/* Using a signal handler. */

#include <stdio.h>
#include <signal.h>
#include <stdlib.h>

#define   MAXSTRING   100

void   cntrl_c_handler(int sig);
int    fib(int n);

int main(void)
{
   int   i;

   signal(SIGINT, cntrl_c_handler);
   for (i = 0; i < 46; ++i)
      printf("fib(%2d) = %d\n", i, fib(i));
   return 0;
}

void cntrl_c_handler(int sig)
{
   char   answer[MAXSTRING];

   printf("\n\n%s%d\n\n%s",
      "Interrupt received!  Signal = ", sig,
      "Do you wish to continue or quit? ");
   scanf("%s", answer);
   if (*answer == 'c')
      signal(SIGINT, cntrl_c_handler);
   else
      exit(1);
}

int fib(int n)
{
   if (n <= 1)
      return n;
   else
      return (fib(n - 1) + fib(n - 2));
}