Object oriented concepts:
Object-Oriented
Programming or OOPs refers to languages that uses objects in programming.
Object-oriented programming aims to implement real-world entities like
inheritance, hiding, polymorphism etc in programming.
The
main aim of OOP is to bind together the data and the functions that operate on
them so that no other part of the code can access this data except that
function.
Principles (Features) of Object Oriented Programming:
1.
Encapsulation
2.
Data abstraction
3.
Polymorphism
4.
Inheritance
5.
Dynamic binding
6.
Message passing
Encapsulation: Wrapping
of data and functions together as a single unit is known as encapsulation. By default
data is not accessible to outside world and they are only accessible through
the functions which are wrapped in a class. Prevention of data direct access by
the program is called data hiding or information hiding
Data abstraction: Abstraction
refers to the act of representing essential features without including the back
ground details or explanation. Classes use the concept of abstraction and are
defined as a list of attributes such as size, weight, cost and functions to
operate on these attributes. They encapsulate all essential properties of the
object that are to be created. The attributes are called as data members as
they hold data and the functions which operate on these data are called as
member functions.
Class
use the concept of data abstraction so they are called abstract data type (ADT).
Polymorphism: Polymorphism
comes from the Greek words “poly” and “morphism”. “poly” means many and
“morphism” means form i.e.. many forms. Polymorphism means the ability to take
more than one form. For example, an operation have different behavior in
different instances. The behavior depends upon the type of the data used in the
operation.
Different
ways to achieving polymorphism in C++ program are:
1) Function overloading 2) Operator overloading
Inheritance: Inheritance
is the process by which one object can acquire the properties of another. Inheritance
is the most promising concept of OOP, which helps realize the goal of constructing
software from reusable parts, rather than hand coding every system from
scratch. Inheritance not only supports reuse across systems, but also directly
facilitates extensibility within a system. Inheritance coupled with polymorphism
and dynamic binding minimizes the amount of existing code to be modified while enhancing
a system.
When the class child, inherits the class parent, the class
child is referred to as derived class (sub class) and the class parent as a
base class (super class). In this case, the class child has two parts: a
derived part and an incremental part. The derived part is inherited from the
class parent. The incremental part is the new code written specifically for the
class child.
Dynamic binding: Binding
refers to linking of procedure call to the code to be executed in response to
the call. Dynamic binding(or late binding) means the code associated with a
given procedure call in not known until the time of call at run time.
Message passing: An object
oriented program consists of set of object that communicate with each other. Objects
communicates with each other by sending and receiving information. A message
for an object is a request for execution of a procedure and therefore invoke the
function that is called for an object and generates result.
Advantages and Applications of OOPS
Advantages (Benefits) of Object Oriented Programming (OOPs)
Reusability: In OOP‟ s programs
functions and modules that are written by a user can be reused by other users without any modification.
Inheritance: Through this we can eliminate redundant
code and extend the use of existing classes.
Data Hiding: The programmer can hide the data and
functions in a class from other classes. It helps the programmer to build the
secure programs.
Reduced complexity of a problem: The given problem can be viewed as a
collection of different objects. Each object is responsible for a specific
task. The problem is solved by interfacing the objects. This technique reduces
the complexity of the program design.
Easy to Maintain and Upgrade: OOP makes it easy to maintain and
modify existing code as new objects can be created with small differences to
existing ones. Software complexity can be easily managed.
Message Passing: The technique of message communication
between objects makes the interface with external systems easier.
Modifiability: it is easy to make minor changes in the
data representation or the procedures in an Object Oriented program. Changes
inside a class do not affect any other part of a program, since the only public
interface that the external world has to a class is through the use of methods.
Applications of OOP:
Real-time systems
Simulation and modeling
Object-oriented databases
Hypertext, hypermedia and expertext
AI and expert systems
Neural networks and parallel
programming
Decision support and office
automation systems
CIM/CAM/CAD
systems.
Applications of C++
C++ is a
versatile language for handling very large programs. It is suitable for
virtually any
programming
task including development of editors, compilers, databases, communication
systems and any complex real-life application systems.
Since C++ allows us to create hierarchy-related objects, we can build special object oriented libraries which can be used later by many programmers.
While C++ is able to map the real-world problem properly, the C part of C++ gives the language the ability to get close to the machine-level details.
C++ programs are easily maintainable and expandable. When a new feature needs to be implemented, it is very easy to add to the existing structure of an object.
Data types, new operators and keywords, type
conversion in C++
Data
Types:
The
language C++ supports all the data types available in ‘C’ language. The data
types of language C++ can be viewed as given bellow.
 |
| Data Types |
As shown
in above figure,
The
user-define data type Structure and union are same as that of the
implementation in C, there is small advantage in implementation of structure in
C++, that we will discuss later. The new data type which is not in C is the
“class”. The concept of the class is the main concept in C++ programming.
The
Library / Built-In data type consist of all the data types as that of the data
types used in C, the range and keyword used for these data type is similar to
C. There is little bit difference in size used in C and in C++.
The
derived data types, array, function. Pointer are also similar to the language
used in C. The language C++ introduces new data type as “reference”
Operators and Keywords:
C++ has
a rich set of operators. All operators in C are used as it is with their
meaning in C++ also.
The
various operators are:-
a.
Assignment Operator
b.
Arithmetic Operator
c.
Relational Operator
d.
Logical Operator
d.
Bit wise Operator
e.
Increment/Decrement operator
f.
Shortcut Operator
g.
Conditional Operator
h.
Special operator
Assignment
operator:
The assignment operator is
used to store the values of constants, variables, and result of an expression
and return value of a function into variable placed in left side.
Operator Symbol: =
Ex
: 1) a = 6; 2)
a = b; 3) a
= b+c;
Arithmetic
operators:
The arithmetic operators are
used to perform the basic operations like addition, subtraction,
multiplication, division
and modulus.
The operators are: Addition (+) , subtraction (–)
, multiplication (*) , Division ( / ), modulus
division (%)
Ex:
1) x=a+b; 2)
x=a-b; 3) x=a*b; 4) x=a/b; 5) x=a%b;
Increment/Decrement
operators:
The Increment operators ++ increase the value of variable by one.
The Decrement operators -- decrease the value of variable by one.
Ex :
i++,
++i,
i--,
--i.
Shortcut
operators:
When the arithmetic operation on value of a variable is to be performed
and assigned to the same variable, we can use shortcut assignment operator.
The operators are: +=, – =, *=, /=, %=
Ex:
A
+= 2; A -=
3;
A
*= 2; A /= 2;
A
%= 4;
Sizeof:
The sizeof
operator is used to find the size of the memory occupied by an variable
in terms of bytes.
Ex : a =
sizeof(int);
Relational
operators:
The
operators that do relationship tests with the operands are called relational
operators.
The
relational operators are:
< (is less than)
<= (is less than or equal to)
> (is greater than)
>= (is greater than or equal
to)
== (is equal to)
!= (is not
equal to)
Logical operators:
Logical
operators are used when more than one relationship should be considered in
evaluation.
It gives
either True value or False value.
The
operators are
AND
operator: &&
OR
operator: ||
NOT operator: !
The language C++ introduces some new operators which are:
1) << :- insertion operator (or output operator)
2) >> :- extraction operator (or input operator)
3) :: :- Scope
resolution operator
4) ::* :- pointer-to-member
declarator
5) ->* pointer-to-member
operator
6) .* pointer-to-member
operator
7) endl line
feed operator
8) new memory
allocation operator
Keywords:
The
keywords are the reserved words with specific meaning, these cannot be used and
programe names or variable names in programe or user define program name.
Some of
the keywords are:
auto
break case
catch char class const
continue
default delete do
double
else enum
extern
float for friend
goto
if inline int long
new
operator
private protected public register return
short
signed sizeof static struct
switch
template
this throw try
typedef union
unsigned
virtual void volatile
while
Mostly
used new keywords in C++ are new, class,
inline, private, protected, public, virtual, etc. These keywords plays very
important role in C++ programming.
The simple
programe in C++ can be written as
#include<iostream.h>
#include<conio.h>
void
main()
{
int a,b,c;
clrscr();
cout<<"Enter first number ";
cin>>a;
cout<<"Enter second number
";
cin>>b;
c = a + b;
cout<<"Addition is
"<<c;
getch();
}
In the
programe above
iostream.h:- is an header file containing the
information about input and output stream. i.e. input and output statements
used in C++.
Input statement:- The “cin” is the
statement used to read the values from keyboard. The general syntax of cin
statement is given as follows:
Syntax:
cin>>variable_name[>>var_name>>var_name…..];
here cin is the statement used to read
values from keyboard. The operator >> is known as “Extraction” or “get from” operator. It extracts (or takes) the value form the keyboard and
assign it to the variable.
int
a,b,c;
cin>>a;
cin>>b>>c;
Output statement:- The “cout” is the
statement used to display values on to the monitor. The general syntax of cout
statement is given as follows:
Syntax:
1)
cout<<variable_name[<<var_name<<var_name…..];
2) cout<<”Any data in double
quot..”[<<”…….”<<”var_name”<<…..];
3)
cout<<“string information”<<variable_name;
here cout is the statement used to display
values on monitor. The operator << is known as “Insertion” or “put to” operator. It inserts (or sends) the value of variable to the
monitor.
int
a,b;
a
= 90; b = 20;
cout<<a;
cout<<a<<b;
cout<<”The
value of A = “<<a<<” B = “<<b;
cout<<”The
addition is “<<a+b;
Classes & Objects
Class:
A Class
is an user define data type that can be treated like any other built-in data
type. The class is a way to bind data and its associated functions together.
The class allows the data and functions to be hidden form external user i.e.
form user, if necessary. When we are defining a class it means we are creating
new user define data type also known as abstract data type.
General form of a class declaration is:
class class_name
{
private:
variable declarations;
function declarations;
public:
variable declarations;
function declarations;
};
In above
declaration
Class is
a keyword used to declare class.
Private, public are the two visibility modes, these are also
called as access specifiers. These are
used to decide whether to allow user to make use of variables and or functions.
The public access specifier is allows user to make use of variables /
functions, whereas private access specifier is used to protect variables /
functions.
The variables declared under public / private / protected access
specifier are known as data members /
properties of class. The functions declared in class are called as method members of class. The method
members are used to make operations on data members of class.
Object:
Objects are the basic run-time entities in an object-oriented
system. They may represent a person, a place, a bank account, a table of data
or any item the program has to handle. They may be represents user-defined data
such as vectors, time and lists.
To make use of the data members and method members of class one
has to create and instance / variable of a class. The class instance / variable
is called as an object of that class. The object of a class contains all the
properties and methods of a class. It is also termed as blue print of a class.
The general syntax of creating object is
class_name
variable_name;
Example of creating class and object:
#include<iostream.h>
#include<conio.h>
class
student
{
private:
int rollno; // Data Member
char sname[20]; // Data Member
public:
void getdata() // Method Member
{
cout<<"Enter roll Number ";
cin>>rollno;
cout<<"Enter name of Student ";
cin>>sname;
}
void putdata() // Method Member
{
cout<<" The Roll Number is "<<rollno;
cout<<" \n The Name is "<<sname;
}
};
void
main()
{
student obj; // Creating an object of class
clrscr();
obj.getdata(); // accessing members of class using object
obj.putdata(); // accessing members of class using object
getch();
}
The
operator dot ( . ) is used to access class members using object of the class.
