o  String descriptors are used in calling certain system
       routines.

    o  The string-length field is two bytes in size.

    o  Descriptor information (2 bytes) is always set to ^X010E.

    o  The pointer field is a 32-bit pointer to the string (4 bytes).

    o  If natural alignment is enabled (using .ENABLE ALIGN_DATA),
       the descriptor is quadword aligned. This allows you to access
       the entire descriptor (2 data words and a longword address) on
       a quadword boundary.

    o  You can only use this directive within data or mixed psects
       (psects that have either the NOEXE or MIX attributes).

    o  This directive also accepts VAX MACRO syntax. See the
       VAX MACRO and Instruction Set Reference Manual for details.