1.  By Wayne Cheng

2.  Introduction  Five Tenets  Terminology  The foundation of C++: Classes

3.  It is the name given to a specific paradigm in the field of programming.  With objects we are creating pieces of code that can stand alone.  You know the box has inputs and outputs but you don’t know what is inside it.

4.  Encapsulation  Data Abstraction  Information Hiding  Inheritance  Polymorphism

5.  The goal is to bind data and the functions that operate on that data together in one “object”.  The functions will be our interface while the data will be hidden in the black box.  Classes in C++ bind data and functions together in objects.

6.  The goal is to force users to interface with the object’s functions rather than accessing data directly.  Data is in the box.  The user can not access the data, he/she must use the defined interface functions to manipulate the data.  Public: elements of class are accessible from outside of class.  Private: restricts access to these functions and data members to this class alone. (as default)  Protected: restricts access to these functions and data member to this class and its children. (Children are classes derived from the current class)

7.  The goal is to prevent the user from seeing how our functions are implemented and exactly what they do.  All the user will see are function prototypes, but no actual implementation.  Multiple file projects: by storing each class implementation in its own file, we can compile and distribute them without allowing users to see the internals of functions.

8. The syntax for a class definition is o class Class_Name { public: Member_Specification 1 Member_Specification 2 … Member_Specification 3 private: Member_Specification_n+1 Member_Specification_n+2 … };

9.  It is a mechanism that allows us to include “Parent” class into a “Child” class.  It just another name for the topic of derived classes.  The goal is code reusability and extensibility.  With it we can reuse code without having to cut and paste it out of our old programs.  It is a major stepping stone on the path to polymorphism.

10.  The goal is to write generic code that can handle multiple objects in the same way.  In code, we can pass multiple objects all as the same base object.  It is refers to the ability to associate multiple meaning to one function name by means of a special mechanism known as “Late Binding”.  We use class hierarchies to allow us to treat child classes as their parent class or grandparent, etc.

11.  Object – A collection of related data and functions bound together.  Method – A function of an object.  Message – A call to an object method. The term “message passing” in reference to OOP you are dealing with method calls.  Member – A method or variable that is part of an object (or class).  Association – an object using another object that exists outside of the first. (Must pass by address or reference)  Aggregation – An object that contains another object.  Generalization – An object that publicly inherits its parent. (Inheritance)  Instance – variable of data type (class or struct).

12.  The class is how we are able to implement OOP concepts in C++.  The class by itself gives us three of our five tenets OOP such are Encapsulation, Data Abstraction and Information Hiding.  It is a technique used in binding functions to the data that they manipulate. (Encapsulation)  It allows us to protect the data from the users direct manipulation. (Data Abstraction)  It allows us to hide the implementation of functions from the user. (Information Hiding)  It defines all its members to be private by default.

13.  A class is a data type whose variables are objects  The definition of a class includes - Description of the kinds of values of the member variables - Description of the member functions  A class description is somewhat like a structure definition plus the member variables

14.  Examine a stack class: two functions and two pieces of data. Class: stack Functions 1. “Push”: it will have one parameter and will return a Boolean value indicating success or failure. The data passed in will be placed at the into the stack at the top. 2. “Pop”: it will have one parameter, a reference, and will return a Boolean value indicating success or failure. The value of the reference will be set to the value at the top of the stack. Data: 1. The first element of data will be the stack itself. 2. The second element of data will be called top and will mark the current position in the stack.

15. ///////////////////////////////////////////////////// //File IntStack.h // This is an integer stack class. ///////////////////////////////////////////////////// class IntStack {public: IntStack(); //the class constructors intpush(int);//the push function prototype intpop(int&);//the pop function prototype private: int stack[10], top;//the definition of calss variables }

16. /////////////////////////////////////////////// //File: IntStack.cpp /////////////////////////////////////////////// #include “IntStack.h”//Import class specification IntStack::IntStack()//The constructor {top = -1;} int IntStack::push(int x)//The push function implementation {if(top == 9) return 0; top++; stack[top] = x; return 1;} int IntStack::pop(int & x)//The pop function implementation {if(top == -1)return 0; x = stack[top]; top--; return 1;}

17. ///////////////////////////////////////////// //pgm.cpp ///////////////////////////////////////////// #include “IntStack.h” #include void main ( ) {IntStack stack; int back; for (intx = 0; x < 12; x++) {cout << “Pushing “ << x << “…”; cout << (stack.push(x)?”Success” : ”Fail”) << endl; } for (x = 0; x < 12; x++) {cout << “Poping…”; (stack.pop(back)? (cout << back) : (cout << “Fail”)) << endl; } }