Object Oriented Progamming in C++ [OOP in CPP Q&A]

8/3/2019 Object Oriented Progamming in C++ [OOP in CPP Q&A]

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QUESTIONS AND ANSWERS

FOR

OBJECT ORIENTEDPROGRAMMING IN C++

G.Appasami, M.Sc., M.C.A., M.Phil., M.Tech.,

Assistant Professor

Department of Computer Science and Engineering

Dr. Pauls Engineering Collage

Pauls Nagar, Villupuram

Tamilnadu, India.

SARUMATHI PUBLICATIONS

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First Edition: July 2010

Second Edition: July 2011

Published BySARUMATHI PUBLICATIONS

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OBJECT ORIENTED PROGRAMMING IN C++, DEPT. OF CSE, DRPEC. 1

OBJECT ORIENTED

PROGRAMMING IN C++

QUESTIONS

WITH

SHORT ANSWERS


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1. Who developed C++?

C++ was developed at AT & T Bell laboratories in the early 1980s

by Bjarne Stroustrup. The name C++ (pronounced as C plus plus) was

coined by Rick Mascitti where ++ is the C increment operator.

2. Explain Basic Concepts of OOP2. List out the Salient features of OOP

2. Write the characteristics of OOP

2. List out the elements of OOP

The basic concepts of OOP are Class, object, Data abstraction,

Encapsulation, Inheritance, Polymorphism, Dynamic binding and message

passing.

Concept MeaningClass Class is a user defined data type

Object Object is an run time entity of class

Abstraction The act of representing essential features without

including the background details

Encapsulation The wrapping up of the data and functions into a

single unit (called class) is known as

encapsulation

Inheritance The mechanism of deriving a new class fromexisting class is called inheritance

Polymorphism The ability to take more than one form. More

operations in same name. polymorphism means

one name multiple forms

Dynamic binding The addresses of the functions are determined at

run time rather than compile time (late binding).

Linking of a procedure to execution code.

Message

Communication

Objects interaction by sending messages to each

other


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3. What are the Applications of OOP?

Real time systems Simulation and modeling Object Oriented Data bases Hypertext, hypermedia and expert text AI and Expert Systems Neural networks and expert systems Desition support and office automation systems CIM/CAD/CAM Systems

4. How does a C++ Class differ from a C++ structure?

Structure Class

Default access is public Default access is private

Data Data & functions

Default inheritance type is public Default is private inheritance

5. What is namespace?

Namespace is a collection of classes arranged in a hierarchical

order. If we include more header files, then there is a chance to have same

classes in different files. This is a problem for compiler to select a class

from which header file. This problem is solved by standard namespace.

Ex.: using namespace std;

6. Write a simple C++ program to print a string on a screen

#include

main()

{

cout


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void getdata(void); //Function declaration

void display(void);

};

void person : : getdata(void) //Function definition

{ cout>name;

cout>age;

}

void person : : display(void)

{ coutsum;

The operator


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9. Write the structure of C++ program

A typical C++ program would contain four sections as shown in the

figure.

10. What stream class is required to create an output stream?

Ostream classes is required to create an output stream.

Note: istream class for input. Iostream for input & output

11. What are the uses of void?

To specify the return type of function when it is not returning anyvalue.

To indicate an empty argument list to a function.12. What are the difference between normal variable and reference

variable?

S normal variable reference variable

1 It holds data It holds address

2 It is not a poiner It is a pointer to another variable.

3 It is a variable tostore value in

memory

It is a variable to store address ofanother variable in memory

4 Ex.: int x; Ex.: int *ptr;

13. Write C++ character set

Like the C language, C++ also comprises a character set from which

the tokens (basic types of elements essential for programming coding) are

constructed. The character set comprises of A .. Z , a .. z, 0 .. 9, +,

-, /, *,\, (, ), [, ], {, }, =, !=, , . , ; : %, ! , &, ?, _, #, =, @, white

space, horizontal tab, carriage return and other characters.

Include filesClass declaration

Class function definitions

Main function program


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14. What is a TOKEN?

A token is the smallest individual unit in a program. Tokens are

classified as shown in Figure.

15. List out few key words in C++.

16. Explain operator and operand.

Operator specifies an operation to be performed that yields a value.

An operand is an entity on which an operator acts.

For example: RESULT = NUM1 + NUM2

NUM1 and NUM2 are operands. + is the additional operator, that

performs the addition of the numbers. The result (value) generated is stored

in the variable RESULT by virtue of = (Assignment) operator. Table

shows the operators in C++.

17. List out the operators in C++

The following operators are specific to C++.

:: .* ->* ::* new delete endl setw


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18. List out the Advantages of new operator

1. New operator automatically computes the size of the dataobject. We need not use the size of operator.

2. It automatically returns the correct pointer type. So that there isno need to use a type cast.

3. It is possible to initialize the object while creating the memoryspace.

4. Like other operator, new and delete can be overloaded.19. List out the Operators classification.

Operators are classified as Arithmetic, Assignment, Component

Selection, Shift, Conditional Logical, Manipulator, Member

dereferencing, Preprocessor, Relational, Scope Resolution, Type Cast

Memory Management. etc

Based on operand requirements, operators are also classified as

Unary operators require one operand:

&, !, *, ++, --, +, -, ~.

Binary operator requires two operands:

+, -, *, /,


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22. Can the precedence order of an operator be altered?

Yes, the precedence order of an operator can be altered by using

parenthesis.

23. Give an example for type cast operation

int avg, sum, num;

avg = sum / float(num);

Now num integer variable is promoted to float

24. Explain Expression with an example.

An expression is a combination of operators, constants and

variables arranged as per the rule of the language. It may also include

function call with return call. An expression may consist of one or moreoperands and zero or more operators to produce value.

Ex. A=(B/2)+(C*10.5)

25. What is an expression?

An expression is a program construct or operation created by

combination of operators and operands.

Ex.: C = A+ B

26. Write the types of expressions

There are four types of expressions. They are:

Constant expressions consist of only constant values

Ex.: 15 25+10/2.0 M

Integral expressions are those which produce integer results

Ex.: m*n-5 m-x 5+int(2.7)

Where m and n are integer variables

Float expressions are those which produce floating-point results

Ex.: x+y x*y/10 5+float(10)

Where x and y are floating-point variables

Pointer expressionsproduce address variablesEx.: &m *ptr ptr+1

Where m is a variable and ptr is a pointer


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27. Write branching and looping statements?

Branching (Selection )

if, if-else and switch

Looping

while, do-while and for

28. What is implicit conversion?

28. What is automatic conversion?

Whenever data types are mixed in an expression, C++ performs the

conversions automatically. This process is known as implicit or automatic

conversion.

Consider an expression with mixed data types like m=5+2.75 is a

valid statement.

29. List out some basic data types in C++

Name Description Size* Range*

char Character or small integer. 1bytesigned: -128 to 127

unsigned: 0 to 255

short int

(short)Short Integer. 2bytes

signed: -32768 to 32767

unsigned: 0 to 65535

int Integer. 4bytes

signed: -2147483648 to

2147483647

unsigned: 0 to

4294967295

long int

(long)Long integer. 4bytes

signed: -2147483648 to

2147483647

unsigned: 0 to

4294967295

bool

Boolean value. It can take

one of two values: true or

false.

1byte true or false

float Floating point number. 4bytes+/- 3.4e +/- 38 (~7

digits)

doubleDouble precision floating

point number.8bytes

+/- 1.7e +/- 308 (~15

digits)

long

double

Long double precision

floating point number.8bytes

+/- 1.7e +/- 308 (~15

digits)

wchar_t Wide character.2 or4

bytes1 wide character


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30. Define widening conversion

Converting from smaller data type to wider data type is called

widening conversion.

Conversion of a char or short int to int is called integer widening

conversion.

31. Explain water fall model of type conversionConverting from smaller data type to wider data type is called

widening conversion. Widening conversion is also called as water fall

model of type conversion. The water fall model is shown in the below

figure.

33. Explain function prototyping

Function prototyping is a declaration statement in the calling

program. The general form is as follows:

Example 1: float volume(int x, float y, float z);

Example 1: float area(float, float );

Short char

int

unsigned int

long int

unsigned long int

float

double

long double

Return-type function-name (argument-list);


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33. What is call byValue?

If a function called with actual value is called call by value.

Ex. int swap (int a, int b)

34. What is call by reference? If a function called with reference variables is called call by

reference.

void swap (int &a, int &b)

{ int t =a;

a=b;

b=t;

}

swap (&x, &y);

Because it works on original data. x and y value gets change permanently.

35. What is return by reference?

A function returns a reference is known as return by reference

int & max(int &a, int &b)

{ if (a>b)

return a;

else

return b;

}

int * ptr = max(&x, &y)

this function may return address of x or y to ptr.

36. What is function overloading?Family of functions with one function name but with different

argument lists. Depending on the arguments correct function will be

invoked. This process is known as function overloading. This is also known

as function polymorphism (compile time polymorphism).EX: //declarations

add(int, int) //prototype1

add(float,float) //prototype2


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add(int, float) //prototype3

//function call

cout


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39. What is friend function?The non member function is defined elsewhere in the program like a

normal C++ function. The function definition doest use either the key word

friend or the scope operator ::. The functions that are declared with the

keyword friend are known as friend function.

Ex:

class A

{ Int a[20];

Public:

getdata();

{for (int i=0;i>a[i];}

showdata();

{for (int i=0;i


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43. What is constant argument?

If function arguments are declared as const. they the arguments are

called comstant argument. The function arguments should not modified in

some cases like interest rate.

float intamout (float p, int t, const float r=0.15)

This is important only when we pass arguments by reference or

pointer.

44. State the properties of static function?

A member function that is declared static has the following

properties:

A static function can have access to only other static members(variables and functions) declared in the same class.

A static member function can be called using the class name(instead of its objects) as follows:

Calss_name :: function_name;

45. Explain array of objects.Set of objects of same class with the same name and stored in

continuous memory locations

Array of objects are collection of objects of same class that are

referred by a common name.

Ex; class stack

{ Int top, a[20];

Public:

Push();

Pop();

}

Main()

{ Stack s[5];

---

}


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46. State the properties of static member functions

Static member functions can also be defined in the private region of

a class.

Private Static member functions can access only Static data

member and can invoke Static member functions .

47. What is abstract data type?An abstraction that describes a set of objects in terms of an

encapsulated or hidden data and operations on that data is called abstract

data type.

48. What is abstract data type?

Abstract collection of data elements and their accessing functions.

Classes use the concept of abstraction and are defined as a list of attributes

and functions to operate on these attributes. They encapsulate all the

essential properties of the objects. Since the classes use the concept of data

abstraction, they are known as abstract data types.

Ex: class stack

{

Int top, a[20];

Public:

Push();

Pop();

}

49. What are the different types of access specifiers?Class members can have the following access specifiers

Private is the default access and private members are accessible only from

the member functions of the same class and/or from their friend class.

Protected members are accessible from member function of the same class

and/or friend classes, and also from members of their immediate derived

class

Public members are accessible from anywhere the class is visible.


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50. What is data abstraction?

Data abstraction refers to the act of representing essential features

without including the background details or explanations.

51. Explain encapsulation

The wrapping up of data and functions into a single unit (called

class) is known as encapsulation.

The mechanism by which the data and functions are bound together

with in an object definition is called encapsulation.

52. What is a class? A class is a user defined data type. It is a blue print, which defines

the variable and methods common to all objects of a certain kind.

53. What is a class?

A group of objects that share common properties and relationships

is called class. In C++, A class is a new data type that contains member

variables and member functions that operate on the variables. A class is

defined with a keyword class.

54. What is an abstract class?

A class that serves only as abase class from which classes are

derived is called abstract class. No objects are created for abstract class.

A class contains a pure virtual functions is an abstract class.

55. What is a container class?

A class that contains objects of other classes is called container

class

56. What is an object?A variable whose type is a class is called an object.

An instance of a class is known as an object.

objects are Run time entities in object oriented programming


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57. What is an instance?

An instance is an object of a particular class. The term instance and

objects are interchangeable. An object has state, behavior and identity,

State defines the attribute (data member) of an object.

Behavior defines method or function used to modify the state of an

object.

Identity is name of an object.

58. What is Call by reference? A function call mechanism that passes arguments to a function by

passing the address of the arguments.

59. What is Call by value? A function call mechanism that passes arguments to a function by

passing a copy of the values of the arguments.

60. Explain constructor with exampleA constructor is a special function whose task is to initialize the

objects of its class. It is special because its name is the same as the class.

Class stack

{

int top;

Public:stack()

{top =0;}

- - -

}

61. Explain destructor with exampleDestructor is used to destroy the objects that have been created by a

constructor. Like a constructor, the destructor is a member function whose

name is same as the class name but it is preceded by tilde.

~stack(){}

62. What are the main function return types?

void and integer


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63. How constructors differ from normal functions?

A constructor is a member function of a class that is used to create

objects or initialize objects of that class. It has the same name as the class

itself, has no return type and is invoked while creating the objects.

A method is an ordinary function of a class. it has its own name, a

return type and is invoked explicitly using the dot operator.

64. List out the properties of constructors

1. Constructors should be declared in public section.

2. They are invoked automatically when objects are created

3. They do not have return type.

4. They must use name of the class.

65. What are the difference between default and parameterized

constructors?

The constructors which does not take arguments explicitly is called

default constructor.

Constructors with arguments are called parameterized constructors.

66. What are all the operators that cannot be overloaded?Direct member access operator .

De-reference pointer to class member operator .*

Scope resolution operator ::

Conational operator ?:

Size of operator Sizeof

67. Explain type conversion

Converting data from one type to another type is called type

conversion. Three types of data type conversions are

A. Conversion from built-in type to class type.B. Conversion from class type to built-in type.

C. Conversion from one class type to another class type.


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68. What is the use of virtual base class?

The duplication of inherited members due to multi paths can be

avoided by making the common base class (ancestor class).

69. What is the use of public access mode?

Public accessible members can be accessed from outside the class.

70. What is the default access mode in a class?

Private is the default access mode in a class

71. What are the functions supported by file stream class for

performing I/O operations?

Put() get() open() close() read() write()

72. What are the file ptr functions available in C++

what are the functions for manipulation of file pointers?

seekg() -> indicates the file pointer position moved by

the get pointer

seekp() -> indicates the file pointer position moved by

the put pointer

tellg() -> tells the file position moved by get pointer

tellp() -> tells the file position moved by put pointer

73. What are the file stream classes available in C++?

fstream, ifstream, ofstream, fstreambase and filebuf

74. What is an I/O stream?

A stream is a sequence of bytes. The source stream that

supplies data to the program is called input stream and the destination

stream that receives data from the program is called output stream.

75. What is dynamic initialization?

C++ permits initialization of variables at run time. This is

referred as dynamic initialization.


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OBJECT ORIENTED

PROGRAMMING IN C++

QUESTIONS

WITH

DESCRIPTIVE ANSWERS


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1. Explain the basic concepts of OOP

The basic concepts of OOP are Class, object, Data abstraction,

Encapsulation, Inheritance, Polymorphism, Dynamic binding and message

passing.

A. Class


is called class. A class is a new data type that contains member variables

and member functions that operate on the variables. A class is defined with

a keyword class.

A class is a user defined data type. It is a blue print for objects,

which defines the variable and methods common to all objects of a certain

kind.

Example: person class:

class person //New data type class person

{

char name[30]; //Data member

int age; //Data member

public: //Public access

void getdata(void); //Function declaration

void display(void);

};

B. Objects

The class variables are known as objects. An instance of a class is

known as an object. Objects are Run time entities in object oriented

programming

Example: person object p:

main()

{

person p; //Person object

p.getdata();

p.display();}


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C. Data abstraction

The act of representing essential features without including the

background details or explanations is known as data abstraction. Class uses

the concept of abstraction. Since class uses the concept of data abstraction,

they are known as Abstract Data Types.

D. Encapsulation

The wrapping up of the data and functions into a single unit (called

class) is known as encapsulation. Data encapsulation is the most striking

feature of a class. The data is not accessible to the outside world and only

those functions which are wrapped in the class can access it. these functions

provide the interface between the objects data and the program. This

insulation of the data from direct access by the program is called data

hiding.

E. Inheritance

The mechanism of deriving a new class from existing class is called

inheritance. There are different kinds of inheritance namely single,

multiple, multilevel inheritance, Hierarchical and Hybrid

Ex.: Single Inheritance

A derived class with only one base class is called Single Inheritance

Class Child : public Parent

F. Polymorphism

The ability to take more than one form is called polymorphism.

That is, more operations in same name. Polymorphism means one name

with multiple forms. Run time polymorphism and compile time

polymorphism are the two kinds of polymorphism.

Parent

Child


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G. Dynamic binding

The addresses of the functions are determined at run time ratherthan compile time (late binding). Linking of a procedure to execution code

is done at run time is called dynamic binding.

H. Message Communication

Objects communicate with one another by sending and receiving

information. A message for an object is a request for execution of

procedure. Message passing involves specifying the name of the object, the

name of the function (message) and information to be sent. Example is

given below :

Polymorphism

Compile timePolymorphism

Run timePolymorphism

Function

overloading

Operator

overloading

Virtual

functions

employee . salary (name);

object message Information

ob ect


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2. What are the Principal Advantages of OOP?2. What are the merits of OOP Methodology?

2. What are the Benefits of OOP/OOM?

OOP offers several befits to both the program designer and the user.The principal advantages are:

Through inheritance, we can eliminate redundant codeand extend the use of existing classes

We can build programs from the standard working modules(Reusability of code by Inheritance).

The principle of Data hiding (encapsulation) helps programmerto build secure program.

Program developed by modules through classesIt is possible to have multiple instances of class objects to co-

exist without any interface.

It is possible to map objects in the problem domain to thoseobjects in the program.

It is easy to Portion the work based on objectsData centered and Bottom-Up design approach.Object oriented systems can be easily upgraded from small to

large systems.

Message passing technique for communication between objects.Software complexity can be easily managed.

3. Explain object oriented programming paradigm

3. Explain object oriented programming approach

3. Explain object oriented programming Methodology

Object oriented programming approach provides solution to some

of flaws encountered in procedural approach. OOP treats data as a critical

element in the program development and does not allow it to flow freely

around the system. It ties data more closely to the functions that operates on

it and protects it from accidental modification from outside functions.

OOP allows decomposition of a problem into a number of entities

called objects and then builds data and functions around these entities. The

organization of data and functions in OOP is shown in the figure given

below:


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The data of an object can be accessed only by the functions

associated with that object. However, functions of one object can access thefunction of other objects.

Some of the striking features of OOP are:

Emphasis is on data rather than procedure. Programs are divided into elements called objects. Data structures are designed such that they characterize the

objects (Abstraction).

Functions and data tied together into a single unit calledencapsulation.

Data is hidden (private data) and cannot be accessed byexternal functions.

Objects may communicate with each other through functions. New data and functions can be easily added whenever

necessary (inheritance).

Bottom-up approach in program design.OOP is the most recent concept among programming paradigms.

Class and objects are the building blocks in OOP. An object is considered

to be a partitioned area of computer memory that stores data and set of

operations that can access that data.

Data

Functions

Object A

Data

Functions

Object B

Data

Functions

Object C


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4. Write the difference between C & C++.

C:

C is a Procedural Programming. It was developed at AT & T Bell

laboratories in 1972 by Dennies Ritchie From the language B.

C++:

C++ is an Object Oriented Programming. It was developed at AT

& T Bell laboratories in the early 1980s by Bjarne Stroustrup.from the

languages C and Simula67.

C C++

C is a subset of C++ C++ is super set

Procedure Oriented

Programming (POP)

Object Oriented Programming (OOP)

Top down approach Bottom up approach

Structured Programming Modular Programming

Importance in given for program Importance is given for data

Does not support objects Supports objects

C provides

Action/Structure/function

oriented programming

C++ provides Object Oriented

Programming with features like

Abstraction, Encapsulation,

Inheritance and polymorphism

C is not a strong type checkinglanguage

C++ is a strong type checkinglanguage

C does not supports error

handling

C++ supports sophisticated error

handling using the Exception Handling

Function overloading and

function overriding are not

availed in C

Function overloading and function

overriding can be done in C++

C does not supports Templates C++ supports Templates

Scanf & printf functions for

getting and showing values

Cin and cout stream operators for

getting and showing values

Input and out put format like

%d, %f, %c are required in

I/O process

No format is required in c++ in I/O

process


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5. Explain Data Types in C++Data Types are the kind of data that variables hold in a

programming language. The ability to divide data into different types in

C++ enables one to work easily with complex objects.

C++ Basic Data Types and their size in bytes

Type Bytes

char, unsigned char and signed char 1int, unsigned int, signed int and short int 2

long int, unsigned long int and signed long int 4

float 4

double 8

long double 10

char and signed char value varies from -128 to 127

unsigned char value varies from 0 to 255

int and signed int value varies from -32768 to 32767

unsigned int value varies from 0 to 65535


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6. Explain Storage Class / Storage Specifiers

Storage Class is another qualifier (like long or unsigned) that can be

added to a variable declaration. The four storage specifiers are auto, static,

extern and register. static and register variables are automatically

initialized to zero when they are declared. Auto variables are not initialized

with appropriate values based on their data type. These variables get

undefined values known as garbage.

Storage Meaning Example

auto Defines local variable known to

the block in which they are

defined. By default the local

variables are auto hence rarely

used.

void main()

{ autofloat ratio;

int kount;

}

static Global scope but one time

initialization

void fun()

{

static int x;

x++;

}

extern Global variable known to all

functions in the current program. These variables are

defined in another program.

extern int filemode;

extern void factorial();

register The modifier register instructs

the compiler to store the

variable in the CPU register to

optimize access.

void fun()

{register int I;}


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7. What are the difference between break and continue?

Break statement tells to compiler that to exit from a loop or switch

case. If loops are nested, the break would only exit from the loop

containing it. That is, break will exit only a single loop. Break statement at

the end of the switch case causes an exit from the switch statement.

The continue statement tells to compiler that to skip the remaining

statements and continue with next iteration.

Break Continue

Break will exit only from a single

loop

Continue will skip remaining lines

for one iteration.

Used in loop and branch control Used only in loop control

Loop is terminated Loop is continued

while(test-con)

{---------

if(cond)

break;--------

}

while(test-con)

{---------

if(cond)

continue;

--------

}

for(ini;test;inc){

---------

if(cond)continue;

--------

}

switch(expresion)

{case 1:

block1

break;case 2:

}


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8. Explain Control Structures in C++

Statements in a program need not necessarily be executed in a

sequential order. Some segments in a program are executed based on a

condition. In such situations the flow of control jumps from one part of the

program to another. Program statements that cause such jumps are called as

control statements or control structures.

Control structures

Sequence Selection (Decision making & Branching)

Control structure

SequenceSelection Loop structure

if ,if else switch do-while while, for


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Loop

IF (Branch)

if (expression is true){

action 1;

}

action 2;

action 3;

If(age>60){

Int_rate=Int_rate+0.5;

}

Interest=P*y*Int_rate;

Cout


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SWITCH (Multiple branches)

switch (expression )

{

case 1:

{

action 1;

}

case 2:

{

action 2;

}

case 3:

{action 3;

}

default:

{

action 4;

}

}

action 5;

Switch(option)

{

case 1:

{

Push();

}

case 2:

{

Pop();

}

case 3:

{Display();

}

default:

{

Cout


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The do-while is an exit-controlled loop. Based on the true condition, the

control is transferred to back to loop.

WHILE (entry controlled loop)

while(condition is

true)

{

action 1;

}

action 2;

Int n=100,sum=0, i=0;

while(i


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9. Explain Classes and objects with example

Class

The most important feature of C++ is the Class. Its significance is

highlighted by the fact that Bjarne Stroustrup initially gave the name Cwith Classes . A class is a new way of creating and implementing a user

defined data type.


is called class. In C++, A class is a new data type that contains member

variables and member functions that operate on the variables. A class is

defined with a keyword class.

A class is a user defined data type. It is a blue print for objects,

which defines the variable and methods common to all objects of a certain

kind.

Characteristics of a class:

The keyword class specifies user defined data type class name The body of a class is enclosed within braces and is

terminated by a semicolon

The class body contains the declaration of variables andfunctions

The class body has three access specifiers ( visibility labels)viz., private , public and protected

Specifying private visibility label is optional. By default themembers will be treated as private if a visibility label is not

mentioned

The members that have been declared as private, can beaccessed only from within the class

The members that have been declared as protected can beaccessed from within the class, and the members of the

inherited classes.

The members that have been declared as public can beaccessed from outside the class also


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Structure of a class

Class Name

Data Declaration

Function

Declaration

Function

Definition

#include

class item //class declaration

{

int number; //private data member

float cost; //private data member

public:

void getdata (void);//prototype declaration

void putdata(void); //function defined here

};

void item :: getdata (void) //function definition

{

coutnumber;

coutcost;

}

void item :: putdata (void) //function definition{

cout


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main()

{

item x; //create object

cout


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Array of objects

item x[100];

The above line will create 100 arrays of objects of type item.

The below lines will collects data for 100 objects.

for(int i=0;i


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10. Explain constructor and destructor with suitable example Constructor

A constructor is a special function whose task is to initialize the

objects of its class. It is special because its name is the same as the class.

Class stack

Class stack

{ Int top;

Public:

stack(); //constructor

~ stack(); //destructor

push();

pop();

disp();

- - - -

};

Example: Constructor

stack ::stack()

{

top=0;

}

Special characteristics of constructors:

They should be declared in public section. They are invoked automatically when the objects are created. They do not have return types. So they cannot return values. They cannot be inherited. Like other C++ functions, they can have default arguments. Constructors cannot be virtual. We cannot refer to their addresses.

Types of Constructors

1. Parameterized constructors

The constructors that can take arguments are called parameterized

constructors.


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class integer

{ int m,n;

public:

integer(int x, int y) //parameterized constructor

..}

2. Default constructors

A constructor that accepts no parameter is called default

constructor. the default constructor for a class A is:

A::A().

3. Multiple constructors

More than one constructor with different arguments is called

multiple constructors.

class integer

{ int m,n;

public:

integer() {m=0; n=0;} // constructor1

integer(int x, int y) // constructor2

{m=a;n=b;}

integer(integer &i) // constructor3

{m=i.m;n=i.n;}

..

}

4. Default arguments constructors

A constructor with default argument is called default argument

constructor.

class complex

{ float real, imag;

public:

complex(float real, float imag=0);

.


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}

complex c(5.0)

real variable gets 5.0 and imag variable get 0 (by default)

5. Dynamic initialization of objects

the class objects can be initialized dynamically too. that is, the

initial value of an object may be provided during run time.

stack ::stack()

{

top=0;

}

6. Copy constructor

A constructor can accept a reference to its own class as a parameter.

that is,

Class A

{

.

public:

A(A &);

}

A copy constructor is used to declare and initialize an object from another

object.

7. Dynamic constructors

Allocation of memory to objects at the time of their construction is

known as dynamic construction for objects. The memory is allocated with

the help of the new operator.

Destructor


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A Destructor is used to destroy the objects that have been created

by a constructor. Like a constructor, the destructor is a member function

whose name is same as the class name but it is preceded by tilde.

Example: Destructor

~stack()

{

delete st;

cout


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11. Compare and contrast between constructor and destructor?

Constructor and destructor

Constructor Destructor

SimilaritiesConstructors does not have a return

type

Destructor also does not have a

return type

Constructor is a member function to

a class

Destructor is also a member

function to a class

Constructor uses class name as their

names

Destructor also uses class name as

their with ~ .

Differences

Provided to a class to initialize an

object

Cleans up or de-initializes each

object before object is destroyed

It has same name as its class It has same name as its class with

prefixed ~ (tilde)

Constructors can have arguments Destructor has no arguments

Multiple constructors can exists Multiple destructors can not exists

Constructors can be overloaded Destructors can not be overloaded


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12. What is function overloading?Many functions with same name created to perform different tasks.

Family of functions with one function name but with different

argument lists. Depending on the arguments correct function will be

invoked. This process is known as function overloading. This is also known

as function polymorphism (compile time polymorphism).

#include

class sample

{

public:

int add(int, int); //prototype1

float add(float,float); //prototype2

add(int, float); //prototype3

};

int sample :: add (int x, int y)

{ return (x+y);}

float sample :: add (float x, float y)

{ return (x+y);}

float sample :: add (int x, float y)

{ return (x+y);}

main(){ sample s;

//function call

cout


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13. Explain Operator overloading with an exampleC++ permits us to add two variables of user-defined types with the

same syntax that is applied to the basic types. this means that C++ has the

ability to provide the operators with a special meaning for a data type. The

mechanism of giving such a special meanings to an operator is known as

operator overloading.

Operator overloading can be done with the help of a special

function is called operator function. The general form of operator function

is given below:

Where returntype is the type of value retuned by the specified operation

and op is the operator being overloaded. the op is proceeded by he keywordoperator.

Operatorop is the function name.

Operator function must be either member functions (non static) or

friend function.

List of operators that cannot be overloaded are:

Direct member access operator .

De-reference pointer to class member operator .*

Scope resolution operator ::

Conational operator ?:Size of operator Sizeof

List of friend function cannot be used are:

Assignment operator =

Function call operator ()

Subscripting operator []

Class member access operator ->

.

Operator functions are declared as follows:

vector operator + (vector); // vector addition

vector operator - (); // unary minus

friend vector operator + (vector, vector); // vector addition

friend vector operator - (vector); // unary minus

returntype classname :: operator op (arg-list){

Function body //task defined

}


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int operator == (vector) //comparison

friend int operator == (vector, vector) //comparison

Rules for overloading operators:

Although it looks simple to redefine the operators, there are somerestrictions and limitations in operator overloading. Some of them are listed

below:

1. Only existing operators can be overloaded. New operators cannot becreated.

2. The overloaded operator must have at least one operand that is ofuser defined type.

3. We cannot change the basic meaning of the operator.4. Overloaded operators must follow the rules of the original

operators.

5. There are some operators that cannot be overloaded.6. We cannot use friend functions to overload certain operators.7. Unary operators are overloaded by means of a member function

with out argument.

8. Binary operators are overloaded through a member function withone argument and a fiend function with two arguments.

9. The left-hand operand must be an object for binary operatoroverloading.

10.Binary arithmetic operators such as + - * and / must return a value.Example1: Program for unary operator overloading

The unary operator is overloaded with single operand. The unary

operator is used to change the negative value of the operand.

Overloading unary operators

#include

class point

{

int x;

int y;

public:

void getdata(int a , int b);

void display(void);

void operator - (); //// unary minus


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};

void point :: getdata(int a, int b)

{

x=a; y=b;

}void point :: display(void)

{

cout


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public:

complex(){ } //constructor1

complex(float real, float imag) //constructor2

{

x=real;y=imag;

}

complex operator+(complex);

complex operator*(complex);

void display(void);

};

complex complex :: operator+(complex c)

{

complex temp; //temprary

temp.x=x+c.x; //real part addition

temp.y=y+c.y; //imaginary part addition

return temp;

}

complex complex :: operator*(complex c)

{

complex temp; //temprary

temp.x=(x*c.x)-(y*c.y); //real part multiplication

temp.y=(x*c.y)+(y*c.x); //imaginary part multiplication

return temp;

}

void complex :: display(void)

{

cout


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c4=c1*c2; //invoke operator*()

cout


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14. Explain type conversion with example

Converting data from one type to another type is called type

conversion. Three types of data type conversions are

A. Conversion from built-in type to class type.

B. Conversion from class type to built-in type.

C. Conversion from one class type to another class type.

Conversion takes place inConversion

required Source class Destination

class

Basic ->

Class

Not

applicable

Constructor

Class ->Basic

Castingoperator

Notapplicable

Class ->

Class

Casting

operator

Constructor

A. Basic to Class Type

The conversion from basic type to class type is easy to accomplish.

We can use constructor to build a string type object from a char* type

variable. This is an example fordefacto type conversion.

Class String constructor:

The string constructor builds a string type object from char* type

variable a. The variables length and p are data members of the class string.

This constructor is used for conversation from basic data type char * to

string type.

string :: string(char *a)

{ length = strlen(a);

P = new char[length + 1];

strcpy(P,a);

}


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Example:

The last statements are used to converts data from char * type to string

type.

B. Class to Basic Type

C++ allows us to define a overload a casting operator that could be

used to convert a class type to a basic type. The general form of an

overloaded casting operator function, usually referred to as a conversionfunction, is:

Example: Converstion from class type string to basic type char * as

follows:

string s3=Dr Pauls Engineering College

char * name3=char* (s3); or

char * name3=s3;

C. One Class to Another Class

We have seen data conversion technique from a basic to class type

and a class to basic type. But there are situations where we would like toconvert one class type data to another class type.

Example:

operator typename()

{

(Function staetments )

}

objX = objY; //ob ects of different t es

string s1,s2;

char * name1 = Dr Pauls;

char * name2 = Engineering College;

s1=string(name1); //calls constructors2=name2; //implicitly calls constructor

string : : operator char*()

{return(p);

}


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Where objX is an object of class X and objY is an object of class Y. The

class Y type data is converted to the class X type data and the converted

value is assigned to the objX. Since the conversion takes place from class

Y to class X, Class Y is Known as source Class and Class X is known as

the destination Class.Such conversions between objects of different classes can be carried

out by either a constructor or a conversion function.

//polar to cartesian.cpp

#include

#include

#include

class polar

{ public:

float r;

float a;

polar(float i=0, float j=0) //constructor

{ r=i;

a=j;

}

};

class cartesian

{

public:

float x;

float y;

cartesian(float m=0, float n=0) //constructor

{ x=m;

y=n;

}

cartesian(polar p) //type conversion

{ x=p.r*cos(p.a);

y=p.r*sin(p.a);

}

void show()

{

cout


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void main()

{

polar ppoint(4.25,0.785); //angle PI/4=0.785

cartesian cpoint;

cpoint=ppoint; //Polar object is assignedcpoint.show();

getch();

}

Output

( 3.0005, 3.0004 )


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15. Explain inheritance / Extending Classes

The mechanism of deriving a new class from existing class is called

inheritance. The existing class is known as base class, super class or parent

class; the new class is known as sub class, derived class or child class.

Defining derived classes

A derived class is defined by specifying its relationship with the base class

in addition to its own details. The general form of defining a derived class

is:

class derived_clas_name : visibility_mode base_class_name

{

//members of derived classes

}

Types of Inheritance

There are different kinds of inheritance namely single, multiple, multilevel

inheritance, Hierarchical and Hybrid

Single Inheritance means a class derived from only one of existing class.

(A derived class with only one base class is called Single Inheritance)

Class Child : public Parent

{ . . .};

Multilevel Inheritance means a class derived from only one of existing

class.

Parent

Derived1

Derived2

Parent

Child


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Class Derived1 : public Parent

{ . . .};

Class Derived2 : public Derived1

{ . . .};

Multiplelevel Inheritance means a class derived from more than one ofexisting classes.

Class Derived1 : public Parent1, public Parent2

{ . . .};

Hierarchical Inheritance means a class my be inherited by more than one

classes.

Class Derived1 : public Parent1

{ . . .};


{ . . .};


{ . . .};

Hybrid Inheritance means combinations of the above inheritance.

Class Parent1 : public GrandParent1

{ . . .};

Class Parent2 : public GrandParent1

Parent1

GrandParent1

Derived3

Parent2

Derived1

Parent1

Derived2 Derived3

Parent1 Parent2

Derived1


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{ . . .};

Class Derived3 : public Parent1, public Parent12

{ . . .};

Multi path inheritance / Virtual base classes

The child has two direct base classes parent1 and parent2 which

themselves have a common base class Grandparent. The child inherits

the traits ofGrandparent via two separate paths. It can also inherit directly

as shown by a broken line. The Grandparent is sometimes referred to as

indirect base class.

Inheritance by the child as shown in the above figure might pose

some problems. All the public and protected members of Grandparent are

inherited into child twice, first via parent1 and again via parent2. This

means child would have duplicate sets of the members inherited from

grandparent. This introduces ambiguity and should be avoided.

The duplication of inherited members due to this multiple paths

can be avoided by making the common base class (ancestor class ) as

virtual base class while declaring the direct or intermediate base classes as

shown below:

Class A // Grandparent

{};

Class B1: virtual public A //parent1

{};

Class B2: public virtual A //parent2

{};

Class C: public B1, public B2 //child{

//only one copy of a will be inherited

};

Derived1

Grand Parent

Child

Derived2


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Access mode in inheritance

With in

class

With

derived

class

Main /

other class

Private Yes No No

Protected Yes Yes No

Public Yes Yes Yes

Private and public inheritance

Data public

derived

class

protected

derived

class

Private

derived

class

Private not

accessible

not

accessible

not

accessible

Protected protected protected Private

Public public protected Private

Sample program for hybrid inheritance


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16. Explain pointers in C++

Pointers

Pointers data type is one of the strengths of the C++ language. A

pointer is a variable which holds the memory address of another variable.

The advantages of pointers

Pointer allows passing variables, arrays, functions, strings and structuresas function arguments.

Pointer facilitates functions to modify calling argumentsPointer supports dynamic allocation and de allocation of memory

segments.

It allows to establish links between data elements such as linked lists,stacks, queues, trees and graphs.

Initialization and declaration of pointers

int *ip; //integer pointer declaration

ip = & x; //address of x assigned to ip

*ip =50 //50 assigned to x through indirection

Constant pointer

char * const ptr1 = GOOD; // constant pointer

we cannot modify the address of ptr1

Pointer to a constant

int const * ptr =&m; // Pointer to a constant

ptr2 can point to any variable, but the contents of what it points to cannot

be changed.

Pointers to objects

#include

Class Base

{ public:void display() { cout


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main()

{

Base B; Base *ptr; //declarations

coutdisplay() //calls Base version

ptr->show() //calls Base version

}


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17. Explain virtual function

Same function name in both the base and derived classes,

the function in the base class is declared as virtual, C++ determines which

function to use at run time based on the type of object pointed to by the

base pointer, rather then the type of the pointer. Thus by making the base

pointer to point to different objects, we can execute different versions of

virtual function

It is used for late binding. That is, for run time polymorphism.

Example

#include

Class Base

{ public:

void display() { cout


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Output

Ptr points to base

display base

show base

Ptr points to deriveddisplay base

show derived

Ptr is always point to base object. but run time polymorphism is achieved

by adding a key word virtual to show() function in base class.


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18. Explain virtual functions with a program (16)

Run time polymorphism is achieved by the concept of

virtual functions. Run time polymorphism refers to the property by which

Objects belonging to different classes are able to respond to the same

function in different forms. An essential requirement of polymorphism is

the ability to refer to objects without any regard to their class. This

necessitates the use of a single pointer variable to refer to the objects of

different classes.

Here we use the pointer to base class to refer to all the derived

objects. But we just discovered that a base pointer, even when it is made to

contain the address of a derived class, always executes the function in the

base class. The compiler simply ignores the contents of the pointer and

chooses the member function that matches the type of the pointer. How do

we then achieve polymorphism? It is achieved using what is known as

virtual function.

Same function name in both the base and derived classes, the

function in the base class is declared as virtual, C++ determines which

function to use at run time based on the type of object pointed to by the

base pointer, rather then the type of the pointer. Thus by making the base

pointer to point to different objects, we can execute different versions of

virtual function

It is used for late binding. That is, for run time polymorphism. run

time polymorphism is achieved only when a virtual function is accessed

through a pointer to the base class.

Example:

Consider a book shop which sells both books and video-tapes. We can

create a class known as media that stores the title and price of a publication.

We can then create two derived classes, one for storing the number of

pages in a book and another for storing the playing time of a tape. The

following figure shows class hierarchy for the book shop

mediavirtual void display()

book tape


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//run time polymorphism-virtual functions

#include

#include

class media

{ protected:char title[50];

float price;

public:

media(char *s, float a)

{ strcpy(title,s);

price=a;

}

virtual void display() { } //empty virtual function

};

class book : public media

{ int pages;

public:

book (char * s, float a, int p) :media(s,a)

{ pages = p;

}

void display()

{ cout


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main()

{ char *title;

float price, time;

int pages;

cout title;

cout > pages ;

cout > price;

book b1(title, price,pages);

cout title;

cout > time ;

cout > price;

tape t1(title, price,time);

media* m1;

media *m2;

m1=&b1;

m2=&t1;

cout


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19. Explain polymorphism

The ability to take more than one form is called polymorphism.

That is, more operations in same name. Polymorphism means one name

with multiple forms. The concept of polymorphism is implemented using

the overloaded functions and operators. Polymorphism can be divided into

Run time polymorphism and compile time polymorphism.

Compile time polymorphism

The overloaded member functions are selected for invoking by

matching arguments by number of arguments and its type. This information

is known to the compiler at the compile time and, therefore, compiler is

able to select the appropriate function for a particular call at the compile

time itself. This is called early binding orstatic binding orstatic linking.

Also known as compile time polymorphism. Early binding simply means

that an object is bound to its function at compile time.

Run time polymorphism

Consider the base and derived class with same function name and

prototype in both classes.

class A

{ int x;

public:

void show() {} //show() in base class

};class B : public A

{ int y;

public:

Polymorphism

Function

overloading

Operator

overloading

Virtual

functions

Compile time

Polymorphism

Run time

Polymorphism


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void show() {} //show() in derived class

};

Here the same show() function is available in both classes. That is,

function overloading is not possible. Therefore static binding fails. In fact,the compiler does not know which function to chose.

The process of selecting the appropriate member function at run

time is called run time poly morphism. It can be achieved using virtual

functions. It is also called as late binding ordynamic binding

Thus, Run time polymorphism refers to the property by which

Objects belonging to different classes are able to respond to the same

function in different forms. Dynamic binding is the one of the powerful

features of C++. This requires the use of pointers to objects.

NOTE: for 16 mark write function overloading, operator overloading and

virtual functions.


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write data

(to files)

get data

(from key

board)

cin>>

20. Explain file handling

Introduction

File input and output streams

The I/O system of C++ handles file operations which are

very much similar to the console input and out put operations. It uses file

stream (sequence of bits or bytes) as an interface between the programs and

the files. The stream that supplies data to the program is known as input

stream and the one that receives data from the program is known as output

stream.

Stream classes for file operations

put datato screen

cout


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Details of stream classes

Class Contents

filebuf Its purpose is to set the file buffers to

read and write.

fstreambase Provides operations common to the file

streams.

ifstream Provides input operations

ofstream Provides output operations

fstream Provides support for simultaneous input

and output operations

//writing and reading objects in a file

#include

#include

class inventory

{

char name[10];

int code;

float cost;public:

void readdata (void);

void writedata(void);

};

ios

streambuf ostreamistream

iostream

fstream ofstreamifstream

fstream base

filebuf

iostream.h

file

fstream.h

file


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void inventory :: readdata (void)

{

coutname;

coutcode;

coutcost;}

void inventory :: writedata (void)

{

cout


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File mode parameters

No. Mode:

parameters

Meanings

1 ios :: in Open file for reading only2 ios :: out Open file for writing only

3 ios :: app Append to end-of-file

4 ios :: ate Go to end-of-file on opening

5 ios :: binary Open as binary file

6 ios :: nocreate Open fails if the file does not

exists

7 ios :: noreplace Open fails if the file already

exists

8 ios :: trunc Delete the contents of the file

if it exists

ERROR HANDLING DURING FILE OPERATIONS

We may get Errors when one of the following occurs:

A file which we are attempting to open for reading does not exist.The file name used for a new file may already exist.We may attempt an invalid operation such as reading after end-of file.There may not be any space in the disk for storing more data.We may use an invalid file name.We may attempt to perform an operation when file is not opened for that

purpose.

ERROR HANDLING FUNCTIONS

Function Return value and meanings

eof() Returns true (non-zero value) if end-of file is

encountered while reading; otherwise returns false

(zero).

fail() Returns true when input or output failed.

bad() Returns true when invalid operation or

unrecoverable error has occurred. if it is false, then

it may be possible to recover from error

good() Returns true if no error has occurred


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21. Explain class and function templates

Single function or class for which a family of similar functions or

class in a generic manner is called templates.

Class template

A single generic class for set of multi class with similar objective is called

class template

Example

Template

T sum (T *arr, int n)

{

T temp=0;

for( int i=0;i


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6. Explain Exception handling.

Exceptions are run time anomalies or unusual events like divide by

zero, out of range, index overflowing, running out of memory or disk space

error etc.

C++ supports exception handling mechanism to detect and manage

runtime errors.

Exceptions are classified into two major types. They are:

1. Synchronous

Error such as out of range, index overflowing, running out of

memory or disk space are called as synchronous type of exceptions.

2. Asynchronous

Events that are passed beyond the control of program such as

keyboard interrupts are called as Asynchronous.

Note: C+ supports Synchronous exceptions only.

There are two basic blocks to handle exceptions. They are1. Try -> to throw the exception

2. Catch -> to catch exception

Exce tions

Synchronous

Exceptions

Asynchronous

Exceptions

Normal code

code that

cause exception

yes

noexception

handler

Normal code


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Syntax for Try block

try

{

.

throw(exception)}

Syntax for catch block

catch(argument type)

{

.

}

Steps involved in handling exceptions are:

1. Fix the problem

2. Inform that Error is occurred3. Receive error information

4. Take corrective action

Purpose of exception handling is to detect and report exception

circumstances, so that appropriate action can be taken. The mechanism

used in C++ to handle exception is throwing and catching exceptions.


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22. Explain String manipulation in detail

STRINGS: A string is a sequence of characters. C++ does not

support string data type. But C++ provides a library header file for string

manipulation is called string.h. Using string.h we can easily perform stringoperations like copy, finding string length, finding substring, etc.

The string class is a very large and includes many constructors,

member functions and operators. We may use these constructors, member

functions and operators to achive the following.

Creating String objects Reading String objects Displaying String objects to the screen Finding a sub-string from a String modifying String objects Comparing String objects Adding String objects Accessing character in a string Obtaining the size of the string

Constructors

String() //create empty string

String(const char *str) //creating a String objects from a null-

terminated string

String(const string &str) //creating a String objects from a null-terminated string

Functions

append() at() compare() begin() end()

erase() find() insert() length() substr()

Operators

+, =, +=, ==, 1=, =

Examples

String s1 (Dr Pauls);String s2;

s2=s1;

s2=s1+Engineering College


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Biography

Mr. G. Appasami was born in Pondicherry, India in 1980. He received his Master of

Science degree in Mathematics, Master of Computer Applications degree and Master

of Technology degree in Computer Science and Engineering from Pondicherry

University, Pondicherry, India. He received his Master of Philosophy in Computer

Science from Alagappa University, Karaikudi, India.

Currently he is faculty in Dr. Pauls Engineering College, Villupuram and affiliated to

Anna University Chennai, Tamil Nadu, India. He is a life member of Indian Societyfor Technical Education, Computer Society of India, International Association of

Computer Science and Information Technology (Singapore) and International

Association of Engineers.

He also qualified Gate Exam. His Area of interests includes Network Security, image

processing and web technology. He has published more papers in national &

international journals and conference proceedings.

Email: [email protected]

Website: www.appas.110mb.com

Object Oriented Progamming in C++ [OOP in CPP Q&A]

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