Hallloo,
 
I  search command print to screen in acrobat reader, where this command i use:
 
Create Trigger tr_xx on t_coba
for before insert as
begin
    .....
    printf('STOCK') 
end

I've been working in Delphi for quite awhile now, so my C is a tad rusty, but unless I'm really out of touch, I believe that printf is a C language function.  I don't think you can make use of it from within a stored procedure/Trigger/Generator, unless you "wrap" it in a UDF.