This part of IEC 61131 defines a language for the programming of Fuzzy Control applications used by programmable controllers. The object of this part of IEC 61131 is to offer the manufacturers and the users a well-defined common understanding of the basic means to integrate fuzzy control applications in the Programmable Controller languages according to IEC 61131-3, as well as the possibility to exchange portable fuzzy control programs among different programming systems. To achieve this, annex A gives a short introduction to the theory of fuzzy control and fuzzy logic as far as it is necessary for the understanding of this part of IEC 61131. It may be helpful for readers of this part of IEC 61131 who are not familiar with fuzzy control theory to read annex A first.