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CHAPTER NO 11
NETWORK AND INTERNET
COMPUTER NETWORK
DEFINATION:
“A computer network is a group of computers which are connected together to allow communication between them.”
TYPES OF NETWORK
There are two main types of network :
LAN WAN
LOCAL AREA NETWORK (LAN) :
Definition: “ A network which is located entirely on one site such as an office, school or within a group of buildings that are in close proximity, that are connected together.”
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WIDE AREA NETWORK (WAN ) :
“ A network which connects together computers on a number of sites in different areas”.
A WAN or Wide Area Network is a group of widely dispersed computers that are connected
together. These could be across the same town, or across a country or even across the world”.
Apart from distance, the other feature that distinguishes as WAN from a LAN is that the WAN
would make use of a range of communication technologies such as telephone, microwave and
satellite links.
Using a WAN, schools in Florida can communicate with places like Tokyo in a matter of
minutes, without paying enormous phone bills. A WAN is complicated.
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Networks allow users to access their files from computers throughout the institute. Like Students can begin an assignment in their classroom, save part of it on a public access area of the network, then go to the media center after school to finish their work. Students can also work cooperatively through the network.
WORKGROUP COMPUTING.
Collaborative software allows many users to work on a document or project concurrently. For example, educators located at various schools within a county could simultaneously contribute their ideas about new curriculum standards to the same document, spreadsheets, or website.
NETWORK TOPOLOGY
Network topology refers to the layout used to wire the computers together.
TYPES OF TOPOLOGY
There are four main topologies that are used.
- BUS
- STAR
- RING
BUS TOPOLOGY
Each computer is connected to a single cable which connects all of the computers. All nodes (file server, workstations, and peripherals) are connected to the linear cable.
Advantages of Bus Topology
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Easy to connect a computer or peripheral to a linear bus. Requires less cable length than a star topology.
Disadvantages of a Bus Topology
Entire network shuts down if there is a break in the main cable. Terminators are required at both ends of the backbone cable. Difficult to identify the problem if the entire network shuts down. Not meant to be used as a stand-alone solution in a large building.
STAR TOPOLOGY
“All communication takes place via a central computer or HUB device.”
A star topology is designed with each node connected directly to a central network hub, switch, or concentrator.
Data on a star network passes through the hub, switch before continuing to its destination. The hub, switch, or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow.
Advantages of a Star Topology
- Easy to install and wire.
- No disruptions to the network then connecting or removing devices.
- Easy to detect faults and to remove parts.
Disadvantages of a Star Topology
- Requires more cable length than a linear topology.
- If the hub or concentrator fails, nodes attached are disabled.
- More expensive than bus topologies because of the cost of the HUB device.
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INTERNET
DEFINATION:
Internet is global “ Network of Networks ”. The internet is a worldwide public network of computers on which people can join and use multiple services such as sharing of information.
By internet users at any one computer can get information from any other computer.
HISTORY OF INTERNET
It was developed by the United States Defense Advanced Research Projects Agency in the 1970s and was initially known as ARPANET.
The Internet was designed to be used by companies and Universities doing military research so that they could share information. Since then the number of people who use the Internet and the services that are provided on the Internet have grown tremendously. There are now over 200,000,000 people who regularly make use of it.
CONNECTING METHODS TO THE INTERNET
To connect to the Internet the following are needed:
a computer
telephone line
modem and/or router
an ISP (Internet Service Provider)
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Web browser, e.g. Internet Explorer, Firefox, Chrome, Safari, Opera etc.
WHAT IS MODEM?
A device which convert analog signals to digital signals and digital signals to analog for transmitting data over internet.
WHAT IS WEB BROWSER?
Web Browser is Software used to display the Web pages. Internet explorer is an example of web browser
Here are some types of web browser:
Internet explorer Firefox Chrome Safari Opera
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WWW: World Wide Web, It consists of a large number of web servers that host websites. Each
website will normally consist of a number of web pages. A web page can contain text, images,
video, animation and sound.
Paknews: Domain Name
Com: type of web site there are many other types of web sites like
Pak: Pakistan
Edu: education
Mil: military
Gov: govt
Com: commercial
ADVANTAGES OF INTERNET
There many advantages to using the internet such as:
Email. Sharing Information. Services. Buy or sell products. Communities. News Searching jobs Advertisement Communication Entertainment Online education Online education and research
DISADVANTAGES OF INTERNET
Although there are huge advantages of internet but there is always another side of picture.
So internet has some disadvantages like
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Viruses Security problem Immorality Many information is not accurate Wastage of time
EMAIL
Electronic Mail (email) is a system which allows users of a computer network to send messages to each other. Users can usually:
Send a message to another user, or group of users. Keep their messages in a mailbox. Read, print and delete messages from their mailbox.
It is not only typewritten messages that can be sent using Electronic Mail. Pictures, music, videos, in fact almost any sort of information you can think of, can also be sent.
Each user has to have his or her own address that other users need to know to send messages to him or her.
Electronic mail is good because it is much faster that the ordinary post. It is also very accessible since you can read your email on any suitable computer anywhere in the world. On the other hand not everybody has an electronic mailbox at the moment, so you cannot use email to send messages to everyone, and you certainly can’t send a parcel by email.
There are many email service provider companies which allow any user to send and receive
electronic mail like
Hotmail o www.hotmail.com Yahoo o www.yahoo.com/mail Gmail o www.gmail.com
