22 Dec
2006
22 Dec
'06
8:13 a.m.
Dave Dunfield wrote:
Yes, I'd be naturally inclined to use cylinders - I just wondered if there was
any good reason not to, given that (particularly in the floppy world) 'tracks'
often gets thrown around to mean 'cylinders'. As Brian says, it's probably a
hang-up from the days when floppy disks were pretty much single sided and so
the terms did mean the same thing...
Oh, that's another thing - is there a correct convention for track numbering?
There seem to be equal numbers of apps out there which treat the first track
as track zero as there are which treat it as track one :-) (Personal
preference would be to number from zero, just because it likely makes some
programming calculations easier, but I'm not sure if it's technically wrong to
present that visually to the user...)
Out of
interest, which is the correct terminology when defining a single point
on a disk's surface - is it better to talk in terms of cylinders, or tracks?
People often seem to talk about floppy drives in terms of tracks, heads and
sectors (e.g. for an 80 cylinder floppy with two sides they'll still talk in
terms of tracks 1-80 in conjunction with a side number, even though the media
has 160 tracks in total)
The problem is that "Tracks" is ambiguous - it could be "track number the
start
of the surface" or "track number from the start of the entire media" both
uses of the
term have become common enough that the meaning has to be explicitly stated.
My vote is for Cylinders to refer to the position over any surface (ie: from
Cylinder 0 - funny - many referefnces refer to this as Track-0 even if they
use the Cylinders convention otherwise), and for Tracks to refer to the position
from the beginning of the media (entire disk) - But I know I've used Tracks
in both ways - best to explicitly state which convention you are using. btw - with floppies, it can be worse - NorthStar
floppies are logically treated
as a single range of 35, 40, 80 or 160 tracks (depending on the type of drive)
however when you reach the innermost Track/Cylinder of Side-0, the next
logical track is the innermost track/cylinder of Side-1 - in other words, it steps
in for increasing track numbers when they exist on Side-0 and out for
increasing track numbers when they exist on Side-1 - So absolute track and
sector numbers (absolute from start of media) will be different than you might
expect if you are used to a system which advances C/H/S though it's
logical progression. This is yet another ambiguity with "Tracks".
Hmm, that's interesting. I'm messing around writing a floppy image manipulator
[1] that'll work at the filesystem level. NorthStar's very low on the priority
list though, so I'll just keep that in mind - when it comes to it though it
should only be an issue at the interface between the filesystem driver and
disk image driver, so it's not something that the user needs to worry about.
[1] Actually, I'm trying to avoid the word 'floppy' as there's no reason
that
it shouldn't work with hard disk images too, and probably even tapes.
cheers
Jules