Margaret Hamilton and the printed code for the Apollo Guidance Computer. Draper Laboratory

A few days ago, on September 30, 2026, pioneering computer scientist Margaret Hamilton died in Cambridge, Mass. at age 90. Hamilton was the leader of the team that wrote the code for the computer used on the Apollo missions to the moon in the late 1960s and early 70s.

Hamilton invented the term “software engineering” and led the software engineering team at MIT that developed the software for the Apollo guidance computer (AGC). Her savvy ideas built into the AGC software prevented the a disastrous computer malfunction on the first lunar landing on July 20, 1969. Could the landing have been done without her?

While clearly Hamilton never actually landed on the moon herself, it was her software that made it possible. Hamilton designed the software to be fault tolerant and ignore lower level demands, focusing on the most important task at hand, which was a safe touchdown of the Apollo 11 lunar lander on surface. Hamilton later described it this way in a letter.

 

The computer (or rather the software in it) was smart enough to recognize that it was being asked to perform more tasks than it should be performing. It then sent out an alarm, which meant to the astronaut, ‘I’m overloaded with more tasks than I should be doing at this time and I’m going to keep only the more important tasks’; i.e., the ones needed for landing … Actually, the computer was programmed to do more than recognize error conditions. A complete set of recovery programs was incorporated into the software. The software’s action, in this case, was to eliminate lower priority tasks and re-establish the more important ones … If the computer hadn’t recognized this problem and taken recovery action, I doubt if Apollo 11 would have been the successful Moon landing it was.