Fail-Safe Software — Some Principles and a Case Study

A method is presented that leads to programs, which are failsafe with respect to their control flow or their data flow. The basic principle is: during the testing phase a self supervision memorises what has been tested, during the online phase it is decided whether the actual run is among the tested ones. If this is true, the output is performed as forseen by the program, if not, a safety action is taken.