C Program to calculate factorial using iterative method

Interview Preparation

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.

Please follow this article for factorial program in C using recursion

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

c program to calculate factorial using iterative method

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

c program to calculate factorial using iterative method

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