The story so far has been a narrative about the development of two very contrasting types of computational artifacts. On the one hand, Alan Turing conceived the idea of a purely abstract and formal artifact—the Turing machine—having no physical reality whatsoever, an artifact that belongs to the same realm of symbols and symbol manipulation, as do mathematical objects. On the other hand, the major part of this narrative has been concerned with a material artifact, the computer as a physical machine that, ultimately, must obey the laws of physics—in particular, the laws governing electromagnetism and mechanics. This was as true for Babbage’s machines (which were purely mechanical) as for Hollerith’s tabulator, as true for the electromechanical machines, as for the Harvard Mark I and the Bell Telephone computers, as true for the ABC and the ENIAC, as for the EDSAC and the Manchester Mark I. Beginning with the EDVAC report, and especially manifest in the development of the first operational stored-program computers, was the dawning awareness of a totally new kind of artifact, the likes of which had never been encountered before. Philosophers speak of the ontology of something to mean the essential nature of that thing, what it means to be that thing. The ontology of this new kind of artifact belonged neither to the familiar realm of the physical world nor the equally familiar realm of the abstract world. Rather, it had characteristics that looked toward both the physical and the abstract. Like Janus, the Roman god of gates, it looked in two opposite directions: a two-faced artifact—which, as we will see, served as the interface between the physical and the abstract, between the human and the automaton; a liminal artifact, hovering ontologically between and betwixt the material and the abstract (see Prologue, Section IV ). So uncommon was this breed that even a name for it was slow to be coined. During the Cambridge conference in England in 1949, we find a session devoted to programming and coding.