Foreword reliability and safety in real-time systems

BUILDING safe and reliable software is a major problem when using computers in safety-critical environments where failures could result in loss of life and tremendous economic costs. These systems are both complex and must operate in real-time. The single most important characteristic of any real-time system is that its actions, or inactions, cannot be overlooked or ignored; the system can never be returned to a prior state. The effect that a decision of the computer system has on the controlled system and, in turn, the controlled system on the real world may be desirable, inconvenient, or disastrous: it is never inconsequential. This requires that each decision must be correct and, because of this, extra care and effort must be involved in producing such systems in order to enhance their reliability and safety.