Appendix A -- Drawing Interchange File Formats
ASCII DXF Files
General DXF File Structure
Essentially a DXF file is composed of pairs of codes and associated values. The codes, known as group codes, indicate the type of value that follows. Using these group code and value pairs, a DXF file is organized into sections, composed of records, which are composed of a group code and a data item. Each group code and value is on its own line in the DXF file.
Each section starts with a group code 0 followed by the string, SECTION. This is followed by a group code 2 and a string indicating the name of the section (for example, HEADER). Each section is composed of group codes and values that define its elements. A section ends with a 0 followed by the string ENDSEC.
It may be helpful to produce a DXF file from a small drawing, print it out, and refer to it while reading the information presented in this section.
The overall organization of a DXF file is as follows:
If you use the Select Objects option of the SAVE and SAVEAS commands, the resulting DXF file contains only the ENTITIES section and the EOF marker. The ENTITIES section contains only the objects you select for output. If you select an insert entity, the corresponding block definition is not included in the output file.