A programmable logic controller, PLC, or programmable controller is a digital computer used for automation of typically
industrial electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or
light fixtures. PLCs are used in many machines, in many industries. PLCs are designed for multiple arrangements of
digital and analog inputs and outputs, extended temperature ranges, immunity to electrical noise, and resistance to
vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile
memory. 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, otherwise unintended operation will result.