The 1201 alarm was triggred by the Apollo 11 guidance computer. The computer was overloaded with data and ran out of memory so the program gave the famous 1201 alarm. It rebooted and gave a 1202 alarm. This was also a alarm that the computer was running out of memory just. Now Neil Armstrong had do do a manual landing without the assistance of the landing guidance computer.
[Mission Control] Houston. You are go for landing. Over
[Armstrong] Roger that. Go for landing, we have an alarm.
[Mission Control] 1201, Roger 1201 alarm.
[Mission Control] We’re go. Hang tight. We’re go.
Neil Armstrong landed on the moon with less than 30 seconds of fuel left.