How the Web Works - A Brief Introduction

Although we are ignoring a lot of details, you can picture the World Wide Web as working this way:

           
|  user   |
|         |
    |                                   
|             |         /              /
| workstation |<------>/ Internet or  /
|             |       /  Intranet    /
                     /              /  
                             |
                             |          
                       |            |
                       | Web Server |
                       |            |
                              |        
                              |       
                       |             |
                       | Data server |
                       |             |

• Now, the user (you, or a colleague or a customer) are at your workstation, which is probably running Windows, maybe Mac, OS/2, or Linux

• To get to the web, you get into your browser applicaiton, which is probably Microsoft Internet Explorer, Netscape Navigator, Apache, or some other browser

• You and the browser are considered the client

• The "Web Server" has traditionally been a UNIX box; more recently it could be Windows box; now it can be a mainframe

• The "Data server" has often been a mainframe running DB2 or a UNIX box with DB2 for UNIX or  Oracle, Informix, or Sybase

• With UNIX System Services available on the mainframe, the two separate systems, the Web server and the Data server, can now be consolidated to one box: the mainframe which runs your mission critical classic applications and at the same time it can run your new mission critical Web applications

• Few people are aware of the fact that IBM ships a free Web Server along with OS/390 and z/OS, but it's there

• A web page is just a text file stored on the Web server. This text is in a language called HTML (or possibly the newer XHTML). That is, the words are stored along with formatting information, to tell the browser that something should be underlined, or bulleted, and so on
  
• We say the browser renders the page

• When you ask your browser to look at a web page (http://www...), the browser goes to the Web server, who finds the page and sends it back to the browser

• The browser converts the text of HTML text into a visible web page on your workstation

• If a web page has graphics or animations or music, these are all stored in separate files, and the HTML / XHTML just points to those files; they are sent along with the page file to your browser and the browser puts it all together

• If the web page needs to accomplish something more sophisticated, it can actually ask for a program to be run, either on the workstation or on the web server


• Programs that are run on the browser are either scripts (written in JavaScript, JScript, or similar languages) or "plugins" (support programs with their own processing abilities, such as Java, Macromedia Flash, and others)


• Programs that are run on the server are called CGI (Common Gateway Interface) programs, or CGIs; a CGI is either a script (written in REXX, Java, shell script, and so on) or a program written in compiled languages (such as Assembler, COBOL, C, C++, PL/I, Java, and others)

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this page last updated: 18 March, 2007
Copyright © 2007 by The Trainer's Friend, Inc.