Posted by Rallaz on Mar 18, 2013; 10:03am
URL: https://forum.librecad.org/LibreCAD-DXF-File-Structure-tp5707695p5707718.html

I forgot...

330 group code are "Soft-pointer ID/handle to owner BLOCK_RECORD object" if  are a "normal" entity then value of code 5 of *Model_Space BLOCK_RECORD. In a partial or minimal dxf not needed.

About your "min_line.dxf":
group codes 8, 62, 370 & 6 are "group codes for entities" and must be between "AcDbEntity" and "AcDbLine"

Layer value (8) can be any valid string, all programs that reads dxf create it if not exist

linetype & color (62 & 6) if are BYLAYER not needed like 30 & 31 (z values) defaults to 0