[Valmont]

No need to hate . We can do it nicely OS-independant:

 #include <iostream>
#include <cctype>
#include <string>
#include <algorithm>

using namespace std;

int main()
{
   string s = "UPPERCASE (?)";
   
   transform(s.begin(), s.end(), s.begin(), (int(*)(int)) tolower);
   
   cout<<s<<endl;
   
   return 0;
}