Because 1) bool is a useless type in C and C++ since it's an arithmetic type, 2) it's no clearer than an int. (consider a function that returns true on failure,

Because 1) bool is a useless type in C and C++ since it's an arithmetic type, 2) it's no clearer than an int. (consider a function that returns true on failure, logic being that the rest of the program should be aborted.) You expect that "true" is success, but you can't know without checking, and then you're back in the same situation as with int. In practice, idiomatically, you write something like if(!some_function(blah)), and in this context it totally doesn't matter whether the function returns bool or int.