Path: utzoo!utgpu!watmath!att!tut.cis.ohio-state.edu!cica!iuvax!uxc.cso.uiuc.edu!csd4.milw.wisc.edu!cs.utexas.edu!utastro!bill
From: bill@utastro.UUCP (William H. Jefferys)
Newsgroups: comp.sys.mac
Subject: Bug in EXCEL v. 2.2, and a flame
Keywords: Excel
Message-ID: <4134@utastro.UUCP>
Date: 28 Jul 89 16:56:28 GMT
Organization: U. Texas, Astronomy, Austin, TX
Lines: 46

Nearly two years ago, I reported in this forum on
a bug in Microsoft EXCEL. I also reported the bug
directly to Microsoft, although they never responded
to my letter.

The version was 1.05. The bug was NOT fixed in 1.5,
and I regret to say, it has apparently NOT been fixed
in v. 2.2 either. (I thank Paul McJones [mcjones@src.dec.com]
for verifying this, as I haven't got v. 2.2 yet).

Here is the bug. It shows up on a Mac+ with no coprocessor.
It does NOT show up on a Mac II. I don't know about the SE,
but I expect it will show up there too (anyone want to
try it?)

Compute the square root of 0.999975. On a Plus, EXCEL
gives the incorrect value 0.9999875. The correct value
is 0.9999749992187, a difference of 1.6e-10. This may
not sound like much, but for the application I was
doing when I discovered this, it was highly significant.
Normally, EXCEL gives 16 digit accuracy for the square 
root.

The argument range over which reduced accuracy is obtained
is [0.999975, 0.99999991].

****FLAME ON****

It is inexcusable that Microsoft has had this bug reported
to them nearly two years ago, has put out two major
upgrades, and has STILL not fixed the problem. Although the 
amount of the error is small, in scientific calculations
it can be quite significant, and could easily produce
errors that by going undetected might do considerable
damage. 

Microsoft, are you listening? PLEASE FIX THIS!!!

****FLAME OFF****

Bill Jefferys

-- 
Glend.	I can call spirits from the vasty deep.
Hot.	Why, so can I, or so can any man; But will they come when you
	do call for them?    --  Henry IV Pt. I, III, i, 53