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, LP. (The driver name
          corresponds to the device code; in this case, the driver
          name would be SYS$LPDRIVER.)

    c     is the controller designation A through Z; unless UCM
          specifies a different letter, all USB devices are A.

    u     is the unit number (0 through 9999).

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