Logical values start on an arbitrary byte boundary and are stored
  in one, two, or four contiguous bytes.  The low-order bit (bit 0)
  determines the value.  If bit 0 is set, the value is .TRUE.; if bit
  0 is clear, the value is .FALSE.  The remaining bits are undefined.

  When a logical value is stored in memory, all of its bits are
  stored.  For example, consider the following:

     LOGICAL*4 L1, L2, L3
     L1 = L2 .AND. L3

  This example does a full 32-bit AND of L2 and L3, and stores all 32
  resulting bits in L1.