At the MIT Instrumentation Lab in the 1960s, Margaret was working on code for the Apollo Guidance Computer. A working mom, she sometimes did what a lot of us do: she took her daughter, Lauren, to the office. Margaret would often test programs in the simulator, and Lauren liked to play astronaut like her mom. One day, Lauren crashed the simulator after she pressed a button that set off a prelaunch program while the mission was in mid-flight.

Margaret didn’t scold Lauren. Instead, she was struck with a thought: “What if an astronaut did the same thing during a real mission?” Margaret lobbied to add code that would prevent a system crash from actually happening if he did.

This way of thinking came to define Margaret’s work. She’d always ask, “What if something you never thought would happen, happens?” Then, she’d develop and test a system that would be prepared for that scenario.

Her “what if” mindset was crucial throughout the Apollo missions, where the software had to work perfectly, and had to work the first time, in space. Keep in mind, this was at a time when software engineering literally wasn’t even a thing yet—Margaret herself coined the phrase “software engineering” while working on Apollo.