C++ Classes & Objects: A Beginner's Guide

Welcome to our exploration of Classes and Objects in C++ programming!A class is like a blueprint or template that defines how something should be structured.From this single blueprint, we can create multiple objects, each following the same structure but with its own unique characteristics.Let's look at a practical example using a Car class. The class defines what properties and behaviors all cars should have.From this Car class, we can create different car objects, each with its own specific values for color, model, and speed.In C++, we define a class using the class keyword, followed by the class name. Inside the class, we declare our properties as private data members and our behaviors as public member functions.To create objects from our Car class, we simply declare variables of type Car. Each object will have its own separate copy of the properties defined in the class.Let's review the key points about classes. They serve as blueprints for creating objects, define both properties and behaviors, and enable code reusability.Now that we understand what classes and objects are, let's move on to explore their structure and members in more detail.A C++ class consists of two main components: data members and member functions.Data members are variables that store the object's properties. They are typically declared as private to protect the data.Member functions are methods that can access and modify these data members. They are usually declared as public to provide an interface.Let's examine how data members store the essential properties of our Car class.Member functions provide controlled access to these properties, defining how we can interact with the object.This structure demonstrates encapsulation, a key principle of object-oriented programming.Access specifiers control how members can be accessed. Public members can be accessed directly, while private members are only accessible through public member functions.The getter and setter pattern provides controlled access to private data members, allowing for validation and access control.This class structure forms the foundation for creating and using objects, which we'll explore next.Objects are created from classes using special member functions called constructors.The default constructor takes no parameters and initializes object members to default values.A parameterized constructor allows us to initialize an object with specific values.The copy constructor creates a new object as a copy of an existing object.Let's see how to create objects using these different constructors.When objects are created, each gets its own space in memory to store its data members.We use the dot operator to access object members. Changes to one object don't affect others.Notice how car3, which was copied from car2, maintains its original values independently.Member functions can be defined either inside or outside of the class definition. Here's how we define them inside the class:When defining member functions outside the class, we need to use the scope resolution operator, which looks like two colons.Getter and setter methods are special member functions that provide controlled access to private data members.There are several types of member functions, each serving a specific purpose in class design.Member functions can interact with each other and with the object's data members. Here's an example using a bank account class:Notice how the public member functions deposit and withdraw both call the private updateHistory function, demonstrating how member functions work together.Now let's implement a complete Student class to manage student records and grades.Our Student class has private data members for student ID, name, grades, and GPA. The constructor initializes these basic attributes.Let's add member functions to manage grades and calculate GPA.The addGrade method adds a new grade to the student's record and automatically updates their GPA. The updateGPA method calculates the average of all grades.We'll also need getter methods to access private data members and a display method to show student information.These methods allow us to safely access student data while maintaining encapsulation.Let's see how to use our Student class in a main program.We create two student objects, Alice and Bob, and add their grades. Notice how each student maintains their own separate grade records.When we run this program, here's what the output looks like.Each student's information is displayed with their current GPA, calculated from their individual grades.