To find out the factorial of a number is an easy task. For example factorial of 4 (4!) is 4 x 3 x 2 x 1 = 24. Now, the question is how do we do that in a computer program? Here, I will show you two ways. We have to note that it was assumed that 0! is 1 so keeping in mind the value, here is the code:

1. Using Simple Function:

#include<iostream>
 
using namespace std;
 
int fact(int n);
 
int main()
{
	int number;
	cout << "Enter a number: "; 	
        cin >> number;
	cout << "Factorial is: " << fact(number) << endl;
        return 0;
}
int fact(int n)  //Factorial using a simple while loop in a function
{
     int result=n;
     if (n == 1 || n == 0)
        return 1;
     else
    {
        while (n>1)
	{
		result *= (n-1);
		n--;
	}
		return result;
	}
}

2. Factorial using a Recursive Function: A recursive function is a function that call itself.

#include<iostream>
 
using namespace std;
int factorial(int n);
int main()
{
	int number;
	cout << "Enter a number: ";
 	cin >> number;
	cout << "Factorial is: " << factorial(number) << endl;
	return 0;
}
 
int factorial(int n)  // using recursive function to find out the factorial of any number.
{
	if (n == 1 || n == 0)
		return 1;
	else
		return (n * factorial(n - 1));
}

I think there are many other way to achieve this problem but the above two are the most common ones.