anchor.diff:  INSTANCE VARIABLE #reserved-sectors
   INSTANCE VARIABLE #fats
   INSTANCE VARIABLE #root-entries
  +INSTANCE VARIABLE fat32-root-cluster
   INSTANCE VARIABLE total-#sectors
   INSTANCE VARIABLE media-descriptor
   INSTANCE VARIABLE sectors/fat
  
positive.code: : read-cluster ( cluster# -- )
    dup bytes/cluster @ * cluster-offset @ + bytes/cluster @ read-data
    read-fat dup #clusters @ >= IF drop 0 THEN next-cluster ! ;
  : read-dir ( cluster# -- )
    ?dup 0= IF root-offset @ #root-entries @ 20 * read-data 0 next-cluster !
    ELSE read-cluster THEN ;
  
  : .time ( x -- )
    base @ >r decimal
  
negative.code: 
    \ For FAT32:
    sectors/fat @ 0= IF data @ 24 + 4c@ bljoin sectors/fat ! THEN
    #root-entries @ 0= IF data @ 2c + 4c@ bljoin ELSE 0 THEN fat32-root-cluster !
  
    \ XXX add other FAT32 stuff (offsets 28, 2c, 30)
  
  