The GNode struct represents one node in a N-ary Tree. The data field contains the actual data of the node. The next and prev fields point to the node's siblings (a sibling is another GNode with the same parent). The parent field points to the parent of the GNode, or is NULL if the GNode is the root of the tree. The children field points to the first child of the GNode. The other children are accessed by using the next pointer of each child.