- A microprocessor and a microcontroller are both chips while a PLC is a complete system.
- A microprocessor needs external memory- and I/O-chips, while these are integated in a microcontroller.
- A PLC consists of at a printed circuitboard, a microprocessor with external chips or a microcontroller, and interface circuits to communicate with the "ouside world", all this is usually mounted in a "box" with easy accessible connections.