OOPS (object oriented programming) unit 1

306
Object Oriented
Programming & Data
Structure

Concepts of OOP
Conc
epts
Object
Message Passing
Polymorphism
Abstraction
Dynamic Binding
Encapsulation
Inheritance
Class

Object:
 Any Entity that has state and behaviour is known as entity.
 Object is an active entity.(actual work)
 Object is a instance of class.
 When class is defined no memory is allocated but when it is instantiated
memory is allocated.

 Class class_name()
 {
Dataype datamember;
Datatype datafunction(){
//which task we perofrm
}
};
Int main (){
Object Obj;
Obj.function name();
Return 0;
}

Class:
 Class is a collection of objects.
 Class is a passive entity.
 A class is a user defined data type which has data member and data
function.

Inheritance:
 When one class access the property of another class is called inheritance.

Polymorphism:
 When one task is performed by different ways are known as polymorphism.
 For example, A person at the same time can have different character like
a father , a husband and employee.
 So the same person can have different behaviour in different situations.
Polymorphism
Compile Time Run Time
Function
Overloading
Operator
Overloading
Virtual Function

Abstraction:
 Hiding internal details and showing functionality.
 For example, phone call we don’t know the internal processing.
 In c++ we can use abstract class and interface to achieve abstraction.

Encapsulation:
 Binding or wrapping code and data together into a single unit is known as
encapsulation.
 For example, Capsule, It is wrapped with different medicine.

Dynamic Binding:
 In dynamic binding, the code to be executed in response to function call is
decided at runtime.
 C++ has virtual function to support this.

Message Passing:
 Objects communicate with one another by sending and receiving
information to each other through message passing.
Object A Object B
Message
Sending Object Receiving Object

1.1 Difference Between Procedural
Programming & OOPS
Procedural Languages Object Oriented Language
The Program is divided into small parts
called functions.
The Program is divided into small parts
called objects.
It follows a top-down approach. It follows a bottom-up approach.
No access specifier in procedural
programming.
Object-oriented programming has
access specifier like
private,public,protected.
There is no concept of data hiding
and inheritance.
It provides concept of data hiding
and inheritance.
Doesn’t have any proper way to
hiding data so it is less secure.
Provides data hiding so it is more
secure.
Overloading is not possible. Overloading is possible.
The function is more important than
the data.
Data is more important than the
function.
It is not based on the real word
example.
It is based on the real word example.

1.2 Various Library(header) Files For C++
 The Standard Function Library (I/O,String and character
handling,Mathematical,ide-character etc)
 The Object Oriented Class Library
• The Standard C++ I/O classes
• The String Class
• The Numeric Class
• The STL Container Classes
• The STL Algorithms
• The STL Function Objects
• The STL Iterator
• Exception Handling Classes ,etc.

1.3 Data Types in C++
 C++ supports following data types:
1. Built-in Data Type
2. Derived Data Type
3. User-defined Data Type

Data Types (continue…)
1)Built-in Data Type:
 It’s also known as primary data type and fundamental data type.
 Built-in data type can be used directly by user to declare variables.
• Integer
• Character
• Boolean
• Floating Point
• Double Floating Point
• Void
• Wide Character

1.Integer:
 Keyword is used for integer data type is int.
 Integer data type require 4 bytes of memory space.
 Range is from -2147483648 to 2147483647.
 Long,Short,Signed,Unsigned
Example:
int a;

2.Character:
 Character data type is used for storing character values.
 Keyword is used for character data type is char.
 Character data type require 1 bytes of memory space.
 Range is from -128 to 127.
Example:
char a;

3.Boolean:
 Boolean data type is used for storing logical values.
 Keyword is used for boolean data type is bool.
 Boolean variable can store either true or false value.
Example:
bool a;

4.Floating Point:
 Floating Point data type is used for storing single-precision floating-point
value or decimal values.
 Keyword is used for Floating-Point data type is float.
 Float variables require 4 bytes of memory location.
Example:
float a;

5.Double Floating Point:
 Double Floating Point data type is used for storing double-precision floating-
point value or decimal values.
 Keyword is used for Floating-Point data type is double.
 Double Float variables require 8 bytes of memory location.
Example:
double a;

 #include <iostream>
 using namespace std;
 double findSum(double x, double y)
 {
 return x + y;
 }
 int main()
 {
 double value1 = 10.45, value2 = 6.28;
 cout << "The sum is: " << findSum(value1, value2) << "nn";
 return 0;
 }

 int main()
 {
 double value1 , value2;
Cout<<“Enter 1 value”<<endl;
Cin>>value1;
Cout<<“Enter 2 value”;
Cin>>value2;
 cout << "The sum is: " << findSum(value1, value2) << "nn";
 return 0;
 }

6.Void:
 Void means without any value.
 Void data type represents a valueless entity.
 A void data type is used for those function which does not return a value.
Example:
void function_name()
{
…
}

7.Wide Character:
 Wide character data type is also a character data type but this data type has a
size grater than the normal 8-bit data type
 Wide character represents by wchar_t.
 It is generally 2 or 4 bytes long.
Example:
#include<iostream.h>
using namespace std;
int main(){
wchar_t wide_character = L’a’;
cout<<“The wide character is:”<<wide_character<<endl; //97
cout<<“Wide character size: “<<sizeof(wide_character); //2
}

2) Derived Data Type:
 The data types that are derived from primitive or built-in data types are
referred to as Derived Data Types.
 These can be of four type.
• Function
• Array
• Pointer
• Reference

1. Function:
 A function is a block of code or program-segment that is define to perform a
specific task.
 A function is generally defined to save the user from writing the same lines of
code again and again for the same input.
 All the line of code are put together inside a single function and this can be
called anywhere required.
 main() is a default function that is defined in every program of c++.
Syntax:
FunctionType FunctionName(parameters)

Example:
int max(int a,int b) //find maximum
{
if(a > b)
return a;
else
return b;
}
int main()
{
int x=10,y=20;
int m = max(x,y);
cout << “m is” << m;
return 0;
}

2. Array:
 An array is a collection of items stored at continuous memory locations.
 The idea of array represent many instances in one variable.
 Array length = 5
 First Index = 0
 Last Index = 4
40 63 22 97 10
0 1 2 3 4
Array
Indices

2. Array:
Syntax :
DataType ArrayName[size_of_array];
Example:
Int main()
{
int array[3];
array[0] = 13;
array[1] = 20;
array[2] = 2;
cout<<array[0]<<“ “<<array[1]<<“ “<<array[2];
return 0;
}

3. Pointers:
 Pointer are symbolic representation of addresses.
 They enable programs to simulate call-by-reference as well as to create and
manipulate dynamic data structure.
 Use * before the variable name.
Syntax:
datatype *var_name;

3. Pointers:
Example:
Int main()
{
int var = 10;
int* ptr; //declare pointer variable
ptr = &var; //data type of ptr and var must be same
// assign addess of a variable to a pointer
cout<<“Value Of ptr = “<<ptr<<“n”;
cout<<“Value Of Var = “<<var<<“n”;
cout<<“Value of *ptr = “<<*ptr<<“n”;
}

4. Reference:
 When a variable is declared as reference,it becomes an alternative name for an existing
variable.
 A variable can be declared as reference by putting ‘&’ in declaration.
Example:
int main()
{
int x =10;
int& ref = x; //ref is reference of x.
ref = 20; //value of x is now chaged to 20
cout<<“x = “<<x<<endl; //20
x=30; //calue of x is now changed to 30
cout<<“ref = “<<ref<<endl; //30
return 0;
}

3.User Defined Data Type:
 1. class:
 A class represent a group of similar objects.
 To represent classes in c++, it offers a user defined data type called class.
 Once the class is defined in it objects belonging to that class can be easily
be created.
 To define a class you describe what sort of information it can represent and
what sort of action can perform with that data .

 1. class:
Class department{
public:
int emp_no;
char name[30];
char deptname[30];
public:
void add(int emp_no,string name,string deptname);
void delete();
void display(){ cout<<emp_no<<name<<deptname };
};
Int main(){
department sales,HR,accounts;
sales.add(1,”abc”,”computer science”);
sales.display();
}

#include<string.h>
Class MyClass{
public:
int num;
char mystring[30];
};
Int main(){
MyClass obj;
obj.num=10;
obj.mystring=“Hello World…”;
cout<<obj.num<<endl;
cout<<obj.mystring;
return 0;
}

 2. Structure :
 A structure is a collection of variables of different data types referenced under
one name.
 For every datamember it will occupy different memory location.
Struct student{
int roll_no;
char name[30];
float marks;
};
Main(){
student s1,s2,s3;
}

#include<string.h>
Int main(){
struct{
string brand;
string model;
int year;
}c1,c2;
c1.brand=“BMW”;
c1.model=“X5”;
c1.year=1999;
c2.brand=“Ford”;
c2.model=“Mustang”;
c2.year=1969;
cout<<c1.brand<<c1.model<<c1.year;
cout<<c2.brand<<c2.model<<c2.year;
return 0;
}

 3.Union:
 Union is a memory location that is shared by two or more different variables,
generally of different types at different times.
 Defining a union is similar to defining a structure.
 Element uses same memory location.(anyone)
Union share{
int a; //2
char ch; //1
}
Union share c; //make variable

#include <iostream.h>
union GFG {
int Geek1;
char Geek2;
float Geek3;
};
int main()
{
union GFG G1;
G1.Geek1 = 34;
cout << "The first value at " << "the allocated memory : " << G1.Geek1 << endl;
G1.Geek2 = 34;
cout << "The next value stored "
<< "after removing the "
<< "previous value : " << G1.Geek2 << endl;
G1.Geek3 = 34.34;
cout << "The Final value value "
<< "at the same allocated "
<< "memory space : " << G1.Geek3 << endl;
return 0;
}

 4.Enumeration:
 An alternative method for naming integer constants is often more
convenient than const.
 This can be achieved by enumeration by using keyword enum.
Const int start =0;
Const int pause =1;
Const int go=2;
Or
Enum status{start=10,pause=20,go=30};

enum detail { a1
a2
a3};
detail d1= a1;
detail d2= a2;
detail d3= a3;
int main()
{
cout << "The numerical value "<< "assigned to a1: "<< d1<< endl;
return 0;
}

enum detail {
doble pi=3.14;
}
Function sum(){
sum=pi+x;
}
Int main()
{
detail d1;
cin>>10;
cout<<“The sum is: “<<sum();
return 0;
}

1.4 Concept Of String
 Strings are used for storing a text.
 A string variable contains a collection of character surrounded by double
quotes or single quotes.
Example:
string str = “Hello”;
 To use strings, must include an additional header file in the source code, the
<string> library:
#include<string>
string str = “Hello”;

1.4.1 Character Array
 C++ programming, the collection of characters is stored in the form of arrays.
 Strings are array of type char terminated with null character, that is , 0(ASCII value
of null character is 0).
To define a String:
char str[] = “C++”;
• Here, str is a string and it holds 4 character.
• C++ has 3 character ,the null character 0 is added to the end of the string
automatically.
 Alternative way to define string
 char str[4] = “C++”;
 char str[] = {‘C’,’+’,’+’,’0’};
 char str[4] = {‘C’,’+’,’+’,’0’};

1.4.1 Character Array (continue…)
 A character array is a derived data type in c++ that used to store a collection
of characters or strings.
 A char data type take 1 byte of memory, so a character array has memory of
the number of elements in the array. (1*number_of_element_in_array).
 Each character in character array has an index that shows the position of the
character in the string.
 The null character 0 is used to find the end of characters in the array and is
always stored in the index after the last character or in the last index.
0 1 2 3 4 5
H e l l o 0

1.4.1 Character Array (continue…)
 Example:
int main()
{
char str[30];
cout<<“Enter a string: “; //C++
cin>>str;
cout<<“You entered: “<<str<<endl;
cout<<“Enter another string: “; //Hello Word (terminating character)
cin>>str;
cout<<“You entered: “<<str<<endl;
return 0;
}

1.4.2 Pointer To Character Array
 An array of pointer to strings is an array of character pointers that holds the address of the first
character of a string or we can say the base address of a string.
 In an array of pointers, the manipulation of strings is comparatively easier than in case of 2d
array.We can easily change the position of strings by using pointers.
Example:
char *names[5] = {“John”,
“Ravi”,
“Hetvi”,
“Om”,
“Mansi”};
 We declared an array of pointer name as ‘names’ of size 5.
 In this case we have done initialization at the time of declaration, so we do not need to mention
the size of array of a pointer.
 We can also declared array without any size.
 It is not guaranteed that all the string literals will be stored in the contiguous memory location, but
the characters of string literal are stored in contiguous memory location.

1.4.2 Pointer To Character Array (continue…)
Example:
int main()
{
char *names[5] = {“John”,”Om”,”Ravi”,”Hetvi”,”Mansi”};
for(int i=0;i<5;i++)
{
cout<<names[i]<<endl;
}
return 0;
}
In this code, we have declared an array of char pointer holding 5 string literals,
and the first character of each string is holding the base address of the string.

1.4.3 Use Of String.h & It’s Important Function
 String.h is a header library for string.
 This library has several common functions for dealing with strings stored in
arrays of characters.
 The string.h header file to be included before using any string function.
 To define we can write,
#include<string.h>
So many functions are used.
strcpy()
strlen()
strcmp()
strcat()
strupr()
strlwr()

1.4.3 Functions Of String.h Header File
1. strcpy():
 Strcpy() is a standard library function in C/C++ and is ued to copy one string
to another.
 The stcpy() function takes two arguments :
• taget - Pointer to the destination array where the content is to be
copied.
• source – string which will be copied.
 It copies the character string pointed by the source to the memory location
pointed by the target.
 The null terminating character is also copied.
Syntax:
char *strcpy(char *dest, const char *src);

1. strcpy():
Example:
#include<string.h>
using namespace std;
int main()
{
char s[] = “Hello World”;
char *s1[];//large enough to store content of src
cout<<“copied String: “<<strcpy(s1,s);
return 0;
}

2. strlen():
 The strlen() function calculates the length of a given string.
 The strlen() function is defined in string.h header file.
 It doesn’t count null character ‘0’.
Syntax:
strlen(const char *str);
• Str – It represents the string variable whose length we have to find.

2. strlen():
Example:
#include<string.h>
int main()
{
char str[] = “Hello”;
cout<<“Length of string is = “<<strlen(str);
return 0;
}

3. strcmp():
This function takes two strings as arguments and compare these two strings.
Synatx:
strcmp(const char *str1,const char *str2);
Example:
int main(){
char s1[] = “Hello”;
char s2[] = “Hello”;
int returnvalue = strcmp(s1,s2);
if(returnvalue==0){
cout<<“Strings are equal”;
}
else{
cout<<“Strings are unequal”;
}
cout<<“n Value returned by strcmp() is: “<<returnvalue;
return 0;
}

4. strcat():
 This function will append a copy of the source string to the end of destination
string.
 The strcat() function takes two arguments:
1. dest
2. src
Syntax:
strcat(dest,src);

4. strcat():
Example:
int main()
{
char dest[30] = “Hello”;
char src[30] = “World”;
strcat(dest,src);
cout<<dest;
return 0;
}

5. strrev():
 This function is used to reverse the string.
Syntax:
char *strrev(char *str);
 Str – The given string which is needed to be reversed.

5. strrev():
Example:
int main()
{
char str[30] = “hello”;
cout<<“Entered string is: “<<str;
cout<<“After reversing string is: “<<strrev(str);
return 0;
}

1.5 Concepts Of Class & Objective
Class:
 Class in C++ is the building block that leads to object-oriented programming.
 It is a user-defined data type,which holds its own data members and member
functions,which can be accessed and used by creating an instance of that
class.
 A C++ class is like a blueprint for an object.
 For example consider the class of cars.There may be many cars with different
names and bunds but all of them will share some common properties like all
of them will have 4 wheels,speed limit,etc.
 So here, car is the class and wheels, speed limits are their properties.
 An Object is an instance of a class.When a class is defined,no memory is
allocated but when it is instantiated memory is allocated.

Class:
 A class is defined in c++ using the keyword class followed by the name of
class.
 The body of the class is defined inside the curly brackets and terminated by a
semicolon at the end.
class ClassName
{
Access specifier; //can be private,public or protected
Data members; //variables to be used
Member Functions(){} //methods to access data members
}; //class name ends with a semicolon

Declaring Objects:
 when a class is defined,only the specification for the object is
defined;no memory or storage is allocated.
Syntax:
ClassName ObjectName;
 If we want to access member function using object which we can create.
Object.datamember;
Object.memberfunction();

Class student()
{
public:
int rno;
string name;
double marks;
void display()
{
cout<<name<<rno<<marks;
}
};
Int main()
{
student s1;
s1.rno=1;
s1.name=“abc”;
s1.marks=50.67;
s1.display();
return 0;
}

OOPS (object oriented programming) unit 1

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