Re: Disk format

[Rubywand <rubywand@swbell.net>]

David Wilson writes ...
> 
> "Aurelien Mere" <amere@multimania.com> writes:
> >Does anybody know the disk format of 3"5 apple II disks ?
> >I mean : number of sectors, tracks, bytes/sectors, heads, etc...
> 
> It is the same (well almost) as the Mac:
> 
> 80 tracks
> 2 heads
> 512 bytes/sector (Mac has extra 12 bytes for flags, Apple // has zeros)
> Variable number of sectors per track
> 
> For a single sided disk:
> 
>         Tracks  Sectors/Track   Sector #s
>         0-15            12        0-191
>         16-31           11      192-367
>         32-47           10      368-527
>         48-63           9       528-671
>         64-79           8       672-799
> 
> I assume that for a double sided disk you just double the sector numbers.
> 

     Yes. For 2 sides, a 512-byte sector is usually called a "block" and
the numbering of blocks alternates between the sides for each Track. For
example ...

Track 0, Side 1 has blocks  0-11 (decimal)
Track 0, Side 2 has blocks 12-23 (decimal)


So, you end up with ...

        Tracks    Blocks/Track    Block Numbers
         0-15     12/side= 24        0-383   (decimal)
         ...
        64-79      8/side= 16     1344-1599  (decimal)


Rubywand