In parallel with the development of data processing applications for computers, effort was directed to other areas in which computers might provide benefits for the user. One early effort was the application of computers to the monitoring and control of industrial processes such as those used in oil refinery units, steel plants, and paper machines. Over time, these early efforts were generalized to a broader class of applications in which the computer was connected directly into an external process which placed time response requirements on the computer system. These systems have become known as real-time systems. In this paper, the evolution of IBM small real-time systems is traced from the late 1950s to the present. Emphasis is placed on a few features and requirements which characterize these systems.