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Python Program - to calculate factorial of a number using while loop

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💻 Practical Program
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Program to calculate factorial of a number using while loop

📌 Information & Algorithm

Here is a Python program to calculate the factorial of a number using a while loop:

💻 Program Code

num = int(input("Enter a positive integer: "))
factorial = 1
i = 1

while i <= num:
    factorial *= i
    i += 1

print("The factorial of", num, "is", factorial)

                        

🖥 Program Output

Enter a positive integer: 5
The factorial of 5 is 120

                            

📘 Explanation

In this program, we prompt the user to enter a positive integer using the input() function and convert it to an integer using the int() function. We initialize two variables: factorial, which will store the factorial of the number, and i, which we will use to iterate over the numbers from 1 to num.

We use a while loop to iterate over the numbers from 1 to num. In each iteration of the loop, we multiply factorial by i and increment i by 1. This calculates the product of all the numbers from 1 to num, which is the factorial of num.

Finally, we print out the result using the print() function.

This program demonstrates the sequential flow of execution in Python, where the statements are executed in the order in which they appear in the code. The while loop causes the statements inside the loop (i.e., the repeated multiplication of factorial by i and the incrementation of i) to be executed until the condition i <= num becomes False, resulting in the final value of factorial.

📚 Learning Subject

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Improve your coding logic, problem-solving skills and programming confidence by practicing real-world examples with explanations.

🎯 How to learn from this example

First understand the algorithm carefully. Then study the program line-by-line and compare it with the output. Finally, review the explanation section to strengthen your logic and programming understanding.

🔥 Practice suggestion

Rewrite the program without looking at the code. Modify values, conditions or logic and run it again. This helps improve confidence and strengthens coding skills much faster.