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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
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
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.
Invented by Doug Englebart at SRI, 1963/4
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 three-
dimensional 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?