dbms_output.put_line()??

I am trying to run this simple PL/SQL but it doesn't run.

SQL> set serveroutput on;
SQL> create or replace test is begin
SQL> dbms_output.put_line('hello');
SQL> end;
SQL> /
SQL> ** error **unknown dbms_out... command

Why?? Received on Thu Sep 21 2000 - 00:00:00 CDT