[Coco] Creating a .dsk MESS image an EASY way!

[tim lindner]

Robert Gault <robert.gault at worldnet.att.net> wrote:

> There has been quite a bit of confusion over the MESS utility IMGTOOL
> partially caused by buggy versions. That will be a thing of the past 
> when the next MESS is released because of a new function included within
> the Coco emulation.
> 
> I recently answered a question saying that I created a 0byte file .dsk
> file and ran DSKINI from MESS Coco emulation. After posting that, I 
> realized I'm the only person that can do that because of a special 
> version of RGBDOS. However, I'm going to show you how to do the 
> equivalent, regardless of your DOS. First we need some background on how
> MESS works.
> 
> The MESS philosophy is to emulate all hardware as closely as possible
> regardless if it makes sense in the context of emulation. In the case of
> disk I/O, the result is odd. MESS will not run DSKINI on a 0byte .dsk
> image because the image is not recognized as a disk. DSKINI will run 
> with 157KB .dsk files.

A stock DSKINI command will do no such thing. Currently the emulated
179x will abort the write track command as soon as it is recieved.

> If you examine the full .dsk image, you will only see the data portion
> for each sector but not the format information found on a real disk. 
> Users of RGBDOS in MESS will know that you can DSKINI a 0byte .vhd image
> and it works perfectly. What is the difference? RGBDOS treats a hard 
> drive as if it were an image consisting only of data portions of 
> sectors. No low level formatting is done. Clearly MESS will extend a 
> .dsk image if it thinks a low level format is not being called.
> 
> So clearly anyone can create a .dsk image from a 0byte file in MESS, 
> regardless of DOS, if they do a raw write to the image. Here's one way
> to do it.
> 
> 00 REM Substitute for DSKINI with MESS
> 10 CLEAR500
> 20 A$=STRING$(128,255):B$=STRING$(128,255)
> 30 FORT=0TO34:FORS=1TO18
> 40 DSKO$0,T,S,A$,B$
> 50 NEXTS,T
> 
> This method can do what DSKINI can't do because the number of tracks and
> sectors can be any number desired. You can easily create an 80 track 
> .dsk (without any JVC header info) by changing the range of T.

A stock DSKO$ command error out if the track or sector parameter is too
large?

> Creating a 0byte file is also easy using Windows. A right click in a 
> directory should bring up "new text file" as a possibility. Just make
> the extension .dsk.

****

You said above that these instructions will work, "regardless of your
DOS". I just wanted to point out these limitations.

-- 
tim lindner
tlindner at ix.netcom.com                                            Bright