The original Pick Operating System and database.
There is a pre-built image:
wget https://github.com/Krowemoh/R83/raw/main/R83-HD.img
qemu-system-x86_64 -curses -m 8M -drive format=raw,file=R83-HD.img
You can also load this image into v86js and run R83 directly in the browser. Make sure to limit the memory size to 8MB!
Otherwise you can use qemu or PCem to run the pre-built image.
You will need PCem to build a hard drive with R83 installed on it. You can then continue to use PCem to get into the hard drive or you can use qemu.
There are instructions and screenshots in INSTRUCTIONS.md to load R83 into PCem and building an image from scratch.