Those rules are mostly met by the "xcomp" unit, which is
expected to have been loaded prior to icore and redefines ":"
and other defining words. So, in other words, when compiling
icore, ":" doesn't means what you think it means, go look in
B260.

This is loaded in two "low" and "high" parts. The low part is
the biggest chunk and has the most definitions. The high part
is the "sensitive" chunk and contains "LITN", ":" and ";"
definitions which, once defined, kind of make any more defs
impossible.

The gap between these 2 parts is the ideal place to put device
driver code. Load the low part with "393 LOAD", the high part
with "415 LOAD"