TABLE OF CONTENTS The IEC standard defines a large number of common features and elements that apply to all the programming languages. The internal behaviour of program organisation units, i.e. programs, function blocks and functions, can be described using any one of five different languages. However, irrespective of the language used, the variables and data types handled by all POUs are described using the same common programming elements.
For example, input and output variables of a function block will be described in the same terms whether the function block is programmed using Ladder Diagram, Function Block Diagram or Instruction List.
