CGI
CGI stands for Common Gateway Interface.
Scripts are used for two-way interaction between the Web site and the user browsing it. They can be used flexibly, for instance to obtain information from the user and to act accordingly upon it.
A CGI script can be used to create programs to update your web page, with the results depending on user input. It provides a standard way to obtain input. This can be from a form using environmental variables or from the URL that invoked the script using parameters. The output of the script is returned to the Web browser as HTML. CGI also lets users send you e-mail and lets you check errors. Note that not all browsers are forms-enabled. CGI defines how the input from the user is supplied. Your CGI scripts should be authorised by the webmaster of the server upon which they are to rune before they are executed, as they could compromise the server.
TCL stands for the Tool Command Language, which is a CGI scripting language. Dr. John K. Ousterhout developed it. It is a portable and extensible shell language. It is often used with the Tk toolkit.