PLC stands for "Programmable Logic Controller" and refers to a computer-based control unit used for the (electronical) open-loop or closed-loop control of machines and systems. Functionality is determined by an application that is relatively easy to create using standardised programming
languages. The sensors and actuators are connected to this assembly in analog or (increasingly) digital fashion via a data bus (see Bus) to minimise wiring outlay.
A PLC processes the sensor signals, calculates the responses required, and controls the actuators in cyclical programs while the application indicates the current status of the sensors so that the user can control the actuators in line with requirements and achieve the desired results.