# C++ Program to find the Factorial of a Number

## Program to find the Factorial of a Number

Here we will discuss how to find the factorial of a number entered by the user in C++ programming language.

Factorial of any number is the product of it and all the positive numbers below it for example factorial of 5 is 120

5!=5 x 4 x 3 x 2 x 1

=120

To find the factorial of a number we will use a for loop.   ## Algorithm:-

1. take an input number
2. Input is stored in an int type variable say num.
3. Initialize fact =1
4. num is checked for being a negative number if true then input is invalid.
5. Otherwise a for loop is started
1. The loop starts with i=num
2. In every loop cycle i is multiplied by fact and its value is decremented by 1.
3. Loop works until i is greater than 0.
6. fact is printed as it is the factorial of the given number.

## C++ Code

```//C++ Program
//Factorial of a number
#include<iostream>
using namespace std;
//main program
int main()
{
//initializing variables
int fact=1,num;
cout<<"Enter the number: "; //user input     cin>>num;
//checking for negative input
if(num<0)
cout<<"Invalid input!!\nEnter whole numbers only";
// for positive numbers
else
{
for(int i=num;i>0;i--)
{
fact*=i;
}
cout<<"Factorial of "<<num<<" is "<<fact;
}
return 0;
}```

### Output

```Enter the number: 3
Factorial of 3 is 6``` 