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Re: load vectors and whatnot [message #283142] Mon, 17 March 1986 12:49
jhs is currently offline  jhs
Messages: 26
Registered: May 2013
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Article-I.D.: mitre-be.8603171654.AA07440
Posted: Mon Mar 17 12:49:33 1986
Date-Received: Wed, 19-Mar-86 00:55:05 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The MITRE Corp., Bedford, MA
Lines: 35

I just noticed that "Inside Atari DOS" apparently has an error in describing
the sequence of the control bytes at the end of DOS sectors.  I would
appreciate confirmation by anyone who knows.

Inside Atari DOS (IAD) says that a sector consists of 128 bytes, numbered 0
through 127, and that in DOS files only 125 bytes (0 - 124) are used for data.
(This much is true.)  They go on to say that byte numbers 125, 126, and 127
are numbered as follows:

		125                     126                     127
IAD    | # of bytes actually    6 hi bits=file number     low 8 bits of next-
Version| used in the sector     2 lo bits=hi bits of      sector number (link)
				next-sector number

Documentation supplied with David Young's OMNIMONXL resident monitor/debugger
says that the numbering is

		125                     126                     127
The   | 6 hi bits=file number   low 8 bits of next-     number of bytes
Truth!| 2 lo bits=hi bits of    sector nr (link)        actually used in this
      | next sector nr (link)                           sector.


Based on what I can see in the actual sectors I have looked at, both with
OMNIMONXL and with another independently developed debugger, David Young's
information appears to be correct and Inside Atari DOS appears to have
incorrect information.

I would appreciate confirmation of my conclusion by others who have noticed
the error in IAD.  (Also if they have any other errors I would like to be
made aware of them!)

						John Sangster
						jhs at mitre-bedford.arpa
				   !ihnp4!linus!mbunix!jhs
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