@ipd @NoelJPenaflor It's assembler, and each book is one revision of the entire code base.

It's on github here: https://github.com/chrislgarry/Apollo-11

Also, it was developed by a team for which Margaret Hamilton was the director. It was also developed in conjunction with the development of the hardware. This makes it a somewhat strange platform, with special hardware hacks to improve performance (or more commonly, save memory) on the software side.

It is true that it was at least partly written by hand, and by hand I mean using pen and paper. The assembler was running on IBM mainframes, and the typical way to program with those machines was to write code on paper forms, these forms were then transcribed onto punchcards which were then fed into the assembler as a batch job.

Now, Apollo 11 was in 1969, and they kept developing the software after that, and interactive terminals were a thing so they may very well have used them to write code at least later. There was a hardware device used to emulate the memory boards on the actual hardware so they could load the memory with the output of the assembler and then run the tests on actual hardware. I don't know how long the compile/test cycle was on this system. I also thing the number test computers they had was limited so that would have been a problem as well.

It's an extremely fascinating system and for anyone interested I recommend this book: https://link.springer.com/book/10.1007/978-1-4419-0877-3