1.1 This European Standard specifies the process and technical requirements for the development of software for programmable electronic systems for use in railway control and protection applications. It is aimed at use in any area where there are safety implications. These systems can be implemented using dedicated microprocessors, programmable logic controllers, multiprocessor distributed systems, larger scale central processor systems or other architectures.1.2 This European Standard is applicable exclusively to software and the interaction between software and the system of which it is part.1.3 This European Standard is not relevant for software that has