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CGI Flash Java HTML has come a long way since it was first developed, giving Web designers many more graphical layout options. However, HTML by itself provides almost no interactivity beyond the ability to "jump" between sections of a document or from one page to another. Nevertheless, there are ways to turn a static site into a dynamic one, enabling visitors to do a number of useful things. For example, readers can search for information in a database or select several items from a form and get a customized reply. One way to accomplish this type of interactivity is by using a Common Gateway Interface script, commonly known as a CGI or a gateway script.
Common Gateway Interface (CGI)Simply put, a gateway script is a program that runs on a web server and is triggered by input from a browser. The script is usually a link between the server and some other program running on the system, like a database. Most of the work happens on the server, behind the scenes. You only see the result. The beauty of CGI is that it allows two-way communication through the use of HTML.
The real value of gateway scripts, however, is realized through the use of online forms. These can range from simple e-mail forms or data entry boxes for searching, to complex surveys with multiple choices or purchase order forms that process orders online. A form is set up in HTML in a way that lets someone enter information by selecting buttons, pulling down or scrolling through menus, entering text into data entry fields, or combinations of all of these features.
At the bottom of the form there are usually two buttons, one to reset the form and one to submit the data. The Submit button sets the process in motion. It sends information to the server pointing it to the CGI directory and to the appropriate script to run the procedure. Here's the sequence of events:
Each script has a special header that gives the server, and eventually the browser, information about the output it is sending. That way, it knows how to properly format the output at each step of the process. The header isn't actually part of the document and it's never displayed anywhere. CGI is widely used on the Web and probably will continue to be for some time to come. However, new tools promise to open the doors to more sophisticated ways of expression and communication, taking interactivity on the Web to another level.
Flash
Another widely used tool is a product called Flash from Adobe, Inc. Flash
is an animation and authoring program specifically developed for use on
the Web. Viewing Flash animations requires a plug-in, a software program
specifically designed to work with an existing program, in this case, a web browser. Flash plugs into
your web browser and plays animations embedded on a web page, in real-time.
Internet Explorer, Firefox, Netscape Navigator and Safari all support Flash and recent versions come bundled with the plug-in. If you don't already have it, you can download it from the Adobe website. Once you've installed the plug-in, visit the rapidly growing list of Flash showcase sites.
Java Although
Flash represents another milestone for the World Wide Web, the real breakthrough
in interactivity and multimedia content delivery is a programming language
called Java. Developed by Sun Microsystems, Inc., this powerful object-oriented
programming language uses a Java-enabled web browser to run interactive applications.
A well done Java application on a single web page can engage a user for a long time. Rather than just providing text, sound, images, or videos, a Java page offers a place to play, learn, or communicate and interact with others in a way that isn't necessarily based on going somewhere else on the Web through hyperlinks. In this way, Java turns the Web into a software delivery system in which users have things to do rather than just places to go. This offers the potential to transform the surfing behavior of Web users into one of playing and learning in interactive environments. How does it work? Java makes Java browsers "smart" enough to interpret and execute the content, instead of relying on servers to provide information and functionality. When downloading a web page that contains the special hypertext tag called "APP," the Java browser knows that a special kind of Java program called an applet is associated with that page. The browser then downloads a file of information that describes the execution of that applet. This file of information is written in what are called bytecodes. The Java browser interprets these bytecodes and runs them as an executable program on the user's computer. All of this downloading and execution happens automatically. When a Java browser requests a web page, here's what happens:
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Use the Site
The web page, then, is programmed in HTML, and the
gateway script usually is written in a programming
language like C or Perl. Gateway scripts can be used for a wide variety of Web
applications, ranging from the very simple to the complex. For example, a simple CGI script can track the number of visitors with a page counter or it
might automatically update each page with the local time and date.
The most common use of CGI scripts is for implementing
image maps and forms.
An image map is a graphic image with distinct
areas that have different 
A URL points to a gateway script the same way it points to
any other document on the server. The browser requests that URL from a server just as it would any other document.
The server receives the request, notes that the URL points
to a script (based on the location of the file or based on its extension, depending on the type of server), and activates that script.
The
script performs some action based on the input from the browser (for example,
querying a database, calculating a value, or calling up some other program
on the system).
The script formats the result in a manner that the server can understand.
The server receives the result from the script and passes it back to the browser, which formats and displays it for the reader.
