EDIT : OK, just got it: I got the logic backwards: first, -1 is converted to uint. Second, -1 uint means UINT_MAX. Third, the binary representation of UINT_MAX

EDIT : OK, just got it: I got the logic backwards: first, -1 is converted to uint. Second, -1 uint means UINT_MAX. Third, the binary representation of UINT_MAX is all 1s. The way I previously understood it, the -1 would be a signed integer which has some binary representation, and that binary representation would become the uint. Weird bit of arcana. Below is my mistaken comment. (Notice that I pretended that UINT_MAX is not all 1s, which is silly. I suppose I made that mistake because I "couldn't be wrong" or something.) As far as I know, your definition can't be inferred from the C standard. The answer itself acknowledges that -1 doesn't yield 0xFFFF… on every platform. The only guarantee is that it will yield UINT_MAX, which is not what was asked. Otherwise, that would mean that C basically mandates a two's complement representation. Does it?