CREATE TABLE departments (department_id, department_name, manager_id, location_id) AS
SELECT 100, 'Finance', 108,  1700 FROM DUAL UNION ALL
SELECT 120, 'Treasury', NULL,  1700 FROM DUAL;

BEGIN 
  FOR rec in (SELECT * from departments)
loop
dbms_output.put_line(rec.department_id||' '||rec.department_name||' '||NVL(rec.manager_id,'N/A')||' '||rec.location_id);
  end loop;
END;

orclz> ed
Wrote file afiedt.buf

  1  BEGIN
  2    FOR rec in (SELECT * from departments)
  3  loop
  4  dbms_output.put_line(rec.department_id||' '||rec.department_name||' '||NVL(to_char(rec.manager_id),'N/A')||' '||rec.location_id);
  5    end loop;
  6* END;
orclz> /
100 Finance 108 1700
120 Treasury N/A 1700

PL/SQL procedure successfully completed.