Margaret Hamilton

Computer Scientist & Software Engineering Pioneer

About

Margaret Hamilton (1936–2026) was an American computer scientist who led the team that developed the on-board flight software for NASA's Apollo program. She began at MIT in 1959 writing weather-prediction software for Edward Lorenz, and at the Draper Laboratory began using the term 'software engineering' to give the discipline the same legitimacy as other engineering fields. Her rigorous approach to software design, including error detection and recovery, saved the Apollo 11 moon landing when the computer became overloaded minutes before touchdown. Her innovations in asynchronous software, priority scheduling, and human-in-the-loop decision making established foundational principles still used in safety-critical systems today. The Apollo story is rightly iconic, but it was a team's work, with more than 400 engineers under her direction, and popular retellings sometimes flatten the people and the hardware behind the landing. She died on 30 September 2026, aged 90.

Key Contributions

Led MIT's Apollo flight-software team, treating software as mission-critical engineering before the field had that status
Popularized 'software engineering' to argue that complex code deserved the same rigor and legitimacy as hardware engineering
Built priority scheduling and error-recovery behavior into Apollo guidance software, helping Apollo 11 continue during computer overload alarms
Turned human-in-the-loop safety and asynchronous software into practical design principles for critical systems
Founded Hamilton Technologies and developed Universal Systems Language around a preventative, before-the-fact approach to systems design

Videos & Interviews

Oral History of Margaret Hamilton

Three hours with the Computer History Museum, told in her own words. She traces her path from writing weather-prediction software for Edward Lorenz at MIT, to the SAGE air-defense system at Lincoln Laboratory, to Apollo at Draper. There is the "Lauren bug": her four-year-old daughter crashed a simulator by selecting the pre-launch program mid-flight. Hamilton argued for a fix and was overruled, because "the astronauts would never ever make a mistake," and on Apollo 8 they made exactly that one. Then the 1201 and 1202 priority displays she had personally written, which came up just before the Apollo 11 landing while the software shed lower-priority work and carried on. She tells how "software engineering" began as a joke among the hardware engineers until one of them stood up and called it engineering, and she ends with the philosophy she built a company on: development "before the fact," preventative rather than restorative.

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Connections

Edward Lorenz

Influenced by

Meteorologist & Founder of Chaos Theory, MIT

Her first job, in 1959, was programming Lorenz's weather models at MIT, on an LGP-30 in his office, before she had 'really been near a computer.' 'He taught me everything he knew about the LGP-30,' she remembered, and she called it 'one of the best things I ever did.' When she slipped back at four in the morning to fix a mistake she didn't want him to see, he worked it out the next day from the equations: where she had been, and what she had done.

youtube.com · en.wikipedia.org · news.mit.edu

Grace Hopper

Kindred

Computer Scientist & Naval Rear Admiral

Neither woman invented software; each insisted it be taken seriously as something built. Hopper argued the machine should come toward human language and wrote the compiler that made the argument stick; Hamilton, a generation later, argued that code carrying human lives deserved the word 'engineering' and made it stick by landing on the Moon. Both were pushing against the same assumption — that the real work was the hardware.

Alan Turing

Kindred

Mathematician & Computer Science Pioneer

In 1949, at the conference launching Cambridge's EDSAC, Turing asked how anyone could make sure a routine is right, and answered that the programmer should make 'definite assertions which can be checked individually, and from which the correctness of the whole programme easily follows.' Hamilton reached the same conviction the hard way, through Apollo's errors, and built a company on it: define a system so completely that whole classes of mistakes can't be written. Read this way, both refused to treat correctness as something you find out after the code runs.

Alan Turing, Checking a Large Routine (1949) · arxiv.org · youtube.com

David Robinson

Kindred

Former Safety Transparency Lead, OpenAI

Hamilton called the usual way of building software an 'after the fact life cycle', where you write it and then hunt the errors, 'like back in the old medical community where they didn't wash their hands.' Half a century later Robinson left OpenAI describing the same pattern in AI, 'shipping new capability and risk every Tuesday,' and asked that a release wait until its safety criteria are met, however long that takes. He also pointed to the Challenger launch, where the risk 'had been known and documented and accepted.' One pairing, read across fifty years: safety is a property you design in, not one you discover after release.

youtube.com · youtube.com · youtube.com