Editing Programmable logic controller (section)

=== User interface ===
{{See also|User interface|List of human-computer interaction topics}}
[[File:Control-panel-plc.jpg|thumb|upright|Control panel with a PLC user interface for [[Thermal oxidiser|thermal oxidizer]] regulation]]

PLCs may need to interact with people for the purpose of configuration, alarm reporting, or everyday control. A [[SCADA#Human-machine interface|human-machine interface]] (HMI) is employed for this purpose. HMIs are also referred to as man-machine interfaces (MMIs) and graphical user interfaces (GUIs). A simple system may use buttons and lights to interact with the user. Text displays are available as well as graphical touch screens. More complex systems use programming and monitoring software installed on a computer, with the PLC connected via a communication interface.