Microsoft Fixes Excel Calculation Bug

[Sunite]

Microsoft Fixes Excel Calculation Bug
By Jennifer LeClaire
October 12, 2007 8:17AM

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A calculation bug that crept into Excel 2007 has officially been eliminated this week with Microsoft making a patch available for download. Those not concerned about fixing the Excel calculation issue right away can wait for the patch to be available through Microsoft's update service or through Office 2007's first service pack.

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   Microsoft Relevant Products/Services has fixed an embarrassing error in Excel 2007 -- a major component of the Office 2007 productivity suite. The issue involves miscalculating numbers around 65,535.

The first reported problem revolved around "77.1 x 850," according to Microsoft. But the Excel team's testing, along with additional reports from outsiders, soon revealed this was not the only instance where Excel 2007 would return a value of 100,000 instead of 65,535.

"We are in the process of adding this fix to Microsoft Update so that it will get automatically pushed to users running Excel 2007 or Excel Services 2007," the officials wrote on an Excel developer team blog.

Excel users can download the fix manually or wait until it is released as part of the first service pack for Office 2007. Microsoft has not yet offered a release date for Office 2007 Service Pack 1.

Root of the Problem

Microsoft traced the root of the problem to changes that were made to the Excel calculation logic for the latest version of the software. Excel incorrectly displays the result of a calculation in 12 specific cases.

However, the issue actually is not in the calculation itself. In other words, calculation stored in Excel's memory is correct. The problem is only in the result that is shown in the sheet. The equation "850 x 77.1" will display an incorrect value, but if you then multiply the result by two, you will get the correct answer, Microsoft said.

Of the 9.214*10^18 different floating point numbers that Excel 2007 can store, there are six floating point numbers between 65534.99999999995 and 65535, and six between 65535.99999999995 and 65536 that cause this problem, according to Microsoft.

Consumers can't actually enter these numbers into Excel directly because Excel will round to 15 digits on entry. However, any calculation returning one of those results will have this issue if the results of the calculation are displayed in a cell. No other calculation results are affected.

Sending Pest Control

In other Microsoft news, the company issued a security Relevant Products/Services advisory on Wednesday concerning a URL handling vulnerability in Windows XP and Windows Server 2003 with Internet Explorer 7, which could allow remote code execution. Microsoft said it is investigating public reports of the vulnerability.

"We are not aware of attacks that try to use the reported vulnerability or of customer impact at this time. Microsoft is investigating the public reports," the company said in its security blog. The vulnerability does not affect Windows Vista or any supported editions of Windows where Internet Explorer 7 is not installed.

Microsoft said that upon completion of its investigation, it would take the "appropriate action" to protect its customers, which may include providing a solution through a service pack, our monthly security update release process, or even an out-of-cycle security update.