program1.cpp: In function `int main()': program1.cpp:39: warning: passing NULL used for non-pointer argument 3 of `void std::fill(_ForwardIter, _ForwardIter, const _Tp&) [with _ForwardIter = char*, _Tp = int]' program1.cpp:47: warning: comparison between signed and unsigned integer expressions program1.cpp:56: warning: comparison between signed and unsigned integer expressions