A bit of reading practice The World Wide Web

The World Wide Web is a system of Internet servers that supports hypertext to access several Internet protocols on a sin­gle interface.

Almost every protocol type available on the Internet is ac­cessible on the Web. Internet protocols are sets of rules that allow for intermachine communication on the Internet. The following major protocols are accessible on the Web:

E-mail (Simple Mail Transport Protocol or SMTP) Distributes electronic messages and files to one or more electronic mailboxes.

Telnet (Telnet Protocol) Facilitates login to a computer host to execute commands.

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FTP (File Transfer Protocol) Transfers text or binary files be­tween an FTP server and client.

Usenet (Network News Transfer Protocol or NNTP)

Distributes Usenet news articles derived from topical discus­sions on newsgroups.

HTTP (HyperText Transfer Protocol) transmits hyptertext over networks.

Other protocols are also available on the Web e.g., the Voice over Internet Protocol (VoIP) allows users to place a telephone call over the Web. The World Wide Web provides a single interface for accessing all these protocols.

This creates a convenient and user-friendly environment. It is not necessary to be conversant in these protocols within separate, command-level environments. The Web gathers these protocols into a system and is the fastest-growing component of the Internet (taking into account its ability to work with multimedia and ad­vanced programming languages).

Hypertext 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. Hence, the WWW contains a complex virtual web of connections among a huge amount of documents, graphics, videos, and sounds.

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. HTML is an evolv­ing language, with new tags being added as each upgrade of the language is developed and released.

Pages on the Web» The World Wide Web consists of files, called pages or Web pages, containing information and links to re­sources throughout the Internet.

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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.

Access to Web pages may be accomplished by:

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.

The URL, retrieving documents on the Web. 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 software programs use the URL to retrieve the file from the host computer and the directory in which it resides. This file is then displayed on the user's Monitor.

URLs are translated into numeric addresses using the Inter­net Domain Name System (DNS). The numeric address is actually the «real» URL. The URLstructure.

This is the format of the URL:

protocol: //host/path/filename

For example, this is a URL on the home page of the House Committee on Agriculture of the U.S. House of Representatives:

http://www.house.gov/agriculture/schedule.htm

This URL is typical of addresses hosted in domains in the United States. Structure of this URL:

1. Protocol: http

2. Host computer name: www

3. Second-level domain name: house

4. Top-level domain name: gov

5. Directory name: agrictulture

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6. File name: schedule.htm

Web browsers. 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:

1. Graphical: Text, images, audio, and video are retrievable through a graphical software program such as Netscape Na­vigator and Internet Explorer. Navigation is accomplished by pointing and clicking with a mouse on highlighted words and graphics.

2. Text: 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.

Plug-ins extend the browser. 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 plug-ins, to run or display the file. Working with plug-ins, browsers can offer a seam­less multimedia experience.

File formats requiring plug-ins are known as MIME types (Multimedia Internet Mail Extension). The basic MIME type han­dled by Web browsers is text / html associated with the file exten-sion.html.

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 Fortnat (PDF). These doc­uments are the MIME type application / pdf and are associated with the file extension .pdf. When the Acrobat Reader has been configured to your browser, the program will open and display the file requested when you click on a hyperlinked file name with the suffix.pdf.

Web browsers are often standardized with a small suite of plug-ins, especially for playing multimedia content Once a plug-

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in is configured to your browser, it will automatically launch when you choose to access a file type that it uses.

ActiveX is a technology developed by Microsoft which may make plug-ins less necessary. 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. For example, Active X allows users to view three-dimensional VRML worlds in a Web browser without the use of a VRML plug-in. As another example of the power of Acti­veX, this technology can allow you to view and edit PowerPoint presentations directly within your Web browser. ActiveX works best with Microsoft's Internet Explorer browser.

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.

Multimedia

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 various news organizations and view the same videos shown on the nightly television news. Several plug-ins are available for viewing these videos. For exam­ple, Apple's Quick Time Player downloads files with the .mov ex­tension and displays these as «movies» in a small window on your computer screen. Quick Time files can be quite large, and it may take patience to wait for the entire movie to download into your computer before you can view it.

The problem of slow download times 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. The RealPlayer plug-in plays streaming audio and video files. Extensive files such as interviews, speeches and hearings work

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very well with the RealPlayer. The RealPlayer is also ideal for the broadcast of real-time events. These may include press confe­rences, live radio and television broadcasts, concerts, etc. The Windows Media Player is another streaming media player.

Shockwavepresents another multimedia experience. Shock­wave allows for the creation and implementation of an entire multi­media display combining graphics, animation and sound.

Sound files, including music, may also be heard on the Web. It is not uncommon to visit a Web page and hear background music. Sound files are also available for downloading independent of Web page visits. 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 the latest music trend to sweep the Web. The fam­ous Napster site allows for the exchange of MP3 files.

Live camsare 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.

Date: 2015-12-11; view: 1002