Blockeditmode: Control to use REFEDIT or BEDIT to edit the block when double click block

Layerdlgmode:  Control the default way when you run LAYER command, set to 1 means load the layer panel, while 0 means to load the classic layer dialog box.

Undosnapshot: Turn on or off the undo / redo preview feature, by default it is turned off to make sure the performance.


Commands:

Sysvdlg: to check the system variable info, including the default value, where to save, and its meaning.