# Write a program to calculate the factorial of a given number3 min read

Calculating the factorial of a given number is a common programming problem that tests the ability to implement basic mathematical concepts and logical structures. In this article, we will discuss how to write a program to calculate the factorial of a given number using pseudocode.

First, let’s define what a factorial is. The factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example, 5! = 5 x 4 x 3 x 2 x 1 = 120.

To calculate the factorial of a given number, we can use a loop to multiply all positive integers less than or equal to the given number. Here’s the pseudocode for the program:

Let’s go through each step of the pseudocode.

Step 1: We initialize the variable `factorial` to 1, which is the starting point for the multiplication.

Step 2: We use a loop to multiply all positive integers less than or equal to n. We start the loop from 1 and iterate up to n. At each iteration, we multiply the current value of `factorial` with the value of `i` and assign it back to `factorial`. This way, `factorial` gets updated with the product of all positive integers less than or equal to n.

Step 3: We output the final value of `factorial`, which is the factorial of the given number.

Here’s an example implementation of the program in Python:

In this implementation, we use a `for` loop to iterate from 1 to `n`. We use the `range` function to generate a sequence of numbers from 1 to `n`, and then multiply each number with `factorial` and assign the result back to `factorial`. Finally, we return the value of `factorial`.

In conclusion, calculating the factorial of a given number is a fundamental programming problem that involves implementing basic mathematical concepts and logical structures. By using a loop to multiply all positive integers less than or equal to the given number, we can easily calculate the factorial of any non-negative integer.

Here’s how you can implement the pseudocode to calculate the factorial of a given number in Python, Java, and C:

Python:

Java:

C:

In all three languages, we define a function named `factorial` that takes a non-negative integer `n` as input and returns its factorial. We initialize the `factorial` variable to 1 and use a `for` loop to multiply all positive integers less than or equal to `n`. Finally, we return the value of `factorial`.

Note that the syntax of the code may vary slightly depending on the programming language, but the logic and algorithm remain the same.