From its creation, developers recognized Hypertext Markup Language's restriction of only allowing the creation of static content as a problem that placed limitations on the rapidly expanding area of Web technology.
Developers wanted a way to add dynamics to applications; to render content from
a database or to accept interaction with users. To achieve this goal, companies
creating servers devised complementary technologies to allow for dynamic use of
the Internet. Microsoft presented the Internet Server API (ISAPI) for its
Internet Information Services (IIS) — also adopted by Apache — and Netscape
developed NSAPI (Netscape Server API) for the same purpose.
ISAPI consists of two principal parts,
Extensions and Filters. Extensions are 'standard' applications that run from a
Web request. The best known ISAPI Extension is the 'QueryString' that appears at
the end of an URL in the form of an interrogation sign with at least
one parameter, with each parameter
separated by '&'(Forexample,http://Server/default.aspx?paremeter1=value1¶meter2=value2).
Filters are, as the term implies, elements that distillate and modify
the information between the request and the response from the Web
Programming the ISAPI has never been a simple matter. The
technology is very complex, the developer must work directly with the
assemblies from Win32, and because traditionally, it has only been possible
using C/C++. As an alternative, ASP.NET introduced HttpHandlers and
HttpModules.
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