Programmable Logic Controllers or more communally referred to as PLCs, are a type of industrial microprocessor control device that continuously reads input and executes outputs according to the programmed logic. PLCs are typically programmed in either Ladder Logic or structured text.
A PLC has multiple predefined memory addresses which are used for storing different types of data.
Below are links for the Omron PLC Demonstration posts that go over selection of hardware, setup, programming and other project additions to the core display.