The bitwise complement of a floating point number's binary representation
IEEE 754 floating point numbers are represented as a sign, a mantissa and an exponent.

It is possible to work with floats at a bit level, but you need to know what you're doing.



Here are some documents which explain further.

http://www.engrng.pitt.edu/hunsaker/3097/floatingpoint.pdf

http://floating-point-gui.de/