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 HP C Version 4 or _VMS_V6_SOURCE for OpenVMS Version 6), forces use of short (16-bit) UID/GID.