You can use xdata to store any type of information you want. For example, draw an entity (such as a line or a circle), then enter the following code to attach xdata to the entity:
(setq lastent (entget (entlast))) ; Gets the association
; list of definition data
; for the last entity.
(regapp "NEWDATA") ; Registers the
; application name.
(setq exdata ; Sets the variable
'((-3 ("NEWDATA" ; exdata equal to the
(1000 . "This is a new thing!") ; new extended dataâ€”
))) ; in this case, a text
) ; string.
(append lastent exdata)) ; Appends new data list to
; entity's list.
(entmod newent) ; Modifies the entity with the new
; definition data.
To verify that your new xdata has been attached to the entity, enter the following code and select the object:
(entget (car (entsel)) '("NEWDATA"))
This example shows the basic method for attaching extended data to an entity.