Penn Library

John W. Mauchly and the Development of the ENIAC Computer

The EDVAC Design

The fact that the ENIAC was such a revolutionary machine contributed to the second controversy that has marked its history--the development of the "stored program concept." By no means did the ENIAC have all of the architectural features of a modern computer: it was a wartime project, and the exigencies of doing something quickly justified a straight-forward design. But this contingency meant that all of the groups who subsequently took an interest in the ENIAC could propose improvements to the machine, thereby fueling priority disputes over who first came up with a particular concept.

By the spring of 1944 it was clear to many people who had been working on the ENIAC that there were ways to improve its method of operation. Foremost among these new design ideas were methods for simplifying the process of programming and wiring the machine. Realizing this fact well before the ENIAC was operational, Mauchly, Eckert, and other members of the project were already thinking of mechanisms that would simplify programming procedures in a new machine. They included the idea of storing programs within some special mechanism. The prospects of building this improved machine materialized when the Bureau of Ordnance issued a follow-on contract for the EDVAC computer.


Photograph of EDVAC, ca. 1948. (click to expand to 83k)
It was the highly skilled mathematician, John von Neumann, who produced the best formal description of a stored program computer. During the fall of 1944 von Neumann took time off from his work at the Institute for Advanced Studies in Princeton, New Jersey and the Los Alamos Project to take part in the Moore School discussions regarding the EDVAC design. No official reports or minutes came out of these joint discussions, making issues of credit very difficult to resolve. Instead, Von Neumann independently drafted a report titled the "First Draft Report of the Edvac Design." As a draft document merely reflecting his current thoughts, von Neumann had not attempted to attribute or resolve issues of credit. But Herman Goldstine had given the document wide circulation, which had the unfortunate (or fortunate) result of placing the knowledge in the public domain.

Plan of EDVAC, n.d. (click to expand to 83k)
The controversy here reflects, in part, the different cultures of electrical engineers and mathematicians. Whereas electrical engineers tend not to publish their ideas before they turn them into concrete inventions, mathematicians often circulate their ideas amongst colleagues even before they are ready to release them in a publication. Both sides failed to appreciate the different conventions of their respective fields, fueling the priority disputes that ensued.


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