Intro-OOP-PPT- an introduction to the su

OOP
R. G. Masand
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R.
G.
Masand,
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CONTENTS OF UNIT - I
• Introduction to procedural, modular, object-oriented and generic
programming techniques
• Limitations of procedural programming
• Need of object-oriented programming
• Object Oriented Programming features
● Objects
● Classes & Class as ADT
● Data members
● Methods
● Message passing
● Data encapsulation
● Data abstraction
● Information hiding
● Inheritance(Code Reuse)
● Polymorphism(Function overloading and operator overloading)
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FUNDAMENTALS OF OO
PROGRAMMING
• C++ Program Structure
• C++ Identifiers
• C++ Keywords
• Comments
• Primitive Built- in Types
• Variable declarations
• Local scope v/s Global Scope
• Literals
• Const keyword
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FUNDAMENTALS OF OO
PROGRAMMING(CONTINUED)
• Defining Function & Function Prototyping
• Function Declaration
• Function Calling
• Inline Function
• Pointers
• This pointer
• C++ References
• Standard INPUT & OUTPUT Streams
• Class Constructor & Destructor
• Static Keyword
• Static data members
• Static member function
• Dynamic memory Allocation & De-allocation
• New & Delete operator
• I/O manipulation
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A SURVEY OF PROGRAMMING
TECHNIQUES
• Unstructured programming
• Procedural programming
• Modular programming
• Object-oriented programming
• Generic programming
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UNSTRUCTURED PROGRAMMING
• Only one Program i.e. main Program
• All the sequences of commands or statements in one
programs called main Program
• E.g. Fortran, assembly language, old Basic
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STRUCTURED PROGRAMMING
• Also called as Procedural Programming
• For each task procedure is created
• The procedures are called from main
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MODULAR PROGRAMMING
• Procedures with some common functionality
are grouped together into separate modules
• Program is categorized into several smaller
modules
• Each module can have its own data
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OBJECT-ORIENTED PROGRAMMING
• Works on objects which is considered smallest
unit of the object oriented languages
• Focuses more on data rather than Procedures
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EXAMPLE
• Unstructured Programming:
#include
#include
void main()
{
int a,b,c;
clrscr();
cout << "Enter the first number";
cin >> a;
cout << "Enter the second number";
cin >> b;
c=a+b;
cout << "The sum is:" << c;
getch();
} 10
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EXAMPLE
• Procedural Programming:
#include
#include
int add(int,int);
void main()
{
int a,b,c;
clrscr();
cout << "Enter the first number";
cin >> a;
cout << "Enter the second number";
cin >> b;
c=add(a,b);
cout<<"The sum is:" << c;
getch();
}
int add(int x,int y)
{
int z=x+y;
return z;
}
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EXAMPLE
• Object Oriented programming
#include
#include
class Addition
{
int a,b,c;
public:
void read()
{
cin >> a;
cin >> b;
}
void add()
{
c=a+b;
}
void display()
{
cout << "The sum is:" << c;
}
};
void main()
{
Addition obj; //object creation
cout << "Enter the numbers";
obj.read();
obj.add();
obj.display();
getch();
}
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LIMITATIONS OF PROCEDURAL PROGRAMMING
• Poor real world model.
• No importance to data.
• No privacy.
• No true reuse.
• Functions and data should be treated
equally.
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PROCEDURAL V/S OBJECT ORIENTED
PROGRAMMING
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Feature Procedure oriented Programming Object oriented Programming
Divided Into
In POP Program is divided into small parts
called functions
In OOP, program is divided into parts
called objects.
Importance In POP, Importance is not given to data
but to functions as well as sequence of
actions to be done.
In OOP, Importance is given to the data
rather than procedures or functions
because it works as a real world.
Approach POP follows Top Down approach. OOP follows Bottom Up approach
Access Specifiers POP does not have any access specifier OOP has access specifiers named
Public, Private, Protected, etc.
Data Moving In POP, Data can move freely from
function to function in the system.
In OOP, objects can move and
communicate with each other through
member functions.
Expansion To add new data and function in POP is
not so easy.
OOP provides an easy way to add new
data and function
Data Access
In POP, Most function uses Global data
for sharing that can be accessed freely
from function to function in the system.
In OOP, data can not move easily from
function to function, it can be kept public
or private so we can control the access of
data.
Data Hiding
POP does not have any proper way for
hiding data so it is less secure.
OOP provides Data Hiding so provides
more security.
Overloading In POP, Overloading is not possible. In OOP, overloading is possible in the
form of Function Overloading and
Operator Overloading.
Examples Example of POP are : C, VB,
FORTRAN, Pascal.
Example of OOP are : C++, JAVA,
VB.NET, C#.NET.
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GENERIC PROGRAMMING
• It is an idea that code should be as generic as
possible
• Means writing templates
• e.g. container classes like arrays
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OBJECT ORIENTED FEATURES
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INTRODUCTION
• C++ is a statically typed, compiled, general-
purpose, case-sensitive, free-form programming
language that supports procedural, object-
oriented, and generic programming.
• C++ is regarded as a middle-level language, as it
comprises a combination of both high-level and
low-level language features
• Developed by Bjarne Stroustrup starting in 1979
at Bell Labs in Murray Hill, New Jersey
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C++ CLASS DEFINITION
• It is template, format or blueprint
• Also can be said as user defined data Type
• A class definition starts with the keyword class
followed by the class name; and the class body,
enclosed by a pair of curly braces.
• Class definition must be followed by a semicolon
• Class contains data members and member function
class Box{
public:
double length; // Length of a box
double breadth; // Breadth of a box
double height; // Height of a box
}; 19
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CLASS AS ADT
• Abstract Data Types (ADTs)
● type implementation & operations
● hidden implementation
• built-in and user-defined types are ADTs
client
Implementation
Interface
manufacturer’s
responsibility
ADT
use
client
client
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C++ OBJECTS
• A class provides the blueprints for objects
• an object is created from a class
• Object is variable of class type
• Objects are declared the same way the variables
are declared
Box Box1; // Declare Box1 of type Box
Box Box2; // Declare Box2 of type Box
Both of the objects Box1 and Box2 will have their
own
copy of data members.
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ACCESSING THE DATA MEMBERS
• The public data members of objects of a class can be
accessed using the direct member access operator (.)
#include <iostream>
using namespace std;
class Box{
public:
double length; // Length of a
box double breadth; // Breadth of a
box double height; // Height of a
box
};int main( ){
Box Box1; // Declare Box1 of type
Box Box Box2; // Declare Box2 of
type Box double volume = 0.0; //
Store the volume of a box here
// box 1 specification Box1.height = 5.0;
Box1.length = 6.0;
Box1.breadth = 7.0;
// box 2 specification
Box2.height = 10.0;
Box2.length = 12.0;
Box2.breadth = 13.0; //
volume of //box 1
volume = Box1.height *
Box1.length * Box1.breadth;
cout << "Volume of Box1 : " <<
volume <<endl; // volume of
box 2
volume = Box2.height *
Box2.length * Box2.breadth;
cout << "Volume of Box2 : " <<
volume <<endl; return 0;}
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MEMBERS OF CLASS
• A member function of a class is a function that has
its definition or its prototype within the class
• Members are accessed using dot operator(.)
class Box
{
public:
double breadth; // Breadth of a box data
member double height; // Height of a
box
double getVolume(void); // Returns box
volume
// member function
};
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MEMBERS OF CLASS(CONTINUED…)
• Member functions can be defined within the class
definition or separately using scope resolution
operator, ::
class Box{
public:
double getVolume(void){
return length * breadth * height;
}
};// class end
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MEMBERS OF CLASS(CONTINUED…)
• If you like you can define same function outside
the class using scope resolution operator, :: as
follows:
double Box::getVolume(void){
}
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DATA ENCAPSULATION
• The wrapping up of data and function into a single
unit (called class) is known as encapsulation. Data
and encapsulation is the most striking feature of a
class.
• OOP encapsulates data (attributes) and functions
(behavior) into packages called objects
• E.g. class encapsulates data members and member
functions
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DATA ABSTRACTION
• Abstraction refers to the act of representing
essential features without including the
background details or explanation
• Classes use the concept of abstraction and are
defined as a list of abstract attributes such as size,
wait, and cost, and function operate on these
attributes.
• E.g TV
● a television separates its internal implementation from
its external interface and we can play with its interfaces
like the power button, channel changer, and volume
control without having any knowledge of its internals.
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INFORMATION HIDING
• Data hiding is one of the important features of
Object Oriented Programming which allows
preventing the functions of a program to access
directly the internal representation of a class type
• The access restriction to the class members is
specified by the labeled public, private, and
protected sections within the class body
• private, and protected are called access
specifiers/modifiers.
• A class can have multiple public, protected, or
private labeled sections
• The default access for members and classes is
private 28
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INFORMATION HIDING(CONTINUED)
• class Base {
public: // public members go here
protected: // protected members go here
private: // private members go here
};
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INFORMATION HIDING(CONTINUED)
• A public member is accessible from anywhere
outside the class but within a program
• A private member variable or function cannot be
accessed, or even viewed from outside the class.
Only the class and friend functions can access
private members.
• By default all the members of a class would be
private
• A protected member variable or function is very
similar to a private member but it provided one
additional benefit that they can be accessed in
child classes which are called derived classes
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INHERITANCE
• Inheritance is the process by which objects of one
class acquired the properties of objects of another
classes.
• In OOP, the concept of inheritance provides the
idea of reusability
• add additional features to an existing class without
modifying it
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POLYMORPHISM
• Polymorphism is another important OOP concept.
Polymorphism, a Greek term, means the ability to
take more than on form
• An operation may exhibit different behavior is
different instances.
• The process of making an operator to exhibit
different behaviors in different instances is known
as operator overloading.
• Using a single function name to perform different
type of task is known as function overloading.
• E.g. abs(parameter type) instead of fabs(),labs(),abs()
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MESSAGE PASSING
• An object-oriented program consists of a set of
objects that communicate with each other. The
process of programming in an object-oriented
language, involves the following basic steps:
● Creating classes that define object and their behaviour,
● Creating objects from class definitions, and
● Establishing communication among objects.
• A Message for an object is a request for execution
of a procedure, and therefore will invoke a
function (procedure) in the receiving object that
generates the desired results.
• Message passing involves specifying the name of
object, the name of the function (message) and the
information to be sent. Example:
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FUNDAMENTALS OF OO
PROGRAMMING
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USE OF C++
• C++ is used by hundreds of thousands of
programmers in essentially every application
domain.
• C++ is being highly used to write device drivers
and other softwares that rely on direct
manipulation of hardware under real-time
constraints.
• C++ is widely used for teaching and research
because it is clean enough for successful teaching
of basic concepts.
• Anyone who has used either an Apple Macintosh
or a PC running Windows has indirectly used
C++ because the primary user interfaces of these
systems are written in C++.
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C++ PROGRAM STRUCTURE
#include <iostream>// headers
using namespace std; // use std namespace
// main() is where program execution begins.
int main()
{
cout << "Hello World"; // prints Hello
World// //
statements
return 0;
}
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C++ IDENTIFIER
• A C++ identifier is a name used to identify a
variable, function, class, module, or any other
user-defined item.
• Starts with a letter A to Z or a to z or an
underscore (_) followed by zero or more letters,
underscores, and digits (0 to 9).
• C++ does not allow punctuation characters such as
@, $, and % within identifiers
• C++ is a case-sensitive programming language
• E.g. Mohd, zara, abc, move_name, a_123
myname50, _temp, j, a23b9, retVal 37
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COMMENTS
• Program comments are explanatory statements
that you can include in the C++ code that you write
and helps anyone reading it's source code
• All programming languages allow for some form of
comments.
• C++ supports single-line and multi-line comments
• C++ comments start with /* and end with */.
• /* This is a comment */
• /*
C++ comments can also
* span multiple lines
*/
• // prints Hello World ---single line comment
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DATA TYPE PROGRAM
• #include <iostream>
• using namespace std;
• int main(){
cout << "Size of char : " << sizeof(char) << endl;
cout << "Size of int : " << sizeof(int) << endl;
cout << "Size of short int : " << sizeof(short int) << endl;
cout << "Size of long int : " << sizeof(long int) << endl;
cout << "Size of float : " << sizeof(float) << endl;
cout << "Size of double : " << sizeof(double) << endl;
cout << "Size of wchar_t : " << sizeof(wchar_t) << endl;
return 0;
}
// endl, which inserts a new-line character after
every line
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VARIABLES DEFINITION IN C++
• A variable definition means to tell the compiler where and how much to create the
storage for the variable
type variable_list;
• Example
#include <iostream>
// Variable declaration:
extern int a, b;
extern int c;
extern float f;
int main (){
// Variable definition:
int a, b, c;
float f;
// actual initialization
a = 10;
b = 20;
c = a + b;
cout << c << endl ;
f = 70.0/3.0;
cout << f << endl ;
return 0;
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VARIABLES
• In all programming languages, we need to use
various variables to store various information
• are nothing but reserved memory locations to store
values
• to store information of various data types like
character, wide character, integer, floating point,
double floating point, Boolean etc.
• Based on the data type of a variable, the operating
system allocates memory and decides what can be
stored in the reserved memory.
• Variable provides us with named storage that our
programs can manipulate.
• The name of a variable can be composed of letters,
digits, and the underscore character.
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TYPES OF VARIABLE IN C++
Type Description
bool Stores either value true or false.
char
Typically a single octet(one byte). This is an
integer type.
int
The most natural size of integer for the
machine.
float A single-precision floating point value.
double A double-precision floating point value.
void Represents the absence of type.
wchar_t A wide character type.
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LOCAL AND GLOBAL VARIABLES
• Local Variable
● Variables that are declared inside a function or block are local
variables.
● They can be used only by statements that are inside that function
or block of code.
● Local variables are not known to functions outside their own
#include <iostream>
int main ()
{
// Local variable declaration:
int a, b;
int c;
// actual initialization
a = 10;
b = 20;
c = a + b;
cout << c;
return 0;
}
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• Global Variables
● Global variables are defined outside of all the
functions, usually on top of the program
● The global variables will hold their value throughout
the life-time of your program.
● A global variable can be accessed by any function
● Global variable is available for use throughout your
entire program after its declaration
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GLOBAL VARIABLES : EXAMPLE
#include <iostream>
// Global variable declaration:
int g = 20;
int main ()
{
// Local variable declaration:
int g = 10;
cout << g;
return 0;
}
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LITERALS
• Constants refer to fixed values that the program
may not alter and they are called literals.
• Constants can be of any of the basic data types and
can be divided into Integer Numerals, Floating-
Point Numerals, Characters, Strings and Boolean
Values.
• constants are treated just like regular variables
except that their values cannot be modified after
their definition
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INTEGER LITERAL
• An integer literal can be a decimal, octal, or
hexadecimal constant.
• A prefix specifies the base or radix: 0x or 0X for
hexadecimal, 0 for octal, and nothing for decimal.
• An integer literal can also have a suffix that is a
combination of U and L, for unsigned and long,
respectively.
• The suffix can be uppercase or lowercase and can
be in any order
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EXAMPLES
212 // Legal
215u // Legal
0xFeeL // Legal
078 // Illegal: 8 is not an octal digit
032UU // Illegal: cannot repeat a suffix
85 // decimal
0213 // octal
0x4b // hexadecimal
30 // int
30u // unsigned int
30l // long
30ul // unsigned long
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FLOATING POINT LITERALS
• A floating-point literal has an integer part, a
decimal point, a fractional part, and an exponent
part
3.14159 // Legal
314159E-5L // Legal
510E // Illegal: incomplete exponent
210f // Illegal: no decimal or
exponent
.e55 // Illegal: missing integer or
fraction
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BOOLEAN LITERAL
• There are two Boolean literals and they are part of
standard C++ keywords:
● A value of true representing true.
● A value of false representing false
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CHARACTER LITERALS
• Character literals are enclosed in single quotes
• If the literal begins with L (uppercase only), it is a
wide character literal (e.g., L'x') and should be
stored in wchar_t type of variable
• it is a narrow character literal (e.g., 'x') and can be
stored in a simple variable of char type
• A character literal can be a plain character (e.g., 'x'),
an escape sequence (e.g., 't'), or a universal
character (e.g., 'u02C0').
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ESCAPE SEQUENCES
Escape sequence Meaning
character
' ' character
" " character
? ? character
a Alert or bell
b Backspace
f Form feed
n Newline
r Carriage return
t Horizontal tab
v Vertical tab
ooo
Octal number of one to three
digits
xhh . . .
Hexadecimal number of one or
more digits
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STRING LITERALS
• String literals are enclosed in double quotes
• A string contains characters that are similar to
character literals: plain characters, escape
sequences, and universal characters
• "hello, dear“
• "hello,

dear“
• "hello, " "d" "ear"
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CONST KEYWORD
• use const prefix to declare constants with a specific type as
follows:
const type variable = value;
#include <iostream>
int main()
• {
const int LENGTH = 10;
const int WIDTH = 5;
const char NEWLINE = 'n';
int area;
area = LENGTH * WIDTH;
cout << area;
cout << NEWLINE;
return 0;
}
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DEFINING A FUNCTION
return_type function_name( parameter list )
{
body of the function
}
• Return Type
• Function Name
• Parameters
• Function Body 58
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FUNCTION DECLARATIONS
• A function declaration tells the compiler about a
function name and how to call the function. The
actual body of the function can be defined
separately.
• A function declaration has the following parts:
return_type function_name( parameter list );
int max(int num1, int num2);
• Function declaration is required when you define a
function in one source file and you call that
function in another file
• should declare the function at the top of the file
calling the function.
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FUNCTION CALLING
• While creating a C++ function, we give a definition
of what the function has to do.
• To use a function, we will have to call or invoke
that function.
• When a program calls a function, program control
is transferred to the called function
• A called function performs defined task and when
its return statement is executed or when its
function-ending closing brace is reached, it returns
program control back to the main program
• Actual arguments and formal arguments
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FUNCTION CALLING
Call Type Description
Call by value
This method copies the actual value of
an argument into the formal parameter
of the function. In this case, changes
made to the parameter inside the
function have no effect on the
argument.
Call by pointer
This method copies the address of an
argument into the formal parameter.
Inside the function, the address is used
to access the actual argument used in
the call. This means that changes made
to the parameter affect the argument.
Call by reference
This method copies the reference of an
argument into the formal parameter.
Inside the function, the reference is
used to access the actual argument used
in the call. This means that changes
made to the parameter affect the
argument.
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POINTER
• A pointer is a variable whose value is the address of
another variable
type *var-name;
type is the pointer's base type
• it must be a valid C++ type and var-name is the
name of the pointer variable. The asterisk we used
to declare a pointer is the same asterisk that you
use for multiplication
int *ip; // pointer to an integer
double *dp; // pointer to a double
float *fp; // pointer to a float
char *ch; // pointer to character 62
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USING POINTERS IN C++
#include <iostream>
int main ()
{
int var = 20; // actual variable declaration.
int *ip; // pointer variable
ip = &var; // store address of var in pointer variable
cout << "Value of var variable: ";
cout << var << endl;
// print the address stored in ip pointer variable
cout << "Address stored in ip variable: ";
cout << ip << endl;
// access the value at the address available in pointer
cout << "Value of *ip variable: ";
cout << *ip << endl;
return 0;
} 63
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OUTPUT
• Value of var variable: 20
• Address stored in ip variable: 0xbfc601ac
• Value of *ip variable: 20
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C++ REFERENCES
• Think of a variable name as a label attached to the
variable's location in memory
• then think of a reference as a second label attached
to that memory location
int i = 17;
int& r = i;
Read the & in these declarations as reference
65
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PROGRAM
#include <iostream>
int main ()
{
// declare simple variables
int i;
double d;
// declare reference variables
int &r = i;
double & s = d;
i = 5;
cout << "Value of i : " << i << endl;
cout << "Value of i reference : " << r << endl;
d = 11.7;
cout << "Value of d : " << d << endl;
cout << "Value of d reference : " << s << endl;
return 0;
}
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OUTPUT
Value of i : 5
Value of i reference : 5
Value of d : 11.7
Value of d reference : 11.7
67
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C++ REFERENCES V/S POINTERS
• References are often confused with pointers but
three major differences between references and
pointers are:
● We cannot have NULL references. We must always be
able to assume that a reference is connected to a
legitimate piece of storage.
● Once a reference is initialized to an object, it cannot be
changed to refer to another object. Pointers can be
pointed to another object at any time.
● A reference must be initialized when it is created.
Pointers can be initialized at any time.
68
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THE STANDARD INPUT STREAM (CIN)
• The predefined object cin is an instance of istream
class
• The cin object is said to be attached to the standard
input device, which usually is the keyboard.
• The cin is used in conjunction with the stream
extraction operator, which is written as >> which are
two greater than signs
int main( )
{
char name[50];
cout << "Please enter your name: ";
cin >> name;
cout << "Your name is: " << name << endl;
}
69
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THE STANDARD INPUT STREAM
(CIN)(CNTD….)
• The stream extraction operator >> may be used
more than once in a single statement. To request
more than one datum you can use the following:
cin >> name >> age;
• This will be equivalent to the following two
statements:
cin >> name;
cin >> age;
70
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THE STANDARD OUTPUT STREAM (COUT)
• The predefined object cout is an instance of ostream
class
• The cout object is said to be "connected to" the
standard output device, which usually is the display
screen
• The cout is used in conjunction with the stream
insertion operator, which is written as << which are
two less than signs
#include <iostream>
int main( )
{
char str[] = "Hello C++";
cout << "Value of str is : " << str << endl;
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THE CLASS CONSTRUCTOR
• A class constructor is a special member function of
a class that is executed whenever we create new
objects of that class.
• A constructor will have exact same name as the
class and it does not have any return type at all, not
even void. Constructors can be very useful for
setting initial values for certain member variables.
• 0-argument constructor
• Parameterized constructor
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• E.g.
Class test_ctor{
private :
int x,y;
public :
test_ctor(int x=0, int y=0){
this→x = x;
this→ y=y;
}
tets_cot(){
//some code here….
}
void display(){
// some code goes here…..
}
} 73
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CONTINUED….
void main(){
test_ctor t1(10,20);
tets_ctor t2;
test_ctor t3;
t3.display();
}
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THE CLASS DESTRUCTOR
• A destructor is a special member function of a
class that is executed whenever an object of it's
class goes out of scope or whenever the delete
expression is applied to a pointer to the object of
that class.
• A destructor will have exact same name as the class
prefixed with a tilde (~) and it can neither return a
value nor can it take any parameters. Destructor
can be very useful for releasing resources before
coming out of the program like closing files,
releasing memories etc.
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• E.g.
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INLINE FUNCTION
• C++ inline function is powerful concept that is
commonly used with classes
• If a function is inline, the compiler places a copy of
the code of that function at each point where the
function is called at compile time.
• Any change to an inline function could require all
clients of the function to be recompiled because
compiler would need to replace all the code once
again otherwise it will continue with old
functionality.
• To inline a function, place the keyword inline
before the function name and define the function
before any calls are made to the function
• The compiler can ignore the inline qualifier in case
defined function is more than a line.
77
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INLINE (CNTD…)
• A function definition in a class definition is an inline
function definition, even without the use of the inline
specifier
#include <iostream>
inline int Max(int x, int y)
{
return (x > y)? x : y;
}
// Main function for the programint
main( )
{
cout << "Max (20,10): " << Max(20,10) << endl;
cout << "Max (0,200): " << Max(0,200) << endl;
cout << "Max (100,1010): " << Max(100,1010) << endl;
return 0;
}
78
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OUTPUT
Max (20,10): 20
Max (0,200): 200
Max (100,1010): 1010
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STATIC KEYWORD
• We can define class members static using static
keyword
• When we declare a member of a class as static it
means no matter how many objects of the class
are created, there is only one copy of the static
member.
• A static member is shared by all objects of the
class
• All static data is initialized to zero when the first
object is created, if no other initialization is
present
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#include <iostream>
class Box{
public:
static int objectCount;
// Constructor definition
Box(double l=2.0, double b=2.0, double h=2.0)
{
cout <<"Constructor called." << endl;
length = l;
breadth = b;
height = h;
// Increase every time object is created
objectCount++;
}
double Volume()
{
}
private:
};
// Initialize static member of class Box
int Box::objectCount = 0;
int main(void){
Box Box1(3.3, 1.2, 1.5); // Declare box1
Box Box2(8.5, 6.0, 2.0); // Declare box2
// Print total number of objects.
cout << "Total objects: " << Box::objectCount << endl;
return 0;
}
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OUTPUT
Constructor called.
Constructor called.
Total objects: 2
82
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STATIC FUNCTION MEMBERS
• By declaring a function member as static, we make
it independent of any particular object of the class
• A static member function can be called even if no
objects of the class exist and the static functions
are accessed using only the class name and the
scope resolution operator ::
• A static member function can only access static
data member, other static member functions and
any other functions from outside the class.
Program during labs.
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DYNAMIC MEMORY ALLOCATION AND DE-
ALLOCATION
• Memory in your C++ program is divided into two
parts
● The stack: All variables declared inside the function will
take up memory from the stack → Static memory
allocation
● The heap: This is unused memory of the program and
can be used to allocate the memory dynamically when
program runs.
→ Dynamic memory allocation
• Many times, we are not aware in advance how
much memory we will need to store particular
information in a defined variable and the size of
required memory can be determined at run time
84
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DYNAMIC MEMORY ALLOCATION AND DE-
ALLOCATION(CNTD….)
• In static memory allocation, decision of
memory allocation is done at compile time
e.g. int a;
● During run time variables are created
• In dynamic allocation both decision &
allocation of memory is done during
execution time.
85
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NEW AND DELETE OPERATOR
• We can allocate memory at run time within the
heap for the variable of a given type using a special
operator in C++ which returns the address of the
space allocated. This operator is called new
operator.
• Use delete operator, which de-allocates memory
previously allocated by new operator.
• Syntax :
new data-type;
data-type could be any built-in data type
86
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• E.g.
#include<iostream>
int main()
{
int n, *pointer,c;
cout<<“enter an integern”;
cin>>n;
pointer = new int[n];
cout<<“enter”<<n<<“ integersn”;
for(c=0;c<n;c++)
cin>>pointer[c];
cout<<“elements entered by you aren”;
for(c=0;c<n;c++)
cout<<poineter[c]<<endl;
delete[] pointer;
return 0;
}
87
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NEW OPERATOR
void main(){
int x, float y, int *p;
p = new int;
}
➢ Now compiler makes an entry in symbol table
➢ new allocates memory, calls constructor
➢ New creates nameless objects.
➢ what is allocated must be de-allocated so use
delete operator which calls destructor, de-allocates
memory.
88
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NAMED & NAMELESS OBJECTS....!!!
class shape{
private :
int a,b;
};
shape p; → name object created (p)
Shape *q;
q = new shape; → name less object created.
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• E.g. New and delete
operator
Class example {
private :
int i, float a;
public :
example(){
i=0;
a=0.0;
}
Example(int ii, float aa){
i = ii;
a= aa;
}
};
void main(){
example *p1,*p2;
p1 = new example;
p2 = new
example(15,30.5);
delete p1;
delete p2;
}
90
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THIS POINTER
• Also called as constant pointer
• “this” keyword is used to identify between local
and instance variables
91
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• Class this_test{
private :
int i, float a;
public :
void setdata(int i, float a){
this→i = i;
this→ a= a;
}
};
void main(){
this_test t1,t2;
t1.setdata(10,20.5);
}
92
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FORMATTING FLAGS AND MANIPULATORS
• The following output manipulators control the
format of the output stream
• Include <iomanip>
• The Range column tells how long the manipulator
will take effect: now inserts something at that point,
next affects only the next data element, and all
affects all subsequent data elements for the output
stream.
93
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REFERENCES
• Let us c++ by yashwant kaetkar
• Object oriented programming with c++ by
balagurusamy
• http://www.uow.edu.au/~lukes/TEXTBOOK/notes-
cpp/index.html
• http://www.cplusplus.com/reference/library/manipula
tors/
• http://www.cplusplus.com/doc/tutorial/
94
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