/* 
 * simple example of defining and using functions
 * and using library function sqrt() (must compile with -lm).
 */
#include <stdio.h>
#include <math.h>

/* function declarations / prototypes */

/* add two integers */
int add(int a, int b);

/* print numbers from n down through 0 */
void countdown(int n);

/* main program */

int main(void) {

	int x, y;

	printf("enter two integers\n");
	if (scanf("%d %d", &x, &y) == 2) {
		printf("x, y, sum %d %d %d\n", x, y, add(x, y));
		countdown(x);
		printf("sqrt of x %f\n", sqrt(x));
		return 0;
	} 
	else {
		printf("not numbers\n");
		return 1;
	}
}

/* function definitions */

int add(int a, int b) {
	return a+b;
}

void countdown(int n) {
	if (n >= 0) {
		printf("%d\n", n);
		countdown(n-1);
	}
}