The Internet was created for the U.S. Department of Defense as a tool for communications. Today, the Internet is a network of interconnected networks. It is a huge, cooperative community with no central ownership. The Internet connects thousands of networks and more than 100 million users around the world. The Internet carries messages, documents, programs, and data files that contain every imaginable kind of information for businesses, educational institutions, government agencies, and individuals.
All computers on the Internet use TCP/IP protocols. Any computer on the Internet can connect to any other computer. Individual computers connect to local and regional networks, which are connected together through the Internet backbone. A computer can connect directly to the Internet, or as a remote terminal on another computer, or through a gateway from a network that does not use TCP/IP. Every computer on the Internet has a unique four-part numeric IP address, and most also have an address that uses the domain name system (DNS). DNS addresses have two parts: a host name (a name for a computer connected to the Internet) followed by a domain that generally identifies the type of institution that uses the address. This type of domain is often called top-level domain. For example, many companies have a DNS address whose first part is the company name followed by ".com" - ibm.com (International Business Machines Corp.). Some large institutions and corporations divide their domain addresses into smaller subdomains. For example, a business with many branches might have a subdomain for each office - such as boston.widgets.com and newyork.widgets.com. In 1996 a new set of top-level domain names was created because it was difficult for organizations to find suitable domain names for their Internet sites, for example .firm (businesses or firms), .shop (business that offer items for purchase over the Internet),.arts (organizations promoting artistic or entertainment activities over the Internet. Geographic domains usually identify the country in which the system is located, such as .ca for Canada or .fr for France.
The Internet has a lot of uses:
- Inexpensive electronic mail systems enable you to exchange messages with any other user anywhere.
- TELNET allows a user to operate a second computer from his or her machine.
- File Transfer Protocol (FTP) is the Internet tool for copying data and program files from one computer to another.
- News and mailing lists are public conferences distributed through the Internet and other electronic networks.
- Chats are public conferences, conducted in real time, where people discuss topics of interest.
The World Wide Web
One part of the Internet is the World Wide Web. It was created in 1989 at the European Particle Physics Laboratory in Geneva, Switzerland as a method for incorporating footnotes, figures, and cross-references into online hypertext documents. A hypertextdocument, or a Web page, is a specially encoded file that uses the hypertext markup language (HTML). This language allows a document's author to embed hypertext links, or hyperlinks, in the document. A collection of related Web pages is called a Web site. Web sites are housed on Web servers, Internet host computers that often store thousands of individual pages. Copying a page onto a server is called posting the page. Downloading a page from the Web server to your computer for viewing is commonly called "hitting" the Web site. Many Web pages feature a hit counter to display the number of times the page has been viewed.
A Web browser is a software application designed to find hypertext documents on the Web and then open the documents on the user's computer. A point-and-click browser provides a graphical user interface (GUI) that enables the user to click graphical objects and hyperlinks. The most popular browsers are Microsoft's Internet Explorer and Netscape Navigator. A Web browser displays a Web page as specified by the page's underlying HTML code. To format a document in HTML, a designer places HTML tags throughout the document. The HTML tags enclosed in angle brackets (<>), tell the browser how to display individual elements on the page. The internal structure of the World Wide Web is built on a set of rules called Hypertext transfer protocol (HTTP). HTTP uses Internet addresses in a special format, called a Uniform Resource Locator (URL). URLs look like this: type://address/path/. In a URL, type specifies the type of the server in which the file is located, address is the address of the server, and path is the location within the file structure of the server. The path includes the list of folders (or directories) where the desired file is located.
You probably have heard the term home page used to reference a page named index.htm on a Web site. This term is important and actually has two meanings:
Personalized Start Page. On your computer, you can choose a Web page that opens immediately when you launch your Web browser by using a command in your browser to specify the URL for the desired page. This personalized start page can be on your computer's hard drive or a page from any Web site. For example, if you want to see today's copy of USA Today Online when you launch your browser, use the address http://www.usatoday.com/ as your personal home page.
Web Site Home Page. A Web site's primary page is also called its home page. This page is the first one you see when you type the site's basic URL. From this page, you can navigate to other pages on the Web site (and possibly to other sites). For example, if you type the URL http://www.cnn.com/ into your browser's address box, the CNN home page opens in your browser window.