device-name:

    The name of the device whose characteristics are to be added. The
    device name has the form ddcu

    where:

    dd    is the device code - for example, OH (The driver name
          corresponds to the device code; in this case, the driver
          name would be SYS$OHCIDRIVER.  Supported devices are OH,
           EH, and UH.

    c     is the controller designation A through Z;

    u     is the unit number for USB controllers, which is always 0.

    OpenVMS device names consist of the two-character device
    code, followed by the controller designation, the unit number
    (which can be 1 to 4 characters), and a colon (:).