Now format the disk using FAT12 and put the command.com program on there... now rename the program foobar.com.
Reset the machine, and when it boots, it will promt you for the file name of the command interpreter... which can be entered and it will boot.
Hense the BIOS can read the FS...
No, I think that's false
The code that asks you for the name of the command interpreter will do the same thing regardless of the BIOS, the code to do that is written on the bootblock.
The BIOS can read the bootblock into memory and execute code from it.
Try using a QNX disk, or a Linux boot disk.
Or one interesting idea, is to use PC-TASK, to format a floppy, it has its own interesting code for the boot block!! ;-)