Download Chapter 5 Input and Output Learning Objectives Learning Objectives

Learning Objectives
• Identify several types of input and output
Chapter 5
Input and Output
devices and explain their functions.
• Describe the characteristics of the input
equipment that most users encounter regularly,
namely, keyboards and pointing devices.
• Explain what source data automation is and
discuss how scanners and other devices can be
used to accomplish it.
Learning Objectives, cont’d.
• List several types of multimedia input devices and
discuss their purposes.
• Describe the characteristics of the output equipment that
most users encounter regularly, namely, display devices
and printers.
• Discuss several types of multimedia output equipment.
• Explain what a multifunction device is and list some
Overview
• This chapter covers:
– Equipment designed primarily for input of
programs and data into the computer
system, or for output, or for both.
• Many other types of input/output devices
exist, but this chapter covers a good
sampling of the most widely used ones.
advantages and disadvantages of using such a device.
Input and Output
• Input devices convert data and programs that
people can understand into a form
comprehensible to the CPU.
• Output devices convert the strings of bits used
by the computer back into a form that people
can understand.
Keyboards
• Keyboards can differ in number of keys, key
arrangement, types of special keys, and touch.
– QWERTY – widely used
– Dvorak – not used often
• Function keys enable software packages to be
customized to meet a user's applications needs.
• The numeric keypad makes it easy to enter
numbers quickly.
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Ergonomic Keyboards
• Designed to reduce
or minimize
repetitive strain
injury of wrists
– Provide more natural,
comfortable position
of wrists, arms, and
hands
Pointing Devices: 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
Common mouse
operations are clicking,
scrolling, and dragging
and dropping.
Pointing Devices: Electronic
Pens
Electronic Pens Use
• Electronic pen:
pen: an alternative to the mouse to
• Graphics tablet
•
select objects or to write or draw on the screen
Types:
– light pen (uses lightlight-sensitive cell in its tip)
– stylus (usually plastic)
• Devices that use pen input:
– Signature capture devices
– Graphics tablets
– PenPen-based computers
– User moves stylus or puck
across board
– Used to create or trace precise
drawings
• PenPen-based computing
–Use penpen-like stylus to input data
–Often used in PDAs or pocket PCs
–Use handwritten character recognition
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Pointing Devices: Touch Screens
Trackball and Joystick
• Touch screens are used:
• Trackball
– When consumer input is
required, as in consumer
kiosks
– When other input devices are
impractical
– Allow user to touch items on
screen
– Position of finger on screen
determines item to be input
into system
– 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’
pointer’s position
– Pressing trigger causes actions to
take place
Touchpad and Pointing Stick
Scanners and Related Devices
• Touchpad
• Source data automation involves collecting
– Rectangular pressurepressure-sensitive pad
– Sliding finger across pad moves
pointer
– Tapping with finger recognized as
click
data in machinemachine-readable form as soon as
it is generated.
• Pointing stick
• Source data automation is used to convert
Optical Scanners
Scanners
– Small pressurepressure-sensitive post
mounted in center of keyboard
– Pushing post in any direction
moves pointer
• Optical scanner:
scanner: converts hardhard-copy images of
text pages, photographs, and drawings into
digital form
• Common uses:
– Scanners at supermarkets
– Document imaging - converts paper
documents to electronic versions
• Documents stored on disk
• Can be edited or processed by software
source documents into digital form and
commonly utilizes some type of scanner.
• 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
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Scanners (Cont’d)
• Other types of scanners:
– Drum scanner (very large and expensive.
Documents are mounted on a glass cylinder)
– 3D scanner (for multimedia applications)
• Scanner resolution
– Measured in dots per inch (dpi)
– 72 to 150 dpi for images displayed on screen
– 300 dpi and higher for printed
Optical Characters
•Optical character recognition (OCR) software
required to convert picture (scanned document) into
characters
•2nd type of 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
Optical Readers
• Optical marks
• Optical
characters
• Optical codes
Magnetic Ink Character
Recognition (MICR)
• Uses a machine to read
characters made of
magnetized particles
• Banking industry is
predominant user
– Characters preprinted on
lower leftleft-hand side of check
– Amount added by MICR
inscriber when check is
cashed
Magnetic Ink Character Recognition
Reader
Multimedia Input: Digital
Cameras
• Readers can read the special magnetic
• User takes photo that is stored on a chip
characters, as well as sort documents by their
codes.
instead of film
• Photos can be downloaded to computer
(via cable or special card reader)
– Use photophoto-editing software to enhance
– Store permanently on CDs or DVDs
• Photos composed of many pixels of color
• Photos stored on removable memory card
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Multimedia Input: Video
Cameras
• Video cameras can be used to either
record or send images over the Internet.
• Video input can also be obtained by using
special hardware to transfer conventional
video images to the computer.
Video Input
Multimedia Input:
Audio Input Devices
• Digital video consists of series
• VoiceVoice-input systems convert spoken words to digital
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
data.
• User speaks to computer
•
•
– Speech recognition devices convert spoken words into
binary digits
Most are speakerspeaker-dependent
– System “learns”
learns” user’
user’s voice
Types of systems
– Discrete word systems - user must pause between
words
– Continuous word systems - user can speak normally
Other Audio Input Devices
Display Devices
• MusicMusic-input systems can record musical input for
• Display devices are the most common type of
use with a multimedia presentation or to be
edited or combined with other input
• MIDI – musical instrument digital interface –
device, such as musical keyboard
• Telephony is the process of performing
telephonetelephone-oriented tasks using a computer
output device.
• PC displays are commonly called monitors.
monitors.
• Can be separate from computer or combined
• The cursor, or insertion point, indicates where
editing or typing will appear on the display
screen.
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Size
Resolution
• Resolution refers to the sharpness of the
screen image.
• Most monitors today are about 17 inches
wide, measured diagonally.
„
• The actual viewing area is typically less
than the stated size.
Images are formed
by lighting up tiny
dots on the screen
called pixels.
Resolution (cont’d)
Graphics Standards
• Dot pitch – the distance between the pixels
• Computer graphics standards specify such characteristics
• Resolution shows how many distinct columns
• Video cards connect the monitor to the PC and support a
• Higher resolution – smaller image – more details
• Video cards typically contain video RAM to support the
(measures in millimiters).
millimiters). Usual are .26 and .28
(smaller is better)
and rows of pixels the screen can display
• Can be selected by user
as the possible resolutions and number of colors that can
be used.
particular graphics standard, such as SVGA. (SVGA
allows true color - 24 bit - 16.7 million colors)
number of colors and resolutions allowed, as well as to
help speed up image display.
Color vs. Monochrome Displays
CRT vs. Flat-Panel Displays
• Most color displays are of the RGB type.
• RGB displays combinations of red, blue, and
• Most desktop display devices use CRT
•
green light to form other colors.
Refresh rate – 60 to 80 times per second (Hz)
cathode ray tube) technology, similar to
conventional television technology.
• FlatFlat-panel displays are compact,
lightweight, and consume little power.
– Ideal for notebook computers
– Most use liquid crystal display (LCD)
technology
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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
Flat Panel Technologies
• ActiveActive-matrix LCD
– Uses many thinthin-film transistors (TFT)
– Produces brighter image and can be viewed from
wider angles
• PassivePassive-matrix LCD
– Uses fewer transistors
– Cheaper and uses less power
• Gas plasma
– Supports very large displays
– Has brilliant color display
– Viewable at very wide angles
HDTV
• HDTV is a new type of television that supports
highhigh-resolution digital broadcasts (up to 1080
lines)
• WideWide-format (16:9 instead of regular 4:3)
• All broadcasting is expected to eventually be in
high definition
• HDTV monitor can be used as both TV and
computer monitor
Printers
Impact Printers
• Produce information on paper output
• Physical contact with paper required to produce
– Printed output known as hard copy
• Print resolution is commonly measured in dots
per inch (dpi).
• Two technologies are used:
– Impact Printers
– Nonimpact printers
image
• Line printer
– Prints an entire line of a program at once
– Typically used with mainframe computers printing
lengthy reports
• DotDot-matrix printer
– Has print head consisting of one
or more columns of pins
– Pins form characters and images
as pattern of dots
– still used for multipart forms
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Nonimpact Printers
Personal Printers: Laser
• Places an image on a page without physically
• Laser printers often cost between $200
•
touching the page
Laser printer
– Uses light beam to help transfer images to paper
– Produces highhigh-quality output at very fast speeds
• InkInk-jet printer
– Sprays dots of ink from jet nozzles
– Can print in both black and white and
color
– Requires highhigh-quality paper so ink
does not smear
– Less expensive than laser printers
and $400 and print 5 to 12 pages per
minute (ppm), at resolutions of at least
600 dpi.
„
„
„
Work similarly to photocopy
machines.
Toner is in toner cartridge
Are usually black and white,
though color laser printers
are available.
Personal Printers: Ink-Jet
Network Printers
• InkInk-jet printers produce images by spraying
• A network printer is shared by several
•
• Line printers print a whole line at a time
•
thousands of droplets of electrically charged ink onto a
page.
Technology of choice for home users who want to
produce affordable, hardhard-copy color output from desktop
systems.
Ink is in print cartridge (can be expensive)
people over a local area network.
rather than just a character.
• Page printers can produce a page of
output at a time.
• Network laser printers are faster and hold
more paper than personal versions.
Special Purpose Printers
• Photo printers
• BarBar-code printers
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Portable printers
„
Electrostatic Plotters
„
Wide-format ink-jet printers
• Label printers
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Multimedia Output Devices
Voice Output
• Speakers
• Voice synthesizers convert data to vocalized
• Data and multimedia projectors
• VoiceVoice-output systems
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 telephonetelephone-based customer
service applications
– Useful when an inquiry would be followed by a short
reply, such as a balance inquiry
Multifunction Devices
• A multifunction device offers some
combination of:
– Printing
– Copying
– Scanning
– Faxing
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