Tech Innovation

How Female ENIAC Programmers Pioneered the Software Industry

ENIAC women programmers

As American women stepped up to support the war effort during WWII, a top-secret Army program picked six female mathematicians to code instructions for ENIAC, the first all-electronic digital computer. Their programming work launched a modern software industry.

When Betty “Jean” (Jennings) Bartik earned her degree in math from a rural Missouri college during WWII, her academic advisor suggested she become a schoolteacher, noting the impact she could have in a small community.

Instead, Bartik, who’d watched the men of her generation head overseas to fight, craved adventure herself. She landed a job in Philadelphia as a human computer and soon joined a select group of female mathematicians hired to calculate weapons trajectories to aid the war effort.

There, she and five other women went on to write instructions for the world’s first all-electronic, programmable computer. It launched the modern software industry and, ultimately, changed the world.

Until recently, however, these women were all but forgotten.

female ENIAC programmers
Betty “Jean” Jennings Bartik (left), Marlyn Wescoff Meltzer (center) and Ruth Lichterman Teitelbaum (right). Courtesy of the University of Pennsylvania Archives.

“The women of ENIAC were true pioneers,” said Kathy Kleiman, an attorney specializing in internet law and policy for the D.C.-based firm Fletcher, Heald & Hildreth, as well as founder of the ENIAC Programmers Project.

“They came from a range of backgrounds to become college graduates, an achievement in itself,” she said. “At a time when college-educated women had few employment options other than teaching, they went on to program the first electronic computer and kick off the Information Age.”

Programming the ENIAC

Between 1942 and 1945, the Army recruited approximately 100 female computers to calculate ballistic trajectories by performing a complex series of differential calculus equations.

These female Electronic Numerical Integrator and Computer (ENIAC) programmers solved the equations by taking into account a variety of factors, including barometric pressure, humidity and even the rotation of the Earth.

“Each firing table had about a thousand trajectories,” Bartik once explained. “It took about 30 to 40 hours to do one by hand.”

But even with human computers working six days a week on the project, there were thousands of calculations to complete and, given the urgency of war, insufficient time. To speed up the process, the Army backed a top secret project led by two Moore School instructors, physicist Dr. John Mauchly and engineer J. Presper Eckert: building the Electronic Numerical Integrator and Computer (ENIAC).

Women ENIAC programmers
Betty “Jean” Jennings Bartik (left) and Frances “Fran” Bilas Spence. Courtesy of the University of Pennsylvania Archives.

The ENIAC was a black steel behemoth that stretched 80 feet long, rose eight feet high and weighed 30 tons. It took up three sides of a gargantuan room and included 18,000 vacuum tubes, hundreds of cables and 3,000 switches.

In theory, the ENIAC would automate the calculation process and turn out ballistic tables a thousand times faster than humans. But first, it needed to be programmed.

The Army selected Bartik, Betty (Snyder) Holberton, Marlyn (Wescoff) Meltzer, Ruth (Lichterman) Teitelbaum, Kay (McNulty) Mauchly Antonelli, and Frances “Fran” (Bilas) Spence for the job.

There were no manuals for the ENIAC, no user’s guide, no operating systems or computer languages. The women weren’t even allowed access to the machine before their security clearance was approved. Until then, they were simply given wiring diagrams of the machine’s 40 panels.

female ENIAC programmers
Photo taken at unveiling of the ENIAC in February, 1946. Courtesy of the University of Pennsylvania Archives.

“We learned, you might say, from the back forward,” Antonelli said in an interview years later. ”We learned all about the tubes first and then came around and found out what the front did.”

Bartik, who co-led the team along with Holberton, said it was a huge challenge to program.

But they did it. With their hands finally on the hardware, they employed human logic to break down the differential calculus equation into steps the computer could handle.

The ENIAC was essentially a collection of electronic arithmetic machines capable of performing a variety of mathematical functions. These units were controlled by a web of electrical cables and programmed by a combination of plug-board wiring and three portable function tables, each with 1,200 10-way switches used for entering tables of numbers. By manipulating the cables and switches, the female ENIAC programmers could instruct the computer to work its way, step by step, through differential equations.

Though the ENIAC was not finished in time for the end of the war, it was clear the lightning-fast machine held enormous potential for other applications. In 1945, it was used to help solve a problem coming in from Los Alamos, which some believe was the trigger to the hydrogen bomb.

Just months after the war ended, in February, 1946, the Army unveiled ENIAC to the press and the public.

In a dramatic display, with lights turned off to emphasize the flashing lights on the accumulators, the ENIAC calculated the whole trajectory of a missile – taking into account variables such as distance, wind and temperature – in just 20 seconds, not only thousands of times faster than a human could perform the calculations by hand, but also in less time than it would take for the projectile to leave the muzzle of the gun and hit its target.

Mauchly and Eckert were catapulted to fame and whisked off to celebrations in their honor.

The female ENIAC programmers, however, were rarely mentioned for the next 40 years.

Out of the Margins

In the mid-1980s, when Kleiman was an undergraduate at Harvard, she observed a dwindling number of women in her computer science classes and an absence of female faculty in the department. In search of role models, she looked to history where two figures quickly surfaced: Ada Lovelace from the 19th century, and Captain (later Rear Admiral) Grace Hopper from the 20th.

“What that told me was one woman per century could succeed in computer science,” said Kleiman, who found the idea untenable.

female ENIAC programmers
Courtesy of the University of Pennsylvania Archives

As she continued her research, she came across photos of the 1946 ENIAC press coverage, which included – in addition to Mauchly and Eckert, who were mentioned in the caption – several unidentified women.

Curious, Kleiman approached a computer historian. He told her the women in the photo were likely “refrigerator ladies,” that is, models who were posed in front of appliances of the era. Kleiman wasn’t convinced.

“In photo after photo, the women were interacting with the ENIAC, manipulating cables and switches,” she said. “It looked like they knew what they were doing.”

More digging led Kleiman to a single paragraph in an autobiography by a man who once supervised the ENIAC women. That’s when Kleiman found names for the women in the photos, giving her enough information to track them down.

In 1986, Kleiman attended the 40th anniversary of the ENIAC group, where she finally met her role models in person and began the process of recording and sharing their stories, first by collaborating on an article with Wall Street Journal reporter Thomas Petzinger, Jr., and later, co-producing the documentary, The Computers: The Remarkable Story of the ENIAC Programmers.

In the process, she discovered that some of the women continued to make significant contributions to the computer industry even after the war.

Bartik led the team that converted the ENIAC into one of the world’s first stored-program computers. She also made contributions to the early BINAC and UNIVAC 1 computers.

Holberton achieved a series of “firsts” in computing, Kleiman said, including developing the first construction code, the first sort routine and the first software application. She was also responsible for an aesthetic shift in early computers, as she never wanted to see another black computer after facing the monstrous ENIAC.

As the true story of the ENIAC Six spread, other accolades followed.

In 1997, all six women were inducted into the Women in Technology International Hall of Fame. That same year, Holberton received an Ada Lovelace Award from the Association of Women in Computing and the Institute of Electrical and Electronics Engineers (IEEE) Computer Pioneer Award. In 2008, Bartik was made a Fellow of the Computer History Museum.

Additionally, the women of ENIAC have become role models for countless women and girls interested in pursuing careers in technical fields.

Adelaide Rhodes, a marine zoologist and bioinformaticist at the Center for Genome Research and Biocomputing at Oregon State University, was inspired by the women ENIAC programmers.

“The fact that they were not seen or recognized does not mean that they were not an important part of the process,” Rhodes said. She relates to the ENIAC women’s stories because she doesn’t let a lack of recognition hold her back from working on and completing complex projects.

Kleiman added that while women are still a minority in the industry, there’s hope for a more diverse future.

“The idea that the field of software and programming was created by women is one that gives all of us a little bit of extra energy and a little bit of extra confidence in the work that we do,” Kleiman said.

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