On the implementation of control loops by software

This article is intended to present a survey of what we consider as one of the central aspects of embedded systems, namely the realization of control systems by software. Although computers are today the most popular medium for implementing controllers, we feel that the state of understanding of this topic is not satisfactory, mostly due to the fact that it is situated in the frontier between two different cultures and world views (control and informatics), which are not easy to reconcile. The purpose of this article is to clarify these issues and present them in a uniform and, hopefully, coherent manner