## Factorial Program in C Programming

Factorial program in C Programming Language: C Program code to find and print factorial of a number.

Factorial can be achieved by three methods as follow:

1. Factorial Program using loop,
2. Program using a function to find factorial and
3. Factorial Program 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 Programming using ‘for’ loop

Here we find factorial using ‘for’ loop.

```/**
Write a c program to find the factorial of number using for loop
**/
#include <stdio.h>

int 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);

return 0;
}```

Output:

```Enter a number to calculate it's factorial
6
Factorial of 6 = 720```

## Factorial program in C Programming using function

Here we find factorial using function.

```/**
Write a c program to find factorial of number using Funtion
**/
#include <stdio.h>

long factorial(int);

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 Programming using recursion

Here we find factorial using Recursion.

```/**
Write a c program to find a factorial of number using Recursion
**/
#include<stdio.h>

long factorial(int);

int 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);
}

return 0;
}

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.

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