Classes and objects

Classes And
Objects
1.
2.
3.
4.
5.
6.

STRUCTURE
CLASS
CLASS DECLARATION
CLASS MEMBERS
ARRAY OF OBJECTS
PASSING OBJECTS TO FUNCTION

Compiled By: Kamal Acharya

STRUCTURE
 It is the collection of different types of data under the

common name.
Syntax:
struct StructureName
{
dataType var1;
dataType var2;
………………….;
dataType varN;
};

Example:
struct Student
{
int Roll;
char Name[20];
};


 Declaring Variables

StructureName
StructureName
 Example

Student ram;
Student s[5];


variableName;
variableName[10];

Intialization:
StructureName VariableName ={ val1,
val2,.........,valN};
Example:
Student Ram={11,”Ram”};


Processing Structure
#include<iostream.h>
#include<conio.h>
struct student
{
int roll;
char name[20];
};
void main()
{
student s1;
clrscr();


cout<<"Enter Roll
Number"<<endl;
cin>>s1.roll;
cout<<"Enter Your
Name"<<endl;
cin>>s1.name;

cout<<"Your Name is
"<<s1.name<<endl;
cout<<"Your Roll Number is
"<<s1.roll;
getch();
}

Output


Passing Structure to Function
#include<conio.h>
struct student
{
int roll;
char name[20];
};
void display(struct student s);
void main()
{
student s1={12,"Sita"};
clrscr();
display(s1);

getch();
}
void display(struct student s1)
{
cout<<"Your Name is
"<<s1.name<<endl;
cout<<"Your Roll Number is
"<<s1.roll;
}

LIMITATION OF STRUCTURES
Struct data type can’t be treated as the built in type.
Example:
struct complex
{
int real;
int img;
}c1,c2,c3;
c3= c1+c2; //Illegal



 Do not permit data hiding. Structure members can

be directly accessed by structure variables by any
function any where
Example
complex c1;
c1.real= 20;
c1.img=70;


CLASSES
 C++ incorporates all the features of structure while

avoiding the drawbacks in new user defined data
types called Class.
 Classes can hold both data and the functions
 Classes members are private by default.


Class Declaration
 Syntax:

class className
{
private:
variables declaration;
functions declaration;
public:
variables declaration;
functions declaration;
}; By: Kamal Acharya
Compiled

Creating Objects
Example
class item
{
int number;
float cost;
public:
void getdata(int a , float
b);
void putdata();
};

item x; //single object
item x[5]; // array
 At the time of definition
also we can create
objects.
class item
{
………
………..
}x,z[20];

Accessing Class Members
 Syntax:

objectName.functionName(arguments);
Example
x.getdata(100,75.5);


Defining Member Function
Member Function can be defined in two places:
1. Inside the Class
Are inline by default.
2. Outside the Class
Syntax:
returnType className::functionName(arguments)
{
function body;
}

Defining member function inside the class
class item
{
int number;
float cost;
public:
void getdata(int a,float b)
{
number=a;
cost=b;
}

void putdata()
{
cout<<number;
cout<<cost;
}

};

Defining member function outside the class
class item
{
int number;
float cost;
public:
void getdata(int a,float b);
void putdata();
};


void item::getdata(int a,
float b)
{
number=a;
cost=b;
}
void item::putdata()
{
cout<<number;
cout<<cost;
}

C++ program with class
#include<conio.h>
class item
{
int number;
float cost;
public:
void getdata(int a, float b);
void putdata()
{
cout<<"Number:"<<number<<endl;
cout<<"Cost:"<<cost<<endl;
}
};
void item::getdata(int a, float b)
{
number=a;
cost=b;
}

void main()
{
item x;
clrscr();
cout<<"Object x"<<endl;
x.getdata(10,2.9);
x.putdata();
item y;
cout<<"Object y"<<endl;
y.getdata(12,4.7);
y.putdata();
getch();
}

Making Outside Function Inline
Class item
{
……….
public:
…………..
void getdata(int a, float b);
};
inline void item :: getdata(int a, float b)
{
function body;
}

Nesting of member function
#include<conio.h>
class item
{
int n,m;
public:
void getdata(int a, int b);
int largest();
void putdata();
};
void item::getdata(int a, int b)
{
n=a;
m=b;
}
void item::putdata()
{
cout<<"The largest number is " <<largest();
}

int item::largest()
{
if(n>m)
return n;
else
return m;
}
void main()
{
item x;
clrscr();
x.getdata(20,70);
x.putdata();
getch();
}

OUTPUT


Memory Allocation for Objects
• Each objects has its own separate data items

and memory are allocated when the objects
are created.
• Member function are created and put in the
memory only once when class are defined.


Static Data Members
 It is initialized to zero when first object is created.
 Only one copy is created for entire class.
 It is visible within the class but its life time is the

entire program.
 Type and scope of each static member variable must
be defined outside the class definition.
 They are stored separately rather than as a part of
the object.


Program to show the static data members
#include<conio.h>
class item
{
static int count;
int number;
public:
void getdata(int a)
{
number=a;
count++;
}
void getcount()
{
cout<<"Count: "<<count<<endl;
}
};
int item::count; // REMEMBER THIS


void main()
{
item a,b,c;
clrscr();
cout<<"Before Reading Data" <<endl;
a.getcount();
b.getcount();
c.getcount();
a.getdata(10);
b.getdata(20);
c.getdata(30);
cout<<"After Reading Data" <<endl;
a.getcount();
b.getcount();
c.getcount();
getch();
}

Static Member Function
 It has access to only other static members(function or

variables) declared in the same class.
 To declare any function static just put the keyword static in
front of the function defination.
static returnType functionName(arguments)
{
function body;
}
 It can be called using the class name as follows:
className :: functionName(arguments);

Program to show the work of static function
#include<conio.h>
class item
{
static int count;
int code;
public:
void setcode()
{
code=++count;
}
void showcode()
{
cout<<"Object Number: "<<code<<endl;
}
static void showcount()
{
cout<<"Count: "<<count<<endl;
}
};

int item::count;
void main()
{
item t1,t2;
clrscr();
t1.setcode();
t2.setcode();
item::showcount();
item t3;
t3.setcode();
item::showcount();
t1.showcode();
t2.showcode();
t3.showcode();
getch();
}

Remember It Won’t Work

static void showcount()
{
cout<<code; //code is not static
}


Array of Objects
 We can create the array of objects as:

className variable[x];
 To access the individual element we have to take the

help of the dot operator.
variable[i].function(arguments);


Program to demonstrate the array of objects
#include<conio.h>
class employee
{
char name[30];
int age;
public:
void getdata();
void putdata();
};
void employee::getdata()
{
cout<<"Enter name:"<<endl;
cin>>name;
cout<<"Enter age:"<<endl;
cin>>age;
cout<<endl;
}
void employee::putdata()
{
cout<<"Name: "<<name<<endl;
cout<<"Age: "<<age<<endl;
}

void main()
{
employee manager[2];
int i;
clrscr();
for(i=0;i<2;i++)
{
cout<<"Details of manager"<<i+1<<endl;
manager[i].getdata();
}
cout<<endl;
for(i=0;i<2;i++)
{
cout<<endl<<"Manager"<<i+1<<endl;
manager[i].putdata();
}
getch();
}

Passing objects to function
Two Ways to pass the objects to the function:
1. Passing by value
Entire object is passed is passed to the
function.
2. Passing by reference
Only the reference to the object is passed.


Passing by value
#include<conio.h>
class test
{
int a;
public:
void getdata(int x)
{
a=x;
}
void add(test, test);
};
void test::add(test x, test y)
{
cout<<"The sum of the values is: “
<<x.a+y.a<<endl;
}


void main()
{
test t1,t2,t3;
clrscr();
t1.getdata(40);
t2.getdata(20);
t3.add(t1,t2);
getch();
}

Passing By Reference
#include<conio.h>
class test
{
int a;
public:
void getdata(int x)
{
a=x;
}
void putdata()
{
cout<<"a= "<<a<<endl;
}
void change(test &, test &);
};
void test::change(test &x, test &y)
{
int temp;
temp=x.a;
x.a=y.a;
y.a=temp;
}

void main()
{
test t1,t2,t3;
clrscr();
t1.getdata(40);
t2.getdata(20);
cout<<"Before Swapping"<<endl;
cout<<"In t1"<<endl;
t1.putdata();
t2.putdata();
t3.change(t1,t2);
cout<<"After Swapping"<<endl;
t1.putdata();
t2.putdata();
getch();
}

Classes and objects

More Related Content

What's hot

Viewers also liked

Similar to Classes and objects

More from Kamal Acharya

Recently uploaded

Classes and objects