7800demo.s: It compiles to a 48k file, then when I run it in MESS it just displays the ATARI logo, and then hangs, which, as I suspect, is the result of the infinite loop. That's probably exactly what it should do. 7800sprt.asm: When I copy the code between all headers and all the "word. Start" stuff (which is probably senseless, because at first glance they look the same in both files) into the "demo", it just compiles to an empty .bin. It happens also with the original 7800sprt.asm. Strange it is.