DOSContainerPC-DOS 2.00 junk bytes in the FAT area
📅 2025-06-22 · ✍️ Bas v.d. Wiel · 🏷 documentation
This is something of a journal entry. I’m preparing to start work on implementing PC-DOS 2.00 compatibility, which means creating a bunch of pristine floppy and hard disk images to base my implementation on. 86Box is my friend here, as is the ghex utility for looking at every single byte. While trawling through a disk image, sometime I discover something intriguing. Apparently, PC-DOS 2.00 injects a bunch of stuff into the area of the disk where the FAT’s live but these bytes have nothing at all to do with the FAT’s. In fact, should the disk get enough files and subdirectories, these bytes would get mercilessly clobbered by the growing FAT. So, what gives?
