Factorial program in c

Factorial program in c: c code to find and print factorial of a number, three methods are given, first one uses for loop, second uses a function to find factorial and third using recursion. Factorial is represented using '!', so five factorial will be written as (5!), n factorial as (n!). Also
n! = n*(n-1)*(n-2)*(n-3)...3.2.1 and zero factorial is defined as one i.e. 0! = 1.

Factorial program in c using for loop

#include <stdio.h>

#includde<conio.h>

void main()

{

  int c, n, fact = 1;

  printf("Enter a number to calculate it's factorial\n");

  scanf("%d", &n);

  for (c = 1; c <= n; c++)

  fact = fact * c;

  printf("Factorial of %d = %d\n", n, fact);

  getch();

}

---------------------------------------------------------------------------------------------

Factorial program in c using function

#include <stdio.h>
#include<conio.h>
long factorial(int);
void main()
{
  int number;
  long fact = 1;
  printf("Enter a number to calculate it's factorial\n");
  scanf("%d", &number);
  printf("%d! = %ld\n", number, factorial(number));
  getch();
}
 long factorial(int n)
{
  int c;
  long result = 1;
  for (c = 1; c <= n; c++)
  result = result * c;
  return result;
}

---------------------------------------------------------------------------------------------------------------------------------

Factorial program in c using recursion

#include<stdio.h>

#include<conio.h>
long factorial(int);
void main()
{
  int n;
  long f;
  printf("Enter an integer to find factorial\n");
  scanf("%d", &n);
  if (n < 0)
    printf("Negative integers are not allowed.\n");
  else
  {
    f = factorial(n);
    printf("%d! = %ld\n", n, f);
  }
    getch();
}
 long factorial(int n)
{
  if (n == 0)
  return 1;
  else
   return(n * factorial(n-1));
}

------------------------------------------------------------------------------------------------------------
Recursion is a technique in which a function calls itself, for example in above code factorial function is calling itself. To solve a problem using recursion you must first express its solution in recursive form.