Wednesday, January 5, 2011

Interactivity on the Web

Five years ago, the Web was very static. You could see text and graphics and you could click on links. Then other types of media started to appear; sound, animation, video and interactive applications. The interactivity was brought about by four different techniques. The first is the Plug-in technique. A plug-in is not a part of a browser. It is a separate program that is invoked by the browser when it encounters a file with a format that the plugin module can understand. There are hundreds of plug-ins on the Internet that you can download and install on your computer. Some of them cost money, but most of them are free.


The difficulty with plug-ins is that you have to find them, download them and install them. First you must find the right plug-in on the Internet. There are different plug-ins for different platforms, so you have to make sure that the plug-in that you want to download is the right one. Then you have to download the plug-in; a process that typically takes 10 to 20 minutes through a 28.8 kbps modem. The file you’ve downloaded is almost always archived and compressed, so you have to decompress and de-archive it. Then you have to install the plugin before you’re ready to use it.


There is another variant of the plug-in technique called a helper application. A helper application is exactly the same thing as a plug-in, that is a small program that is invoked by the browser. The only difference is that a plug-in shows its information within the window of the browser, while a helper applications shows its information in an external window.

The second technique is called CGI, which stands for Common Gateway Interface. One use is for entering data in a form on a web page and submitting it by clicking on a button. Another use is to sense where the user clicks on an active image area. There are many other ways to use CGI.


The third technique, called the Scripting Languages, involves extending the HTML code by using a programming language called a script language. The code of the scripting language is mixed with the HTML code. When you open an HTML page with a word processor you can actually see the code of the scripting language. The browser interprets the scripting language code in a similar way it interprets the HTML code. The most common scripting language is JavaScript.

The fourth technique is Java. This technique involves sending, not just the data from the server to the client, but also the program that will handle this data. In this way users don’t have to find, download and install plug-ins on their computers.

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