# Find factorial program in C

Factorial of an integer n is denoted by n! and determined as the product of all the positive descending integers. Factorial of an integer n is determined by the following equation;

n! = n * (n – 1) * (n – 2) * (n -3) * ……. * 3 * 2 * 1

If you want to determine the factorial of an integer 6, then the result will be as the following;

6! = (6 * 5 * 4 * 3 * 2 * 1) = 720

It should be mentioned that 0! = 1.

In this article we will try to understand and write factorial program in C programming language. We can write a factorial program in different methods. So of the methods of writing factorial program in C are as follows;

• Factorial program using loop in C
• Factorial program using function or recursion in C

Now, let’s see some C programs to find out factorial of an integer in C.

## Factorial program using loop in C

``````// factorial program using loop in c
#include <stdio.h>
int main(){
int number, i, fact = 1;

printf("Enter the number for calculating its factorial : ");
scanf("%d", &number);

for (i = 1; i <= number; i++){   // using loop to calculate factorial
fact = fact * i;
}
printf("\nFactorial of %d is = %d\n", number, fact);

return 0;
}
``````

### Output of this factorial program: ## Factorial program using function in C

``````// factorial program using function or recursion in c
#include<stdio.h>

long fact(int num){   // function to calculate factorial
if (num == 0){
return 1;
}else{
return (num * fact(num - 1));
}
}

int main(){
int num;
long factorial;

printf("Enter the integer to find factorial : ");
scanf("%d", &num);

if (num < 0){
printf("Factorial of negative integer is undefined.\n");
}else{
factorial = fact(num);
printf("%d! = %ld\n", num, factorial);
}
return 0;
}``````

### Output of this C factorial program Previous pageSum of natural numbers

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