Partition versus File System question

[R.T.]

http://en.wikipedia.org/wiki/File_Allocation_Table#Initial_FAT16
In 1984 IBM released the PC AT, which featured a 20 MB hard disk.
Microsoft introduced MS-DOS 3.0 in parallel. Cluster addresses were
increased to 16-bit, allowing for a greater number of clusters (up to
65,517) and consequently much greater file-system sizes. However, the
maximum possible number of sectors and the maximum (partition, rather
than disk) size of 32 MiB did not change. Therefore, although
technically already "FAT16", this format was not yet what today is
commonly understood under this name. A 20 MiB hard disk formatted
under MS-DOS 3.0 was not accessible by the older MS-DOS 2.0. Of
course, MS-DOS 3.0 could still access MS-DOS 2.0 style 8 KiB cluster
partitions.

http://en.wikipedia.org/wiki/File_Allocation_Table#Extended_partition_and_logical_drives
To allow the use of more FAT partitions in a compatible way, a new
partition type was introduced (in MS-DOS 3.2, January 1986), the
extended partition; which was actually just a container for additional
partitions called logical drives. Originally only 1 logical drive was
possible, allowing the use of hard disks up to 64 MB. In MS-DOS 3.3
(August 1987) this limit was increased to 24 drives; it probably came
from the compulsory letter-based disk naming (A and B being reserved
for the two floppy drives). The logical drives were described by
on-disk structures which closely resemble the Master Boot Record (MBR)
of the disk (which describes the primary partitions), probably to
simplify coding. Though some believe these partitions were nested in a
way analogous to Russian matryoshka dolls, that wasn't the case. They
were always stored on disk like a row of separate blocks within a
single box; these blocks are often referred to as being chained
together, by the links in their extended boot record (EBR) sectors.
Only one extended partition was allowed. Logical drives were not
bootable, and the extended partition could only be created after the
primary FAT partition (except with third party formatting tools),
which removed all ambiguity, but also the possibility of booting
several DOS versions from the same hard disk.

http://en.wikipedia.org/wiki/File_Allocation_Table#Final_FAT16
Finally in November 1987, Compaq DOS 3.31 introduced what is today
called the FAT16 format, with the expansion of the 16-bit disk sector
index to 32 bits. The result was initially called the DOS 3.31 Large
File System. Although the on-disk changes were apparently minor, the
entire DOS disk code had to be converted to use 32-bit sector numbers,
a task complicated by the fact that it was written in 16-bit assembly
language.
In 1988 the improvement became more generally available through MS-DOS
4.0 and OS/2 1.1. The limit on partition size was now dictated by the
8-bit signed count of sectors-per-cluster, which had a maximum
power-of-two value of 64. With the usual hard disk sector size of 512
bytes, this gives 32 KiB clusters, thereby fixing the "definitive"
limit for the FAT16 partition size at 2 gibibytes. On magneto-optical
media, which can have 1 or 2 KiB sectors, the limit is proportionally
greater.



On Wed, Feb 27, 2008 at 1:26 PM, Madison Kelly <linux-5ZoueyuiTZhBDgjK7y7TUQ at public.gmane.org> wrote:
> FAT (and it's variants), specifically.
>
>  What exactly is the difference between say the 'FAT16 Initial' partition
>  identified as '04h' and the file system by the same name? Is the same
>  piece of software responsible for both roles?
>
>  Ditto question with 'FAT16 Extended' (05h), 'FAT16 Final' (06h) and so on.
>
>  Thanks, yet again!
>
>  Madi (the ever-questioning one)
>  --
>  The Toronto Linux Users Group.      Meetings: http://gtalug.org/
>  TLUG requests: Linux topics, No HTML, wrap text below 80 columns
>  How to UNSUBSCRIBE: http://gtalug.org/wiki/Mailing_lists
>
--
The Toronto Linux Users Group.      Meetings: http://gtalug.org/
TLUG requests: Linux topics, No HTML, wrap text below 80 columns
How to UNSUBSCRIBE: http://gtalug.org/wiki/Mailing_lists