PHYSICAL DATA STRUCTURES

 A description of how memory is ordered in order to store information in
 an appropriate way.

 Arrays
 Linked Lists
 Binary Trees

 Nodes, pointers, what is pointing where, how are they connected?

 Defined by its variables, even if you haven't worked out what
 operations it should perform.




ABSTRACT DATA TYPES

A description of how the data structure operates, what you want it to do, irrespective of how it is stored.

Stacks
Queues
Tables

An abstract type is defined by its METHODS, even if you don't how the memory is organized.





PHYSICAL DATA STRUCTURES

Doubly Linked List

class LL {
 private:
  LLN *head, *tail;
};

class LLN {
 private:
  LLN *next, *prev;
  string data;
};