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From: bob@nbires.UUCP (Bob Bruck)
Newsgroups: net.micro.pc
Subject: Re: Re: Norton Utilities (Unerase, actually)
Message-ID: <440@nbires.UUCP>
Date: Fri, 19-Jul-85 11:25:59 EDT
Article-I.D.: nbires.440
Posted: Fri Jul 19 11:25:59 1985
Date-Received: Sun, 21-Jul-85 03:42:53 EDT
References: <185@drivax.UUCP> <18923@mgweed.UUCP>
Organization: NBI,Inc, Boulder CO
Lines: 26

Daniel Gray wrote:

> The FAT (File Allocation Table) contains smaller structures within it
> that are sometimes refered to as FCBs (File Control Blocks). The table
> or control block is simply an index to the beginning of the file and
> also contains the number of records that the file contains. When a file
> is erase, the FCB -or- FAT is flagged that this entry is now availible 
> for use.

Now I am really getting confused!  I thought that the directory information
on the disk contained the location of the first allocation block for the
file described by that directory entry.  Once you know the first allocation
block, you can use the FAT as a linked list to find subsequent allocation
blocks.  I assumed (probably incorrectly) that when a file is deleted, each
FAT entry in this linked list is set to zero (000) to indicate that this
cluster is unused and available.  If this linked list is destroyed in this
way, then the file would be unrecoverable (I think).  On the other hand, if
this assumption is incorrect, then DOS must at some point do "garbage
collection" to recover space used by deleted files.

Can anyone out there in NETland (Microsoft, are you listening?) clear up my
confusion about this? Thanks.

					Bob Bruck
					NBI, Inc.  Boulder, Co.
					(hao | allegra | ...)!nbires!bob