1. Introduction and Prologue

It is said that the past is prologue. This saying is borne out by most of the history of science, but it applies only loosely to computer science, since this “modern” science does not have that much of a past compared to the traditional sciences like physics and chemistry. In the latter, in any era the events of the past do presage the ongoing and future development of these sciences. The development of computer science proceeds at such a rapid and frenetic pace that the boundary between past events and the current state of the subject is somewhat blurred. In this book, with its advisedly provocative title referring to the heart of computer science, we take the position that its prologue is indeed rather brief and somewhat diffuse. To recount how the history of computer science interacts with its current state we adopt a simplifying assumption about its early history, the reasonableness of which we shall defend, to the effect that the early and defining history of computer science (the prologue) can be encapsulated in the work of one man, the British mathematician Alan Turing. Except for some very early and rather naïve contributions by the outstanding mathematicians Pascal and Leibniz and some later more substantial ones by the polymath Babbage and the logician Godel, the subject which we now call computer science sprang largely from the brilliant and original researches of Turing, as we shall attempt to illustrate.