Programming Languages Chapter 10 Programming From Problem Analysis Program Design Eighth Edition Classes And Data

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C++ Programming: From Problem Analysis to Program Design, Eighth Edition 10-1

Chapter 10

Classes and Data Abstraction

A Guide to this Instructor’s Manual:

We have designed this Instructor’s Manual to supplement and enhance your teaching

experience through classroom activities and a cohesive chapter summary.

This document is organized chronologically, using the same headings that you see in the

textbook. Under the headings, you will find lecture notes that summarize the section, Teacher

Tips, Classroom Activities, and Lab Activities. Pay special attention to teaching tips and

activities geared towards quizzing your students and enhancing their critical thinking skills.

In addition to this Instructor’s Manual, our Instructor’s Resources also contain PowerPoint

Presentations, Test Banks, and other supplements to aid in your teaching experience.

At a Glance

Instructor’s Manual Table of Contents

• Overview

• Objectives

• Teaching Tips

• Quick Quizzes

• Class Discussion Topics

• Additional Projects

• Additional Resources

• Key Terms

C++ Programming: From Problem Analysis to Program Design, Eighth Edition 10-2

Lecture Notes

Overview

Chapter 10 introduces a structured data type called a class, which is specifically

designed to group data and functions. After examining its structure, students will learn

how to create and use classes. The typical members of a class will be discussed,

including accessors, mutators, constructors, and destructors. We will define the

properties of these members, such as private, protected, public, and static.

Students will also learn about abstract data types and how classes are used to implement

them. In the process, they will be introduced to the concept of information hiding.

Finally, we will discuss information hiding as implemented in C++.

Objectives

In this chapter, the student will:

• Learn about classes

• Learn about private, protected, and public members of a class

• Explore how classes are implemented

• Become aware of accessor and mutator functions

• Examine constructors and destructors

• Learn about the abstract data type (ADT)

• Explore how classes are used to implement ADTs

Teaching Tips

Classes

1. Review the concepts of object-oriented design discussed in Chapter 1, including the

definition of an object.

C++ Programming: From Problem Analysis to Program Design, Eighth Edition 10-3

Teaching

Tip

The terms object and class may be confusing to students because they are often

used interchangeably. Because these terms will be referred to throughout the

chapter, emphasize the difference between them before continuing. A class is a

definition of a data type; an object is an instance variable of the class. You might

relate it to the struct type definition and variables declared of that struct

type.

2. Define a class and examine the syntax for declaring a class.

Teaching

Tip

Clarify the concept of grouping data and operations together into one data type

by providing some real-life examples, such as electrical appliances or

transportation vehicles. Discuss the typical operations associated with these

objects.

4. Explain how member access specifiers control access to the members of a class.

Illustrate with the clockType class presented in this section.

Teaching

Tip

Because the clockType class is used throughout this chapter to introduce new

concepts, go over the class definition in detail and verify that students are on

track.

Unified Modeling Language Class Diagrams

1. Use Figure 10-1 to illustrate how to use UML to model the members of a class.

Variable (Object) Declaration

1. Explain how to declare a class variable, or class object/class instance.

2. Describe how memory is allocated for a class, and use Figure 10-2 to illustrate this

concept.

Teaching

Tip

Discuss why it is acceptable to have one physical copy of a member function in

memory, whereas a data variable is allocated memory when an object is

declared.

C++ Programming: From Problem Analysis to Program Design, Eighth Edition 10-4

Accessing Class Members

1. Discuss how to access class members and explain the rules involving access of

private and public members. Illustrate with Example 10-1.

Built-in Operations on Classes

1. Note the built-in operations that are valid for class objects: assignment and member

access.

Teaching

Tip

Mention that most programmers overload conventional operators for the classes

they implement in order to provide the same behaviors for the client.

Assignment Operator and Classes

1. Demonstrate how the assignment operator works with classes using Figure 10-3.

Class Scope

1. Explain the terms automatic and static as they relate to class scope.

2. Discuss the scope of both class objects and class members in a program.

Teaching

Tip

Emphasize that classes generally should not be declared static because it defeats

the purpose of object-oriented programming. However, discuss situations in

which using static classes is preferable. You might consider using an example

from the STL.

Functions and Classes

1. Discuss the rules for classes regarding parameter passing and return types.

Reference Parameters and Class Objects (Variables)

1. Explain how to determine whether to pass classes by value or by reference. Note the use

of constant reference parameters for classes that should not be modified in a called

function.

Teaching

Tip

Note that the guidelines for parameter passing in the two previous sections are

the same as for C++ structs.

C++ Programming: From Problem Analysis to Program Design, Eighth Edition 10-5

Implementation of Member Functions

2. Explain the use of the scope resolution operator in function implementations.

3. Illustrate the process of implementing class member functions by stepping through the

5. Discuss how classes are used in a program. Define the terms client and instance

variables as they relate to program use.

Teaching

Tip

Clarify the term client in terms of the programs your student will write to test

their classes. In most cases, the client will be the test program that contains

main. In other words, this program will instantiate and manipulate a class as a

client.

Accessor and Mutator Functions

1. Define accessor and mutator functions and explain their purpose as member functions in

a class.

3. Illustrate the use of a class in a program with Example 10-2 presented in this section.

Order of public and private Members of a Class

1. Explain the rules regarding the declaration of private and public members of a

class. Use Examples 10-3 through 10-5 to illustrate various orderings of class members.

Teaching

Tip

Discuss the standard conventions for the ordering of public and private

members in a class. Share your own preferences with the class.

Quick Quiz 1

1. What are the two built-in operations that are valid for class objects?

C++ Programming: From Problem Analysis to Program Design, Eighth Edition 10-6

license distributed with a certain product or service or otherwise on a password-protected website for classroom use.

Answer: assignment (=) and member access (.)

2. By default, all members of a class are ____________________ (public/private).

3. True or False: In the definition of a class, you initialize the variable when you declare it.

4. True or False: If a member of a class is a function, it can directly access any member of

the class – member variables and member functions.

Constructors

2. Mention the two types of constructors.

3. Describe the properties of a constructor, including its name, parameters, and return type.

Invoking a Constructor

Invoking the Default Constructor

1. Examine the syntax to invoke the default constructor of a class.

Teaching

Tip

Emphasize that default constructors in C++ cannot be invoked with parentheses.

Note that some programming languages, such as Java, require empty

parentheses.

Invoking a Constructor with Parameters

1. Examine the syntax to invoke a constructor with parameters.

3. Illustrate how constructors are implemented and used in a program with Example 10-6

C++ Programming: From Problem Analysis to Program Design, Eighth Edition 10-7

Constructors and Default Parameters

1. Explain how to implement a constructor with default parameters.

Teaching

Tip

Review the rules for declaring formal parameters in a function (Chapter 6) to

clarify why the clockType constructor with default parameters in this section

can replace two of its previously defined constructors.

Classes and Constructors: A Precaution

1. Explain what happens when a class does not include a default constructor. Discuss the

In-line Initialization of Data Members and the Default Constructor

1. Explain that the C++11 standard allows the initialization of data members when they are

declared in a class. This may eliminate the declaration of the default constructor.

Arrays of Class Objects (Variables) and Constructors

1. Discuss how to initialize an array of class objects by providing the appropriate

constructor(s).

2. Use Figures 10-8 and 10-9 to illustrate the process of assigning values to array

different elements of an array.

C++ Programming: From Problem Analysis to Program Design, Eighth Edition 10-8

Quick Quiz 2

1. What is meant by an automatic class object?

2. True or False: Classes can be passed as parameters to functions either by value or by

reference.

3. In a function definition’s heading, the name of the function is the name of the class,

followed by the ___________________, followed by the function name.

4. What is an accessor function?

Data Abstraction, Classes, and Abstract Data Types

1. Describe the concept of data abstraction and its usefulness in creating robust

applications.

Teaching

Tip

Explain data abstraction by relating the clockType class with an actual alarm

clock. First, separate the implementation details from the operations. When using

the clockType class, who/what is the client? In a real-world clock, which of

these operations would also be abstracted from the client, assuming that the

client is a human being? What additional operations might be provided as public

operations?

3. Use the listType class presented in this section to demonstrate how classes can

represent ADTs. Present the UML diagram for the listType class shown in Figure

10-10.

C++ Programming: From Problem Analysis to Program Design, Eighth Edition 10-9

A struct Versus a class

1. Discuss the difference between a struct and a class. Emphasize the enhanced

Information Hiding

1. Discuss the reasons for separating the specification and implementation details of a

class.

Teaching

Tip

Emphasize that separating the specification of a class from the implementation is

beneficial to programmers as well as clients. Discuss the benefits of restricting

access to a program when the application development involves a large team.

2. Explain how to create separate implementation and header files in C++.

3. Introduce the terms precondition and postcondition. Describe the purpose of including

Executable Code

2. Introduce the terms build, rebuild, and make. Explain the steps that are involved in

creating an executable file with separate header and implementation files.

Teaching

Tip

Ask students to share the type of compiler and/or development environment they

are using at home. Verify that everyone is comfortable with the

compiling/linking steps for their particular environment as well as for any

environment that is available at the school labs.

More Examples of Classes

1. Examine the design, specification, and implementation of the circleType class in

Example 10-8.

C++ Programming: From Problem Analysis to Program Design, Eighth Edition 10–10

3. Examine the design, specification, and implementation of the personType class in

Example 10-10. Correlate this with the UML diagram for this class shown in Figure 10-

11.

Inline Functions

1. C++ allows inline function definitions, i.e., those that occur within the class definition.

2. Inline functions are typically used for very short definitions.

Static Members of a Class

1. Define a static member of a class and describe its purpose.

2. Note the rules for declaring and accessing static members in a class. Use Examples 10-

12 and 10-13 to illustrate.

3. Discuss how memory is allocated for static member variables.

Teaching

Tip

Emphasize that using static members is not a truly object-oriented approach

because the members are not associated with a particular object. However, static

variables are useful for many applications. Discuss situations in which using

static variables is the preferred approach in OOP.

4. Encourage students to work through the “Juice Machine” Programming Example to

consolidate their understanding of the concepts presented in this chapter.

Quick Quiz 3

1. Separating the design details of what an object does from its implementation is called

____________________.

2. The set of values belonging to an ADT is called a(n) ____________________.

3. A(n) ____________________ file contains the specification details of a class.

4. True or False: The implementation file of a class contains the function main.

Class Discussion Topics

1. Why do your students think initializing a class member variable during declaration is

not permitted?

2. This chapter only briefly introduces UML diagrams. Discuss the benefits of using UML

diagrams in real-world applications. Why is it important to design an application before

implementing it?

3. Is it always necessary to provide a default constructor for a class? Why or why not?

Additional Projects

1. Modify the student name/test scores program you created in Chapter 9 to use a class

for the student information instead of a struct. The member variables will be the

2. Modify the capitals program from Chapter 9 and create a countryType class to store

the same information. Provide accessor and mutator methods. This class will contain the

Additional Resources

1. Learn about C++ Classes and Objects:

2. Classes (I):

3. C++ Constructors:

4. Introduction to C++ Class Code and Header Files:

C++ Programming: From Problem Analysis to Program Design, Eighth Edition 10–12

Key Terms

➢ Abstract data type (ADT): a data type that specifies the logical properties without the

implementation details

➢ Build, rebuild, or make: when applied to a project, commands that tell the system to

automatically compile and link all files required to create the executable code

➢ Class: a collection of a fixed number of components with the operations you can

perform on those components

➢ Class object (class instance, object): a class variable

➢ Client: program or software that uses and manipulates the objects of a class

➢ Constant function: a member function that cannot modify member variables of the

➢ Instance variables: non-static data members of a class

➢ Member access operator: the dot (period); used to access a member variable or

function

➢ Members: the components of a class

➢ Mutator function: a member function of a class that modifies the value(s) of the