Personally I'd use: unsigned int a = 0xFFFF, not unsigned int a = -1.

This is a classic case of a readability issue. 0xFFFF is, in my mind, much clearer on your intention than -1. The only problem is that you're assuming a specific int size, but really, if you're working with bits, chances are good that you're working on a platform where you know the architecture size (at least on embedded platforms).