Object-Oriented Programming Basics

Study Notes

Objects

An object is a real-world entity characterized by Reference/Identity, Behavior, & Property.
Objects serve as the fundamental unit in object-oriented programming, encapsulating both data and functions.
An object is an instance of a class, similar to how a cake is an instance of a recipe.
Each object created from a class inherits attributes and behaviors defined in the class.

Classes

A class is a collection or template of objects, acting as a blueprint that defines properties and behaviors.
Classes establish the structure, behavior, and attributes that an object will have.
To create a class, the class keyword is used, following a specific syntax.

Class Syntax

The basic syntax for defining a class is:

class class_name {
    // Access specifier;
    // Data member;
    // Member function / Methods;
};

Access Specifiers

Access specifiers control the visibility and accessibility of class members, enforcing data hiding.
There are three primary types of access specifiers in C++:
- Public: Members are accessible from anywhere in the program.
- Private: Members are only accessible within the class itself.
- Protected: Members are accessible within the class and its subclasses.

Access Specifier Syntax

The syntax for defining access specifiers in a class:

class ClassName {
    private:
        // Declare private members/methods here.
    public:
        // Declare public members/methods here.
    protected:
        // Declare protected members/methods here.
};

Example Class

An example of a simple class in C++:

class MyClass {
    public:
        int publicVar;    // Accessible from anywhere
    private:
        int privateVar;   // Accessible only from within the class
    protected:
        int protectedVar; // Accessible from class and its subclasses

    public:
        // Constructor definition
        MyClass() { 
            publicVar = 1; 
            privateVar = 2; 
            protectedVar = 3; 
        }

        // Method to display values
        void displayValues() { 
            cout << "Public: " << publicVar << " Private: " << privateVar << " Protected: " << protectedVar; 
        }
};

The constructor initializes the properties of the object when an instance is created.

Description

This quiz covers the fundamental concepts of object-oriented programming, including objects, classes, and access specifiers. Understanding these principles is essential for creating organized and efficient code in any object-oriented language. Test your knowledge on how classes and objects interact and the syntax used to define them.