C++ Programming Code Examples C++ > Mathematics Code Examples C++ Program to Find Factorial C++ Program to Find Factorial 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. 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. #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; }