Lessons from experience in software engineering for process and production control

Seven online systems installed by one industrial user of computers are classified and the experience reviewed. A change in project style and a trend in the use made of manufacturer´s software are reported. Many features have appeared which are widely recognised as producing efficient programs. Examples are used to show the importance of the hidden features of high-level languages, especially for the user of minicomputers, and to support the general structure of a model of programming activity which has been previously advanced elsewhere. This model enables important conclusions to be drawn on more than an ad hoc basis for the implementation of distributed and interactive systems of computers. In particular, as the cost of software and its maintenance comes to dominate the total cost of a system, the use of real-time languages (r.t.l. s) will be an economic necessity, via the better programming and improved documentation they make possible.