In the Object-Oriented Programming (OOP) paradigm, objects and classes are the primary building blocks. They help us model and solve real-world problems efficiently.

Class

In C++, a class is a blueprint for creating objects. It can be compared to a factory's mould that gives shape to its products. For example, consider a class BankAccount. All bank accounts, regardless of who owns them, have some common characteristics such as an account number, balance, and operations like deposit, withdrawal, and balance inquiry. A class encapsulates these common properties and behaviors.

Object

On the other hand, an object is an instance of a class. Going by our banking analogy, each customer's account is an object of the class BankAccount. Each object has access to all the properties and behaviors defined in the class, but its state (its variables' values) is independent of other objects. For instance, two BankAccount objects will have different account numbers and balances.

Understanding this Class-Object relationship is essential for writing efficient, modular, and bug-resistant OOP code. Below is a simple example of a class and its objects in C++.

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#include <iostream>

using namespace std;

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// Define a simple BankAccount class

class BankAccount {

public:

  string account_number;

  double balance = 0.0;

​

  void deposit(double amount) {

    balance += amount;

    cout << amount << " deposited. Current balance: " << balance << endl;

  }

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  void withdraw(double amount) {

    if (balance - amount >= 0) {

      balance -= amount;

      cout << amount << " withdrawn. Current balance: " << balance << endl;

    } else {

      cout << "Insufficient balance." << endl;

    }

  }

};

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int main() {

  // Use the BankAccount class to create two bank account objects

  BankAccount johnsAccount;

  BankAccount amysAccount;

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