14. Computer Systems Output Devices

Output

What Is Output?

• Data that has been processed into useful form called information– Text– Graphics– Audio– Video

Impact on Society

What Are Output Devices?

• Any computer component capable of conveying information to a user– Display devices– Printers– Other display devices

• Data projectors• Fax machine• Multifunction devices

– Terminals

Display Devices• An output device that visually conveys text, graphics,

and video information• CRT Monitors

– Screen housed in a plastic or metal case– Cathode ray tube (CRT)– Picture elements (Pixels)– Viewable size

• 17” monitor 15.7” viewable size– Colour vs. monochrome monitor

• Colour monitor and colour depth• Monochrome monitor and gray scaling

Display Devices

• Flat-panel displays– LCD displays

• Lightweight• Used by handheld computers, digital watches,

calculators• Active (TFT) and passive-matrix displays

– Number of transistors– Cost, sharpness and clarity of images– Also used with desktop computers with space and weight

constraints

Display Devices

• Flat-panel displays– Gas plasma

• Large displays of up to 42” of viewable area• Gas glows that produce pixels that form an image• Higher display quality• More expensive

Display Devices

• Factors that affect monitor quality– Resolution

• Related to the number of pixels it can display• Higher resolution

– Increased sharpness– Smaller images

• Number of columns of pixels X number of rows of pixels– Dot pitch

• Vertical distance between each pixel on a monitor• Measure of image clarity• The smaller the distance between each pixel, the sharper the

image

Display Devices

• Factors that affect monitor quality– Refresh rate

• Speed that the monitor redraws images on the screen• Measured in Hertz (Hz) to measure flicker• The higher the refresh rate, the lower the flicker

– Interlacing• Old method of refreshing images

Display Devices

• Video Cards– Graphics card, video adapter– Converts digital output into an analog video signal that

is sent through a cable to a monitor– Number of colours number of bits used to store

information about each pixel• 8-bit card (28 colours = 256 colours)• 24-bit card (224 colours = 16.7 million colours)

– Video RAM• Memory to generate the resolution and number of colours you

want to display

Video Card Display

Video Standards

Display Devices

• Monitor Ergonomics– Incorporate comfort, efficiency and safety into

the design of items in the workplace• Digital controls help fine-tune the display• Tilt-and-swivel base to minimise neck strain and

reduce glare• MPR II standard regarding electromagnetic

radiation (EMR)• ENERGY STAR program to create energy-efficient

monitors

Display Devices

• High-Definition Television– Uses digital television signals– Can be used as a monitor while browsing the

Internet– Monitor come TV– HDTV

Printers

• An output device that produces text and graphics on a physical medium such as paper or transparency film– Hard copy (printout)

vs. softcopy (monitor)– Portrait vs. landscape– Printing requirements

vary

D o t-m a trix

L ine

Im pa ct

In k -je t

L a ser

T h e rm al

P o rta b le

P lo tte rsa nd

L a rge F orm a t

N o n -im p a ct

P rin te rs

Printers

• Impact Printers– Printing mechanism strikes paper, ribbon and character

together– Near letter quality (NLQ)– Used for multipart forms

• strikes through multiple layers of paper

Printers

• Impact Printers– Dot matrix printers

• Small dots form characters• Continuous form paper• More pins on print head means higher quality• Speed measured in characters per second (cps)

Printers

• Impact Printers– Line printers

• High speed• Prints an entire line at a time• Band printer• Shuttle-matrix printer

Printers

• Non-impact Printers– No mechanism strikes the paper– Much quieter than impact printers– Ink-jet printers

• Spray tiny drops of ink onto the paper• Both black-and-white and colour• Resolution measured in dots per inch

(dpi)• Speed measured in pages per minute

(ppm)• Nozzles spray ink

Printers

• Non-impact Printers– Laser printers

• High-speed, high-quality non-impact printer• Very high quality resolution - 300dpi to 1,200 dpi• Stores entire page before printing it• Page description language (PDL)

– PCL (Printer Control Language)– Postscript

• Operates much like a copy machine• Toner• Replace cartridge

Printers

• Non-impact Printers– Thermal printers

• Pushes electrically heated pins against heat-sensitive paper

– Thermal transfer printer• Print head heats and melts the ink of the ink

ribbon to print the dot-composed character on normal paper

Printers

• Non-impact Printers– Portable printers

• Small, lightweight printer that allows a mobile user to print from a laptop or handheld computer while traveling

• Ink-jet• Thermal • Parallel port or infrared port

Printers

• Non-impact Printers– Plotters and Large-Format Printers

• Used for high-quality drawings such as blueprints, maps, circuit diagrams, and signs

• Plotters– Pen plotters– Electrostatic plotters

• Large-format printer– Photo-realistic quality color prints

Printers

• Non-impact Printers– Special-purpose printers

• Snapshot printer– Photo lab quality pictures

• Label printer

Audio Output

• Audio output devices– Produce music, speech, or other sounds– Speakers

• Low-quality sound• For high quality sound

– Stereo speakers and woofer– Sound card

– Headsets

Other Output Devices

• Data projectors– Allows an audience to view output– LCD projectors– Digital light processing (DLP) projector

• Facsimile (Fax) Machine– Used to transmit and receive an image of a document over

a phone line– Stand-alone– Fax modem

• Designed to transmit documents to a fax machine or to another fax modem

Other Output Devices

• Multifunction Devices– Can print, scan, copy, and fax– Less space– Lower cost than separate units– For example, OfficeJet by Hewlett-Packard is a

colour printer, scanner and photocopier all in one device

Terminals

• Performs both input and output– Monitor– Keyboard– Video card

• Dumb terminal• Intelligent (programmable) terminal

– Modern PC• Point-of-sale (POS) terminal• Automatic teller machine (ATM)

Output Devices For Physically Challenged Users

• Issues with output devices– Cannot see graphics because of visual

impairments– Cannot hear audio because of hearing

impairment• Possible solutions

– Windows Accessibility Properties dialog box– Braille printer

Output Devices For Physically Challenged Users

Output Device Users Guide

Web Surfing for the Blind

Computer Types and Architectural Characteristics

• Personal computer (PC)• Workstation• General-purpose computer• Supercomputer• Microcomputer• Process control computer

Personal Computer

• Desktop– Meant to be placed on a desktop

• Laptop– Portable computer which is slightly larger and

heavier than a notebook computer• Notebook

– A lightweight thin portable computer.

Mini Tower and Monitor

Notebooks (Mobile computing)

Workstation

• More powerful than the personal computers– Main applications are

• Research and development fields– Complex scientific and engineering calculations

• Product manufacturing fields– Used in CAD, CAM, etc application.

• Software development field– Computer Aided Software Engineering tool

• Communication network field– Client machines or server machines in distributed processing

system.

A Workstation

Supercomputer

• Capable of performing complex and large calculations at extremely high speed

• Main use– Weather forecast– Simulation of nuclear power generation– Orbit calculation of artificial satellites

SupercomputerFujitsu VPP700E: 256 Fujitsu CMOS processing elements

Microcomputer

A small computer with a microprocessor• Used in household appliances• Control data is recorded in ROM• Output devices are called actuators

– Motors or switches

Process Control Computer

• Computers that control machines in heavy industries– Machines entirely automated through process

control computers• Used in general building security system,

highway traffic control, etc.

General Purpose Computer (Mainframe)

• A very large and powerful computer capable of supporting thousands of users simultaneously.

• Mainframes are just below supercomputers in processing power

Laptops

Palmtops