As part of the finalization of the DDS standard, a number of DDS-specific primitive types will be introduced. By using these types, you will ensure that your data is serialized consistently across platforms even if the C/C++ built-in types have different sizes on those platforms.
In this version of dds, the DDS primitive types are defined using the OMG's Common Data Representation (CDR) standard. In a future version of dds, you will be given the choice of whether to use these CDR-based types or C/C++ built-in types through a flag provided to the rtiddsgen tool.
Typedef's that begin with RTICdr are defined in <NDDSHOME>/include/ndds/cdr/cdr_type.h, which uses types that are further defined in <NDDSHOME>/include/ndds/osapi/osapi_type.h.