Xref: utzoo comp.unix.wizards:17332 comp.lang.c:20013
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.unix.wizards,comp.lang.c
Subject: Re: what does NaN mean out of printf?
Message-ID: <10557@smoke.BRL.MIL>
Date: 19 Jul 89 07:14:15 GMT
References: <20283@adm.BRL.MIL>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Followup-To: comp.lang.c
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 11

In article <20283@adm.BRL.MIL> Leisner.Henr@xerox.com (Marty) writes:
>What does NaN mean out of printf?

Please direct C language questions to the C newsgroup, not a UNIX group.

NaN stands for "Not a Number".  In IEEE Std 754/854 floating-point
arithmetic, there are a set of bit combinations reserved for representing
non-numbers, as well as values for positive and negative infinity.
If you haven't arranged your computation correctly, you can easily find
one of these odd creatures lurking in a floating-point variable instead
of a valid number.