VIRTUAL FUNCTIONS IN C++ Virtual Function என்பது C++-இல் Runtime Polymorphism உருவாக்க பயன்படும் முக……
VIRTUAL FUNCTIONS IN C++
A virtual function is a member function in a base class declared using the virtual keyword and redefined in a derived class to achieve runtime polymorphism. Tamil mixed: Base class-ல் virtual keyword பயன்படுத்தி declare செய்யப்பட்டு, deriv…
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47 programs 10 MCQs v2
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Definition
A virtual function is a member function in a base class declared using the virtual keyword and redefined in a……
Simple Explanation
ஒரு Base class: class Animal ……
இதுதான் Virtual Function-ன் ம……
Explanation
Why virtual function is needed
Normal function call compile time-ல் decide ஆகலாம். ஆனால் சில நேரங்களில் எந்த object function execute ஆக வேண்……
Explanation
எந்த sound() execute ஆக வேண்டும்? Dog என்றால் bark Cat எ……
Concept
Main concept
Virtual Function ↓ Function Overriding ↓ ……
Syntax
Derived class
Explanation
Program - without virtual function
முதலில் virtual இல்லாமல் என்ன……
Explanation
return 0; }…
Explanation
Why base class output?
Pointer declaration: Base *ptr; Pointer type: Base Function virtual இல்லை. அதனால் compiler pointer type-ஐ ப……
Explanation
return 0; }…
Explanation
Line explanation
Base Class class Base Parent class உருவாக்கப்படுகிறது. Virtual Function virtual void show() இங்கு: virtual co……
Explanation
Base pointer
Base *ptr; இது Base class poi……
Explanation
Derived object
Derived d; Derived object உரு……
Explanation
Pointing derived object
ptr = &d; இப்போது: Base point……
Explanation
Function call
ptr->show(); show() virtual என்பதால் runtime system actual ……
Flow
Program Start ↓ Create Derived object d ↓ Create Base pointer ptr ↓ ptr = &d ↓ ptr->show() ↓ Is show() virtua……
Explanation
Example
void show() without virtual. Dynamic Binding Function se……
Explanation
Virtual function and polymorphism
Polymorphism means: One interface, many forms. Anim……
Explanation
ஒரே statement. ஆனால் different outputs:……
Real Life Example
Real-time example
#include using namespace std; c……
Program
Next
Actual object: Cat Call:…
Explanation
Key point
ஒரே: Animal *ptr; pointer, பல derived ob……
Explanation
Function overriding
Virtual function பொதுவாக Function Overriding உடன் பயன்படுத்தப்படுகிறது. Base: virtual void show() Derived: vo……
Real Life Example
Example - overloading
void add(int a, int b); void add(double a……
Real Life Example
Example - overriding
class Base { public: virtual void show() { } }; clas……
Explanation
Override keyword
Modern C++-ல் derived class override ……
Program
Example
Explanation
இது compiler-க்கு: இந்த function Base class virtual function-ஐ override செய்ய வேண்டும் என்று தெரிவிக்கிறது. [……
Important
Important rule
Base function virtual என்றால் Derive……
Program
Example
Explanation
Derived::show() virtual behavior தொடரும……
Program
Example
Explanation
Call: A *ptr; C obj;…
Why? Actual object: C…
Explanation
Pure virtual function
Virtual Function-ன் very important ……
Program
Example
Explanation
= 0 என்பது pure virtual funct……
Explanation
Pure virtual function meaning
Base class: virtual void draw() = 0; என்று சொல்வது: Eve……
Explanation
Abstract class
ஒரு class-ல் குறைந்தது ஒரு pure vir……
Program
Example
Explanation
Shape is abstract class.…
Explanation
Can we create abstract class object?
No. Wrong: Shape s; Abstract class object direc……
Program
Pure virtual function program
Explanation
Shape *ptr = &c;…
Explanation
return 0; }…
Explanation
Virtual destructor
Virtual functions topic-ல் மிகவும் important interview concept: Virtual Destructor Suppose: Base *ptr = new D……
Explanation
delete ptr; return 0; }…
Correct destruction sequence.…
Explanation
Why virtual destructor?
When deleting through base pointer: delete ptr; Runtime ……
Explanation
Can constructor be virtual?
No. C++ constructor cannot be virtual. Reason: Object construction இன்னும் co……
Explanation
Can destructor be virtual?
Yes. virtual ~Base() is valid……
Explanation
Can static function be virtual?
No. A static member function belongs to class, not to a particular object……
Explanation
Can friend function be virtual?
A friend function is not a member function. Virtual function mus……
Explanation
Can global function be virtual?
No. Virtual functions are mem……
Explanation
Virtual function rules
Important rules: Virtual function must be a class member function. It is declared using virtual in base class……
Explanation
Base reference with virtual function
Virtual function pointer மட்டும் அ……
Program
Example
Explanation
Base &ref = d; ref.show(); re……
Program
Both support virtual dispatch
Program
and
Important
Object slicing - important
Suppose: Derived d; Base b = d; இங்கு object copy செய்வதால் derived-specific part slice ஆகலாம……
Real Life Example
Real-life example - payment
#include using namespace std; ……
Runtime Polymorphism
Explanation
Different objects different b……
Extensibility
Explanation
New derived classes add செய்வ……
Flexible Design
Explanation
Base interface மூலம் differen……
Code Reusability
Explanation
Common interface reuse செய்யல……
Maintainability
Explanation
Large OOP systems-ல் clean ar……
Explanation
Disadvantages
Virtual function dispatch-க்கு small runtime overhead இருக்கலாம். Object may also need i……
Explanation
Vtable and vptr
Exam/interview level-ல் virtual functions எப்படி internally work ஆகும் என்பதை அறிந்திருக்கலாம். Many C++ impl……
Important
C++ standard itself implementation must use an actual ……
Common Mistake
Common error 1
Base function virtual இல்லாமல் runtime poly……
Common Mistake
Common error 2
Function signature mismatch. Base: virtual void show(in……
Common Mistake
Common error 3
Abstract class object உருவாக்குவது. Wrong: ……
Common Mistake
Common error 4
Destructor virtual செய்யாமல் base pointer மூலம் de……
Memory Trick
VIRTUAL ↓ RUNTIME ↓ ACTUAL OBJECT ↓ DERIVED FUN……
MCQ
Virtual function is used to a……
MCQ
Which keyword is used to decl……
MCQ
Virtual function binding occu……
MCQ
Which concept works with virt……
MCQ
Virtual function should norma……
MCQ
A pure virtual function conta……
MCQ
A class containing a pure vir……
MCQ
Can constructor be virtual?…
MCQ
Can destructor be virtual?…
MCQ
Which supports runtime polymorphism……
Program
Exam program
Explanation
return 0; }…
Interview Point
What is a virtual function? A member function declared with virtual in a base class……
Interview Point
What is late binding? Function cal……
Interview Point
Difference between virtual and pure virtual? virtual void show() { } Vi……
Important
Remember these four lines: virtual ↓ overriding ↓ base pointer/ref……
Practice
Write programs using virtual functions for: Animal → Dog, Cat Shape → Circle, Rectangl……
Summary
Virtual Function | ├── Declared using virtual | ├── Base class member function | ├── Overridden in derived cl……
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