A programmable controller – also known as a programmable logic controller (PLC) – is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines. Programmable controllers are used in many industries and machines. Unlike general-purpose computers, a programmable controller is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise and resistance to vibration and impact.
PLCs are well-adapted to a range of automation tasks. These are typically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the total cost of the automation, and where changes to the system would be expected during its operational life.
Programmable controller applications are typically highly customizable. Therefore, the cost of a packaged programmable controller is low compared to the cost of a specific custom-built controller design.