That said you can pick a very old PC with a functional floppy drive, and write a Forth interpreter under DOS in assembler. Then, you "just" have to replace the system call to DOS to read/write blocks to/from your blockfile with BIOS calls to read/write floppy disk sectors. You can even do that under DOS, provided you don't have anything valuable on your hard disk. This DOS-based Boostrap Forth should feature at least an editor, a mini-assembler and a self-compiler. Once you have that, you can make a bootable disk that boots on your standalone Forth interpreter (which has therefore been promoted to the rank of 'OS' ;-). With a very old 5MHz 8086 "laptop" featuring an half-broken single density floppy disk drive, one can boot, make a change in the kernel, recompile, then reboot and test the change within a minute. Those machines were power monsters. It's a pity that CGA cards didn't have shaders ;-).