Specifies a volume to be used as the default volume for all
 succeeding commands.  If the USE command is not used, then
 the default volume is SYS$DISK.

 FORMAT:
 USE <device>

 Where <device> is some device spec. or a logical name that
 translates to a device spec.  The device must have some
 media MOUNTed on it.

 EXAMPLE:
  USE DBA1: