Native C compiler (smaller C) with Color text TV system. Under a tiny memory, libraries are hard to link, so library such print, filesystem is on the flash and call from function-table. PS/2 keyboard(US, Japanese) can be used. Library for Color Video...
For quite some time I have been thinking about the possibility to using a laptop to run all the heavy OpenPlotter and OpenCPN stuff instead of using a Raspberry Pi. The performance of the RPi is... well it's usable but it's not a pleasant user experience....
Here are some "Quickstart" instructions for the Menu, BASIC, VTL2, and Visual/02 programs in Mike Riley's alternate program ROM. They're not a full manual yet, but will get you started and give you a "taste" of vintage programs and languages. A Quickstart...