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From: new@ee.udel.edu (Darren New)
Newsgroups: comp.sys.amiga.tech
Subject: Re: AmigaDOS Filing System Block Format
Message-ID: <27022@nigel.ee.udel.edu>
Date: 9 Aug 90 16:54:39 GMT
References: <2761@mindlink.UUCP>
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In article <2761@mindlink.UUCP> a275@mindlink.UUCP (Travers Naran) writes:
>1. What are the "words" refered to in the AmiDOS Tech manual? Long words or
>normal 16 bit words?

32-bit words. 

>2. The Checksum is confusing, 

Only if you have preconceived notions of how a Checksum should be computed.
You must arrange the checksum word such that adding up all the words in
the block comes out to zero. This way, the same routine can be used to
check the checksum on any block regardless of where the actual checksum is.
To rebuild the checksum, you must know where to put the checksum, of course.

A little algebra should tell you how to compute the checksum of a block
given that you know the desired conditions. Basically, set the CS to zero,
add up all the words, subtract sum from zero, and that is the CS (I think).
I have code that does this, so I can look it up if this isn't right.
The code is offline right now, however.

>3. T.SHORT and ST.ROOT, etc. where are these constants defined?

Hmmm... I remembered seeing them somewhere in the stuff from CBM, but
here is what the Disk Mechanic manual says:

T.SHORT is 2, T.DATA is 8, and T.LIST is 16.
ST.ROOT is 1, ST.USERDIR is 2 and ST.FILE is -3.

That should be all of them.  Can't help you with AmigaMail.
	    -- Darren