Programmable logic controller (PLC) is a digital operation electronic system specially designed for industrial environment applications. It uses programmable memory, which stores instructions for logical operation, sequence control, timing, counting and arithmetic operation, and controls various types of mechanical equipment or production processes through digital or analog input and output.

Programmable logic controller (PLC) is a kind of digital operation controller which is automatically controlled by microprocessor. It can load control instructions into memory for storage and execution at any time. Programmable controller consists of CPU, instruction and data memory, input/output interface, power supply, digital-to-analog conversion and other functional units.

The early programmable logic controller only had the function of logic control, so it was named programmable logic controller. Later, with the continuous development, these simple computer modules already have many functions, including logic control, time sequence control, analog control, multi-computer communication and so on, and their names have also been changed to programmable controllers.

However, due to the conflict between the abbreviation of PC and the abbreviation of personal computer, and the reasons of habit, people often use the name of programmable logic controller and still use the abbreviation of PLC.