C# Program to Convert Decimal to Binary (Using Bitwise Operator, Array, Function, and Recursion)

Introduction

Decimal to binary conversion is a foundational concept in computer science and programming. Binary numbers are used in low-level programming, networking, embedded systems, and digital electronics.

In this tutorial, we’ll explore multiple ways to write a C# program to convert decimal to binary, using a variety of techniques to suit different learning goals and applications.

 

Problem Statement

Write a C# program to convert a decimal number to its binary equivalent using different methods such as bitwise operations, arrays, user-defined functions, and recursion.

 

Use Cases

• Used in microcontroller programming and digital systems

• Required in binary arithmetic and logical operations

• Helpful for learning number systems and data representation

• Basis for understanding how computers store and interpret data

 

Method 1: Using Bitwise Operator

// C# Program to Convert Decimal to Binary Using Bitwise Operator
using System;

class W3CW
{
    // Main function
    static void Main()
    {
        // Step-1 Declare the input number
        int num = 10;

        // Step-2 Handle the zero case
        if (num == 0)
        {
            Console.WriteLine("Binary: 0");
            return;
        }

        // Step-3 Build binary string using bitwise shift
        string binary = "";
        for (int i = 31; i >= 0; i--)
        {
            int k = num >> i;

            // Check each bit
            if ((k & 1) == 1)
                binary += "1";
            else if (binary.Length > 0) // skip leading zeros
                binary += "0";
        }

        // Step-4 Print the binary output
        Console.WriteLine("Binary: " + binary);
    }
}

Run

Explanation:

• We loop through each bit from MSB to LSB using >> (right shift).

• The bit is extracted using bitwise AND (& 1).

• Leading zeros are ignored until the first 1 is found.

 

Output

 

Method 2: Using Array

// C# Program to Convert Decimal to Binary Using Array
using System;

class W3CW
{
    static void Main()
    {
        // Step-1 Declare an array to store binary digits
        int[] binaryNum = new int[32];

        // Step-2 Input the decimal number
        int num = 10;
        int index = 0;

        // Step-3 Convert to binary using remainder and division
        while (num > 0)
        {
            binaryNum[index] = num % 2;
            num = num / 2;
            index++;
        }

        // Step-4 Print binary digits in reverse
        Console.Write("Binary: ");
        for (int i = index - 1; i >= 0; i--)
        {
            Console.Write(binaryNum[i]);
        }
    }
}

Run

Explanation:

• Remainders of num % 2 are stored in an array.

• We print the array in reverse for correct binary order.

 

Output

 

Method 3: Using a Function

// C# Program to Convert Decimal to Binary Using a Function
using System;

class W3CW
{
    // Function to convert decimal to binary
    static string ConvertToBinary(int num)
    {
        string result = "";
        while (num > 0)
        {
            result = (num % 2) + result;
            num = num / 2;
        }
        return result == "" ? "0" : result;
    }

    static void Main()
    {
        int number = 10;
        Console.WriteLine("Binary: " + ConvertToBinary(number));
    }
}

Run

Explanation:

• We define a reusable function ConvertToBinary().

• The result is built by prepending binary digits.

 

Output

 

Method 4: Using Recursion

// C# Program to Convert Decimal to Binary Using Recursion
using System;

class W3CW
{
    // Recursive function
    static void ConvertToBinary(int num)
    {
        if (num == 0)
            return;

        ConvertToBinary(num / 2);
        Console.Write(num % 2);
    }

    static void Main()
    {
        int number = 10;
        Console.Write("Binary: ");
        if (number == 0)
            Console.Write("0");
        else
            ConvertToBinary(number);
        Console.WriteLine();
    }
}

Run

Explanation:

• Recursive calls divide the number until the base case is met.

• Digits are printed in ascending order during stack unwind.

 

Output

 

Output of the Above Programs

All programs will generate this output for input 10:

 

Summary Table

Method	Uses	Reusability	Suitable For
Bitwise Operator	Bit manipulation	Low	Low-level concepts
Array	Manual storage and iteration	Medium	Beginners
Function	Modular code	High	Code reusability
Recursion	Elegant logic, stack use	Medium	Algorithm learners