Convert Decimal to Binary

Convert a non-negative integer from decimal to binary representation.

BeginnerTopic: Basic Python Programs

What You'll Learn

Using loops and modulo for base conversion
Building strings from lists of digits
Understanding how binary representation works

Python Convert Decimal to Binary Program

This program helps you to learn the fundamental structure and syntax of Python programming.

# Program to convert decimal to binary without using bin()

num = int(input("Enter a non-negative integer: "))

if num < 0:
    print("Please enter a non-negative integer.")
elif num == 0:
    print("Binary: 0")
else:
    binary_digits = []
    n = num
    while n > 0:
        remainder = n % 2
        binary_digits.append(str(remainder))
        n //= 2

    binary_digits.reverse()
    binary_str = ''.join(binary_digits)
    print(f"Binary of {num} is {binary_str}")

Output

Enter a non-negative integer: 10
Binary of 10 is 1010

Step-by-Step Breakdown

1Read a non-negative integer.
2Loop while the temporary value is > 0.
3Append each remainder (n % 2) to a list.
4Reverse and join the list into a string.
5Print the final binary string.

Understanding Convert Decimal to Binary

We repeatedly divide the number by 2, collecting remainders:

1.Take remainder of division by 2 → least significant bit.

2.Divide by 2 using integer division.

3.Repeat until the number becomes 0.

4.Reverse the collected bits to get the correct order.

This demonstrates a classic base conversion algorithm.

Note: To write and run Python programs, you need to set up the local environment on your computer. Refer to the complete article Setting up Python Development Environment. If you do not want to set up the local environment on your computer, you can also use online IDE to write and run your Python programs.

Practical Learning Notes for Convert Decimal to Binary

This Python program is part of the "Basic Python Programs" topic and is designed to help you build real problem-solving confidence, not just memorize syntax. Start by understanding the goal of the program in plain language, then trace the logic line by line with a custom input of your own. Once you can predict the output before running the code, your understanding becomes much stronger.

A reliable practice pattern is to run the original version first, then modify only one condition or variable at a time. Observe how that single change affects control flow and output. This deliberate style helps you understand loops, conditions, and data movement much faster than copying full solutions repeatedly.

For interview preparation, explain this solution in three layers: the high-level approach, the step-by-step execution, and the time-space tradeoff. If you can teach these three layers clearly, you are ready to solve close variations of this problem under time pressure.

Convert Binary to Decimal

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