Recently a customer contacted us to ask how to tell with what AutoCAD version a received DXF file was saved. In recent versions of AutoCAD, the command line history will list the version when a DWG is opened, but not for DXF files.
Historically a DWG can be opened in Notepad to show the AutoCAD version coded with the first six characters of the file like this:
The problem that arose with the recent case was that there were no indications of the coded version number in a DXF received from another source. That DXF would also not open in AutoCAD. It did, however open in a third party application that was able to save to DWG.
So then, the answer to the question, how can you tell the DWG version a drawing was saved with and what AutoCAD releases save to that version is detailed in WikiPedia.
From that article here is a listing of the most recent versions:
DWG 2000 AC1015 AutoCAD 2000, AutoCAD 2000i, AutoCAD 2002
DWG 2004 AC1018 AutoCAD 2004, AutoCAD 2005, AutoCAD 2006
DWG 2007 AC1021 AutoCAD 2007, AutoCAD 2008, AutoCAD 2009
DWG 2010 AC1024 AutoCAD 2010, AutoCAD 2011, AutoCAD 2012
DWG 2013 AC1027 AutoCAD 2013, AutoCAD 2014
Notice that the DWG format has been changing after every three releases of AutoCAD. As Autodesk's development team introduces new features and variables, they have chosen not to disrupt the file format any more often.
So the new features are planned to coincide with the DWG format changes. Significant changes may therefore need to wait for the drawing database to include new fields to support the new features.