# 1. Introduction

Factorial of a non-negative integer, n, is the product of all positive integers less than or equal to n. It is denoted by n!. For instance, the factorial of 5 (denoted as 5!) is 5 x 4 x 3 x 2 x 1 = 120. In this guide, we'll dive into a TypeScript program that calculates the factorial of a given number.

# 2. Program Overview

We will implement a recursive function, named findFactorial, which takes a number as its parameter. This function will compute the factorial of the given number and return the result.

# 3. Code Program

// Recursive function to find the factorial of a number
function findFactorial(num: number): number {
// Base condition
if (num === 0) return 1;
// Recursive call
return num * findFactorial(num - 1);
}

// Testing the function
const numberToFindFactorial: number = 5;
console.log(`Factorial of \${numberToFindFactorial} is: \${findFactorial(numberToFindFactorial)}`);

### Output:

Factorial of 5 is: 120

# 4. Step By Step Explanation

1. We commence by defining the recursive function findFactorial that calculates the factorial of a number.

2. Inside the function, we first check for the base condition. If the given number is 0, the function returns 1 as 0! is 1.

3. If the number is not 0, the function calls itself recursively, multiplying the number with the factorial of the number minus one (num - 1).

4. This recursive approach continues until the base condition is met.

5. To test the function, we find the factorial of 5.

6. After invoking the function with the number 5, it computes the factorial as 120 and outputs the result.