For a better understanding, we always recommend you to learn the basic topics of C programming listed below:

In this C program, we have to find out the Factorial of a given number. So first, we have to check what is Factorial.

The factorial of a number means the product of all the natural numbers up to the given number. An exclamation mark indicates the factorial of a number '**!**'. Let us consider an example: the factorial of **5** is 5! = 5 * 4 * 3 * 2 * 1. Which is equal to **120**.

The logic we applied in this c program is to declare the variable '**i**,' **num**, **fac**. Then read the number from the user and save it into the variable **num**. By using a for loop with the condition "**i <= n**" , calculate **fact = fact * i**. Finally, display the factorial of the number as '**fact**'. the syntax of the if-else statement is

```
if (testExpression) {
// codes inside the body of if
} else {
// codes inside the body of else
}
```

If the test expression is True, then we execute the code inside the `if`

condition, and `else`

parts are skipped. But if the test expression is False, we run the else part and ignore the if condition.

**STEP 1:** Include the header files to use the built-in function in the C program.

**STEP 2:** Declare the integer variable **i, fact, num**, and set **fact=1**.

**STEP 3:** Read the number from the user and save it into the variable **num**.

**STEP 4:** Check if the number is less than or equal to zero `if`

valid, then set '**fact=1**' and do step 6. `Else`

do step 5.

**STEP 5:** By using the `for loop`

with the condition** i<=num**, calculate **fact=fact*i**.

**STEP 6:** Display Factorial of the number num as **fact**.

` ````
#include <stdio.h>
void main() {
int i, fact = 1, num;
printf("Enter the number\n");
scanf("%d", & num);
if (num <= 0)
fact = 1;
else {
for (i = 1; i <= num; i++) /* multiplying each number below the given number to get the factorial */ {
fact = fact * i;
}
} /* End of else */
printf("Factorial of %d =%d\n", num, fact);
} /* End of main() */
```

Enter the number 5 Factorial of 5 = 120