Was the FORTH interpreter for your own use or did you sell it? I ask because it's always fun to see someone on HN that wrote products I saw in the pages of Rainbow long ago.
It was unusual in quite a few ways. For one thing it was subroutine threaded which made it a little faster than most FORTHs, also it used self-modifying code in an inner loop to save a cycle in an important place.
Most FORTHs at the time used block-based disk I/O because you could do that without a real operating system and have some nice benefits such being able to copy a block of source code to the screen buffer to edit in place, easy memory allocation, etc.
OS-9 had a handle-based API for filesystem access basically the same as UNIX and MS-DOS 2.0 so my FORTH used that. OS-9 had a choice of text editors, including a vi clone so I didn't feel the need to embed an editor in the interpreter.
