Object Oriented Programming. Assistant Lecture Omar Al Khayat 2 nd Year

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1 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

2 Syllabus Overview of C++ Program Principles of object oriented programming including classes Introduction to Object-Oriented Paradigm:Structures Classes Constructors and Destructors. Friend Functions and Friend Classes

3 Templates: Function Templates and Class Templates Inheritance Virtual Functions, Polymorphism, and Overloading

4 References Object Oriented Programming with C++ by E Balagurusamy, fourth Edition 2008, published by Tata McGraw Hill. Object Oriented Programming in C++ by Robert Lafore,fourth Edition,sams pub,2002. Object Oriented Programming using C++ by Joyce Farrell Data Structures and Program Design in C++ - Robert L. Kruse

5 Overview of C++ Programming

6 Simple C++ Program // comment // comment... #include <Lib. Name>.. Void main() { Program instruction(s) }

7 C++ Program Structure: Comments Libraries main function Statements that define memory locations (constants and variables) Statements that specify actions to be taken (i.e. flow of controls) Operational expressions involving data representations Representations of data of different types (e.g. structure) Other Functions and procedures

8 Standard Input and Output Output Statement: Input Statement

9 Overview of C++ Programming

10 Conditional Statements (if Condition)

11 Repitision Statements

12 Nested FOR Statements

13 Array One Dimensional Array (1D Array)

14 For example: 2D Array (Matrix)

15 Structures A structure is a collection of simple variables that have same or different data types: int, float, and so on. This is unlike the array in which all the variables must be the same type. The data items in a structure are called the members of the structure.

16 In order to use a structure in our C++ programs, we need the following: 1) Defining the structure. 2) Defining a structure variable(s). 3) Accessing and manipulating the members of the structure.

17 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

18 Pointer

19 Every byte in the computer s memory has an address. Each program, when it is loaded into memory, occupies a certain range of these addresses. That means that every variable and every function in your program starts at a particular address.

20 A pointer is a variable that holds an address value. Hence we can use pointers to find out where things are in memory. The data type of pointer is not the same as the variable whose address is being stored; a pointer to int is not type int.

21 Pointer Definition To define the variable pointer: Type *pointer_name Example:

22 Uses of pointers Accessing array elements Passing arguments to a function when the function needs to modify the original argument Passing arrays and strings to functions Obtaining memory from the system Creating data structures such as linked lists

23 Pointers and Arrays

24 Functions

25 A function groups a number of program statements into a unit and gives it a name. This unit can then be invoked from other parts of the program as shown in the figure below. Two reasons to use functions: 1) to aid in the conceptual organization of a program. (However, object-oriented programming is more powerful). 2) to reduce program size.

26 To add a function to the C++ program, we need to add three components to the program: Function declaration (prototype). Calls to the function. Function definition.

28 Passing Arguments to Functions Passing by Value: Passing arguments in this way, where the function creates copies of the arguments passed to it, is called passing by value. when the function call is executed will be passed to the function. As it did when constants were passed to it, the function creates new variables to hold the values of these variable arguments. The function gives these new variables the names and data types of the parameters specified in the declarator

29 Passing by Reference: When we need the function returns more than one value, we can pass arguments by reference to the function. A reference provides an alias another name for a variable (It s actually the memory address of the variable that is passed). An important advantage of passing by reference is that the function can access the actual variables in the calling program.

30 Passing by pointer: Passing a pointer as an argument to a function is in some ways similar to passing a reference. They both permit the variable in the calling program to be modified by the function. However,the mechanism is different. A reference is an alias for the original variable, while a pointer is the address of the variable.

31 Functions & Structure

32 A structure can be passed to a function as a single variable. The scope of a structure declaration should be an external storage class whenever a function in the main program is using a structure data types. The field or member data should be same throughout the program either in the main or in a function.

33 Function Overloading Overloading refers to the use of the same thing for different purposes. Function overloading means that we can use the same function name to create functions that perform a variety of different tasks. These overloaded functions have the same function name but with different argument lists (i.e. different number and/or different data types of arguments). An overloaded function appears to perform different activities depending on the kind of data sent (passed) to it. It performs one operation on one kind of data but another operation on a different kind.

34 Inline Functions To save execution time in short functions, you may elect to put the code in the function body directly inline with the code in the calling program. That is, each time there s a function call in the source file, the actual code from the function is inserted, instead of a jump to the function.

35 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

36 Introduction There are two weaknesses related with structured programming: Firstly, functions have unrestricted access to global data. This causes a program s structure difficult to conceptualize. In addition, it makes the program difficult to modify. Any change made in a global data item may necessitate rewriting all the functions that access that item

37 Object-Oriented Programming (OOP)

38 OOP incorporates the best features of structured programming with several powerful new concepts. It provides a new way of thinking, organizing and developing programs. OOP allows decomposition of a problem into a number of entities called objects and then builds data and functions around these objects

39 Class: Fundamental OOP Concepts

40 Object: Fundamental OOP Concepts

41 Fundamental OOP Concepts Encapsulation:

42 Inheritance: Fundamental OOP Concepts

43 Fundamental OOP Concepts Polymorphism:

44 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

45 Classes

46 The general form of a class declaration in C++ is:

47 Objects: Once a class has been defined, we can create objects of that type as follows: This statement creates an object x of type item. At this stage, memory space is allocated to the object x. We may also declare more than one object in one statement, for example

48 Accessing Class Members Definition of Member Functions

49 Definition of Member Functions Class member functions can be defined in two places: 1. Outside the Class Definition 2. Inside the Class Definition

50 General Form: DataType Class_Name :: Member_Function_Name(DataType input(s))

51 Example: Inside the Class Definition

52 Private Member Functions Some tasks such as deleting a customer account, or providing an increment to an employee may require certain functions to be hidden (like private data) from the outside calls. We can place these functions in the private section. Note that a private member function can only be called by another member function of its class, and cannot be called by an object.

53 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

54 Constructors Destructors

55 Constructors A constructor is a member function whose name is the same as the class name. The constructor is used to initialize the objects of its class. The constructor is automatically invoked whenever object of its associated class is created.

56 Notes: The constructor should be declared in the public section. The constructor does not have return type, (not even void), and therefore it cannot return any value. There is no need to write any statement to invoke the constructor function because it is invoked automatically when the object is created.

57 Parameterized Constructors Sometimes we need to initialize the data elements of different objects with different values when they are created. This can be done by passing arguments to the constructor function when objects are created. Such constructor is called parameterized constructor.

58 Destructors A destructor is a member function whose name is the same as the class name but is preceded by a tilde ~. The destructor is used to destroy the objects that have been created by a constructor. For example, the destructor for the class integer is defined as follows: ~integer() { }

59 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

60 Friend Function

61 Friend Function Sometimes we need a non-member function that has full access to the private data of a class. We would like many classes to share a particular function. In such situations, we define the function as a friend function with these classes. Such a function need not be a member of any of these classes.

62 Friend Class

63 Friend Class We can also declare all the member functions of one class as the friend functions of another class. In such cases, the class is called a friend class. This can be specified as follows:

64 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

65 Memory Management Operators

66 Memory Management Operators An object can be created by using new and destroyed by using delete as and when required. A data object created inside a block with new will remain in existence until it is explicitly destroyed by using delete. The new operator can be used to create objects of any type.it takes the following general form :

67 Array of Object

68 Array of Object We can also array of variables that are of the type class. Such variables are called arrays of objects. Consider the following class definition:

69 Objects as function arguments

70 Objects as function arguments Example: (Add Two Time in Hours, Minutes Using Friend Function) #include <iostream> #include <conio.h> using namespace std;

71 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

72 Returning Objects

73 Returning Objects A function can not only receive objects as arguments but also can return them. Example: Add two complex numbers A and B to produce a third complex number C and display all the three numbers.

74 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

75 Operator Overloading

76 Operator Overloading Operator overloading is one of the most exciting features of object oriented programming. It can transform complex, obscure program listings into intuitively obvious ones.

77 The term operator overloading refers to giving the normal C++ operators, such as +, *, <=, and +=. Additional meanings when they are applied to user-defined data types like classes.

78 Defining Operator Overloading

79 Overloading Unary Operators

80 Overloading Binary Operators

81 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

82 Pointers to Objects

83 Pointers to Objects Sometimes, when we are writing the program we don t know how many objects we want to create. In such case, we can use new operator to create objects at run time. The new operator returns a pointer to an unnamed object. Thus, object pointers are useful in creating objects at run time.

84 this Pointer C++ uses a unique keyword called this to represent an object that invokes a member function. this is a pointer that points to the object for which this function was called. The pointer this is automatically passed to a member function when it is called.

85 One important application of the pointer this is to return the object it points to. The statement return *this; inside a member function will return the object that invoked the function.

86 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

87 Copy Constructor

88 Copy Constructor It is a member function which initializes an object using another object of the same class. A copy constructor has the following general function prototype: class_name (const class_name&obj); {//body of constructor} A copy constructor takes a reference to an object of the same class as it self as an argument. We can not pass the argument by value to copy constructor.

89 What is the main difference between the copy constructor and the assignment operator? The copy constructor creates a new object. The assignment operator works on an already valid object.

90 Constant Object

91 Constant Object We ve seen that we can apply constant to variables of basic types such as int to keep them from being modified. In a similar way, we can apply constant to objects of classes. When an object is declared as constant, you can t modify it. It follows that you can use only constant member functions with it, because they re the only ones that guarantee not to modify it.

92 1. When we decelerate the object as constant we must also set member function as constant. 2. Can not modify any data of the object which set as constant object. 3. The 3 rd line in the main program if we active it the program not work because this function is not constant member function and if we set a constant also not work because this function try to modify data. 4. The output of this program is:

93 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

94 Templates

95 Templates Templates enable us to define generic classes and functions and thus provide support for generic programming. A template can be used to create a family of classes or functions. For example, a class template for an array class would enable us to create arrays of various data types such as int array and float array. Templates for a function, say mul( ),that would help us to create various versions of mul( ) for multiplying int, float and double types values.

96 Class Templates

97 Class Templates The general form of class template is:

98 Class Template With Multiple Parameters

99 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

100 Member Function Template

101 Member Function Template At the previous examples we use a template class with member function built inside the class. To implement a member function template (outside the class):

102 non T template arguments We can use non-template arguments with template arguments. The general form of non_t is: template <class T, data_type Var1,..> The following example is print an array (1D) of varying type:

103 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

104 Function Templates

105 Function Templates We can also define function template to create family of function s with different arg s types. The general form of Template Function is:

106 Function Template with Multiple arg s We can use multiple generic data types in the function arg s) The general form of using multiple data types in function is:

107 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

108 Inheritance

109 Inheritance Inheritance is the process of creating new classes, called derived classes, from existing or base classes. The derived class inherits all the capabilities of the base class but can add embellishments and refinements of its own. The base class is unchanged by this process.

110

111 Inheritance Types: 1. Single Inheritance. 2. Multiple Inheritance. 2. Multilevel Inheritance.

112 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

113 Defining Derived Classes

114 Defining Derived classes Class Derived_Class : Visibility-Mode Base_Class Where Visibility Mode : Public or Private By default, the mode is private.

115 Note: When a base class is privately inherited by a derived class, public members of the base class become private members of the derived class and therefore the public members of the base class can only be accessed by the member function of the derived class. They are inaccessible to the objects of the derived class.

116 Object Oriented Programming Assistant Lecture Omar Al Khayat 2 nd Year

117 Making a private member inheritable

118 Making a private member inheritable A member declared as protected is accessible by the member function within its class and any class immediately derived from it It cannot be accessed by the function outside these two classes.

119

120

121

122 Application1

123 Write OOP Program to subtract two of the rectangular area, using Constructor, and Binary Operator.

124 Write OOP program to represents the information of two departments each of one have 5 students, using constructor.

125 Application2

126 Write C++ program using class to calculate the area of rectangle.

127 Write C++ program using class to calculate the max number between two numbers.

Data Structures using OOP C++ Lecture 3

Data Structures using OOP C++ Lecture 3 References: th 1. E Balagurusamy, Object Oriented Programming with C++, 4 edition, McGraw-Hill 2008. 2. Robert L. Kruse and Alexander J. Ryba, Data Structures and Program Design in C++, Prentice-Hall 2000.