Successful software relies on well-written APIs that meet user goals.
The interface I want to write about is the older one, the interface between two different pieces of software. It's typically called an Application Programming Interface, or API, and is seen only in source code. The invention and evolution of APIs drives the computer industry and defines the character of everyday computing. Programmers naturally understand that they must design user interfaces for the user, but few programmers realize how vital it is for them to create the APIs deep inside the software with the user's goals as the foremost consideration. In the early 1970s, Gary Kildall at Digital Research created the first significant API for microcomputers.