of reconfiguration. This allowed for easier iteration over manufacturing process design. With a simple programming language focused on logic and switching operations, it was more user-friendly than computers using general-purpose programming languages. It also permitted its operation to be monitored. Early PLCs were programmed in ladder logic, which strongly resembled a schematic diagram of relay logic. Modicon In 1968, GM Hydramatic (the automatic transmission division of General Motors) issued a request for proposals for an electronic replacement for hard-wired relay systems based on a white paper written by engineer Edward R. Clark. The winning proposal came from Bedford Associates from Bedford, Massachusetts. The result was the first PLC—built in 1969–designated the 084, because it was Bedford Associates' eighty-fourth project. Bedford Associates started a company dedicated to developing, manufacturing, selling, and servicing this new product, which they named (standing for modular digital controller). One of the people who worked on that project was Dick Morley, who is considered to be the "father" of the PLC. The Modicon brand was sold in 1977 to Gould Electronics and later to Schneider Electric, the current owner. About this same time, Modicon created Modbus, a data communications protocol used with its PLCs. Modbus has since become a standard open protocol commonly used to connect many industrial electrical devices. One of the first 084 models built is now on display at Schneider Electric's facility in North Andover, Massachusetts. It was presented to Modicon by GM, when the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84 moniker at the end of its product range until the 984 made its appearance. Allen-Bradley In a parallel development Odo Josef Struger is sometimes known as the "father of the programmable logic controller" as well. He was involved in the invention of the AllenBradley programmable logic controller and is credited with inventing the PLC initialism. Allen-Bradley (now a brand owned by Rockwell Automation) became a major PLC manufacturer in the United States during his tenure. Struger played a leadership role in developing IEC 61131-3 PLC programming language standards. Early methods of programming Many early PLCs were not capable of graphical representation of the logic, and so it was instead represented as a series of logic expressions in some kind of Boolean format, similar to Boolean algebra. As programming terminals evolved, it became more common for ladder logic to be used, because it was a familiar