Object Oriented Programming using C++ Unit 1

Object Oriented Programming Using C++
Prepared by
Mr. Nagesh Pratap Singh
JMS GROUP OF INSTITUTIONS, HAPUR
DEPARTMENT OF COMPUTER APPLICATION

C++ FUNCTIONS
A function is a block of code which only runs when it is
called.
You can pass data, known as parameters, into a
function.
Functions are used to perform certain actions, and they
are important for reusing code: Define the code once, and
use it many times

• The main( )Functon ;
ANSI does not specify any return type for the main ( ) function which is the starting point for the execution of a
program .
The definition of main( ) is :-
main()
{
//main program statements
}
This is property valid because the main () in ANSI C does not return any value. In C++, the main () returns a
value of type int to the operating system.
The functions that have a return value should use the return statement for terminating.
The main () function in C++ is therefore defined as follows.
int main( )
{
--------------
--------------
return(0)
}
Since the return type of functions is int by default, the key word int in the main( ) header is optional

INLINE FUNCTION:
• To eliminate the cost of calls to small functions C++ proposes a new feature called inline function. An inline
function is a function that is expanded inline when it is invoked .That is the compiler replaces the function
call with the corresponding function code.
The inline functions are defined as follows:-
inline function-header
{
function body;
}
Example:
inline double cube (double a)
{
return(a*a*a);
}
The above inline function can be invoked by statements like c=cube(3.0);
d=cube(2.5+1.5);
remember that the inline keyword merely sends a request, not a command to the compliler. The compiler may
ignore this request if the function definition is too long or too complicated and compile the function as a normal
function

SOME OF THE SITUATIONS WHERE
INLINE EXPANSION MAY NOT WORK ARE:
1. For functions returning values if a loop, a switch or a go
to exists.
2. for function s not returning values, if a return statement
exists.
3. if functions contain static variables.
4. if inline functions are recursive,.

Object Oriented Programming using C++ Unit 1

DEFAULT ARGUMENTS IN C++
• A default argument is a value provided in a function
declaration that is automatically assigned by the compiler
if the calling function doesn’t provide a value for the
argument. In case any value is passed, the default value
is overridden.
• 1) The following is a simple C++ example to demonstrate
the use of default arguments. Here, we don’t have to write
3 sum functions; only one function works by using the
default values for 3rd and 4th arguments.

CPP PROGRAM TO DEMONSTRATE DEFAULT
ARGUMENTS
#include <iostream>
using namespace std;
int sum(int x, int y, int z = 0, int w = 0)
{
return (x + y + z + w);
}
int main()
{
cout << sum(10, 15) << endl;
cout << sum(10, 15, 25) << endl;
cout << sum(10, 15, 25, 30) << endl;
return 0;
}

FUNCTION OVERLOADING:
Function overloading is a feature of object-oriented
programming where two or more functions can have the
same name but different parameters. When a function
name is overloaded with different jobs it is called Function
Overloading. In Function Overloading “Function” name
should be the same and the arguments should be
different. Function overloading can be considered as an
example of a polymorphism feature in C++.
If multiple functions having same name but parameters of
the functions should be different is known as Function
Overloading.

#include <iostream>
using namespace std;
void add(int a, int b)
{
cout << "sum = " << (a + b);
}
void add(double a, double b)
{
cout << endl << "sum = " << (a + b);
}
int main()
{
add(10, 2);
add(5.3, 6.2);
return 0;
}

WHY USE CLASSES INSTEAD OF STRUCTURES
• Classes and structures are somewhat the same but
still, they have some differences. For example, we
cannot hide data in structures which means that
everything is public and can be accessed easily which
is a major drawback of the structure because structures
cannot be used where data security is a major concern.
Another drawback of structures is that we cannot add
functions in it.

CLASSES IN C++
• Class is a group of objects that share common
properties and relationships .In C++, a class is a
new data type that contains member variables
and member functions that operates on the
variables. A class is defined with the keyword
class. It allows the data to be hidden, if
necessary from external use.

CLASS DECLARATION
Generally a class specification has two parts:-
a) Class declaration
b) Class function definition
Syntax:-
class class-name
{
private:
variable declarations;
function declaration ;
public:
variable declarations;
function declaration;
};

CREATING OBJECTS:
Once a class has been declared we can create variables of that type by using the
class name.
Example: item x;
creates a variables x of type item.
In C++, the class variables are known as objects. Therefore x is called an object of
type item.
item x, y ,z also possible.
class item
{ -----------
-----------
----------- }x ,y ,z;
would create the objects x ,y ,z of type item.

ACCESSING CLASS MEMBER:
The private data of a class can be accessed only through the member functions of that class.
The main() cannot contains statements that the access number and cost directly.
Syntax: object name.function-name(actual arguments);
Example:- x. getdata(100,75.5);
It assigns value 100 to number, and 75.5 to cost of the object x by implementing the getdata() function .
Example: class xyz {
Int x;
Int y;
public:
int z;
};
xyz p;
p. x =0; error , x is private
p. z=10; ok ,z is public

DEFINING MEMBER FUNCTION:
Member can be defined in two places
• Outside the class definition
• Inside the class function
OUTSIDE THE CLASS DEFlNATION :-
Member function that are declared inside
a class have to be defined separately
outside the class.Their definition are very
much like the normal functions.
Syntax:
return type class-name::function-name(argument
declaration )
{
function-body
}
Example:
void item :: getdata (int a , float b )
{
number=a; cost=b;
}
void item :: putdata ( void)
{
cout<<”number=:”<<number<<endl;
cout<<”cost=”<<cost<<endl;
}

INSIDE THE CLASS DEFINATION:
Another method of defining a member function is to replace the function declaration by the
actual function definition inside the class .
Example:
class item
{
public:
Intnumber; float cost;
void getdata (int a ,float b);
void putdata(void)
{
cout<<number<<endl; cout<<cost<<endl;
}
};

A C++ PROGRAM WITH CLASS:
# include< iostream. h>
class item
{
public:
int number; float cost;
void getdata ( int a , float b);
void putdala ( void)
{
cout<<“number:”<<number<<endl;
cout<<”cost :”<<cost<<endl;
}
};
void item :: getdata (int a , float b)
{
number=a; cost=b;
}
main ( )
{
item x;
cout<<”nobjectx”<<endl;
x. getdata(100,299.95);
x .putdata();
item y;
cout<<”n object y”<<endl;
y. getdata(200,175.5);
y. putdata();
}

Object Oriented Programming using C++ Unit 1

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