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From: sauder@nbs-amrf.UUCP (Jeff Sauder)
Newsgroups: net.micro.cbm
Subject: EPYX Fast Load and "Edit Disk" function
Message-ID: <273@nbs-amrf.UUCP>
Date: Mon, 28-Apr-86 12:54:44 EDT
Article-I.D.: nbs-amrf.273
Posted: Mon Apr 28 12:54:44 1986
Date-Received: Sat, 3-May-86 00:39:52 EDT
Distribution: na
Organization: National Bureau of Standards
Lines: 37

Recently I downloaded a sequential file from a bulletin board, only
to find that the file came across as a program file.  I realize
there are utilities to change the type of a file, but being a true
hacker, I decided that I must attempt to rectify the situation
myself.  According to my 1541 reference manual, the location of the
directory information resides on track 18.  However, when I
attempted to use the "Edit Disk" function of my EPYX Fast Load
cartridge to alter track 18, I found no information on track 18.
(According to the "Edit Disk" function, anyway)  I eventualy
located the correct information on track 12, altered the hex code
so that the program file was now a sequential file, and then
proceeded to use the sequential file for its desired purpose.  My
question, however, is this --  What is wrong with this particular
function on Fast Load?  I know that the information was really on
track 18.  Are all track numbers actually referenced by a number
six less than the true number (i.e. 12 instead of 18)?

Also, I attempted to write directly to track 18 of the disk with
limited success.  I tried to place the information '255' and '129'
into track 18, sector 1, bytes 3 & 4 respectively.  (129 is the
code for sequential files while 130 is the code for program files.
I was trying to replace 130 with 129 and I assumed that I also had
to write the previous 255 to the disk also, because I could find no
way of skipping over a byte within a sector.)  Anyway, I
accomplished the desired feat with undesirable side effects.  My
short little program continued writing '255' and '129' throughout
the entire sector.  All the odd numbered bytes had '255' in them
and all the even numbered bytes had '129' in them.  Is it possible
to write to only part of a sector, or must I write to the entire
sector when attempting a Block-Write?  

You can send me E-mail if you wish, but I'm willing to bet that
some others may be interested in this, too.  Thanks in advance.

-- 

Jeff Sauder     {seismo,umcp-cs}!nbs-amrf!sauder