In the early twentieth century, electrical power networks were some of the most complex engineering systems in use. In order to predict the performance of these systems, Vannevar Bush and his associates at the Massachusetts Institute of Technology developed several analog computing devices. One of these, the differential analyzer, was sufficiently successful that copies were built at a few laboratories. At the outbreak of World War II, the U.S. armed forces contracted to use differential analyzers at MIT and at the Moore School of Electrical Enginnering of the University of Pennsylvania. The machines were used to calculate firing tables for new artillery. Differential analyzers alone could not do the job; the government also hired people (whose job title was "computer") to calculate tables using mechanical desk calculators.
John W. Mauchly, a physicist with a doctorate from Johns Hopkins University who had taught at Ursinus College, went to work at the Moore School when war broke out. He believed that much faster computing devices were needed than the analog differential analyzer or the digital computers that used relays. He envisioned a computer that used vacuum tubes and other electronic parts. Others had thought about building electronic computing devices. The mathematical physicist J.V. Atanasoff ofIowa State University, assisted by Clifford Berry, tried to build such a machine before the war. Mauchly had visited Atanasoff and discussed his plans with him. The influence of Atanasoff on Mauchly is a matter of dispute.
Mauchly first proposed building an electronic computing device in August, 1942. By the following spring, the U.S. Army was falling far behind in providing the firing tables needed for new artillery. That June, Mauchly, the electrical engineer J. Presper Eckert, and a team at the Moore school received the funds needed to begin the ENIAC (Electronic Numerical Integrator and Computer).
The ENIAC was the first successful general purpose electronic computer. The ENIAC initially did not store its programs in its internal memory, but it could carry out operations at electronic speeds. Operators set the machine to solve problems by plugging in cables and setting switches--in effect, rewiring the machine for each new problem to be solved. Punched card equipment handled input and output of numbers, but while the machine was actually solving a problem these were not used, because they could not operate fast enough.
The ENIAC was big. It weighed 30 tons and took up 1800
square feet of floor space. The entire machine contained over
17,000 vacuum tubes, 70,000 resistors, 10,000 capacitors and
6,000 manual switches. It cost almost $500,000, and required six
full-time technicians to keep it running.
The ENIAC was completed in December, 1945, after World War II had ended. Its first calculations were used in the design of atomic weapons and in ballistics work. It was used for many other applications, including the first numerical weather prediction by computer. In the fall of 1947, engineers disassembled the ENIAC and moved it from the University of Pennsylvania to the Army's Aberdeen Proving Ground in Aberdeen, Maryland. The installation at Aberdeen is shown in the photograph. Portions of the ENIAC were given to the Smithsonian in the early 1960s.
References: Anonymous (1953), NMAH Collections, Stern, Williams.
