Write a C Program to find factorial by recursion and iteration methods

By | March 22, 2017

C Program to find factorial by recursion and iteration methods


Write a C Program to find factorial by recursion and iteration methods. Here’s a Simple Program to find factorial of a number using both recursive and iterative methods in C Programming Language.

This Program prompts user for entering any integer number, finds the factorial of input number and displays the output on screen.


Factorial of a Number : :


A factorial of a number x is defined as the product of x and all positive integers below x.  A factorial is product of all the number from 1 to the user specified number.

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. You will learn to find the factorial of a number using recursion and iterative methods in this example.

1. Using Recursion : :


We will use a recursive user defined function to perform the task. Here we have a function fact( )  that calls itself in a recursive manner to find out the factorial of input number.

2. Using Iterative : :


To calculate the factorial in a for loop, it seems like all we would have to do is start from x and then multiply by all integer values below x, and just hold that value until we are done iterating.

Below is the source code for C Program to find factorial by recursion and iteration methods which is successfully compiled and run on Windows System to produce desired output as shown below :


SOURCE CODE : :


/* Program to find the factorial of a number by recursion and iteration method*/



#include<stdio.h>
long int fact(int n);
long int Ifact(int n);

int main( )
{
	int num;
	printf("Enter a number : ");
	scanf("%d", &num);

	printf("\nUsing Recursion :: \n");
	if(num<0)
		printf("No factorial for negative number\n");
	else
		printf("Factorial of %d is %ld\n", num, fact(num) );

    printf("\nUsing Iterative :: \n");

	if(num<0)
		printf("No factorial for negative number\n");
	else
		printf("Factorial of %d is %ld\n", num, Ifact(num) );

		return 0;
}/*End of main()*/

/*Recursive*/
long int fact(int n)
{
	if(n == 0)
		return(1);
	return(n * fact(n-1));
}/*End of fact()*/

/*Iterative*/
long int Ifact(int n)
{
	long fact=1;
	while(n>0)
	{
		fact = fact*n;
		n--;
	}
	return fact;
}/*End of ifact()*/


OUTPUT  : :


Enter a number : 8

Using Recursion ::
Factorial of 8 is 40320

Using Iterative ::
Factorial of 8 is 40320

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