On August 20, 1969, fifty-one days after the Apollo 11 moon landing, Margaret Hamilton received a commendation from NASA for the software her team had written. The Apollo Guidance Computer had performed exactly as designed. When a pre-flight checklist error during the landing sequence threatened to abort the mission, software she had insisted on including — against objections that it was unnecessary weight — identified the problem and kept the navigation system running.

Hamilton was born on August 17, 1936, in Paoli, Indiana. She studied mathematics at Earlham College and moved to Boston, taking a software job at MIT to fund her husband's Harvard Law degree. She had not planned to stay in software. The work turned out to be more interesting than the plan.

She joined the MIT Instrumentation Laboratory in 1960, working on SAGE, the first real-time computer system for air defense. By 1965 she was leading the team developing in-flight software for the Apollo program — a position with no precedent because there was no software field yet, no established practices, no textbooks. She and her team invented the practices.

She coined the term "software engineering" and spent years arguing — unsuccessfully, at first — that software development should be treated with the same rigor as hardware engineering. NASA and the Department of Defense classified software as secondary to hardware. Schedules and budgets were built around hardware; software was expected to catch up. Hamilton's team worked nights and weekends for years because the institutional structure had not accounted for what the software actually required.

The error-detection software she insisted on including in the Apollo 11 landing sequence identified a hardware-triggered overload condition during the final four minutes of descent. The system deprioritized non-essential tasks and kept the navigation running. Neil Armstrong landed with sixty seconds of fuel remaining.

Hamilton received the NASA Exceptional Space Act Award in 2003 and the Presidential Medal of Freedom in 2016. The photograph of her standing next to the stacked printouts of Apollo software code — the code taller than she is — circulated widely in 2016. She was eighty years old when it was taken. She has been alive the entire time.