CGI, or Common Gateway Interface, is often misunderstood as a protocol that connects a web server to a legacy information system, such as a database. However, it refers to an interface to external server programs that allow users to interact with services they may not normally have access to.

The concept of CGI was born in 1993 at the National Center for Supercomputing Applications (NCSA), where the pioneering Mosaic web browser also originated. Rob McCool, a prominent figure in the development of NCSA HTTPd - one of the world's first web servers and the direct ancestor of the open-source Apache web server - took the lead in writing the CGI specification.

The aim was to create a common standard for various web servers (including CERN httpd and Plexus server) so that software programs initiated via a web page could run on any server and send the result back to the web page. This marked the beginning of web applications, allowing early users to run interactive programs. After a CGI script was executed on a server, the result was sent back to the originating web page as HTML code.

In contrast to JavaScript, which performs interactive tasks inside the browser (client-side), CGI scripts ran via an external program on a server (server-side). While a CGI script wasn't a dynamic component in the browser like JavaScript, it did allow early web users to interact with programs. The version defined by this spec will be CGP/1.0.

The NCSA HTTPd Home Page, April 1997

The Invention of CGI

The idea was to create a common specification for the various web servers (others active in 1993 included Tim Berners-Lee's CERN httpd and Tony Sanders' Plexus server), so that a software program initiated via a web page could run on any server and send the result back to the web page.

In many ways, it was CGI - not JavaScript - that was the start of web applications. McGool spent some time writing up a formal specification for the Server-gateway interface. On November 17th, 1993, he posted a message to the www-talk mailing list:

'This is a preliminary specification of the Common Gateway Protocol, or CGP. I invite any and all comments and suggestions.'

Over time, CGI has evolved into a crucial aspect of web development, enabling developers to create dynamic and interactive web pages. In conclusion, CGI stands for Web Programming, and its invention in 1993 marked the beginning of web applications as we know them today.

Cgi stands for web programming