A linked list is a data structure consisting of a g roup of nodes which together represent a sequence. Under the simplest form, each node is composed of a datum and a reference (in other words, a link ) to the next node in the sequence; more complex variants ad d additional links. This structure allows for efficient insertion or removal of elements from any position in the sequence. Linked lists are among the simplest and most common data structures. They can be used to implement several other common abstract data types, including stacks , queues , etc. though it is not uncommon to implement the other data structures directly without using a list as th e basis of implementation.