sb@pro-generic.cts.com (Stephen Brown) (05/31/90)
In-Reply-To: message from ce1zzes@prism.gatech.EDU In this message, Eric Sheppard says: >on an IBM diskette, the small hole near the center of the diskette is used >to indicate A) the start of a track B) the start of a sector. > >My answer (B) was judged incorrect, and my debate with the instructor would >not change his mind. He is convinced it determines the start of a track! >He also contends that Apple formatted disks do not need the index hole at all! I have seen 5-1/4" disks with one index hole, and I've seen them with multiple index holes. I suspect that disks with just one are for track start, and ones with multiple holes are for sector start. Machines which require hard sectored disks seem to have disappeared, but I do remember several years ago when you could buy 5-1/4's in different configuations, presumably with different hole spacing. Let me quote Jim Sather, in Understanding the Apple II, Quality Software pub., copyright 1983, page 9-3: "Hard sectored disks are disks with little holes in them which divide the disk into a number of sectors...." The Apple II has never used the index hole, as the Apple II uses soft sectored disks, that is, formatting information is encoded as particular sequences of disk bytes. Let me quote Don Worth and Pieter Lechner, in Beneath Apple ProDOS, Quality Software pub., copyright 1984, page 3-3: "The sectoring does not use the index hole, provided on most diskettes, to locate the first sector of the track. The implication is that the software must be able to locate any given track and sector with no help from the hardware. This scheme, known as soft sectoring, takes a little more space for storage but allows flexibility..." Whether this helps you get a higher mark or not, I hope it enhances your understanding of the Apple II. UUCP: crash!pro-generic!sb ARPA: crash!pro-generic!sb@nosc.mil INET: sb@pro-generic.cts.com