Abstraction is the process or method of gaining the information. While encapsulation is the process or method to contain the information. In abstraction, problems are solved at the design or interface level. While in encapsulation, problems are solved at the implementation level.
Encapsulation implies the hiding of an object's data because any procedures can operate on public data. Information hiding: abstracting things, such as an object's implementation i.e. an object's data, the implementation of its procedures, and the classes of the parameters and return values of its procedures.
Abstraction focuses on outside viewing, for example, shifting the car. Encapsulation focuses on internal working or inner viewing, for example, the production of the car. Abstraction is supported in Java with the interface and the abstract class.
Go to the source! Grady Booch says (in Object Oriented Analysis and Design, page 49, second edition):
Abstraction and encapsulation are complementary concepts: abstraction focuses on the observable behavior of an object... encapsulation focuses upon the implementation that gives rise to this behavior... encapsulation is most often achieved through information hiding, which is the process of hiding all of the secrets of object that do not contribute to its essential characteristics.
In other words: abstraction = the object externally; encapsulation (achieved through information hiding) = the object internally,
Example:
In the .NET Framework, the System.Text.StringBuilder
class provides an abstraction over a string buffer. This buffer abstraction lets you work with the buffer without regard for its implementation. Thus, you're able to append strings to the buffer without regard for how the StringBuilder
internally keeps track of things such the pointer to the buffer and managing memory when the buffer gets full (which it does with encapsulation via information hiding).
rp
The OP updated his question with several citations that he had found, namely in an article by Edward V. Berard titled, "Abstraction, Encapsulation, and Information Hiding". I am re-posting a slightly expanded and reformatted version of the OP's update, since it should be an answer in its own right.
(All citations are taken from the article mentioned above.)
Abstraction:
"One point of confusion regarding abstraction is its use as both process and an entity. Abstraction, as a process, denotes the extracting of the essential details about an item, or a group of items, while ignoring the inessential details. Abstraction, as an entity, denotes a model, a view, or some other focused representation for an actual item."
Information Hiding:
"Its interface or definition was chosen to reveal as little as possible about its inner workings." — [Parnas, 1972b]
"Abstraction can be […] used as a technique for identifying which information should be hidden."
"Confusion can occur when people fail to distinguish between the hiding of information, and a technique (e.g., abstraction) that is used to help identify which information is to be hidden."
Encapsulation:
"It […] refers to building a capsule, in the case a conceptual barrier, around some collection of things." — [Wirfs-Brock et al, 1990]
"As a process, encapsulation means the act of enclosing one or more items within a […] container. Encapsulation, as an entity, refers to a package or an enclosure that holds (contains, encloses) one or more items."
"If encapsulation was 'the same thing as information hiding,' then one might make the argument that 'everything that was encapsulated was also hidden.' This is obviously not true."
Conclusion:
"Abstraction, information hiding, and encapsulation are very different, but highly-related, concepts. One could argue that abstraction is a technique that help us identify which specific information should be visible, and which information should be hidden. Encapsulation is then the technique for packaging the information in such a way as to hide what should be hidden, and make visible what is intended to be visible."
Abstraction
is hiding the implementation details by providing a layer over the basic functionality.
Information Hiding
is hiding the data which is being affected by that implementation. Use of private
and public
comes under this. For example, hiding the variables of the classes.
Encapsulation
is just putting all similar data and functions into a group e.g Class
in programming; Packet
in networking.
Through the use of Classes, we implement all three concepts - Abstraction
, Information Hiding
and Encapsulation
Please don't complicate simple concepts.
Encapsulation : Wrapping up of data and methods into a single unit is Encapsulation (e.g. Class)
Abstraction : It is an act of representing only the essential things without including background details. (e.g. Interface)
FOR EXAMPLES AND MORE INFO GOTO :
http://thecodekey.com/C_VB_Codes/Encapsulation.aspx
http://thecodekey.com/C_VB_Codes/Abstraction.aspx
Approved definitions here
P.S.: I also remember the definition from a book named C++ by Sumita Arora which we read in 11th class ;)
The meaning of abstraction given by the Oxford English Dictionary (OED) closest to the meaning intended here is 'The act of separating in thought'. A better definition might be 'Representing the essential features of something without including background or inessential detail.'
Information hiding is the principle that users of a software component (such as a class) need to know only the essential details of how to initialize and access the component, and do not need to know the details of the implementation.
Edit: I seems to me that abstraction is the process of deciding which parts of the implementation that should be hidden.
So its not abstraction VERSUS information hiding. It's information hiding VIA abstraction.
Abstraction
Abstraction is an act of representing essentail details without including the background details. A abstract class have only method signatures and implementing class can have its own implementation, in this way the complex details will be hidden from the user. Abstraction focuses on the outside view. In otherwords, Abstraction is sepration of interfaces from the actual implementation.
Encapsulation
Encapsulation explains binding the data members and methods into a single unit. Information hiding is the main purpose of encapsulation. Encapsulation is acheived by using access specifiers like private, public, protected. Class member variables are made private so that they cann't be accessible directly to outside world. Encapsulation focuses on the inner view. In otherwords, Encapsulation is a technique used to protect the information in an object from the other object.
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