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Input Output Devices
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Back of Computer
Remove these screws
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Step 2 Looking Inside
Identify all the major components:
Power Supply
Motherboard
Memory
Card Slots
Cards (sound, video, network)
CPU, heatsink and fan
Drives (floppy, hard and CD-ROM)
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powersupply
hard
drive
motherboard
COMPONENTS
CD-ROM
drive
floppydrive
cards
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Input and Output
Input devices convert data from the user into aform understood by the computer.
Output devices convert the processed 0s and 1sinto a form that the user can understand.
Hard copypermanently recorded, such as onpaper.
Soft copytemporarily recorded, such as on acomputer screen.
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The Keyboard
The most common input device is the keyboard,which is used to enter letters, numbers and special
characters.
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Working with the Keyboard
Function keysare special purpose keys whose functiondepends on the software being used.
Cursor keysare used to move the cursor up, down, left,
or right.
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Variations on Keyboard Design
Ergonomic
to address repetitive stress
injuries
Wireless Folding
Half
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Keyboards
Portablekeyboardsandthumb pads
areincreasingly
being used
with portablePCs and
mobile
devices.
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Pointing Devices, Contd.
Electronic pens (light pen, stylus)
An alternative to the mouse to select objectsor to write or draw on the screen.
Commonly used with:
Graphics tablets
Digital portfolios and digital pens
Signature capture devices
Pen-based computers
Handwriting recognition technology
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Pointing Devices,Contd.
Touch screens
Used when other
input devices are
impractical.
Often used when
consumer input isrequired, as in
consumerkiosks.
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Pointing Devices,Contd.
Other common pointing devices
Joysticks and other gaming devices
Trackballs
Pointing sticks
Touch pads
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Pointing Devices
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Reading Tools
Optical-mark readers
Bar-code readers
Magnetic-inkcharacter readers
Wand readers
Pen scanners
Input devices read directly from paper and convertprinted information into bit patterns that can beprocessed by the computer.
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Digitizing the Real World
Scanner
Digital camera
Speech recognition Sensing devices
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Scanners
Scanners capture and digitize printed images.
There are several types of scanners:
Flatbed scanners
Handheld scanners
Sheet-fed scanners
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Scanners
Scanners (optical scanners) convert hard-copy images of text pages, photographs, and
drawings into digital form.
Types of scanners:
Flatbed
Sheet-fed
Handheld
Quality of scanned images
are measured by resolution.
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Optical Mark Readers (OMRs)
Read opticalmarks, such ason:
Exams
Census forms
Voting ballots
Lottery forms
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Bar-Code Readers
Bar codean optical code consisting ofseveral bars of varying widths that form a
unique, identifiable code. Read by fixed or portable bar-code readers.
Common types:
Universal Product Code (UPC)
POSTNET code
Proprietary codes for shippers, hospitals, and
other businesses
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Optical Character Recognition
(OCR) Devices Optical charactersare designed to be
identifiable by humans as well as OCR device.
Widely used in turnaround documents, such as
monthly bills.
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Magnetic Ink Character
Recognition (MICR) Readers
MICR readerscan read the
specialmagneticcharactersand sort andprocessdocumentsaccordingly.
Used primarily for processing checks.
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Multimedia Input Devices
Digital cameras record data onto digital mediainstead of conventional film or tape.
Images can be transferred to a PC via a cable orthe storage media (such as a flash memory card
with a digital still camera).
Can be digital still camerasordigital videocameras.
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Digital Cameras
Digital cameras capture snapshots
and store them as bit patterns on
disks or other storage media.
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Multimedia Input Devices,
Contd.
Digital still cameras
Images are usually stored on flash memory cards.
Photos can usually be immediately previewed and deleted, ifneeded.
Photos are easily transferred to a PC to be stored and/or
printed.
Camera quality is measured in mexapixels.
Digital photos can be printed at home or at a photo lab.
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Multimedia Input Devices,
Contd. Digital video cameras
Store images on digital media (typically digital
tape or optical discs).
Video can be easily transferred to a PC for editing
and/or burning onto a DVD.
Can be used for videoconferencing and Webcams.
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Multimedia Input Devices,
Contd. Audio input devices
Voice-input systems convert spoken words todigital data.
Voice input can be used to input data or
commands into a PC as well as fortelephony.
Music-input systemscan input and record music(either original compositions or via a CD or DVD
player).
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Sensing Devices
Sensing devices are used to monitor
temperature, humidity, pressure and other
physical quantities.
The data collected provides data for use in
robotics, environmental climate control,
weather forecasting and other
applications.
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Output: From Pulses to People
Screen Output
Paper Output
Sound Output
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Screen Output
A monitor or video display terminal (VDT)
displays characters, graphics,
photographic
images, animation and video.
Video adapterconnects the monitor to thecomputer
VRAM or video memorya special portion ofRAM to hold video images (the more video
memory, the more detail of a picture
displayed)
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Display Devices
Display device characteristics
Color vs. monochrome displays
Size (measured diagonally)
Screen resolution
Graphic standards
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Display Devices, Contd.
CRT (cathode-ray tube) monitorsdisplay images
similar to conventional televisions.
Quality is measured in dot pitch.
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Screen Talk
Monitor size - measured as a diagonalline across the screen.
Pixels (or picture element) - tiny dots thatcompose a picture
Resolution- the number of pixels
displayed on the screen (the higher theresolution, the closer together the dots)
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Image Quality
Image quality is
affected by resolution
and color depth (or bit
depth)
Color depth refers to
the number of
different colors a
monitor displays at
the same time
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Examples of Color Depth
1-bit depth
16-bit depth8-bit depth
4-bit depth
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Monitor Classes
CRT (cathode ray
tube) LCD (liquid crystal display)
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Display Devices, Contd.
Flat-panel displaysform images bymanipulating electronically-charged chemicalsor gases between thin panes or glass orplastic.
Common types:
Liquid crystal displays (LCD)
Gas plasma
Used for monitors, televisions, handhelddevices, and other consumer products.
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Liquid Crystal Display (LCD)
Light-weight
Compact
Flat-panel Used in overhead projection panels and
video projectors to project computer
images
More expensive than CRTs
Increasingly being seen with desktop
computers
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Paper Output
Printers produce
paper output or hardcopy
2 kinds of printers:
Impact printers
Non-impact
printers
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Impact Printers
Line printer
Used by mainframes to
produce massive printouts
Limited to printingcharacters
Dot matrix printer
Images created by amatrix of tiny dots
Low print quality
Low cost
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Non-impact Printers
A laser beam reflected
off
a rotating drum tocreate patterns of
electrical charges
Faster and moreexpensive
than dot matrix printer
High-resolution output
Laser Printer
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Laser Printers
The standard for business documents.
Work similarly to photocopy machines; printwith toner powder.
Are usually black and white, though colorlaser printers are available.
Fast print speed; print one page at a time.
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More on Non-impact Printers
Sprays ink onto paperto produce printed textand graphic images
Prints fewerpages/minute thanlaser printer
High-quality colorcosting less than laserprinter
Ink-jet Printer
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Ink-Jet Printers
Print with tiny drops of liquid ink.
Typically print in color.
Often the choice for home use.
Print fairly slowly, one line at a time.
Quality not quite as good as a laser printer.
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Special Purpose Printers
Photo printers
Bar-code printers
Label printers
Portable printers
Plotters and wide-format
ink-jet printers
Fax machines
Multifunction devices
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Additional Output Devices
Multifunction peripheral or MFP combines
a scanner, printer and a fax modem.
A plotter is an automated drawing tool that
can produce large, finely scaled
engineering blueprints and maps.
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Output You Can Hear
A sound card allows the PCto accept microphone input,
play music and other sounds
through speakers orheadphones.
Synthesizers are included in
sound cards and havespecialized circuitry designed
to generate sounds
electronically.
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Multimedia Output Devices
Speakers
Voice-output
systems
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