ISAPI (Internet Server Application Programming Interface)

The Internet Server Application Programming Interface (ISAPI) is the API of Internet Information Services (IIS), Microsoft's collection of Windows-based network services. ISAPI was designed to model N-tier architecture. ISAPI enables programmers to develop web-based applications that run much faster than conventional CGI programs because they're more tightly integrated with the web server. In addition to IIS, several web servers from companies other than Microsoft support ISAPI.