+----------------------------------------------------------------------+
|                         RT-11 SYSTEM                                 |
+------+----------------+-------------------------+--------------------+
       |                |                         |
       |                |                         |
  +----+----+      +----+-----+            +------+------+
  |   DL    |      |   DL     |            |  DH  or DZ  |
  +----+----+      +----+-----+            +------+------+
       |                |                         |
       |                |           +---+---+---+-+-+---+---+---+
       |                |           |   |   |   |   |   |   |   |
       |                |           |   |   |   |   |   |   |   |
PUN:   0                0           0   1   2   3   4   5   6   7

LUN:   0                1           2   3   4   5   6   7   8   9