Human Machine Interface software gives machine operators a way to interact with and manage a system. This interaction is through a graphical user interface (GUI).
Supervisory control and data acquisition (SCADA) is a control system architecture that uses computers, networked data communications and graphical user interfaces for high-level process supervisory management, but uses other peripheral devices such as programmable logic controllers (PLCs) and discrete PID controllers to interface to the process plant or machinery.
The operator interfaces which enable monitoring and the issuing of process commands, such as controller set point changes, are handled through the SCADA supervisory computer system. However, the real-time control logic or controller calculations are performed by networked modules which connect to the field sensors and actuators.