Back in the 1980&#x27;s I had a TRS-80 color computer which was running a Unix-clone operating system called OS-9,  this was multi-tasking and multi-user so I could log into my Coco with a DEC Correspondent printing terminal.<p>I wrote a FORTH implementation for the 6809 in about 3k lines of assembly code which included the language plus the &#x27;standard library&#x27;.  Instead of the &#x27;standard&#x27; Forth I&#x2F;O,  there was an interface to Unix-style file-handle based I&#x2F;O.  It used subroutine threading so that FORTH compiled directly to 6809 code and the part that did dynamic dispatch used self-modifying code to shave off a few cycles.<p>FORTH is an interesting part of the story about why LISP didn&#x27;t take off on 1980&#x27;s microcomputers,  partly because if you wanted a LISP on an 8-bit micro,  you could get much of the way there with FORTH in a footprint even smaller than BASIC.