SQL & PL/SQL

CREATE OR REPLACE PROCEDURE proc_test1 IS
BEGIN
IF (TRUE AND NULL ) THEN
DBMS_OUTPUT.PUT_LINE ('first condition ');
ELSIF NOT(TRUE AND NULL ) THEN
DBMS_OUTPUT.PUT_LINE ('second condition ');
ELSIF (TRUE AND TRUE ) THEN
DBMS_OUTPUT.PUT_LINE ('third condition ');
END IF;
END proc_test1;

hi xprt..

the second condition is true...rite
NOT(TRUE AND NULL ) ===>>> true
but m not getting it...the output as "second conditon"

but only third condition...

why?... m i missing something..??

Regards...

Dichan