What is the main advantage ATL offers over MFC when used to develop ActiveX controls?

The main advantage ATL offers ActiveX development is that ATL can create controls that
have no dependencies. Properly written, an ActiveX control created from ATL requires
neither MFC nor the C run-time library, ensuring that only the control's executable file
needs to be downloaded from a Web page. ActiveX controls created using MFC can
execute only when MFC42.dll and MSVCRT.dll are present on a system.

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Explain Polymorphism and Flavors of Polymorphism...

Polymorphism is the ability of different objects to react in an individual manner to the same message. This notion was imported from natural languages. For example, the verb "to close" means different things when applied to different objects. Closing a door, closing a bank account, or closing a program's window are all different actions; their exact meaning is determined by the object on which the action is performed. Most object-oriented languages implement polymorphism only in the form of virtual functions. But C++ has two more mechanisms of static (meaning: compile-time) polymorphism: Operator overloading. Applying the += operator to integers or string objects, for example, is interpreted by each of these objects in an individual manner. Obviously, the underlying implementation of += differs in every type. Yet, intuitively, we can predict what results are. Templates. A vector of integers, for example, reacts differently from a vector of string objects when it receives ...

• Why might you need exception handling be used in the constructor when memory allocation is involved?

Your first reaction should be: "Never use memory allocation in the constructor." Create a separate initialization function to do the job. You cannot return from the constructor and this is the reason you may have to use exception handling mechanism to process the memory allocation errors. You should clean up whatever objects and memory allocations you have made prior to throwing the exception, but throwing an exception from constructor may be tricky, because memory has already been allocated and there is no simple way to clean up the memory within the constructor.

• What are the advantage and disadvantage of using exception handling?

Disadvantage is a slight overhead imposed by implementing of exception handling mechanism. Advantage is "bullet-proof" program. With exception handling you have a mechanism which guarantee you control over program behavior despite the errors that might be in your program. With try-catch block you control not even given block of the program, but also all underlying function calls.

VC++ - Visual C++ - Microsoft Visual C++ Interview Questions And Answers

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