Some apps written in SubX and Mu. Where the rest of this repo relies on a few
Linux syscalls, the apps in this subdirectory interface directly with hardware.
We still need the top-level and apps to build them.

I'd like to eventually test these programs on real hardware, and to that end
they are extremely parsimonious in the hardware they assume:

  0. Lots (more than 640KB/1MB[1]) of RAM
  1. Pure-graphics video mode (1280x1024 pixels) in 256-color mode.
  2. Keyboard

That's it:
  * No wifi, no networking
  * No multitouch, no touchscreen, no mouse
  * No graphics acceleration, no graphics
  * No virtual memory, no memory reclamation

Just your processor, gigabytes of RAM[1], a moderately-sized monitor and a
keyboard.

These programs don't convert to ELF, and there's also currently no code/data
segment separation. Just labels and bytes.

Most programs here assume `main` starts at address 0x8800 (3KB or 6 disk
sectors past the BIOS entrypoint). See baremetal/boot.hex for details.

So far the programs have only been tested in Qemu and Bochs emulators.

[1] Though we might need to start thinking of [the PC memory map](https://wiki.osdev.org/Memory_Map_(x86))
as our programs grow past the first 512KB of memory. Writing to random
locations can damage hardware or corrupt storage devices.