Computers:
Tools for an Information Age
Chapter 5
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
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
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
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
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
Input: Getting Data from the User to the
Computer
Keyboard
Pointing devices
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
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
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
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
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
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
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
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
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
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
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
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
Smart Displays
Based on flat-panel technology
Each contains its own processor
Wireless transmitter-receiver allows user to
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
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
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
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,
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
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
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
Computer Graphics
Business graphics
Video graphics
Computer-aided design/computer-aided
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
Computer-Aided Design/
Computer-Aided Manufacturing
Creates two- and
three-dimensional designs
Performs engineering tests
such as stress tests
Serves as bridge between
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?
