On July 20, 1969, as Eagle descended toward the lunar surface, the guidance computer began flashing 1202 alarms because a stuck rendezvous radar was flooding it with data, and Margaret Hamilton's priority-scheduling code shed the low-priority tasks in real time and let the landing continue
The 1202 alarm that flashed inside Eagle at 33,500 feet above the Moon was not a computer failure. It was Margaret Hamilton's priority scheduler doing exactly what she had designed it to do.