More About WWW


Getting Started

Congratulations! If you are a new internet user reading this page, you should congratulate yourself. You have taken the first step in becoming a proficent user of the internet. Before going through further information, let me explain a bit about what is going on.

Right now you are viewing a system known as World Wide Web or WWW which is a useful system for getting information about the internet. The first stage of this class is to get you comfortable about using WWW so that you can access lots of interesting things on the internet.

WWW is an example of hypertext. Hypertext is like regular text with one important difference. It is possible to "link" a piece of text (such as this essay) with another piece of text on the net. To show exactly how this works, This piece of text should appear somewhat different from the rest of the text in this essay. If you are using a graphical browser, it may be underlined and/or with different color from the main text.

This difference in the text means that that piece of text is connected to another file on the net. To view that other file, you have to select the link. If you are using a graphical browser, you generally select a link by moving the mouse pointer over the link and clicking the mouse button.

O.K. do that, and see where the text leads to.


How the Web Works

Getting a World Wide Web page such as this to you requires the cooperation of two programs. One program which is located on your local machine is called a client. The other program is located on a remote machine on which some WWW pages are stored and is called a server.

Whenever you want to view a page, the client sends a message to the server asking to retrieve a page. The server gets this message, finds the requested page, and sends it back to the client. The client gets this page and then displays it. These two programs "talk" to each other using a common language called HyperText Transfer Protocol or HTTP.

This division of work between a client program that asks for and displays the pages and the server program which finds the pages has several big advantages. One of these advantages is that you can use different client programs for different machines. The server doesn't care whether you are running a Mac, a PC, or an X terminal. It doesn't care if you are restricted to text only or have the latest graphics displays. The only job of the server is to send a page to the client. It's up to the client to figure out how to display the page and how to figure out what pages the user wants from the server.

There are a lot of different clients out there. This is good because it means that a lot of different types of computers can connect themselves to the web. Unfortunately, the fact that there are a lot of different clients makes it hard to teach how to use the web, because many of the different clients have different ways of doing things. We have already run into this problem once before. In most graphical clients, you select a link by clicking on it with a mouse. On the other hand, text-only browsers are designed for machines without mice, and in these links are selected by choosing a number.

Another problem in having many different clients is that some clients have special features which are not universal. For example, certain clients let you put bookmarks on pages so that you can return to them and let you add personal notes to a WWW page. Others don't.


Document Addresses

Each document on WWW has a particular address, which is called a Universal Resource Locator or URL for short. As an example of a typical URL, we have this document which whose URL is

http://www.mansfield.ohio-state.edu/summer95/wwwintro.html

To understand what this means, we can break up the address into its component parts.

http: ----
The first part of the URL is the protocol used to retrieve the document. In other words, the first part of the URL describes the language that the server and client will use to communicate with each other. In the case of this document, the language use to communicate between the server and the client is http or hypertext transfer protocol. Other common protocols includes gopher, ftp, telnet, etc. .

www.mansfield.ohio-state.edu ----
This section refers to the machine on which the document is stored, location of the server.

summer95/wwwintro.html ----
This section of the address gives the path and the name of the document. In this case, the document is intro.html contained in the directory (ie. folder) summer95. The file name of a hypertext document usually has the .html extention, meaning hypertext markup language.


Let's Start the Fun!

Before taking off, let me remind you to use "Back" button, "Forward" button, or "Go" menu to move back and forth.

Here is a list of some starting points to surf the Web.

June 8, 1995
Chunsheng Ban / cban@math.ohio-state.edu