Next to being an alternative language, ALT is a also a purely functional programming language but then without functions!
One could argue that ALT is one of the purest functional languages out there, as you can only create new values and code, while you cannot mutate old values and code. In other words, everything is immutable in ALT.
So what about mutable IO, files, databases etc? You cannot have them in ALT! Of course, you can store ALT programs (in memory or in the cloud), but that’s not observable from within ALT. So IO must happen outside of ALT.