I got to try out the point of compiling and trying out your programs now. `ex8`, `ex9` and `ex10` all segfault here.
Some time ago I was at a wedding, and I was terribly bored, until I found out that the guy to my left was writing washing machine software in assembly. In a way it seems awfully primitive, e.g. your `ex11.subx` is 350 lines long and prints out `.......` but I guess in certain systems it's the only option, and what's underneath it all in any system.