How code churn is calculated in TFS 2005/2008
Code churn [1] in TFS 2005 and TFS 2008 is calculated using a very simple algorithm: inserted + changed + deleted lines [2].
This is done independently of the contents of the line, which means that everything - incl. comments, blank lines, etc. - is counted.
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[1] http://blogs.msdn.com/mohamedg/archive/2007/12/04/code-churn.aspx
[2] http://msdn2.microsoft.com/en-us/library/ms244698(VS.80).aspx