Chapter 13, Problem 1RQE

What is the difference between a class and an instance of the class?

Program Plan Intro

Class:

In object oriented programming, the concept of class is considered as an important feature.

• A class is a collection of data members and member functions, which are used to represent the overall structure of the project.
• The objects are created to access the data members and its functions of the class.

Explanation of Solution

Difference between class and instance of the class:

Some of the differences between class and instance of the class are as follows:

Class	Instance of the class
A class is like a blueprint from which the object is created.	Instance of a class is called as an object.
When a class is created, its memory space is not allocated.	After the creation of an instance for the class, memory space is allocated.
Class is a logical entity.	Instance of the class is a physical entity.
The definition for a class can be created only once.	The object can be created as many times as possible.
Syntax: class Class_name { //class members }	Syntax: Class_name object;

Example Program for class and instance of a class:

//Include the required header files

#include<iostream>

#include<string>

using namespace std;

//class name

class Mobile

{

//Access specifier

public:

//Declare a variable

string mobile_name;

};

//Main Function

int main()

{

//create a first object for mobile

Mobile object1;

//Assign a string to the object

object1.mobile_name = "Samsung";

//print the name

cout << object1.mobile_name << endl;

//create a second object for mobile

Mobile object2;

//Assign a string to the object

object2.mobile_name = "Apple";

//print the name

cout << object2.mobile_name << endl;

}

Explanation:

• In the above program, inside a class “Mobile”, declare a variable named “mobile_name”.
• Inside  a main function
  • Create an object named “object1”.
  • Access and assign a string “Samsung” to the data member.
  • Print the string.
  • Create an object named “object2”.
  • Access and assign a string “Apple” to the data member.
  • Print the string.

Sample Output

Samsung

Apple