How to convert Decimal to Binary using C#?

Converting decimal numbers to binary in C# can be accomplished using the division and modulus operators. This process involves repeatedly dividing the decimal number by 2 and collecting the remainders, which form the binary representation when reversed.

The algorithm works by dividing the decimal value by 2, storing the remainder (which is always 0 or 1), and continuing until the quotient becomes 0. The binary representation is formed by reading the remainders in reverse order.

Algorithm

The conversion process follows these steps −

1. Divide the decimal number by 2

2. Store the remainder (0 or 1)

3. Update the decimal number to the quotient

4. Repeat until the quotient becomes 0

5. Reverse the collected remainders to get the binary result

Using Manual Division Method

Example

using System;

class DecimalToBinary {
   static void Main(string[] args) {
      int decVal = 48;
      int val;
      string remainders = "";
      
      Console.WriteLine("Decimal = {0}", decVal);
      
      while (decVal >= 1) {
         val = decVal / 2;
         remainders += (decVal % 2).ToString();
         decVal = val;
      }
      
      string binary = "";
      for (int i = remainders.Length - 1; i >= 0; i--) {
         binary += remainders[i];
      }
      
      Console.WriteLine("Binary = {0}", binary);
   }
}

The output of the above code is −

Decimal = 48
Binary = 110000

Using Built-in Convert.ToString() Method

Example

using System;

class DecimalToBinaryBuiltIn {
   static void Main(string[] args) {
      int decimal1 = 48;
      int decimal2 = 25;
      int decimal3 = 100;
      
      Console.WriteLine("Decimal {0} = Binary {1}", decimal1, Convert.ToString(decimal1, 2));
      Console.WriteLine("Decimal {0} = Binary {1}", decimal2, Convert.ToString(decimal2, 2));
      Console.WriteLine("Decimal {0} = Binary {1}", decimal3, Convert.ToString(decimal3, 2));
   }
}

The output of the above code is −

Decimal 48 = Binary 110000
Decimal 25 = Binary 11001
Decimal 100 = Binary 1100100

Using Recursive Approach

Example

using System;

class RecursiveBinary {
   static string DecimalToBinary(int n) {
      if (n == 0) return "0";
      if (n == 1) return "1";
      
      return DecimalToBinary(n / 2) + (n % 2);
   }
   
   static void Main(string[] args) {
      int[] numbers = {48, 15, 7, 32};
      
      foreach (int num in numbers) {
         Console.WriteLine("Decimal {0} = Binary {1}", num, DecimalToBinary(num));
      }
   }
}

The output of the above code is −

Decimal 48 = Binary 110000
Decimal 15 = Binary 1111
Decimal 7 = Binary 111
Decimal 32 = Binary 100000

Comparison of Methods

Conclusion

Converting decimal to binary in C# can be achieved through multiple approaches: manual division with remainders, the built-in Convert.ToString() method, or recursive functions. The Convert.ToString() method is most efficient for production use, while manual implementation helps understand the underlying algorithm.