DWG files are proprietary drawing files created by AutoCAD. They are the drawing. TPC reads and writes DWG files directly.
Because DWG files are free to change with new releases of AutoCAD, they are not backwards compatible. As many surveyors who use CAD will tell you, exchanging DWG files has become a real problem because of all the different versions of AutoCAD.
DXF files, however, are designed to exchange drawings between programs as well as different versions of AutoCAD. A DXF file written for AutoCAD 2000 can still be read by AutoCAD R12 or R14. See DXF files.
TPC can export any drawing in DWG format. You can even choose the version of AutoCAD to write the file for.
You can import DWG files and convert the drawing objects like lines and symbols to survey points.
TPC supports the most common elements of a DWG file, but not all.
Exporting DWG Files
Importing DWG Drawings
DWG Support
Layers
Working with Drawing Objects
Converting Drawing Objects to Survey Points