C++.pdf

Full text

(1)C++ OOP Concepts.

(2) Outline § Basics of Object Oriented Programming § Introduction to C++ § C++ Language OOP Constructs & Features.

(3) Basics of Object Oriented Programming.

(4) What is OOP? § Object Oriented Programming (OOP) is the programming paradigm uses objects to design applications and computer programs. § Object oriented programming provides some nice features, some of them include : §. Classes. §. Data Abstraction. §. Objects. §. Data Encapsulation. §. Constructors & Destructors. §. Polymorphism. §. Inheritance. §. Overloading.

(5) Objects § The basic unit of Object Oriented Programming. § Objects are data structures consisting of data fields and methods. § Each object is a particular instance of a class, which has its unique name. § Each object carries the properties of its relevant class, i.e.variables & associated functions. § When created, each object allocates memory for variables and data associated with it..

(6) Classes § Classes are the data types from which objects are created. § It can be seen as a template which define the abstract characteristics and behaviour of a thing (object). § Properties – Characteristics of each object that may be created from the class. § Methods – Actions to be performed by the objects that are declared in class. § No memory is allocated when a class is created..

(7) Classes (Contd..) § Memory allocation happens only when the actual instances of a class (the objects) are created. § Basically, a class is an expanded concept of a data structure; which can hold data as well as functions. § In terms of variables, a class would be the data_type and the object would be the variable..

(8) Properties & Methods § Properties mean the data to be used or manipulated within a computer program. § Properties are generally referred to as variables. § Methods are the subroutines exclusively associated with a class or with an object. § The methods may have a sequence of programming statements to perform some action, a set of input parameters to customize these actions, and possibly an output value of some kind. § Methods in C++ are usually called functions..

(9) Introduction to C++.

(10) Introduction to C++ § C++ - An enhancement of C with added OOP concepts. § Originally named “C with Classes”. Later changed to C++ by adding increment operator of C language. § Standardized 14882:2003.. as. ISO/IEC. 14882:1998 and later ISO/IEC. § C++ has a slightly enhanced standard library over C. § C++ class based approach helps generic and template based programming..

(11) C++ OOP Features.

(12) Classes & Objects § Declared with a keyword class. § The syntax for class declaration is as follows:. class class_name{ access_specifier_1: member1; access_specifier_2: member2; ... } object_names;.

(13) Classes & Objects (Contd..) § class_name is a valid C++ identifier. § The body of the declaration may contain members, which can be both data or function declarations, and optionally access specifiers. § object_list is an optional list of names of objects of this class. § Access specifiers: private, protected & public..

(14) Classes & Objects (Contd..) § private : members of a class accessible only from within other members of the same class or from their friends. § protected : accessible from members of their same class and from their friends, and also from members of their derived classes. § public : accessible from anywhere where the object is visible..

(15) Classes & Objects (Contd..) Example class Employer{ int regno, sal; public: void set_values (int, int); int area (void); } emp;. § Employer – is a class § emp – is an object of class Employer § Class has data and member functions that may be accessed through a ‘.’ (dot) operator..

(16) class Example class #include <iostream> using namespace std; class cube { public: double side; double volume() { return (side * side* side); } };. main() Program int main() { double volume1 = 0; cube c1,c2; cout << "Enter the length of the cube:" << endl; cin >> c1.side; cout << "The volume of the cube is:" << c1.volume() << endl; c2.side = c1.side + 2; cout << "The volume of the 2 nd cube is:“ << c2.volume() << endl; return(0); }.

(17)

(18)

(19) Constructor § Constructors are used to initialize the objects. § Constructor – A special kind of function which is the member of the class. § The name of the constructor is same as the name of the class. § Constructor is automatically called whenever an object is created. § Constructors DO NOT have a return value..

(20) Constructor (Contd..) § A default constructor is the one with no parameters. § If no constructor is defined by the user, the compiler supplies the default constructor..

(21) Destructor § A destructor is the complement of the constructor that is, it is used to destroy the objects. § The objects are destroyed in order to deallocate the memory occupied. § The name of the destructor is the same as the constructor and is preceded by a ‘~’ (tilt) operator. § A destructor for objects is executed in the reverse order of the constructor functions..

(22) Constructor-Destructor Example Constructor & Destructor. #include<iostream> using namespace std; // continues here... class cube cube() { { public: cout << "A default constructor double side; is called " << endl; double volume() } { ~cube() return( side * side * side ); { } cout << "Destructing " << cube(double side1) side << endl; { } cout << "A constructor is called" << endl; }; side=side1; } // continue....

(23) Constructor-Destructor Example (Contd..) int main() { cube c1(2.34); cube c2;. main Program. cout << "The side of the cube is: " << c1.side << endl; cout << "The volume of the first cube is : " << c1.volume() << endl; cout << "Enter the length of the second cube : " ; cin >> c2.side; cout << "The volume of second cube is : " << c2.volume() << endl; return(0); } // end....

(24) Constructor-Destructor Example (Contd..) Constructor & Destructor. #include<iostream> using namespace std; cube() class cube { { cout << "A default constructor public: is called " << endl; double side; } double volume() ~cube() { { return( side * side * side ); cout << "Destructing " << } side << endl; cube(double side1) } { }; cout << "A constructor is called" << endl; side=side1; } // continue...

(25)

(26)

(27)

(28) Constructor-Destructor Example (Contd..) int main() { cube c1(2.34); cube c2;. main Program. cout << "The side of the cube is: " << c1.side << endl; cout << "The volume of the first cube is : " << c1.volume() << endl; cout << "Enter the length of the second cube : " ; cin >> c2.side; cout << "The volume of second cube is : " << c2.volume() << endl; return(0); } // end....

(29)

(30)

(31)

(32)

(33) Inheritance § A process of forming a new class from an existing class (often called base class). § The base class – also called parent class/super class. § The derived class – also called as child class/sub class/extended class. § Inheritance helps reduce the overall size of the program code, which helps the overall performance. § The derived/extended classes have all the properties of the base class. Upon them, a programmer can choose to add new features specific to the newly created derived class..

(34) Inheritance (Contd..) § Advantages of inheritance: § Reusability • Inheritance helps the reuse of the same code . • Once the base class is defined and worked out, it need not be reworked. • Any no. of derived classes can be created from the base class as needed while adding specific features to each derived class as needed. §. Saves Time & Efforts. §. Increases the program structure which results in a greater reliability..

(35) Inheritance (Contd..) § Inheritance declaration: class <derived_class_name> : <access_specifier><base_class_name> e.g. –. class bread: public food class e_n_c: private engg class science_students: protected students.

(36) Inheritance (Contd..) //base class class food { public: food(void) { x=0; } void f(int n1) { x= n1*5; } void output(void) { cout << x; } private: int x; }; //end of base class. Inheritance Example // derived class class bread: public food { public: bread(void) { s1=0; } void f1(int n1) { s1=n1*10; } void output(void) { food :: output(); cout << s1; }. private: int s1; } // end of derived class // main program int main (void) { bread s; s.f(10); s.output(); s.f1(50); s.output(); } //end of main program.

(37)

(38)

(39)

(40)

(41)

(42)

(43)

(44)

(45) Inheritance (Contd..) § Some important points regarding inheritance: § Derived class CANNOT have access to the constructor or destructors of the base class. § However, it can add new member functions or variables, new constructors or destructors. § For each object of the derived class, the memory is allocated for the data members of the base class as well as that of the derived class. § The derived class will have access to all the member data and functions of the base class which are not defined as private..

(46) Some Remark on Access Specifiers § public: All public type members of the class are accessible from outside the class. § private: None of the members of type private within the class may be accessed from outside the class. § protected: protected access specifier lies in between public and private. If the member function/variable is defined in a class as protected, it cannot be accessed from outside the class but they can be accessed by the derived class of that class..

(47) Data Abstraction § It allows creation of user-defined data types. It represents the needed information without presenting the details. § The main idea behind data abstraction is to give a clear separation between properties of data type and the associated implementation details. § Abstract data type: § Properties – clearly visible to the user interface. § Implementation details – hidden.. § Abstract data type – defined in terms of the operations that it performs, and not in terms of its structure (implementations)..

(48) Data Abstraction (Contd..) § Two types of data abstraction: Functional Abstraction, & Data Abstraction. Functional Abstraction. Data Abstraction. Refers to functions without taking into account its implementation.. Refers to the data that is used without taking into account the way it is stored.. Access to the function is provided through a specific interface defined to invoke the function.. Access to the data is provided through a specific set of operations defined to examine and manipulate the data..

(49) Data Abstraction (Contd..) § Reasons for need of abstraction: § Flexibility in approach: By hiding data or abstracting details, the programmer achieves greater flexibility. § Enhanced security: Hiding the implementation details provides security. § Easier replacement: Allows the code to be replaced without recompilation. So, replacing code becomes easier and less time consuming. § Modular approach: Project application may be divided into modules and each of them may be tested separately. Later, all the modules are taken together and tested. So, application development approach becomes easier..

(50) Data Abstraction (Contd..) § Ways to achieve abstraction: 1. Modular/Function based approach: § Code is broken int small segments – functions § Code or parts of it may be reused many times. § It customized all the data of a similar type, under the control of a type module. § By defining module type, we can get the module to be an abstract data type. 2. Friend Functions: § One class or some of its members are associated with the other class as its “friend”..

(51) Encapsulation § The process of combining or packaging data with functions and thereby allowing users to create a new abstract data type. (which is nothing but a class!) § As data and functions reside inside a single autonomous unit. § The user cannot directly access the encapsulated data. § Encapsulation introduces the concept if information hiding..

(52) Encapsulation (Contd..) Encapsulation Example. class Exforsys { public: int sample(); int example(char *se) int endfunc(); //Other member functions private: int x; float sq; //Other data members };. All data members and functions are bundled inside a single autonomous entity called class Exforsys..

(53) Encapsulation (Contd..) § As the data and the functions are bundled inside the class, the class takes total control of maintenance and hence human errors are reduced. § Encapsulated objects act as black boxes to the other parts of the program. This enhances the security. And still, the objects maybe used to achieve some functionality. § The usage of access specifiers can further add restrictions on the way data may or may not be allowed to be accessed. § In case a user wants some non-member function to access an object’s private or protected data, he/she can use friend functions..

(54) Abstraction vs. Encapsulation Encapsulation. Abstraction. • Information hiding. • Working on higher level without worrying about internal details.. • It hides data.. • It hides implementation. • It binds the data and functions and is independent for each object. • Data hiding is applicable for the Once this object gets destroyed, whole implementation. all related binding information also gets destroyed..

(55) Polymorphism § Polymorphism allows routines to use variables of different types at different times. § It is an ability to use an operator or a function in different ways. § A function given different meanings or an operator functioning in many ways is called “Polymorphism”..

(56) Overloading § Overloading is a type of polymorphism. § When an exiting operator or function begins to operate on new data type, or class, it is understood to be overloaded. § There are two types of overloading: § Function overloading, & § Operator overloading.

(57) Function Overloading § Polymorphism in which the functions assume different forms at different times is called function overloading. § The selection of an appropriate function is done at the compile time. § Two or more functions may have the same name but their parameter lists should be different in terms of either: § parameters, or § their data types. § The functions which differ only in their return values CANNOT be overloaded..

(58) Function Overloading (Contd..) § The compiler selects right function depending on the type of parameters passed. § In case of classes, the constructors could be overloaded as they can be both initialized and uninitialized objects..

(59) Function Overloading (Contd..) Function Overloading Example #include<iostream> using namespace std; // start of class class employee { public: int week; int year; double calculate(double salary) { return(salary*week); } // fnc-1. int calculate(int salary) { return(salary*week*year); } // fnc-2 employee(int week1) { week = week1; } // constructor-1 employee(int week1,int year1) { week = week1; year = year1; } // constructor-2 }; // end of class.

(60) Function Overloading (Contd..) main Program. int main() { int sal; double sal2; employee emp1(10); employee emp2(10,3); cout << "Enter the no years for first employee" << endl; cin >> emp1.year; cout << endl << "Enter the salary per week for first employee" << endl; cin >> sal; cout << "The total salary of first employee is : " << emp1.calculate(sal) << endl; cout << endl << "Enter the salary per week for second employee is : " << endl; cin >> sal2; cout << "The total salary of second employee is for one year: “ << emp2.calculate(sal2) << endl; return(0); } // end of main program...

(61)

(62)

(63)

(64)

(65) Operator Overloading § Polymorphism in which the operators assume different meanings at different times is called operator overloading. § Operator functions are created to perform operator overloading. § However, operator overloading DOES NOT allow creating new operators. § General syntax for operator function is as follows: <return_type> operator #(<arg_list>) { ... }.

(66) Operator Overloading (Contd..) <return_type> operator #(<arg_list>) { ... } § § § §. <return_value> : return type of the function <arg_list> : list of function arguments operator is a keyword. # will be replaced with an operator for which overloading is to be done..

(67) Operator Overloading (Contd..) Operator Overloading Example #include<iostream> using namespace std; // start of class class rectangle { public: int length; int breadth; rectangle(int length1, int breadth1) { length = length1; breadth = breadth1; } // constructor. int operator+(rectangle r1) { return(r1.length+length); } }; // end of class.

(68) Operator Overloading (Contd..) main Program int main () { rectangle r1(10,20); rectangle r2(40,60); int len; len = r1+r2; cout << "The total length of the two rectangles is : " << len << endl; return(0); } // end of main program...

(69)

(70)

(71)

(72) ThanQ.

(73)

No results found