---
description: "Learn more about: Window Objects"
title: "Window Objects"
ms.date: "11/04/2016"
helpviewer_keywords: ["objects [MFC], window", "Windows window [MFC]", "MFC, windows", "frame windows [MFC], C++ window objects", "window objects [MFC]", "windows [MFC], C++ window objects", "window messages [MFC]", "HWND", "messages [MFC], Windows", "Visual C++, window objects [MFC]", "HWND, window objects [MFC]"]
ms.assetid: 28b33ce2-af05-4617-9d03-1cb9a02be687
---
# Window Objects

MFC supplies class [CWnd](../mfc/reference/cwnd-class.md) to encapsulate the `HWND` handle of a window. The `CWnd` object is a C++ window object, distinct from the `HWND` that represents a Windows window but containing it. Use `CWnd` to derive your own child window classes, or use one of the many MFC classes derived from `CWnd`. Class `CWnd` is the base class for all windows, including frame windows, dialog boxes, child windows, controls, and control bars such as toolbars. A good understanding of [the relationship between a C++ window object and an HWND](../mfc/relationship-between-a-cpp-window-object-and-an-hwnd.md) is crucial for effective programming with MFC.

MFC provides some default functionality and management of windows, but you can derive your own class from `CWnd` and use its member functions to customize the provided functionality. You can create child windows by constructing a `CWnd` object and calling its [Create](../mfc/reference/cwnd-class.md#create) member function, then customize the child windows using `CWnd` member functions. You can embed objects derived from [CView](../mfc/reference/cview-class.md), such as form views or tree views, in a frame window. And you can support multiple views of your documents via splitter panes, supplied by class [CSplitterWnd](../mfc/reference/csplitterwnd-class.md).

Each object derived from class `CWnd` contains a message map, through which you can map Windows messages or command IDs to your own handlers.

The general literature on programming for Windows is a good resource for learning how to use the `CWnd` member functions, which encapsulate the `HWND` APIs.

## Functions for Operating On a CWnd

`CWnd` and its [derived window classes](../mfc/derived-window-classes.md) provide constructors, destructors, and member functions to initialize the object, create the underlying Windows structures, and access the encapsulated `HWND`. `CWnd` also provides member functions that encapsulate Windows APIs for sending messages, accessing the window's state, converting coordinates, updating, scrolling, accessing the Clipboard, and many other tasks. Most Windows window-management APIs that take an `HWND` argument are encapsulated as member functions of `CWnd`. The names of the functions and their parameters are preserved in the `CWnd` member function. For details about the Windows APIs encapsulated by `CWnd`, see class [CWnd](../mfc/reference/cwnd-class.md).

## CWnd and Windows Messages

One of the primary purposes of `CWnd` is to provide an interface for handling Windows messages, such as WM_PAINT or WM_MOUSEMOVE. Many of the member functions of `CWnd` are handlers for standard messages — those beginning with the identifier **afx_msg** and the prefix "On," such as `OnPaint` and `OnMouseMove`. [Message Handling and Mapping](../mfc/message-handling-and-mapping.md) covers messages and message handling in detail. The information there applies equally to the framework's windows and those that you create yourself for special purposes.

### What do you want to know more about

- [The relationship between a C++ window object and an HWND](../mfc/relationship-between-a-cpp-window-object-and-an-hwnd.md)

- [Derived window classes](../mfc/derived-window-classes.md)

- [Creating windows](../mfc/creating-windows.md)

- [Destroying window objects](../mfc/destroying-window-objects.md)

- [Detaching a CWnd from Its HWND](../mfc/detaching-a-cwnd-from-its-hwnd.md)

- [Working with window objects](../mfc/working-with-window-objects.md)

- [Device contexts](../mfc/device-contexts.md): objects that make Windows drawing device independent

- [Graphic objects](../mfc/graphic-objects.md): pens, brushes, fonts, bitmaps, palettes, regions

## See also

[Windows](../mfc/windows.md)