The CGI (Common Gateway Interface) is the standard by which external programs (often called gateways) interface with your HTTP servers. Thus CGI programs act as gateways between the HTTP server and databases, or between the server and local programs or document generators. For example CGI program can be designed to handle an information request to a database, take the results and assemble an HTML document from it, and return this document to your browser. Consequently CGI gateway programs are used to process information obtained via ISINDEX, FORMS or ISMAP (active image map) requests to an HTTP server.
With NCSA HTTP servers the CGI programs and scripts are placed
in a special directory named cgi-bin. This directory
is referenced by the url http://stuff.cc.dd/cgi-bin/.
Therefore whenever you see this url you know a cgi-bin program is being
accessed.
The NCSA documentation described in detail how to write these scripts, and mentions important ** security issues **. Please read the NCSA CGI documentation.