Analog/hybrid: what it was, what it is, what it may be

The history of the analog computer goes back to antiquity, where tax maps were first reported being used for assessments and surveying. However, I shall confine this paper to the analog computer as it evolved from World War II to the present time. For those interested in the history of the analog computer, from antiquity to World War II, I refer the reader to an excellent introductory article by J. Roedel, Reference 1. The "Palimpsest" in which Roedel's history of the analog computing art is included is in itself an excellent history of analog computers in the early days dating from World War II to about 1954. From page 4 of the Palimpsest, I would like to show a diagram of computing devices as visualized by George Philbrick for an article in Industrial Laboratories in May, 1952. Of interest to us in this diagram on the analog side, is the separation, at the bottom, between fast and slow analog which I will discuss shortly. We will also note the presence of hybrid at the very top, and this article was written in 1952! Of course, Mr. Philbrick's "hybrid" was reserved for the use of the analog computer first to obtain a ball-park idea of a solution, then followed by a separate digital solution to obtain a more accurate answer to the same problem. I am certain that very few people thought of this as being hybrid computation at the time. However, consider this definition in the light of later work reported by Mark Connelly (Reference 2) in his use of a "skeleton" representation of a problem on the analog in conjunction with a more accurate representation of the problem on the digital.