Chapter 6: Input & Output

Taking Charge of Computing &

Communications

Key Questions6.1 How is input and output hardware used by a

computer system?

6.2 What are the three categories of input hardware, what devices do they include, and what are their features?

6.3 What are the two categories of output hardware, what devices do they include, and what are their features?

6.4 What are some examples of the future of input and output technology?

I. Input Hardware

Keyboards

Pointing Devices

Source Data-Entry Devices

II. Pointing Devices Mice, Trackballs, & Joysticks

– Mouse– Trackball– Pointing stick– Touchpad

Light Pen Digitizing Tablet Pen-Based Systems

III. Common Hardware for Source Data-Entry Bar-Code Readers

– Bar codes(Universal Product Code or UPC) Mark-Recognition & Character-Recognition

– Magnetic-ink char recognition (MICR)• Banking industry

– Optical-mark recognition (OMR)• Tests and examinations

– Optical-char recognition (OCR)• Utility companies using turn-around documents• Convert printed text to digital form

Checks use magnetized ink thatcan be read by a bank’s magnetic-ink character-recognition equipment.

MICR technology

Other Input Devices

Scanning Devices: Imaging Systems– Flatbed image scanners– Sheetfed image scanners– Handheld image scanners

Audio-Input Video-Input Digital Cameras

Summary of input devices

IV. Output Hardware

Softcopy– data that is shown on a display

screen or is in audio or voice form Hardcopy

– Printed on paper, microfilm and microfiche

V. Softcopy: Display Screens Cathode-Ray Tubes (CRTs) Flat-Panel Displays

– Substances between plates• Liquid crystal display (LCD)• Electroluminescent (EL) • Gas-plasma display

– Arrangements of transistors.Active-matrix:brighter, sharper and $$$ .Passive-matrix: need less power

How a CRT works

Display Screen Screen Clarity

– Resolution: image sharpness• horizontal & vertical pixels: 800x600, 1024x768

– Dot pitch: space between adjacent pixels• dot pitch < .31 millimeter provide clear images

– Refresh rate: • how often the pixels are recharged

Monochrome Versus Color Screens Bitmapped Displays Video Display Adapters

VI. Hardcopy Output Impact Printers

– Print char or images by striking a mechanism (hammer) against an inked ribbon, leaving an image on paper

– Dot Matrix Printer Nonimpact Printers

– Laser printer– Ink-jet printer– Thermal printer

Type Technology Advantages Disadvantages TypicalSpeed

ApproximateCost

Dot-matrix IMPACT: Printhead strikes aninked ribbonagainst paper

Inexpensive; outputchar & graphics; canprint multi-part forms;low cost per page

Noisy; low quality 30 to500+cps*

$100-$2000

Laser Laser beamdirected onto adrum, “etching”spots that attracttoner, which isthen transferredto paper

Quiet; excellentquality; output of textand graphics; veryhigh speed

High cost,especially for color

8-200ppm*

$500-$20,000

Ink-jet Electrostaticallycharged dropshit paper

Quiet; prints color,text, and graphics;less expensive; fast

Relatively slow;clogged jets; fewerdots per inch

35-400+cps

$150-$2000

Thermal Temperature-sensitive paperchanges colorwhen treated;

Quiet; high-qualitycolor output of textand graphics

Special paperrequired;expensive; slow

11-80cps

$2000-$22,000

*cps = characters per second; ppm = pages per minute

Printer comparisons

In & Out Terminals:

– Used to access another machine– Monitor & Keyboard– Dumb: no local processing power– Intelligent: CPU and RAM– Special Purpose: Point-of-sale (POS)

Touch Screens

Summary of output devices