As the need of automation increases significantly, a control system needs to be easily programmable, flexible, reliable and cost effective. In this chapter review on the programming and applications of Programmable Logic Controller (PLC) in our current market is discussed. Studied on the ladder logic programming, principle of operation and selection of PLC's in engineering studies, industrial control applications and monitoring of plants are reviewed in this chapter. PLC's do have its own limitations, but studies indicate that PLC's have more benefits than limitations. PLC's are used in industrial automation to solve complex problems.