Path: utzoo!utgpu!water!watmath!clyde!burl!codas!mtune!rutgers!ames!amelia!msf From: msf@amelia.nas.nasa.gov (Michael S. Fischbein) Newsgroups: comp.lang.c Subject: Re: == vs = Message-ID: <100@amelia.nas.nasa.gov> Date: 11 Jan 88 22:11:32 GMT References: <626@PT.CS.CMU.EDU> Reply-To: msf@amelia.nas.nasa.gov (Michael S. Fischbein) Organization: NASA Langley Research Center, Hampton, VA Lines: 38 In article <626@PT.CS.CMU.EDU> edw@IUS1.CS.CMU.EDU (Eddie Wyatt) writes: > I got this letter that I thought I would public reply to. >From: Michael S. Fischbein >In article <609@PT.CS.CMU.EDU> you write: >>>that had a bug in the software to the degree: for i=1.100 in Fortran ). > >>Do you have a reference for this? > O.K. here it is: >From "Principles of Programming Languages: Design, Evaluation, and >Implementation", Bruce J. MacLennan. pg 90-91 This was gone over in great detail in comp.risks a month or so ago. Of course, I'm SURE that everything in that text is carefully researched and there are absolutely no errors in it, but somehow no one was able find this program. In fact, as was pointed out by a comp.risks contributor, FORTRAN was not used for the probe software; it was all in assembly (check the date, Mr Wyatt). The bug was reported in a newspaper as being a `single character' and, like Parson Weems, a great moral concerning variable names was drawn. It turns out the actual character in error was a `-' and was NOT in the program, but was a logical negation that was overlooked by the programmer translating the symbolic logic into assembly. >BTW those people that claim they don't run into these types of bugs. At least I never said that. Sure, this bites me about once a month. Sometimes I type < instead of <= also. That doesn't mean < should be :< to make all numerical comparisons two characters. mike -- Michael Fischbein msf@prandtl.nas.nasa.gov ...!seismo!decuac!csmunix!icase!msf These are my opinions and not necessarily official views of any organization.