in treeon the other handnodes with single link are not permitted node with one data item must always have two linksunless it' leafin which case it has no links figure shows the possibilities node with two links is called -nodea node with three links is -nodeand node with four links is -nodebut there is no such thing as -node figure -node -node -node nodes in tree tree organization for convenience we number the data items in link from to and the child links from to as shown in figure the data items in node are arranged in ascending key orderby convention from left to right (lower to higher numbersan important aspect of any tree' structure is the relationship of its links to the key values of its data items in binary treeall children with keys less than the node' key are in subtree rooted in the node' left childand all children with keys larger than or equal to the node' key are rooted in the node' right child in tree the principle is the samebut there' more to itall children in the subtree rooted at child have key values less than key all children in the subtree rooted at child have key values greater than key but less than key