1.      Program to find the greatest common divisor (GCD).

1. #include <iostream.h>

2. #include <conio.h>

3. int gcd(int a, int b) {

4.     if (b == 0)

5.         return a;

6.     return gcd(b, a % b);

7. }

8. int main() {

9.     int num1, num2, result;

10.     cout << "Enter two numbers: ";

11.     cin >> num1 >> num2;

12.     result = gcd(num1, num2);

13.     cout << "GCD of " << num1 << " and " << num2 << " is " << result << endl;

14.     getch();

15.     return 0;

17. }