anchor.diff:      (let ((next (aref fat cluster-n)))
         (setf (aref fat cluster-n) 0
               cluster-n next)))
  -
     ;; mark directory entry (or entries) as free
     (free-file-entry directory start)
  -
     ;; Write to disk
     (write-fat disk fat32 fat)
     (write-file fat32 disk cluster-n fat directory))
  
positive.code:         (assert source-start (source-start) "Source file not found. ~s" source)
          (multiple-value-bind (dest-dir dest-cluster dest-start) (open-file-metadata host dest)
            (assert (not dest-start) (dest-start) "Destination file alredy exist. ~s" dest)
  
            (let ((dest-offset))
              (multiple-value-setq (dest-offset dest-dir)
                (create-directory-entry dest-dir
  
negative.code:                               :pathname path
                                :format-control "Directory ~A not empty."
                                :format-arguments (list path))))
                   ;; free directory clusters
                   (do ((cluster-n (read-first-cluster parent-dir dir-offset)))
                       ((>= cluster-n (last-cluster-value fat32)))
  