Government Polytechnic, Muzaffarpur. Name of the Lab: OBJECT ORIENTED PROGRAMMING

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1 Government Polytechnic, Muzaffarpur. Name of the Lab: OBJECT ORIENTED PROGRAMMING THROUGH C++ Practical: OOPS THROUGH C++ Subject Code: PROGRAM NO.1 Programming exercise on executing a Basic C++ Program. Object oriented programming As the name suggests uses objects in programming. Object oriented programming aims to implement real world entities like inheritance, hiding, polymorphism etc in programming. The main aim of OOP is to bind together the data and the functions that operates on them so that no other part of code can access this data except that function. When we consider a C++ program, it can be defined as a collection of objects that communicate via invoking each other's methods. Let us now briefly look into what a class, object, methods, and instant variables mean. Object Objects have states and behaviors. Example: A dog has states - color, name, breed as well as behaviors - wagging, barking, eating. An object is an instance of a class. Class A class can be defined as a template/blueprint that describes the behaviors/states that object of its type support. Methods A method is basically a behavior. A class can contain many methods. It is in methods where the logics are written, data is manipulated and all the actions are executed. Instance Variables Each object has its unique set of instance variables. An object's state is created by the values assigned to these instance variables. There are following concepts of OOPS: 1. Class 2. Object 3. Inheritance 4. Data Encapsulation 5. Data Abstractions 6. Polymorphism

2 1) Class Class is the template of an object. That logically encapsulates data members and member functions into a single unit. Classes are data type based on which objects are created. 2) Object Object is a basic unit of OOPS. It has unique name. An object represents a particular instance of a class. We can create more than one objects of a class. The size of class is size of total number of data members of class. 3) Inheritance Inheritance is the process of creating new class from existing class or base class. By using the concept of Inheritance, we can use implemented (existing) features of a class into another class). Base class is also known as parent class or super class. The new class that is formed is called derived class. The derived class is also known as sub class or child class. Inheritance is basically used for reducing the overall code size of the program. 4) Data Encapsulation Data encapsulation combines data members and member functions into a single unit that is called class. The advantage of encapsulation is that data cannot access directly. It is only accessible through the member functions of the class. 5) Data Abstraction Data abstraction specifies hiding the implementation detail for simplicity. It increases the power of programming language by creating user define data types. 6) Polymorphism Polymorphism is basic and important concept of OOPS. Polymorphism specifies the ability to assume several forms. It allows routines to use variables of different types at different times. In C++, an operator or function can be given different meanings or functions. Polymorphism refers to a single function or multi-functioning operator performing in different ways.

3 C++ Program Structure Let us look at a simple code that would print the words Hello World. #include <iostream> using namespace std; // main() is where program execution begins. int main() cout << "Hello World"; // prints Hello World return 0; Let us look at the various parts of the above program The C++ language defines several headers, which contain information that is either necessary or useful to your program. For this program, the header <iostream> is needed. The line using namespace std; tells the compiler to use the std namespace. Namespaces are a relatively recent addition to C++. The next line '// main() is where program execution begins.' is a single-line comment available in C++. Single-line comments begin with // and stop at the end of the line. The line int main() is the main function where program execution begins. The next line cout << "This is my first C++ program."; causes the message "This is my first C++ program" to be displayed on the screen. The next line return 0; terminates main( )function and causes it to return the value 0 to the calling process.

4 Program: Sum of two no. #include <iostream> using namespace std; int main() int firstnumber, secondnumber, sumoftwonumbers; cout << "Enter two integers: "; cin >> firstnumber >> secondnumber; // sum of two numbers in stored in variable sumoftwonumbers sumoftwonumbers = firstnumber + secondnumber; // Prints sum cout << firstnumber << " + " << secondnumber << " = " << sumoftwonumbers; return 0; Output Enter two integers: = 9

5 PROGRAM NO.2 Programming Exercise on Control Statement (if-else, else-if ladder) IF-ELSE The if...else statement executes two different codes depending upon whether the test expression is true or false. Sometimes, a choice has to be made from more than 2 possibilities. Program: Check Whether Number is Even or odd using if else #include <iostream> using namespace std; int main() int n; cout << "Enter an integer: "; cin >> n; if ( n % 2 == 0) cout << n << " is even."; else cout << n << " is odd."; return 0; Output

6 Enter an integer: is odd. Nested if...else The nested if...else statement allows you to check for multiple test expressions and execute different codes for more than two conditions. Syntax of Nested if...else if (testexpression1) // statements to be executed if testexpression1 is true else if(testexpression2) // statements to be executed if testexpression1 is false and testexpression2 is true else if (testexpression 3) // statements to be executed if testexpression1 and testexpression2 is false and testexpression3 is true.. else // statements to be executed if all test expressions are false Program: C++ Nested if...else // Program to check whether an integer is positive, negative or zero #include <iostream> using namespace std; int main() int number; cout << "Enter an integer: "; cin >> number; if ( number > 0) cout << "You entered a positive integer: " << number << endl; else if (number < 0) cout<<"you entered a negative integer: " << number << endl; else

7 cout << "You entered 0." << endl; cout << "This line is always printed."; return 0; Output Enter an integer: 0 You entered 0. This line is always printed.

8 PROGRAM NO.3 Programming exercise on loop Control Statement (for, while, do while) For Loop: A for loop is a repetition control structure which allows us to write a loop that is executed a specific number of times. The loop enables us to perform n number of steps together in oneline. Syntax: for (initialization expr; test expr; update expr) // body of the loop // statements we want to execute Program: Sum of Natural Numbers using For loop include <iostream> using namespace std; int main() int n, sum = 0; cout << "Enter a positive integer: "; cin >> n; for (int i = 1; i <= n; ++i) sum += i; cout << "Sum = " << sum; return 0; Output Enter a positive integer: 50 Sum = 1275 This program assumes that user always enters positive number. If user enters negative number, Sum = 0 is displayed and program is terminated.

9 Do-while: In do while loops also the loop execution is terminated on the basis of test condition. The main difference between do while loop and while loop is in do while loop the condition is tested at the end of loop body, i.e do while loop is exit controlled whereas the other two loops are entry controlled loops. Note: In do while loop the loop body will execute at least once irrespective of test condition. Syntax: initialization expression; do // statements update_expression; while (test_expression); C++ Program to compute factorial of a number #include <iostream> using namespace std; int main() int number, i = 1, factorial = 1; cout << "Enter a positive integer: "; cin >> number; while ( i <= number) factorial *= i; //factorial = factorial * i; ++i; cout<<"factorial of "<< number <<" = "<< factorial; return 0; Output Enter a positive integer: 4 Factorial of 4 = 24

10 PROGRAM NO.4 Programming exercise on Function Depending on whether a function is predefined or created by programmer; there are two types of function: Library Function User-defined Function Library Function Library functions are the built-in function in C++ programming. Programmer can use library function by invoking function directly; they don't need to write it themselves. Example: Library Function #include <iostream> #include <cmath> using namespace std; int main() double number, squareroot; cout << "Enter a number: "; cin >> number; // sqrt() is a library function to calculate square root squareroot = sqrt(number); cout << "Square root of " << number << " = " << squareroot; return 0; Output Enter a number: 26 Square root of 26 = In the example above, sqrt() library function is invoked to calculate the square root of a number. Notice code #include <cmath> in the above program. Here, cmath is a header file. The function definition of sqrt()(body of that function) is present in the cmath header file. You can use all functions defined in cmath when you include the content of file cmath in this program using #include <cmath>

11 User-defined Function C++ allows programmer to define their own function. A user-defined function groups code to perform a specific task and that group of code is given a name(identifier). When the function is invoked from any part of program, it all executes the codes defined in the body of function. Example : User Defined Function C++ program to add two integers. Make a function add() to add integers and display sum in main() function. #include <iostream> using namespace std; // Function prototype (declaration) int add(int, int); int main() int num1, num2, sum; cout<<"enters two numbers to add: "; cin >> num1 >> num2; // Function call sum = add(num1, num2); cout << "Sum = " << sum; return 0; // Function definition int add(int a, int b) int add; add = a + b; // Return statement return add; Output Enters two integers: 8-4 Sum = 4

12 Program: Prime Numbers Between two Intervals using function #include <iostream> using namespace std; int checkprimenumber(int); int main() int n1, n2; bool flag; cout << "Enter two positive integers: "; cin >> n1 >> n2; "; cout << "Prime numbers between " << n1 << " and " << n2 << " are: for(int i = n1+1; i < n2; ++i) // If i is a prime number, flag will be equal to 1 flag = checkprimenumber(i); if(flag) cout << i << " "; return 0; // user-defined function to check prime number int checkprimenumber(int n) bool flag = true; for(int j = 2; j <= n/2; ++j) if (n%j == 0) flag = false; break; return flag;

13 Output Enter two positive integers: Prime numbers between 12 and 55 are: To print all prime numbers between two integers, checkprimenumber() function is created. This function checks whether a number is prime or not. All integers between n1 and n2 are passed to this function. If a number passed to checkprimenumber() is a prime number, this function returns true, if not the function returns false.

14 PROGRAM NO.5 Programming exercise on creating classes and their object. C++ Class Before you create an object in C++, you need to define a class. A class is a blueprint for the object. We can think of class as a sketch (prototype) of a house. It contains all the details about the floors, doors, windows etc. Based on these descriptions we build the house. House is the object. As, many houses can be made from the same description, we can create many objects from a class. How to define a class in C++? A class is defined in C++ using keyword class followed by the name of class. The body of class is defined inside the curly brackets and terminated by a semicolon at the end. class classname // some data // some functions ; Example: Class in C++ class Test private: int data1; float data2; public: void function1() data1 = 2; ; float function2() data2 = 3.5; return data2;

15 C++ Objects When class is defined, only the specification for the object is defined; no memory or storage is allocated. To use the data and access functions defined in the class, you need to create objects. Syntax to Define Object in C++ classname objectvariablename; You can create objects of Test class (defined in above example) as follows: class Test private: int data1; float data2; public: void function1() data1 = 2; ; float function2() data2 = 3.5; return data2; int main() Test o1, o2; Here, two objects o1 and o2 of Test class are created. In the above class Test, data1 and data2 are data members and function1() and function2() are member functions.

16 Example: Object and Class in C++ Programming // Program to illustrate the working of objects and class in C++ Programming #include <iostream> using namespace std; class Test private: int data1; float data2; public: void insertintegerdata(int d) data1 = d; cout << "Number: " << data1; ; float insertfloatdata() cout << "\nenter data: "; cin >> data2; return data2; int main() Test o1, o2; float seconddataofobject2; o1.insertintegerdata(12); seconddataofobject2 = o2.insertfloatdata(); cout << "You entered " << seconddataofobject2; return 0; Output Number: 12 Enter data: 23.3 You entered 23.3

17 PROGRAM NO.6 Programming exercise to demonstrated constructor and destructor. A constructor is a special type of member function that initialises an object automatically when it is created. Compiler identifies a given member function is a constructor by its name and the return type. Constructor has the same name as that of the class and it does not have any return type. Also, the constructor is always public. Example: Constructor in C++ Calculate the area of a rectangle and display it. #include <iostream> using namespace std; class Area private: int length; int breadth; public: // Constructor Area(): length(5), breadth(2) void GetLength() cout << "Enter length and breadth respectively: "; cin >> length >> breadth; int AreaCalculation() return (length * breadth); ; void DisplayArea(int temp) cout << "Area: " << temp; int main() Area A1, A2; int temp;

18 A1.GetLength(); temp = A1.AreaCalculation(); A1.DisplayArea(temp); cout << endl << "Default Area when value is not taken from user" << endl; temp = A2.AreaCalculation(); A2.DisplayArea(temp); return 0; Output Enter length and breadth respectively: 6 7 Area: 42 Default Area when value is not taken from user Area: 10 \

19 Destructor The destructor is a special member function which is called automatically when the object goes out of scope. Program Class class_name public: `class_name() //Destructor Example // Header Files #include<iostream> #include<conio.h> //Standard Namespace Declaration using namespace std; class BaseClass // Class Name public: //Constructor of the BaseClass BaseClass() cout << "Constructor of the BaseClass : Object Created"<<endl; //Destructor of the BaseClass ~BaseClass() cout << "Destructor of the BaseClass : Object Destroyed"<<endl; ; int main () // Object Declaration for BaseClass BaseClass des; // Wait For Output Screen getch(); //Main Function return Statement return 0; Sample Output Constructor of the BaseClass : Object Created Destructor of the BaseClass : Object Destroyed

20 PROGRAM NO.7 Programming exercise on operator overloading. In C++, it's possible to change the way operator works (for user-defined types). This is done by operator overloading feature. How to overload operators in C++ programming To overload an operator, a special operator function is defined inside the class as: class classname public returntype operator symbol (arguments) ; Here, returntype is the return type of the function. The returntype of the function is followed by operator keyword. Symbol is the operator symbol you want to overload. Like: +, <, -, ++ You can pass arguments to the operator function in similar way as functions.

21 Example: Operator overloading in C++ Programming #include <iostream> using namespace std; class Test private: int count; public: Test(): count(5) ; void operator ++() count = count+1; void Display() cout<<"count: "<<count; int main() Test t; // this calls "function void operator ++()" function ++t; t.display(); return 0; Output Count: 6 This function is called when ++ operator operates on the object of Test class (object t in this case). In the program,void operator ++ () operator function is defined (inside Test class). This function increments the value of count by 1 for t object.

22 PROGRAM NO.8 Programming exercise to illustrate concept of Inheritence One of the most important concepts in object-oriented programming is that of inheritance. Inheritance allows us to define a class in terms of another class, which makes it easier to create and maintain an application. This also provides an opportunity to reuse the code functionality and fast implementation time. When creating a class, instead of writing completely new data members and member functions, the programmer can designate that the new class should inherit the members of an existing class. This existing class is called the baseclass, and the new class is referred to as the derived class. The idea of inheritance implements the is a relationship. For example, mammal IS-A animal, dog IS-A mammal hence dog IS-A animal as well and so on. Base and Derived Classes A class can be derived from more than one classes, which means it can inherit data and functions from multiple base classes. To define a derived class, we use a class derivation list to specify the base class(es). A class derivation list names one or more base classes and has the form class derived-class: access-specifier base-class Where access-specifier is one of public, protected, or private, and base-class is the name of a previously defined class. If the access-specifier is not used, then it is private by default.

23 Example: Create game characters using the concept of inheritance. #include <iostream> using namespace std; class Person public: string profession; int age; ; Person(): profession("unemployed"), age(16) void display() cout << "My profession is: " << profession << endl; cout << "My age is: " << age << endl; walk(); talk(); void walk() cout << "I can walk." << endl; void talk() cout << "I can talk." << endl; // MathsTeacher class is derived from base class Person. class MathsTeacher : public Person public: void teachmaths() cout << "I can teach Maths." << endl; ; // Footballer class is derived from base class Person. class Footballer : public Person public: void playfootball() cout << "I can play Football." << endl; ; int main() MathsTeacher teacher; teacher.profession = "Teacher"; teacher.age = 23; teacher.display(); teacher.teachmaths(); Footballer footballer; footballer.profession = "Footballer"; footballer.age = 19; footballer.display(); footballer.playfootball(); return 0;

24 Output My profession is: Teacher My age is: 23 I can walk. I can talk. I can teach Maths. My profession is: Footballer My age is: 19 I can walk. I can talk. I can play Football. In this program, Person is a base class, while MathsTeacher and Footballer are derived from Person. Person class has two data members - profession and age. It also has two member functions - walk() and talk(). Both MathsTeacher and Footballer can access all data members and member functions of Person. However, MathsTeacher and Footballer have their own member functions as well: teachmaths() and playfootball() respectively. These functions are only accessed by their own class. In the main() function, a new MathsTeacher object teacher is created. Since, it has access to Person's data members, profession and age of teacher is set. This data is displayed using the display() function defined in the Person class. Also, the teachmaths() function is called, defined in the MathsTeacher class. Likewise, a new Footballer object footballer is also created. It has access to Person's data members as well, which is displayed by invoking the display() function. The playfootball()function only accessible by the footballer is called then after.

25 Types of Inheritance When deriving a class from a base class, the base class may be inherited through public, protected or private inheritance. The type of inheritance is specified by the access-specifier as explained above. We hardly use protected or private inheritance, but public inheritance is commonly used. While using different type of inheritance, following rules are applied Public Inheritance When deriving a class from a public base class, public members of the base class become public members of the derived class and protected members of the base class become protected members of the derived class. A base class's privatemembers are never accessible directly from a derived class, but can be accessed through calls to the public and protected members of the base class. Protected Inheritance When deriving from a protected base class, public and protected members of the base class become protected members of the derived class. Private Inheritance When deriving from a private base class, public and protected members of the base class become private members of the derived class.

26 Example of public, protected and private inheritance in C++ class base public: int x; protected: int y; private: int z; ; class publicderived: public base // x is public // y is protected // z is not accessible from publicderived ; class protectedderived: protected base // x is protected // y is protected // z is not accessible from protectedderived ; class privatederived: private base // x is private // y is private // z is not accessible from privatederived In the above example, we observe the following things: base has three member variables: x, y and z which are public, protected and private member respectively. publicderived inherits variables x and y as public and protected. z is not inherited as it is a private member variable of base. protectedderived inherits variables x and y. Both variables become protected. z is not inherited If we derive a class derivedfromprotectedderived from protectedderived, variables x and y are also inherited to the derived class. privatederived inherits variables x and y. Both variables become private. z is not inherited If we derive a class derivedfromprivatederived from privatederived, variables x and y are not inherited because they are private variables of privatederived.

4. C++ functions. 1. Library Function 2. User-defined Function

4. C++ functions. 1. Library Function 2. User-defined Function 4. C++ functions In programming, function refers to a segment that group s code to perform a specific task. Depending on whether a function is predefined or created by programmer; there are two types of