A programmable logic controller is a digital computer used for automation of typically industrial electromechanical processes. Invented in the late 1960’s, programmable controllers were primarily used in machinery on factory floors but they are used in many machines needed across a variety of industries. PLCs are designed for multiple arrangements of digital and analog inputs and outputs. They need to be able to stand the rigors of factory floors and their temperature ranges, electrical noise, vibrations and impacts. A PLC can run an automatic machine year after year with little ‘assistance’ from humans. PLCs are an example of a "hard" real-time system where output results are produced in response to input conditions within a limited time. The PLC programs are a set of instructions to turn on and off outputs based on input conditions and the internal program. PLCs have continued to evolve over the years and become more intelligent. PLCs have been used in electrical communi