Find Factorial of a Number using C++

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.

Source Code

#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.