The "IME" window class is a predefined system global class that defines the appearance and behavior of the standard IME windows. The class is similar to common control classes in that you create a window of this class by using the CreateWindowEx function. Like static controls, an IME window does not respond to user input by itself. Instead, it notifies the IME of user input actions and processes control messages sent to it by the IME or applications to carry out a response to the user action.
IME-aware applications sometimes create their own IME windows using the IME class. This allows the application to take advantage of the default processing of the IME window while having control of the positioning of the window.