The Complete Guide to Mastering MFC Interview Questions

Landing a job as a C++ developer often requires excelling at MFC interview questions The Microsoft Foundation Class Library (MFC) is a popular C++ framework for building Windows applications Having in-depth knowledge of MFC is a must for developers working on Windows platforms,

In this comprehensive guide, I will share some of the most common and important MFC interview questions you need to master. Whether you are prepping for your next technical interview or brushing up on concepts, these questions will enhance your understanding of MFC

Overview of MFC

Let’s start with a quick primer on MFC MFC provides a object-oriented wrapper over the Windows API to make Windows programming in C++ easier It encapsulates many complex portions of Win32 development like window creation, message handling, and GUI controls into C++ classes.

Some key capabilities offered by MFC include:

• Simplified message mapping using macros like ON_COMMAND and ON_UPDATE_COMMAND_UI.
• Document/View architecture for separating data and UI concerns.
• Serialization framework for saving/loading objects.
• Support for GDI+ graphics, common controls like toolbar, and ActiveX.
• Database classes for interacting with ODBC/DAO data sources.

Now that you have an overview of MFC, let’s dive into some common interview questions on this technology.

Common MFC Interview Questions

Here are some of the most popular MFC interview questions that test your knowledge of the framework:

Q1. Explain message handling in MFC.

Messages are central to Windows’ event-driven programming model. MFC provides macros like ON_COMMAND and ON_NOTIFY to map messages to class member functions for handling. This message map defines the routing for messages to appropriate handlers.

The message map is declared using BEGIN_MESSAGE_MAP and END_MESSAGE_MAP in the class declaration. Message handlers are prototyped as ClassName::HandlerName(WPARAM, LPARAM). Parameters like command ID or control ID can be extracted from WPARAM and LPARAM.

Q2. What is the role of CWinApp class in an MFC application?

CWinApp class encapsulates the application itself. Each MFC app must instantiate one CWinApp derived object. Key responsibilities include:

• Initializes Windows instance (hInstance)
• Processes command line arguments
• Enters main message loop
• Manages application lifetime and resources
• Routes messages to appropriate handlers

We override CWinApp methods like InitInstance() and ExitInstance() to customize initialization and cleanup.

Q3. How is document/view architecture used in MFC?

The document/view architecture separates data management from UI display. The document (CDocument) represents underlying data model and business logic. The view (CView) handles presentation layer and user interactions.

This promotes separation of concerns and modularity. Multiple views can display the same document. Views can be easily changed without affecting document implementation. The framework coordinates between documents and views automatically.

Q4. What are the main steps for serialization in MFC?

To enable serialization in MFC class:

1. Derive from CObject.
2. Use DECLARE_SERIAL macro.
3. Implement Serialize() function.
4. Call archive object’s operator<< and operator>>.

The Serialize() function is invoked automatically when archiving objects. We can override it to define custom serialization behavior.

Q5. How are resources handled in MFC?

MFC uses Resource Management Objects (RMOs) to encapsulate resources like fonts, brushes, bitmaps etc. These RMOs tie into Windows GDI system for efficient resource management.

Some examples:

• CFont – Font resources
• CBrush – Brush resources
• CBitmap – Bitmap resources

RMOs automatically clean up resources when they go out of scope, preventing leaks.

Q6. What are some widely used MFC classes?

Some commonly used MFC classes include:

• CWinApp – Base application class.
• CDocument – Encapsulates document data.
• CView – Displays document data.
• CWnd – Provides core window functionality.
• CFrameWnd – Implements application main window.
• CDialog – Dialog box windows.
• CComboBox – Combobox control.
• CListCtrl – List view control.
• COleObjectFactory – For OLE embedding.

Q7. How can you implement a splitter window in MFC?

We can use CSplitterWnd class to create splitter windows in MFC. Key steps:

1. Add CSplitterWnd member to main frame class.
2. Call Create() in OnCreate() handler passing parent window pointer.
3. Call CreateView() to create splitter panes (pass CRuntimeClass of view).
4. Adjust pane sizes with SetRowInfo() or SetColumnInfo().

The splitter handles pane dragging/resizing internally. We can control orientation, appearance and initial pane sizes.

Q8. What are the advantages of using MFC?

Some notable advantages of using MFC include:

• Object-oriented abstraction over Windows API.
• Simplified message mapping and event handling.
• Document/View architecture promotes loose coupling.
• Serialization framework for easy object persistence.
• Extensive set of reusable classes like dialogs, controls etc.
• Debugging support is better compared to raw Win32.
• Improved type safety over plain C Win32 programming.

Q9. What are some limitations of MFC?

Some limitations associated with MFC:

• Steep learning curve for beginners.
• Increased complexity due to framework overhead.
• Uses outdated C++ features instead of modern C++.
• Tight coupling makes unit testing difficult.
• Not suitable for cross-platform development.
• Limited official documentation and samples.

Q10. How can you improve performance when using MFC?

Some tips for boosting performance in MFC apps:

• Avoid unnecessary memory allocations/deallocations.
• Create GDI objects once and reuse.
• Load bitmaps/resources once at startup.
• Reduce screen redraws using BeginDeferWindowPos().
• Use reference counted objects like CString instead of raw char arrays.
• Profile bottlenecks using Visual Studio’s Diagnostic Tools.
• Optimize slow drawing code in views using Double Buffering.

Mastering these MFC interview questions displays your expertise in optimizing Windows GUI applications with MFC framework. Practice mock interviews and analyze areas needing improvement. With thorough preparation on MFC, you can ace your next technical interview!