o  See the OpenVMS Calling Standard for a full description of
       procedure descriptors.

    o  You must specify .LOCAL_PROCEDURE_DESCRIPTOR before the code
       of the routine it describes.

    o  See the description for the $PROCEDURE_DESCRIPTOR and $ROUTINE
       library macros. These macros define the procedure identifier
       and define the storage for the procedure descriptor.

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

    o  If automatic data alignment is enabled, this directive aligns
       the current location counter to a quadword (64-bit) boundary
       before defining the procedure identifier.