Functions are the building blocks of C++ and are used to reduce program size by calling reusable code in different places. Functions can return values using the return statement. Function prototypes provide interface details like data types and arguments to the compiler. Parameters can be passed by reference, allowing the calling function to modify the original argument. Inline and recursive functions are also discussed. Classes are user-defined data types that contain data members and member functions. Member functions can be defined inside or outside the class.

2. FUNCTIONS
• Function is the building block of C++.
• Used to reduce the size of the program by
calling and using them in different places in
the program.
• main()Function returns an integer value.
int main();
int main(int arg);
 Function return a value using return statement.

3. FUNCTION PROTOTYPE
• The function interface to the compiler by
giving the details like number, data type,
arguments – function prototype.
• It is a declaration statement in calling program
type function name (argument list);
Eg:
float volume (int x, float y, z);
float volume (int, float, float);

4. CALL BY REFERENCE
• C++ permits to pass the parameters to the
functions by reference variable.
• When it is passed the formal argument act as
the actual argument in the calling function
void swap(int a, int b)
{
int t = a;
a = b;
b = t;
}

5. INLINE & RECURSION FUNCTION
• An inline function is a function that is expanded in
line when it is invoked.
• The compiler replaces the function call with the
corresponding function code.
inline function header
{
function body
}
• It send a request not a command
• Recursion means function call by itself ie one of the
statement in the function definition makes a call to
the same in which it is present.

6. CLASS
• Collection of objects – CLASS
• The entire set of data and code of an object can
be made a user defined data type by using
class.
• 2 Parts:
– Class Declaration – describe the type & scope of
its members
– Class function definitions – how the class
function are implemented.

7. • General format:
class class-name
{
private:
variable declaration;
function declaration;
public:
variable declaration;
function declaration;
};
Class item
{
int number;
float cost;
public:
void getdata(int a, float b);
void putdata(void);
};

8. • Class member – the class body contains the
declaration of variables and functions.
• Data member – variables declared inside the
class.
• Member function – the function declared
inside the class.

9. DEFINING MEMBER FUNCTIONS
• Done by 2 ways
1. Outside the class definition
2. Inside the class definition

10. Outside the class definition
• Member function declared inside the class has to be
defined separately outside the class.
return-type class-name :: function-name
(argument declaration)
{
function body;
}

11. void item :: getdata (int a , float b)
{
number = a;
cost = b;
}
void item :: putdata (void)
{
cout<< “Number : “ << number;
cout << “Cost : “ << cost;
}

12. Inside the class definition
• It is to replace the function declaration by the actual
function definition inside the class.
class item
{
int number;
float cost;
public:
void getdata(int a, float b);
void putdata(void)
{
cout << number;
cout << cost;
}
};