Factorial program in C# with example and logic. l

For Example to find the factorial of a number 6 is 720.

(6!=6*5*4*3*2*1=720)

## How to find factorial?

The factorial of a number denoted as n!.

**Factorial Formula.**

n!=n*(n-1)*(n-2)*…*1

For suppose to find the factorial of a number 6 as based on above formula.

6!=6*(6-1)*(6-2)*(6-3)*(6-4)*(6-5)

=6*5*4*3*2*1

=720

**Notes:**

- The factorial number is product of number in its descending order.
- Factorial of 0 is 0!=1
- No factorial for Negative Number.

## Example of factorial program in C# using for loop

```
using System;
/*
C# example for finding factorial of a number using for loop
*/
class Program
{
static void Main(string[] args)
{
//initialized number by 6
int number = 6;
//initialized factorial by 1
int factorial=1;
```** for (int j = number; j >= 1; j--)
{
factorial = factorial * j;
}**
Console.WriteLine("the factorial of the number " + number + " =" + factorial);
}
}
}

### Output

the factorial of the number 6 = 720

## Example of factorial program in C# using while loop

```
/*
C# example for finding factorial of a number using while loop
*/
class Program
{
static void Main(string[] args)
{
//initialized number by 6
int number = 6;
//initialized factorial by 1
int factorial=1;
int j = number;
```** while (j >= 1)
{
factorial = factorial * j;
j = j - 1;
}**
Console.WriteLine("the factorial of the number " + number + " =" + factorial);
}
}

## Example of factorial program in C# using do-while loop

```
class Program
{
static void Main(string[] args)
{
//initialized number by 6
int number = 6;
//initialized factorial by 1
int factorial=1;
int j = number;
```**do
{
factorial = factorial * j;
j = j - 1;
} while (j >= 1);**
Console.WriteLine("the factorial of the number " + number + " =" + factorial);
}
}

## Example of factorial program in C# using function

```
class Program
{
static void Main(string[] args)
{
//initialized number by 6
int number = 6;
//initialized factorial by 1
int factorial=1;
```**Program p = new Program();
//call the function by passing value to find the factorial
factorial = p.fact(number);**
Console.WriteLine("the factorial of the number " + number + " =" + factorial);
}
**public int fact(int number)
{
int factorial = 1;
int j = number;
while (j >= 1)
{
factorial = factorial * j;
j = j - 1;
}
return factorial;
}**
}

## Example of factorial program in C# using Recursive function

```
class Program
{
static void Main(string[] args)
{
//initialized number by 6
int number = 6;
//initialized factorial by 1
int factorial=1;
Program p = new Program();
factorial = p.fact(number);
Console.WriteLine("the factorial of the number " + number + " =" + factorial);
}
public int fact(int number)
{
if (number==0 || number==1)
{
return 1;
}
else
{
return
```**number * fact(number - 1);**
}
}
}