Difference Between Objects and Classes

Objects vs Classes

Objects and classes are used in object oriented programming languages. All object oriented programming languages such as C++, Java, .NET and others, employs objects and classes.

Objects

An object is defined as any entity that can be utilized by using commands in a programming language. Object can be a variable, value, data structure or a function. In object oriented environment, object is referred to as instance of a class. Objects and classes are closely related to each other. In real world, the objects are your TV, bicycle, desk and other entities. Methods are used to access the objects of a class. All the interaction is done through the object’s methods. This is known as data encapsulation. The objects are also used for data or code hiding.

A number of benefits are provided by the objects when they are used in the code:

• Ease of debugging – The object can be easily removed from the code if there is some problem due to it. A different object can be plugged in as a replacement of the former one.

• Information hiding – The code or internal implementation is hidden from the users when interaction is done through object’s methods.

• Reuse of code – if an object or code is written by some other programmer then you can also use that object in your program. In this way, objects are highly reusable. This allows experts to debug, implement task specific and complex objects that can be used in your own code.

• Modularity – You can write as well as maintain the source codes of objects in an independent manner. This provides modular approach to programming.

Classes

A class is a concept used in object oriented programming languages such as C++, PHP, and JAVA etc. Apart from holding data, a class is also used to hold functions. An object is an instant of a class. In case of variables, the type is the class whereas the variable is the object. The keyword “class” is used to declare a class and it has the following format:

class CLASS_NAME

{

AccessSpecifier1:

Member-1;

AccessSpecifier2:

Member-2;

} OBJECT_NAMES;

Here, the valid identifier is CLASS_NAME and the names for objects are represented by OBJECT_NAMES. The benefit of objects include information hiding, modularity, ease in debugging and reuse of the code. The body contains the members that can be functions or data declarations. The keywords for access specifiers are public, protected or private.

• The public members can be accessed anywhere.

• The protected members can be accessed within same classes or from friend classes.

• The private members can be accessed only within the same class.

By default, the access is private when the class keyword is used. A class can hold both data and functions.

Objects vs. Classes

• An object is an instant of a class. A class is used to hold data and functions.

• When a class is declared, no memory is allocated but when the object of the class is declared, memory is allocated. So, class is just a template.

• An object can only be created if the class is already declared otherwise it is not possible