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Computer StudiesComputer Studies
Computer Communication and Networking
Table of contentsTable of contents
CConcept of computer communicationoncept of computer communication
TThe need for networkinghe need for networking
TTypes of networksypes of networks
NNetwork topologyetwork topology
MMeans of communicationeans of communication
UUse of world wide web (W W W)se of world wide web (W W W)
Concept of computer Concept of computer communicationcommunication
Concept of computer Concept of computer communicationcommunication
Telephone Line
Stage of Stage of communicationcommunication
• Encoding
• Transmission
• Decoding
m odem m odem
by telephone line
Where do each stage take
place ?
Sending device Receiving device
EncodingEncoding
• Information (e.g. data, text, voice or video) from the sending device is converted into signals which the communication medium can carry
Receiving device receive analog signal
Sending device send digital signal
010110
TransmissionTransmission
• The signals are transmitted through the medium to the receiving device
m odem m odem
by telephone line
Sending device Receiving device
Signal transmitted by telephone line
DecodingDecoding
• The signals are converted back into the information in its original form in the receiving device
Sending device send analog signal
Receiving device receive digital signal
010110
Computer NetworkComputer Network
ServerServer
ScannerScannerPrinterPrinter
WorkstationWorkstation
WorkstationWorkstation
WorkstationWorkstation
This is the end of
Concept of Computer CommunicationConcept of Computer Communication
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Next Section
The need for The need for networkingnetworking
Sharing of resourcesSharing of resources
Can I use the Laser Printer ? How ?
Sharing of resourcesSharing of resources
Connected
Connected
Sharing of resourcesSharing of resources
• Sharing : data, programs and hardware
• Data and software can be centrally stored in a computer acting as the file server and accessed by any computer in the network
• An expensive laser printer can be connected to a computer which serves as a print server and processing printing jobs from other computers
Communicate with one Communicate with one anotheranother
MacMac IBM PS/2IBM PS/2
Communicate with one Communicate with one anotheranother
• Different types of computers store data files using different internal representation methods
• A network operation system can automatically convert the files into the required representations before they are transferred
Centralized control and Centralized control and Better securityBetter security
The network supervisorThe network supervisor
centralized control over allfacilities and resources
better security measures
Centralized control and Centralized control and Better securityBetter security
• The network supervisor can have a centralized control over the use of all facilities and resources
• including all data, programs, disk spaces and other hardware
• better security measures can be applied
Easier software Easier software managementmanagement
Installnew
software
Use newUse newsoftwaresoftware Use new Use new
softwaresoftware
Use new softwareUse new software
ServerServer
Easier software Easier software managementmanagement
• When a new applications is developed and installed in the server, workstation can immediately use it from any computer
• upgrading or changing software is simpler because it is now stored in the single file server but not distributed among different computers
Flexibility of locationFlexibility of location
ServerServer
New ScannerNew Scanner
New PrinterNew Printer
New WorkstationNew Workstation
WorkstationWorkstation
WorkstationWorkstation
Flexibility of locationFlexibility of location
• Any computer on the network can be used to access the centralized database or the software and data in the file server
• it is fairly easy to add a workstation anywhere, relocate a computer to another site, to add a new printer or any other resources
This is the end of
The Need for NetworkingThe Need for Networking
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Next Section
Types of networksTypes of networks
Local Area NetworkLocal Area NetworkNNAALL NNAALL NNAALL NNAALL - Within a room, floor or building
FAST!
FAST!
Metropolitan Area NetworkMetropolitan Area NetworkNNAAMM NNAAMM NNAAMM NNAAMM - Within a large city
- Optical fibers as media
LANLAN
LANLAN
LANLAN
I Love U !I Love U too !
Wide Area NetworkWide Area NetworkNNAAWW NNAAWW NNAAWW NNAAWW - link small networks in different geographic area
This is the end of
Types of NetworksTypes of Networks
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Next Section
Network topologyNetwork topology
It refers to the way by which the network hardware (called nodes) are arranged and the means if data flow.
Star architectureStar architecture
HostHost
NodeNodeHello?
Transferring
Yes, I can hear you
Star architectureStar architecture
HostHost
NodeNodeHello?Hello?
I can’t work!
????
Star architectureStar architecture
HostHost
NodeNodeHello?
Transferring
Yes, I can hear you
Star architectureStar architecture
• Host fails,– whole network breaks down
• Node fails,– network not affected
• Configuration is simple
Ring architectureRing architecture
All Computer are nodes
PC1, I love U!
Oh, not for me, I will pass the message
I know u love me, but I hate u !
Ring architectureRing architecture
PC1, I love U!
????
Oh, I can’t transfer your message!!
Ring architectureRing architecture
• All computers are All computers are – NodesNodes
• If any node fails,If any node fails,– whole network break downwhole network break down
Bus architectureBus architecture
BUSBUS
NodeNode
You have to handin your homework
today!
Not my message,I won’t pick up
Not my message,I won’t pick up
Not my message,I won’t pick up
What! The deadlinehas changed??It’s my message,
I will pick it up
Bus architectureBus architecture
BUSBUS
NodeNode
You have to handin your homework
today!
Not my message,I won’t pick up
Not my message,I won’t pick up
What! The deadlinehas changed??It’s my message,
I will pick it up
What will happen?
What will happen?
Bus architectureBus architecture
• All Nodes connected to All Nodes connected to – BUSBUS
• If any node fails,If any node fails,– network not affectednetwork not affected
This is the end of
Network TopologyNetwork Topology
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Next Section
Means of Means of communicationcommunication
1.Direct mode transmission
Signals are transmitted to a
particular receiver
Two ways of transmission data:Two ways of transmission data:
2. Broadcast mode transmission
Signals are transmitted
to all directions
Direct mode Direct mode transmissiontransmission
1.Twisted pair wires
Cheapest transmission medium
Susceptible to local electrical noises
Usually used for short distance
connections such as telephone line
2. Coaxial cable
Fairly cheap transmission
medium
An insulating material protect the copper wire
Used for connecting a TV
set to public antennaMore reliable as
it is better insulated
3. Optical fibre
- Light passes along the coated fine cylindrical glass tubing by reflection
• Very expensive transmission medium
• Not subject to electrical disturbance
• Suited for long distances communication in high data rate
Broadcast mode transmissionBroadcast mode transmission
Ground station receive the data and beam to the satellite by microwave
Satellite will re-transmit data to another ground station
Satellite transmission
This is the end of
Means of CommunicationMeans of Communication
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Use of world wide Use of world wide web(WWW)web(WWW)
The InternetThe Internet
A global network A global network link many link many networksnetworks
Can communicate Can communicate with other people or with other people or access information access information
worldwideworldwide
Use Web Browser to Use Web Browser to browse through browse through
InternetInternet
What is Web Browser ?What is Web Browser ?
Web Browser is a software to:
1. Traverse the links in the Web2. Communicate with servers3. Retrieve data
Two popular Web Two popular Web BrowsersBrowsers
1. Netscape
2. Internet Explorer
Use of Web BrowserUse of Web Browser
• You can see some shortcut key on the browser like this
• Address of Web Site is called URL(Uniform Resource Locator)
e.g. http://www.singtao.com
http://www.singtao.com
Type in the address and press enter
• After that, you can browse the home page that you wanted.
Suggestions of Interesting Suggestions of Interesting Web SitesWeb Sites
• Newspapers
– Singtao Daily News
http://www.singtao.com/
– Apple Daily News
http://apple.daily.com.hk/
• Christmas Card Web Site
http://www.comp.hkbu.edu.hk/~c6000171/xmas
http://www.casema.net/~pico/kerst/
• Meteor showerhttp://www.glink.net.hk/~sohk/leonid/enter.htm
• Games– Cow boy http://www.shinenet.com.tw
/fashion/game92/index.html
– Matching Gameshttp://personal.cityu.edu.hk/~96013494/matching/
– Gamehttp://personal.cityu.edu.hk/~96013494/fool/fool.htm
• Comics–叮噹網頁
http://home.hkstar.com/~fucp/fujiko/doraemon/dora.htm
This is the end of
Use of World Wide WebUse of World Wide Web
Back to Table of Content
