Moves the structure pointer backwards at the current level
   and displays the structure at the new position.

     Format:

        BACK [n]

   n
        The number of positions by which you would like to move back.
        If you are analyzing an indexed file and are positioned at the
        10th record in a bucket, "BACK 1" positions you at and displays
        the 9th record in the bucket, and a subsequent "BACK 3" positions
        you at and displays the 6th record in the bucket.  The notation
        for this argument is described in HELP RADIX.  If "n" is omitted,
        the default value is 1.