Forms and CGI: What are they?

There are two parts two providing user interaction in HTML forms:

Form

-- the HTML form itself. The User Interface.

A CGI script

-- a program which resides on the Web server itself. This program is written in a language such as Perl, C/C++, TCL, AppleScript, or another Common Gateway Interface (CGI) language.

The Common Gateway Interface

The role of this CGI program is:

• to accept the data which the user inputs and
• do something with it.
• usually, send a reply back to user.

Figure: The Common Gateway Interface

What does a CGI program do?

• That depends on what the program has been written to do.
• It could e-mail the data to someone,
• or add an entry to a database,
• or write out a text file,
• or create a customized display,
• or just about anything else you can think of.

For this section we will concentrate on the User interface (HTML side) of Forms. Subsequent sections will deal with CGI and Perl programming.