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C++ User-Defined

The C++ can define your own user-defined types using structures (structs) and classes. These types allow you to encapsulate data and functions into a single unit, providing a way to model real-world objects or abstract concepts. Here, I’ll explain how to define your own user-defined types using both structs and classes.

  1. Using Structs: A struct is a simple way to define a user-defined type with public data members. Here’s an example:
 // Define a struct representing a Point in 2D space
 struct Point {
     double x; // public data member
     double y; // public data member

You can then create instances of this struct:

 Point p1;
 p1.x = 1.0;
 p1.y = 2.0;
  1. Using Classes: A class is similar to a struct but allows you to encapsulate data and functions (methods) together with access control (public, private, and protected). Here’s an example:
 // Define a class representing a Rectangle
 class Rectangle {
     // Constructors
     Rectangle(); // Default constructor
     Rectangle(double width, double height); // Parameterized constructor

     // Member functions
     double area() const;
     double perimeter() const;

     double width;  // private data member
     double height; // private data member

 // Define the constructor implementations
 Rectangle::Rectangle() : width(0.0), height(0.0) {

 Rectangle::Rectangle(double w, double h) : width(w), height(h) {

 // Define member function implementations
 double Rectangle::area() const {
     return width * height;

 double Rectangle::perimeter() const {
     return 2 * (width + height);

You can create instances of the class and use its member functions:

 Rectangle r1;               // Create a default rectangle (0x0)
 Rectangle r2(3.0, 4.0);     // Create a rectangle with width 3.0 and height 4.0

 double r1_area = r1.area(); // Calculate the area of r1
 double r2_perimeter = r2.perimeter(); // Calculate the perimeter of r2

User-defined types allow you to create complex data structures and objects that can represent various entities and behaviors in your C++ programs. You can also implement constructors, destructors, and operator overloads to customize the behavior of your user-defined types as needed.


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