this is utter nonsense. in C, since before C89, all non-zero values are considered true in conditional contexts (if, for, while, ?:). http://port70.net/~nsz/c/c89/c89-draft.html#3.6.4.1. false must therefore be exactly zero. !1 is also always 0, as it must be. http://port70.net/~nsz/c/c89/c89-draft.html#3.3.3.3.