sector numbering on floppy and hard drives?

On 10 Oct 2009 at 22:24, Andrew Lynch wrote: Convention, mostly. At least for soft-sectored media, the sector (and side and cylinder, really) can be anything the person who writes the low-level formatting software wants it to be. There are systems out there that use sector 0 as the first sector (HP 125, for example or several Kaypro formats). By the same token, there are systems that use 65, 128 or 192 as the first sector. I know of at least one system that used the sector ID to differentiate between single- and double-sided formats. There is at least one PC AT ST412 interface hard disk controller out there that uses a "hidden" 256-byte sector 0 to record the drive parameters. Cylinder, head and sector numbers need not even be consecutive, although that does make things easier when a controller capable of multi-sector transfers is used. --Chuck