The following example defines a parent and child window. It then uses WPARENT( ) to identify which window is the parent.
CLEAR ALL
CLEAR
DEFINE WINDOW wParent ;
FROM 1,1 TO 20,20 ;
TITLE 'wParent' && Parent window
ACTIVATE WINDOW wParent
DEFINE WINDOW wChild ;
FROM 1,1 TO 10,10 ;
TITLE 'wChild' ;
IN WINDOW wParent && Child window
ACTIVATE WINDOW wChild
WAIT WINDOW 'The parent window is ' + WPARENT( )
RELEASE WINDOW wParent, wChild