PLC programming developers are responsible for developing code that controls programmable logic controllers (PLCs). PLCs are devices that control industrial machinery and processes. They are used in a variety of industries, including manufacturing, oil and gas, automotive, food and beverage, pharmaceuticals, and more. PLC programming developers create programs that tell the PLC what to do under certain conditions. For example, they may develop a program that turns on a conveyor belt when a sensor detects a product in front of it.