I think it is very simple, and I have forgot the
detail. you can look up int21h spec.
before and after you write a charactor, you just
call change charactor mode function by int21H.
there is a byte parameter high four bits are
background and low four bits are forground of
charactor. I just remember these thing, I think
I have not do these job for five years. I'm sorry.
master jansenzhu.