#include <stdio.h>
 
/* 全局变量声明 */
int g;
 
int main (){
  /* 局部变量声明 */
  int a, b;
 
  /* 实际初始化 */
  a = 10;
  b = 20;
  g = a + b;
 
  printf ("value of a = %d, b = %d and g = %d\n", a, b, g);
  return 0;
}