Path: utzoo!attcan!uunet!cs.utexas.edu!csd4.milw.wisc.edu!mag2
From: mag2@csd4.milw.wisc.edu (Michael A Gorski)
Newsgroups: comp.sys.atari.8bit
Subject: Re: Disk Operating Systems
Message-ID: <3267@csd4.milw.wisc.edu>
Date: 8 Jul 89 11:42:19 GMT
References: <115200034@uxa.cso.uiuc.edu> <1790@zaphod.axion.bt.co.uk> <10134@dasys1.UUCP>
Sender: news@csd4.milw.wisc.edu
Reply-To: mag2@csd4.milw.wisc.edu (Michael A Gorski)
Organization: University of Wisconsin-Milwaukee
Lines: 21

In article <10134@dasys1.UUCP> andrewh@dasys1.UUCP (andrew huie) writes:
>"Inside Atari Dos" is compiled by Bill Wilkinson.  (Stuff deleted...)!
>Note that there is an error in how a sector in a
>file is set up, if I remember correctly, the byte which says how many data 
>bytes in a sector is 127, not 125 (bytes go from 0-127 for a single density
>disk). 
>-- 
>andrew huie ( andrewh@dasys1.UUCP )
>Big Electric Cat Public UNIX
>...cmcl2!dasys1!andrewh  (or pick your own bang path, if you wish)

Bill Wilkinson is correct but misleading.  There are 128 bytes in a single
density sector (0-127) but only 125 (0-124) are data bytes.  The last
3 bytes are for DOS control.

In byte 125, the left 6 bits are the file number.  The right 2 bits and all
byte 126 are a point to the next sector in the file.  Byte 127 is actual
number of data byte being used in that sector.

   Mike
   mag2@csd4.milw.wisc.edu