In addition to receiving messages, drivers must notify clients when certain events occur. Waveform input drivers notify clients by sending one of the following messages using the DriverCallback function.
| WIM_CLOSE | Notifies a client application when a device is closed. |
| WIM_DATA | Notifies a client application when the driver is finished with a data buffer and is returning it to the client. |
| WIM_OPEN | Notifies a client application when a device is opened. |