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ASP Basics: What's Happening Back There?


With each new language it seems computers get easier and easier to program. When computers first came into existence, programmers needed to know very cryptic and specific machine instructions to make those ancient behemoths do anything. Before too long assembly languages arose, and then high-level programming languages were introduced with the creation of Fortran. Today we have reusable components, GUI/WYSIWYG designers, and easy to use scripting languages.

As computers become easier and easier to program, though, developers have to know less of what's happening in the bowels of the compiler or interpreter. While this saves time, I think it is important to have a firm grasp on what's going on behind the scenes. I think this is an important thing to know for two reasons: one, it's cool; two, having a better understanding of what's really happening leads to better written code, fewer bugs, and an improved self-esteem!

Client/Server Interaction for Static HTML Files Before we begin discussing how ASP pages "work," let's talk about how static HTML pages "work." The Internet is built on a client/server foundation. That means that there are two parts we must look at when dissecting an Internet transaction: the client and the server. The client is the web browser, be it Internet Explorer, Netscape, Lynx, Opera, or whatever. The server is the web server on which the HTML page exists.

The entire process of retrieving a web page goes like this:

  • You type in the URL into your browser, for example http://www.yahoo.com/index.html
  • Your browser finds the appropriate web server, and to that server says, "I need to look at the file /index.html, please."
  • The web server locates the file /index.html and sends it to the browser as HTML text.
  • The browser collects this text and parses it, determining how to display those colorful animated gifs and blinking text we've all come to love.

Client/Server Interaction for ASP Files It's that simple. The transaction has just three simple steps: the client requests the document, the web server sends the document, the client decides how to display it. With ASP, however, there are some additional steps are taken on the server before the HTML text is sent back to the client. Let's look at what happens with ASP:

  • You type in the URL into your browser, for example http://www.ASPisNeat.com/default.asp
  • Your browser finds the appropriate web server, and to that server says, "I need to look at the file /default.asp, please."
  • The web server locates the file /default.asp and parses out the ASP code, turning all of the ASP code into applicable HTML code. ASP code is code inbetween the ASP script delimiters (<% ... %>) or in OBJECT tags with the RUNAT=Server property set. Since all of the ASP is parsed into HTML, the client sees absolutely no ASP code!
  • The browser collects this HTML text and parses it, determining how to display those colorful animated gifs and blinking text we've all come to love.

You'll note that there is again just three steps, although the second step is a bit more involved. The whole process starts with the client requesting a file with a .ASP extension. The web server notes the extension, and since it has a .ASP extension (as opposed to a .txt, .htm or .html), the server parses the contents of the requested file before sending it to the client. So when you view an ASP file through IE or Netscape, your browser doesn't know that the .asp file is any different from a standard .html file!

  • Proceed to Part 2


  • Article Information
    Article Title: ASP Basics: What's Happening Back There?
    Article Author: Scott Mitchell
    Published Date: Monday, August 23, 1999
    Article URL: http://www.4GuysFromRolla.com/webtech/082399-1.shtml


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