What is data abstraction and data hiding concept in c plus plus?

Answer 1

Data abstraction refers to the way users can interact with class data without needing to know how that data is stored or manipulated by the class. For instance, a class method such as int GetValue() will obviously return an integer, but the value from which that integer comes need not be an integer (it could be a float) or it could be calculated on the fly based upon other internal data members. The point is that it is irrelevant to the user how the value was obtained.

Although many will tell you that data hiding (or information hiding) refers to the way in which classes "hide" private or protected information within themselves, that is not the case at all. What they are really referring to is data abstraction, as outlined above.

Note that private or protected access only limits access to the information, it does not physically hide it in any way, shape or form. That is, a private data member can be thought of as being placed in a virtual cage: your compiler can see the member exists, but unless your code is a member of the class then you cannot access it, and the compiler will tell you as much. The following example demonstrates the concept:

class a {

private: int data; };

class b: public a {

void foo { a::data = 5; }

}

In the above example, a::data is clearly visible and nothing can physically prevent you from writing the code shown above. Your compiler will obviously tell you that a::data is not accessible from b, but in order to do so the compiler must know that a::data exists. And if the compiler knows it exists, then so do you, even if the declaration appears in another file, thus the data cannot be said to be hidden.

The true meaning of data hiding is the way in which a binary executable or library hides information from the user. That is, the information is hidden through obfuscation. A skilled disassembler can still reveal the internal details so it is not completely hidden, but it would be difficult, if not impossible, even for a skilled disassembler, to reconstruct the original classes from which that data was produced, unless they have access to the declaration.