The reader of any root directory is where any other branch directories. The root directory of the hard disk of a computer is the C:. There is no specific designation for flash drives. A, B and C hard.
(And therefore root directories) are designated by the computer. A and B drives are always saved to floppy drives and drive C is recorded for the primary hard drive of a computer. After that, the drive letters are not consistent from computer to computer.
Additional drive letters
Any disk drive in the primary drive is assigned to D, and so on. Optical disc drives are next, followed by USB devices. Thus, on a computer with a hard drive and a DVD burner connected via 3.0 Powered USB hub, the root of the USB drive will be E. If the computer has two hard drives, or additional disk drive and the USB flash drive will be assigned F.
Whatever the root drive of your USB flash drive, it is important rarely. It will work the same way regardless of its drive designation. The only time it might matter is that if something is installed in the USB drive and that drive letters change with the addition of new hardware. If the operating system provides a program to be in a car, and it is not, which can cause errors and the program will probably not function properly.