In the earlier unit, we have discussed about the arrays. Arrays are data structures of fixed size. Insertion & deletion involves reshuffling of array elements. Thus, arraymanipulation is very time-consuming & inefficient. In this unit, we will illustrate abstract data type-lists, array implementation of lists & linked list implementation, Doubly & Circular linked lists & their applications. In the linked lists, items can be added or removed simply to the end or beginning or even in the middle.