Write PL/SQL program？

DECLARE
--Declare variables num, sum_of_digits and remainder of datatype Integer 
num  INTEGER; 
sum_of_digits INTEGER; 
remainder  INTEGER; 
BEGIN
num := 123456; 
sum_of_digits := 0;
-- Find the sum of digits until original number doesnt become null 
WHILE num <> 0 LOOP 
 remainder := MOD(num, 10); 
 sum_of_digits := sum_of_digits + remainder; 
 num := TRUNC(num / 10); 
END LOOP; 
dbms_output.PUT_LINE('Sum of digits is '|| sum_of_digits); 
END;