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The application of computers for controlling process units is now about ten years old. The applications have progressed from the experimental stages of early development to a well-established (economically speaking) control practice. This has not been without some anxious moments and a few outright failures. These have not been forgotten, but current successes are proving beyond any doubt that digital computers are capable of generating an attractive economic return on the investment required for their installation. This paper has three objectives: first, to acquaint those outside the process industries of the general process control problem in order that they may appreciate some of the requirements imposed on a control computer; second, to describe the computer hardware normally considered for process control; third, to present the general philosophy of the real-time software systems required for process control. [ABSTRACT FROM AUTHOR]

The concept span of control has been interpreted so widely over the past years that in its present form its use as a means of communicating information among scholars has become severely impaired. This article argues that it is a useful concept for measuring the closeness of contact between a superior and his subordinates, Data are presented which demonstrate that different operational definitions of the term will produce not only greatly different mean values of the span of control, but also different correlation coefficients with other important structural variables. A new operational measure is proposed in order to develop a common language of measurement that will facilitate an understanding of organizational structure. [ABSTRACT FROM AUTHOR]