2. Peripheral Devices
Peripheral Devices are the devices that are
linked internally or externally to a computer.
These devices are used to transfer data.
3. Types of Peripheral Devices
Peripheral Devices are of three types:-
Input Devices
Output Devices
Storage Devices
6. Input Devices (3)
Scanning devices
– Image scanner
– Fax machine – scan image to bitmap
– Bar code scanner – scan Universal Product Code
(UPC)
– Magnetic ink character scanner (MICR)
– Optical character scanner (OCR)
– Optical mark scanner (OMR)
7. Input Devices (4)
Voice Input Device
– Microphone – to receive the sound signal
– Sound card – to convert the sound signal to digital
form
– Use speech recognition software to recognize
human speech
9. Output Devices (1)
Visual Display Unit (VDU)
– Commonly called monitor
2 common types of monitor
– CRT (Cathode Ray Tube) monitor
High radiation and bulky
– LCD (Liquid Crystal Display) monitor
No radiation and slim
10. Output Devices (2)
Printer – to produce hard copy
Laser printer
– to produce high quality output
– resolution up to 2400 dpi (dot per inch)
– use carbon toner, usually for black and white
printout, colour is very expensive
11. Output Devices (3)
Inkjet printer
– produce good quality colour output
– resolution up to 1440 dpi
– use ink droplets to compose the image
– The printer is much cheaper than laser printer but
the ink is very expensive
12. Output Devices (4)
Dot matrix printer
– Use impact principle
– Can print multiple (carbon) copies at a time, usually
use in printing invoices
– The ink ribbon is cheap
– Poor quality of printout
13. Output Devices (5)
Plotter
– Drawing high quality image, use colour pens, can
draw smooth curves
– Can print on large paper size, use roll of paper
– To draw posters and maps
– Use in CAD (Computer Aided Design)
14. Output Device (6)
Voice output devices
– Sound card, to convert computer signals to sound
– Speakers, to amplify the sound output
15. Storage Devices (1)
Floppy Disk (Diskette)
– A flexible plastic circular disc
– Packed in a plastic square jacket
– Formatted to 1.44MB
– Divided to many circular tracks
– Each track is divided to many sectors
– Use magnetic technology to store data ‘0’ or ‘1’
– Random access
– Slow accessing speed
16. Storage Devices (2)
Hard Disk
– High storage capacity, over 100 GB
– Hard metallic surface
– Consists of several metallic disks
– Data are stored in cylinder (a deck of tracks)
(see p.86)
– Use magnetic technology
– Very high access speed
– Random access
17. Storage Device (3)
Optical disk
– CDROM, DVDROM, CDRW, DVDRW
– Use optical technology, laser reflection on pits
– ‘1’ will reflect the laser beam while ‘0’ does not
– High storage capacity, 700 MB for a CDROM,
17GB for a DVDROM
– Random access
– High access speed
18. Storage Device (4)
Tape
– Cheap
– Sequential access
– Use magnetic technology
– Ideal for backup data, we need to backup and restore all
data
– High storage capacity
– Slow access speed
– Group of records are stored in a block
– Inter-block gaps are needed for stopping and starting the
read/write head.
19. Storage Device (5)
Other Storage devices – can be read/write
Removable disks -Zip disk(100/250MB),
superdisk(120MB), Jazz disk(1GB)
MO disk
Flash memory cards – compact flash, smart
media and memory stick, commonly used in
digital camera
20. Network Devices (1)
Network Interface Card (NIC) (LAN card)
– Connection between the network and the computer bus
– Have built-in transceiver, for data transmitting and receiving
– Usually 100 MB/s
Wireless LAN card
– Usually 11 MB/s
– Work within the distance range, and no blocking in between.
21. Network Devices (2)
Connectors
RJ-45 telephone jack connector
– For connecting twisted pairs LAN cable
BNC connector
– For connecting coaxial cables
22. Network Device (3)
Terminators
– Use in bus network, to prevent signal rebounce and
echo at the ends of bus.
23. Network Device (4)
Hub
– To connect the workstations within a room on same
floor
Switch
– To connect the workstations for different floors in a
building, it is faster and more efficient than a Hub.
Router
– To connect different LANs together to form a Wide
Area Network (WAN)
24. Network Device (5)
Repeater
– When a network spans a long distance, the signal
weaken, repeater is used to reproduce the signal.
Exchange
– To boost the signals along the network path for a
Wide Area Network.
25. Network Device (6)
Computer
– Different computers play different roles on a network
Server
– Provide services to other computers connected to
the network, usually have higher processing power
and larger storage capacity.
Workstation
– The computers connected to the network but not act
as a server.
26. Network Device (7) - Servers
File server
– control the sharing and access of files over the network,
must have a huge storage capacity.
Print server
– Manage the print jobs from different computers to different
network printers, and manage the print queues.
Web server
– To host a web site and publish web pages on the web,
support HTML, Java script, CGI, PHP and ASP web
languages
Email server
– To store, send and receive emails over the Internet
Internet server
– To provide Internet access
27. Types of network
Client-Server Network
– Some computers act as server to provide services to clients
on the network
– Server programs are running on the server
– Client programs are running on client computers
Peer-to-peer Network
– Every computer plays the same role in the network. They
form a workgroup, no server and no client
– The security in a peer-to-peer network is low.
– It is easy to set up, since no server programs or client
programs need to be run.
