Unit 1: Concept of Object Oriented
Programming (12)
1.1
Programming Languages and Software Crisis
1.2
Procedure Vs Object Oriented Programming
Language
1.3
Feature of Object Oriented Programming
1.4
Popular Object Oriented Programming Language and
features
1.5
Advantage and Disadvantage of OOPs
1.6 Introduction of C++ and Compilers
1.7 Programming Structure in C++
1.8 Comparison on C and C++
1.9 Additional Data types, token in C++
1.10 Insertion and Extraction
Operators
Practical Works:
· Install
the compiler of C++.
· Use
Insertion and Extraction Operator.
· Compare
the C and C++ Compiler and structure
1.1
Programming language and Software Crisis
Developments in software technology continue
to be dynamic. New tools and techniques are announced in quick succession. This
has forced the software engineers and industry to continuously look for new
approaches to software design and development, and they are becoming more and
more critical in view of the increasing complexity of software systems as well
as the highly competitive nature of the industry. These rapid advances appear
to have created a situation of crisis within the industry.
The following issued need to be addressed to
face the crisis:
• How to represent real-life entities of problems in system design?
• How to design system with open interfaces?
• How to ensure reusability and extensibility of modules?
• How to develop modules that are tolerant of any changes in future?
• How to improve software productivity and decrease software cost?
• How to improve the quality of software?
• How to manage time schedules?
1.2 Procedure Vs Object Oriented Programming
Language
Both OOP (Object Oriented Programming) and POP (Procedural
Oriented Programming) are languages (high-level) in the world of programming-
widely used in application development. These languages have a different
approach based on the nature of code development- and thus, they work
differently. Before we understand the difference between procedural and object
oriented programming, let us know more about them.
What is Procedural Programming?
You can define Procedural Programming as a programming
model derived from structural programming. It follows the concept of the
calling procedure. The procedures, also called functions, routines, or
subroutines, consist of a series of computational steps that they need to carry
out. During the execution of a program, one can call any given procedure at any
point- either by other procedures or by itself.
Procedural Programming Languages – BASIC, FORTRAN, COBOL, ALGOL, Pascal, and C.
What is Object Oriented Programming?
You can define Object Oriented Programming as a programming
model that follows the concept of objects. The objects contain codes in the
form of methods and data in the form of attributes. In the case of Object
Oriented Programming, it designs computer programs by using the concept of the
objects interacting with the real world. There are various Object Oriented
Programming languages. But the most popular ones among all are class-based. It
means that the objects are instances of the classes determining their types.
Object Oriented Programming Languages – Java, Python, C#, C++, JavaScript, PHP, Ruby, Dart, Perl, Swift,
Scala, Objective.
Difference Between Procedural and Object Oriented
Programming
Parameter
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Procedural Programming
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Object Oriented Programming
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Definition |
This programming language makes use of a
step by step approach for breaking down a task into a collection of routines
(or subroutines) and variables by following a sequence of instructions. |
This programming language uses objects
and classes for creating models based on the real-world environment. |
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Security |
Procedural Programming does not offer any
method of hiding data. |
Hiding data is possible with Object
Oriented Programming due to the abstraction. |
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Approach |
The Procedural Programming follows a
Top-Down approach. |
The Object Oriented Programming follows a
Bottom-Up approach. |
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Type of Division |
It divides any large program into small
units called functions. |
It divides the entire program into small
units called objects. |
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Inheritance |
It does not provide any inheritance. |
It achieves inheritance in three modes-
protected, private, and public. |
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Overloading |
The case of overloading isn’t possible in
the case of Procedural Programming. |
Overloading is possible in the form of
operator overloading and function overloading in the case of Object Oriented
Programming. |
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Examples |
Some common examples of Procedural
Programming are C, Fortran, VB, and Pascal. |
The examples of Object Oriented
Programming languages are Java, C++, VB.NET, Python, and C#.NET. |
1.3 Features of Object Oriented Programming
Features of Object-oriented Programming
Object
Oriented
Programming
- Objects
- Classes
- Data
abstraction
- Data
encapsulation
- Inheritance
- Polymorphism
- Dynamic
binding
- Message
communication
1.
Objects
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; they may also represent user-defined
data such as vector, time and lists.
Each object contains
data(attributes) and code to manipulate the data (methods).
Object Oriented Programming
2.
Classes
A class represents a set of
related objects. The object having similar attributes can be grouped as a
class. The class of an object defines what attributes an object has. The
entire set of data and code of an object can be made a user-defined data
type with the help of a class.
The data and the
operation of a class can be declared as one of the three types:
- Public,
- Protected
and
- Private:
3.
Data Abstraction
Abstraction refers
to the act of representing essential features without including the background
details or explanations. Since the classes use the concept of data abstraction,
hence called as Abstract Data Types (ADT).
4.
Data
Encapsulation
The wrapping up of
data and functions into a single unit (as a class) is known as encapsulation.
These methods provide the interface between the object’s data and the program.
This insulation of the data from direct access by the program is called data hiding.
5.
Inheritance
Inheritance is the
process by which objects of one class acquire the properties of objects of
another class. In OOP, the basic idea behind the inheritance is re-usability.
Using inheritance, we can add additional features to an existing class without
modifying it by deriving a new class from the existing one. The new class will
have the combined features of both the classes. Each subclass defines only
those features that are unique to it.
6.
Polymorphism
Polymorphism means
the ability to take more than one form. An operation may exhibit different
behavior in different instances. The behavior depends upon the types of the
data used in the operation.
The process of
making an operator to exhibit different behavior at different instance is called
operator overloading.
Another example of polymorphism is function
overloading, where a single function can perform various
different types of task.
7. Dynamic Binding
Binding refers to
the linking of a procedure call to the code to be executed in response to the
call. Dynamic binding
means that the code associated with a given procedure call is not known until
the time of call at run-time. It is also called late binding. This is associated with
polymorphism and inheritance. A function call associated with a polymorphic
reference depends on the dynamic type of that reference.
8.
Message
Communication
Message
communication is another feature of object-oriented programming which enables
the set of objects to communicate with each other. The concept of message communication
makes it easier to talk about building systems that directly model or simulate
their real-world counter-parts.
1.6 Benefits
of OOP
OOP offers several benefits to both the
program designer and the user. The principal advantages are:
• Through inheritance, we can eliminate redundant code extend the use
of existing
Classes.
• The principle of data hiding helps the programmer to build secure
program that can not be invaded by code in other parts of a programs.
• It is possible to have multiple instances of an object to co-exist
without any interference.
• It is possible to map object in the problem domain to those in the
program.
• It is easy to partition the work in a project based on objects.
• Software complexity can be easily managed.
1.7 Program
Structure of C++
A typical C++ program would contain four
sections. This section may be placed in separate code files and then compiled
independently or jointly.
It is a common practice to organize a
program into three separate files. The class declarations are placed in a
header file and the definitions of member functions go into another file. This
approach enables the programmer to separate the abstract specification of the
interface from the implementation details (member function definition).
Finally, the main program that uses
the class is places in a third file which “includes: the previous two files as
well as any other file required.
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Include Files |
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Class declaration
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Member functions definitions
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Main function program |
1.8
Comparision on c and c++
Below is the table of differences between C and C++:
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C |
C++ |
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C was developed by Dennis Ritchie between
the year 1969 and 1973 at AT&T Bell Labs. |
C++ was developed by Bjarne Stroustrup in
1979. |
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C does no support polymorphism,
encapsulation, and inheritance which means that C does not support object
oriented programming. |
C++ supports polymorphism, encapsulation,
and inheritance
because it is an object oriented programming language. |
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C is a subset of C++. |
C++ is a superset of C. |
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C contains 32 keywords. |
C++ contains 63 keywords. |
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For the development of code, C supports procedural
programming. |
C++ is known as hybrid language because
C++ supports both procedural
and object
oriented programming paradigms. |
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C is a function-driven language. |
C++ is an object-driven language |
1.9
Introduction of C++
1. C++ is an object-oriented programming language.
2. It was developed by Bjarne
Stroustrup at AT&T Bell Laboratories in Murray Hill, New Jersey, USA, in
the early 1980’s.
3. Therefore, C++ is an extension of C with a major addition of the
class construct feature of Simula67.
4. The idea of C++ comes from the C increment operator ++, thereby
suggesting that C++ is an augmented version of C.
5. C+ + is a superset of C.
Almost all c programs are also C++ programs. However, there are a few minor
differences that will prevent a c program to run under C++ complier.
1.10
Insertion & Extraction In C++
The insertion
operator << is the one we usually use for output, as in:
Cout<<
“this is output” <<endl;
It gets its name
from the idea of inserting data into the output stream.
The extraction
operator >> is the one we usually use for input, as in:
Cin>> X;
It gets its name
from the idea of extracting data from the input stream.
1.9.1 Application 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 applications systems.
• Since C++ allow 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 closed 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.
• It is expected that C++ will replace C as a general-purpose language
in the near future.
1.10 Simple C++ Program
Let us begin
with a simple example of a C++ program that prints a string on the screen.
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Printing A String #include<iostream> Using
namespace std; int main() { cout<<”c++ is better than
c \n”; return 0; } |
Program 1.10.1
This simple program demonstrates several C++ features.
1.10.1 Program feature
Like C, the C++ program is a collection of
function. The above example contain only one function main(). As
usual execution begins at main(). Every C++ program must have a main().
C++ is a free form language. With a few exception, the compiler ignore carriage
return and white spaces. Like C, the C++ statements terminate with semicolons.
1.10.2 Comments
C++ introduces a new comment symbol //
(double slash). Comment start with a double slash symbol and terminate at the
end of the line. A comment may start anywhere in the line, and whatever follows
till the end of the line is ignored. Note that there is no closing symbol.
The double slash comment is basically a single
line comment. Multiline comments can be written as follows:
//
This is an example of
//
C++ program to illustrate
//
some of its features
The C comment
symbols /*,*/ are still valid and are more suitable for multiline comments. The
following comment is allowed:
/* This is an example
of C++ program to illustrate
some of its features
*/
1.10.3 Output operator
The only statement in program 1.10.1
is an output statement. The statement
Cout<<”C++
is better than C.”;
Causes the string in quotation marks to be
displayed on the screen. This statement introduces two new C++ features, cout
and <<. The identifier cout(pronounced as C out) is a predefined object
that represents the standard output stream in C++. Here, the standard output
stream represents the screen. It is also possible to redirect the output to
other output devices. The operator << is called the insertion or put to
operator.
1.10.4 The iostream File
We have used the following #include
directive in the program:
#include <iostream>
The #include directive instructs the
compiler to include the contents of the file enclosed within angular brackets
into the source file. The header file iostream.h should be included at
the beginning of all programs that use input/output statements.
1.10.5 Namespace
Namespace is a new concept introduced by the
ANSI C++ standards committee. This defines a scope for the identifiers that are
used in a program. For using the identifier defined in the namespace scope we must include the using directive, like
Using
namespace std;
Here, std is the namespace where ANSI
C++ standard class libraries are defined. All ANSI C++ programs must include
this directive. This will bring all the identifiers defined in std to the
current global scope. Using and namespace are the new keyword of C++.
1.10.6 Return Type of main()
In C++, main () returns an integer value to
the operating system. Therefore, every main () in C++ should end with a return
(0) statement; otherwise a warning an error might occur. Since main () returns
an integer type for main () is explicitly specified as int.
Note that the default return type for all function in C++ is int.
The following main without type and return will run with a warning:
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main () { ………….. …………. } |
1.11 More C++
Statements
Let us consider a slightly more complex C++
program. Assume that we should like to read two numbers from the keyboard and
display their average on the screen. C++ statements to accomplish this is shown
in program 1.11.1
AVERAGE OF TWO NUMBERS
#include<iostream.h> // include header file
Using namespace std;
Int main()
{
Float number1, number2,sum,
average;
Cin >> number1; // Read Numbers
Cin >> number2; // from keyboard
Sum = number1 + number2;
Average = sum/2;
Cout << ”Sum = “
<< sum << “\n”;
Cout << “Average = “
<< average << “\n”;
Return 0;
} //end
of example
The output would be:
Enter two numbers: 6.5 7.5
Sum = 14
Average = 7
Program
1.11.1
1.11.1 Variables
The program uses
four variables number1, number2, sum and average. They are declared as type
float by the statement.
float
number1, number2, sum, average;
All variable must be declared before
they are used in the program.
1.11.2 Input Operator
The statement
cin >> number1;
Is an input statement and causes the
program to wait for the user to type in a number. The number keyed in is placed
in the variable number1. The identifier cin (pronounced ‘C in’) is a predefined
object in C++ that corresponds to the standard input stream. Here, this stream
represents the keyboard.
The operator >> is known as extraction
or get from operator. It extracts (or takes) the value from the keyboard and
assigns it to the variable on its right fig 1.8. This corresponds to a familiar
scanf() operation. Like <<, the operator >> can also be overloaded.
Object Execution
operator Variable
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Keyboard |
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Fig |
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Cin |
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>> |
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45.5 |
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1.8 Input using
extraction operator
1.11.3 Cascading of I/O
Operators
We have used the
insertion operator << repeatedly in the last two statements for printing
results.
The statement
Cout
<< “Sum = “ << sum << “\n”;
First sends the string “Sum = “ to
cout and then sends the value of sum. Finally, it sends the newline character
so that the next output will be in the new line. The multiple use of <<
in one statement is called cascading. When cascading an output operator, we
should ensure necessary blank spaces between different items. Using the
cascading technique, the last two statements can be combined as follows:
Cout
<< “Sum = “ << sum << “\n”
<< “Average = “ << average
<< “\n”;
This is one
statement but provides two line of output. If you want only one line of output,
the statement will be:
Cout
<< “Sum = “ << sum << “,”
<< “Average = “ << average
<< “\n”;
The output will be:
Sum = 14, average = 7
We can also cascade input iperator
>> as shown below:
Cin >> number1 >>
number2;
The values are
assigned from left to right. That is, if we key in two values, say, 10 and 20,
then 10 will be assigned to munber1 and 20 to number2.
1.12 An
Example with Class
• One of the
major features of C++ is classes. They provide a method of binding together
data and functions which operate on them. Like structures in C, classes are
user-defined data types.
Program 1.12.1 shows the use of class
in a C++ program.
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USE OF CLASS #include<iostream.h>
// include header file using
namespace std; class person {
char
name[30]; Int
age; public:
void getdata(void); void display(void); };
void
person :: getdata(void) {
cout << “Enter name: “; cin >> name; cout
<< “Enter age: “; cin >> age; |
}
Void person : : display(void)
{
cout << “\nNameame: “
<< name;
cout << “\nAge: “ <<
age;
}
Int main()
{ person
p;
p.getdata();
p.display();
Return 0;
} //end
of example
PROGRAM 1.12.1
The output of program is:
Enter Name: Ravinder
Enter age:30
Name:Ravinder
Age: 30
The program define person
as a new data of type class. The class person includes two basic data type
items and two function to operate on that data. These functions are called member function. The main program uses person to declare variables of
its type. As pointed out earlier, class variables are known as objects. Here, p
is an object of type person. Class object are used to
invoke the function defined in that class.
1.13
Structure of C++ Program
As it can be seen from program 1.12.1, a
typical C++ program would contain four sections as shown in fig. 1.9. This
section may be placed in separate code files and then compiled independently or
jointly.
It is a common practice to organize a
program into three separate files. The class declarations are placed in a
header file and the definitions of member functions go into another file. This
approach enables the programmer to separate the abstract specification of the
interface from the implementation details (member function definition).
Finally, the main program that uses
the class is places in a third file which “includes: the previous two files as
well as any other file required.
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Include Files |
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Class declaration
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Member functions
definitions |
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Main function program |
Fig 1.9
Structure of a C++ program
This
approach is based on the concept of client-server model as shown in fig. 1.10.
The class definition including the member functions constitute the server that
provides services to the main program known as client. The client uses the
server through the public interface of the class.
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Fig. 1.10 |
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The client-server model |
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Server |
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Class
Definition |
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Member Function |
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Client |
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Main function Program |
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1.14 Creating
the Source File
Like C programs can be created using
any text editor. Foe example, on the UNIX, we can use vi or ed text editor for
creating using any text editor for creating and editing the source code. On the
DOS system, we can use endlin or any other editor available or a word processor
system under non-document mode.
Some systems such as Turboc C++ provide an
integrated environment for developing and editing programs
The file name should have a proper file
extension to indicate that it is a C++ implementations use extensions such as
.c,.C, .cc, .cpp and .cxx. Turboc C++ and Borland C++ use .c for C programs and
.cpp(C plus plus) for C++ programs. Zortech C++ system use .cxx while UNIX
AT&T version uses .C (capital C) and .cc. The operating system manuals
should be consulted to determine the proper file name extension to be used.
1.15
Compiling and Linking
The process of
compiling and linking again depends upon the operating system. A few popular
systems are discussed in this section.
Unix AT&T C++
This process of implementation of a C++
program under UNIX is similar to that of a C program. We should use the “cc”
(uppercase) command to compile the program. Remember, we use lowercase “cc” for
compiling C programs. The command
CC example.C
At the UNIX prompt would compile the
C++ program source code contained in the file example.C. The compiler would
produce an object file example.o and then automatically
link with the library functions to produce an executable file. The default
executable filename is a. out.
A program spread over multiple files
can be compiled as follows:
CC file1.C file2.o
The statement compiles only the file file1.C and links it with the
previously compiled file2.o file. This is useful
when only one of the files needs to be modified. The files that are not
modified need not be compiled again.
Turbo C++ and Borland C++
Turbo C++ and Borland C++ provide an
integrated program development environment under MS DOS. They provide a
built-in editor and a menu bar includes options such as File, Edit, Compile and
Run.
We can create and save the source files
under the File
option, and edit them under the Edit option. We can then compile the program under the compile option
and execute it under the Run option. The Run option can be used without compiling the source code.
Summary
• Software technology has evolved through a series of phases during
the last five decades.
• POP follows top-down approach where problem is viewed as sequence of
task to be performed and functions are written for implementing these tasks.
• POP has two major drawbacks:
• Data can move freely around the program.
• It does not model very well the real-world problems.
• OOP was inventing to overcome the drawbacks of POP. It follows down
-up approach.
• In OOP, problem is considered as a collection of objects and objects
are instance of classes.
• Data abstraction refers to putting together essential features
without including background details.
• Inheritance is the process by which objects of one class acquire
properties of objects of another class.
• Polymorphism means one name, multiple forms. It allows us to have
more than one function with the same name in a program.
• Dynamic binding means that the code associated with a given
procedure is not known until the time of the run time.
• Message passing involves specifying the name of the object, the name
of the function and the information to be sent.
• C++ is a superset of C language.
• C++ ads a number of features such as objects, inheritance, function
overloading and operator overloading to C.
• C++ supports interactive input and output features and introduces
anew comment symbol // that can be used for single line comment.
• Like C programs, execution of all C++ program begins at main()
function.
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