anchor.diff:  
   : close
      inode @ inode-size @ free-mem
  -   group-descriptors @ group-desc-size @ free-mem
  +   group-descriptors @ blocks-per-group @ free-mem
      free-data
      blocks @ ?dup IF #blocks @ 4 * free-mem THEN
   ;
  
positive.code: INSTANCE VARIABLE block-size
  INSTANCE VARIABLE inodes/group
  
  INSTANCE VARIABLE group-desc-size
  INSTANCE VARIABLE group-descriptors
  
  : seek  s" seek" $call-parent ;
  
negative.code:   ELSE
       data @ 58 + w@-le inode-size !
    THEN
    data @ 20 + l@-le blocks-per-group !
  
    \ Read the group descriptor table:
    first-block @ 1+ block-size @ *
    blocks-per-group @
    read-data
    data @ group-descriptors !
  
  