The following code illustrates how to determine the number of waveform devices installed.

   #define  RETBUFSIZE 128

   MCI_SYSINFO_PARMS  SysInfo;
   CHAR  SysInfoRet[RETBUFSIZE];
                                       /*  Set unused fields to zero.  */
   memset(&SysInfo, 0x00, sizeof(MCI_SYSINFO_PARMS));
   SysInfo.usDeviceType  = MCI_DEVTYPE_WAVEFORM_AUDIO;
                                       /* Device type                  */
   SysInfo.pszReturn = (PSZ) &SysInfoRet;
                                       /* Pointer to return buffer     */
   SysInfo.ulRetSize = RETBUFSIZE;

           /* Determine the number of waveform audio devices installed */

   mciSendCommand (0,                  /* Don't know device ID yet     */
    MCI_SYSINFO,                       /* MCI sysinfo message          */
    MCI_SYSINFO_QUANTITY | MCI_WAIT,
                                       /* Flags for this message       */
    (PVOID)&SysInfo,                   /* Data structure               */
    0);                                /* No user parm                 */

           /* SysInfoRet now contains number of wave audio devices.    */