# Program to Calculate Factorial

## Factorial of Given Number

We will write a C program to calculate the factorial of the given number and the number will be entered by the user. This will help to understand the basic structure of programming. In this program , we will calculate the factorial of given numbers easily by using proper syntax and algorithms. ## Working of Program :

In the program, we will require some numbers from the user to calculate the factorial of that numbers.

### Important Note:

• The factorial of zero will always be 1.
• The factorial of a negative number doesn’t exist.

### Problem 1

Write a program to calculate the factorial of a given number.

• Firstly, we have to enter the number.
• Then print the factorial of the given number.

### Code

Run
```#include<stdio.h>
int main ()
{
int n, fact;
fact = 1;
printf ("Enter the number = ");
scanf ("%d", &n);
while (n > 0)
{
fact = fact * n;
n = n - 1;
}
printf ("The factorial = %d", fact);
return 0;
}```

### Output

```Enter the number = 5
The factorial = 120```

### Note:

In the following we will find the factorial of the given number using do-while() loop.

### Syntax for do – while() loop:

```do
{
// Statements
// Increment / Decrement
}
while(condition)
```
```Problem 2
```

Write a program to calculate the factorial of a given number using do-while() loop.

• Firstly, we have to enter the number.
• Then print the factorial of the given number.

### Code

Run
```#include<stdio.h>
int main ()
{
int n, fact;
fact = 1;
printf ("Enter the number = ");
scanf ("%d", &n);
do
{
fact = fact * n;
n = n - 1;
}
while (n > 0);
printf ("The factorial = %d", fact);
return 0;
}```

### Output

```Enter the number = 6
The factorial = 720```

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