A node is created with no parent, and the argument is made to point at the new node. F_createTree() uses the type of its argument to decide what kind of node to create. That is, if the argument is of type eventNode* then an event node is created; if the argument is of type erpNode* then an erp node is created.
The following creates a new event node and sets the run data member of the event node.
eventNode *ev; // initially ev points at nothing F_createTree(ev); // ev is made to point at a new eventNode ev->run = 3444; // the new eventNode is filled with data