DXF (Drawing cXchange Format).This format was devised in 1982 to export data from the CAD package AutoCAD.Although AutoCAD uses a different format (DWG) for its own internal use. DXF files are simple Ascii files with a large header containing large amounts of metadata Ordnance Survey Ireland traditionally provided data in DXF format. However, although DXF organizes the data in separate layers, DXF does not include any topology. DXF files can be read by MapInfo. AreVicw. ArcGIS and various other GIS, and layers can even be scparatcd out and saved as a shapefile (sce below). However, decause these files do not contain any topotogy. you generally need to use ArcInfo (or somcthing similer) to creatc the topology (c.g. join the arcs into polygons) before the data can da used in a non-trivial way within a GIS.