The programmer whose code underpins the Internet

Sharla Boehm earned a teaching degree from the University of California, Los Angeles, before she channeled her talent for math into computer programming. While working at the RAND Corporation, she built a groundbreaking simulation, originally conceived to strengthen military communications during the cold war. The simulation—and her work—would ultimately lay the foundation for the modern Internet. LISTEN TO THE PODCASTOn supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.TRANSCRIPTArchival: What if a warning siren sounds? What should you do? Don’t hesitate. Find cover.Katie Hafner: In the early 1960s, the United States and the Soviet Union were in a treacherous standoff. Each side was on high alert, with a growing stockpile of nuclear weapons — ready to launch at the first sign of an attack.U.S. authorities weren’t just worried about how to weather an initial attack. They worried about how they would mount a counterattack if a bomb knocked out communications.After all, these fragile systems were highly vulnerable to nuclear attack. If one bomb hit just right, all military communications could go down, leaving the entire country essentially defenseless.So, the U.S. military put scientists to work. Their charge: to invent a communications network that could survive an attack. And on the team was one scientist who created an ingenious computer simulation — using 1960s-era computers.Doug Rosenberg: As a piece of programming, it’s just unthinkable that she could do what she did. I mean, beyond comprehension.Katie Hafner: And then, she would all but disappear into history as soon as her work was done.Katie Hafner: This is Lost Women of Science. I’m Katie Hafner. And today we have the story of Sharla Perrine Boehm, a brilliant computer programmer — and so much more.The simulation she created in the early 1960s wouldn’t just be offered up as a way to safeguard U.S. communications in the event of a nuclear attack… It was so ingenious that later, long after she left the field, her work would help bring about one of the most world-changing inventions ever: the internet.

But before we start, a mea culpa from me. In 1996, my book, Where Wizards Stay Up Late: The Origins Of The Internet, was published. It's a definitive history of the Arpanet, the network that would eventually evolve into the internet. And I never once mentioned Sharla — never even came across her name. Actually, that can’t be true. She co-authored a major paper, a paper I must have seen, and yet I never thought to ask, “Who is that?” It was always the famous man, her colleague Paul Baran, that I focused on.And so, I want to make up for that today. And since I’m clearly not the expert when it comes to Sharla Perrine Boehm, I’ve brought in our producer Samia Bouzid to tell us Sharla’s story.Samia Bouzid: On the night of November 24, 1961, it seemed like the nation’s worst nightmare had come to pass. The ballistic missile early warning systems across the U.S. went dead all at once. At a base in Omaha, officers on overnight duty tried to call communications headquarters in Colorado Springs — but the phone lines were dead too. That could mean one of two things: Either there had been some inexplicably vast communications failure, or the U.S. was under attack.The officers scrambled to wake up General Thomas Power, the commander in chief of the Strategic Air Command, who immediately ordered nuclear forces on full alert. In the dark, bomber crews guided their planes onto runways. The U.S. was ready to strike.But minutes later, the Strategic Air Command finally made contact with communications headquarters, by sending radar messages through a bomber that was already in the air. And headquarters reported that there was no attack. It was just a regular, quiet night.So what happened? It turned out that a single motor at a relay station out in Colorado overheated and caused the entire system outage. It just happened to be the one relay station that all communications passed through.So here was the United States, one command away from an accidental nuclear war… all because of some janky phone circuits. Clearly, something had to be done.Paul Baran: This was the height of the Cold War.

Samia Bouzid: This is the computer scientist Paul Baran, speaking in an oral history recorded by the Charles Babbage Institute in 1990.Paul Baran: And it was a very dangerous situation because there's no communications that can survive an attack.Samia Bouzid: At the time of that nearly fateful outage, he was working at the RAND Corporation, a prominent research institute in Santa Monica, California. Baran and others at RAND were working on national security issues, including what to do about its disastrously fragile communications system.The problem boiled down to this: back in the early 1960s, military communications mostly happened over phone lines and shortwave radio. The circuits that transmitted these communications were centralized. That meant every message got routed through at most five nodes, or connecting points. If those nodes took a hit, there was no other path. The entire network went down.And so Baran became convinced that the solution was to create a new form of communication. Not with phones or radio. One that sent messages through computers. And he was already envisioning a network that could survive a catastrophic accident or attack.[Paul Baran speaking in background]Basically, set up a network without any central node. Each node is just connected to its neighbors. And then, make sure it's connected to enough neighbors that even if some get knocked out, the network as a whole will still survive.Unfortunately, selling his colleagues on the idea wasn't so simple. They were mostly experts in old-school analog communications, not digital computers. And they weren’t especially interested in hearing from the rogue computer scientist who had wandered into their turf.Paul Baran: They'd get a little huffy about it because, uh, “What the hell is this guy in computer science talking about communications?” People who had a background in analog communication did not understand digital processing. So, some of the things one would say would sound like utter nonsense.And Baran couldn’t stamp out their doubts. Every time he put one concern to rest, someone would raise another.And his colleagues at RAND were just one problem. Some of his biggest detractors were also some of the most important people he had to convince: the managers of AT&T.AT&T controlled everything to do with long distance communication, and so Baran really wanted to get them on board.

Paul Baran: The whole idea at the time was that we had hoped that AT&T would do this with the Air Force, cause AT&T had the monopoly.Samia Bouzid: But when Paul Baran pitched his idea to the company, the response was a mix of skepticism and condescension. He never forgot how a room of AT&T engineers reacted when he tried to describe how his idea would work.Paul Baran: “Wait a minute, son. You mean you open the switch here before the traffic has left the other end of the country?” I said, “Yeah.” And they look at each other, shake their heads and say, “Son, this is how a telephone works,” and it got pretty patronizing.Samia Bouzid: No matter what he said, it just wasn’t enough to win over his colleagues, let alone the AT&T guys.They just struggled to fathom that a digital network could reliably get a message from A to B without relying on any central nodes.So what Paul Baran needed was some way — or someone — to prove his idea could work. And that someone turned out to be a young math teacher who worked across the street at Santa Monica High School. In the late 1950s and early 1960s, she spent summers and sabbaticals moonlighting at RAND, writing code. Her name was Sharla Perrine.Sharla would have been the odd one out back then, the rare woman among a sea of men.Doug Rosenberg: I mean, women were secretaries back then. There were not women in engineering jobs in 19, the early 1960s. It was a bunch of guys in crew cuts.Samia Bouzid: This is Doug Rosenberg, a systems engineer.Doug Rosenberg: There were not women in engineering jobs in the early 1960s. It was a bunch of guys in crew cuts.Samia Bouzid: Doug was a close friend of Sharla’s husband, Barry Boehm. He says Sharla could hold her own. Born in Seattle, she had grown up in Santa Monica during the Depression. Her mother, who had immigrated to the U.S. from Sweden, raised Sharla by herself — her marriage ended around the time Sharla’s older sister died in 1932. Sharla was 2 at the time.

So, in the Perrine household, there were no gender roles. If something broke, there was no man around to fix it and no money to hire someone. So, Sharla’s mother figured out how to do things herself.Tenley Burke: Her mother was a carpenter, so that she could fix things and create things and not have to buy them. Anything that needed fixing they did themselves.Samia Bouzid: This is Sharla’s daughter Tenley, and she says Sharla was the same way.Tenley Burke: She was just no-nonsense, let’s do it ourselves, you can do anything. She didn’t like dilly dallying. She got down to business, and that’s just who she was. She was serious about everything she did.Samia Bouzid: Sharla always had a knack for math, and after earning a degree in teaching from UCLA, she went on to teach math, first at a junior high and then at a high school. But she also gravitated toward programming.Tenley Burke: I could see that RAND was a pull for her because it was so local and it was full of people who were thinking big thoughts. And she always said that she liked to talk to men at parties because they were talking about interesting things, and that’s what she wanted to be doing — she wanted to be in the interesting conversations.Samia Bouzid: RAND did turn out to be an intriguing workplace. While she was waiting for her security clearance in 1959, she met someone who would join her in many interesting conversations: a computer scientist named Barry Boehm. Here’s how he told it to the Computer History Museum in 2017.Barry Boehm: There we were down there in the basement and we, we got to know each other and she's now my wife.[Background chatter]Samia Bouzid: In addition to falling in love, Sharla also sharpened her programming skills writing simple computer code. And then, in the early 1960s, came her big assignment.Paul Baran needed someone to prove that his big idea — the one that could save the country from its massively unreliable communications systems in the event of an attack — could actually work.[AD BREAK]Doug Rosenberg: The way you figure out if it's gonna work or not is you simulate it.