OOP principles overview in C++ - Step-by-Step Execution

Concept Flow - OOP principles overview

Start

↓

Encapsulation

↓

Inheritance

↓

Polymorphism

↓

Abstraction

↓

End

This flow shows the four main OOP principles in order: Encapsulation, Inheritance, Polymorphism, and Abstraction.

Execution Sample

C++

#include <iostream>

class Animal {
  public:
    virtual void sound() { }
};

class Dog : public Animal {
  public:
    void sound() override { std::cout << "Woof"; }
};

Defines a base class Animal and a derived class Dog that overrides the sound method.

Execution Table

Step	Action	Evaluation	Result
1	Create Animal object	Animal a;	Object a created
2	Call a.sound()	a.sound();	No output (empty method)
3	Create Dog object	Dog d;	Object d created
4	Call d.sound()	d.sound();	Outputs: Woof
5	Assign Dog to Animal pointer	Animal* ptr = &d;	Pointer ptr points to Dog object
6	Call ptr->sound()	ptr->sound();	Outputs: Woof (polymorphism)
7	End		Execution stops

💡 Program ends after demonstrating polymorphism with virtual function call

Variable Tracker

Variable	Start	After Step 1	After Step 3	After Step 5	Final
a	none	Animal object	Animal object	Animal object	Animal object
d	none	none	Dog object	Dog object	Dog object
ptr	none	none	none	Points to Dog object	Points to Dog object

Key Moments - 3 Insights

Why does calling sound() on Animal pointer to Dog object output 'Woof'?

Because sound() is declared virtual in Animal, the call uses Dog's overridden method (see execution_table step 6). This is polymorphism.

What is encapsulation in this example?

Encapsulation means bundling data and methods inside classes like Animal and Dog, hiding internal details from outside (shown by class definitions).

How does inheritance work here?

Dog inherits from Animal, so Dog has Animal's interface and can override methods like sound() (see class Dog : public Animal).

Visual Quiz - 3 Questions

Look at the execution_table, what does step 4 output?

A No output

B Woof

C Error

D Animal sound

💡 Hint

Check the 'Result' column in execution_table row for step 4

At which step does polymorphism happen?

A Step 2

B Step 4

C Step 6

D Step 3

💡 Hint

Look for virtual function call through base class pointer in execution_table

If sound() was not virtual, what would ptr->sound() output at step 6?

A No output

B Woof

C Compile error

D Animal sound

💡 Hint

Without virtual, base class method is called regardless of pointer type

Concept Snapshot

OOP Principles Overview in C++:
- Encapsulation: Bundle data and methods in classes
- Inheritance: Derive new classes from existing ones
- Polymorphism: Use virtual functions to override behavior
- Abstraction: Hide complex details behind simple interfaces
Use virtual keyword for polymorphism.

Full Transcript

This visual execution shows the four main OOP principles using C++ code. We start by creating an Animal object with an empty sound method. Then we create a Dog object that inherits Animal and overrides sound to print 'Woof'. Calling sound on Dog outputs 'Woof'. Assigning Dog to an Animal pointer and calling sound demonstrates polymorphism because the Dog's method runs. Encapsulation is shown by bundling data and methods inside classes. Inheritance lets Dog reuse Animal's interface. Polymorphism uses virtual functions to call the right method at runtime. The quiz checks understanding of outputs and polymorphism behavior.