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pointers,virtual functions and polymorphism

The document presents an overview of pointers, virtual functions, and polymorphism in C++. It explains the significance of pointers in memory management and achieving polymorphism, along with rules and applications of virtual functions in object-oriented programming. Additionally, it discusses the types of polymorphism, its importance, and benefits in coding simplicity and extensibility.

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Dr. BABASAHEB AMBEDKAR TECHNOLOGICAL UNIVERSITY Presentation on Pointers , Virtual Functions and Polymorphism. By , Ruturaj Nalawade Sanjay Bidkar Swapnil Sarwade Under the Guidance of , Mrs . Ladda
POINTERS
INTRODUCTION Pointers are the variables which holds the addresses of other variables. Pointer variables are denoted by „ * ptr ‟ Pointers are the derived data types.
INTRODUCTION – CONT. E.g. := { int i , *j; i= 3; j = &i; cout<<“The value of i is t”<<i<<endl; cout<<“The value of *j is t”<<*j; } Output : : The value of i is 3 The value of *j is 3
INTRODUCTION – CONT. E.g. := { int i , *j; i= 3; j = &i; cout<<“The value of i is t”<<i<<endl; cout<<“The value of *j is t”<<*j; * j } Output : : The value of i is 3 The value of *j is 3
Introduction - Cont.  How the *j gets the value of i ? int i , *j ; Variable i j Names Value Memory 65524 65522 Address
Introduction - Cont.  How the *j gets the value of i ? int i , *j ; i=3; Variable i j Names Value 3 Memory 65524 65522 Address
Introduction - Cont.  How the *j gets the value of i ? int i , *j ; i=3; j=&i; Variable i j Names Value 3 65524 Memory 65524 65522 Address *j refers to the value at address j.
INTRODUCTION – CONT. Pointers are used for memory management and achieving polymorphism. C++ adds the concept of CONSTANT POINTER & POINTER TO A CONSTANT . :=
INTRODUCTION - CONT. 1. Constant Pointer :: Declaration = data type * const pointer
INTRODUCTION - CONT. 2. Pointer to a Constant :: data type const * pointer 3. const data type * const pointer
POINTERS TO OBJECTS - Pointers can point to an object created by class . Declaration : classname object; classname * pointer; Definition : pointer = & object;
POINTERS TO OBJECTS - CONT. Object pointers are useful in creating objects at run time. We can also use an object pointer to access the public members & member function of an object , by using „->‟ operator and the object pointer .
POINTERS TO OBJECTS –CONT. E.g. pointer -> getdata( ); We can also use ( * pointer ) . function( );
THIS POINTER C++ uses keyword „ this ‟ to represent an object that invokes a member function. E.g. The function call A. max( ) will set the pointer this to the address of the object A. E.g. To access private variables inside a member function a=123; or this -> a = 123;
THIS POINTER - APPLICATIONS In operator overloading using member function we use implicitly 'this‟ pointer. The another important application of the pointer 'this' is to return the object it points to .
POINTERS TO DERIVED CLASS Pointers to objects of a base class are type compatible with pointers to objects of a derived class. A single pointer variable can be made to point to objects belonging to different classes.
POINTERS TO DERIVED CLASS – CONT. e.g. B *cptr; B b; D d; cptr = & b; we can also make cptr to point to the object d as follows: cptr = & d
POINTERS TO DERIVED CLASS – CONT. Base Class Derived Class Public: a,b Public / Private / Private / Protected : Protected: c,d e,f,g,h If cptr = & d; cptr a,b
POINTERS TO DERIVED CLASS – CONT. This shows that , although a base pointer can be made to point to any number of derived objects, it can not directly access the members defined by a derived class. To access the members defined by a derived class , cast base pointer to the derived class type.
POINTERS TO DERIVED CLASS – CONT.  E.g . Casting dptr -> show ( ) ; ( ( DC * ) bptr ) -> show ( ) ;
VIRTUAL FUNCTIONS
VIRTUAL FUNCTION The application of polymorphism is the ability to refer the objects without any regard to their classes. This necessitates the use of a single pointer variable to refer to the objects of different classes.
VIRTUAL FUNCTION – CONT. By making the function 'virtual' in base class C++ determines which function to use at run time based on the type of object pointed to by the base pointer , rather than the type of the pointer. Runtime polymorphism is achieved only when a virtual function is accessed through a pointer to the base class.
VIRTUAL FUNCTIONS - RULES 1. The virtual functions must be members of some class. 2. They cannot be static members. 3. They are accessed by using object pointers. 4. A virtual function can be friend of other function. 5. A virtual function in a base class must be defined , even though it may not be used.
RULES –CONT. 6. We cannot have a virtual constructors, but we can have virtual destructors. 7. While a base pointer can point to any type of derived object, the reverse is not true.
RULES –CONT. 8. The prototypes of the base class version of a virtual function and all the derived class versions must be identical. 9. When a base pointer points to a derived class , incrementing or decrementing it will not make it to point to the next object of the derived class.
RULES –CONT. 10.If a virtual function is define in the base class ,it need not be necessarily redefined in the derived class.
POLYMORPHISM
POLYMORPHISM  Polymorphism is crucial feature of Object Oriented Programming.  Polymorphism simply means one name having multiple forms.
POLYMORPHISM - CONT.  “Polymorphism is the genie in OOP who takes instruction from clients and properly interprets their wishes.” – Ira Pohl, “Object Oriented Programming using C++”.
POLYMORPHISM – CONT. Definition: Polymorphism is the ability to create a variable, a function or an object that has more than one form.
EXAMPLE: For example: The + (plus) operator in C++: 4+5 <-- Integer addition 3.14 + 2.0 <-- Floating point addition s1 + "bar" <-- String concatenation!
TYPES OF POLYMORPHISM Compile-time Run-time Polymorphism Polymorphism
TYPES OF POLYMORPHISM  In compile time polymorphism, compiler is able to select the appropriate function a particular call at the compile time.  In run time polymorphism, an appropriate member function is selected while the program is running.
BENEFITS OF POLYMORPHISM  Simplicity: This makes your code easier for you to write and easier for others to understand.  Extensibility: Polymorphism design and implements system that are more extensible.
REFERENCES : Let us C++ – by Yeshwant Kanetkar. Object Oriented Programming with C++ –by E . BALAGURUSAMY. Internet.
THANK YOU !!