CLASSES & OBJECTS

1. CLASSES & OBJECTS PREPARED BY: Roop Narayan PGT(Comp.Sc.) KV Kokrajhar (Assam)

2. CLASS DEFINITION A CLASS IS A WAY TO WIND THE DATA DESCRIBING AN ENTITIY AND ITS ASSOCIATED FUNCTIONS TOGETHER. IN C++, CLASS MAKES A DATA TYPE THAT IS USED TO CREATE OBJECTS OF THIS TYPE.

3. CLASS DEFINITION classclass_name { private: variable declaration; function declaration; protected: variable declaration; function declaration; public: variable declaration; function declaration; }; Keywords: In bluecolour Identifiers: In black colour

4. CLASS METHOD DEFINTION • OUTSIDE THE CLASS DEFINITION return type class_name:: function_name(parameter list) { function body } Where return type (Any fundamental data types like void, int, float…) : : (scope resolution operator, specifies that the scope of the function is restricted to the class name)

5. EXAMPLE “OUTSIDE CLASS DEFINITION” void BOOK :: input( ) { cout<<“\n Enter Book No:”; cin>>book_no; cout<<“\n Enter Book Title:”; gets(book_title); cout<<“Enter Price:”; cin>>price; }

6. CLASS METHOD DEFINITION • INSIDE THE CLASS DEFINITION When a member function is defined inside a class definition. • A function defined inside a class is an inline function. • A function can be declared inline by placing the keyword inline before it. • Inline function are best for small functions that are called often. • An inline function definition should be placed above all the functions that call it. • Inline functions executes faster than the normal functions as function calling overheads are saved, however is a memory penalty.

7. EXAMPLE“INSIDE CLASS DEFINITION” class Book { private: intbook_no; char book_title[20]; float price; Float total_cost(int n) //inline function { float total; total = n*price; // inline function definition return total; } public: intbook_sl_no; void book_info_display( ); };

8. EXAMPLE INLINE FUNCTION DEFINITION USING “inline” KEYWORD inline function definition, outside the definition of class with keyword inline: inline void maxi( int a, int b) // inline function { cout<<(a > b ? a : b) }

9. REFERENCING CLASS MEMBERS Class members refer with the help of object. • Creation of object: class_nameobject_name; or class_name obj1, obj2, obj3,…………….; • Referring data member(by dot operator) object_name . data_member_name = value; Referring member function(with dot operator) object_name . Function_name(actual_arguments);

10. EXAMPLE(REFERENCING CLASS MEMBERS) CREATION OF AN OBJECT: Book b1; // Book is a class, b1 is an object  ACCESSING DATA MEMBER(only public data member outside class definition) b1 . bool_sl_no = 1; //book_sl_no is data member • ACCESSING/CALLING MEMBER FUNCTION(only public member function outside class definition) b1 . book_info_display( ); // book_info_display is a member function

11. MEMORY ALLOCATION OF OBJECTS Member functions are created and placed in the memory space only once when the class is defined. The memory space is allocated for objects data members only when the objects are declared. No separate space is allocated for member functions when the objects are created.

12. THANKS