NAN NOT A NUM is only available for floating point numbers.
When the other bit outside the floating point number is 1, the floating point number becomes nan. For example, memory is represented as a Double type of 0xFfffffffffffffffFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
When two extensions of the floating point (ie inf) are calculated, the calculation results become NAN.
