Decimal to Binary Converter in C, C++, Java & Python – Code with Explanation & Examples in Short and Simple

   

C Program

#include <stdio.h>
void toBinary(int n) {
    if (n > 1) toBinary(n/2);
    printf("%d", n%2);
}

C Output

Input: 10  
Output: 1010

C++ Program

#include <iostream>
using namespace std;
void toBinary(int n) {
    if (n > 1) toBinary(n/2);
    cout << n%2;
}

C++ Output

Input: 7  
Output: 111

JAVA Program

void toBinary(int n) {
    if (n > 1) toBinary(n / 2);
    System.out.print(n % 2);
}

JAVA Output

Input: 5  
Output: 101

Python Program

def to_binary(n):
    if n > 1:
        to_binary(n // 2)
    print(n % 2, end='')

Python Output

Input: 13  
Output: 1101

Explanation in Detail

Example

If we consider the number 13 and express it in binary:

13 ÷ 2 = 6 remainder 1

6 ÷ 2 = 3 remainder 0

3 ÷ 2 = 1 remainder 1

1 ÷ 2 = 0 remainder 1

Now, if we flip the remainders from the bottom to the top: 1101

Hence, binary of 13 is 1101.

Real-Life Analogy

Imagine exchanging currency for coins. Suppose you have ₹13, and you can only use ₹8, ₹4, ₹2, and ₹1 coins (which are all powers of 2), you'll pay:

₹8 → yes (now 5 left)

₹4 → yes (now 1 left)

₹2 → no

₹1 → yes

That is saying:

8 (2³): 1

4 (2²): 1

2 (2¹): 0

1 (2⁰): 1

Which results in binary: 1101

Why It Matters

Conversion from decimal to binary is at the heart of computer science. Computers work in binary — everything that you type in a high-level language is ultimately converted into binary operations (0s and 1s).

Learning about this process solidifies your understanding of:

How low-level machine code operates

How bit manipulation occurs

How memory is accessed

It's also a fantastic introduction to recursion, as evident in our solution.

What You Learn from This

You learn the recursive method of dividing up problems into smaller components. You learn about number base systems — an essential component of digital logic and computer architecture.

It teaches you:

How to think in binary

How to construct solutions by adding remainders and division

Recursive programming logic

Interview Relevance and Real Projects

The question is most often requested in interviews as a warm-up or an extension of a larger number system problem. Interviewers can ask follow-ups such as:

Convert binary to decimal

Count number of 1s in binary

Reverse binary bits

Real-life applications include:

Binary encoding of data

Bitmasking and encryption

Microcontroller and low-level programming

SEO-Optimized Explanation

Converting decimal to binary is one of the most fundamental abilities in computer science and programming. One does it by dividing the decimal number repeatedly by 2 and storing the remainders in reverse order, which constitutes the binary form. Whether you’re learning recursion, building number system converters, or preparing for interviews, understanding decimal to binary logic in C, C++, Java, and Python enhances your problem-solving ability. It’s widely used in computer architecture, bit manipulation problems, embedded systems, and real-time data processing. By mastering this logic, students and developers can confidently work on core programming problems and system-level tasks.