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Figure below shows a simple inheritance hierarchy. A typical company has hundreds of persons. An important subset of these persons is a set of employees. Employees are either workers or secretaries.

Person class hierarchy

Each class in a class hierarchy cumulatively inherits the class members of all classes that precede it in the hierarchy chain.

A class that directly precedes another class in a class hierarchy, and is included in the derived class’s base list, is called the direct base class.

A class that does not directly precede another class in a class hierarchy, and that not included in the derived class’s base list, is called the indirect base class.

Access specifiers and inheritance

Even though a derived class inherits the class members of a base class, the base class’s members are still bound by its access specifiers.

Private class members in the base class can be accessed only the base class’s member functions.

For example, the idNum data member in the Person class is private. If you write the following member function in the Customer class, which attempts to directly access to the idNum data member, you will get a compiler error.

void Customer::outputBalDue(){

cout<<“ ID #”<<idNum<<“ Balance due $”<<balanceDue<<endl;

}

Instead, to access the idNum data member you must call the Person class’s outputData() member function, which is public. Alternatively, you can declare the idNum data member with the protected access specifier.

The protected access modifier restricts class member access to

  1. the class itself
  2. to classes derived from the class, or

The following code shows a modified version of the Person class declaration in which the private access modifier has been changed to protected.

Example:

class Person {

protected:

int idNum;

char lastName[20];

char firstName[15];

public:

void setFields(int num, char last[], char first[]);

void outputData();

};

A member function in Customer class that attempts to directly access to the idNum data member will work correctly since the Customer class is a derived class of the Person class and the idNum data member is now declared as protected.

Overriding base class member functions

Derived classes are not required to use a base class’s member functions. You can write a more suitable version of a member function for a derived class when necessary. Writing a member function in a derived class to replace a base class member function is called function overriding .

To override a base class function, the derived member function declaration must exactly match the base class member function declaration, including the function name, return type and parameters.

To force an object of a derived class to use the base class version of an overridden function, you precede the function name with the base class name and the scope resolution operator using the syntax:

object.base_class::function();

Example

In the following code, the base class Person and the derived class Employee have their own function member with the same name setFields().

#include<iostream.h>

Questions & Answers

How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
How can I make nanorobot?
Lily
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
how can I make nanorobot?
Lily
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
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Source:  OpenStax, Programming fundamentals in c++. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10788/1.1
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