the standard from IEC a lot of function blocks are described. Here’s an overview of the most important blocks in the official FBD description.The most basic functionality of a PLC program is logic. Combined called combinatorial logic. Logic is the simplest form of algorithm that, via the states of its inputs can set some outputs. Basically, there are two different bit logic functions or operations in FBD. With just these two you can derive a whole bunch of other logic functions.But let’s sSee more on plcacademy.com A block diagram will not show every wire and switch in detail, that's the job of a circuit diagram. A block diagram is especially focused on the
input and output of a system. It cares less about what happens getting from input to output.