She was born Kathleen Rita McNulty in Feymore, part of the small village of Creeslough in what was then a Gaeltacht area (Irish-speaking region) of County Donegal in Ulster, the northern province in Ireland, on February 12, 1921, during the Irish War of Independence. She was the third of six children of James McNulty and Anne Nelis. On the night of her birth, her father, James McNulty, an Irish Republican Army training officer, was arrested and imprisoned in Derry Gaol for two years as he was a suspected member of the IRA. On his release, the family emigrated to the United States in October 1924 and settled in the Chestnut Hill section of Philadelphia, Pennsylvania where James found work as a stonemason. At the time, Antonelli was unable to speak any English, only Irish; she would remember prayers in Irish for the rest of her life.

In 1945, the Army was recruiting mathematicians from universities to aid in the war effort; despite a warning by her adviser that she would be just "a cog in a wheel" with the Army, and despite encouragement to become a mathematics teacher instead, Bartik known as Betty Jennings at the time decided to become a human computer. Her calculus professor, encouraged Bartik to take the job at University of Pennsylvania because they had a differential analyzer.

She applied to both IBM and the University of Pennsylvania at the age of 20. Although rejected by IBM, Jennings was hired by the University of Pennsylvania to work for Army Ordnance at Aberdeen Proving Ground, calculating ballistics trajectories by hand. While working there, Bartik met her husband, William Bartik, who was an engineer working on a Pentagon project at the University of Pennsylvania. They married in December 1946.

Holberton was born Frances Elizabeth Snyder in Philadelphia, Pennsylvania in 1917. Her father was John Amos Snyder, her mother was Frances J. Morrow and she was born as the third child in a family of 8 children.

Holberton studied journalism, because its curriculum let her travel far afield.Journalism was also one of the few fields open to women as a career in the 1940s. On her first day of classes at the University of Pennsylvania, Holberton's math professor asked her if she wouldn't be better off at home raising children.

During World War II while the Army needed to compute ballistics trajectories, many women were hired for this task. Holberton was hired by the Moore School of Engineering to work as a "computer" and chosen to be one of the six women to program the ENIAC.

Meltzer was born Marlyn Wescoff in Philadelphia and graduated from Temple University in 1942. She was hired by the Moore School of Engineering later that year to perform weather calculations, mainly because she knew how to operate an adding machine; in 1943, she was hired to perform calculations for ballistics trajectories. At the time this was accomplished by using manual desktop mechanical calculators. In 1945, she was selected to become one of the first group of ENIAC programmers.

She was born Frances V. Bilas in Philadelphia in 1922 and was the second of five sisters. Her parents both held jobs in the education sector, her father as an engineer for the Philadelphia Public School System and her mother as a teacher.

Bilas attended the South Philadelphia High School for Girls and graduated in 1938. She originally attended Temple University, but switched to Chestnut Hill College after being awarded a scholarship. She majored in mathematics with a minor in physics and graduated in 1942. While there, she met Kathleen Antonelli, who later also became an ENIAC programmer. In 1947, she married Homer W. Spence, an Army electrical engineer from the Aberdeen Proving Grounds who had been assigned to the ENIAC project and later became head of the Computer Research Branch. She had continued working on the ENIAC in the years after the war, but shortly after her marriage, she resigned to raise a family. She had three boys named Joseph, Richard, and William.

Teitelbaum was hired by the Moore School of Electrical Engineering at the University of Pennsylvania to compute ballistics trajectories. The Moore School was funded by the US Army during the Second World War. Here a group of about 80 women worked manually calculating ballistic trajectories - complex differential calculations.

Along with Marlyn Meltzer, Teitelbaum was part of a special area of the ENIAC project to calculate ballistic trajectory equations using analog technology. They taught themselves and others certain functions of the ENIAC and helped prepare the ballistics software. In 1946, the ENIAC computer was unveiled before the public and the press. The seven women were the only generation of programmers to program the ENIAC.