Harvard Mark I
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The IBM ASCC, the Automatic Sequence Controlled Calculator, called the Mark I by Harvard University, was the first large scale automatic digital computer in the USA.
The electromechanical ASCC was devised by Howard H. Aiken, created at IBM, shipped to Harvard in February 1944, and formally delivered there on August 7, 1944.
The building elements of the ASCC were switches, relays, rotating shafts, and clutches. It was built using 765,000 components and hundreds of miles of wire, amounting to a size of 51 feet in length, eight feet (2.4 meters) in height, and two feet deep. It had a weight of about five short tons (4500 kilograms). The basic calculating units had to be sychronized mechanically, so they were run by a fifty-foot shaft driven by a five-horsepower electric motor. The Mark I could store 72 numbers. It could do three additions or subtractions in a second. A multiplication took six seconds and a logarithm or a trigometric function took over one minute.
The Mark I read its instructions from a punched paper tape and executed the current instruction and then read in the next one. It had no conditional branch instruction. This meant that complex programs had to be physically long. A loop was accomplished by joining the end of the paper tape containing the program back to the beginning of the tape.
The main advantage of the Mark I was that it was fully automatic – it didn't need any human intervention once it started. It was the first fully automatic computer to be completed.
See also
- History of computing hardware
- Other early computers:
References
- Computer: A History of the Information Machine,Martin Campbell-Kelly and William Aspray, 1996, Basic Books, ISBN 0-465-02989-2.
External links
- IBMs ASCC Reference Room (http://www-1.ibm.com/ibm/history/exhibits/markI/markI_reference.html)
- ASCC operational manual (http://www.bitsavers.org/pdf/harvard/MarkI_operMan_1946.pdf) (PDF)de:Automatic Sequence Controlled Calculator