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 a 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

: Here we find factorial using for loop.

#include<stdio.h>
#include<conio.h>
 
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();
   return 0;
}

Factorial
Output of code:

Factorial program in c using function

#include<stdio.h>
 
long factorial(int);
 
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));
 
   return 0;
}
 
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>
 
long factorial(int);
 
main()
{
   int num;
   long f;
 
   printf("ENTER A NUMBER TO FIND FACTORIAL :");
   scanf("%d",&num); 
 
   if(num<0)
      printf("NEGATIVE NUMBERS ARE NOT ALLOWED");
   else
   {
      f = factorial(num);
      printf("%d!=%ld",num,f);
   }
   return(0);
}
 
long factorial(int n)
{
   if(n==0)
      return(1);
   else
      return(n*factorial(n-1));
}