This is the MIDI Associate Control Block data structure.
typedef struct _ACB_MISH { ULONG ulACBLen; /* Structure length. */ ULONG ulObjType; /* Object type. */ HSTREAM hstreamDefault; /* Default HSTREAM. */ ULONG ulDeviceTypeID; /* Device type ID. */ ULONG ulpMapperPorts; /* Pointer to mapper port table. */ ULONG ulNumInStreams; /* Number of input streams. */ HSTREAM hstreamIn[MAX_PORTS]; /* Input stream array. */ ULONG ulNumOutStreams; /* Index to output array. */ HSTREAM hstreamOut[MAX_PORTS]; /* Output stream array. */ } ACB_MISH; typedef ACB _ MISH * PACB _ MISH ;