VMS Help SET, DEFAULT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Sets your default device and directory specifications. The new
    default is applied to all subsequent file specifications that do
    not explicitly include a device or directory name.

    When you change the default device assignment, the system equates
    the specified device with the logical name SYS$DISK.

    Format

      SET DEFAULT  [device-name[:]][directory-spec]

  Additional Information (explode) :

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• Examples