xpp {

/* Define the ancestor class XPlant */

class XPlant {

construct {

public:

<Num upd="false">100</Num>

}

public:

int iAge = 5;

}

/* Define the XTree class which inherits from XPlant but adds nothing else */

class XTree : XPlant {}

/* Instantiate the MyTree object as an instance of XTree */

node(XTree) MyTree;

/* Write the iAge member of MyTree in a sentence */

xout("\r\nMyTree's age is " + MyTree.iAge + " years old.");

/* Write the upd attribute of the Num child node of the MyTree object */

xout("\r\nMyTree/Num's upd flag is " + $MyTree/Num.upd);

/* Assign the Barn node to be the new value of MyTree */

MyTree = $<Barn>500</Barn>;

}