• terminology
  • class--a type of object (like a data type)
  • object--an instance of a class (like a variable)
• class defines the characteristics shared by all of its instances
• each object is different from others by the values of the data stored in them
• operations are common

• Interface
  • define the interface and make it available for all objects to use
  • the implementation and data are hidden
  • the interface is the declarations of the operations
  • it may include other classes, data structures, and constants

• Class versus Object
  • an object is an entity that comes into existence when needed in a program; occupies memory when created and is deleted when it is no longer needed
  • a class is an abstraction--it does not exist in memory but is used as a template to describe attributes and operations for an object

New Way of Thinking about Problem Solving

• planning is now different
• find common objects in the problem and design classes
• identifying classes and objects is one of the hardest parts of OOP programming

Problem Solving Steps

• analyze the problem and the environment
• you want to model the problem
  • identify classes of objects
  • the necessary behavior of the class
  • what is the same about objects in the environment
  • what is different about them