 "A circular linked list"

In the case of a circular doubly linked list, the first node also points to the last node of the list.In some implementations an extra 'sentinel' or 'dummy' node may be added before the first data record or after the last one.This convention simplifies and accelerates some list-handling algorithms, by ensuring that all links can be safely dereferenced and that every list (even one that contains no data elements) always has a "first" and "last" node.