UNIT 1

Fundamentals of Object Oriented Programming

Procedure Oriented Programming 

It employs top down approach.

Fig.: Structure of procedure oriented programming

Modular oriented programming

Generic oriented programming

Object Oriented Programming

It employs bottom up approach.

        Fig.: Structure of Object Oriented Programming

2.     What are the limitations of procedural programming

3.     What are the OOP Paradigms?

However, functions of one object can access the the functions of other objects.

Some of the striking features of object-oriented programming are

4.     Write a program to accept and display details of book.

Explanation

Step 1 : Every C++ program starts with header file “iostream.h” as it contains declarations of input and output streams in program.

Step 2 : Class “Book” is declared and defined. It consists of data members name, pages and price. Access specifier is not mentioned for these members so they are considered as private.

Step 3: Accept function accepts all the details of book. It shows new features cout, <<, cin, >>.

cout

Standard predefined object that represents standard output stream in C++.

5.     Give a brief Introduction to Class

  class Book

Structure of a class

Structure of a “Book” class

Structure of class declaration

We will discuss new terms in above declaration.

Class

Access Specifier

It specifies if class members are accessible to external functions (functions of other classes).

C++ provides three access specifiers :

1. private

2. public

3. protected

Data members

Data _type Variable_name;

e.g. int roll_no;

     float price;

string name;

Methods

Functions declared or defined within a class are known as member functions of that class. Member functions are also called as methods.

Table: Let us create a class Book

6.     Explain messages in detail with example

Programming languages like Smalltalk and Objective-C are considered more flexible than C++ because they support dynamic message passing. C++ does not support dynamic message passing; it only supports static message passing: when a method of an object is invoked, the target object must have the invoked method; otherwise, the compiler outputs an error.

Although the way C++ does message passing is much faster than the way Smalltalk or Objective-C does it, sometimes the flexibility of Smalltalk or Objective-C is required. This little article shows how it is possible to achieve dynamic message passing in C++ with minimum code.

Example

The supplied header contains an implementation of dynamic message passing. In order to add dynamic message passing capabilities to an object, the following things must be done:

Here is an example:

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//the dynamic-message-passing header

#include "dmp.hpp"

//the message signature

std::string my_message(int a, double b) { return ""; }

//a class that accepts messages dynamically

class test : public dmp::object {

public:

    test() {

        add_message(&::my_message, &test::my_message);

    }

    std::string my_message(int a, double b);

};

int main() {

    test t;

    std::string s = t.invoke(&::my_message, 10, 3.14);

}

How it Works

Each object contains a shared ptr to a map. The map's key is the pointer to the signature of the message. The map's value is a pointer to an internal message structure which holds a pointer to the method to invoke.

When a method is invoked, the appropriate message structure is retrieved from the map, and the method of the object stored in the message structure is invoked, using this as the target object.

The map used internally is unordered, for efficiency reasons.

The message map of objects is shared between objects for efficiency reasons as well. When a message map is modified, it is duplicated if it is not unique, i.e., the copy-on-write pattern is applied.

The code is thread safe only when the message maps are not modified while used for look-up by different threads. If a message map is modified, then no thread must send messages to an object at the same time.

The code uses the boost library because of:

7.     Give a short description on data encapsulation , data abstraction and information hiding , inheritance and polymorphism

Data encapsulation

Data abstraction and information hiding

Inheritance

                    Fig. : Inheritance

Polymorphism

       Fig. : Polymorphism

8.     What are identifiers and keywords?

C++ Identifiers

A C++ identifier is a name used to identify a variable, function, class, module, or any other user-defined item. An identifier starts with a letter A to Z or a to z or an underscore (_) followed by zero or more letters, underscores, and digits (0 to 9).

C++ does not allow punctuation characters such as @, $, and % within identifiers. C++ is a case-sensitive programming language. Thus, Manpower and manpower are two different identifiers in C++.

Here are some examples of acceptable identifiers −

mohd       zara    abc   move_name  a_123

myname50   _temp   j     a23b9      retVal

C++ Keywords

The following list shows the reserved words in C++. These reserved words may not be used as constant or variable or any other identifier names.

9.     What is the fundamentals data type of C++?

The table below shows the fundamental data types, their meaning, and their sizes (in bytes):

Data Type  Meaning     Size (in Bytes)

int   Integer     2 or 4

float   Floating-point    4

double  Double Floating-point   8

char   Character     1

wchar_t  Wide Character    2

bool   Boolean     1

void   Empty      0

1. int

The int keyword is used to indicate integers.

Its size is usually 4 bytes. Meaning, it can store values from -2147483648 to 214748647.

For example,

int salary = 85000;

2.  float and double

float and double are used to store floating-point numbers (decimals and exponentials).

The size of float is 4 bytes and the size of double is 8 bytes. Hence, double has two times the precision of float. To learn more, visit C++ float and double.

For example,

float area = 64.74;

double volume = 134.64534;

As mentioned above, these two data types are also used for exponentials. For example,

double distance = 45E12    // 45E12 is equal to 45*10^12

3. char

Keyword char is used for characters.

Its size is 1 byte.

Characters in C++ are enclosed inside single quotes ' '.

For example,

char test = 'h';

Note: In C++, an integer value is stored in a char variable rather than the character itself. To learn more, visit C++ characters.

4.  wchar_t

Wide character wchar_t is similar to the char data type, except its size is 2 bytes instead of 1.

It is used to represent characters that require more memory to represent them than a single char.

For example,

wchar_t test = L'ם'  // storing Hebrew character;

10.  Explain structure in detail with examples and difference of structure and class

C++ Structs

In C++, classes and structs are blueprints that are used to create the instance of a class. Structs are used for lightweight objects such as Rectangle, color, Point, etc.

Unlike class, structs in C++ are value type than reference type. It is useful if you have data that is not intended to be modified after creation of struct.

C++ Structure is a collection of different data types. It is similar to the class that holds different types of data.

The Syntax Of Structure

In the above declaration, a structure is declared by preceding the struct keyword followed by the identifier(structure name). Inside the curly braces, we can declare the member variables of different types. Consider the following situation:

In the above case, Student is a structure contains three variables name, id, and age. When the structure is declared, no memory is allocated. When the variable of a structure is created, then the memory is allocated. Let's understand this scenario.

How to create the instance of Structure?

Structure variable can be defined as:

Student s;

Here, s is a structure variable of type Student. When the structure variable is created, the memory will be allocated. Student structure contains one char variable and two integer variable. Therefore, the memory for one char variable is 1 byte and two ints will be 2*4 = 8. The total memory occupied by the s variable is 9 byte.

How to access the variable of Structure:

The variable of the structure can be accessed by simply using the instance of the structure followed by the dot (.) operator and then the field of the structure.

For example:

In the above statement, we are accessing the id field of the structure Student by using the dot(.) operator and assigns the value 4 to the id field.

C++ Struct Example

Let's see a simple example of struct Rectangle which has two data members width and height.

Output:

Area of Rectangle is: 40

C++ Struct Example: Using Constructor and Method

Let's see another example of struct where we are using the constructor to initialize data and method to calculate the area of rectangle.

Output:

Area of Rectangle is: 24

Structure v/s Class