NODES outputs a list of two numbers. The first represents the number of nodes of memory currently in use. The second shows the maximum number of nodes that have been in use at any time since the last invocation of NODES. (A node is a small block of computer memory as used by Logo. Each number uses one node. Each non-numeric word uses one node, plus some non-node memory for the characters in the word. Each array takes one node, plus some non-node memory, as well as the memory required by its elements. Each list requires one node per element, as well as the memory within the elements.) If you want to track the memory use of an algorithm, it is best if you invoke GC at the beginning of each iteration, since otherwise the maximum will include storage that is unused but not yet collected.