1

“ WHAT IS INTERNET ”

2

What is Internet?

It is a global network of computers that communicate using a common language and allows the sharing of electronic information and resources. Internet is the world’s largest computer network, the network of networks, scattered all over the world.

What is Network?

A Computer network is an interconnection of two or more independent computer systems located at different places to share information and resources.

3

Keyword here is “Sharing” the main purpose of computer networking. The two computers are said be interconnected if they are able to exchange information. The connection need not be a via copper Wire, fiber optics, microwaves and communication satellite or any other wireless media can also be used.

Network contd…

Wireless Network

4

The internet is a world largest computer network "The Network of Networks" scattered all over the world. It consist of millions of private and public academics, business and government networks of local to global scope. The internet is a global system of interconnected computer networks cooperating with each other to exchange data. It is a group of two or more networks that are:

• connected physically• Capable of communication and sharing data with each other• Able to act together as a single network• Machines on one network can communicate with machines on other

network and send data files and other information back and forth.

Internet:

5

The original purpose of the Internet was to enable people in different locations to share text-only documents. Now there is much more you can do using the Internet. You can send and receive email messages; you can search the world for particular files or for files that contain particular words; you can have a live conversation using typed text or voice or even video; you can read electronic magazines and newspapers; you can check on the weather forecast or the score of a ball game; you can play computer games with several people at once; you can post messages to newsgroups on a common topic; you can buy books, CDs, software, electronic gadgets, or just about anything.

Internet offers wide variety of services and tools for communication and data exchange such as:

• Electronic Mail (e-mail)• Telnet (Remote login, A way of connecting directly to computer system)• File Transfer (FTP) A system for storing and retrieving data files• Usenet newsgroup (For posting a responding to a public bulletin board)• Internet Relay Chat (IRC)• Internet Telephone• The World Wide Web

The last component listed here is the most exciting and important element of the internet.

Internet Contd….

6

Web is a series of interconnected documents stored on a computer sites or web sites. These documents are connected each other through links called hyper links. These links are the highlighted words buttons icons or pictures. The world wide web gives a graphical and easy to navigate interface for looking at documents on the internet. These documents and links between them forms a "web" of information. This web lets you jump or hyperlink from one document or one web page to other pages on the web. One can think web as a big library. Websites are like the books and web pages are like the specific pages in the books. Pages can contain news, images, movies, sounds, 3D words – just about anything. These pages can be located on computers anywhere in the world. When you are connecting to he web you have equal access to information world wide.

World Wide Web or WWW :

The world wide web is a system of interlinked hypertext documents accessed via the internet.

The world wide web is a system of interlinked hypertext documents accessed via the internet.

7

Many people thinks Internet and WWW are the same thing. But actually the Internet is the network itself and many activities take place on it including WWW.

• The internet is a global data communication system. It has a hardware and software infrastructure that provides connectivity between computers.

• In contrast the web is one of the services communicated via the internet. It is a collection of interconnected documents and other resources linked by

hyperlink and URLs.

Internet and World Wide Web

Hyperlink & Hypertext:

A hyperlink refers to dynamic link upon clicking at which a new web page or programs opens.

Hypertext refer to the text that connects to other documents through hyperlinks. Hypertext is a method of instant cross referencing. It is used for organizing information and to link related documents or files residing on the same computer or even on net.

8

Network Protocol:For the Hassle-less communication between the computers in the internet each computer must follow some set of rules called protocols. These rules usually specify:

• how to computers can communicate with each other• how they can interprets each other messages • exact format and meaning of each message that a computer can send • under which conditions a computer should send a message and • how a computer should respond when the message arrives.

Thus a protocol is a set of rules which network device must follow to “communicate”. For this to work the network and the machines that are part of the network have to agree either to speak the same language when they are communicating or to use an interpreter.

The most common used protocols and services provided by the internet are as follows:

• Transmission Control Protocol/Internet protocol (TCP/IP)• File Transfer Protocol (FTP)• Hypertext Transfer Protocol (HTTP) • Telnet• Gopher• Simple Mail Transfer Protocol (SMTP)• Network News Transfer Protocol (NNTP)

9

TCP/IP Protocol:The basic protocol for the Internet is called TCP/IP (Transmission

Control Protocol/ Internet Protocol). It allows users computer to communicate properly over the internet.

TCP/IP is actually a collection of protocols or rules that governs the way data travels from one computer to another across the network. When you send or receive data (for example, an e-mail note or a Web page), the message gets divided into little chunks called packets. Each of these packets contains both the sender's Internet address and the receiver's address

IP component does the following:• Envelopes and address the data.• Enables the network to read the envelope and forward the data to its

destination. • define how much data can be fit in a single envelope.

TCP component does the following:• Breaks data up into the packets that the network can handle efficiently.• Verifies whether all the packets arrives at the destination • Re-assembles the data.

10

HTPP Protocol:Hypertext Transfer Protocol or HTTP is the set of rules or protocol that governs the transfer of hypertext between two or more computers. It is the primary access method for interacting with internet. The HTTP generally works in combination with WWW.

HTTP can be defined as a set of rules that signify how the web pages are transmitted over the Web. It is responsible for accessing hypertext documents on world wide web.

HTTP is based on the client server principle. HTTP allows "Computer A" (the client) to establish connection with "Computer B" (the server) and make a request. The server accepts the connection initiated by the client and send backs a response. An HTTP identifies the resource that the client is interested in and tells the server what action to take on the resource.

When user selects a hypertext link, the client program on their computer uses HTTP to contact the server, Identify a resource and ask the server to respond with an action. The server accepts the request and then uses HTTP to respond to or perform the action.

11

12

Web BrowserA WWW client is called the web browser and a WWW server is called a web server. The web browser navigates through the world wide web and displays pages. The web browser requests a page from a web server. The web server makes available the desired page to web browser. A browser short for web browser is a computer program that accesses web pages and display them on a computer screen. It is the basic software that is needed to find retrieve view and send information over the internet. In fact to access the WWW user requires a web browser. The most popular browsers are Microsoft Internet Explorer, Netscape Navigator, Mozilla’s Firefox, Google’s Chrome, Opera etc.

Web PageThe documents residing on the website are called web pages. The world wide web consist of files called pages or web pages which contains information and links to the resources throughout the internet. The web pages uses HTTP.

Web SiteA location on a net server is called a web site. A website is set of related web pages (linked through hypertext links) published by an organization or individuals. Normally a web site contains a home page along with other web pages. Each website is owned and updated by an individual, company or organization.

13

Home PageIt is the top level web page of a web site. When a website is opened, Its home page is displayed. Therefore home page refers to the main page for a web site. Most sites start with a file called index.html. From that starting point or "home page" you should have a general idea about what the site offers.

web pages/Home pages are an electronic document written in a computer language called HTML

Finding a Site on the NetEach page of a site on the Net has its own Uniform Resource Locator (URL) which tells where a file is located among all the computers that are part of the Internet . The URL is somewhat like an address of a specific web site. If you know the URL/address of the site you want to visit, you simply type it into the Address Bar at the top of the browser screen:

The Internet is platform independent. This means that it doesn't matter which operating system the server is using (e.g. Unix, Windows NT) because all servers share the common language of the Internet. Data may be transmitted via modem, cable or satellite with each of the servers working in collaboration with one another. The data seldom takes the same path to get from point A to point B; given the immensity of information transferred, the process is relatively error free

14

URLThe full form of URL is Uniform Resource Locator. A URL refers to an address on internet. Billions of documents/multimedia files can be accessed on internet through their URL.

Each web page has a unique address called URL that identifies its location on the internet. Web browser utilize the URL to retrieve a file from computer on which it resides.

URL defines three things: Method, Hostname and Path Name

The Method is the protocol used to retrieve the document. These protocols may be HTTP,FTP,NEWS,Telnet. The Host is the computer at which the information is located. Path is the pathname of the file where the information is located that separate directories from subdirectories and files.

Method

Host Path

15

http:// This web server uses Hypertext Transfer Protocol for communication the most common protocol on the internet

WWW This site is on the World Wide Web

rdunijbpin Registered Domain name associated with IP address of an web server. IP adress is a unique 32 bit number expressed as Four 8 bits octets and each octets separated by period. e.g. 127.57.13.1

org Domain type (This is a nonprofit Organization others are .com(Commercial) ,.edu (Education provider) .gov (Governmentagencies), .mil (Military sites), .net (network, Internet service provider),etc.

Path main/getinfo

File Name: about.htm

http://www.rdunijbpin.org/main/getinfo/about.htm

A Protocol Name

Host Computer Name

Domain Name

Domain type Path File Name

Format of URL(Uniform Resource Locator):

Server (Computer System That stores the information)

16

How the Page is displayed through browser:

The browser is a client program that is reading files/pages from a web server. Servers are special computers that contain web pages. the browser sends a request to the server for a specific web page. The Web Server receives a request and sends the requested page to the browser, which then interprets the HTML code and performs tasks based on the instructions contained in the code. This usually results in the display of a web page with text and graphics on your computer screen.

17

HTML Code:

Webpages that interprets by the Browsers are written in HTML - a simple scripting language called Hyper Text Markup Language (HTML). It is the language that runs the Web. HTML Provides a way of displaying web pages with Hyper text, text, image and multimedia contents. HTML is not a programming language but a markup language i.e. it uses markup tags to direct information from one page to another, to format text, display pictures, play music and many other actions. These markup tags tell the browsers how to display the page.

HTML markup tags generally used in pairs which tells the browsers to start and stop certain formatting commands. To distinguish from normal text These tags are written inside of the less than and greater than sign called angle brackets.

HTML code what it looks like in browser

This is the  <b>example of bold</b> This is the example of bold

 This is an <i>example of italic</i> This is an example of italic

This is an <h2>example of heading 2</h2> This is an example of heading 2 <center>example of center</center> example of center

This tag <U> underline</U> the text This tag underline the text

 example of <hr>