Control code handling for screen output is complete. Now, all control codes are silently handled as part of screen_write_string. There is an easy way to add a hook later for raw vs. cooked screen mode. That would allow selective handlaing of control code processing. I've also managed to squeeze out 26 bytes from that function. Nothing exciting, but it makes me happy, and I suppose every byte counts.
The plan from here is to get printf finished, and move on to other stuff.