C Program to find factorial of number using Recursion

Factorial of n is the product of all positive descending integers. Factorial of n is denoted by n!.

Example :

5! = 5*4*3*2*1 = 120  
3! = 3*2*1 = 6

Here, 5! is pronounced as "5 factorial", it is also called "5 bang" or "5 shriek".

The factorial is normally used in Combinations and Permutations (mathematics).

There are many ways to write the factorial program in c language. Let's see the 2 ways to write the factorial program.

* Factorial Program using loop
* Factorial Program using recursion

Factorial Program using loop :

Program :

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

Output :

Enter a number: 6
Factorial of 6 is: 720

Factorial Program using recursion in C :

Program :

#include<stdio.h>  
  
long factorial(int n)  
{  
  if (n == 0)  
    return 1;  
  else  
    return(n * factorial(n-1));  
}  
   
void main()  
{  
  int number;  
  long fact;  
  printf("Enter a number: ");  
  scanf("%d", &number);   
   
  fact = factorial(number);  
  printf("Factorial of %d is %ld\n", number, fact);  
  return 0;  
}

Output :

Enter a number: 7
Factorial of 7 is 5040

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