A specific device can have file extensions and .TYPE EAs (Extended Attributes) associated with it. The OS/2 multimedia user can map a file extension or .TYPE EA to a specific device with the Multimedia Setup application located in the Multimedia folder. An OS/2 multimedia subsystem developer writing an installation DLL can map a file extension or .TYPE EA to a device using MCI_SYSINFO_SET_EXTENSIONS or MCI_SYSINFO_SET_TYPES. For an extension or .TYPE EA to be mapped to a device, it must be unique across installation names.
For example, the Multimedia Setup application can be used to associate the WAV extension with the waveaudio01 device. The device can then be opened by passing the name of a data element with a WAV extension as a parameter in the open command to mciSendString. Suppose the following string is passed:
open honk.wav wait
The waveaudio01 device is opened with the data file honk.wav.