1. A common boundary between two systems, devices, or programs.
2. The signal connection and associated control circuits that are used to connect devices. See also standard interface.
3. Specification of the communication between two program units. For example, if a procedure does not refer to nonlocal variables, its interface is defined by the parameter list. Careful definition of interfaces makes it possible to use a program unit without knowledge of its internal working, and is vital to the design of a system that is to be implemented by a team of programmers. The concept is an important feature of Ada; in Ada a package is defined in two parts, the interface and the body. The interface specifies exactly what identifiers are visible outside the package, and is sufficient to permit separate compilation of program units that use the package. Similar facilities are found in most modern programming languages and they are essential features of object-oriented languages such as C++ and Java.
4. To provide an interface.