## MMPM/2 Device Driver Reference

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### MCI_AUDIO_INIT Field - ulVersionLevel

ulVersionLevel (ULONG) Specifies the audio device driver version. As audio device drivers evolve, some changes are sure to occur. The ulVersionLevel field is used to allow new functions to be added to audio device drivers without losing compatibility with existing applications.

When an application calls AUDIO_INIT, it specifies the version level of the requested device driver. The audio device driver compares its version level with that passed by the application and ensures that they are compatible. If the device driver is an earlier version than that required by the application, it returns an error. If the version level of the device driver is newer than the application, the driver ensures that calls from the application are handled in a manner consistent with the version level of the application.

The value specified in ulVersionLevel is the binary-coded decimal representation of the version and build level. For example, Version 1.0 Build 15 is coded 0x01000015. The high-order byte is the version, the next byte is the revision number, and the least significant two bytes are the build number.