Basic Concepts of the World Wide Web

The World Wide Web ("affectionately" called "the Web") is a collection of information stored on computers that are connected to the Internet all over the world. The information can be any type such as text, graphics, audio, and video. The difference between the Web and other types of Internet features is that the Web uses an approach to link material together known as "hyperlinks." When these links are text-based, they are called "hypertext."

To know how the Web works, the following concepts are helpful:

• HTML
• URL
• Web browser
• Web Server
• Client/Server Protocol
• HTML Editor

HTML

HTML (HyperText Markup Language) is a language for creating web pages. Though it is not absolutely neccessary to know HTML before you start to create your own web page thanks to some WYSIWYG("What You See Is What You Get") HTML editors, it is still very helpful and some time a must to know some basics about HTML. Actually, WYSIWYG HTML editors will automatically generate the HTML codes for us. But the bad news is that some HTML codes generated by some WYSIWYG editors are not wholly compatible on different web browsers. To add some advanced features, some WYSIWYG HTML editors are proved quite awkward. That's why most professional web designers still prefer text editors.

In fact, HTML is a very simple tag language, which most people can easily pick it up in less than an hour. At least, homepage construction is not as difficult as you image at the beginning. When I first saw an impressive homepage in 1995, I could not help respecting the authors for their great works. But now I realize that it is really a easy task to construct a basic but attractive homepage. Of course there are many advanced techonologies such as CGI technology (such as PERL scripting, Server Side Include), Active Server Page, Java Servlets, Java Server page, JavaScripts, VBScripts, Java Applet etc. which still require some computer science background. But it's possible to create a very nice homepage without resorting to these advanced features. Of course, laterly if you're interested, you can move on to those higher-level stuffs step by step.

If you know nothing about HTML, you can reference A Beginner's Guide to HTML , a classic and simple tutorial which comes from the home of the first graphic web browser(Mosaic) - NCSA. Personally, I love NCSA's web site, since there are an excellent source of information for both beginning and experienced Web developers.

URL

URL (Uniform Resource Locator) is a naming system that compactly describes the location of every resource on the Internet and the protocol to retrieve it.

For example "http://www.zhanshou.com/myDir/myPage.html" is an URL. It includes three parts:

• Transfer Protocol or Scheme - here "http" which stands for HyperText Transfer Protocol
• Domain Name (Server Name) , as "www.zhanshou.com", which is the alias name for an IP address
• File path name , here is "/myDir/myPage.html"

Please note that usually the Domain Name is NOT case sensitive but the File Path name IS, especially in UNIX-based server systems. This is one of the common problems may confuse some beginners.

Web Browser (Web Client)

A web browser is a program which combines a variety of information retrieval abilities under one interface, make it easier to retrieve and use resourses. Microsoft Internet Explorer, Netscape, and Mosaic are the three most widely used web browsers. It is most likely that you are using one of these three browsers to read this tutorial.

The first graphical web browser was Mosaic, developed by Marc Andreeson (once the vice president of Netscape Inc.) when he was an undergraduate in NCSA. It was the birth of graphic web browser that brought revolutions to the internet and information industry. Other graphic browsers include:

• Hotjava developed by Sun Microsystem in Java language. It has some good features but still has many "bugs". (You can download a free copy from Java 's homepage).
• Cello is another graphical browser, developed by Thomas R. Bruce at Cornell Law School.
• If you use a text-based terminal on a large system, you can use "lynx" to read webpages in a "text only" mode.

Web Server

A Web server is a program that runs on a computer connected to the Internet. The Web server watches the Internet connection and waits for requests from the Web browser.When it receives a requests, if this is static HTML document, it finds the document and sends it back to the browser that requested it; for dynamic page, some server side scripts (programs) will run first and generate the information then return back to the requested clients.

A Web server provides four major functions:

• Serving Web pages
• Running gateway programs and returning output
• Controlling access to the server
• Monitoring and logging server access statistics

There are lots of different web servers that are available on almost every kind of existing platforms. Here are some of the most popular so far:

• Apache Web Server - originally developed on UNIX platform but right now available on Window, LINUX and other platforms. It's an open source and free-distributed software, available from Apache Software Foundation. It dominates the web server market and has more than half of the total market shares upto mid 2001.
• Microsft Internet Infromation Server(IIS) - comes with Microsoft Window Server, only running on Window platform
• Netscape Enterprise Web server - from Netscape.

Client/Server Protocols

The Web is build on a client/server model basing on a request/response paradigm. A server is like the proprietor of a general store; it waits for a client to come in with a request. A client is like a customer who walks into the store and asks for one or more items in a grocery.

Clients and servers communicate with each other using a common protocol. A protocol is a collection of rules that must be complied with by both sides when they communicate with each other. The HyperText Transfer Protocol (HTTP) is the protocol used by The Web.

HTML Editors