## C Language: Factorial of a Number using For loop

**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, i.e 0! = 1

#include <stdio.h>

int main()

{

int n, i;

unsigned long long fact = 1;

printf(“Enter an integer: “);

scanf(“%d”,&n);

// Displays error if the user enters a negative integer

if (n < 0)

printf(“Error! Factorial of a negative number doesn’t exist.”);

else

{

for(i=1; i<=n; ++i)

{

fact *= i; // fact = fact*i;

}

printf(“Factorial of %d = %llu”, n, fact);

}

return 0;

}

**Output:**

Enter a positive integer: 5

Factorial of 5 = 120