Howard Aiken and the Harvard Mark I
Written by Historian   
Saturday, 19 January 2013
Article Index
Howard Aiken and the Harvard Mark I
The War Years
Mark II and beyond

Mark I in the Navy

After his adventures Aiken was put in charge of the Mark I which was also drafted into the navy. Aiken joked that he was the first person to be commanding officer of a computer. Under naval control the Mark I was run as a military machine. Its operators would march around the highly polished floor and salute each other when ever it was required by protocol! According to one Harvard scientist who saw it in action its attendants "appeared to operate the thing while at attention!"

The Mark I could add or subtract three numbers every second - giving it an equivalent clock rate of 0.33Hz! The machine was slow but it was a real computer. In operation it may have sounded like the noise of a roomful of old ladies knitting with steel needles - but it was a fully programmable computer.

Grace Hopper, the inventor of the Cobol language, was just one of the many programmers who learned their craft on the Mark I. Fred Brooks, one of the important people involved in the IBM 360 project, also learned his craft with Aiken and the Mark I. Indeed the people who made the Mark I do its stuff were probably the first modern programmers. They spent most of their time calculating mathematical tables but they also invented the idea of the subroutine and the subroutine library.

The machine spent so long computing Bessel functions that its nickname among the programmers was "Bessy". It also received lots of publicity and was the first machine to stimulate the use of the term "electronic brain" in the popular press. Glossy magazines carried its picture and it became a symbol of the advance of science and technology.

To you and me this machine seems so slow as to be unusable. It also had competition from pure electronic machines such as ENIAC soon after it was completed - but it still worked a 24 hour day for 15 years at Harvard! When asked why he did not use electronic components Aiken responded that he thought that they would be too unreliable and it was better to have a slow machine that worked rather than a fast machine that didn't.

Marks II, III and IV

The Mark II was started in 1945 and it too used relays. It was three times the size of the Mark I and could handle 100 ten digit numbers at ten times the speed of the Mark I. Still you can't help being amazed that they were still building electromechanical computers at this late stage!



The Mark III


The Mark III, also built at the Naval Surface Weapons Center at Dahlgren, Virginia was finished in 1951 and the Mark IV in 1952 and both used novel electronic components - such as magnetic core shift registers.

The Mark IV

Aiken's later career

In 1946 Aiken was allowed to return to full time work at Harvard. In 1947 he was made director of the new Computation Laboratory - a post he held until 1961. In that time he fostered a great deal of fundamental work in computer science - mathematical linguistics, automatic translation, switching theory and the use of core memory and drums were all pioneered at Harvard. He was the editor of the Annals of the Computation Laboratory and wrote a number of books on switching theory.

He retired from the Compuational Laboratory to, in his words, "make money". Could this have been another late change of mind concerning his career! He set up Howard Aiken Industries and sold his knowledge as a consultant. Strangely for a man trying to make money he never liked patents and trying to prove who had invented something.

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