IBM dedicates Harvard Mark I, August 7, 1944

-August 07, 2017

On August 7, 1944, IBM dedicated the Automatic Sequence Controlled Calculator (ASCC), better known as the Harvard Mark I, to Harvard University.

Mark I was the largest electromechanical calculator ever built and the first automatic digital calculator in the United States at the time.


Mark I was the largest electromechanical calculator ever built. Source: IBM

As with many moments in tech history, the dedication was shadowed by disagreement. As the story goes, the machine was born out an idea for a large-scale digital calculator conceived by Howard H Aiken, a graduate student in theoretical physics at Harvard University, in 1930. IBM liked the idea and set its engineers to work on the device with Aiken during World War II .

By the time of dedication, IBM had spent approximately $200,000 on the project and donated an additional $100,000 to Harvard to cover the ASCC's operating expenses. It is said that prior to dedication, Aiken published a press release announcing the Mark I and listing himself as the sole inventor, only noting IBM’s James W Bryce in the release, despite IBM putting several other engineers, some of which were among IBM’s top talent at the time, on the project. Reports state that IBM CEO Thomas J Watson was enraged and only reluctantly attended the dedication ceremony and for a short time.

IBM's archives provide a description of the Mark I:

Consisting of 78 adding machines and calculators linked together, the ASCC had 765,000 parts, 3,300 relays, over 500 miles of wire and more than 175,000 connections. The Mark I was a parallel synchronous calculator that could perform table lookup and the four fundamental arithmetic operations, in any specified sequence, on numbers up to 23 decimal digits in length. It had 60 switch registers for constants, 72 storage counters for intermediate results, a central multiplying-dividing unit, functional counters for computing transcendental functions, and three interpolators for reading functions punched into perforated tape. Numerical input was in the form of punched cards, paper tape or manually set switches. The output was printed by electric typewriters or punched into cards. Sequencing of operations was accomplished by a perforated tape.

Mark I was used by the Navy to run repetitive calculations for the production of mathematical tables. It was operated at Harvard for 15 years.  It was eventually disassembled. A portion of the machine was sent to the Smithsonian Institution in Washington, DC, while other portions of the Mark I remain at Harvard in the Science Center as part of the Harvard Collection of Historical Scientific Instruments.

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Editor's note: This article was originally posted on August 7, 2012 and edited on August 7, 2017.

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