# C++ Program to find factorial of a number

In this article, we will discuss another basic and one of the important programs of c++ - **"factorial of a number"**. Before going further, let's understand what a factorial is. Factorial of a number 'x' is a product of all the positive integers up to 'x'. For example, the factorial of 5 is 5*4*3*2*1 = 120.

### So here we will discuss factorial using :

#### 1. For loop, and

2. Recursion

## 1. Using for loop:-

First, we will compute the factorial using for loop. So **Given below is the code to find factorial of a number:-**

`#include<iostream>`

using namespace std;

int main()

{

int n,fact=1;

cout<<" Enter the number : ";

cin>>n;

if (n < 0) cout << "Error! Factorial doesn't exist.";

else {

for (int a=1;a<=n;a++)

fact=fact*a;

}

cout<<"\n Factorial is = "<<factorial<<endl;

return 0;

}

**OUTPUT:-**

Enter the number: 5Factorial is 120

In this above program, we take the positive integer by the user and store it in n variable. Now we check what the user enters a positive integer or negative integer. If the user enters a negative integer we print an error message else we compute the factorial of the number and print it.

## 2. Using recursion:-

Now, we will compute the factorial using recursion. So **Given below is the code to find factorial of a number:**

```
#include<iostream>
using namespace std;
int fact(int n){
if(n==1) return 1;
else return n*fact(n-1);
}
int main(){
int n;
cout<<"\nEnter the number ";
cin>>n;
cout<<"\nFactorial of the number is :: "<<fact(n);
return 0;
}
```

**OUTPUT:-**

Enter the number: 5Factorial is 120

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