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From: David.Plummer@f70.n140.z1.FIDONET.ORG (David Plummer)
Newsgroups: comp.sys.amiga
Subject: Re: AmigaDOS Filing systems quest
Message-ID: <768.26CB89CF@weyr.FIDONET.ORG>
Date: 14 Aug 90 15:03:36 GMT
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Well, you can check the AmigaDOS manual for some old BCPL charts, or I
could send you home-made include files that have structures for all the
disk blocks.  The only problem is that if you use structures, you are
locking yourself into 512 byte sectors, which is a nono.
 
To be right, you should use the disk blocks via offsets, which are
listed in the AmigaDOS manual.Basically, what you have are the
BitmapKeys, a table of twenty five sectors that each contain 127
longwords (on a floppy only one sector is needed).  Each of these
longwords has 32 bits.  If a bit is set or clear determ,ines if the
block is used or free.  This scheme gives you only about 50meg of room,
so FFS adds a BitmapExtension byte that points to a sector containing
another list of bitmap keys, a checksum, an
and so on (line noise is bad, bear with me).
 
It's pretty confusing, but certainly more open-ended than some other
filing systems I can think of....


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