**The factorial of a positive integer n is equal to 1*2*3*…n. You will learn to calculate the factorial of a number using for loop in this example.**

**The factorial of a positive integer n is equal to 1*2*3*…n. You will learn to calculate the factorial of a number using for loop in this example.**

For any positive number `n`, it’s factorial is given by:

factorial = 1*2*3...*n

Factorial of negative number cannot be found and factorial of 0 is 1.

In this program below, user is asked to enter a positive integer. Then the factorial of that number is computed and displayed in the screen.

## Example: Find Factorial of a given number

#include <iostream> using namespace std; int main() { unsigned int n; unsigned long long factorial = 1; cout << "Enter a positive integer: "; cin >> n; for(int i = 1; i <=n; ++i) { factorial *= i; } cout << "Factorial of " << n << " = " << factorial; return 0; }

**Output**

Enter a positive integer: 12 Factorial of 12 = 479001600

Here variable `factorial` is of type `unsigned long long`

.

It is because factorial of a number is always positive, that’s why `unsigned`

qualifier is added to it.

Since the factorial a number can be large, it is defined as `long long`

.