Re: ProDOS' Block Index Question

[Ralf A. Quint <ralf_quint@hottmail.com>]

On Mon, 16 Feb 2004 01:11:39 GMT, "Bryan Parkoff"
<bryan.nospam.parkoff@nospam.com> wrote:

>    Hold ProDOS -- Let discuss MS-DOS for a while.

Well, it would have been better to do some research before making such
statements as below...

>    MS-DOS has root directory that contains 512 files (I can't remember the
>maximum). 

Wrong, the number of root directory entries is defined in the BPB
(BIOS Parameter Block). 512 is the usual number of entries on FAT16
formatted hard disks, a 1.44MB or 1.2MB floppy disk for example has
only 224 entries, a 360KB or 720KB floppy only 112 entries...

> This root directory has two separate FAT Table.  

Wrong, the FAT tables are not associated with any directory, they are
are part of the disk/partition properties...
Wrong, floppy disks have only one FAT, hard disk partitions "usually"
have two FATs, but both number and size of the FAT as well as the size
of the root directory are flexibel values defined in the BPB ...

> First FAT Table is original and second FAT Table is backup.  

Almost right...

> If root directory is destroyed or wiped by hardware failure.  There is only one way to rebuild root
> directory from scratch is through FAT Table.  

Wrong, if the root directory is wiped, you're screwed...
The only reference that a directory entry has to the FAT is the
starting cluster of a file. And with that information is gone, you
can't rebuild anything...

> FAT Table contains sector ID for each file.

Wrong, the FAT contains pointers to the next cluster belonging to a
file or FFFh/FFFFh in case of the last cluster of a file. Unless it is
a floppy disk, a cluster consists usually of more than one sector...

>    Why two copies of FAT Table are necessary while ProDOS has only one copy
>of Block Table?
>
Wrong question, why does ProDOS not keep a backup copy of the Block
table?

RQ