Now, the server receives this GET request. It fires up the program (hello.pl) and returns the output, verbatim. But this description fails to include exactly how the WEB page ends up communicating with the program. Communication requires a protocol or set of conventions, CGI provides this convention. In particular, as we will see in the next class, it describes how arguments should be passed to programs, and provides the program with a set of Environment Variables, for example, the type of browser the initiator of the request was using, the IP address of the initiator etc.
It's a common misconception that CGI is a ``programming language''. CGI allows the WEB page and server to communicate with the program. In summary, CGI is the protocol which allows programs to be executed over the WEB.
Today, we won't deal with CGI, because we won't be using environment variables and passing parameters to the program.