How extern is working in C, inside function. :         #include<stdio.h>
        
        int a = 33;
        
        
            int main()
            {
              int a = 40;
              
              {
                extern int a;
            
                   printf("\n%d",a);   
              }
              return 0;
            }
    
Output : 33

Can anyone please let me know how Extern is working here ?