Object-Oriented Programming
Using C++
Third Edition
Chapter 1
An Overview of Object-Oriented
Programming and C++
Objectives
•
•
•
•
•
Learn about the task of programming
Examine programming universals
Explore procedural programming
Be introduced to object-oriented programming
Get started in the C++ programming environment
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Objectives (continued)
• Work with variables and the const qualifier
• Create comments
• Examine the differences between ANSI/ISO C++ and
Standard C++
• Produce C++ output with cout and provide input
with cin
• Begin to work with data structures and classes
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The Task of Programming
• Programming: writing instructions that enable a
computer to carry out tasks
• Programs are frequently called applications
• Learning a computer programming language
requires learning both vocabulary and syntax
• The rules of any language make up its syntax
• Types of errors:
– Syntax errors
– Logical errors
• Semantic errors
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The Task of Programming (continued)
• Machine language: language that computers can
understand; it consists of 1s and 0s
• Interpreter: program that translates programming
language instructions one line at a time
• Compiler: translates entire program at one time
• Run a program by issuing a command to execute
the program statements
• Test a program by using sample data to determine
whether the program results are correct
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Programming Universals
• Language provides methods for directing output to
an object and for sending input into the program
• Variables: named locations in computer memory
– “What is yourAge?”
–
–
–
–
Languages define rules for naming variables
Should have meaningful names
May have only one value at a time
Must be explicitly declared sometimes
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Programming Universals (continued)
• Data type: defines what kind of values may be
stored in a variable and what kind of operations
can be performed on it
– Numeric
• -6
– Character
• ‘&’
– Floating point
• 37.56
– Some languages let you create your own types
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Procedural Programming
• Procedural programs: consist of a series of steps
or procedures that take place one after the other
• Procedural Languages:
–
–
–
–
–
COBOL
BASIC
FORTRAN
RPG
C++
• Procedural programming techniques have evolved
into object-oriented techniques
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Early Procedural Programs
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Control Structures
• Control structures: logic components in programs
• Sequence structure: steps execute one after
another, without interruption
• Selection structure: used to perform different
tasks based on a condition
• Loop structure: repeats actions while some
condition remains unchanged
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Selection Structure
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Loop Structure
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Modularity and Abstraction
• Modules: functions, procedures, methods,
subprograms, subroutines, or simply routines
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Modularity and Abstraction (continued)
• Using the method’s name to cause execution of the
statements within the method is known as calling a
method
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Modularity and Abstraction (continued)
• The program in Figure 1-6 is more concise that the
previous program; it is also more abstract
• Abstraction: paying attention to important
properties while ignoring details
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Encapsulation
• The variables and instructions within a module are
encapsulated, which helps make the module
independent of other modules and reusable
• You can interact with an encapsulated module by
using its interface, without knowing its inner details
• Reusing existing systems improves reliability
• To call a module, you need to know some details
– A better approach is object-oriented programming
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Object-Oriented Programming
• Objects have attributes and can take actions
• You can pass messages to objects, so that they
take action
• The same message works differently when applied
to the various objects
• A method can work appropriately with different
types of data
• Objects can inherit traits of previously created
objects
• Information hiding is more complete than in
procedural programs
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Objects and Classes
•
•
•
•
An object is any thing
A class consists of a category of things
An object is an instance of a class
Is-a relationship:
– “myBlueCerealBowl is a Dish”
• Convention is to begin object names with a
lowercase letter and class names with an
uppercase letter
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Inheritance
• Classes are extensible
• You can create new classes that extend or are
descendents of existing classes
• The descendent classes can inherit all the
attributes of the parent class, or they can override
inappropriate attributes
– In geometry, a Cube is a descendent of a Square
– A Cube has all of a Square’s attributes, plus one
additional characteristic: depth
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Polymorphism
• Programming modules are sometimes needed to
change the way they operate depending on the
context
• Object-oriented programs use polymorphism to
carry out the same operation in a manner
customized to the object
• Without polymorphism, you would have to create
separate module names for a method that cleans a
Dish object, one that cleans a Car object, and one
that cleans a Baby object
– With polymorphism, you create a single “clean”
method
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Getting Started in the C++
Programming Environment
• Use an editor to type your source code
• Compile a program to transform it to machine
language
– Produces object code
• An executable program needs the object code and
code from outside sources to which it refers
– Integrating these outside references is called linking
• When compiling, error messages or warnings
may appear
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Creating a main() Function
• Function parts: header and body
• Function header:
– Return type of the function
– Name of the function
– Types and names of any variables enclosed in
parentheses, and which the function receives
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Working with Variables and the const
Qualifier
• Must provide an identifier to each variable before
you can use it
– Also provide identifiers for functions, structures, and
classes
• Identifiers can include letters, numbers, and
underscores, but they must begin with a letter or
underscore
camel casing
• Examples: Age, lastName, tax_2006,
ready2go, salary, Salary, and SALARY
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Simple Data Types in C++
• int
– For example, 4, -7, 15000
– Also, short int and long int
• char
– For example, ‘A’ or ‘&’
• bool
– For example, true or false
– Some older compilers do not support this data type
• float, double, and long double
– For example, 12.25
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Declaring Variables
• Variables may be declared anywhere but cannot be
used until after they are declared
int main()
{
Or: int myAge, yourAge;
int myAge;
int yourAge;
char myMiddleInitial;
double myMoney, yourMoney;
}
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Declaring Variables (continued)
Lvalue
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The const Qualifier
• A quantity that does not change in a program
should not be declared as a variable
• Instead, it should be a named constant
const double MINIMUM_WAGE = 5.75;
• const is a qualifier: a word that qualifies, or
restricts, the ordinary capabilities of the named
type (such as double)
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Creating Comments
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ANSI/ISO Standard C++
• C++ evolved from a language named C
• 1980s: C++ was designed by Bjarne Stoustrup at
Bell Labs
– Several compilers were developed for C++, and the
language evolved in slightly different ways
• 1990s: a joint committee of the American National
Standards Institute (ANSI) and the International
Standard Organization (ISO) standardized the
syntax
– ANSI/ISO Standard
– Supported by most newer compilers
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Using Libraries, Preprocessor
Directives, and namespace
• Header files: files that contain predefined values
and routines, such as sqrt()
– Usually have no extension or end in .h
– Must include a preprocessor directive in the
program
• Preprocessor directives begin with a pound sign (#)
• #include preprocessor directive tells the compiler to
include a file as part of the finished product
• For example, #include <iostream>
• Namespace: mechanism for grouping features you
want to include in a program
– For example, using namespace std;
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Producing C++ Output
• C++ provides several objects for producing output
• The simplest object is called cout
– The name comes from Console OUTput
– For example, cout<<"Hi there";
– Must include iostream
• And using namespace std; in ANSI/ISO C++
– You can use ’\n’ or endl to insert a newline
character
• cout<<"Hi"<<endl<<"there";
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Producing C++ Output (continued)
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Providing C++ Input
• Interactive programs must provide a way for the
user to enter responses to program prompts
• The cin object fetches values from the keyboard
–
–
–
–
Used with the extraction operator (>>)
For example, cin>>quantity;
Must include iostream
Can enter more than one value:
int score1, score2, score3;
cout<<"Please enter 3 scores. Use a space between them. ";
cin>>score1>>score2>>score3;
– Whitespace consists of any number of spaces, tabs,
and Enter characters
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Providing C++ Input (continued)
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A First Look at Data Structures and
Classes
• Primitive or scalar types: int, char, double
• C++ supports two ways to create your own
complex data types: structures and classes
– For example, you might create an Employee
structure or class with components such as
firstName, lastName, hourlySalary,
numberOfDependents, and hireDate
– The relationship between these fields of the
Employee class is often called a has-a relationship
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A First Look at Data Structures and
Classes (continued)
fields are public
Object-Oriented Programming Using C++, Third Edition
fields are private
38
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You Do It
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Modifying a Program to Accept Input
Values
cout<<"Please enter your credit hours ";
cin>>creditHours;
cout<<"Please enter your grade point average ";
cin>>gradePointAverage;
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Creating a Simple Structure
struct Student
{
int creditHours;
double gradePointAverage;
};
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Summary
• Programming a computer includes:
– Learning the syntax of a programming language
– Resolving logical errors
• Programming languages provide methods for input
and output of variable values
• Procedural programs consist of a series of steps or
procedures that take place one after the other
• Object-oriented programming adds several new
programming concepts including objects, classes,
inheritance, and polymorphism
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Summary (continued)
• You write a C++ program by typing source code
into an editor and compiling the program
• C++ modules are called functions, and each
function contains a header and a body
• C++ variables must be given a type and a name
• Comments are nonexecuting program statements
• A preprocessor directive tells the compiler to do
something before compiling the program
• Use cout and cin to display and read values
• When you create a data structure or class, you
create your own C++ data type
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