This dynamic has been at work in the development of the first programmable digital computer in the United States, the digital integrator and computer, Eniac, in the 1940s. Funded by the military, it was about A mastodon weighing more than 30 tons and including 17,468 vacuum tubes. The mere fact of putting him to work was seen as a heroic and virile feat of engineering. On the other hand, the programming appeared to him minimal, even of secretariat. Women worked for a long time in the calculations. In the years leading up to Eniac, many companies have bought huge electronic tab machines – very useful for collecting payroll, for example – from companies like IBM; women often worked as punch card operators for these overgrown calculators. When the time came to hire technicians to draft instructions for Eniac, it made sense for the men in charge to choose an all-female team: Kathleen McNulty, Jean Jennings, Betty Snyder, Marlyn Wescoff, Frances Bilas and Ruth Lichterman. The men would find out what they wanted Eniac to do; women have "programmed" to execute the instructions.

"We could diagnose problems almost up to the individual vacuum tube," Jennings later told an interviewer for the IEEE Annals of History of Computing. Jennings, who grew up as a missed girl of low-income parents near a community of 104 people in Missouri, studied mathematics at the university. "Since we knew both the application and the machine, we learned to diagnose problems as well as, if not better, than the engineer."

Eniac women were among the first programmers to discover that software never worked properly the first time – and that the programmer's main job was actually looking for and fixing bugs. Their innovations include some of the basic concepts of the software. Betty Snyder realized that if you wanted to debug a program that was not working properly, it would be helpful to have a "break point", a time when you could stop a program in the middle of its execution. To date, stopping points are a key part of the debugging process.

In 1946, the creators of Eniac wanted to show the computer to a group of leaders in the fields of science, technology and the military. They asked Jennings and Snyder to write a program calculating the trajectory of the missiles. After weeks of intense efforts, their team and themselves had a work program, with the exception of a technical problem: it was supposed to stop when the missile landed, but for some reason, it continued to work. The night before the demo, Snyder suddenly had the intuition of the problem. She went to work early the next day, toppled a single switch inside Eniac and eliminated the virus. "Betty could make more logical reasoning during her sleep than most people can do," Jennings said later. Nevertheless, women had little credit for their work. At this first official event to show Eniac, male project managers did not mention, let alone show women.

After the war, while coder jobs ranged from the military to the private sector, women remained at the forefront of coding and did some of the most prominent work. The pioneer of programs, Grace Hopper, often created the first "compiler", a program that allows users to create programming languages ​​closer to written words: an encoder could write English type code, and the compiler would work to turn it into ones and zeros for the computer. Hopper has also developed the "Flowmatic" language for non-technical businessmen. Later, she advised the team that created the Cobol language, widely used by companies. Another programmer on the team, Jean E. Sammet, continued to influence language development for decades. Fran Allen was so expert in optimizing Fortran, a popular language for performing scientific calculations, that she became the first IBM woman.

When the number of coding tasks exploded in the fifties and sixties, as companies began to rely on software to process the payroll and process the data, men had no particular advantage to be hired. As Wilkes had discovered, employers were simply looking for logical, good math candidates and meticulous candidates. And in this respect, sexist stereotypes have worked in favor of women: some leaders have argued that women's traditional skills in tedious activities such as knitting and weaving were a clear reflection of this state of mind. (The 1968 book "Your Career in Computers" indicates that people who like to "cook from a cookbook" are good programmers.)

The field was rewarded with his skills: candidates were often presented with a test (usually a type of pattern recognition), were hired if they were successful and were trained on the job, a process that made the field particularly receptive to neophytes. "Do not know anything about computers? Then we'll teach you (and pay you at the same time), "promised a British ad in 1965. In a US recruiting campaign in 1957, the IBM booklet," My Beautiful Ladies, "specifically encouraged women to apply for positions as coders.