Abstract: The data format of AutoCAD DWG files and the main steps for developing the interfaces with DWGDirect C++ Libraries are presented in the paper. DWG file consists of five parts: header, entities, tables, blocks and contingency header, and the information storage of each part is briefly given. DWGDirect, a library developed by the Open Design Alliance, can be used to read and write DWG files without AutoCAD platform. With the method, the realization of how to access part entities for a CAD/CAM software is discussed and a part of C++ codes is introduced also.

Key words: computer application, DWGDirect C++, DWG file, AutoCAD