PLC (Programmable Logic Controller)

A PLC is a ruggedized, purpose-built industrial computer that runs the logic controlling a specific piece of physical equipment — for example, opening and closing a valve based on a pressure reading, or sequencing a conveyor belt. PLCs operate close to the physical process itself (the "field" layer), executing simple, deterministic logic reliably and continuously, often for years without interruption.

PLCs report data up to and receive commands down from higher-level systems like SCADA.