what is class and object in c++ code example

Example 1: how to write a class in c++

class Rectangle 
{
	int width, height;
public:
	void set_values (int,int);
    int area() {return width*height;}
};

void Rectangle::set_values (int x, int y)
{
	width = x;
	height = y;
}

Example 2: classes c++

class Rectangle {
    int width, height;
  public:
    void set_values (int,int);
    int area (void);
} rect;

Example 3: classes c++

class class_name {
  access_specifier_1:
    member1;
  access_specifier_2:
    member2;
  ...
} object_names;

Example 4: new class * [] c++

/*
 Keyword "this"
You can use keyword "this" to refer to this instance inside a class definition.

One of the main usage of keyword this is to resolve ambiguity between the names of 
data member and function parameter. For example:
*/
class Circle {
private:
   double radius;                 // Member variable called "radius"
   ......
public:
   void setRadius(double radius) { // Function's argument also called "radius"
      this->radius = radius;
         // "this.radius" refers to this instance's member variable
         // "radius" resolved to the function's argument.
   }
   ......
}