[Coco] The .DSK format/structure

[Bill Pierce]

FWIW, JVC format has the possibility of a header, but rarely used. The most I've found is a 2 byte header which is require for it to be read with XRoar.
On the other hand, the DMK format is very complex in that it not only contains the "raw data" but also contains the "in between track" info that is on a real disk. This is the info the disk drive uses to locate tracks and sectors. For this reason, DMK is a hard format to support, though DK Coco Emu, Vcc and XRoar all support it. In fact, XRoar will write only to DMK disks, and even then, they have to be a certain type.
Both formats can be found on the web.. just google "DMK disk format" or "JVC disk format".
The only other format I'm familiar with is VDK which I know nothing about. Any of these formats can have the ".dsk" extension.
JVC was originally developed by Jeff Vavsour for his TRS-80 Model X emulators then used for his Coco emulators.
DMK was developed by David Keil for his TRS-80 Model X emulators then Coco as well.

David has a very good format description here:
http://fjkraan.home.xs4all.nl/comp/trs80-4p/dmkeilImages/trstech.htm

I have a copy of Jeff's format here:
https://sites.google.com/site/dabarnstudio/jvc-disk-format


Hope this helps :-)


Bill Pierce
"Today is a good day... I woke up" - Ritchie Havens
 

My Music from the Tandy/Radio Shack Color Computer 2 & 3 
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-----Original Message-----
From: Aaron Wolfe <aawolfe at gmail.com>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Sent: Fri, Aug 22, 2014 11:59 am
Subject: Re: [Coco] The .DSK format/structure


Most .dsk files for the Coco have no "format" at all.  They are just raw
ata with no additional information of any kind.
There are a few .dsk files that use the "JVC" format.  For the most common
ized disk image, the jvc spec also happens to be just raw data with no
dditional information.  If you encounter a .dsk with a file size *not*
venly divisible by 256, chances are you have a JVC disk.  You can learn
bout this here:  https://sites.google.com/site/dabarnstudio/jvc-disk-format
n Aug 22, 2014 10:56 AM, "Tony Cappellini" <cappy2112 at gmail.com> wrote:
> As as result of listening to Randy Kindig's floppy days podcasts,
 I'm now playing with an Apple II emulator and software. I've noticed that
 this emulator also reads .DSK images. But I'm fairly sure that the author
 of the emulator chose the .DSK extension as a convenience.

 I want to look at the differences between the Apple2 and coco .DSK images.
 Would someone point me to the following:

 1. The specification for a coco .DSK image. Obviously, at some level this
 needs
     to be the same as the floppy disk format for a physical floppy, but
 this     structure could also be embedded within a higher level structure
 of the file.

 2. Software used for reading/writing coco .DSK images.
 3. Source code for that reading/writing coco .DSK images

 I want to write a small program that will detect the image type and dump
 the contents of either disk image.

 Thanks


 Tony

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