32-Bit_UID_and_GID_Macro_(Integrity_servers,_Alpha)_

   The C RTL supports 32-bit User Identification (UID) and Group
   Identification (GID). When an application is compiled to use
   32-bit UID/GID, the UID and GID are derived from the UIC as in
   previous versions of the operating system.

   To compile an application for 16-bit UID/GID support on systems
   that by default use 32-bit UIDs/GIDs, define the _DECC_SHORT_GID_
   T macro to 1.

   Not specifying _DECC_SHORT_GID_T provides long (32-bit) UID/GID.

   Compiling on older OpenVMS systems where long UID/GID is not
   supported, or compiling for legacy compatibility (_DECC_V4_SOURCE
   for VSI C Version 4 or _VMS_V6_SOURCE for OpenVMS Version 6),
   forces use of short (16-bit) UID/GID.