C++ OOP Tutorial

 

C++ Object Oriented programming tutorial 

The prime purpose of C++ programming was to add object orientation to the C programming language, which is in itself one of the most powerful programming languages.

The core of the pure object-oriented programming is to create an object, in code, that has certain properties and methods. While designing C++ modules, we try to see whole world in the form of objects. For example a car is an object which has certain properties such as color, number of doors, and the like. It also has certain methods such as accelerate, brake, and so on.

There are a few principle concepts that form the foundation of object-oriented programming −

Object

This is the basic unit of object oriented programming. That is both data and function that operate on data are bundled as a unit called as object.

Class

When you define a class, you define a blueprint for an object. This doesn't actually define any data, but it does define what the class name means, that is, what an object of the class will consist of and what operations can be performed on such an object.

Abstraction

Data abstraction refers to, providing only essential information to the outside world and hiding their background details, i.e., to represent the needed information in program without presenting the details.

For example, a database system hides certain details of how data is stored and created and maintained. Similar way, C++ classes provides different methods to the outside world without giving internal detail about those methods and data.

Encapsulation

Encapsulation is placing the data and the functions that work on that data in the same place. While working with procedural languages, it is not always clear which functions work on which variables but object-oriented programming provides you framework to place the data and the relevant functions together in the same object.

Inheritance

One of the most useful aspects of object-oriented programming is code reusability. As the name suggests Inheritance is the process of forming a new class from an existing class that is from the existing class called as base class, new class is formed called as derived class.

This is a very important concept of object-oriented programming since this feature helps to reduce the code size.

Polymorphism

The ability to use an operator or function in different ways in other words giving different meaning or functions to the operators or functions is called polymorphism. Poly refers to many. That is a single function or an operator functioning in many ways different upon the usage is called polymorphism.

Overloading

The concept of overloading is also a branch of polymorphism. When the exiting operator or function is made to operate on new data type, it is said to be overloaded.

Hope you have already understood the concept of C++ Template which we have discussed earlier. The C++ STL (Standard Template Library) is a powerful set of C++ template classes to provide general-purpose classes and functions with templates that implement many popular and commonly used algorithms and data structures like vectors, lists, queues, and stacks.

At the core of the C++ Standard Template Library are following three well-structured components −

Sr.No	Component & Description
1	Containers Containers are used to manage collections of objects of a certain kind. There are several different types of containers like deque, list, vector, map etc.
2	Algorithms Algorithms act on containers. They provide the means by which you will perform initialization, sorting, searching, and transforming of the contents of containers.
3	Iterators Iterators are used to step through the elements of collections of objects. These collections may be containers or subsets of containers.

We will discuss about all the three C++ STL components in next chapter while discussing C++ Standard Library. For now, keep in mind that all the three components have a rich set of pre-defined functions which help us in doing complicated tasks in very easy fashion.

Let us take the following program that demonstrates the vector container (a C++ Standard Template) which is similar to an array with an exception that it automatically handles its own storage requirements in case it grows −

#include <iostream>
#include <vector>
using namespace std;
 
int main() {

   // create a vector to store int
   vector<int> vec; 
   int i;

   // display the original size of vec
   cout << "vector size = " << vec.size() << endl;

   // push 5 values into the vector
   for(i = 0; i < 5; i++) {
      vec.push_back(i);
   }

   // display extended size of vec
   cout << "extended vector size = " << vec.size() << endl;

   // access 5 values from the vector
   for(i = 0; i < 5; i++) {
      cout << "value of vec [" << i << "] = " << vec[i] << endl;
   }

   // use iterator to access the values
   vector<int>::iterator v = vec.begin();
   while( v != vec.end()) {
      cout << "value of v = " << *v << endl;
      v++;
   }

   return 0;
}

When the above code is compiled and executed, it produces the following result −

vector size = 0
extended vector size = 5
value of vec [0] = 0
value of vec [1] = 1
value of vec [2] = 2
value of vec [3] = 3
value of vec [4] = 4
value of v = 0
value of v = 1
value of v = 2
value of v = 3
value of v = 4

Here are following points to be noted related to various functions we used in the above example −

• The push_back( ) member function inserts value at the end of the vector, expanding its size as needed.

• The size( ) function displays the size of the vector.

• The function begin( ) returns an iterator to the start of the vector.

• The function end( ) returns an iterator to the end of the vector.

The C++ Standard Library can be categorized into two parts −

• The Standard Function Library − This library consists of general-purpose,stand-alone functions that are not part of any class. The function library is inherited from C.

• The Object Oriented Class Library − This is a collection of classes and associated functions.

Standard C++ Library incorporates all the Standard C libraries also, with small additions and changes to support type safety.

The Standard Function Library

The standard function library is divided into the following categories −

• I/O,
• String and character handling,
• Mathematical,
• Time, date, and localization,
• Dynamic allocation,
• Miscellaneous,
• Wide-character functions,

The Object Oriented Class Library

Standard C++ Object Oriented Library defines an extensive set of classes that provide support for a number of common activities, including I/O, strings, and numeric processing. This library includes the following −

• The Standard C++ I/O Classes
• The String Class
• The Numeric Classes
• The STL Container Classes
• The STL Algorithms
• The STL Function Objects
• The STL Iterators
• The STL Allocators
• The Localization library
• Exception Handling Classes
• Miscellaneous Support Library

The following resources contain additional information on C++. Please use them to get more in-depth knowledge on this topic.