Internet Lesson

Lesson 1: What is the Internet?

      The Internet is the largest internet (with a small "i") in the world. An internet (with a small "i") is any set of networks interconnected with routers. It is a three level hierarchy composed ofbackbone networks, mid-level networks, and stub networks. These include commercial (.com or .co), university (.ac or .edu) and other research networks (.org, .net) and military (.mil) networks and span many different physical networks around the world with various protocols, chiefly the Internet Protocol.

      Until the advent of the World-Wide Web in 1990, the Internet was almost entirely unknown outside universities and corporate research departments and was accessed mostly via command line interfaces such as telnet and FTP. Since then it has grown to become an almost-ubiquitous aspect of modern information systems, becoming highly commercial and a widely accepted medium for all sort of customer relations such as advertising, brand building, and online sales and services. Its original spirit of cooperation and freedom have, to a great extent, survived this explosive transformation with the result that the vast majority of information available on the Internet is free of charge. While the web (primarily in the form of HTML and HTTP) is the best known aspect of the Internet, there are many other protocols in use, supporting applications such as electronic mail, Usenet, chat, remote login, and file transfer.

      There are several bodies associated with the running of the Internet, including the Internet Architecture Board, the Internet Assigned Numbers Authority, the Internet Engineering and Planning Group, Internet Engineering Steering Group, and the Internet Society.


Lesson 2: What is the World Wide Web?

The World Wide Web (WWW) is roughly defined as a collection of electronic documents loosely knit by a concept called "hypertext." Documents connect to each other by clickable "hyperlinks." It is more specifically an Internet client-server hypertext distributed information retrieval system, which originated from the CERN High-Energy Physics laboratories in Geneva, Switzerland. The World Wide Web Consortium (W3C) is the main standards body for the web.

On the WWW everything (documents, menus, indices) is represented to the user as a hypertext object in HTML format. Hypertext links refer to other documents by their URLs (Uniform Resource Locator). These can refer to local or remote resources accessible via FTP, Gopher, Telnet or news, as well as those available via the http protocol used to transfer hypertext documents. You need to run a browser program to access the Web.


Lesson 3: Modems, Browsers and ISPs

Modem

      Modem is actually the abbreviated form of modulator-demodulator, which is a device that translates computer (digital) signals to analog signals suitable for send across phone lines.

Browsers

      Browsers (also know as Web browsers) are software applications that are used to view Web pages, which include text, graphics, sound and video as shown below in the diagram.



Most browsers can also be used to send and receive email, connect to Web based free email services and read newsgroups.

      Web pages are written in the hypertext markup language, which is "read" and converted by the web browsers into pages like the one you are viewing now. Some of the web browsers available are: Microsoft Internet Explorer and the Netscape Navigator.

ISPs

      Internet Service Providers (or ISPs) are companies that provide access to the Internet. For a monthly fee, the internet service provider gives you a software package, username, password and access phone number. Equipped with a modem, you can then log on to the Internet and browse the World Wide Web and USENET, and send and receive e-mail. In addition to serving individuals, ISPs also serve large companies, providing a direct connection from the company's networks to the Internet. ISPs themselves are connected to one another through Network Access Points (NAPs). An Internet Service provider usually has multiple access methods, including dial-up, DSL, cable modem, ISDN, T1, and sometimes T3. ISPs are also called IAPs (Internet Access Providers).




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