Example to find the GCD of two positive integers (entered by the user) using recursion in C programming.

To understand this example, you should have the knowledge of following C programming topics:

This program takes two positive integers as input from the user and calculates GCD using recursion.

Visit this page to learn how you can calculate the GCD using loops.

```
#include <stdio.h>
int hcf(int n1, int n2);
int main()
{
int n1, n2;
printf("Enter two positive integers: ");
scanf("%d %d", &n1, &n2);
printf("G.C.D of %d and %d is %d.", n1, n2, hcf(n1,n2));
return 0;
}
int hcf(int n1, int n2)
{
if (n2 != 0)
return hcf(n2, n1%n2);
else
return n1;
}
```

**Output**

Enter two positive integers: 366 60 G.C.D of 366 and 60 is 6.