What is a scope resolution operator in C ?

The scope resolution operator (::) is useful in C programming when both global and local variables have the same name, a statement using that name will access the local variable (more precisely, it will access the variable of that name in the innermost block containing that statement).
The scope resolution operator represented as :: (a double colon) can be used to select the global variable explicitly.

Consider the example below.

#include<stdio.h>
int x = 10;
int main() 
{
  int x = 20;
  printf("%d\n",x);
  printf("%d\n", ::x);
  return 0;
}
OutPut:
20
10