You can find a comprehensive listing of group codes in the AutoCAD help system. Here are instructions for finding the Tables section group codes.
1. In AutoCAD, choose Help > AutoCAD Help Topics from the menubar
2. Click on the Contents tab of the Help Topics dialog box, then double click Customization Guide
3. Double click on Appendix C- DXF Group Codes
4. Double click on the Tables Section.
You will see a listing of group code topics listed below. Click on the button next to the topic you are interested in.
APPID
BLOCK_RECORD
DIMSTYLE
LAYER
LTYPE
STYLE
UCS
VIEW
VIEWPORT