Picture this: it is July 1969, Neil Armstrong and Buzz Aldrin are seconds from touching down on the Moon, and suddenly an alarm starts flashing inside their spacecraft. Disaster? Not quite. The computer was simply overwhelmed with data, and because one woman in Massachusetts had already imagined this exact moment years earlier, the machine knew precisely what to ignore.

That woman was Margaret Hamilton, and her software quietly let the lunar module keep landing while shrugging off the overload. She has died at the age of 90, Massachusetts Institute of Technology, her longtime employer, announced. Hamilton led the team at MIT that wrote the onboard flight software for NASA's Apollo missions, work so novel that it required inventing a new vocabulary. The term "software engineering," now used from Bangalore to Berlin without a second thought, was coined to describe what she and her colleagues were doing, because nothing like it had existed before.

She joined MIT in 1959, originally to support her husband through law school, and ended up becoming, by her own account, the first programmer the lab ever hired, and the first woman. A famous 1969 photograph shows her standing beside a stack of printed code taller than she was. Why does an alarm on a 1969 spacecraft still matter to us? Because Hamilton had designed the system to prioritise, instructing the computer to abandon lesser tasks and protect the landing above all else.