What do these three special floating-point values mean: positive infinity, negative infinity, NaN?

Question

How can we use them in our codes, and what will cause NaN(not a number)?

Answer 1

Positive Infinity is a positive number so large that it can't be represented normally. Negative Infinity is a negative number so large that it cannot be represented normally. NaN means "Not a Number" and results from a mathematical operation that doesn't yield a number- like dividing 0 by 0.

this is not a complete answer(or not clarified enough) - consider this:

double a = Math.pow(10,600) - Math.pow(10,600); //==NaN

mathematically everybody can see it is 0. but for the machine it is an "Infinity" - "Infinity"(of same order) witch is indeed NaN...