Application Programming Interface (the P is alternately described as Programming/Programmers’/Processing)—A term used to describe the data format, common functions and address information necessary for various computer applications to exchange information. While APIs provide a way for third parties to write applications compatible with a program, operating system, or suite of programs, APIs are often kept confidential by the owner of the program(s) in order to limit competitors’ market access (as well as malicious activities by virus writers and other malign individuals). Much of the Microsoft antitrust and competition cases involved and still involve the issue of access to APIs for Windows¨ and other software. The term has also come to be more broadly used (albeit not technically accurately) in legal discussion to describe interface information and transfer and communication protocols for a wide array of computing products including hardware. See Essential Facilities.

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