Hi guys,
Digging through my old repositories, I found this ZX81 API.
As I recall, I wanted some way to buffer the screen and speed up output using z88dk, so I defined the entire ZX81 character set as a header file and wrote a small amount of low-level C as well.
You never know, I might actually do something with it now, unless z88dk has improved since 2013 (which I suspect that it has).
Regards,
Shaun.