Input/Output Devices
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Transcript Input/Output Devices
Input/Output Devices
Chapter 5b
Input
Allow input into computer
Data
Commands
Responses
Programs
Most popular input devices are keyboard and
mouse
Keyboard
Features
QWERTY layout
12 function keys
Numeric keypad
Cursor control key
Special function keys
Connectors
PS/2, USB, IrDA (wireless infrared)
Mouse
Point-and-draw device
Used in GUI interfaces
Controls on-screen pointer or cursor
Click, double-click, drag
Mechanical mouse use ball pushed over flat surface
to generate mouse positions
Optical mouse uses low laser (LED) to generate
mouse positions
Other types include trackballs, track points, track
pads, joystick and digital pen
Connectors are PS/2, USB or IrDA
Data Source Automation
Reduces input errors
Computer generates data entry information at
the source f the data
Scanners used to read the data eliminating
need for key entry
Best known example is UPC or universal
product code
Data Source Automation
Other types
MICR,or magnetic ink character recognition =
used by banks to encode bank and account
information on checks
OMR, or optical mark recognition. Best example
is scantron used in tests and surveys
OCR, or optical character recognition. Reads
both printed and written text. Used by mail
services to read addresses and zip codes
Turnaround document are sent to customers and
returned with payments
Other inputs
Magnetic stripe cards
Data encoded on magnetic stripes
ATM cards, credit/debit cards, badges
Speech recognition or voice input. Requires
special software and quality microphone
Digital cameras and video recorders allow
input of digital pictures and videos.
Output
Output information from computer in form we
can read
Text, graphics, audio, video
Most popular output devices are monitor and
printers
Monitor = “soft copy”
Printer = “hard copy”
Monitors
Two basic technologies = CRT and flat panel
CRT = cathode ray tube
Older technology
Inexpensive
Bulky and power hog
Use same technology as TV picture tubes
Flat panel
Essential for laptops
Gaining popularity with desktops
Light, portable, power misers
More expensive
Most popular technology is LCD or liquid crystal display
Monitors (contd)
Require graphics adapter
Converts digital signals to format compatible with monitor
Cards may be integrated into motherboard or use AGP
expansion slot
Cards have their own VRAM or video RAM and processor
chip
Resolution = picture quality
Pictures displayed as pixels or dots on screen
Higher number of pixels = better resolution
Lower dot pitch (distance between pixels) = better
resolution
Printers
Two categories – impact and non-impact
Impact printers
Older technology
Print head strikes paper
Noisy, lower quality output
Advantage is the ability to print carbon copies
(with appropriate paper!)
Best example is dot-matrix printer
Printers (contd)
Non-impact
Print heads do not touch paper
Quiet, higher quality printout
Ink-jet printer
Sprays ink droplets on paper to form text and graphics
Energy efficient
Refill cartridges are expensive
Laser printer or page printer
Same toner technology as copy machines
Produce one page at a time
Faster than ink jet printers but power hogs
Other output devices
Speakers
Speech synthesis systems = use text-tospeech software to produce speech