C language extern keyword

When local variables conflict with global variables, you can access global variables using the extern keyword.

#include <string.h>
#include <stdio.h>

int a = 123;
int main()
{
  int a = 456;
  int b;
  {
    extern int a;
    printf("%d\n", a); // 123
    b = a;
  }
  
  printf("%d\n", a); // 456
  printf("%d\n", b); // 123
}

output:

123
456
123