CS304 Final term Paper 2009

FINALTERM EXAMINATION 

Fall 2009 

                                    CS304- Object Oriented Programming (Session - 1)
Time: 120 min
Marks: 75


Question No: 1 ( Marks: 1 )
Which one of the following terms must relate to polymorphism?
Static allocation
Static typing
Dynamic binding
Dynamic allocation

Question No: 2 ( Marks: 1 )
Multiple inheritance can be of type
Public
Private
Protected
All of the given

Question No: 3 ( Marks: 1 ) When a subclass specifies an alternative definition for an attribute or method of its
superclass, it is ______the definition in the superclass.
overload
overriding
copy riding
none of given

Question No: 4 ( Marks: 1 ) Like template functions, a class template may not handle all the types successfully.
True
False

Question No: 5 ( Marks: 1 )It is sometimes useful to specify a class from which no objects will ever be created.
True
False

Question No: 6 ( Marks: 1 ) Assume a class Derv that is privately derived from class Base. An object of class Derv
located in main() can access
public members of Derv.
protected members of Derv.
private members of Derv.
protected members of Base.

Question No: 7 ( Marks: 1 )
A pointer to a base class can point to objects of a derived class.
True
False

Question No: 8 ( Marks: 1 ) A copy constructor is invoked when
a function do not returns by value.
an argument is passed by value.
a function returns by reference.
an argument is passed by reference.

Question No: 9 ( Marks: 1 ) A function call is resolved at run-time in___________
non-virtual member function.
virtual member function.
Both non-virtual member and virtual member function.
None of given

Question No: 10 ( Marks: 1 ) When the base class and the derived class have a member function with the same name, you must be more specific which function you want to call (using ___________).

scope resolution operator
dot operator
null operator
Operator overloading

Question No: 11 ( Marks: 1 )Each try block can have _____no. of catch blocks.
1
2
3
As many as necessary.

Question No: 12 ( Marks: 1 ) Two important STL associative containers are ______and _______.
set,map
sequence,mapping
setmet,multipule
sit,mat

Question No: 13 ( Marks: 1 ) The mechanism of selecting function at run time according to the nature of calling object
is called,
late binding
static binding
virtual binding
None of the given options

Question No: 14 ( Marks: 1 ) An abstract class is useful when,

We do not derive any class from it.
There are multiple paths from one derived class to another.
We do not want to instantiate its object.
You want to defer the declaration of the class.

Question No: 15 ( Marks: 1 ) Which of the following is incorrect line regarding function template?
template<class T>
template <typename U>
Class<template T>
template < class T, class U>

Question No: 16 ( Marks: 1 ) Which of the following is/are advantage[s] of generic programming?
Reusability
Writability
Maintainability
All of given

Question No: 17 ( Marks: 1 ) By default the vector data items are initialized to ____
0
0.0
1
null

Question No: 18 ( Marks: 1 ) Which one of the following functions returns the total number of elements in a vector.
length();
size();
ele();
veclen();

Question No: 19 ( Marks: 1 ) Suppose you create an uninitialized vector as follows:

vector<int> evec;
After adding the statment,
evec.push_back(21);
what will happen?

The following statement will add an element to the start (the back) of evec and will initialize it with the value 21.
The following statement will add an element to the center of evec and will reinitialize it with the value 21.
The following statement will delete an element to the end (the back) of evec and will reinitialize it with the value 21.
The following statement will add an element to the end (the back) of evec and initialize it with the value 21.

Question No: 20 ( Marks: 1 ) An STL container can not be used to,

hold objects of class employee.
store elements in a way that makes them quickly accessible.
compile c++ programs.
organize the way objects are stored in memory

Question No: 21 ( Marks: 1 ) Algorithms can only be implemented using STL containers.
True
False

Question No: 22 ( Marks: 1 )The main function of scope resolution operator (::) is,

To define an object
To define a data member
To link the definition of an identifier to its declaration
To make a class private

Question No: 23 ( Marks: 1 ) When is a constructor called?
Each time the constructor identifier is used in a program statement
During the instantiation of a new object
During the construction of a new class
At the beginning of any program execution

Question No: 24 ( Marks: 1 ) Consider the code below,
class Fred {
public:
Fred();
...
};
int main()
{
Fred a[10];
Fred* p = new Fred[10];
...
}
Select the best option,
Fred a[10]; calls the default constructor 09 times Fred* p = new Fred[10]; calls the default constructor 10 times
Produce an error
Fred a[10]; calls the default constructor 11 times Fred* p = new Fred[10]; calls the default constructor 11 times
Fred a[10]; calls the default constructor 10 times Fred* p = new Fred[10]; calls the default constructor 10 times

Question No: 25 ( Marks: 1 ) Associativity can be changed in operator overloading.
True
False

Question No: 26 ( Marks: 1 ) A normal C++ operator that acts in special ways on newly defined data types is said to be
glorified.
encapsulated.
classified.
overloaded.

Question No: 27 ( Marks: 1 ) Which operator can not be overloaded?
The relation operator ( >= )
Assignment operator ( = )
Script operator ( [] )
Conditional operator (? : )

Question No: 28 ( Marks: 1 ) Suppose obj1 and obj2 are two objects of a user defined class A. An + operator is
overloaded to add obj1 and obj2 using the function call obj1+obj2.
Identify the correct function prototype against the given call?

A operator + ( A &obj);
int + operator();
int operator (plus) ();
A operator(A &obj3);

Question No: 29 ( Marks: 1 ) Default constructor is such constructor which either has no ---------or if it has some
parameters these have -------- values
Parameter, temporary
Null, Parameter
Parameter, default
non of the given

Question No: 30 ( Marks: 1 ) Public methods of base class can --------- be accessed in its derived class
directly
inderectly
simultaniously
non of the given

Question No: 31 ( Marks: 1 )
Is Deque a Birectional Container?
Yes, deque behaves like queue (line) such that we can add elements on both sides of it.

Question No: 32 ( Marks: 1 )
What is meant by Generic Programming?
Generic programming refers to programs containing generic abstractions general code
that is same in logic for all data types like printArray function), then we instantiate that
generic program abstraction (function, class) for a particular data type, such abstractions
can work with many different types of data.

Question No: 33 ( Marks: 2 )
Sort the following data in the order in which compiler searches a function?
Complete Specialization, Generic Template, Partial Specialization, Ordinary Function.
Specializations of this function template, instantiations with specific types, can be called
just like an ordinary function:
cout << max(3, 7); // outputs 7

The compiler examines the arguments used to call max and determines that this is a call
to max(int, int). It then instantiates a version of the function where the parameterizing
type T is int, making the equivalent of the following function:
int max(int x, int y)
{
return x < y ? y : x;
}
the C++ Standard Template Library contains the function template max(x, y) which
creates functions that return either x or y, whichever is larger. max() could be defined like
this:
template <typename T>
T max(T x, T y)
{
return x < y ? y : x;
}
Question No: 34 ( Marks: 2 )
State any conflict that may rise due to multiple inheritance?
The conflict may arise is the diamond problem, which our author likes to call the
“diamond of doom”. This occurs when a class multiply inherits from two classes which
each inherit from a single base class. This leads to a diamond shaped inheritance pattern.
For example, consider the following set of classes:
classPoweredDevice
{
};
classScanner: publicPoweredDevice
{
};
classPrinter: publicPoweredDevice
{
};
classCopier: publicScanner, publicPrinter
{
};

Scanners and printers are both powered devices, so they derived from PoweredDevice.
However, a copy machine incorporates the functionality of both Scanners and Printers.
Ambiguity also cause problem.
Question No: 35 ( Marks: 3 )
Describe three properties necessary for a container to implement Generic Algorithms.
If you declare a container as holding pointers, you are responsible for managing the
memory for the objects pointed to. The container classes will not automatically free
memory for these objects when an item is erased from the container.
Container classes are expected to implement methods to do the following:
• create a new empty container (constructor),
• report the number of objects it stores (size),
• delete all the objects in the container (clear),
• insert new objects into the container,
• remove objects from it,
• provide access to the stored objects.
Question No: 36 ( Marks: 3 )
Write three important features of virtual functions.
With virtual functions, derived classes can provide new implementations of functions
from their base classes. When someone calls a virtual function of an object of the derived
class, this new implementation is called, even if the caller uses a pointer to the base class,
and doesn't even know about the particular derived class.
The virtual function is an option, and the language defaults to non virtual, which is the
fastest configuration.
The derived class can completely "override" the implementation or "augment" it (by
explicitly calling the base class implementation in addition to the new things it does).

Question No: 37 ( Marks: 3 )
Consider the code below,
#include <iostream>
#include <stdlib.h>
using namespace std;
class Shape{
public:
void Draw(){cout<<"shape"<<endl;}
};
class Line : public Shape{
public:
void Draw(){cout<<"Line"<<endl;}
};
class Circle : public Shape{
public:
void Draw(){cout<<"Circle"<<endl;}
};
int main(int argc, char *argv[])
{
Shape * ptr1 = new Shape();
Shape * ptr2 = new Line();
Shape * ptr3 = new Circle();
ptr1->Draw();
ptr2->Draw();
ptr3->Draw();
system("PAUSE");
return 0;
}
This code shows output,
Shape
Shape
Shape
Give the reason for this output
Suppose we want to show the output,
Shape
Line
Circle

How we can change the code to do that?
class shape { public:
void draw();
};
class circle : public shape { };
int main(int argc, char **argv){
circle my_circle;
my_circle.draw();
}
While this has all the usual advantages, e.g., code reuse, the real power of polymorphism
comes into play when draw is declared to be virtual or pure virtual, as follows:
class shape{ public:
virtual void draw()=0;
};
class circle : public shape { public:
void draw();
}
Here, circle has declared its own draw function, which can define behavior appropriate
for a circle. Similarly, we could define other classes derived from shape, which provide
their own versions of draw. Now, because all the classes implement the shape interface,
we can create collections of objects that can provide different behavior invoked in a consistent
manner (calling the draw member function). An example of this is shown here.
shape *shape_list[3]; // the array that will
// pointer to our shape objects
shape[0] = new shape; // three types of shapes
shape[1] = new line; // we have defined
shape[2] = new circle;
for(int i = 0; i < 3; i++){
shape_list[i].draw();
}
When we invoke the draw function for each object on the list, we do not need to know
anything about each object; C++ handles the details of invoking the correct version of
draw. This is a very powerful technique, allowing us to provide extensibility in our
designs. Now we can add new classes derived from shape to provide whatever behavior
we desire. The key here is that we have separated the interface (the prototype for shape)
from the implementation.
Question No: 38 ( Marks: 5 )
There are some errors in the code given below, you have to
1. Indicate the line no. with error/s
2. Give the reason for error/s
3. Correct the error/s.

1. #include <iostream> this will be #include <iostream.h>
2. #include <stdlib.h>
3. using namespace std;
4. template <typename T>
5. class MyClass{
6. public:
7. MyClass(){
8. cout<<"This is class1"<<endl;
9. }
10. };
11. template <typename T>
12. class MyClass<int*>{
13. public:
14. MyClass(){
15. cout<<"This is class2"<<endl;
16. }
17. };
18. int main(int argc, char *argv[])
19. {
20. MyClass<int> c1;
21. MyClass<int*> c2;
22. system("PAUSE");
23. return 0;
24. }
Question No: 39 ( Marks: 5 )
Given are two classes A and B. class B is inherited from class A. Write a code snippet(
for main function) that polymorphically call the method of class B. Also what
changes do you suggest in the given code segment that are required to call the class B
method polymorphically.
class A
{
public:
void method() { cout<<"A's method \n"; }
};
class B : public A
{
public:
void method() { cout<<"B's method\n"; }

};
Ans:
public class Test
{
public class A {}
public class B extends A {}
private void test(A a)
{
System.out.println("test(A)");
}
private void test(B b)
{
System.out.println("test(B)");
}
public static void main(String[] args)
{
Test t = new Test();
A a = t.new A();
A b = t.new B();
t.test(a);
t.test(b);
}
}
Question No: 40 ( Marks: 10 )
Create built-in STL (Standard Template Library) vector class object for strings
and add in it some words by taking input from user, then apply the sort()
algorithm to array of words stored in this vector class object.
Hint:Use push_back() to add the words in vector class object, and the [] operator
and size() to display these sorted words.
The STL is the containers, iterators and algorithms component of the proposed C++
Standard Library [ANSI95]. It represents a novel application of principles which have
their roots in styles of programming other than Object-orientation.
void listWords(istream& in, ostream& out)

{
string s;
while (!in.eof() && in >> s) {
add s to some container
}
sort the strings in the container
remove the duplicates
for (each string t in container) {
out << t;
}
}
For now, assume that a word is defined as a whitespace-separated string as delivered by
the stream extraction operator. Later on we will consider ways of refining this definition.
Given the way this problem is expressed, we can implement this program directly, if
naïvely. The STL container class vector will suffice to hold the words: applying the
algorithms sort and unique provides the required result.
void listWords(istream& in, ostream& out)
{
string s;
vector<string> v;
while (!in.eof() && in >> s)
v.push_back(s); // (1)
sort(v.begin(), v.end());
vector<string>::iterator e
= unique(v.begin(), v.end()); // (2)
for (vector<string>::iterator b = v.begin();
b != e;
b++) {
out << *b << endl;
}
}
At (1) the vector member function push_back() is used to add to the end of the vector.
This can also be done using the insert member, which takes as a parameter an iterator
identifying the position in the vector at which to place the added element:
v.insert(v.end(), s);
This allows us to add at any position in the vector. Be aware, though, that adding
anywhere other than the end implies the overhead of physically shifting all elements from
the insertion point to the end to make room for the new value. For this reason, and given
the choices made in this example, attempts to optimise this code by maintaining the

vector in sorted order are unwise. Replace vector with list and this becomes possible -
although in both cases a search over the container will be necessary to determine the
correct position of insertion.
The unique algorithm has the surprising property of not changing the length of the
container to which it is applied (it can hardly do this, as it has access not to the
underlying container, but only to the pair of iterators it is passed). Instead, it guarantees
that duplicates are removed by moving unique entries towards the beginning of the
container, returning an iterator indicating the new end of the container. This can be used
directly (as here, at (2)), conversely it can be passed to the erase member with the old end
iterator, to truncate the container.
Question No: 41 ( Marks: 10 )
Q. Write a detailed note on Exceptions in Destructors with the help of a coding
example.
Exceptions in Destructors:
An object is presumably created to do something. Some of the changes made by an object
should persist after an object dies (is destructed) and some changes should not. Take an
object implementing a SQL query. If a database field is updated via the SQL object then
that change should persist after the SQL objects dies. To do its work the SQL object
probably created a database connection and allocated a bunch of memory. When the SQL
object dies we want to close the database connection and deallocate the memory,
otherwise if a lot of SQL objects are created we will run out of database connections
and/or memory.
The logic might look like:
Sql::~Sql()
{
delete connection;
delete buffer;
}
Let's say an exception is thrown while deleting the database connection. Will the buffer
be deleted? No. Exceptions are basically non-local gotos with stack cleanup. The code for
deleting the buffer will never be executed creating a gaping resource leak.
Special care must be taken to catch exceptions which may occur during object
destruction. Special care must also be taken to fully destruct an object when it throws an
exception.
Example code for exception ……
#include<iostream.h>
#include<conio.c>
class Exception {
private:

char message[30] ;
public:
Exception() {strcpy(message,"There is not enough stock");}
char * get_message() { return message; }
};
class Item {
private:
int stock ;
int required_quantity;
public:
Item(int stk, int qty)
{
stock = stk;
required_quantity = qty;
}
int get_stock()
{
return stock;
}
int get_required_quantity()
{
return required_quantity;
}
void order()
{
if (get_stock()< get_required_quantity())
throw Exception();
else
cout<<"The required quantity of item is available in the stock";
}
~Item(){}
};
void main()
{
Item obj(10, 20);
try

{
obj.order();
}
catch(Exception & exp2)
{
getch();
cout << "Exception: " << exp2.get_message() << endl;
}
getch();