Object Oriented Programming - Unit Wise Questions

Question

1. What is object oriented programming? Explain objects, class, encapsulation, data hiding, inheritance, and polymorphism.

Answer 1

A function can be called without specifying all its arguments. But it does not work on any general function. The function declaration must provide default values for those arguments that are not specified. When the arguments are missing from function call , default value will be used for calculation.

Example:

#include <iostream>

using namespace std;

int sum(int a, int b=10, int c=20);

int main(){

cout<<sum(11)<<endl; /* In this case a value is passed as 11 and b and c values are taken from default arguments.*/

cout<<sum(11, 12)<<endl; /* In this case a value is passed as 11 and b value as 12, value of c values is taken from default arguments.*/

cout<<sum(11, 12, 13)<<endl; /* In this case all the three values are passed during function call, hence no default arguments have been used.*/

return 0;

}

int sum(int a, int b, int c){

int z;

z = a+b+c;

return z;

}

Answer 2

We can use keyword "this" to refer to this instance inside a class definition. One of the main usage of keyword this is to resolve ambiguity between the names of data member and function parameter. For example,

class Circle {

private:

double radius; // Member variable called "radius"

......

public:

void setRadius(double radius) // Function's argument also called "radius"

{

this->radius = radius;

// "this.radius" refers to this instance's member variable

// "radius" resolved to the function's argument.

}

......

}

In the above codes, there are two identifiers called radius - a data member and the function parameter. This causes naming conflict. To resolve the naming conflict, we could name the function parameter r instead of radius. However, radius is more approximate and meaningful in this context. We can use keyword this to resolve this naming conflict. "this->radius" refers to the data member; while "radius" resolves to the function parameter. "this" is actually a pointer to this object.

Answer 3

Class

Class is a user defined data type, which holds its own data members and member functions, which can be accessed and used by creating instance of that class.
The variables inside class definition are called as data members and the functions are called member functions.
Class name must start with an uppercase letter. If class name is made of more than one word, then first letter of each word must be in uppercase.
Classes contain, data members and member functions, and the access of these data members and variable depends on the access specifiers.
Class's member functions can be defined inside the class definition or outside the class definition.
Objects of class holds separate copies of data members. We can create as many objects of a class as we need.

Object

Objects are instances of class, which holds the data variables declared in class and the member functions work on these class objects.
Each object has different data variables.
Objects are initialized using special class functions called Constructors.
And whenever the object is out of its scope, another special class member function called Destructor is called, to release the memory reserved by the object.

Program:

#include <iostream>

#include<stdio.h>

#include<conio.h>

using namespace std;

class Bank

{

public:

char name[20];

char account_type[20];

int account_number;

int balance;

void initialize()

{

cout<<"\\nEnter Account Holders Name:";

cin>>name;

cout<<"\\nEnter Account type:";

cin>>account_type;

cout<<"\\nEnter account number:";

cin>>account_number;

cout<<"\\nEnter balance to deposit:";

cin>>balance;

}

void deposit()

{

int bal;

cout<<"\\nEnter the amout to deposit:";

cin>>bal;

balance=balance+bal;

cout<<"\\nAmount deposited successfuly!!\\nYour New Balance:"<<balance;

}

void withdraw()

{

int bal;

cout<<"\\nYour balance :"<<balance<<"\\nEnter amount to withdraw:";

cin>>bal;

if(bal<=balance)

{

balance=balance-bal;

cout<<"\\nRemaining Balance:"<<balance;

}

else

{

cout<<"Cannot withdraw amount!!";

}

void display()

{

cout<<"\\nName :"<<name;

cout<<"\\nAccout Type:"<<account_type;

cout<<"\\nAccount No."<<account_number;

cout<<"\\nBalance :"<<balance;

}

};

int main()

{

int i;

Bank bk;

bk.initialize();

cout<<"\\n1. Your Information\\n2. Deposit\\n3. Withdraw\\nEnter your choice:\\n";

cin>>i;

if(i==1)

{

bk.display();

}

else if(i==2)

{

bk.deposit();

}

else if(i==3)

{

bk.withdraw();

}

getch();

return 0;

}

Answer 4

# include<iostream>

using namespace std;

class Stack

{

int top;

public:

int a[5]; //Maximum size of Stack

Stack() //constructor

{

top = -1;

}

void push(int x)

{

if(top<5)

{

a[++top] = x;

cout << "Element Inserted \\n";

}

else

{

throw "Stack is full. You cannot insert the item!!!";

}

int pop()

{

if(top>=0)

{

int d = a[top--];

return d;

}

else

{

throw "Stack is empty. You cannot pop the item!!!";

}

};

int main()

{

int item;

Stack s1;

int ch=1;

cout<<"\\n1.PUSH\\n2.POP\\n3.EXIT";

cout<<"\\nEnter your choice:";

cin>>ch;

do

{

switch(ch)

{

case 1:

cout<<"\\nEnter the item to push:";

cin>>item;

try

{

s1.push(item);

}

catch(const char* e)

{

cout<<e<<endl;

}

break;

case 2:

try

{

cout<<"\\nPoped Item is:"<<s1.pop();

}

catch( const char* e)

{

cout<<e<<endl;

}

break;

case 3:

exit(0);

}

cout<<"\\nEnter your choice:";

cin>>ch;

}while(ch<4);

return 0;

}

Answer 5

Constructors are special class functions which performs initialization of every object. The Compiler calls the Constructor whenever an object is created. Constructors initialize values to object members after storage is allocated to the object.
Destructor is a special class function which destroys the class object as soon as the scope of object ends. The destructor is called automatically by the compiler when the object goes out of scope.

Importance of Constructor:

Constructors are used to initialize the objects of the class with initial values.
Constructors are invoked automatically when the objects are created.
Constructors can have default parameters.
If constructor is not declared for a class , the C++ compiler generates a default constructor.
A constructor can be used explicitly to create new objects of its class type.
The constructor is executed automatically.
Constructor function can be overloaded.

Importance of Destructor:

Destructors are invoked automatically when the objects are destroyed.
Destructors can not have any parameter and will not return any value.
Destructors are declared in a program to release memory space for future utilization.

Example

#include <iostream>

using namespace std;

class MyClass

{

private:

int m, n;

public:

MyClass( ) // constructor

{

m = 10;

n = 5;

}

~MyClass( ) //destructor

{

cout<<"Destructor called!!";

}

void display()

{

cout<<"The sum is:"<<(m+n)<<endl;

}

};

int main()

{

MyClass obj;

obj.display();

return 0;

}

Answer 6

Destructor is a special class function which destroys the object as soon as the scope of object ends. The destructor is called automatically by the compiler when the object goes out of scope. Destructors are declared in a program to release memory space for future utilization.

Program:

#include <iostream>

using namespace std;

class MyClass

{

private:

int m, n;

public:

MyClass( ) // constructor

{

m = 10;

n = 5;

}

~MyClass( ) //destructor

{

cout<<"Memory is released!!";

}

void display()

{

cout<<"The sum is:"<<(m+n)<<endl;

}

};

int main()

{

MyClass obj;

obj.display();

return 0;

}

Output

When an object is created the constructor of that class is called. The object reference is destroyed when its scope ends, which is generally after the closing curly bracket } for the code block in which it is created.

Answer 7

In C++, we can make operators to work for user defined classes. This means C++ has the ability to provide the operators with a special meaning for a user-defined data type, this ability is known as operator overloading. For example, we can overload an operator ‘+’ in a class like String so that we can concatenate two strings by just using +. Other example classes where arithmetic operators may be overloaded are Distance which has data member feet and inch, Complex Number etc.

Operator that cannot be overloaded are as follows:

Scope operator (::)
Sizeof
member selector(.)
member pointer selector(*)
ternary operator(?:)

Program

#include <iostream>

using namespace std;

class Distance

{

private:

int feet, inch;

public:

void readDistance(void)

{

cout << "Enter feet: ";

cin >>feet;

cout << "Enter inch: ";

cin >>inch;

}

void displayDistance(void)

{

cout << "Feet:" << feet << "\\t" << "Inches:" << inch << endl;

}

friend Distance operator+(Distance, Distance);

};

Distance operator+(Distance d1, Distance d2)

{

Distance temp;

temp.inch = d1.inch + d2.inch;

temp.feet = d1.feet + d2.feet + (temp.inch/12);

temp.inch = temp.inch%12;

return temp;

}

int main()

{

Distance d1,d2,d3;

cout << "Enter first distance:" << endl;

d1.readDistance();

cout << endl;

cout << "Enter second distance:" << endl;

d2.readDistance();

cout << endl;

d3=d1+d2;

cout << "The sum of two distance is:" << endl;

d3.displayDistance();

return 0;

}

Answer 8

#include <iostream>

using namespace std;

class Teacher

{

int tid;

string subject;

public:

void TeacherRead()

{

cout<<"Enter teacher's id:"<<endl;

cin>>tid;

cout<<"Enter teacher's subject:"<<endl;

cin>>subject;

}

void TeacherDisplay()

{

cout<<"Teacher's Id:"<<tid<<endl;

cout<<"Teacher's subject:"<<subject<<endl;

}

};

class Staff

{

int sid;

string position;

public:

void StaffRead()

{

cout<<"Enter staff's id:"<<endl;

cin>>sid;

cout<<"Enter staff's position:"<<endl;

cin>>position;

}

void StaffDisplay()

{

cout<<"Staff's id:"<<sid<<endl;

cout<<"Staff's position:"<<position<<endl;

}

};

class Coordinator: public Teacher, public Staff

{

string department;

public:

void CoordinatorRead()

{

cout<<"Enter department:"<<endl;

cin>>department;

}

void CoordinatorDisplay()

{

cout<<"Department:"<<department<<endl;

}

};

int main()

{

Coordinator c1, c2;

c1.TeacherRead();

c1.CoordinatorRead();

c1.TeacherDisplay();

c1.CoordinatorDisplay();

c2.StaffRead();

c2.CoordinatorRead();

c2. StaffDisplay();

c2.CoordinatorDisplay();

return 0;

}

Output:

Answer 9

Program:

#include <iostream>

using namespace std;

class Lecture

{

public:

int id;

string name;

void readdata()

{

cout<<"Enter the Id of lecture:";

cin>>id;

cout<<"Enter the name of leture:";

cin>>name;

}

void printdata()

{

cout<<"Id of lecture : "<<id<<endl;

cout<<"Name of lecture: "<<name<<endl;

}

};

class PartTime:public Lecture

{

public:

float payperhr;

void readdatapt()

{

cout<<"Enter the salary paid per hour: ";

cin>>payperhr;

}

void printdatapt()

{

cout<<"Salary paid per hour:"<<payperhr<<endl;

}

};

class FullTime:public Lecture

{

public:

float paypermonth;

void readdataft()

{

cout<<"Enter the salary paid per month: ";

cin>>paypermonth;

}

void printdataft()

{

cout<<"Salary paid per month:"<<paypermonth<<endl;

}

};

int main()

{

PartTime p1;

FullTime f1;

cout<<"***Part Time***"<<endl;

p1.readdata();

p1.readdatapt();

cout<<"***Displaying Data***"<<endl;

p1.printdata();

p1.printdatapt();

cout<<"***Full Time***"<<endl;

f1.readdata();

f1.readdataft();

cout<<"***Displaying Data***"<<endl;

f1.printdata();

f1.printdataft();

return 0;

}

Answer 10

When a class is derived from two or more base classes, such inheritance is called Multiple Inheritance. Multiple Inheritance in C++ allow us to combine the features of several existing classes into a single class.

Syntax:

class base_class1
{
    // body of the class
};
class base_class2
{
    //body of the class
};
class derived_classname : visibility_mode base_class1, visibility_mode base_class2
{
    //body of the class
};

Example:

#include <iostream>

using namespace std;

class A

{

protected:

int a;

public:

void get_a(int n)

{

a = n;

}

};

class B

{

protected:

int b;

public:

void get_b(int n)

{

b = n;

}

};

class C : public A, public B

{

public:

void display()

{

cout << "The value of a is : " <<a<<endl;

cout << "The value of b is : " <<b<<endl;

cout <<"Addition of a and b is : "<<a+b;

}

};

int main()

{

C obj;

obj.get_a(10);

obj.get_b(20);

obj.display();

return 0;

}

Answer 11

A friend function is a function that can access private members of a class even though it is not a member of that class.

A class can also be declared as friend of some other class. When a class ABC declares another class XYZ as its friend, then friend class XYZ can access to all data and function members of class ABC.

The philosophy of object oriented programming is that we can't access private members of a class from outside the class. But in C++, we can access private members of a class even from non-member function using concept of friend function and friend class. So, it is against the philosophy of Object Oriented Programming.

Answer 12

A friend function is a function that can access private members of a class even though it is not a member of that class.

Program:

#include <iostream>

using namespace std;

class XYZ;

class ABC

{

private:

int value;

public:

ABC()

{

value = 6;

}

friend int multiply(ABC, XYZ);

};

class XYZ

{

private:

int value;

public:

XYZ()

{

value = 4;

}

friend int multiply(ABC, XYZ);

};

int multiply( ABC v1, XYZ v2 )

{

return (v1.value * v2.value);

}

int main()

{

ABC a;

XYZ x;

cout << "Product of two number is : " << multiply( a, x ) << endl;

return 0;

}

Answer 13

Templates is defined as a blueprint or formula for creating a generic class or a function. To simply put, we can create a single function or single class to work with different data types using templates.

Function Template

It is used to define a function to handle arguments of different types in different times. Using function template, we can use same function for arguments of one data type in some cases and arguments of other types in other cases.

Syntax:

template<class type>

ret_type func_name(parameter list)

{

//body of the function

}

Example:

#include<iostream.h>
using namespace std;
template<class X>
X func( X a, X b)
{
 return a;
}
int main()
count<<func(15,8);      //func(int,int);
count,,func('p','q');   //func(char,char);
count<<func(7.5,9.2);   //func(double,double)
return();
}

Class Template

Class Templates Like function templates, class templates are useful when a class defines something that is independent of the data type.

Syntax:

template<class Ttype>

class class_name

{

//class body;

}

Example:

#include <iostream>
using namespace std;

template <class T>
class Calculator
{
private:
	T num1, num2;
	
public:
	Calculator(T n1, T n2)
	{
		num1 = n1;
		num2 = n2;
	}
	void displayResult()
	{
		cout << "Numbers are: " << num1 << " and " << num2 << "." << endl;
		cout << "Addition is: " << add() << endl;
		cout << "Subtraction is: " << subtract() << endl;
		cout << "Product is: " << multiply() << endl;
		cout << "Division is: " << divide() << endl;
	}
	T add() { return num1 + num2; }
	T subtract() { return num1 - num2; }
	T multiply() { return num1 * num2; }
	T divide() { return num1 / num2; }
};

int main()
{
	Calculator<int> intCalc(2, 1);
	Calculator<float> floatCalc(2.4, 1.2);
	
	cout << "Int results:" << endl;
	intCalc.displayResult();
	
	cout << endl << "Float results:" << endl;
	floatCalc.displayResult();
	
	return 0;
}

Answer 14

The catch block defines the action to be taken, when an exception occur. We can use the catch statement with three dots as parameter (...) so that it can catch any types of exceptions. For example:

#include <iostream>
using namespace std;

void func(int a) {
   try {
      if(a==0) throw 23.33;
      if(a==1) throw 's';
   } catch(...) {
      cout << "Caught Exception!\\n";
   }
}
int main() {
   func(0);
   func(1);
   return 0;
}

Multiple Catch Statements

Multiple catch statements are used when we have to catch a specific type of exception out of many possible type of exceptions i.e. an exception of type char or int or short or long etc. For example:

 #include<iostream.h>
       #include<conio.h>
       void main()
       {
            int a=2;
              try
              {

                  if(a==1)
                      throw a;                  //throwing integer exception

                  else if(a==2)
                      throw 'A';                //throwing character exception

                  else if(a==3)
                      throw 4.5;                //throwing float exception

              }
              catch(int a)
              {
                  cout<<"\\nInteger exception caught.";
              }
              catch(char ch)
              {
                  cout<<"\\nCharacter exception caught.";
              }
              catch(double d)
              {
                  cout<<"\\nDouble exception caught.";
              }
              cout<<"\\nEnd of program.";
       }
   Output :
              Character exception caught.
              End of program.

Answer 15

#include<iostream>

using namespace std;

template <class T>

void swaps(T &a,T &b) //Function Template

{

T temp=a;

a=b;

b=temp;

}

int main()

{

int x1=5,y1=9;

float x2=3.5,y2=6.5;

cout<<"Before Swap:"<<endl;

cout<<"x1="<<x1<<"y1="<<y1<<endl;

cout<<"x2="<<x2<<"y2="<<y2<<endl;

swaps(x1,y1);

swaps(x2,y2);

cout<<"After Swap:"<<endl;

cout<<"x1="<<x1<<"y1="<<y1<<endl;

cout<<"x2="<<x2<<"y2="<<y2<<endl;

return 0;

}

Answer 16

Exceptions are run-time anomalies or abnormal conditions that a program encounters during its execution. Exception Handling in C++ is a process to handle runtime errors. We perform exception handling so the normal flow of the application can be maintained even after runtime errors. In C++, we use 3 keywords to perform exception handling: try, catch, and throw

The try statement allows us to define a block of code to be tested for errors while it is being executed.
The throw keyword throws an exception when a problem is detected, which lets us create a custom error.
The catch statement allows us to define a block of code to be executed, if an error occurs in the try block.

Syntax to handle multiple exceptions:

try

{

//protected code

} catch(exceptionName e1)

{

// catch block

} catch(exceptionName e2)

{

// catch block

} catch(exceptionName en)

{

// catch block

}

Example:

#include<iostream.h>
       #include<conio.h>
       void main()
       {
            int a=2;
              try
              {

                  if(a==1)
                      throw a;                  //throwing integer exception

                  else if(a==2)
                      throw 'A';                //throwing character exception

                  else if(a==3)
                      throw 4.5;                //throwing float exception

              }
              catch(int a)
              {
                  cout<<"\\nInteger exception caught.";
              }
              catch(char ch)
              {
                  cout<<"\\nCharacter exception caught.";
              }
              catch(double d)
              {
                  cout<<"\\nDouble exception caught.";
              }
              cout<<"\\nEnd of program.";
       }
   Output :
              Character exception caught.
              End of program.

Answer 17

#include<iostream.h>

#include<conio.h>

#include<stdio.h>

#include<string.h>

void reverseit(char *p)

{

int j;

int len=strlen(p);

j=len-1;

for(int i=0;i<len/2;i++)

{

char a=p[i];

p[i]=p[j];

p[j]=a;

j--;

}

cout<<"\\n\\nReverse Of String :";

puts(p);

}

void main()

{

char str[50];

char ch;

cout<<"\\nEnter The String : ";

gets(str);

reverseit(str);

getch();

}

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Object Oriented Programming - Unit Wise Questions

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Object Oriented Programming - Unit Wise Questions