Most operating environments, such as MS-Windows, provide an API so that programmers can write applications consistent with the operating environment. Although APIs are designed for programmers, they are ultimately good for users because they guarantee that all programs using a common API will have similar interfaces. This makes it easier for users to learn new programs.

DOS Protected Mode Interface (DPMI)
This is a programmer's reference copy of the DOS Protected Mode Interface, a protected mode API specification for DOS extended applications.

Microsoft Internet Server API (ISAPI) information page
Provides a brief description of Microsoft's Internet Server API (ISAPI), along with a link to information on CGI.

eBay API For Developers
With the eBay API you communicate directly with the eBay database in XML format. By using the API, your application can provide a custom interface, functionality and specialized operations not otherwise afforded by the eBay interface.

Google Maps API
The Google Maps API lets you embed Google Maps in your own web pages with JavaScript. The API provides a number of utilities for manipulating maps and adding content to the map through a variety of services, allowing you to create robust maps applications on your Web site.

Webopedia Did You Know...? All About DirectX
While you may be familiar with the "Would you like to install DirectX now?" window, do you know what DirectX is, and why it is important to keep an updated version of it on your PC?