Active Server Pages (ASP), also known as Classic ASP or ASP Classic, was Microsoft's first server-side script engine for dynamically-generated web pages. Initially released as an add-on to Internet Information Services (IIS) via the Windows NT 4.0 Option Pack, it was subsequently included as a free component of Windows Server (since the initial release of Windows 2000 Server). It has now been superseded by ASP.NET.
Developing functionality in ASP websites is enabled by the active scripting engine's support of the Component Object Model (COM), with each object providing a related group of frequently-used functions and data attributes. In ASP 2.0 there were six built-in objects: Application, ASPError, Request, Response, Server, and Session. Session, for example, is a cookie-based session object that maintains the state of variables from page to page. Functionality is further extended by objects which, when instantiated, provide access to the environment of the web server; as an example FileSystemObject (FSO) is used to create, read, update and delete files.