1 NU
 This command restores te UIC, protecction, and privileges to the state
 previous to an earlier SU command.  The top entry in the stack is
 removed and used to set the UIC, protection, and privileges.

 If the stack is empty, all privileges are removed.

 Format:

        $ NU :== $disk:[directory]NU
        $ NU [/qualifiers]

2 qualifiers
/HOME

 This qualifier causes the entire stack of states to be removed.  This
 returns the UIC, protection, and privileges to the state they were in
 before the first SU command given that is still on the stack.

