Block 6000
( forth79.4th -- the FORTH-79 Required Word Set for v4,        )
( as colon definitions, loaded when the system boots.          )
( docs/v4.0.0/NUCLEUS.md.  Blocks 6000 up.                     )
( A word moves here from the assembled nucleus, v4/capsule,    )
( once its colon definition passes POST.                       )
Block 6001
( U*  U/MOD -- FORTH-79 unsigned multiply and divide.          )
( Neither v3 nor the v4 nucleus had them.                      )
( The first two words count the bits in a cell.               )
: (BITS) ( -- n )
  0 1 BEGIN DUP WHILE 2* SWAP 1+ SWAP REPEAT DROP ;
(BITS) CONSTANT (NB)
VARIABLE (UD)
( u1 u2 -- ud   the unsigned double product )
: U* UM* ;
Block 6002
( ud u1 -- u2 u3   unsigned: u2 the remainder, u3 the quotient )
( One bit a step: shift ud left, and take u1 from its high     )
( cell whenever it goes, counting that in the low cell.        )
( A zero divisor is error 11, Division by zero.                )
: U/MOD
  DUP 0= IF DROP DROP DROP 11 NODE-ERROR ! THEN  (UD) !
  (NB) 0 DO
    DUP 0< >R  2* OVER 0< IF 1+ THEN  SWAP 2* SWAP
    R> IF (UD) @ - SWAP 1+ SWAP
    ELSE DUP (UD) @ U< 0= IF (UD) @ - SWAP 1+ SWAP THEN THEN
  LOOP SWAP ;