Object Oriented Programming (OOP) using C++ - Lecture 1

Object Oriented
Programming using C++
By Mohamed Gamal
© Mohamed Gamal 2024

Resources
• Text Book:
• Object Oriented Programming in C++
• 4th Edition
• By Robert Lafore
• 978-0672323089
• Sams Publisher
• Other Resources
Book Link

The topics of today’s lecture:
Agenda

History of C++
– C++ was developed by Bjarne Stroustrup at Bell Labs in the early 1980s as an
enhancement to C, incorporating object-oriented features.
– It became commercially available in 1985, with its first standard (C++98) published
in 1998.
– Subsequent updates (C++03, C++11, C++14, C++17, and C++20) added significant
features like templates, auto type, lambdas, and concepts, making it a powerful
tool for modern software development
– C++ continues to evolve with ongoing efforts for new standards.
– Its influence extends to languages like C#, Java, and Rust.C++

Object-Oriented Languages
– Some of the most popular Object-oriented Programming languages are:
▪ C++
▪ Java.
▪ smalltalk
▪ Eiffle.
▪ Ruby
▪ Delphi

First C++ Program
#include <iostream>
using namespace std;
int main() {
cout << "Welcome to C++!" << endl;
return 0;
}
cout is declared in this name space

#include <iostream>
int main()
{
const int MAX = 20; //max characters in string
char str[MAX]; //string variable str
cout << "nEnter a string : ";
// cin >> setw(MAX) >> str; // space problem
cin.get(str, MAX); //put string in str (max 19 chars)
// no more than MAX chars
cout << "You entered: " << str;
cout << ", size: " << sizeof(str);
cout << endl;
return 0;
}
Arrays
– An array is a collection of variables of the same types.

#include <iostream>
const int MAX = 2000; //max characters in string
char str[MAX]; //string variable str
int main()
{
cout << "nEnter a string : n";
cin.get(str, MAX, '$'); //terminate with $
cout << "You entered : n" << str << endl;
return 0;
}
Reading Multiple Lines

Structures
– A structure is a collection of variables of different types.
– The variables in a structure can be of different types:
• Some can be int, some can be float, and so on.
• The data items in a structure are called the members of the structure.
struct Car
{
int modelNumber;
int year; // manufacturing year
float price;
};

#include <iostream>
struct Car
{
int modelnumber;
int year;
float price;
};
int main() {
Car car1;
car1.modelnumber = 301;
car1.year = 2019;
car1.price = 217500.00F;
//display structure members
cout << "Model: " << car1.modelnumber << endl;
cout << "Year: " << car1.year << endl;
cout << "Price $: " << car1.price << endl;
return 0;
}

#include <iostream>
struct Car
{
int modelnumber;
int year;
float price;
};
int main() {
Car car1 = { 301, 2019, 217500.00F };
Car car2;
car2 = car1;
// display structure members
return 0;
}

Enumerations
– An enumeration is a list of all possible values, you must give a specific
name to every possible value.
– The first name in the list is given the value 0, the next name is given the
value 1, and so on.
#include <iostream>
enum days_of_week { Sun, Mon, Tue, Wed, Thu, Fri, Sat };
enum pets { cat, dog, mice, canary, turtule };
int main() {
return 0;
}

Overloaded Functions
– The function overloading is in practice two functions have the same
name but their parameter lists are different (in type or in number).
#include <iostream>
// Declarations
void repchar();
void repchar(char);
void repchar(char, int);
int main() {
repchar();
repchar('=');
repchar('+', 30);
return 0;
}

void repchar() // displays 45 asterisks
{
for (int j = 0; j < 45; j++) // always loops 45 times
cout << '*'; // always prints asterisk
cout << endl;
}
void repchar(char ch) // displays 45 copies of specified character
{
for (int j = 0; j < 45; j++) // always loops 45 times
cout << ch; // prints specified character
cout << endl;
}
// displays specified number of copies of specified character
void repchar(char ch, int n)
{
for (int j = 0; j < n; j++) // loops n times
cout << ch; // prints specified character
cout << endl;
}

Namespaces in C++
– Namespaces are used to organize code into logical groups and to prevent name collisions.
#include <iostream>
// Define a namespace called 'MathFunctions'
namespace MathFunctions {
double add(double a, double b) {
return a + b;
}
double subtract(double a, double b) {
return a - b;
}
}
// Define another namespace called 'Utils'
namespace Utils {
void printMessage(const std::string& message) {
std::cout << message << std::endl;
}
}
int main() {
// Use the functions defined in the MathFunctions namespace
double sum = MathFunctions::add(5.0, 3.0);
double difference = MathFunctions::subtract(5.0, 3.0);
// Print the results
std::cout << "Sum: " << sum << std::endl;
std::cout << "Difference: " << difference << std::endl;
// Use the function defined in the Utils namespace
Utils::printMessage("Hello, namespaces!");
return 0;
}

Introduction
– Object-oriented programming (OOP)
▪ The fundamental idea behind object-oriented languages is to combine into a
single unit both data and the functions that operate on that data. Such a unit
is called an object.
▪ An object’s functions, called member functions in C++, typically provide the
only way to access its data.
▪ If you want to read a data item in an object, you call a member function in
the object. It will access the data and return the value to you.
▪ You can’t access the data directly. The data is hidden, so it is safe from
accidental alteration.

Introduction
– Object-oriented programming (OOP)
▪ Encapsulation: encapsulates data (attributes) and functions (behavior) into
packages called classes.
▪ Information Hiding: implementation details are hidden within the classes
themselves.
– Classes
▪ Classes are the standard unit of programming
▪ Objects are instantiated (created) from the class

Structures and Classes
– The only formal difference between class and struct is that in a class the
members are private by default, while in a structure they are public by
default.
struct foo {
int data1;
void func();
};
class foo {
private:
int data1;
public:
void func();
};

An Analogy
– You might want to think of
objects as departments—such as
sales, accounting, personnel, and
so on—in a company.

Characteristics of OOP
– Programs are divided into classes and functions.
– Data is hidden and cannot be accessed by external functions.
– Use of inheritance provides reusability of code.
– New functions and data items can be added easily.
– Data is given more important than functions.
– Data and function are tied together in a single unit known as class.
– Objects communicate each other by sending messages in the form of function.

Car Class Example
Class Objects
Car
Toyota
BMW
Mercedes

Data Hiding
– A key feature of object-oriented programming is data hiding, this means
that data is concealed within a class so that it cannot be accessed
mistakenly by functions outside the class.
– The primary mechanism for hiding data is to put it in a class and make it
private.
▪ Private data or functions can only be accessed from within the class.
▪ Public data or functions, on the other hand, are accessible from outside the class.

Example
#include <iostream>
class car
{
private:
int modelnumber;
int year;
float price;
public:
void setcar(int mn, int yr, float p)
{
modelnumber = mn;
year = yr;
price = p;
}

void showcar()
{
cout << "Model: " << modelnumber << endl;
cout << "Year: " << year << endl;
cout << "Price $: " << price << endl;
}
};
int main() {
car car1; //define object of class car
car1.setcar(301, 2020, 225500.00F); //call member function
car1.showcar(); //call member function
return 0;
}

Constructor
– It’s required that an object can initialize itself when it’s first created,
without requiring a separate call to a member function.
– Automatic initialization is carried out using a special member function
called a constructor.
– A constructor is a member function that is executed automatically
whenever an object is created.
– The constructor has the same name as the class, and no return type is
used for constructors.
(The term constructor is sometimes abbreviated ctor )

Constructor Example
#include <iostream>
class Counter {
private:
unsigned int count;
public:
Counter() { //constructor – Or Counter() : count(0) {}
count = 0;
}
void inc_count() {
count++;
}
int get_count() {
return count;
}
};

int main() {
Counter c1; //define and initialize
cout << "c1 = " << c1.get_count() << endl; //display
c1.inc_count(); //increment c1
cout << "c1 = " << c1.get_count() << endl; //display again
return 0;
}
– The default constructor.

Destructor
– The destructor is a special member function that is called automatically
when an object is destroyed.
– A destructor has the same name as the constructor (which is the same as
the class name) but is preceded by a tilde symbol ( ~ ).
– Destructor does not have a return value and they take no arguments.

Destructor Example
#include <iostream>
class Test {
public:
// Constructor
Test() { cout << "Constructor executed" << endl; }
// Destructor
~Test() { cout << "Destructor executed" << endl; }
};
int main()
{
Test t, t1, t2, t3;
return 0;
}

Overloaded Constructors
#include <iostream>
#include <string.h>
class Person
{
private:
char name[80];
char gender[7];
int age;
public:
Person()
{
strcpy(name, "Mohamed");
strcpy(gender, "Male");
age = 25;
}
Person(char _name[])
{
strcpy(name, _name);
strcpy(gender, "Male");
age = 25;
}

Person(char _name[], char _gender[])
{
strcpy(gender, _gender);
age = 25;
}
Person(char _name[], char _gender[], int _age)
{
strcpy(gender, _gender);
age = _age;
}
~Person() {
cout << "Destructor executed." << endl;
}
void print()
{
cout << "Name: " << name << endl;
cout << "Gender: " << gender << endl;
cout << "Age: " << age << endl;
}
};
int main()
{
Person p1, p2("Hassan", "Male", 32);
p1.print();
p2.print();
return 0;
}

#include <iostream>
#include <string>
class Car {
private:
string make;
double price;
int year;
public:
Car() : make(""), price(0.0), year(0)
{ }
Car(string carMake, double carPrice, int carYear)
{
make = carMake;
price = carPrice;
year = carYear;
}
void setDetails() {
cout << "Enter car make: ";
getline(cin, make);
cout << "Enter car price: ";
cin >> price;
cout << "Enter production year: ";
cin >> year;
}
void displayDetails() const {
cout << "Car Make (Company): " << make << endl;
cout << "Car Price: " << price << endl;
cout << "Car Year: " << year << endl;
}
};
int main() {
Car myCar;
// Get car details
myCar.setDetails();
// Show the car details
cout << "Car Details:n";
myCar.displayDetails();
return 0;
}
Example
Car Class

Static Class Data
– When a member variable is defined as static within a class,
– All the objects created from that class would have access to this variable.
– It would be the same variable for all of the created objects; they would
all see the same count.

#include <iostream>
class foo
{
private:
static int count; // only one data item for all objects
public:
foo() { //increments count when object created
count++;
}
int getcount() { //returns count
return count;
}
};
int foo::count = 0; // definition of 'count'
int main()
{
foo f1, f2, f3; //create three objects
//each object sees the same value
cout << "count is " << f1.getcount() << endl;
return 0;
}

#include <iostream>
#include <cstring> //for strcpy()
class part
{
private:
char partname[30]; //name of widget part
int partnumber; //ID number of widget part
double cost; //cost of part
public:
void setpart(char pname[], int pn, double c)
{
strcpy(partname, pname);
partnumber = pn;
cost = c;
}
void showpart() //display data
{
cout << "nName = " << partname;
cout << ", number = " << partnumber;
cout << ", cost = $" << cost;
}
};
int main()
{
part part1, part2;
part1.setpart("handle bolt", 4473, 217.55); //set parts
part2.setpart("start lever", 9924, 419.25);
cout << "nFirst part : "; //show parts
part1.showpart();
cout << "nSecond part : ";
part2.showpart();
return 0;
}
Complete Example

Object Oriented Programming (OOP) using C++ - Lecture 1

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