Example to find factorial of a non-negative integer (entered by the user) using recursion.

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

The factorial of a positive number n is given by:

factorial of n (n!) = 1*2*3*4....n

The factorial of a negative number doesn't exist. And the factorial of 0 is 1.

You will learn to find the factorial of a number using recursion in this example. Visit this page to learn, how you can find the factorial of a number using loop.

```
#include <stdio.h>
long int multiplyNumbers(int n);
int main()
{
int n;
printf("Enter a positive integer: ");
scanf("%d", &n);
printf("Factorial of %d = %ld", n, multiplyNumbers(n));
return 0;
}
long int multiplyNumbers(int n)
{
if (n >= 1)
return n*multiplyNumbers(n-1);
else
return 1;
}
```

**Output**

Enter a positive integer: 6 Factorial of 6 = 720

Suppose the user entered 6.

Initially, the `multiplyNumbers()`

is called from the `main()`

function with 6 passed as an argument.

Then, 5 is passed to the `multiplyNumbers()`

function from the same function (recursive call). In each recursive call, the value of argument `n` is decreased by 1.

When the value of `n` is less than 1, there is no recursive call.