Milestones:Harvard Mark 1 Computer, 1944 - 1959

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Cambridge, MA
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Harvard Mark 1 Computer, 1944-1959


The Mark I computer was a general-purpose electro-mechanical computer that could execute long computations automatically. It was conceived by Harvard University's Dr. Howard Aiken, and built by International Business Machines Corporation in New York. The machine used mechanical punch-card tabulating equipment. Considered the first large-scale electro-mechanical computer, it was a leap forward in modern computing.

Street address(es) and GPS coordinates of the Milestone Plaque Sites

42.3763452, -71.1166043 Harvard School of Engineering and Applied Science, 1 Oxford Street Cambridge MA 02138

Details of the physical location of the plaque

Inside the lobby of Harvard Science Center (1 Oxford Street), Cambridge MA, in proximity to the historical display that features significant components from the original Mark I.

How the intended plaque site is protected/secured

The Harvard school lobby is generally opened to the public.

Historical significance of the work

The IEEE should award this milestone to the Mark 1 Computer, the name used by the Operator, Harvard University, Howard Aiken, Grace Hopper,and others for nearly 15 years. The designation preferred by some was 'IBM Automatic Sequence Controlled Calculator (ASCC)' but this name was a temporary one, more like a shop name. Since the computing machine was the brainchild of Howard Aiken, naming rights belong to him. Aiken envisioned other computers, like a Mark II and a Mark III.

The computer was housed in a steel frame 51 feet (16 m) long and eight feet high. It consisted of an interlocking panel of small gears, mechanical counters, switches and control circuits, all only a few inches in depth. It was connected with 500 miles (800 km) of wire with three million connections, 3,500 multipole relays with 35,000 contacts, 2,225 counters, 1,464 tenpole switches and tiers of 72 adding machines, each with 23 significant numbers. And that was the world's largest electromechanical calculator.

The Mark I was not dead-end technology but encouraged Aiken to develop the Mark II and later the Mark III. See Wikipedia for details. Google Grace Hopper for historical information and photographs.

Features that set this work apart from similar achievements

The history and evolution of computers is long and complicated. How the Mark 1 fits in the scheme of things is beyond the scope of this document. The Mark I computer had many features that are stated elsewhere in the literature. As a starting point, refer to IEEE GHN #1 and #2 and Wikipedia #3.

Significant references

1 IEEE GHN Biography of Howard Aiken,

2 IEEE GHN Harvard Mark I

3 Wikipedia

4 Cohen, Bernard (2000). Howard Aiken, Portrait of a computer pioneer. Cambridge, Massachusetts: The MIT Press.

5 Aiken, Howard H. and Grace M. Hopper, "The Automatic Sequence Controlled Calculator", Electrical Engineering, Vol.65 No.8-9, pp.384-391 (Aug 1946); No.10, pp.449-454 (Oct 1946); No.11, pp.522-528 (Nov 1946).

6 Harvard Computation Laboratory, A Manual of Operation for the Automatic Sequence Controlled Calculator, The Annals of the Computation Laboratory of Harvard University, Vol.1, Harvard University Press (1946), 561pp.

7. Priceless construction photographs of the Mark 1 computer being unloaded in pieces then assembled in place by IBM. Photos appear to have been taken by IBM in 1944.,/is/,/14343/,/false/,/true

8. Time Magazine cover issue of 23 January 1950 shows the Mark II and Mark II.

Supporting materials

Historical photographs and historical information on IBM's collaboration are given by Frank da Cruz on his website: - sources

A priceless image of the team working on Mark I is attached. Its been copied from www.

Grace Murray Hopper (seated second from right) and Howard Aiken (seated center) along with other members of the Bureau of Ordinance Project. Photo taken in front of Mark 1.


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