Usually referred to as NaN or Not a Number. Intel supports several NaNs. The NaNs are indicated by a specific exponent. In Intel 's case all of the exponent bits are set to one. These values are primarily use to represent positive and negative infinity.
Most computer systems support floating point in hardware today.
Small embedded computers may not. Hardware simply does it faster, it can be done in software. Super computer systems are often measured in how many floating point operations it can perform in a second. The Intel Ultra computer is rated at over 1,000,000,000,000 floating point operation per second. It is composed of over 9,000 Pentium-pro processors.