Margaret Hamilton, the MIT computer scientist who coined the term 'software engineering' and led the team that wrote the Apollo guidance software, died on 30 September at the age of 90. MIT announced her death on Wednesday; the news circulated widely on 7 and 8 October.

Born in Paoli, Indiana, in 1936, Hamilton studied mathematics at Earlham College and planned to go on to a PhD. Instead she taught herself to program at MIT, first writing weather-model code for the meteorologist Edward Lorenz — the code behind the discovery of chaos theory's 'butterfly effect' — and later software for the Air Force's SAGE air-defence system.

In 1965 she joined MIT's Instrumentation Laboratory as the first programmer hired to build the onboard flight software for NASA's Apollo programme, and the first woman on the team. The code was stored in 'rope core' memory: wires woven by hand through magnetic cores by former textile workers, which earned her the nickname 'rope mother'. She led a team of roughly 100 people.

Her most famous decision was to build error detection and recovery into the software — a failsafe that, if the guidance computer was overloaded, would shed low-priority tasks and keep the ones needed to land. Minutes before Apollo 11 touched down in 1969, that is exactly what happened: the computer flashed alarms, mission control considered aborting, and the software recovered by itself.

'If the computer hadn't recognised this problem and taken recovery action, I doubt if Apollo 11 would have been the successful Moon landing it was,' she later wrote. The Apollo software she helped develop was added to GitHub in 2015.

Hamilton received the Presidential Medal of Freedom in 2016 and was immortalised as a LEGO minifigure in the 'Women of NASA' set in 2017. She later founded two software companies, Higher Order Software and Hamilton Technologies, built around her ideas of error prevention and defensive programming.

She is survived by her daughter, Lauren, a son-in-law, two grandsons and four great-grandchildren.

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