Presentation on theme: "Computer Studies Computer Communication and Networking."— Presentation transcript:
Computer Studies Computer Communication and Networking
Table of contents C oncept of computer communication T he need for networking T ypes of networks N etwork topology M eans of communication U se of world wide web (W W W)
Concept of computer communication
Stage of communication Encoding Transmission Decoding Where do each stage take place ? Sending deviceReceiving device
Encoding 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
Transmission The signals are transmitted through the medium to the receiving device Sending device Receiving device Signal transmitted by telephone line
Decoding 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
Computer Network Server Scanner PrinterWorkstationWorkstation Workstation
This is the end of Concept of Computer Communication Back to Table of Content Next Section
The need for networking
Sharing of resources Can I use the Laser Printer ? How ?
Sharing of resources Connected
Sharing 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 another Mac IBM PS/2
Communicate with one another 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 Better security The network supervisor centralized control over all facilities and resources better security measures
Centralized control and Better 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 management Install new software Use new software software Use new software Server
Easier software management 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 location Server New Scanner New Printer New Workstation Workstation Workstation
Flexibility 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 Networking Back to Table of Content Next Section
Types of networks
Local Area Network NALNALNALNAL - Within a room, floor or building FAST!
Metropolitan Area Network NAMNAMNAMNAM - Within a large city - Optical fibers as media
LAN LAN LAN I Love U !I Love U too ! Wide Area Network NAWNAWNAWNAW - link small networks in different geographic area
This is the end of Types of Networks Back to Table of Content Next Section
Network topology It refers to the way by which the network hardware (called nodes) are arranged and the means if data flow.
Star architecture Host Node Hello? Transferring Yes, I can hear you
Star architecture Host Node Hello? I can’t work!????
Star architecture Host Node Hello? Transferring Yes, I can hear you
Star architecture Host fails, – whole network breaks down Node fails, –network not affected Configuration is simple
Ring 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 architecture PC1, I love U! ???? Oh, I can’t transfer your message!!
Ring architecture All computers areAll computers are –Nodes If any node fails,If any node fails, –whole network break down
Bus architecture BUS Node You have to hand in 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 deadline has changed?? It’s my message, I will pick it up
Bus architecture BUS Node You have to hand in your homework today! Not my message, I won’t pick up Not my message, I won’t pick up What! The deadline has changed?? It’s my message, I will pick it up What will happen?
Bus architecture All Nodes connected toAll Nodes connected to –BUS If any node fails,If any node fails, –network not affected
This is the end of Network Topology Back to Table of Content Next Section
Means of communication
1.Direct mode transmission Signals are transmitted to a particular receiver Two ways of transmission data:
2. Broadcast mode transmission Signals are transmitted to all directions
Direct mode transmission 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 antenna More 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 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 Communication Back to Table of Content Next Section
Use of world wide web(WWW) The Internet A global network link many networks Can communicate with other people or access information worldwide Use Web Browser to browse through Internet
What is Web Browser ? Web Browser is a software to: 1.Traverse the links in the Web 2.Communicate with servers 3.Retrieve data
Two popular Web Browsers 1. Netscape 2. Internet Explorer
Use 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. Type in the address and press enter
After that, you can browse the home page that you wanted.
Suggestions of Interesting Web Sites Newspapers –Singtao Daily News –Apple Daily News
Christmas Card Web Site Meteor shower
Games –Cow boy
Comics – 叮噹網頁
This is the end of Use of World Wide Web Back to Table of Content