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Mounting Devices and Logical Drives

RTFiles-32 must assign drive letters and mount all drives to be used. Mounting involves determining the file system type (FAT-12/16/32/ISO 9660/exFAT), the drive's size, etc. RTFiles-32 mounts drives in an MS-DOS and Windows compatible order to achieve the same drive letter assignment. During the first RTFiles-32 API call which needs access to a drive, drive letters are assigned according to the rules given below. Please note that removable devices are not accessed until they are actually needed. However, the partition tables of all non-removable hard disks are read at program startup.

• Drive letters are assigned to devices in the order they appear in the device list.
• Drive letter assignment starts with letter 'A'. When a hard disk is mounted, the driver letter is set to 'C' or higher.
• Floppy disks and non-removable hard disks are mounted before removable hard disks.
• A single drive letter is reserved for every floppy and removable hard disk, even if they are not present or never accessed. For non-removable hard disks, drive letters are only assigned for existing FAT partitions.
• For non-removable hard disks, drive letters are assigned in this order:
  • the first primary partition of all devices, then
  • all logical drives in extended partitions of all drives, then
  • all other primary partitions of all drives.

While this mounting algorithm may seem complicated, it corresponds to the method used by MS-DOS and results in the same drive letter assignment. Please note that you can utilize a much simpler scheme by setting flag RTF_DEVICE_MOUNT_CONTIGUOUS for all devices in the device list. If used, all partitions of a device will be assigned consecutive drive letters.

The only drive letters automatically skipped by RTFiles-32 are 'A' and 'B' if no or only one floppy disk is present before the first hard disk is found. However, you can force RTFiles-32 not to use drive letters by inserting dummy devices into the device list using the RTFDrvNULL driver.

RTFiles-32 in Embedded Applications

RTFiles-32 APIs

RTFiles-32 Buffers