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
HTML (HyperText Markup Language) is a language for marking hypertext links
and other important features of a document. If you want to construct your
own web page, mastering HTML is the first step. Don't worry, homepage construction
is not as difficult as you may think. When I first saw an impressive homepage
two years ago, I could not help respect the authors for their work. But
now I realize that it is really a relatively easy task to construct a basic
but attractive homepage. Of course there are many advanced features such
as Javascript, VBScript, Java Applet, ActiveX control and CGI technology
(such as PERL scripting, Server Side Include) which still require a lot
of knowledge and work. But it's possible to create a very nice homepage
without resorting to these advanced features. Then, later, if you're interested,
you can move on to learn some of the higher-level capabilities which are
available.
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 original web browser Mosaic - NCSA. Personally, I
love NCSA's web site, since they 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.cs.uh.edu/~zsyu/me.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.cs.uh.edu", which is the alias name
for "rodin.cs.uh.edu", the web server at the Department of Computer Science
of UH.
-
File path name , here is "/~zsyu/me.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 problem may confuse some start users.
For more information about URL,visit NCSA again at A
Beginner's Guide to URLs .
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.
Netscape, Microsoft
Internet Explorer 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
(now vice president of Netscape Inc.) when he was an undergraduate in NCSA.
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 for HTML an document. When it receives a requests, it finds
the HTML document and sends it back to the browser that requested it.
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
NCSA httpd server, Netscape server and CERN server are currently the three
most commonly used servers.
Client/Server System and 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
You can use any text editor, such as Notepad , Wordpad or vi, to create
and edit your HTML files. Some "What You See Is What You Get" (WYSIWYG)
editors are available (e.g., Microsoft Frontpage, Internet Assistant ,Netscape
Page Composer, HotMetal, HotDog, Adobe PageMill,etc). Some of them are
free. For example, the Netscape Page Composer is one part of the latest
Netscape Communicator package. It is a good tool to create your web pages.
Of course, you can select online
listing of HTML editors (organized by platform) by yourself.

