Computers: Tools for an Information Age Chapter 5 Input and Output: The User Connection
Objectives Describe the user relationship with computer input and output Explain how data is input into 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
Objectives Differentiate among different kinds of printers Explain the function of a computer terminal and describe the types of terminals Describe the ethical considerations involved in handling computer data
How Users See Input and Output Users submit data (input) to the computer to get processed information (output) Output can be instant reaction to input Also can be separated by time, distance, or both
Instant Reaction Items scanned at supermarket Produce item name and price at counter Forklift operator speaks to computer Forklift obeys operator s commands Sales rep enters an order on a pad Characters displayed as typed text and stored in pad Factory workers punch a time clock as they go from task to task Produce weekly paychecks and management reports
Input and Output Separated Data on checks input into bank computer Computer processes entries once a month to prepare statements Charge-card transactions provide input Processed monthly to produce customer bills Water samples collected and input into computer Used to produce reports that show patterns of water quality
Input: Getting Data from the User to the Computer Keyboard Pointing devices Source data automation
Keyboard Similar to typewriter keyboard May be part of a personal computer May be part of a terminal connected to a computer in another location Can be unique to an industry Keys on McDonald s keyboards represent Big Mac or large fries Ergonomic keyboards
Ergonomic Keyboards Designed to reduce or minimize repetitive strain injury of wrists Provide more natural, comfortable position of wrists, arms, and hands
Anatomy of a Keyboard
Pointing Devices Used to position a pointer on the screen Communicate commands to operating system by clicking a button Common devices Mouse Devices used for games Devices used in laptops Others
The First Mouse Invented by Doug Englebart at SRI, 1963/4 Doug Engelbart invented the computer mouse in 1963-64 as part of an experiment to find better ways to point and click on a display screen. It was made in a shop at SRI. The casing was carved out of wood. The mouse had only one button - that was all there was room for.
Mouse The most common pointing device Movement on flat surface causes movement of pointer on screen Several types Mechanical - small ball on underside rolls as mouse is moved Optical - uses a light beam to monitor mouse movement Cordless - uses either infrared or radio waves, rather than a cord, to connect to computer
Trackball and Joystick Trackball Variation on mechanical mouse User rolls the ball directly Often built into laptop computers Joystick Short lever with handgrip Distance and speed of movement controls pointer s position Pressing trigger causes actions to take place
Touchpad and Pointing Stick Touchpad Rectangular pressure-sensitive pad Sliding finger across pad moves pointer Tapping with finger recognized as click Pointing stick Small pressure-sensitive post mounted in center of keyboard Pushing post in any direction moves pointer
Other Pointing Devices Graphics tablet User moves stylus or puck across board Used to create or trace precise drawings Touch screen Allow user to touch items on screen Position of finger on screen determines item to be input into system Used at kiosks in public places such as malls Pen-based computing Use pen-like stylus to input data Often used in PDAs or pocket PCs
Source Data Automation Use of special equipment to collect data at the source Primary areas Magnetic-ink character recognition (MICR) Optical recognition devices Other sources
MICR Uses a machine to read characters made of magnetized particles Banking industry is predominant user Characters preprinted on lower left-hand side of check Amount added by MICR inscriber when check is cashed
Optical Recognition Uses a light beam to scan data and convert to electrical signals Common uses Scanners are the most common form Other optical recognition methods
Common Uses Scanners at supermarkets Document imaging - converts paper documents to electronic versions Documents stored on disk Can be edited or processed by software
Scanners Flatbed scanner Typically scans one page at a time Can be used to scan large bound documents Sheetfed scanner Motorized rollers feed sheet across scanner head Handheld scanner Smallest and least accurate Optical character recognition (OCR) software required to convert picture into characters
Other Optical Recognition Methods Optical Mark Recognition Machine senses marks on piece of paper Optical character recognition Wand reader reads characters in special typeface Bar Codes A series of vertical marks Represents a unique code Universal Product Code (UPC) used as standard in supermarkets
Other Sources Voice input Digital cameras Video input
Voice Input User speaks to computer Speech recognition devices convert spoken words into binary digits Most are speaker-dependent System learns user s voice Types of systems Discrete word systems - user must pause between words Continuous word systems - user can speak normally
Digital Camera User takes photo that is stored on a chip Photo can be downloaded to computer Use photo-editing software to enhance Store permanently on CDs or DVDs Photos composed of many pixels of color Photos stored on removable memory card
Video Input Digital video consists of series of still frames Displayed rapidly enough to give illusion of motion Web cam used to transmit video over the Internet Can capture video from analog sources with video capture card
Output: Information for the User Computer screens Printers Voice output Music output Microform
Computer Screen Technology Screen is part of computer s monitor Screen output known as soft copy Intangible and temporary Common forms Cathode ray tube (CRT) Flat-panel screens Smart displays
CRT Screens Display text and graphics Most are in color Some monochrome monitors are used in applications that have no need for color or graphics Graphics card converts signals from the control unit into the image the user sees
Factors Affecting Performance Scan rate The frequency with which the image is refreshed Resolution (clarity) of screen Measured in pixels (picture elements) The more pixels, the higher the resolution Graphics standards Dot pitch The amount of space between dots The smaller the dot pitch, the sharper the image Video memory A high-speed form of RAM installed on graphics card
Graphic Standards Agree on resolutions, colors, other issues related to displaying graphics Super Video Graphics Adapter (SVGA) is most common standard Provides 800 (horizontal) x 600 (vertical) pixels on the display Other varieties of SVGA exist Support 16 million colors The number of colors that can be displayed depends on amount of video memory
Flat-Panel Screens Liquid crystal display (LCD) Originally used for laptops, but making their way to desktop computers Very thin (only a few inches) Produce sharper text images than CRTs Easier on eyes than CRTs Different flat-panel technologies
LCD Technologies Active-matrix Uses many thin-film transistors (TFT) Produces brighter image and can be viewed from wider angles Passive-matrix Uses fewer transistors Cheaper and uses less power Gas plasma Supports very large displays Has brilliant color display Viewable at very wide angles
Smart Displays Based on flat-panel technology Each contains its own processor Wireless transmitter-receiver allows user to control desktop from anywhere in the house
Printers Produce information on paper output Printed output known as hard copy Orientation settings Portrait - vertical alignment Landscape - horizontal alignment Two ways of printing Impact printer Non-impact printer
Impact Printers Physical contact with paper required to produce image Line printer Prints an entire line of a program at once Typically used with mainframe computers printing lengthy reports Dot-matrix printer Has print head consisting of one or more columns of pins Pins form characters and images as pattern of dots
Non-impact Printers Places an image on a page without physically touching the page Laser printer Uses light beam to help transfer images to paper Produces high-quality output at very fast speeds Ink-jet printer Sprays dots of ink from jet nozzles Can print in both black and white and color Requires high-quality paper so ink does not smear Less expensive than laser printers
Voice Output Voice synthesizers convert data to vocalized sounds Two approaches Synthesis by analysis - analyzes actual human voice, records and plays back as needed Synthesis by rule - uses linguistic rules to create artificial speech Used in automated telephone-based customer service applications Useful when an inquiry would be followed by a short reply, such as a balance inquiry
Music Output Multimedia clips, games, videos include sight and sound Speakers placed on side of monitor Powered sub-woofers produce low-frequency sounds Musical Instrument Digital Interface (MIDI) Rules for connecting musical instruments, synthesizers, and computers Allows users to set up home studios that rival capabilities of professional recording studios
Computer Output Microform (COM) Output of photographically reduced images on microfilm or microfiche Microfilm - images stored on continuous roll of film Microfiche - images stored in rows and columns on a card Needs special reader Common uses Libraries store back issues of periodicals Businesses store large volumes of historical records
Terminals Combine input and output capabilities Dumb terminal Keyboard for input and monitor for output No processing capability Intelligent terminal Has limited memory and a processor Point-of-sale (POS) terminal Captures retail sales data when transaction takes place
Computer Graphics Business graphics Video graphics Computer-aided design/computer-aided manufacturing (CAD/CAM)
Business Graphics A powerful way to impart information Colorful graphics, maps, and charts help managers compare data, spot trends, and make quicker decisions As underlying data changes, charts and graphs are instantly updated
Video Graphics A series of video images Displayed rapidly to give the impression of motion Used extensively in television Also used in computer and arcade video games
Computer-Aided Design/ Computer-Aided Manufacturing Creates two- and threedimensional designs Performs engineering tests such as stress tests Serves as bridge between design and manufacturing
Ethics and Data Once data is in computer, there are many ways it can be used Ethical issues to ponder Is it ethical to use a computer to alter photographs? Is it ethical to erase e-mail messages that may be of interest to a party in a lawsuit? Is it ethical to use someone else s data for your purposes?