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Hi, I’m Brad Feld, a managing director at the Foundry Group who lives in Boulder, Colorado. I invest in software and Internet companies around the US, run marathons and read a lot.

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Excel 100000 Bug

Comments (11)

Software has bugs.  Lots of them.  I am a master bug finder (anyone that has had me bang on their stuff likely has at least one anecdote about this.) 

Today’s “special bug” is a bug in Microsoft Excel 2007.  If you enter =850*77.1 into a cell you will get the result 100000.  Hint – that is an incorrect answer.  I tried it in Google Docs and it resulted in 65535 (the correct answer.)  Hmmm – I wonder what 2^16 is?  Boundary condition anyone?

  • http://blog.surehits.com JonKelly

    Quick note that it should be 100K rather than 10K. Pretty strange bug that seems to be tied to Excel’s cell display rather than the calcing of the value. One of the Digg commenters noted that the VBA value property had it right. Very odd. I’ve definitely seen some strange Excel bugs over the years, though.

  • http://et.cairene.net Robert W. Anderson

    That isn’t a bug, it’s an Easter Egg!

  • http://westcoastgrid.blogspot.com Dan Ciruli

    Wow. That is amazing.

    I have to know – how’d you find that one?

  • http://www.feld.com Brad Feld

    @Dan – making the rounds today – saw it in a couple of places.

  • Lura

    Did you try changing the format to scientific notation before calculating it? I’m curious to see if that would make any difference. I’d try, but I have an ancient version of excel.

  • http://www.feld.com Brad Feld

    @Lura – interesting idea, but it didn’t work. I tried a number of different formats – they all come up 100000.

  • http://www.gnoso.com Peter Waldschmidt

    It must be a bug in the display formatting code. When I use the result in other calculations, the math is correct. Although it has the same error for 65535 and 65536.

    For instance,

    =850*77.1*2 shows 131070
    =850*77.1/850 shows 77.1
    =850*77.1+1 shows 100001
    =850*77.1+2 shows 65537

  • http://www.prototest.com Pete Dignan

    Brad – if your current gig doesn’t work out, you can come work for us at ProtoTest anytime! Or maybe you could be a guest instructor in our Fundamentals of Software Testing class, where we *do* cover boundary values. :-)

  • Dave

    Per your response to Dan: so did YOU discover the bug or did you simply see it mentioned elsewhere? Your post implies, but does not say, that you discovered it yourself.

  • http://www.feld.com Brad Feld

    I wish I could take credit for this one because it’s so delicious but I can’t. Several people emailed me about it and I was digg #1484 (or something like that.) A detailed explanation from Microsoft is at http://blogs.msdn.com/excel/archive/2007/09/25/calculation-issue-update.aspx

  • drop

    Here is even patch for artifical Excel modification:
    http://reverse-engineer.info/

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