Are the bit patterns of NaNs really hardware-dependent?

Question

I was reading about floating-point NaN values in the Java Language Specification (I\'m boring). A 32-bit float has this bit format:

seee eeee em         


        

Answer 1

Here is a program demonstrating different NaN bit patterns:

public class Test {
  public static void main(String[] arg) {
    double myNaN = Double.longBitsToDouble(0x7ff1234512345678L);
    System.out.println(Double.isNaN(myNaN));
    System.out.println(Long.toHexString(Double.doubleToRawLongBits(myNaN)));
    final double zeroDivNaN = 0.0 / 0.0;
    System.out.println(Double.isNaN(zeroDivNaN));
    System.out
        .println(Long.toHexString(Double.doubleToRawLongBits(zeroDivNaN)));
  }
}

output:

true
7ff1234512345678
true
7ff8000000000000

Regardless of what the hardware does, the program can itself create NaNs that may not be the same as e.g. 0.0/0.0, and may have some meaning in the program.