The SCADE tool has been used from many years for the development of safety critical software in the nuclear, aeronautics and railways sectors. The language supported by this tool is also called SCADE and is based on the formal language LUSTRE. In this book, the authors present the SCADE language (syntax and semantics) along with some examples of use. Within the field of aeronautics, the SCADE tool is used by both Boeing and Airbus. In the railways sector, all the major companies throughout the world have used this tool. There are currently no books that present the SCADE language and tool, and thus this book will be the first to tackle this subject. It is especially useful as new versions of standards recommend that the language used in safety critical applications be formalized.