C/C++ data types for binary query output in libpq/libpg++

Could someone tell me where the header file is located that defines
the data types used in C/C++ when calling the libpq/libpq++
methods/functions that return fields of built-in data types when using 
binary cursors?  I can't seem to find a mapping of postgres type <->
C/C++ types in the manuals, nor can I seem to find the appropriate
source file.  Any help would be greatly appreciated.

thanks,
Matt Denny