Harvard Mark I

The Harvard Mark I, or IBM Automatic Sequence Controlled Calculator (ASCC), was one of the earliest general-purpose electromechanical computers. It helped with important work near the end of World War II.

One of the first jobs for the Mark I started on 29 March 1944. It was done by John von Neumann, who was working on the Manhattan Project. He needed to see if a certain way could work for a very important bomb.

The Mark I also did math work, like making tables. This was something Charles Babbage had wanted to do with his machine in 1837.

People who worked with the Mark I sometimes called it “Bessy.” This was after a kind of math used on the machine.

The Mark I was taken apart in 1959. Some parts went to IBM. Some went to the Smithsonian Institution, and some went to the Harvard Collection of Historical Scientific Instruments. For many years, Harvard’s part was shown in a building at Harvard. In about 1997, it was moved to the Harvard Science Center. In 2021, it was moved again to a new building at Harvard in Allston, Massachusetts.

Origins

The Harvard Mark I started as an idea in 1935 by Howard Aiken, a student at Harvard University. He wanted to build a machine that could solve hard math problems on its own. He shared his idea with IBM, and they agreed to help build it. Work began in 1939.

Because of World War II, Aiken had to stop the project for a time, but IBM kept working on it. The machine was finished in early 1943 and sent to Harvard in 1944. It was used to help the US Navy with calculations and was an important step in the history of computers. The Mark I used many ideas from Charles Babbage’s Analytical Engine and added new features too.

Design and construction

The Harvard Mark I, also called the IBM Automatic Sequence Controlled Calculator, was made from switches, relays, rotating shafts, and clutches. It had many parts and used lots of wire. The machine was very big — about 51 feet long, 8 feet high, and 2 feet deep.

It used a long drive shaft and an electric motor to help it do calculations. The Mark I was built by IBM for Dr. Howard Aiken at Harvard University. An industrial designer named Norman Bel Geddes designed its outer case.

Operation

The Harvard Mark I could store 72 big numbers and do simple math fast. It read steps from special paper tapes and did them one by one.

At first, people had to guide the machine step by step. Later changes let it work more on its own. Some of the first people to use this machine became important in computer science.

Instruction format

The Harvard Mark I used special tapes to control its work. These tapes had 24 channels split into three groups of eight. Each group held important information: the first group told the machine where to store the result, the second group told it what numbers to use, and the third group told it what operation to do. All these instructions were written in binary code, a simple system of zeros and ones.

Contribution to the Manhattan Project

John von Neumann helped with important math for the Manhattan Project. In 1944, he brought two mathematicians to Harvard. They used the Harvard Mark I computer to study how to make the first atomic bomb work better.

The Mark I made these calculations more precise. It could handle many more decimal places, helping scientists get better results for their work. Von Neumann thought this design would be very useful for future atomic bombs.

Aiken and IBM

Howard Aiken announced the Mark I and said he was the only inventor. He thanked one IBM engineer, James W. Bryce, but many others helped build it too. This made IBM chairman Thomas J. Watson unhappy. He went to the machine's dedication ceremony on August 7, 1944, but he did not want to. Because of this, Aiken decided to build later machines without IBM. The machine was called the "Harvard Mark I". Later, IBM made its own Selective Sequence Electronic Calculator to try new ideas and show its work.

Successors

The Harvard Mark I was followed by several more machines. The Harvard Mark II came next in 1947 or 1948, improving on the Mark I but still using electromechanical relays. The Mark III/ADEC in 1949 used mostly electronic components like vacuum tubes and crystal diodes, but it still had some mechanical parts, such as rotating magnetic drums for storage. The Harvard Mark IV in 1952 was completely electronic, using magnetic-core memory instead of mechanical parts.

The Mark II and Mark III were given to the US Navy base at Dahlgren, Virginia, while the Mark IV was built for the US Air Force but stayed at Harvard. The original Mark I was taken apart in 1959, and parts of it are now on display in the Science Center at the Harvard Collection of Historical Scientific Instruments. In July 2021, it was moved to the new Science and Engineering Complex in Allston. Some pieces of the original machine are at IBM and the Smithsonian Institution.