[DEPT COURSE# PRE_ PRE_COURSE#
---- ---------- ---- -----------
CS 432 CS 240
CS 532 CS 432
Math 314 Math 221
CS 432 Math 314
CS 552 CS 240

5. Write a procedure in your package that, for a given course (with dept_code and course# as parameters), can return all its prerequisite courses (show dept_code and course# together as in CS532), including both direct and indirect prerequisite courses.
If course C1 has course C2 as a prerequisite, C2 is a direct prerequisite.
If C2 has course C3 has a prerequisite, then C3 is an indirect prerequisite.
Indirect prerequisites can be more than two levels away.

No answer?
Anyway thanks . I solve it. and I will post my solution for general benefit.
and it's working.

set serveroutput on set echo on create or replace procedure show_pre
(deptc in courses.dept_code%type,cour# in courses.course#%type)
is 
cursor c2 is
select (p1.pre_dept_code||p1.pre_course#) as CID
from prerequisites p1 where p1.dept_code=deptc and p1.course#=cour#;

begin for c2_rec in c2 loop
 dbms_output.put_line(c2_rec.CID);


declare
	cursor c3 is
       	select (p2.pre_dept_code||p2.pre_course#) as CID
       	from prerequisites p2 where (p2.dept_code||p2.course#)=c2_rec.CID;	
begin for c3_rec in c3 loop
	dbms_output.put_line(c3_rec.CID);
	end loop;
end;

end loop;
end;
/
show errors

exec show_pre('CS',432);

Salam Alakoum
Samer