C<? is a flag indicating whether a character is waiting in the
input stream. 1 means yes, 0 means no. It is the responsibility
of C<* to update that flag.

WORDBUF is the buffer used by WORD

BOOT C< PTR is used when Forth boots from in-memory
source. See "Initialization sequence" below.

INTJUMP All RST offsets (well, not *all* at this moment, I
still have to free those slots...) in boot binaries are made to
jump to this address. If you use one of those slots for an
interrupt, write a jump to the appropriate offset in that RAM
location.

                                                        (cont.)