The Core
We call the assembly portion of RetroForth the core. The core is an interesting place, since it provides the initial functionality needed to bootstrap RetroForth, yet it doesn't actually provide a lot of inherent functionality.
The core consists of a handful of words and variables used to implement the interpreter and compiler, but not stack manipulation, arithmetic, or even memory management. It's really a skeleton on which a dialect of Forth can be built.
The core also encompasses a few I/O words like key, emit, type, and #, but this is only to make life easier for those doing new ports.
Most people don't need to delve deeply into the inner workings of the core, but if you want to modify the compiler itself, or alter some internal functionality, you should read the rest of this section.