It’s all about onions. That and mapping what you want onto what you have. Thinking back to my 8085 project (yes, that long ago) we designed “the ideal machine” for what we wanted to do (real time telemetry gathering, mass reading of digital I/O, analog cards etc) and then we looked at what the 8085 could do along with the supporting stuff 8255-s. 8259, etc (programmable I/O and interrupt controller respectively) and gradually wrote software that supported co-operative multitasking, provided an “API” for all bespoke software to use etc etc it was dead interesting as it was my first real job and I still remember like it was yesterday!
So, I guess we’d first have to figure out an initial set of goals; maybe keyboard I/O and basic tty style I/O and go for it. There’d have to be a “BIOS Layer” where Elixir code (via NIF code) can make calls to the BIOS and then process the return data to do something.
I’d start some processes in memory and then have an ISR (interrupt service routine) post the raw keyboard event to an Elixir process and what happens from there is anybodies guess! Likewise for terminal I/O, a buffer can be populated with outbound data (like an asynchronous UART queue or something) and an Elixir process can “receive” character data and then make the relevant BIOS call to output some text.
I still think the Squeak Smalltalk is a good one; that runs on more platforms than the JVM and that is still the case last time I looked.
It would come down to isolating those places where I/O is required and start simple. Once you could do basic keyboard and screen work then you could turn your attentions to the persistent storage model..hell I’d be so bold as to map DEFSTRUCT-s onto physical disk structures and leave it at that. Imagine treating the hard drive as a relational database and that’s all you needed to know…I mean it works like that anyway but it goes via a backend database driver…so all you’d need is a “raw disk” abstraction layer instead and that should be enough.
I am sure I could spend a lot of time thinking about this but…
- is it worth it other than for pedagogical reasons?
- who would use it?
- how would you maintain it?
- is it worth it? and
- is it worth it ??
Moving on…for now 
