Apollo-11

Best for: engineers and historians who want to read the actual flight software that landed humans on the Moon.

Apollo-11 is a preserved copy of the original Apollo Guidance Computer (AGC) source code for the Command Module (Comanche055) and Lunar Module (Luminary099), transcribed from scanned NASA listings by the Virtual AGC project and maintained on GitHub by Chris Garry. It is written in AGC assembly and reads unlike any modern codebase: hand-written comments, terse mnemonics, and the famous BURN_BABY_BURN -- MASTER IGNITION ROUTINE.

What makes it worth reading: it is a rare chance to study production-critical software written under extreme memory and reliability constraints, with the engineering culture visible directly in the comments. The repository is archived in the Software Heritage library and has been translated into more than thirty languages.

Where it falls short: this is a historical artifact, not a tool. You cannot run it without an AGC emulator, there is no practical application to modern development, and the licensing is non-standard (NASA-derived, marked NOASSERTION on GitHub). Treat it as reading material and study reference rather than a dependency.

Details: AGC assembly. Community-maintained transcription.