Frequent contributor Leland Leahy uses this routine to create an AutoCAD layer like defpoints, meaning that it will display on screen but not plot. This code is meant to be called from within another LISP function, and Leland calls it at drawing startup so the nonplotting layer is always available. It also creates a second layer named Xref for the insertion of external references. You can use this as a guide for creating your own layers via code too.