China DOS Union

Yu Fei, please come in, a DOSIMG question

Why is it that when an image is made from a floppy with a few bad sectors, DOSIMG can't extract it, but UNDISK can?

Oh, it's like this. I do a strict check on the FAT of the disk image to determine whether this file is a disk image. If the check result is incorrect, then I don't perform the extraction. For disk images made from disks with bad sectors, in the FAT table their "total number of sectors" * "bytes per sector" != "disk image file length", so it is considered not to be a disk image. If I remove this check, then it can be extracted. The reason I perform a strict check is to avoid treating non-disk-image files as disk image files. If this causes inconvenience, I will relax these checks in the next version.

Recently I've been doing some extensions for Delphi for DOS. When this thing is finished, I'll use it to make the next version of DOSIMG, so under pure DOS there will be no need to specially load an extender to run DOSIMG. And it will be a 32-bit DOS program, able to make full use of memory, and it will have a window interface (a DOS character window; if I want to make a graphical window, that will depend on the progress of Delphi for DOS), no longer just command-line only. But exactly when it can be finished depends on the progress of Delphi for DOS. I hope the extensions I wrote can become part of DWPL version 2.2.0.

Very nice. Also, I think DOSIMG's shortcomings are that it's a bit slow, and it doesn't support very many formats.

Actually, making DOSIMG not need the CWSDPMI extender isn't difficult either. For example, you can directly STUB it with WDOS/X 0.95, and then DOSIMG.EXE alone will be enough to run it.

Yeah, the slow speed is because when it was first written in Turbo Pascal, due to DOS limitations I didn't dare make use of memory, so the data operations were basically all done on disk. Later, after changing it to Free Pascal, I didn't modify that, so it became even slower. For the next version I plan to rewrite all the code in Delphi, add support for more file formats (if possible, even CD images), and support both command-line and character-window operation. Besides extracting the entire image file, it will also be able to do other operations, such as add, delete, copy, move, and so on. Because there is too much work to do, it's hard for me to guarantee when the next version will be finished. :-(

Here is the C source code of CDMAKE, an ISO CD image creation program under DOS:
http://www.alumni.caltech.edu/~pje/cdmake.txt

Wengier, thank you so much! ^;^

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