3. What is Pure Virtual Function? Why and when it is used ?

Ans:

The abstract class whose pure virtual method has to be implemented by all the classes which derive on these. Otherwise it would result in a compilation error. This construct should be used when one wants to ensure that all the derived classes implement the method defined as pure virtual in base class

Ex Q1: What is problem with Runtime type identification?

Ans:

The run time type identification comes at a cost of performance penalty. Compiler maintains the class.

Ex Q2: Can inline functions have a recursion?

Ans:
No.
Syntax wise It is allowed. But then the function is no longer Inline. As the compiler will never know how deep the recursion is at compilation time.

Ex Q3: How Virtual functions call up is maintained?

Ans:
Through Look up tables added by the compile to every class image. This also leads to performance penalty.

Ex Q4: How do you link a C++ program to C functions?

Ans:
By using the extern "C" linkage specification around the C function declarations. Programmers should know about mangled function names and type-safe linkages. Then they should explain how the extern "C" linkage specification statement turns that feature off during compilation so that the linker properly links function calls to C functions.

Ex Q5: Name some pure object oriented languages?

Ans:

Ø    Smalltalk,
Ø    Java,
Ø    Eiffel, 
Ø    Sather.