Use :: to reference global variable : global variable « Language Basics « C++ Tutorial

1. C++ Tutorial
2. Language Basics
3. global variable

#include <iostream>
using namespace std; 
int global_name = 1001;

int main(void){
   int global_name = 1;  // Local variable

   cout << "Local variable value " << global_name << '\n';
   cout << "Global variable value " << ::global_name << '\n';
}