The Common Gateway Interface or CGI is a standard way to interface external application of program. Here the function of the server like HTTP or any other web server is also important. Any text file including HTML document is static in nature that means the text files do not change. But on the other hand a CGI program is executed within a time-frame and as a result the CGI program provides dynamic information.

It is most important for us to know how exactly the CGI program functions. Now let us start with an example. Suppose you want to hook up any individual UNIX data base in the WWW or World Wide Web. You want to do this to allow the web users all over the world to get it according to their requirement. You can do this by using CGI program. Foe this you have to create a CGI program, which the daemon of web can execute to pass the data or information to the engine of database. Apart this, the CGI program also help to receive back the information to produce before the client. This is a perfect example of gateway.

This CGI sounds very simple, but in many occasions it is very difficult to execute. Using this CGI program you can hook up any thing to the World Wide Web. But while doing so you have to remember one thing; your CGI program must not take longer time to process it. If it takes too much time to process, the user will have to wait for loner period, which is not at all desirable. This common gateway interface serves as a way to pass the request of the web user for the application of a program and thereby helping to get back desired data or information at the click of the mouse. The CGI works as a gate of passing request of web user and producing data before him.