A programmable logic controller PLC or programmable controller is an industry digital computer which has been ruggedized and adapted for the control of manufacturing processes, such as assembly line, or robotic devices, or any activity that requires high-reliability control and ease of programming and process fault diagnosis.
They were first developed in the automobile industry to provide flexible, ruggedized and easily programmable controllers to replace hard-wired relays and timers. Since then they have been widely adopted as high-reliability automation controllers suitable for harsh environments. A PLC is an example of a “hard” real-time system since output results must be produced in response to input conditions within a limited time, other is unintended operation will result.
