anchor.diff:  \ FLUSH ( -- ) empties all local buffers.  Before doing so,
   \ any buffers marked for update will be written back.
   t: FLUSH ( -- )
  -  0 BEGIN DUP 64 < WHILE
  +  0 BEGIN DUP #buffers < WHILE
       DUP dirty? IF DUP wrb THEN
       1+
     REPEAT DROP ;
  
positive.code: \ side effect of allowing the competent user to reallocate
  \ the buffers to suit the needs of her application.
  t: 0blocks ( -- )
    HERE clocks ! 64 CELLS ALLOT
    HERE blocks ! 64 CELLS ALLOT
    HERE laundry ! 64 ALLOT
    HERE buffers ! 64 1024 * ALLOT
    EMPTY-BUFFERS
    ;
  
negative.code: \ internal cache.  If it's missing from the cache, return TRUE.
  \ Otherwise, return the cache row and FALSE.
  t: missing ( b -- b -1 / b r 0 )
    0 BEGIN DUP #buffers < WHILE
      2DUP CELLS blocks @ + @ = IF 0 EXIT THEN
      1+
    REPEAT DROP -1 ;
  