Recently digitized and turned into a repo, the original Apollo 11 guidance computer source code has been made available for viewing on Github.
In MAIN.agc, the repo author comments that they
split the huge monolithic source code into smaller, more manageable chunks--i.e., into individual source # files.
A bit later, the author states
It may be reasonably asked why tens of thousands of lines of source are joined by means of inclusion, rather than simply assembling the source files individually and then linking them to form the executable. The answer is that the original development team had no linker.
I know what linkers are and I understand the point of them- but I've never heard of the phrase (as far as ASM goes) "joined by means of inclusion".
What does this mean? Considering that linkers are a big deal in programming, I'm curious what this substitution of linkers by "means of inclusion' is and how it works.