Because you didn't used any C++ style strings. Only C style strings, aka char arrays.

It's because a C++ string is not equivalent to a character array (C style String). Your code works fine when using a char array instead 40550976.It gives a error as compiler cannot implicitly covert c++ string into a char array. To construct C string out of a string c_str method is used. Difference bw c and c++ style string .