When the server is asked for a document, it first checks if it is a CGI script. CGI scripts must belong to one of the CGI paths or their subpaths, or must match with one of the path patterns listed in the CGI Paths.
Abyss Web Server is able to run standalone executable files (files which executable attribute is set using the command chmod +x <File>; see chmod reference in your system's manual). For other kinds of scripts, the server tries to find the suitable interpreter to run them by checking the CGI Interpreters table and matching the script's extension with a declared interpreter.
Abyss Web Server automatically detects NPH (Non Parsed Headers) scripts. NPH scripts output is sent directly to the browser without prior header decoding by the server. It is up to NPH scripts to generate correctly all the necessary HTTP response headers. Abyss Web Server considers a script to be NPH if the the first line it outputs starts with the string HTTP/.