What is a data structure?
       A data structure is a systematic way of organizing and accessing data.

• Primitive data structures:  int, float (double), or char.

• Array: a data structure that store collections of data and allow direct access to the elements by using simple index operations.

• Programming defined data structures:

  • Vector: using index operations but it can grow dynamically to meet the runtime demands of the program.

  • Stack:  first in last out.

  • Queue:  first come first serve.

  • Link List: like a chain, store data by pointers.  One can be linked to next or previous one.  This is good for inserting and deleting.

  • Tree:  a Parent-Child relation for data.   It is not a linear list.  This is good for searching data.