What is OOP ? Basic Concepts.

What is OOP?
Object oriented programming is a type of programming paradigm based around programming classes and instances of classes called objects. These can be objects that appear on the screen (e.g., pictures, textboxes, etc.) or are part of the programming (e.g. actors, connections, particles, etc.)

What is an Object?
An object is merely a collection of related information and functionality. An object can be something that has a corresponding real-world manifestation (such as an employee object), something that has some virtual meaning (such as a window on the screen), or just some convenient abstraction within a program (a list of work to be done, for example).

An object is composed of the data that describes the object and the operations that can be performed on the object. Information stored in an employee object, for example, might be various identification information (name, address), work information (job title, salary), and so on. The operations performed might include creating an employee paycheck or promoting an employee.

When creating an object-oriented design, the first step is to determine what the objects are. When dealing with real-life objects, this is often straightforward, but when dealing with the virtual world, the boundaries become less clear. That’s where the art of good design shows up, and it’s why good architects are in such demand.

 What is a Class?
Structures are very similar to Classes in that they collect data together. However, classes extend this idea and are made from two different things:
Attributes - things that the object stores data in, generally variables.
Methods - Functions and Procedures attached to an Object and allowing the object to perform actions

Let's take a look at the following example:

class car
  private maxSpeed as integer
  public fuel as integer
  public sub setSpeed(byVal s as integer)
    maxSpeed = s
  end sub
  public function getSpeed() as integer
    return maxSpeed
  end function
  public sub refuel(byVal x as integer)
    console.writeline("pumping gas!")
    fuel = fuel + x
  end sub
  public function getFuel() as integer
    return fuel
  end function
  public sub drive()
    fuel = fuel - 1
  end sub
end class 
:

two attributes: maxSpeed, fuel
four methods
three procedures: setSpeed, refuel, drive
one function: getSpeed
  Attributes

These store information about the object. In the example above we store the fuel and maxSpeed. The attributes are attached to the classes, and if there are several instances (objects) of the classes then each will store its own version of these variables. Note that instead of the usual dim, there is the word private or public, we'll cover that in the encapsulation section.


Methods

Unlike structures, OOP allows you to attach functions and procedures to your code. This means that not only can you store details about you car (the attributes), you can also allow for sub routines such as drive() and refuel, which are attached to each class.