I don't think "register" is a good term to describe a system's smallest addressable storage unit. If you don't like "byte", I'd suggest "smallest addressable storage unit" would be a precise term. In any case, I was responding to the claim that the size of a uint32_t is "set in stone" at four bytes for all conforming implementations, which a reasonable person might interpret as saying that sizeof (uint32_t) is required to be 4. I think it's rather silly that the Standard defines no category of programs between Strictly Conforming programs, a category so narrow as to be almost useless, and Conforming programs, a category so broad as to be essentially meaningless, and only defines two categories of implementations, either of which would be allowed (because of the "One Program" loophole) to behave in arbitrary fashion when given almost any program. If the Standard sought to actually categorize things usefully, separating out common-integer-size implementations from weird-integer-size implementations would make a lot of sense. Unfortunately, the authors of the Standard seem to go out of their way to avoid suggesting that some implementations should be considered inferior to others.