HWNDs

A HWND, or Handle to a Window, is a fundamental concept in Microsoft Windows programming. It serves as an opaque identifier, a unique tag assigned by the operating system to each window or control that is created. Think of it as a reference number that the system uses internally to manage and interact with these visual elements.

When an application creates a window, such as a main application window, a dialog box, a button, or a text edit field, the Windows operating system allocates a specific HWND for it. This handle is not a pointer to the window's memory directly, but rather a value that the operating system can use to look up the window's associated data.

Applications use HWNDs extensively to perform operations on windows. For example, to send a message to a specific window, to change its size or position, to set its title, or to determine if it's visible, an application must pass its HWND to the relevant Windows API (Application Programming Interface) functions. Without an HWND, the operating system wouldn't know which specific window to target. While programmers work with HWNDs, they are largely an internal mechanism for the Windows system to manage its graphical user interface.