The following table provides summary descriptions of the AutoLISP extended data-handling functions.
Extended data-handling functions  | 
                  |
|---|---|
Function  | 
                     Description  | 
                  
(regapp application)  | 
                     Registers an application name with the current AutoCAD drawing in preparation for using extended object data  | 
                  
(xdroom ename)  | 
                     Returns the amount of extended data (xdata) space that is available for an object (entity)  | 
                  
(xdsize lst)  | 
                     Returns the size (in bytes) that a list occupies when it is linked to an object (entity) as extended data  |