How to convert integer to binary string in C#?

Question

I\'m writing a number converter. How can I convert a integer to a binary string in C# WITHOUT using built-in functions (Convert.ToString does different things b

Answer 1

Here is an elegant solution:

// Convert Integer to binary and return as string
private static string GetBinaryString(Int32 n)
{
    char[] b = new char[sizeof(Int32) * 8];

    for (int i = 0; i < b.Length; i++)
        b[b.Length-1 - i] = ((n & (1 << i)) != 0) ? '1' : '0';

    return new string(b).TrimStart('0');
}

Answer 2

Almost all computers today use two's complement representation internally, so if you do a straightforward conversion like this, you'll get the two's complement string:

public string Convert(int x) {
  char[] bits = new char[32];
  int i = 0;

  while (x != 0) {
    bits[i++] = (x & 1) == 1 ? '1' : '0';
    x >>= 1;
  }

  Array.Reverse(bits, 0, i);
  return new string(bits);
}

That's your basis for the remaining two conversions. For sign-magnitude, simply extract the sign beforehand and convert the absolute value:

byte sign;
if (x < 0) {
  sign = '1';
  x = -x;
} else {
  sign = '0';
}
string magnitude = Convert(x);

For one's complement, subtract one if the number is negative:

if (x < 0)
  x--;
string onec = Convert(x);