###### C++ Decision Making

C++ Program to Find Factorial of a Numbers.

# C++ Program to Find Factorial of a Numbers

In this example, we will learn to Find the Factorial of a number using For Loop and While Loop.

To understand this example, you should have the knowledge of the following C++ programming topics:

## Factorial of a Numbers

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 1: Program to Find Factorial of a given number using for loop.

``````// C++ Program to Find the Factorial of a number using For loop.
#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: 5
Factorial of 5 =120```
##### Working of above Program:

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`.

## Example 2: Program to Find Factorial of a given number using while loop

``````// C++ Program to Find the Factorial of a number using While loop

#include <iostream>
using namespace std;

int main() {
int n, f = 1, i = 1;
cout << "Enter a positive integer: ";
cin >> n;

// Loop to calculate the factorial of a number
while (i <= n) {
f=f*i;
++i;
}
cout << "Factorial of " << n << " = " << f;
return 0;
}``````

Output

```Enter a positive integer: 5
Factorial of 5 =120```

Here variable f is of type `int`.

It is because factorial of a number is always positive, that's why `unsigned` qualifier is added to it.

##### Working of above Program:
• First the computer reads the number to find the factorial of the number from the user.
• Then using while loop the value of ‘i’ is multiplied with the value of ‘f’.
• The loop continues till the value of ‘i’ is less than or equal to ‘n’. Finally the factorial value of the given number is printed.

## Next Example

We hope that this Example helped you develop better understanding of the concept of "Find Factorial" in C++.

Keep Learning : )

In the next Example, we will learn about C++ `Program to Generate Multiplication Table`.