What is the datatype and precision of Oracle NULL column?

Do you know the datatype and precision of Oracle Null column?
It is Varchar2 with 0 as the precision.

SQL> create view test_vw as select null x from dual;

View created.


SQL> desc test_vw
 Name                                      Null?    Type
 ----------------------------------------  -------  --------
 X                                                  VARCHAR2

  1  select table_name, column_name, data_type, data_length
  2  from   user_tab_columns
  3* where  table_name ='TEST_VW'
SQL> /

TABLE_NAME      COLUMN_NAME     DATA_TYPE       DATA_LENGTH
--------------- --------------- --------------- -----------
TEST_VW         X               VARCHAR2                  0
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