ASP in a Nutshell, 2nd Edition

Active Server Pages and Active Server Pages 2.0

Late in the life of Internet Information Server 2.0, Microsoft began public beta testing of a technology whose code name was Denali. This technology is now known as Active Server Pages and is a very important aspect of Microsoft's Internet Information Server strategy.

This ASP technology is encapsulated in a single, small (~300K) DLL called ASP.DLL. This DLL is an ISAPI filter that resides in the same memory space as Internet Information Server. (For more about how IIS is configured to use ISAPI filters, see Appendix C.) Whenever a user requests a file whose file extension is .ASP, the ASP ISAPI filter handles the interpretation. ASP then loads any required scripting language interpreter DLLs into memory, executes any server-side code found in the Active Server Page, and passes the resulting HTML to the web server, which then sends it to the requesting browser. To reiterate this point, the output of ASP code that runs on the server is HTML (or HTML along with client-side script), which is inserted into the HTML text stream sent to the client.^[2] Figure 1.2 illustrates this process.

Figure 1.2. Dynamically generated web content: request and delivery

^[2] Note, however, that an Active Server Page application could just as easily send XML, for example, to the browser. HTML is only the default.