converts any integer in the decimal number system to binary number system.

static string DecimalToBinary(int number)
    {
        int remainder;
        string result = string.Empty;
        while (number > 0)
        {
            remainder = number % 2;
            number /= 2;
            result = remainder.ToString() + result;
        }
        return result;
    }
    
    static void Main(string[] args)
    {
        Console.WriteLine(DecimalToBinary(15));
    }