AutoCAD DXF (Drawing Exchange Format) is a widespread file exchange format for CAD data developed by Autodesk, Inc., that enables vector data exchange as well as 2D and 3D graphics drawing. Originally introduced in December 1982 as part of AutoCAD 1.0, it was intended to provide an exact representation of the data in the AutoCAD native file format DWG (Drawing), but since Autodesk didn't publish its specifications until many years later, correct imports of DXF files have been a problem since the beginning. Another problem is that DXF typically is dimensionless meaning it doesn't provide all necessary information to permit interoperability with other programs. That's why it's essential that the viewer knows the unit that was used to produce the drawings. With AutoCAD supporting more complex data types over the years, DXF has become less useful but due to its good documentation and with being the lowest common denominator of all CAD based systems, it is still quite popular and therefore also supported by PCB-Investigator.