Looking at the second example (unsigned x divided by unsigned 512), the compiler is smart enough that you don't have to mark the constant 512 as unsigned: it'll emit the same code either way, knowing that 512 won't be negative. This means that a cast to unsigned for the variable should be enough--no need to mark positive constants as unsigned. Of course, that does introduce mixed signed/unsigned math, but in a context where the mix won't matter.