Real Time

What is REAL TIME ?

It is important to emphasize that a desire for rapid processing, either on the part of the designer or on the part of the client for whom the system is being developed, is not enough, on its own, to justify the description real time. This is often misunder stood, even by developers within the software industry.

A Anecdote

We build systems that reside in a small telemetry computer, equipped with all kinds of sensors to measure electromagnetic fields and changes in temperature, sound and physical disturbance. We analyze these signals and transmit the results back to a remote computer over a wide-band channel. Our computer is at one end of a one-meter long bar and at the other end is a nuclear device. We drop them together down a big hole in the ground and when the device detonates, our computer collects data on the leading edge of the blast. The first two-and-a-quarter milliseconds after detonation are the most interesting. Of course, long before millisecond three, things have gone down hill badly for our little computer. We think of that as a real-time constraint.

De Marco, writing in the foreword to Hatley and Pirbhai, 1987