Inheritance

IInheritance in Object Oriented Programming can be described as a process of creating new classes from existing classes. New classes inherit some of the properties and behavior of the existing classes. An existing class that is "parent" of a new class is called a base class.

Types of Inheritance

1)    Single level  Inheritance

2)    ) Multi level  Inheritance

3)    Multiple Inheritance

4)    Hierarchical Inheritance

5)    Hybrid Inheritance

Benefits of Inheritance

1)    Reusability of code

2)    Reduce the software cost and design time

3)    Represents the real world situation

4)    Easy maintenance and expansion of program

Syntax

1.       Single level  Inheritance

Class base                                                      

{

..

..

}

class derived: public base

{

.

.

.

}

2.       Multi level  Inheritance

 class base                                                                

{

..

..

}

class derived1: public base

{

.

.

.

}

class derived2: public derived1

{

.

.

.

}

3.       Multiple Inheritance

 class base1

{

..

..

}

class base2

{

.

.

.

}

class derived : public base1,base2

{

.

.

.

}

4.       Hierarchical Inheritance

 class base

{

..

}

class derived1: public base

{

.

.

}

class derived2: public base

{

.

.

}

          Single Inheritance

                        Multi level Inheritance         

Multiple Inheritance

Hierarchical  Inheritance

Hybrid  Inheritance

Visibility Mode

Public mode: If a class is inherited in public mode there is no change in access control of base class.

i.e  

public members                       remain                 public

protected members               remain                 protected

private members                     remain                 private

Protected mode: If a class is inherited in protected  mode public members will become  protected  and no change in access control of protected and private members of  base class.

i.e  

public members                       change to            public

protected members               remain                 protected

private members                     remain                 private

Private  mode: If a class is inherited in private mode public  and protected members will become  private  and no change in access control of  private members of  base class.

i.e  

public members                       change to            private

protected members               change to            private

private members                     remain                 private

Tips to solve board pattern questions

1.       To calculate size of object

While we are calculating size of object we must know the size of different  data types

Integer                                 2 bytes

Float                      4 bytes

Long                      4 bytes

Double                                 8 bytes

Short                     2 bytes

Char                       1 bytes ( for string name[10]= 10x1=10 bytes, city[20]=20x1=20 bytes}

While we are calculating size of object first we should calculate size of it’s own class  then check if some class is inherited in it or not if  yes then calculate the size of inherited class and add it on size of previously calculated size repeat this process this condition is true (please be careful while calculating the size , don’t do counting mistakes). While calculating size don’t bother about visibility mode.

Example

class A

{

}

class B:public A

{

}

class  C:public B

{

}

If we have to find the size of object of class C

1)      Go to class c calculate its size then (2) check if class is inherited or not here yes B is inherited, (3) calculate the size of B( 4 )again check if some class is inherited in class B or not here again it is true(5) so calculate size of A also (6) again check if some is inherited in class A or not, here it is false  so stop the process . (7) add all three size it will be the size of object of class C
2. Members accessible from object
Always remember object can access only public members. while you are finding the members accessible from object first write down only PUBLIC member of its own class. then check if some class is inherited in it in PUBLIC Mode or not if it is then go to that class and then write the public members of this class, if some class is inherited in this class in public mode then go to that class also and write the public members.

   

 3. Members accessible from MEMBER FUNCTION
Remember function can access every thing of it's own class so write every thing of class which belongs to it

now check some class is inherited or not
 first level it will entry with public, protected and private gate and access public and protected member(as pvt member cant be inherited)

if some class is inherited in its base class then it will go through only public and protected gate and access only public member from this class. go through this diagram: