Chapter-10 INHERITANCE

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1 Chapter-10 INHERITANCE Intrductin: Inheritance is anther imprtant aspect f bject riented prgramming. C++ allws the user t create a new class (derived class) frm an existing class (base class). Inheritance: Inheritance is the capability f ne class t inherit prperties frm anther class. Base Class: It is the class whse prperties are inherited by anther class. It is als called Super class. Derived Class: It is the class that inherits the prperties frm base class. It is als called Sub class. Need f Inheritance: Suppse X is a class already defined and we need t redefine anther class Y has same prperties f X and in additin its wn. Suppse if we use direct ptin withut using inheritance, it has fllwing prblems. Cde written in X is repeated again in Y which leads t unnecessary wastage f memry. Testing t be dne separately fr bth class X and class Y leads t waste f time. The abve prblem can be slved by using the cncept f inheritance. If we use the cde f X even in Y withut rewriting it. The class Y inherits all the prperties f X. The class X is called base class and the class Y is called derived class. The main advantages f Inheritance are: Reusing existing cde Faster develpment time Easy t maintain Easy t extend Memry Utilizatin The main disadvantage f Inheritance are: Inapprpriate use f inheritance makes prgrams mre cmplicated. Calling member functins using bjects creates mre cmpiler verheads. 1 P a g e

2 Defining Derived Classes: A derived class is a cmpsite class it inherits members frm the base class and adds member f its wn. The general frm f the derived class is given belw. Here, IMAGE class Keywrd derived_class_name Name f the derived class : Shws the derivatin frm the base class. Visibility Mde Specifies the type f derivatin base_class_name Name f the base class. Example: The use f a cnstructr can be cleverly dne especially in thse prblems where it is necessary t initialize certain data members cmpulsrily. Public Derived Class Private Derived Class Prtected Derived Class class father //Base class char name[10]; char caste[10]; int age; vid readdata( ); class sn : public father char gender[5]; vid display( ); class father //Base class char name[10]; char caste[10]; int age; vid readdata( ); class sn : private father char gender[5]; vid display( ); class father //Base class char name[10]; char caste[10]; int age; vid readdata( ); class sn : prtected father char gender[5]; vid display( ); Visibility mde: Visibility mde can be public, private r prtected. The private data f base class cannt be inherited. If inheritance is dne in public mde, public members f the base class becme the public member f derived class and prtected member f base class becme the prtected member f derived class.. 2 P a g e

3 3 P a g e If inheritance is dne in a private mde, public and prtected members f base class becme the private members f derived class. prtected: If inheritance is dne in a prtected mde, public and prtected members f base class becme the prtected members f the base class. Base class Public Inheritance: Derived Class Visibility Mde public private prtected public public private prtected private Nt inherited Nt inherited Nt inherited prtected prtected private prtected When a base class is inherited as public, all public members f the base class becme public members f derived class. The private members f the base class remain private t that class, and are nr accessible by members f the derived class. Example: A prgram illustrates public inheritance. #include<istream.h> #include<cni.h> class shape //Base Class int side1, side2; class rectangle : public shape //Derived Class int area; vid cmpute( ) area = side1 * side2; vid main( ) rectangle R; // R is the bject f derived class R.side1 = 5; // Data directly accessed by bject R.side2 = 6; OUTPUT: R.cmpute( ); cut<< Area f the rectangle = <<R.area; Imprtant 5 Marks Area f the rectangle = 30

4 Private Inheritance: When a base class is inherited as private, then all public and prtected members f the base class becme private members f derived class. This means that they are still accessible by member f the derived class, but cannt be accessed by ther parts f the prgram. Example: A prgram illustrates private inheritance. #include<istream.h> #include<cni.h> class shape //Base Class prtected: int side1, side2; int area; vid cmpute( ) area = side1 * side2; class rectangle : private shape //Derived Class vid readdata( ) cut << Enter the input first side : ; cin>>side1; cut << Enter the input secnd side : ; cin>>side2; vid display( ) cmpute( ); // Calling base class cut<< Area f the rectangle = <<area; vid main( ) OUTPUT: rectangle R; Enter the input first side : 9 R.readdata( ); Enter the input secnd side : 5 R.display( ); Area f the rectangle = 45 4 P a g e

5 Prtected Inheritance: When a base class is inherited as prtected, then all public and prtected members f the base class becme prtected members f derived class. The private data members f base class are nt visible t derived class. They can nly be accessed thrugh public and prtected member functins f base class. Example: A prgram illustrates prtected inheritance with the base class having prtected and public members. #include<istream.h> #include<cni.h> class shape //Base Class prtected: int side1, side2; int cmpute( ) return(side1 * side2); class rectangle : prtected shape //Derived Class vid readdata( ) cut << Enter the input first side : ; cin>>side1; cut << Enter the input secnd side : ; cin>>side2; vid display( ) cut<< Area f the rectangle = <<cmpute( ); OUTPUT: vid main( ) Enter the input first side : 7 rectangle R; Enter the input secnd side : 8 R.readdata( ); Area f the rectangle = 56 R.display( ); 5 P a g e

Types f Inheritance: Based n the relatinship, inheritance can be classified int five frms: Single Inheritance Multilevel Inheritance Multiple Inheritance Hierarchical Inheritance Hybrid Inheritance

6 Types f Inheritance: Based n the relatinship, inheritance can be classified int five frms: Single Inheritance Multilevel Inheritance Multiple Inheritance Hierarchical Inheritance Hybrid Inheritance Single Inheritance: Single Inheritance is the prcess f creating a new class frm existing class base class. It is very cmn in inheritance that a class is derived frm the base class. The data members and memberfunctin f the base class are data member and member functin f the derived class. Imprtant 5 Marks A derived class with single inheritance is declared as fllws: class Base_Class class Derived_class : public Base_calss Example: Prgram t illustrate single level inheritance. #include<istream.h> #include<cni.h> class base int rlln; char name[10]; vid read( ) 6 P a g e

7 7 P a g e cut << Enter Rll Number and Name <<endl; cin >> rlln >> name; vid display( ) cut << Rll N : << rlln <<endl; cut << Name : << name <<endl; class derived : public base int m1, m2, t; vid read1( ) cut << Enter Maths and Cmputer marks <<endl; cin >> m1 >> m2; t = m1 + m2; vid display1( ) cut << Maths : << m1 <<endl; cut << Cmputer : << m2 <<endl; cut << Ttal Marks : << t <<endl; OUTPUT: vid main( ) derived bj; clrscr( ); bj.read( ); bj.read1( ); bj.display( ); bj.display1( ); getch( ); Multilevel Inheritance: Enter Rll Number and Name 1234 RAM Enter Maths and Cmputer marks Rll N : 1234 Name : RAM Maths : 80 Cmputer : 90 Ttal Marks : 170 Derivatin f a class frm anther derived class is called multilevel inheritance. In the figure class A is the base class fr class AB and class AB is the base class fr class ABC. The class AB prvides a link fr the inheritance between A and ABC, and is knwn as

multilevel inheritance. #include<istream.

8 intermedidate base class. A derived class with multilevel inheritance is declared as fllws: class A class AB : public A class ABC : public AB Example: Prgram t illustrate multilevel inheritance. #include<istream.h> #include<cni.h> class A vid displaya( ) cut << Base class A <<endl; class AB : public A 8 P a g e

9 vid displayab( ) cut << Intermediate Base class AB <<endl; cut << Derived frm A << endl; class ABC : public AB vid displayabc( ) cut << Derived Class ABC <<endl; cut << Derived frm AB << endl; vid utput( ) displaya( ); displayab( ); displayabc( ); vid main( ) ABC bj; clrscr( ); bj.utput( ); getch( ); Multiple Inheritance: OUTPUT: Base Class A Intermediate Base Class AB Derived frm A Derived Class ABC Derived frm AB A class can be derived frm mre than ne base calss is knwn as multiple inheritance. A derived class with multiple inheritance is declared as fllws: class A //Base Class A 9 P a g e

10 class B //Base Class B class C //Base Class C class Derived_Class : public A, private B, prtected C //Members f derived class Hierarchical Inheritance: If a number f classes are derived frm a single base class, it is called as hierarchical inheritance. Hierarchical mdel exhibits tp dwn apprach by breaking up a cmplex class int simpler class. Hybrid Inheritance: Hybrid Inheritance is cmbinatin f Hierarchical and multilevel inheritance. 10 P a g e

11 Virtual Base Classes: When tw r mre bjects are derived frm a cmmn base class, we can prevent multiple cpies f the base class being present in an bject derived frm thse bjects by declaring the base class as virtual when it is being inherited. Such a base class is knwn as virtual base class. This can be achieved by preceding the base class name with the wrd virtual. Example: Class A class B : virtual public A class C : virtual public A class D : public B, public C Abstract Class: An abstract class is ne that is nt used t create bjects. An abstract class is designed nly t act as a base class (t be inherited by ther classes). Cnstructr and Destructrs in derived classes: A destructr is special member functin that is executed when an bject f that class is destryed. 11 P a g e

12 Destrying an bject means, de-allcating all the resurces such as memry that was allcated fr the bject by the cnstructr. It will have like cnstructr, the name same as that f the class but preceded by a tilde (~). Example: Prgram t illustrate the use f destructrs in C++. class Base Base( ); //Default cnstructr cut<< Inside Base Cnstructr <<endl; ~ Base( ); //Destructr cut<< Inside Base Destructr <<endl; class Derived : public Base Derived( ); //Default cnstructr cut<< Inside Derived Cnstructr <<endl; ~ Derived( ); //Destructr cut<< Inside Derived Destructr <<endl; OUTPUT: vid main( ) Inside Base Cnstructr Derived x; Inside Derived Cnstructr a.display( ); Inside Derived Destructr Inside Base Destructr CHAPTER 10 Inheritance BLUE PRINT VSA (1 marks) SA (2 marks) LA (3 Marks) Essay (5 Marks) Ttal Questin 01 Questin Questin N Marks Imprtant Questins 12 P a g e

13 5 Marks Questin: 1. What is Inheritance? Explain any tw types f Inheritance. 2. What are visibility mdes? Explain. 3. What is the difference between public, private and prtected access specifiers? 4. Explain single inheritance with a suitable C++ prgram. 5. What is Multilevel Inheritance? Explain with a suitable prgram example. 6. What is virtual base class? Give example. 7. What are the advantages f Inheritance? (Any five) **************** 13 P a g e

Common Language Runtime

Common Language Runtime Intrductin t.net framewrk.net is a general-purpse sftware develpment platfrm, similar t Java. Micrsft intrduced.net with purpse f bridging gap between different applicatins..net framewrk aims at cmbining