Transcript Concept of Computer Communication

Computer Studies
Computer
Communication
and Networking
Table of contents
 Concept of computer communication
 The need for networking
 Types of networks
 Network topology
 Means of communication
 Use of world wide web (W W W)
Concept of computer
communication
Concept of computer
communication
Telephone Line
Stage of communication
• Encoding
• Transmission
• Decoding
Where do each
stage take
place ?
by telephone line
modem
Sending device
modem
Receiving device
Encoding
• Information (e.g. data, text, voice or video)
from the sending device is converted into
signals which the communication medium
can carry
010110
Sending device
send digital signal
Receiving device
receive analog signal
Transmission
• The signals are transmitted through the
medium to the receiving device
Signal transmitted
by telephone line
by telephone line
modem
Sending device
modem
Receiving device
Decoding
• The signals are converted back into the
information in its original form in the receiving
device
010110
Sending device
send analog signal
Receiving device
receive digital signal
Computer Network
Workstation
Workstation
Server
Printer
Scanner
Workstation
This is the end of
Concept of Computer Communication
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The need for networking
Sharing of resources
Can I use
the Laser
Printer ?
How ?
Sharing of resources
Connected
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
better security
measures
centralized
control over all
facilities and
resources
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
Server
Install
new
software
Use new
software
Use new software
Use new
software
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
Workstation
New Workstation
Server
New Scanner
New Printer
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
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Types of networks
-A
Within
Local
L
AANAN
Area
N a room,
Network
N floor or building
- Within a large city
- Optical fibers as media
Metropolitan
M
AA
N NA
Area
A
N
Network
N
Wide
W
AANAArea
A N Network
N
N
- link small networks in different
geographic area
I Love U !
I Love U too !
LAN
LAN
LAN
This is the end of
Types of Networks
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Network topology
It refers to the way by
which the network
hardware (called
nodes) are arranged
and the means if data
flow.
Star architecture
Yes, I can
hear you
Transferring
Host
Hello?
Node
Star architecture
????
I can’t work!
Host
Hello?
Node
Star architecture
Yes, I can
hear you
Transferring
Host
Hello?
Node
Star architecture
• Host fails,
– whole network breaks down
• Node fails,
– network not affected
• Configuration is simple
Ring architecture
I know u love me,
but I hate u !
PC1, I love U!
Oh, not for me, I will
pass the message
All Computer
are nodes
Ring architecture
????
PC1, I love U!
Oh, I can’t transfer
your message!!
Ring architecture
• All computers are
– Nodes
• If any node fails,
– whole network break down
What! The deadline
It’s
message,
hasmy
changed??
I will pick it up
Bus architecture
Node
Not my message,
I won’t pick up
Not my message,
I won’t pick up
BUS
Not my message,
I won’t pick up
You have to hand
in your homework
today!
What! The deadline
It’s
message,
hasmy
changed??
I will pick it up
Bus architecture
Node
Not my message,
I won’t pick up
BUS
Not my message,
I won’t pick up
You have to hand
in your homework
today!
Bus architecture
• All Nodes connected to
– BUS
• If any node fails,
– network not affected
This is the end of
Network Topology
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Means of
communication
Two ways of transmission data:
1.Direct mode transmission
Signals are
transmitted to a
particular receiver
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
More reliable as
it is better
insulated
An insulating material
protect the copper wire
Used for
connecting a TV
set to public
antenna
3. Optical fibre
• Very expensive transmission
medium
• Not subject to electrical
disturbance
• Suited for long distances
communication in high data rate
- Light passes
along the coated
fine cylindrical
glass tubing by
reflection
Broadcast mode transmission
Satellite transmission
Ground station
receive the data
and beam to
the satellite by
microwave
Satellite will retransmit data to
another ground
station
This is the end of
Means of Communication
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Use of world wide
web(WWW)
Can communicate
with other people or
access information
worldwide
A global network
link many
networks
The Internet
Use Web Browser to
browse through
Internet
What is Web Browser ?
Web Browser is a software to:
1.
2.
3.
Traverse the links in the Web
Communicate with servers
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. 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
Web 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 shower
http://www.glink.net.hk/~sohk/leonid/enter.htm
• Games
– Cow boy
http://www.shinenet.com.tw/fashion/game92/index.html
– Matching Games
http://personal.cityu.edu.hk/~96013494/matching/
– Game
http://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 Web
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