443600107-1-Introduction-to-C-ppt (1).ppt

Object Oriented Programming
through
C++

Introduction
• C++ is an Object Oriented Programming language, developed by
Bjarne Stroustrup in early 80’s at AT & T Lab.
• It is better than C
• More appropriate for real-life and commercial applications.

Procedure Oriented Programming (POP)
• Emphasis is on algorithm
• Large programs are divided into a no of procedures or
functions.
• Mainly the data in the programs are global.
• Data move freely inside the system.
• It follows top-down approach.
Main Program
F1 F2 F3
F4
Local
data
F1
Local
data
F2
Local
data
F3
Global Data

Object Oriented Programming (OOP)
• Emphasis is on data
• Large programs are divided into a no objects.
• Data are tied with functions.
• It follows bottom-up approach.
Data
Function
Data
Function
Data
Function

Object
• An object is a collection of some properties, behavior with
some existence.
• Box object:
Properties:- length , breadth, width. ( data elements)
Behavior:- open, close. ( functions )
Existence:- length=15, breadth=10, width=5 ( data values )
open()
close()
length
breadth
width
15
10
5
Data
elements
Data
values
Functions
A Box object

Class
• Class is a collection of some properties, behavior
• BOX class:
Properties:- length , breadth, width. ( data elements)
Behavior:- open, close. ( functions )
open()
close()
length
breadth
width
Data
elements
Functions
A Box class

• Class is a logical structure or prototype where as Object
has physical existence.
• Object is an instance of a Class.
• Class is a collection of similar types of objects where the
data values may not be the same.
Definition of OOP
OOP is an approach which provides a way to make
modularized program by allocating separate memory
locations for both data and functions which acts as
prototype for creating some more object as per demand.

Insertion and Extraction operators
cout << “NITR”;
 cout is an object of class ostream.
 << is called the insertion or put-to operator.
 The value present right to << operator would be put into the
object cout which is connected to VDU to display it.
int a;
cin >> a;
 cin is an object of class istream.
 >> is called the extraction or get-from operator.
 Extract the value stored in cin object got from keyboard and
assign it to the integer variable a;

A Simple Program
#include<iostream>
using namespace std; // namespace defines a scope
for
int main(){ // global identifiers.
int a,b,sum;
cout<<“Enter the value of a and b n”;
cin>>a;
cin>>b; // cin>>a>>b;
sum=a+b;
cout<<“The addition result is: “<<sum;
return 0;
}

Executing the program in linux
environment
• Write the program in VI or VIM editor.
• Save the file with .cpp extension.
• Compile the file in the $ prompt with the command g++. e.g.
g++ add.cpp
• After the successful compilation, to see the output by ./a.out

Reference Variable
int a=5;
int b=a;
b=b+10;
cout<<a;
cout<<b;
5
a
110
5
b
220
15
b
220
int a=5;
int b=a;
b=b+10;
cout<<a
cout<<b;
5
a, b
110
15
a, b
110
5
a
110
‘b’ acts as an alias to ‘a’ and points
to the same memory location 110
&
// 5
// 15
// 15
// 15

Scope Resolution Operator
#include<iostream.h>
using namespace std;
int m=10; // global variable m.
int main(){
int m=20; // local m in outer block
{
int k=m; // local m in inner
block
int m=30;
cout<<k; // 20
cout<<m; // 30
cout<< ::m; // 10
}
cout<<m; // 20
cout<< ::m; // 10
return 0;
} // ::m directly accesses the global m

Memory Management Operators
1. new operator: It allocates memory
Syntax :
e.g. new int allocates a memory block of size 2
bytes
and returns the base address of the memory
block;
use:
For an array:
new datatype
int *p;
p=new int;
*p=5;
5
p
110
110
int *p;
p=new int[5];
*p=0;
*(p+1)=1;
*(p+2)=2;
*(p+3)=3;
*(p+4)=4;
0 1 2 3 4
p
110 112 114 116 118
110

2. delete operator: It deallocates memory
use:
For an array:
int *p;
p=new int;
*p=5;
delete p;
int *p;
p=new int[5];
delete [5]p;
or
delete []p;
or
delete p;

Advantages of new and delete operators
over malloc, calloc and free
• Don’t have to specify the sizeof operator while using
new.
• new operator will return correct address so there is no
need of type casting.
• While allocating memory dynamically we can initialize
the block.
• new and delete operators can be overloaded.
int *p=(int *)malloc(sizeof(int));
int *p=new int(5);

Passing Arguments to Function
Arguments can be passed to a function in 3 ways.

Pass by Value.

Pass by Address or Pointer.

Pass by reference.
void add(int p, int q){
cout<<(p+q); // 30
p=p+5;
q=q+5;
}
Pass by Value
int main(){
int a=10,b=20;
add(a,b);
cout<<a; //
10
cout<<b; //
20
}
10
a
110
20
b
220
10
p
100
20
q
200
15
p
100
25
q
200

void add(int *p, int *q){
cout<<(*p+*q); // 30
*p=*p+5;
*q=*q+5;
}
Pass by Address or Pointer
int main(){
int a=10,b=20;
add(&a,&b);
cout<<a; // 15
cout<<b; // 25
return 0;
}
10
a
110
20
b
220
110
p
100
220
q
200
15
a
110
25
b
220

void add(int &p, int &q){
cout<<(p+q); // 30
p=p+5;
q=q+5;
}
Pass by Reference
int main(){
int a=10,b=20;
add(a,b);
cout<<a; // 15
cout<<b; // 25
return 0;
}
q
10
a
110
20
b
220
q
25
b
220
p
15
a
110
p
10
a
110
20
b
220

Returning values from Function
Values can be returned from a function in 3 ways:

Return by Value.

Return by Address or Pointer.

Return by reference.
int max(int p, int q){
if(p > q)
return p;
else
return q;
}
Return by Value
int main(){
int a=50,b=20,c;
c=max(a,b);
cout<<c; // 50
}

int * max(int *p, int *q){
if(*p > *q)
return p;
else
return q;
}
Return by Address or Pointer
int main(){
int a=50,b=20;
int *c;
c=max(&a,&b);
cout<< *c; // 50
}
int & max(int p, int q){
if(p > q)
return p;
else
return q;
}
Return by Reference
int main(){
int a=50,b=20,c;
c=max(a,b);
cout<< c; // 50
}

Default Argument in Function
void add(int a,int b){
cout<<a+b;
}
int main(){
add(5,7); // 12
add(2); // 11
}
void add(int a,int b=9){
cout<<a+b;
}
Default argument:
• Always assigned from right to left of the arg list
•
Default value is overridden if new value is passed
int main(){
add(5,7); // 12
add(2); // error-insufficient no of arg
}

Inline Function
• If the overhead time to call a function is greater than the
execution time of the function code then the function should
be made as inline and the function calls are replaced by the
function code.
inline void disp(int a){
cout<<a;
}
int main(){
void disp(int);
// no inline keyword in the prototype
disp(5); //replaced by cout<<5;
return 0;
}

• The inline keyword precedes the function definition but not
the function declaration.
• Inline function acts as macro.
• Inline is a request but macro is a command.
• Incase the function contains more statements and can’t be
expanded inline then the compiler shows a warning message
and the function is treated as a normal c++ function.
• Inline function does not work in the following situations.
• If the function contains a loop, switch or goto statement.
• If it is a recursive function.
• If it contains static variable.

Function Overloading
void test() { ……..}
void test(int a) {……….}
void test(char b) {……….}
void test(int a,char b) {……….}
void test(char b,int a) {……….}
Function overloading is a mechanism of using the same function
name to create multiple functions performing different tasks and
those can be differentiated by the compiler at the compile
time(compile time polymorphism).
It provides static binding.
The functions are differentiated by the no of arguments, type of
arguments or the sequence of arguments.
test(); //calls the 1st
test
test(5); //calls the 2nd
test
test(‘m’); //calls the 3rd
test
test(5,’m’); //calls the 4th
test
test(‘m’,5); //calls the 5th
test

The argument (10) which is of int type is
implicitly converted to long and so calls the
3rd test
void test(char a) { ……..}
void test(long b) {……….}
test(‘A’); //calls the 1st
test
test(25L); //calls the 2nd
test
test(10); //calls the 3rd
test
The compiler chooses a particular overloaded from the set as follows.

Search for exact match.

Follow integral promotion ( int to char, char to int, float to
double, double to float )

Follow implicit type conversion.

void test(double a) { ……..}
void test(long double b) {……….}
test(5.5f);
/* Shows an error message
because float can be converted to
both double and long double */
void test() { ……..}
int test() {……….}
No function overloading

Function Overloading(Example)
28
double add(double a, double b){
return a+b;
}
void add(int m, int n, int p){
cout<<"integer:"<<m+n+p<<endl;
}
float add(float m, float n){
return m+n;}
main(){
double a;
float b;
a = add(4.5,9.6);
add(1,2,3);
b = add(4.3,4.9);
cout<<"double:"<<a<<endl;
cout<<"float:"<<b;
}

Why Does Function overloading does not
depend on the return type ???
int f( )
{
return 9;
}
void f( )
{
}
int main( )
{
f( );
}
29s
By seeing the function call it is not easy to
make out which version of the f ( ) should get
called.

OOP Features
1. Abstraction: It is a process of highlighting the important
features of a class or an object without going into much
detail.
2. Encapsulation: It is a process of putting data and functions
into a single unit.
3. Polymorphism: means “same name multiple forms”
e.g. area of a triangle.
area of a rectangle.
4. Inheritance: The process of acquiring the properties of one
class by another class is called inheritance.
Parent Child
( Thief + Intelligent ) ( Thief + Lazy )

OOP Features Cont …
5. Dynamic Binding:
Binding is a process of associating the function call with the
code to be executed.
binding
Static binding (Compile time)
Dynamic binding (Run time)
6. Message Passing: Message to an object is a request to
execute a piece of code.
e.g. ob.area(15,10,5);
where ob is an object of class BOX.

Advantages of OOP
• Inheritance facilitates reusability.
• The principle of data hiding helps the programmer to build
secure programs.
• It is easy to partition the project work based on objects.
• Object oriented systems can be easily upgraded from
small to large systems.

Assignments
1. WAP in C++ to print all the prime no.s between 1 to 1000.
2. WAP in C++ to calculate the area of a square.
3. WAP in C++ to calculate compound interest.
4. WAP in C++ to accept name, mark, rollno, of 10 students and print average
mark of the students using array of structure.
5. WAP in C++ to sort an array in ascending and descending order.
6. WAP in C++ to find the gross salary of 10 employees, given their BASIC, DA
and HRA. The default HRA for each employee is 15% of basic and those who
have basic more than 15,000 will get HRA of 25%.
7. WAP in C++ to implement swap_n_max() function to swap 2 nos, where the
arguments are passed by pointer and the function returns a pointer to the
maximum of the 2 nos.
8. WAP in C++ to implement swap_n_max() function to swap 2 nos, where the
arguments are passed by reference and the function returns a reference to
the maximum of the 2 nos.
9. Overload the area() function to calculate the area of a rectangle and a
circle.

443600107-1-Introduction-to-C-ppt (1).ppt

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