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# How to find the factorial in C language

The factorial of a number n, represented by n!, is a product of n with all the positive numbers less than or equal to n. For example, $factorial(5) = 5 * 4 * 3 * 2 * 1 = 120$

Let’s see how we can find factorial in C. There are two methods:

1. Using a loop
2. Using recursion

Let’s explore both of them.

## 1. Using a loop

#include <stdio.h>
int main() {
int n, i;
// since we are taking, set the start value at 1.
int factorial = 1;
// define the value of n for which we have
// to compute the factorial.
n = 5;
// run the loop from 1 to that number, multiplying
// the previous result with i.

// no factorial for negative number, check if number is negative
if(n<0)
{
printf("Factorial does not exist");
return 1;
}
for (i = 1; i <= n; ++i) {
factorial = factorial * i;
}
printf("Factorial of %d = %d", n, factorial);
return 0;
}

## 2. Using recursion

#include <stdio.h>

int factorial(int n)
{
// base case.
if (n <= 1)
return 1;
// recursive case.
return n * factorial(n-1);

}
int main() {
int n;
// define the value of our n for which we have
// to compute the factorial.
n = -5;

if(n<0)
{
printf("factorial does not exist");
return 1;
}

// call the factorial(n) function.
printf("Factorial of %d = %d", n, factorial(n));
return 0;
}

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