ucb_addr

    OpenVMS usage address
    type          quadword (unsigned)
    access        read only
    mechanism     by value
    System address of the Unit Control Block of the device.

 name_buf

    OpenVMS usage char_string
    type          character string
    access        write only
    mechanism     by reference
    Address of buffer to receive device name.

 name_len

    OpenVMS usage longword_unsigned
    type          longword (unsigned)
    access        read only
    mechanism     by value
    Length of buffer to receive device name.