A while ago, I did some research into MFS, the original Macintosh File System. At the time, I was considering trying to implement a GS/OS File System Translator for it, though nothing ever came of that. MFS uses a 12-bit linked-list to store file allocation information, in a fashion similar to the MS-DOS FAT format.
This similarity is no coincidence; Over the weekend, I found this revealing passage on Andy Hertzfeld’s Folklore:
Our first file system used a simple data structure that didn’t scale well to large drives (in fact, it was suggested to us by Bill Gates in July 1981)…
Apple replaced MFS with HFS a year and a half later.
Microsoft extended FAT (FAT 8, FAT 12, FAT 16, FAT 32) as disk and file sizes grew bigger before replacing it with NTFS. FAT is still in use due to its simplicity and universal support.