If or the definitions make mathematical sense. Recall that have special binary representations, with all exponent bits equal to 1 and all mantissa bits equal to 0.

If , then the operation is , which makes no mathematical sense.
What we obtain is therefore invalid information.
The result is the **``Not a Number''**, in short **NaN**.
Recall that NaN also have a special binary representation.
NaN is a red flag, which tells the user that something wrong happened with the
program. may or may not be the result of a bug, depending on the
context.

Adrian Sandu 2001-08-26