UNIX® on the Game Boy Advance is an implementation of the 5th version of the Unix Operating System for the ARM chip inside the gameboy. To do this, it runs SIMH, a PDP-11 simulator which has been ported to a bunch of different systems. The original RK05 disk image is combined with the PDP-11 simulator to make a functioning 5th Edition workstation.

It’s… just… brilliant.

On the right, you can see a screendump. Notice that it is compiling a simple Hello World C program.

If you are into this stuff, you can get lots of different PDP-11 software off the net with a minimum of searching.