[TBD] I should go upload a 64k and 2x32k image here
It does some initial probing to see if there’s a disk controller!
.. If it finds one then it installs itself as a DOS command (‘g’).
.. If it doesn’t find one then it starts immediately.
DOS ROM extension commands only work with PC-DOS - so no, you can’t
use MS-DOS here!
It likely installs itself as a DOS extension command in order to use
DOS interrupts for the file IO. Apparently this is a common thing done
by IBM PCjr cartridge software to avoid needing DOS in ROM.
(Although wouldn’t DOS in ROM be actually quite useful?)
What about a manual?
I haven’t found a manual yet online!
So, some usage notes!
it runs in 640x200x4 colour mode
Right click the 4 colours to cycle through the hardware palette options
When drawing circles, squares, lines - you use left click to size,
and right click to actually draw them!