The Room Nobody Wanted Credit For
In the winter of 1945, inside a building at the University of Pennsylvania, six women crouched behind a machine the size of a small house. It weighed thirty tons. It had eighteen thousand vacuum tubes. And it had absolutely no instruction manual.
The women — Jean Jennings, Frances Bilas, Betty Snyder, Marlyn Wescoff, Ruth Lichterman, and Frances Spence — were given a stack of wiring diagrams, a set of logical problems, and a deadline tied to the war effort. Their job was to make ENIAC calculate ballistic trajectories. Nobody told them how. Nobody could. The machine had never been programmed before.
What nobody mentioned at the press conference afterward was that these women had already been doing something very much like this for years. They just called it operating a switchboard.
Routing Calls, Routing Logic
Before the digital age, the telephone network was the most complex live system most Americans ever interacted with. And the people who ran it — almost entirely women — weren't just plugging cables into holes. They were managing dynamic routing problems in real time, under pressure, with no margin for error.
A missed connection meant a dropped call. A wrong sequence could cascade into a regional outage. Operators had to hold multiple simultaneous pathways in their heads, anticipate bottlenecks, reroute on the fly, and do all of it in seconds while a subscriber was waiting on the line.
Sound familiar? It should. That's debugging. That's systems thinking. That's exactly what programming a machine like ENIAC required.
The women who would go on to code the first modern computers weren't recruited from mathematics departments or engineering schools — though some had math backgrounds. They were recruited from a pool of women who had proven they could manage logic under pressure. The government called them "computers" — a job title, not a machine — and they were paid accordingly. Less than men. Rarely credited. Almost never promoted.
What the Switchboard Actually Taught Them
Kay McNulty, one of the original ENIAC programmers, grew up in a small Irish-immigrant community in Pennsylvania. She'd studied math at Chestnut Hill College, but the skills that made her exceptional on ENIAC weren't purely academic. They were practical. Intuitive. Built from years of watching how systems failed and learning to catch the failure before it spread.
She later described programming ENIAC as "learning to talk to something that didn't speak your language yet." The machine had no operating system, no interface, no feedback loop that a modern programmer would recognize. You set it up physically — rerouting cables, adjusting switches — and then you waited to see if your logic held.
That's not so different from a switchboard operator listening for the click that tells her the line went through.
Frances Bilas Spence, another of the six, had worked as a "human computer" before the machine existed — doing the math by hand that the military needed for shell trajectories. She was methodical, precise, and completely unbothered by complexity. When ENIAC finally came online, she was one of the first people to understand intuitively why a calculation wasn't running correctly. She traced the problem through the machine's physical wiring the same way she would have traced a dropped call through a patch panel.
The Press Conference That Erased Them
On February 14, 1946, the Army unveiled ENIAC to the world. Reporters crowded into the demonstration room. Generals posed for photographs. The machine ran its first public calculation — a trajectory problem — and the room broke into applause.
The six women who had programmed it stood at the back. They weren't introduced. Several accounts suggest they weren't even mentioned. The narrative that emerged from that press conference centered on the hardware — the engineers who built the machine, the military officials who funded it. The software, and the people who wrote it, were invisible.
For decades, that's how the story stayed.
It wasn't until the 1980s and 1990s — largely through the research of historian Kathy Kleiman, who stumbled across archival photographs and began tracking down surviving programmers — that the full story started to come out. Kleiman found the women, interviewed them, and eventually helped produce a documentary called Top Secret Rosies that finally put their names on the record.
By then, most of them were in their seventies or eighties. Some had already died.
The Skill Set Nobody Named
Here's the part that gets overlooked in the rush to celebrate these women's mathematical talent: the telephone operator wasn't just a pipeline to programming. She was a model of it.
The Bell System, by the 1930s, had developed training programs for operators that were, in retrospect, remarkably similar to what we'd now call computational thinking. Operators learned to break complex routing problems into sequential steps. They learned to isolate variables — is it this line or that one? They learned to work within strict logical rules while still making judgment calls in ambiguous situations.
They were, in every meaningful sense, running algorithms. They just didn't have that word for it.
When the computing industry exploded in the 1950s and 1960s, the women who transitioned from telephone work to early programming roles didn't experience the shift as a leap. They experienced it as a translation. The logic was the same. The pressure was the same. The pay gap was, unfortunately, also the same.
What Got Lost
The erasure of these women from tech history had consequences that went far beyond fairness. It created a false origin story for computing — one that centered on hardware and male engineers, and left out the human systems thinking that made the hardware useful.
That story shaped how the industry recruited, who it valued, and what it rewarded. The skills that the ENIAC programmers brought — practical, intuitive, systems-level thinking built through experience rather than credentials — were precisely the skills that got coded out of the industry's self-image.
We ended up with a field that told itself a story about lone genius and technical purity, when the actual history was messier, more collaborative, and far more diverse than that story allowed.
The switchboard operators who became programmers didn't wait for permission. They didn't have a roadmap. They looked at a thirty-ton machine with no manual and figured it out, the same way they'd figured out every tangled routing problem before it.
That's not just a footnote to computing history. That's the whole point.