Home Page
Description of the ENIAC

"ENIAC, was the introduction of vacuum tubes for fast, reliable digital computation. It began with John V. Atanasoff's digital electronic, special purpose computer, conceived and built at Iowa State College (now University) between 1935 and 1942, and it led to the ENIAC through an idea Atanasoff conveyed by letter to John W. Mauchly in 1941. The ENIAC was initially planned by Mauchly and J. Presper Eckert, Jr., and was then developed, designed, and built by a group of engineers under their direction. Work on the ENIAC was carried out at the Moore School of Electrical Engineering of the University of Pennsylvania, where planning and initial development of the stored program computer were also to take place.

The ENIAC was the first general-purpose electronic computer, capable of solving a wide variety of problems in science, engineering, and number theory at a high rate of speed. Its accumulators could add 5000 numbers per second, and its multiplier could perform 400 multiplications per second. While these are not startling rates by today's standards, the ENIAC was roughly 1000 times faster than its closest competitor, the electromechanical Harvard Mark I.2 It was only about 100 times faster than the differential analyzer, but, being digital, it achieved much greater accuracy than the analog differential analyzer and could solve a much wider range of problems. As a consequence of its speed and power, it solved computational problems previously beyond the reach of man, thereby establishing the feasibility and value of electronic digital computation.

Although the ENIAC used electronics for computing, its method of programming was manual, an extension of the plug board. To enter instructions in the machine, operators set switches on the calculating units; and to sequence these instructions, they connected the units to one another by plugging cables into sockets. Such programming was, of course, laborious. While the ENIAC could compute the 30 second trajectory of a shell in 20 seconds, operators required 2 days to program it
 or to do so. It remained for the stored program computer, the product of the second major advance in computer technology, to alter programming in the same drastic manner in which the ENIAC had altered hardware." [Annals of the History of Computing,  Vol.3 #4 October 1981]