beam scans input data • Most common type of source input • Document imaging – converts paper documents to electronic form • Converts snapshots into images • Converts scanned picture into characters – OCR Exact computer-produced replica of original

  22. Types of Scanners • Flatbed • One sheet at a time • Scans bound documents • Sheetfeed • Motorized rollers • Sheet moves across scanning head • Small, convenient size • Less versatile than flatbed • Prone to errors

  23. Types of Scanners • Handheld • Least expensive • Least accurate • Portable • User must move the scanner in a straight line at a fixed rate • Wide document causes problems

  24. Optical Recognition • Optical mark recognition (OMR) • Mark sensing • Exams • Recognizes the location of the marks • Optical character recognition (OCR) • Light source reads special characters • OCR-A is ANSI standard typeface for optical characters

  25. Optical RecognitionWand Reader Retail stores Libraries Hospitals Factories

  26. Optical RecognitionBar Code Reader • Photoelectric device • Reads bar codes • Inexpensive • Reliable • Where Used? • Supermarket – UPC • Federal Express

  27. Optical RecognitionHandwritten Characters Must follow rigid rules • Size • Completeness • Legibility

  28. Voice Input • Speech Recognition • Speech recognition devices • Input via a microphone • Voice converted to binary code • Problems • Speaker-dependent • Voice training

  29. Voice Input • Changing radio frequencies in airplane cockpits • Placing a call on a car phone • Requesting stock-market quotations over the phone • Command from physically disabled users

  30. Voice Input • Discrete work systems • Understand isolated words • Pause between words • Difficult for dictation • Continuous work systems • Normal speaking pattern • Easy to use • Faster and easier to dictate than to key

  31. Digital Cameras • Photos stored in electronic form • No film • Point and shoot • Edit

  32. Output • Information for the user • Types • Screen – soft copy • Printer – hard copy • Voice • Sound • Graphics

  33. Monitor • Data that is entered appears on the screen • Screen is part of the monitor

  34. Monitor Cathode Ray Tube (CRT) Flat panel display Liquid Crystal Display (LCD)

  35. CRT Raster scanning • Sweeping electron beams across the back of the screen • Phosphorous coating on back • Glows when hit by a beam of electrons • Phosphorous loses glow and image fades and flickers • Image must be continually refreshed

  36. CRT Refresh rate / scan rate • Number of times electron beams refreshes the screen • 80-100 times per second adequate for clear screen image • Process also used for television

  37. CRT Interlaced vs. Non-interlaced • Interlaced • Refresh every other line on each pass • Lower refresh rate without flicker • Good for fixed graphics • Causes flutter with animated graphics • Inexpensive • Non-interlaced • Refresh every line on each pass • Typical screen sold today

  38. CRT Color vs. Monochrome • Color • Typical monitor sold today • Monochrome • Green or amber on a contrasting background • Less expensive than color

  39. CRT Resolution • Clarity of image • Pixel (Picture element) • Dot on screen • Is addressable • Can be illuminated • More pixels means higher resolution • Dot pitch • Distance between dots • Smaller distance means better quality image

  40. CRT Graphics Card/Graphics Adapter Board • Plugs into expansion slot on motherboard • Graphics card and monitor must be compatible for high quality image

  41. CRT Size • Measured diagonally • Typical sizes • Office user: 15-17 inch • High-powered graphics user: 19 inch • High-end monitors: 21 inches and up • Larger size • More expensive • More space on desktop • Reduces eye strain

  42. Graphics Standards • PCs • Monitor • Graphics boards • Software Help insure that the products work together

  43. Graphics Standards • SVGA (Super VGA) • Resolution – 800 x 600, 1024 x 768, 1280 x 1024, 1600 x 1200 pixels • 16 million colors • Number of colors displayed simultaneously limited by amount of video memory • XGA (Extended Graphics Array) • High resolution • Supports more simultaneous colors • Allows non-interlaced monitors

  44. Flat-panel Screens • Liquid Crystal Display (LCD) • Primarily on laptops • Moving to desktop • Skinny (depth) regardless of size

  45. Flat-panel Screens • Crisp, brilliant images • Easy on eyes • No flicker • Full dimension is useable • More expensive that CRT monitors

  46. Flat-panel Screens • Active Matrix • Thin-film transistor technology (TFT) • Transistors for each pixel • Brighter image • Viewable from an angle • Passive Matrix • Fewer transistors • Cheaper • Less power

  47. Printer • Produces information on paper • Orientation • Portrait • Landscape • Methods of printing • Impact • Nonimpact

  48. Line printer One line at a time High volume Low quality Dot-matrix printer One character at a time Impact Printers

  49. Nonimpact PrinterLaser Printer

  50. Nonimpact PrinterLaser Printer • Transfers images to paper using a light beam • Prints one page at a time • 600-1200 dpi – High quality • Speed • Personal laser printers: 8-10 ppm • Network laser printers: 35-50 ppm • High-volume laser printers: up to 1000 ppm • Black and white / color

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