Source:GEnieLamp A2, December 1995
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Section excerpted from the December 1995 issue of GEnieLamp A2.
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What's a .DSK file?
Does anyone know what a .DSK file would be? A friend found a bunch of Eamons on an Internet ftp site, and they have that suffix. He can't figure out how to use them. ShrinkIt says it's not an archive.
(A2.TOMZ, CAT10, TOP10, MSG:27/M645;1)
>>>>> That is a "disk image" file, representing an Apple 5.25" disk, 16 sector, as follows:
1'st 256 bytes = Track 0, Sector 0
2'nd 256 bytes = Track 0, Sector 1
3'rd 256 bytes = Track 0, Sector 2
The common formats are:
|.DSK –||As described above|
|.DO –||Same as .DSK. (Note that these two formats have the data in "DOS 3.3 ascending logical sector order", data should be handled as sectors, and not as ProDOS blocks)|
|.PO –||This is essentially the same as .DO, except that it is in "ProDOS ascending block order". That is, it was created by reading a 16 sector disk with the ProDOS ReadBlock command, and is ordered Block 0, Block 1, Block 2, etc.|
Conversion between .DO/.DSK and .PO formats is relativly trivial, once one understands the differences.
Most files of this nature are stored as "Name.DSK.GZ" or "Name.DO.GZ", etc. You need a utility capable of unGZipping these archives prior to trying to write them back to 5.25" media. I have had very limited success using GZ2PKZ followed with Angel or PMPUnZip, and almost 100% success with StuffIt Expander w/Expander Enhancer. [I now have the source code for a GZ unpacker, but I haven't yet tried to port it to the GS]
These files are how Apple II emulators manage to deal with Apple disks without the needed hardware (they don't use a real drive, instead they work with virtual disks)
(HAROLD.H, CAT10, TOP10, MSG:30/M645;1)
[Minor editing at author's request]