Typical Data Types
	ä Stacks ä Init, Push, Pop ä Lists ä Init, Add, Remove, Head, Tail ä Queues (could be based on priorities) ä Init, Add, Remove ä Sets ä Init, Add, Remove, Union, Intersection ä Trees of various kinds ä Init, Add, Remove ä We can use these in our programs without knowing how the data is represented ä A list could be implemented using a stack, a stack could be implemented using a list and so on…. ä The interface to the data type’s operations is all we need