input/output devices chapter 5b. input allow input into computer data commands responses programs...
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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-to-
speech software to produce speech
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