Pitfalls and Safeguards in Real-Time Digital Systems with Emphasis on Programming

Real-time digital systems are largely a technical innovation of the past decade, but they appear destined to become more wide spread in the future. They monitor or control a real physical environment, such as an air-traffic situation, as distinguished from simulating that environment on an arbitrary time scale. The complexity and rapid variation of such an environment necessitates use of a fast and versatile central-control device, a role well suited to digital computers. The usual system will include some combination of sensors, communication, control, display, and effectors. Although many parts of such a system pose no novel management problems, their distinguishing feature, the central digital device, frequently presents unusually strict requirements for speed, capacity, reliability and compatibility, together with the need for a carefully deisgned stored program. These features, particularly the last, have implications that are not always foreseen by management. An attempt is made to point out specific hazards common to most real-time digital systems and to show a few ways of minimizing the risks associated with them.