cpp detect os
#include <iostream>
using namespace std;
int main() {
#ifdef _WIN32
cout << "This is Windows." << endl;
#elif __linux__
cout << "This is Linux." << endl;
#elif __APPLE__
cout << "This is MacOS." << endl;
#else
cout << "This is an unknown operating system." << endl;
#endif
return 0;
}