Picture a photograph from 1969. A woman stands beside a stack of paper taller than she is. That paper is code — the actual printed instructions that would guide two astronauts to the Moon. The woman is Margaret Hamilton, and without her, Apollo 11 might never have landed at all.

Hamilton, who has died aged 90, joined MIT in 1959 almost by accident. She had taken a job there to support her husband through law school, not realizing she would end up leading the team that wrote every line of onboard software for NASA's Apollo missions. "I was the first programmer to join and the first woman they hired," she told the Guardian in 2019. At the time, nobody even had a name for what she was doing.

It was Hamilton herself who coined the term "software engineering," a phrase so ordinary now that it is easy to forget someone had to invent it. Here is the moment that made her famous. Minutes before Armstrong and Aldrin's historic touchdown, an onboard computer suddenly flashed an alarm: overload. Had this happened in a lesser system, the mission might have been aborted.