Input/Output Hardware
Chapter 3
Interfaces Between You and the
Computer
© The McGraw-Hill Companies, Inc., 2000
Overview
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Ch 3
I/O usage
Input hardware
Output hardware
Combined input and
output devices
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Input Hardware
• Three types:
keyboard,
pointing, and
source-entry
Ch 3
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Keyboard
• Standard keys
– type characters
– CAPS lock
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• Cursor-movement keys
– arrows, page up, page down
• Numeric keys
– for calculating (Num Lock)
• Function keys
– “F” keys, for software functions
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• Special-purpose keys
– Alt, Ctrl, Shift, Escape, Enter
Ch 3
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Source-data Entry Devices
• Scanners, bar-code scanners, fax
machines, imaging systems
• Voice-recognition devices
• Audio input devices
• Electronic cameras
• Sensors
• Human-biology input devices
Ch 3
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More Keys and Indicators
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Delete key
Insert key
Status lights
Secondary arrows in
numeric pad
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Function Keys
• Issue commands
• Defined by the software program
• Also used by some computers during boot
up to access the options for CMOS/BIOS
settings
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Ch 3
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Ergonomics
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Keyboards
Mice
Keyboard wrist pads
Monitor placement
Proper seat adjustment
Proper monitor viewing
adjustment
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Mice
• Can be wireless
controlled by
infrared or radio
signals
• Can have a
programmable
wheel
• Can have additional
buttons
Ch 3
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Mice Actions
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Ch 3
Point
Click
Double-click
Drag
Drop
Right-click
Programmable
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Which point device is best?
• Mouse
– Relatively inexpensive
– Little finger movement
– Foot print required is large
• Trackball
– Uses less space
– Less movement than mouse
– Increased finger movement
• Touchpad
– Less dust prone
– More precision
Ch 3
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Other Input
• Light Pen
– light-sensitive stylus
– use on display screens and ...
• Digitizing Tablets
– for graphic design, computer animation, and
engineering diagramming
• Pen-based Systems
– enter handwriting and marks into the
computer
Ch 3
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Types of Pen-Based Systems
• Gesture recognition or electronic checklists
• Handwriting stored as scribbling
• Handwriting converted to typed text
– similar to voice-recognition, requires training
the software
• Handwriting, converted without training, to
typed text
– not that accurate at this point
Ch 3
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PDAs
• Pen-based systems are
most commonly used
it in PDAs. Or
Personal Digital
Assistants, such as
3COM Palm III
Ch 3
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Source-Data Entry
• Does not require keystrokes
• Direct entry into computer often is more
accurate
• Main devices
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Ch 3
Bar-code readers
Mark and character recognition devices
FAX machines
Imaging systems
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Bar-Code
• Vertical striped marks
on most manufactured
products
• Often seen is a
Universal Product
Code, as seen in North
America and Australia
Ch 3
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Scanning Devices
• Bar-core readers
– Photoelectric scanners that translate code
symbols into digital code
• MICR
– Magnetic-ink character recognition numbers
such as on checks
Ch 3
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More input devices
• OMR
– Optical mark recognition reads marks and
converts them into usable form
– can now include black pen as well as pencil,
depending upon the reader
• OCR
– Optical character recognition uses specific
character sets, converting them into machinereadable form
Ch 3
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Other input devices
• FAX machines
– facsimile transmission machine
scans an image, then sends those
electronic images over telephone
lines
• Imaging systems
– Image or graphic scanners convert
text, drawings, photographs into
digital form which can then be
transmitted elsewhere
Ch 3
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Imaging Systems
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Used in
Desktop Publishing
Multimedia Development
Include scanners
– External: flatbed, drum, or handheld
– Internal: slide and photo
Ch 3
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Voice Recognition
• Using as microphone
or telephone
• Converts to digital
code
• Saves typing input
• Current technology
up to 98%
Ch 3
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Voice Recognition
• Keys after signal processing:
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Ch 3
Phonetic models
Dictionary
Grammar
Search
Output
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Audio Input Devices
• Records or plays
analog sound
• Translates for
digital storage
and processing
Ch 3
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Audio Boards
• Also called sound cards
• Some motherboards have built-in audio
boards
• Three major standards
– SoundBlaster
– Ad Lib
– Windows
Ch 3
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MIDI Boards
• Most support MIDI
– musical instrument digital interface
• MIDI boards
– used for multimedia applications
Ch 3
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Video and Photographic Support
• Most are analog
– frame-grabber video card
– full-motion video card
• Digital video growing rapidly
• Advent of USB ports
– rapid increase in digital cameras
• All-in-one cards
– provide sound and video
Ch 3
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Video Input
• Digital video
– can be limited to the speed
of the computer and its
ability to provide a
consistent and high enough
frames-per-second
– minimum to provide fullmotion is 24 frames per
second
Ch 3
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Digital Cameras
• Use charge-coupled device (CCD)
– light-sensitive photo cells
• Smallest 1/8th size of a 35 mm frame
• Up to 35 mm frame size
• Approaching image quality of 35mm
Ch 3
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Sensors
• Collect specific kinds of data directly from
the environment
• Transmit data to a computer for processing
and consolidation
• Under highways for traffic control
• Within buildings for temperature control
Ch 3
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Human-Biology Input Devices
• Identification through fingerprint, voice
intonation, retinal image
• Line-of-site systems
• Cyber gloves and body suits
Ch 3
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Multimedia Input Needs
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Ch 3
Sound card
Microphone
Graphics scanner
Video capture card
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Input Controls
• Garbage in, garbage out
• Manual and computer-based controls
• Software often uses internal software tables
to validate data input
• Reasonableness tests coded
• Care should be taken to ensure system is not
too restrictive
Ch 3
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Output Hardware
• What are the main characteristics
of printers, plotters,
multifunction devices, display
screens, and audio output
devices?
Ch 3
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Printers
• Impact printers
– draft
– near-letter quality
– line printers
• Non-impact printers
– laser
– ink-jet
Ch 3
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Laser Printers
• Often can be improved with additional
memory to handle increased office
requirements
• Page description standards
– PS
• Adobe Post Script
– HPGL
• Hewlett-Packard Graphic Language
Ch 3
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Ink-Jet Printers
• Slower, but less expensive than laser
printers
• Bubble-jet variation
– uses heat to force inks through print head
• Cartridges are often implemented in the
following ways
– single holder
• can often print color by switching cartridges
Ch 3
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Printer Cartridge Variation
– double holder
• can often print color and photo quality by replacing
cartridges
– quad holder
• uses black, plus three different color cartridges, or
four color cartridges
Ch 3
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Plotters
• Produce high-quality graphics, often on
large formats
• Two basic types
– ink-jet plotter
• slower, output on continuous drum
– electrostatic plotter
• paper lies partially flat, similar to a photocopier
process
Ch 3
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Printer or Plotter Installation
• Some drivers come preset within a BIOS
• Some come on included diskette or CD
• Often, more up-to-date drivers can be found
from the manufacturer’s Web site
• Newer drivers than default drivers, such as
keyboards or mice, may provide additional
functionality
Ch 3
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Multifunctional Printer
Technology: All for One
• Often printing, scanning, copying, and
faxing
• May not perform each function as quickly
or as well as individual devices
• Statistically the repair record of these
devices is equal to that of individual devices
Ch 3
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40 CCI
Monitors
• The softcopy output
• Display adapters/video
monitors have their own video
chips and RAM
• CRTs
– cathode ray tubes
– also in television sets
Ch 3
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Flat-Panel Screens
• Thinner, less weight
• Technologies used include:
– Liquid crystal display (LCD)
– Electroluminescent display (EL)
– Active-matrix or dual-scan (passive-matrix)
using transistors
Ch 3
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Screen Clarity
• Standard screen resolutions
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Ch 3
640 x 480
800 x 600
1024 x 768
1280 x 1024
1600 x 1200
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Changing screen resolutions and
refresh rates
• Consult manual for resolution and refresh
rates prior to changing, as monitors may be
damaged at ranges beyond capabilities
Ch 3
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Dot Pitch & Refresh Rate
• Closer the pixels, the crisper the image
• Less than .31 mm provides clear viewing
• Multimedia and desktop publishing
monitors often .25 mm pitch
• Refresh rate should be at least 72 Hz to
avoid eye fatigue
Ch 3
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Color
• Monochrome
– black on white, white on black
– amber on black
– green on black
• Color monitors or RGB (red, green, blue)
– between 16and 16.7 million color
– based upon color depth
Ch 3
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Monitor standards
• VGA
– video graphics display
– at 640 x 480 supports 4-bit color
• SVGA
– at 1024 x 768 supports 8-bit color
• XGA
– at 1024 x 768 supports 24-bit or true color
Ch 3
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Monitor capacity and trade-off
• The more colors and the higher the refresh
rate the harder the video card or adapter has
to work
• The higher the color settings the slower the
adapter
• The adapter and monitor must be
compatible, including whether analog or
digital
Ch 3
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Future Display Technology
• High Definition Televisions (HDTV)
– 1920 x 1080
• Field Emission Display (FED)
Ch 3
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Audio Output Hardware
• Voice Output
– Speech coding
– Speech synthesis
• sounds called phonemes
• Sound Output
– Digitized sounds
– Beeps to music
Ch 3
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50 CCI
Multimedia Output Needs
• Sound or audio card
• Headphones
• Speakers
Ch 3
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In & Out: Devices That Do Both
• Dumb terminals
• Intelligent terminals
– processing capability but no storage
• Point-of-Sale (POS) Terminals
• Automated Teller Machines
Ch 3
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52 CCI
Smart and Optical Cards
• Smart Cards
– Credit-card like with
microprocessor
• Touch screens
• Future
– retinal displays more
common
Ch 3
© The McGraw-Hill Companies, Inc., 2000
53 CCI
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Chapter 3: Input/Ouput Hardware