# Factorial program in C Language

Factorial program in c Language, A factorial program in C is one of the most basic programs that a beginner in the world of programming can learn. Factorial is a mathematical function that is used to calculate the product of all positive integers from 1 to a given number. In this blog post, we will be discussing how to write a factorial program in C.

## What is a Factorial?

A factorial is a mathematical function that is used to calculate the product of all positive integers from 1 to a given number. It is represented by an exclamation mark (!). For example, 5! (5 factorial) is equal to 5 x 4 x 3 x 2 x 1, which is equal to 120.

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The factorial function is commonly used in mathematics and statistics to calculate the number of possible combinations or permutations of a set of objects.

## How to write a Factorial Program in C

Writing a factorial program in C is a simple task that can be accomplished in a few lines of code. The basic logic behind a factorial program is to use a loop to multiply each number from 1 to the given number. Let’s take a look at a simple example of a factorial program in C:

```				```
#include <stdio.h>

int main()
{
int i, n, factorial = 1;
printf("Enter a number to calculate its factorial: ");
scanf("%d", &n);
for (i = 1; i <= n; i++)
{
factorial *= i;
}
printf("Factorial of %d is %d", n, factorial);
return 0;
}

```
```

In this program, we have declared three variables: i, n, and factorial. The variable i is used as a loop counter, n is used to store the number for which we want to calculate the factorial, and factorial is used to store the result of the calculation.

We then ask the user to enter the number for which they want to calculate the factorial using the printf and scanf statements.

After that, we use a for loop to calculate the factorial. The loop runs from 1 to n, and in each iteration, it multiplies the current value of factorial by the loop counter i. This calculation is done using the shorthand operator *=, which multiplies the current value of factorial by i and assigns the result back to factorial.

Finally, we print the result of the calculation using the printf statement.

This program will calculate the factorial of any positive integer that the user enters.

Recursive Factorial Program in C

Another way to write a factorial program in C is by using recursion. Recursion is a technique in programming where a function calls itself repeatedly until a certain condition is met.

Let’s take a look at a simple example of a recursive factorial program in C:

```				```
#include <stdio.h>

int factorial(int n);

int main()
{
int n;
printf("Enter a number to calculate its factorial: ");
scanf("%d", &n);
printf("Factorial of %d is %d", n, factorial(n));
return 0;
}

int factorial(int n)
{
if (n == 0)
return 1;
else
return n * factorial(n - 1);
}

```
```

In this program, we have declared a function called factorial that takes an integer n as its argument and returns an integer value.

The factorial function uses recursion to calculate the factorial. The base case of the recursion is when n is equal to 0, in which case the function returns 1. Otherwise, it multiplies n by the result of calling the factorial function with n – 1 as its argument.

In the main function, we ask the user to enter the number for which they want to calculate the factorial using the printf and scanf statements. We then call the factorial function with the user input as its argument, and print the result using the printf statement.

This program will also calculate the factorial of any positive integer that the user enters, but it uses recursion instead of a loop to perform the calculation.

There are some advantages and disadvantages of using recursion to write a factorial program.