The First True Computers

World War II stimulated computer development as military advantages could be gained through designing weapons according to more sophisticated ballistic calculations and deciphering the encoded communications of the opposing side. In the early 1930s, the U.S. Navy Board of Ordnance sponsored the American mathematician Howard Aiken, and in 1939, in collaboration with engineers at the International Business Machines Corporation (IBM), he was contracted by the Navy to develop a machine for ballistic calculations. Aiken’s electromechanical Automatic Sequence Controlled Calculator, also known as the Harvard Mark I, was completed in 1944 at a cost of $500,000. It was operated by a punched-tape program and weighed 5 tons.

In Britain, computer research efforts were concentrated on code breaking. Alan Turing, the British mathematician who in 1936 had formulated his vision of a “universal computing machine,” was one of the team that created the Colossus code-breaking machine. Colossus succeeded in breaking the supposedly impregnable German Enigma code, but, for obvious reasons, the project was kept top secret. The most influential of the computers developed in the course of military research was not completed until 1946. This was the Electronic Numerical Integrator and Calculator (ENIAC), commissioned by the U.S. Army Ordnance Department. ENIAC was built by a team at the University of Pennsylvania, led by John Presper Eckert and John William Mauchly. Drawing on Atanasoff and Berry’s design, ENIAC was the world’s first electronic computer. Weighing 30 tons and occupying 160 square meters (1,600 square feet) of floor space, it contained 19,000 thermionic valves, which acted as gates controlling the flow of electric current. Each calculation was programmed by operators feeding in punched cards, and the results were also presented on punched cards.

Feeding in punched cards was a slow and laborious process, so university scientists elsewhere began working on methods of internal program storage. In 1945, the eminent Hungarian-born American mathematician John Von Neumann outlined his theory of a stored-program computer with a central unit to control and process operations in sequence and with read-write random access memory. In Britain, teams at the Universities of Manchester and Cambridge were also addressing this issue. The Manchester team was led by Freddie Williams and Tom Kilburn and assisted by Alan Turing. In 1948, the Manchester electronic computer, known as the Small Scale Experimental Machine (SSEM) and nicknamed the Baby, ran the world’s first stored program, which was stored on cathode ray tubes. Von Neumann’s ideas first came to fruition in the Electronic Delay Storage Automatic Calculator (EDSAC), built at Cambridge University and operational from 1949. EDSAC used mercury delay line storage, a technology developed at the Massachusetts Institute of Technology. EDSAC was completed in advance of the Von Neumann computers developed in the United States, namely the Electronic Discrete Variable Computer (EDVAC) at the University of Pennsylvania and the MANIAC-1 computer at the Institute for Advanced Study at Princeton.