Strictly, this is a method by which an operator can interact with a machine. When applied to computer-based measurement, monitoring or control equipment this typically refers to the interface between an operator and the computer program. This is usually in the form of a graphical display with some operator inputs, such as a keyboard, mouse, touch-screen or operator buttons. In this context, an HMI differs from a full graphical user interface in that it typically has a simplified layout designed to provide only necessary functionality. This ensures that the system can be operated efficiently without the hinderance of all configurable settings being visible to the operator.