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