The Crew

When the Mark I was assembled at Harvard in 1944, a handful of Harvard civilians ran the first series of test problems, becoming its first operators. In the following months the Navy completed the crew with its own personnel to apply the computer’s powers to wartime problems. The machine’s inventor, Howard Aiken, who had enlisted in the Navy in 1941, was put back in charge with the rank of commander. A cadre of officers with advanced mathematical training, directed by two mathematics PhDs, programmed the machine. A group of enlisted men working around the clock in 8-hour shifts rounded out the team. These groups—the Harvard civilians, Navy officers, and enlisted men—formed the core team who had the monumental task of turning diverse mathematical problems into actual numerical results from a new machine about which most of them knew little.

The biggest hurdle was to translate mathematical problems into a set of clearly defined steps the machine could understand. This involved designing sequential instructions, strings of numbers, and custom wirings. The team referred to this process as the “coding” of a problem.

The coding pioneers of wartime Mark I went on to prominent positions in the computer industry of the postwar years.

The Cruft Laboratory (Oxford Street), where Mark I operated in the basement between 1944 and 1946. During the war, the building also housed the Pre-Radar Training Course for military officers and the Underwater Sound Laboratory.

Harvard University Archives

Mark I's wartime team, early 1945.

Officers on the second row: Ensign Richard Bloch, Lieutenant Commander Hubert Andrew Arnold, Commander Howard Aiken, Lieutenant Grace Hopper, Ensign Robert Campbell. The Harvard civilians in the back are technician Robert Hawkins, secretary Ruth Knowlton and Assistant Director of the Cruft Laboratory, David Wheatland.

The enlisted men are Seamen Livingston, Bissell, Calvin, White, and Verdonck.

Collection of Historical Scientific Instruments, Harvard University
Lieutenant Grace Murray Hopper, Ph.D. in Mathematics from Yale and professor at Vassar College. Enlisted in the Navy in 1943, she was assigned to the computation project as third in command becoming one of the four original "coders," the first computer programmers. After the War she was a central figure in the development of UNIVAC, the first commercial computer. In the 1950s she created the first compiler, the system that allows to program in plain English rather than numerical machine code, and co-developed the commercial computer language COBOL. Hopper continued a long career in the Navy, retiring in 1986 as a Rear Admiral.

Grace Murray Hopper Collection, Archives Center, National Museum of American History, Smithsonian Institution

Ensigns Robert Campbell, and Richard Bloch (facing the camera) at work in the coder's office.

Campbell was a PhD student in physics at Harvard in 1941, and he was the first "coder" of Mark I. After Aiken went to the Navy in 1941, he became the person supervising the construction of the machine at IBM. He supervised the transfer and set-up at Harvard before Aiken came back to direct the military project, at which point Campbell entered the Navy and was given a military rank. He helped in the design of Mark II, and after the War went to private industry, at Raytheon and Burroughs.

Robert Bloch was Mark I's second "coder". He joined the Navy in 1943 right after completing his undergraduate degree in Mathematics at Harvard. Originally assigned to the Naval Research Laboratory, Aiken transferred him to Harvard. Bloch was considered the main mathematical programmer of Mark I, and worked with outside users to formulate their projects for the machine. After the war he followed Campbell to Raytheon and later General Electric, where he headed their computer divisions.

Grace Murray Hopper Collection, Archives Center, National Museum of American History, Smithsonian Institution

The rank-and-file of Mark I's crew was constituted by enlisted men selected for their experience with calculating machines. They were referred to as "operators" and performed most of the physical tasks, such as punching the paper tapes with the numbers and instructions, as seen in the above photo. They also set the machine's switches, dialed in constants, fed the tape and punch card readers, and retrieved the printed output. In this photograph: Seaman Livingston.

Grace Murray Hopper Collection, Archives Center, National Museum of American History, Smithsonian Institution

Before the arrival of the Navy crew, Mark I was assembled and operated by Harvard University civilians from the Cruft Laboratory, who continued to work alongside the Navy crew throughout the War. Robert Hawkins (above) was the Cruft technician sent to IBM in Endicott, NY, to be trained in its construction, operation and maintenance. Back at Harvard, Hawkins became Mark I's technical wizard. After the war he remained at Harvard and participated in the construction of its successors Mark II, III and IV.

Collection of Historical Scientific Instruments, Harvard University

Ensign Ruth Brendel, a mathematician and later arrival to the team and third woman in the computation project, after Ruth Knowlton, the Cruft secretary who became an operator, and Lieutenant Grace Hopper. A mathematics instructor at the University of Buffalo, at 21 years old Brendel enlisted in the Navy the moment her age allowed. After the war, she returned to her university career in Buffalo.

Grace Murray Hopper Collection, Archives Center, National Museum of American History, Smithsonian Institution

A playful summary of the distribution of work in a wartime computation task directed by Grace Hopper. Problem L was the Bessel function tables project.

Grace Murray Hopper Collection, Archives Center, National Museum of American History, Smithsonian Institution

The inventors of Mark I: Frank E. Hamilton, Clair D. Lake, Howard H. Aiken and Benjamin M. Durfee.
After the War, Aiken became a Professor at Harvard, creating the Computation Laboratory, one of the first computer science programs in the country. He directed the construction of the machine's successors Mark II, III and IV for the Navy, in which IBM did not participate.
IBM Engineers Hamilton, Lake and Durfee, remained in Endicott. During the war they developed the smaller Pluggable Sequence Relay Calculator (PSRC) or "Aberdeen Machines" for calculating artillery trajectories, and later they participated in IBM's postwar computing project, the Selective Sequence Electronic Calculator (SSEC), built between 1945 and 1948.

Collection of Historical Scientific Instruments, Harvard University

Collection of Historical Scientific Instruments   © President and Fellows of Harvard College