AutoCAD DXF (Drawing Interchange Format, or Drawing Exchange Format) is a CAD data file format developed by Autodesk for enabling data interoperability between AutoCAD and other programs. DXF was introduced in December 1982 as part of AutoCAD 1.0, and was intended to provide an exact representation of the data in the AutoCAD native file format, DWG (Drawing). For many years, Autodesk did not publish specifications, making correct imports of DXF files difficult. Autodesk now publishes the DXF specifications online. Versions of AutoCAD from Release 10 (October 1988) and up support both ASCII and binary forms of DXF. Earlier versions support only ASCII. As AutoCAD has become more powerful, supporting more complex object types, DXF has become less useful. Certain object types, including ACIS solids and regions, are not documented. Other object types, including AutoCAD 2006's dynamic blocks, and all of the objects specific to the vertical market versions of AutoCAD, are partially documented, but not well enough to allow other developers to support them. For these reasons many CAD applications use the DWG format which can be licensed from Autodesk or non-natively from the Open Design Alliance. DXF coordinates are always without dimensions so that the reader or user needs to know the drawing unit or has to extract it from the textual comments in the sheets. File structure ASCII versions of DXF can be read with any text editor. The basic organization of a DXF file is as follows: section General information about the drawing. Each parameter has a variable name and an associated value. section Holds the information for application-defined classes whose instances appear in the , , and sections of the database. Generally does not provide sufficient information to allow interoperability with other programs. section This section contains definitions of named items. Application ID () table Block Record () table Dimension Style () table Layer () table Linetype () table Text style () table User Coordinate System () table View () table Viewport configuration () table section This section contains Block Definition entities describing the entities comprising each Block in the drawing. section This section contains the drawing entities, including any Block References. section Contains the data that apply to nongraphical objects, used by AutoLISP, and ObjectARX applications. section Contains the preview image for the DXF file. The data format of a DXF is called a "tagged data" format, which "means that each data element in the