The development of fault free software [for railway trains]

Transportation systems demand reliability of their components. With the advent of electronic control systems, electronic components have been developed which will operate reliably in the harsh environmental conditions encountered. As the complexity of control has increased, microprocessors and microcontrollers have been included in the systems, bringing with them the problem of software reliability. As a result of experience gained in developing the software for the highly successful British Rail time division multiplex equipment, this paper demonstrates that reliable software, which meets all its functional and operational requirements, is fault-free software. If fault-free software is to be produced, the concept must be introduced from the inception of the project