# C Program to calculate factorial using iterative method

In this tutorial, we will learn to write the program to find the factorial of numbers using the C programming language. Here we are going to follow an iterative approach.

Before moving forward let’s understand

## What is Factorial of a number?

Factorial of a whole number ‘n’ is the product of that number ‘n’ with its every whole number in descending order till 1.

For example

Factorial of 5 is 5*4*3*2*1 = 120

And factorial of 5 can be written as 5!.

Note: To store the largest output we are using long long data type. Long long takes double memory as compared to single long.

There are multiple ways to write the program in C to calculate the factorial of the whole number.

In this tutorial, we will learn to write using

1). Using For Loop

2). Using Function

## 1). Factorial Program in C of a given number using for Loop

``````#include<stdio.h>
int main() {
int i, num, factorial = 1;
printf("Enter a whole number to find Factorial = ");
scanf("%d", &num);
for (i = 1; i<=num; i++) {
factorial = factorial * i;
}
printf("Factorial of %d is: %d", num, factorial);
return 0;
}``````

Output

## 2). Factorial Program in C using Function and While Loop

``````#include<stdio.h>
int fact(int num) {
int i = 1, fact = 1;
while (i <= num) {
fact *= i;
i++;
}
return fact;
}
int main() {
int i, num, factorial = 1;
printf("Enter a whole number to find Factorial = ");
scanf("%d", & num);
printf("Factorial of %d is: %d", num, fact(num));
return 0;
}``````

Output