#include <iostream>

// with this line, the program won't link because k is prototyped, but not defined.
//extern int k;

// with this line the program links correctly, because k is defined;
extern int k=2;

extern int i = 1;

extern const int j = 2;

using namespace std;

int main() {
  cout << "i = " << i << endl;
  cout << "k = " << k << endl;
  return 0;
}