<h1 align="center">Understanding the World Wide Web</h1>

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<p>The World Wide Web is a system of Internet servers that supports hypertext to access several Internet protocols on a single interface. The World Wide Web is often abbreviated as the Web or WWW. </p> <p>The World Wide Web was developed in 1989 by Tim Berners-Lee of the European Particle Physics Lab (CERN) in Switzerland. The initial purpose of the Web was to use networked hypertext to facilitate communication among its members, who were located in several countries. Word was soon spread beyond CERN, and a rapid growth in the number of both developers and users ensued. In addition to hypertext, the Web began to incorporate graphics, video, and sound. The use of the Web has reached global proportions and has become a defining aspect of human culture in an amazingly short period of time. </p> <p>Almost every protocol type available on the Internet is accessible on the Web. <strong>Internet protocols</strong> are sets of rules that allow for intermachine communication on the Internet. The following is a sample of major protocols accessible on the Web: </p> <dl> <dt><strong>E-mail</strong> (Simple Mail Transport Protocol or SMTP) </dt> <dd>Distributes electronic messages and files to one or more electronic mailboxes <p> </p></dd> <dt><strong>Telnet</strong> (Telnet Protocol) </dt> <dd>Facilitates login to a computer host to execute commands <p> </p></dd> <dt><strong>FTP</strong> (File Transfer Protocol) </dt> <dd>Transfers text or binary files between an FTP server and client <p> </p></dd> <dt><strong>Usenet</strong> (Network News Transfer Protocol or NNTP) </dt> <dt> </dt> <dd>Distributes Usenet news articles derived from topical discussions on newsgroups <p> </p></dd> <dt><strong>HTTP</strong> (HyperText Transfer Protocol) </dt> <dd>Transmits hyptertext over networks. This is the protocol of the Web. </dd> </dl> <p> </p> <p>Many other protocols are available on the Web. To name just one example, the Voice over Internet Protocol (VoIP) allows users to place a telephone call over the Web. </p> <p>The World Wide Web provides a single interface for accessing all these protocols. This creates a convenient and user-friendly environment. Once upon a time, it was necessary to be conversant in these protocols within separate, command-level environments. The Web gathers these protocols together into a single system. Because of this feature, and because of the Web's ability to work with multimedia and advanced programming languages, the Web is by far the most popular component of the Internet. </p>

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<h4 align="center">HYPERTEXT AND LINKS: THE MOTION OF THE WEB</h4>

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<p>The operation of the Web relies primarily on hypertext as its means of information retrieval. HyperText is a document containing words that connect to other documents. These words are called links and are selectable by the user. A single hypertext document can contain links to many documents. In the context of the Web, words or graphics may serve as links to other documents, images, video, and sound. Links may or may not follow a logical path, as each connection is created by the author of the source document. Overall, the Web contains a complex virtual web of connections among a vast number of documents, graphics, videos, and sounds. </p> <p>Producing hypertext for the Web is accomplished by creating documents with a language called HyperText Markup Language, or HTML. With HTML, tags are placed within the text to accomplish document formatting, visual features such as font size, italics and bold, and the creation of hypertext links. Graphics may also be incorporated into an HTML document. </p> <p>HTML is an evolving language, with new tags being added as each upgrade of the language is developed and released. For example, visual formatting features are now often separated from the HTML document and placed into Cascading Style Sheets (CSS). This has several advantages, including the fact that an external style sheet can centrally control the formatting of multiple documents. The World Wide Web Consortium (W3C), led by Web founder Tim Berners-Lee, coordinates the efforts of standardizing HTML. The W3C now calls the language XHTML and considers it to be an application of the XML language standard. </p>

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<h4 align="center">PAGES ON THE WEB</h4>

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<p>The World Wide Web consists of files, called pages or Web pages, containing information and links to resources throughout the Internet. </p> <p>Web pages can be created by user activity. For example, if you visit a Web search engine and enter keywords on the topic of your choice, a page will be created containing the results of your search. In fact, a growing amount of information found on the Web today is served from databases, creating temporary Web pages "on the fly" in response to user queries. </p> <p>Access to Web pages may be accomplished by: </p>

1. Entering an Internet address and retrieving a page directly
2. Browsing through pages and selecting links to move from one page to another
3. Searching through subject directories linked to organized collections of Web pages
4. Entering a search statement at a search engine to retrieve pages on the topic of your choice

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<h4 align="center">RETRIEVING DOCUMENTS ON THE WEB: THE URL and DOMAIN NAME SYSTEM</h4>

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<p>URL stands for Uniform Resource Locator. The URL specifies the Internet address of a file stored on a host computer connected to the Internet. Every file on the Internet, no matter what its access protocol, has a unique URL. Web browsers use the URL to retrieve the file from the host computer and the specific directory in which it resides. This file is downloaded to the user's client computer and displayed on the monitor connected to the machine. </p> <p>URLs are translated into numeric addresses using the <strong>Domain Name System (DNS)</strong>. The DNS is a worldwide system of servers that stores location pointers to Web sites. The numeric address, called the IP (Internet Protocol) address, is actually the "real" URL. Since numeric strings are difficult for humans to use, alphneumeric addresses are employed by end users. Once the translation is made by the DNS, the browser can contact the Web server and ask for a specific file located on its site. </p> <p><strong>Anatomy of a URL</strong> </p> <p>This is the format of the URL: </p> <blockquote> protocol://host/path/filename </blockquote> <p>For example, this is a URL on the Web site of the U.S. House of Representatives: </p> <blockquote> <strong>http://www.house.gov/house/2004_House_Calendar.html</strong> </blockquote> <p>This URL is typical of addresses hosted in domains in the United States.
Structure of this URL: </p>

1. Protocol: <strong>http</strong>
2. Host computer name: <strong>www</strong>
3. Second-level domain name: <strong>house</strong>
4. Top-level domain name: <strong>gov</strong>
5. Directory name: <strong>house</strong>
6. File name: <strong>2004_House_Calendar_html</strong>

<p> </p> <p>Note how much information about the content of the file is present in this well-constructed URL. </p> <p>Other examples: </p> <blockquote> <p><strong>telnet://locis.loc.gov</strong> the catalog of the Library of Congress </p> <p><strong>ftp://ftp.sunsite.auc.dk/projects/cgfa/picasso/p-picasso11.jpg</strong> a file on an ftp site </p> </blockquote> <p>Several top-level domains (TLDs) are common in the United States: </p> <div align="center"> <table cellspacing="0" cellpadding="6" width="50%" border="1" id="table1"> com commercial enterprise edu educational institution gov U.S. government entity mil U.S. military entity net network access provder org usually nonprofit organizations </table> </div> <p>New domain names were approved in November 2000 by the Internet Corporation for Assigned Names and Numbers (ICANN): .biz, .museum, .info, .pro (for professionals) .name (for individuals), .aero (for the aerospace industry), and .coop (for cooperatives). ICANN continues to investigate proposals for addding additional domain names, for example, .mobi for sites designed for mobile devices, and .jobs for the human resources community. </p> <p>In addition, dozens of domain names have been assigned to identify and locate files stored on host computers in countries around the world. These are referred to as <strong>two-letter Internet country codes,</strong> and have been standardized by the International Standards Organization as ISO 3166. For example: </p> <div align="center"> <table cellspacing="0" cellpadding="6" width="50%" border="1" id="table2"> ch Switzerland de Germany jp Japan uk United Kingdom </table> </div> <p> </p> <p>As the technology of the Web evolves, URLs have become more complex. This is especially the case when content is retrieved from databases and served onto Web pages. The resulting URLs can have a variety of elaborate structures, </p> <p>The first part of this URL looks familiar. What follows are search elements that query the database and determine the order of the results. As a growing number of databases serve content to the Web, these types of URLs will appear more commonly in your browser's address window. </p>

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<h4 align="center">HOW TO ACCESS THE WORLD WIDE WEB: WEB BROWSERS</h4>

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<p>To access the World Wide Web, you must use a Web browser. A browser is a software program that allows users to access and navigate the World Wide Web. There are two types of browsers: </p>

1. <strong>Graphical:</strong> Text, images, audio, and video are retrievable through a graphical software program such as Internet Explorer, Firefox and Netscape. These browsers are available for Windows, Apple, Linux and other operating systems. Navigation is accomplished by pointing and clicking with a mouse on highlighted words and graphics. <p> </p> You can install a graphical browser on your computer. For example, Internet Explorer is a part of the Windows operating system, and is also available on the Microsoft site: http://www.microsoft.com/ . Firefox is available for downloading from http://www.mozilla.org/products/firefox/ and Netscape is available from http://home.netscape.com/.
2. <strong>Text:</strong> Lynx is a browser that provides access to the Web in text-only mode. Navigation is accomplished by highlighting emphasized words in the screen with the arrow up and down keys, and then pressing the forward arrow (or Enter) key to follow the link. In these days of graphical browsers, it may be hard to believe that Lynx was once very popular. For more information, see http://library.albany.edu/internet/lynx.html

<p> </p> <h3>Extending the Browser: Plug-Ins</h3> <p>Software programs may be configured to a Web browser in order to enhance its capabilities. When the browser encounters a sound, image or video file, it hands off the data to other programs, called <strong>plug-ins,</strong> to run or display the file. Working in conjunction with plug-ins, browsers can offer a seamless multimedia experience. Many plug-ins are available for free. </p> <p>File formats requiring plug-ins are known as <strong>MIME types.</strong> MIME stands for Multimedia Internet Mail Extension, and was originally developed to help e-mail software handle a variety of binary (non-ASCII) file attachments. The use of MIME has expanded to the Web. For example, the basic MIME type handled by Web browsers is text/html associated with the file extention .html. </p> <p>A common plug-in utilized on the Web is the Adobe Acrobat Reader. The Acrobat Reader allows you to view documents created in Adobe's Portable Document Format (PDF). These documents are the MIME type "application/pdf" and are associated with the file extension .pdf. When the Acrobat Reader has been downloaded to your computer, the program will open and display the file requested when you click on a hyperlinked file name with the suffix .pdf. The latest versions of the Acrobat Reader allow for the viewing of documents within the browser window. </p> <p>Web browsers are often standardized with a small suite of plug-ins, especially for playing multimedia content. Additional plug-ins may be obtained at the browser's Web site, at special download sites on the Web, or from the Web sites of the companies that created the programs. </p> <p>Once a plug-in is configured to your browser, it will automatically launch when you choose to access a file type that it uses. </p> <h3>Beyond Plug-Ins: Active X</h3> <p><strong>ActiveX</strong> is a technology developed by Microsoft which make plug-ins less neccesary. ActiveX offers the opportunity to embed animated objects, data, and computer code on Web pages. A Web browser supporting ActiveX can render most items encountered on a Web page. As just one example, Active X allows you to view and edit PowerPoint presentations directly within your Web browser. ActiveX works best with Microsoft's Internet Explorer. </p>

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<h4 align="center">THE EXPERIENCE OF THE WEB</h4>

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<p>Today's World Wide Web presents an ever-diversified experience of multimedia, programming languages, and real-time communication. There is no question that it is a challenge to keep up with the rapid pace of developments. The following presents a brief description of some of the more important trends to watch. </p> <h3>Multimedia</h3> <p>The Web has become a broadcast medium. It is possible to listen to audio and video over the Web, both pre-recorded and live. For example, you can visit the sites of news organizations and view the same videos shown on the nightly news. Several plug-ins are available for viewing these videos. </p> <p>At one time, the entire multimedia file had to be downloaded before viewing. Since these types of files tend to be quite large, download times can be lengthy. This problem has been answered by a revolutionary development in multimedia capability: streaming media. In this case, audio or video files are played as they are downloading, or streaming, into your computer. Only a small wait, called buffering, is necessary before the file begins to play. </p> <p>The Windows Media Player, RealPlayer and QuickTime plug-ins play <strong> streaming audio and video</strong> files. Extensive files such as interviews, speeches and hearings work very well with these players. They are also ideal for the broadcast of real-time events. These may include live radio and television broadcasts, concerts, Web-only broadcasts, and so on. A list of selected sites that make use of these programs is available on the page, http://library.albany.edu/internet/reference/multimedia.html</p> <p><strong>Shockwave</strong> and <strong>Flash</strong> are plug-ins that provide another multimedia experience. They offer the creation and implementation of an entire multimedia display combining graphics, animation and sound. </p> <p>Sound files, including music, are also a part of the Web experience. Sound files may be incorporated into Web sites, and are also available for downloading independent of Web site visits. For example, try the search engine FindSounds.com. Sound files of many types are supported by the Web with the appropriate plug-ins. The MP3 file format, and the choice of supporting plug-ins, is one of the most popular music trends to sweep the Web. </p> <p><strong>Live cams</strong> are another aspect of the multimedia experience available on the Web. Live cams are video cameras that send their data in real time to a Web server. These cams may appear in all kinds of locations, both serious and whimsical: an office, on top of a building, a scenic locale, a special event, and so on. </p> <h3>Programming Languages and Functions</h3> <p>The use of existing and new programming languages have extended the capabilities of the Web. What follows is a basic guide to a group of the more common languages and functions in use on the Web today. </p> <p><strong>CGI, Active Server Pages: CGI (Common Gateway Interface)</strong> refers to a specification by which programs can communicate with a Web server. A CGI program, or script, is any program designed to accept and return data that conforms to the CGI specification. The program can be written in any programming language, including C, Perl, and Visual Basic Script. A common use for a CGI script is to process a form on a Web page. For example, you might fill out a form to order a book at Amazon. The script processes your information and sends it to Amazon to process your order. </p> <p>Another type of dynamically generated Web page is called <strong>Active Server Pages (ASP).</strong> Developed by Microsoft, ASP is a programming environment that processes scripts on the Web server. The scripts run on the server, rather than on the Web browser, to generate the HTML pages sent to browsers. Visual Basic and JScript (a subset of JavaScript) are often used for the scripting. ASPs end in the file extension .asp or .aspx. </p> <p><strong>Java/Java Applets: Java</strong> Java is an object-oriented programming language similar to C++. Developed by Sun Microsystems, the aim of Java is to create programs that will be platform independent. The Java motto is, "Write once, run anywhere." A perfect Java program should work equally well on a PC, Macintosh, Unix, and so on, without any additional programming. This goal has yet to be realized. Java can be used to write applications for both Web and non-Web use. </p> <p>Web-based Java applications are usually in the form of <strong>Java applets.</strong> These are small Java programs called from an HTML page that can be downloaded from a Web server and run on a Java-compatible Web browser. A few examples include live newsfeeds, moving images with sound, calculators, charts and spreadsheets, and interactive visual displays. Java applets can tend to load slowly, but programming improvements should lead to a shortened loading time. </p> <p><strong>JavaScript/JScript: JavaScript</strong> is a programming language created by Netscape Communications. Small programs written in this language are embedded within an HTML page, or called externally from the page, to enhance the page's the functionality. Examples of JavaScript include moving tickers, drop-down menus, real-time calendars and clocks, and mouse-over interactions. <strong>JScript</strong> is a similar language developed by Microsoft and works with the company's Internet Explorer browser. </p> <p><strong>VRML: VRML</strong> (Virtual Reality Modeling Language) allows for the creation of three-dimensional worlds. These may be linked from Web pages and displayed with a VRML viewer. One of the most interesting aspects of VRML is the option to "enter" the world and control your movements within the world. </p> <p><strong>XML: XML</strong> (eXtensible Markup Language) is a mark-up language that enables Web designers to create their own customized tags to provide functionality not available with HTML alone. XML is a language of data structure and exchange, and allows developers to separate form from content. With XML, the same content can be formatted for multiple applications. In May 1999, the W3 Consortium announced that HTML 4.0 has been recast as an XML application called XHTML. This move is slowing having an impact on the future of both XML and HTML. </p> <h3>Real-Time Communication</h3> <p>Text, audio and video communication can occur in real time on the Web. This capability allows people to conference and collaborate in real time. In general, the faster the Internet connection, the more successful the experience. </p> <p>At its simplest, <strong>chat</strong> programs allow multiple users to type to each other in real time. Internet Relay Chat and America Online's Instant Messenger are prime examples of this type of program. The development of a messenging protocols is underway. Such a protocol would allow for the expansion of this capability throughout the Internet. </p> <p>More enhanced real-time communication offers an audio and/or video component. CU-See Me is a sotware programs of this type. Even more elaborate are programs that allow for true <strong>real-time collaboration.</strong> Microsoft's NetMeeting and Netscape's Conference (available with Communicator) are good examples of this. </p> <p>Featured collaboration tools include: </p> <ul>

<strong>audio:</strong> conduct a telephone conversation on the Web

<strong>video:</strong> view your audience

<strong>file transfer:</strong> send files back and forth among participants

<strong>chat:</strong> type in real time

<strong>whiteboard:</strong> draw, mark up, and save images on a shared window or board

<strong>document/application sharing:</strong> view and use a program on another's desktop machine

<strong>collaborative Web browsing:</strong> visit Web pages together

</ul> <p>Currently no standard exists that will work among all conferencing programs. </p> <p><strong>Push: Push</strong> refers to a technology that sends data to a program without the program's request. This is the opposite of the typical "pull" of the Web, in which the user clicks on a link to request a file from a server. With push, the data is sent automatically. Content is sent through a "channel." The early Web-based implementation of push was commercial. Push can also be used to deliver software upgrades to desktop machines. At one time, push was considered to be The Next Big Thing for the Web. This has not materialized. </p> <div id="globalWrapper"> <div id="column-content"> <div id="content"> <div id="bodyContent"> <b>History of the Internet</b><p>The underlying ideas of the Web can be traced as far back as 1980, when Tim Berners-Lee and Robert Cailliau built ENQUIRE (referring to Enquire Within Upon Everything, a book Berners-Lee recalled from his youth). While it was rather different from the Web we use today, it contained many of the same core ideas (and even some of the ideas of Berners-Lee's next project after the WWW, the Semantic Web).</p> <p>In March 1989, Tim Berners-Lee wrote "Information Management: A Proposal", which referenced ENQUIRE and described a more elaborate information management system. [3] He published a more formal proposal for the actual World Wide Web on November 12, 1990 [4]. Implementation began on November13, 1990 when Berners-Lee wrote the first Web page on a NeXT workstation.</p> <p>During the Christmas holiday of that year, Berners-Lee built all the tools necessary for a working Web [5]: the first Web browser (which was a Web editor as well) and the first Web server.</p> <p>On August 6, 1991, he posted a short summary of the World Wide Web project on the <tt> alt.hypertext</tt> newsgroup. This date also marked the debut of the Web as a publicly available service on the Internet.</p> <p>The crucial underlying concept of hypertext originated with older projects from the 1960s, such as Ted Nelson's Project Xanadu and Douglas Engelbart's oN-Line System (NLS). Both Nelson and Engelbart were in turn inspired by Vannevar Bush's microfilm-based "memex," which was described in the 1945 essay "As We May Think".</p> <p>Berners-Lee's brilliant breakthrough was to marry hypertext to the Internet. In his book Weaving The Web, he explains that he had repeatedly suggested that a marriage between the two technologies was possible to members of both technical communities, but when no one took up his invitation, he finally tackled the project himself. In the process, he developed a system of globally unique identifiers for resources on the Web and elsewhere: the Uniform Resource Identifier.</p> <p>The World Wide Web had a number of differences from other hypertext systems that were then available.</p> <ul>

The WWW required only unidirectional links rather than bidirectional ones. This made it possible for someone to link to another resource without action by the owner of that resource. It also significantly reduced the difficulty of implementing Web servers and browsers (in comparison to earlier systems), but in turn presented the chronic problem of broken links.

</ul> <ul>

Unlike certain applications, such as HyperCard, the World Wide Web was non-proprietary, making it possible to develop servers and clients independently and to add extensions without licensing restrictions.

</ul> <p>On April 30, 1993, CERN announced that the World Wide Web would be free to anyone, with no fees due.</p> <p>The World Wide Web finally gained critical mass with the 1993 release of the graphical Mosaic web browser by the National Center for Supercomputing Applications developed by Marc Andreessen. Prior to the release of Mosaic, the Web was text based and its popularity was less than older protocols in use over the Internet, such as Gopher and WAIS. Mosaics graphical user interface allowed the Web to become by far the most popular Internet protocol.</p></div> </div> </div> </div>