• This graphical language is part of the IEC 1131-3 standard.
• There are different data types for the connection lines.
• Inputs and outputs can be negated by adding a inverting input or output.
• The functions in the diagrams are based on the other functions available. The inputs to a function enter on the left of the block, and the outputs of the function emerge from the right.
• Some functions can have a variable number of arguments. Here there is a third value input to the add block. This is known as overloading.
• The ADD function in the example must always have the same inputs, other functions may have variable numbers of arguments.