What does 'plz chk .its not working' mean? As the code you posted is not valid in Oracle, I doubt it shows this terrible text.
Anyway, as PL/SQL code runs on Oracle server, it has no ability to display anything. It may at most fill DBMS_OUTPUT buffer by calling its PUT_LINE method. The client program may display its content then, if it is able and configured to do so.
In SQL*Plus, it is possible after setting SERVEROUTPUT ON.
In SQL Developer, it is available on "DBMS Output" tab after enabled by a button.
The same principle is available in TOAD; the tab may be named slightly differently though.
I have no idea, whether it is implemented in any other client (Forms reports, JDBC, OCCI, ...). It may be done manually by calling DBMS_OUTPUT.GET_LINE You may find more about it in Oracle documentation.
By the way, what are clients you plan to use?
[Add: As PRINTF is supposed to call DBMS_OUTPUT, what is the difference then? Do you suppose, it will display more than DBMS_OUTPUT.PUT_LINE? Anyway, you should call PUT_LINE correctly there. ]