Object
An object is something which has some definite
properties. In computing, an object is a memory location having a value and
referenced by an identifier. An object is an instance of a class.
Class
Class is the logical structure of an object. A
class is a blueprint where an object can build from this blueprint. In addition,
a class is the collection of data and methods or functions under a single class
name.
In C++, a program can have many classes. When a class is declared, no memory is
allocated until the object is defined. All the variables in the class are called
member variable and all the functions are called member function.
Structure of a class
class
ClassName
{
// member
variables
// member
functions
};
class
Rect
{
//memeber
varibales
public:
int
width;
int
height;
// member
functions
int
area(void);
};
This is a class of Rect where two member variables width and
height and a member function area.
#include<iostream>
using
namespace std;
class
Rect {
//memeber
varibales
public:
int
width;
int
height;
// member
functions
int
area(void);
};
int
Rect::area(void){
return
width * height;
}
int
main( ) {
Rect r;
r.height=5;
r.width=4;
cout<<"Area
of a rectangle: ";
cout<<r.area();
return
0;
}
Output
Area of a rectangle: 20
In the main function Rect is a class and r is
the object.