Input / Output (I/O) Devices

•

Data Entry Input Devices

•

Keyboard

- QWERTY – function keys – numeric keypad •

Pointing Devices

– Mouse – Light pen – Joystick – Trackball – Touchpad (notebooks) – Touch Screen Comp 1001: IT & Architecture - Joe Carthy 1

Input / Output (I/O) Devices

•

Data Automation Input Devices

–

OCR

: Optical Character Recognition • Utility Bills: ESB • Typically use special font e.g. OCR1 –

OMR

: Optical Mark Recognition • (e.g. lotto tickets) –

Image scanner

• OCR software • DIP: Document Image Processing e.g. for CAO forms –

Bar code Scanner

• Reads an optical code • Universal Product Code:

UPC

• (supermarket checkouts/ libraries) • Often used as key component of Point-of-Sale system (

POS

) Comp 1001: IT & Architecture - Joe Carthy 2

Input / Output (I/O) Devices

•

Digital Camera

• •

Voice recognition

(e.g. Viva Voice by IBM, Dragon) •

Handwriting recognition

• HP Ipaq; Palm Pilot •

Smart Cards

• contain a processor e.g. Telecom phonecards •

MICR

Magnetic ink character recognition • Used on bank cheques Comp 1001: IT & Architecture - Joe Carthy 3

Output Devices

•

Display devices

: e.g. computer

monitor

use with PCs.

is what most people • A

computer terminal

It is a

dumb

is made up of a monitor and a keyboard. device unlike a PC. Terminals may be used to access a

mainframe

computer. • Screen size varies from

15 to 27 inches

, measured

diagonally

across the screen.

•

Resolution

• Images are usually made up of tiny “dots” called elements). The higher the resolution , the better the quality of picture.

pixels

(picture 4 Comp 1001: IT & Architecture - Joe Carthy

Output Devices

• Resolution may be measured by either

–

pixel density

e.g. .26 or .28

– (distance between pixels in millimetres)

or

– as a

matrix of pixels

– 640 x 480 rows e.g. 640 x 480

VGA standard

– 800 x 600 – 1024 x 768

SVGA standard XGA standard

– 1080 x 1024 – 1600 x 1200

SXGA standard UXGA

Comp 1001: IT & Architecture - Joe Carthy 5

Output Devices

•

Colour

• Most monitors are RGB (red-green-blue) i.e. form colours by combinations of primary colours.

• Most monitors produce

non-interlaced

images i.e all lines are redrawn when the screen is refreshed. TVs produce

interlaced

images i.e every other line is redrawn on every refresh.

• The screen is usually refreshed 60 times a second.

6 Comp 1001: IT & Architecture - Joe Carthy

Output Devices

•

Landscape

: Screen is wider than it is high •

Portrait:

Screen is higher than it is wide • •

CRT versus Flat-Panel

Desktop monitors are typically

CRT

TVs, although flat screens are becoming more popular as they take up less space but are more expensive.

(cathode-ray tube) devices like • Notebooks use

flat-screens

lightweight.

which require less power and are • Flat-screens often use

LCD

(liquid crystal display) technology.

•

Active-matrix

LCDs provide sharper images than

passive-matrix

LCDs but at higher cost.

7 Comp 1001: IT & Architecture - Joe Carthy

Output Devices: Printers

•

Variety of Print technologies

•

Ink-jet

: high quality and very popular: Usually Colour •

Laser

– (page printer): highest quality

Colour laser printers are much more expensive than black&white

•

Cost

of ink-jet cartridges/colour toner is an issue in choosing a printer •

Dot-matrix

: good quality largely replaced by ink-jet •

Line-printers

: Fast, low quality bulk printing on computer paper 8 Comp 1001: IT & Architecture - Joe Carthy

Output Devices: Others

•

Plotters:

for CAD (Computer Aided Design) output – architectural/engineering drawings – A3 laser printers now also used for these applications • •

Speakers

As in sound systems • •

Computer Output on Microfilm

(COM) e.g. for archival purposes Comp 1001: IT & Architecture - Joe Carthy 9

Communications Devices

•

Modem: Modulator/demodulator

– Uses to allow computers communicate over analog telephone lines – Converts computer digital signals to analog signals and vice versa – Operates at speeds up to 56Kbps –

bps = bits per second

•

ISDN Card

• Digital communication device requires

digital phone

line • Operates at speeds from 64Kbps, 128 Kbps (home use) to low Megabit range • Much more reliable than modem •

DSL/ADSL Card

• Similar to ISDN but operates at much higher speeds (140Kbps to 3 Mbps) •

Network Card

(Ethernet card, LAN card): • Short Distances (<1000m) • • used inside an organisation like UCD

10Mbps

to

100Mpbs

to 1000 Mbps Comp 1001: IT & Architecture - Joe Carthy 10

Computer System: Storage and I/O Devices

Printe r Phone Socke t Spe ake rs Mode m Computer Mouse Monitor and Ke yboard CD-ROM Tape Unit Disk Unit

Comp 1001: IT & Architecture - Joe Carthy 11

I/O Devices and Communication Devices: Review

• • •

Data entry

– Keyboard, mouse, joystick, light pen, touch pad etc – OCR, OMR, Barcode scanner, DIP, MICR – Digital Camera, Voice, Smart Cards

Output

–

Monitor

(VGA, SVGA, XGA etc) • CRT, LCD –

Printer

• Inkjet, Laser, Dot-Matrix – –

Plotter Speakers Communication Devices

• Modem • ISDN • ADSL/DSL • Network Card 12 Comp 1001: IT & Architecture - Joe Carthy