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About the Internet
# What is Internet?
Internet is a global collection of computer's, which are linked together by cable and telephone lines making communication possible among them in a common language. It can be defined as a global network over a million of similar heterogeneous computer networks. The internet is the common language whereby dissimilar computers with various operating systems, are able to communicate with each other, using a standard set of protocols (rules).
A user need the following to access the Internet:
An internet access account from an ISP(Internet service provider) Computer
Necessary software for connecting to the internet and accessing information.
#Internet Addressing-Domain name system
An addressing system was designed by the INTERNET ENGINEERING TASK FORCE (IETF).This addressing scheme assigns name and numbers to identify the computer on the internet. The names are called domain names and the numbers are called IP addresses. Every computer system on the Internet has a domain name and IP address.
#COMMANLY USED NON- GEOGRAPHICAL DOMAINS
DOMAIN NAME DESCRIPTION
.COM A company or commercial organization. for example- netscape.com
.EDU Educational institution (i.e,universities,schools etc).for example- ignou.edu
.GOV Government organization. for example- whitehouse.gov
.MIL Military site. For example- army. mil
.NET Network resources or internet service provider. for example- internic.net
.ORG Other organization, manily non-profit or non-commercial organizations. for example- rfc.editor.org
# What is world wide web(www)?
The World Wide Web (www) is an internet service, based on a common set of protocols, which allows a particularly configured server computer to distribute documents across the internet in a standard way. The www is an example of client-server technology.
# What are protocols?
A protocol, in general, is set of procedural rules that must be obeyed to effect orderly exchange of intelligence among communicating agencies. It helps in a proper exchange and sharing of information and working procedures.
#HYPER TEXT TRANSPORT PROTOCOL (HTTP)
A web page is created by using a specialized language called- HYPER TEXT MARKUP LANGUAGE
(HTML).web pages are requested by internet users or clients from the internet hosts or server and are served or transported over the internet using a protocol called HYPER TEXT TRANSPORT PROTOCOLS (HTTP).
FTP-File Transfer Protocol
SMTP:-Simple mail Transfer Protocol
# Web site
A web site is a collection of web pages belonging to a particular person or organization. Each document on the web site, which may contain only text or a text, image and multimedia, is called a web page.
The most popular browser, are:
Microsoft internet explorer
Netcom’s web cruiser
# Electronic mail (E-mail)
E-Mail is a popular way of communication on the internet. By which you can send mail to any part of the world with in few seconds and without spending huge amount of money. It is the method of sending or receiving messages electronically.
# What is networking?
A network is an interconnected collection of autonomous computers. Two computers are said to be interconnected if they are capable of exchange information. Autonomous mean that no computer on the network can start, stop or control another. So, a network allows computer users to share computer equipment and programs, messages and the information available at one site.
Advantages and Disadvantages of networking:-
1. Resource Sharing
2. High reliability
3. Saving Money
4. Communication media
1. Increased Security Risk.
2. Increased Hardware /Software Risk.
#Types of Network
There are three type of networking
LAN(local area networks)
WAN(wide area networks)
MAN(metropolitan area networks)
A digital communication system capable of interconnecting a large number of computers, terminals and together peripheral devices confined to relatively small areas such as a building or a group, for example university campus.
#TOPOLOGIES OF LAN
There are three types of LAN
The bus topology permits the connection of terminals, peripheral devices and micro computers along a central cable called a transmission medium. It is easy to add devise or delete them from the network .It is also know as ETHERNET CABEL .Addition of node can often be accomplished without disrupting network traffic .Data to be transmitted from one node is sent on the bus from where it is captured by the target node .
# STAR LAN
A star topology involves a centralized host computer connected to a number of smaller computer systems. The smaller computer systems communicate with one another through the host and usually share the host computer database. Both the central computer and the distributed computer system are connected to terminals.
The ring topology involves computer systems that are a appropriately the same size, with no one computer system as the focal point of network. When one system routes a message to another system, it is passed around the ring until it reaches its destination address. The ring requires no routing as each nodes always passes on a message.
It is a larger version of LAN which again utilizes the concept of cable to transmit any thing. There is special property in MAN we can transmit data and voices. In MAN switching element (IMPs) is not present .Which simplified the design complexity.
A Wide Area Network covers a large geographical area in WAN post & system machine are connected with the help of communication subnet. Subnet is the collection of transmission lines and switching element (rooter/IMP).Internetwork is separate type of WAN .Various network of different type are connected together to share and exchange informations of any kind In this way we can say that a WAN which connects various LAN may be a better example of internetwork.
HTML (Hyper Text Markup Language)
The language used to develop web pages is called Hyper Text Markup Language (HTML).
HTML is the language Interpreted by a browser. WebPages are also called HTML documents.HTML is a set of special codes that can be embedded in text to add, formatting and linking information .HTML is specified as TAGS in an html document.
Tags are instructions that are embedded directly into the text of the document .An html tag is a signal to a browser that it should do something other than just throw text up on the screen .By convention all html tags begin with an open angle(<) bracket and end with a close(>) angle bracket.
HTML tags can be of two types
1) PAIRED TAGS: - A tag is said to be a paired tag if it is along with a companion tag.
For example the <B> tag is Paired tag. The <B> tag with its companion tag </B> causes the
Text contained between them to be rendered in bold. Ex- <html>, <body>, <center>, <p>
2) SINGULAR TAGS:-The second type of tag is the singular or stand alone tag. A stand alone tag does not have a companion tag. For example <BR> tag will insert a line break. This tag does not require any companion tag. Ex.-<HR> , <BR>