1   
    2   int counter = 1;
    3   
    4   int main()
    5   {
    6       if (fork() == 0) {
    7         counter--;
    8         exit(0);
    9       }
   10       else {
   11         Wait(NULL);
   12         printf("counter = %d\n", ++counter);
   13       }
   14       exit(0);
   15   }