Path: utzoo!utgpu!water!watmath!clyde!att!pacbell!ames!pasteur!ucbvax!decwrl!purdue!gatech!udel!mmdf
From: Leisner.Henr@xerox.com (marty)
Newsgroups: comp.os.minix
Subject: Re: DOS[READ\WRITE\DIR] on hard disk
Message-ID: <2649@louie.udel.EDU>
Date: 20 May 88 13:43:29 GMT
Sender: mmdf@udel.EDU
Lines: 34

I'm currently trying to do a rewrite of dos[dir/read/write] to handle hard
disks.

The first thing I did was have the argument specify the block special device
(/dev/fd0 instead of 0).

However, it seems hard disks are a major pain.  In order to compute the fat
size, there is this mega-equation in the DOS tech reference manual, based on
some generic system parameters and the number of sectors in the partition.  So I
need a way to determine sectors/partition.

The algorithm would have to look something like:
	if(floppy disk)
		if(360K floppy)
			do 360k floppy
		if(1.2 meg floppy)
			do 1.2 meg floppy
	else	/* hard disk */
		figure out sectors for this partitions (somehow)
		check first fat entry for hard disk partition ID
		do good stuff
	end

I suppose the  major device numbers could be examined to determine floppy/hard
disks.
But in multiple hard disk systems, how would the boot block be read in?  
Or is there a better way to determine number sectors/drive?  Seek off the end?
Then divide the offset by SECTOR_SIZE?

marty
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