Write a PL/SQL block to describe the usage of NULL values in equal comparison, unequal comparison and NOT NULL equals NULL comparison

DECLARE
  m NUMBER := 7;
  n NUMBER := NULL;

  o NUMBER := NULL;
  p NUMBER := NULL;

  q    INTEGER := 4;
  r    INTEGER := 9;

 large INTEGER;

----------------------------------
BEGIN
  IF m != n THEN  -- yields NULL, not TRUE
    DBMS_OUTPUT.PUT_LINE('m != n');  -- not run
  ELSIF m = n THEN -- also yields NULL
    DBMS_OUTPUT.PUT_LINE('m = n');
  ELSE
    DBMS_OUTPUT.PUT_LINE
      ('Can not say whether m and n are equal or not.');
  END IF;

-----------------------------------
  IF o = p THEN  -- yields NULL, not TRUE
    DBMS_OUTPUT.PUT_LINE('o = p');  -- not run
  ELSIF o != p THEN  -- yields NULL, not TRUE
    DBMS_OUTPUT.PUT_LINE('o != p');  -- not run
  ELSE
    DBMS_OUTPUT.PUT_LINE('Can not say whether two NULLs are equal');
  END IF;
--------------------------------------
  IF (q > r)       -- If q or r is NULL, then (q > r) is NULL
    THEN large  := q;  -- run if (q > r) is TRUE
    ELSE large  := r;  -- run if (q > r) is FALSE or NULL
DBMS_OUTPUT.PUT_LINE('The value of large : '||large);
  END IF;
  
  IF NOT (q > r)   -- If q or r is NULL, then NOT (q > r) is NULL
    THEN large  := r;  -- run if NOT (q > r) is TRUE
    ELSE large  := q;  -- run if NOT (q > r) is FALSE or NULL
DBMS_OUTPUT.PUT_LINE('The value of large : '||large);
  END IF;

END;
/