Remembering the Eniac Six

Eniac Ventures
3 min readMar 30, 2023

by Regan Gore

The Electronic Numerical Integrator and Computer — the world’s first non-mechanical, general-purpose computer — was unveiled at the University of Pennsylvania’s Moore School of Electrical Engineering on February 15, 1946.

John Mauchly and John Presper Eckert, the hardware engineers who designed the computer (known as ENIAC), have been justly celebrated as technology pioneers. Much less well known are the six women who programmed ENIAC and truly brought it to life: Betty Holberton, Jean Jennings Bartik, Kay McNulty, Marlyn Wescoff Meltzer, Ruth Lichterman, and Frances Bilas Spencer.

The “ENIAC Six” were selected for the job after working alongside more than 80 other women at Moore as “computers,” manually calculating ballistic trajectories with differential equations for the US Army during World War II. At the time, mathematical computing was considered “too tedious” for male engineers, so women were tasked with solving these complex equations (which could take more than 40 hours per equation).

When the six women started working on ENIAC, the US Army did not initially grant them security clearance, so they were not allowed to see the hardware; they had to program the computer based solely on blueprints of the device and interviews with the engineers. The group was not even given a space to work together, instead using abandoned classrooms and Penn fraternity houses to do their work.

When the time came to reveal ENIAC’s capabilities to the public, that first demonstration was led by two of the Eniac Six, Marlyn Wescoff and Ruth Lichterman. That’s who you see in those iconic ENIAC photos, like the one above. But none of the women were invited to the celebratory dinner afterwards, and as the years passed, when computer historians were asked about the photos, some suggested that Marlyn and Ruth were only models.

They did so much more than that: These are the women who developed the logic behind ENIAC’s programming, creating subroutines, nesting, and other programming techniques still used today. They successfully wired the machine to perform specific tasks crucial to the Army, setting each switch and tube to properly perform the card-punch computations. They even crawled inside the machine itself to debug it.

After ENIAC was complete, they were tasked with creating the ENIAC programming manual, teaching the next generation of programmers, and developing programs for new problems and use cases for the computer at Aberdeen Proving Ground. Until it was decommissioned in 1955, ENIAC was used in the nuclear fission calculations and weather simulations required to create the hydrogen bomb.

After programming ENIAC, Betty continued to work with Mauchly and Eckert to help develop the UNIVAC, BINAC, Cobol, and Fortran. Jean contributed to BINAC as well, and is also credited with leading the group at Penn that worked out how to use ENIAC as a stored program machine. Decades later, the ENIAC Six were finally recognized in books, short films, and articles. In 1997, Betty, Jean, Marlyn, Ruth, Frances, and Kathleen were inducted into the Women in Technology International Hall of Fame.

Eniac Ventures is, of course, named after that first ENIAC computer, and the two conference rooms in our New York office are named after Betty Snyder and Jean Jennings. Founded by four Penn alums, we invest in companies that we believe continue ENIAC’s legacy of innovation.

Today, with Women’s History Month drawing to a close, we wanted to acknowledge the women who are such a crucial part of that legacy.



Eniac Ventures

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