C++ Tutorial/Class/protected inheritance

#include <iostream>
using namespace std;
class base {
protected:
  int i, j;
public:
  void setij(int a, int b) { i=a; j=b; }
  void showij() { cout << i << " " << j << "\n"; }
};

class derived : protected base{
  int k;
public:
  void setk() { 
    setij(10, 12); 
    
    k = i*j; 
  }
  void showall() { 
     cout << k << " "; 
     showij(); 
  }
};
int main()
{
  derived ob;
  ob.setk(); 
  ob.showall();
  return 0;
}