On a 32 bit platform, Is this structure legal? struct { UINT64 part1 : 48; UINT64 part2 : 16; }Parts; Do I have to tune the compiler to pack them into a single 64 bit space? While assigning some 32 bit value to Parts.part1, do I have to cast the r-value into UINT64? Sorry if this were a repetition. Thanks, kumaresh