DOS ain't dead

Igor Pavlov released 7-ZIP 9.07 beta on 2009-08-29

What's new compared to 4.65:

- LZMA2 compression method:
- - Can use 4 CPU cores instead of only 2 (useless in DOS)
- - Better compression of poorly compressible files (very useful)
- - Less expansion of incompressible files
- - Possibly marginally better compression of "ordinary" files
- - Not decompressible by 7-ZIP 4.65 and older
- Support of disk images (only in the full DLL version)
- - Physical disk images AKA "MBR archive"
- - Logical volume images AKA "FAT archive" (FAT12, FAT16, FAT28, with VFAT/NTLFN hack) and "NTFS archive" (with kicked files and special "files" like "bitmap" and "logfile", with breakage-through access restrictions that might apply ), OTOH not corrupt filesystems, and flaw see below
- - Can connect to Physical disk and Logical volume using "\\.\PhysicalDrive0" and
"\\.\C:" ? "\\.\C:\"
- Can extract files from nested uncompressed archives without need to extract the full outer archive (Win32 GUI FM only, useless in DOS)

What's new compared to early 9.0x versions:

- Fixed BUG's in handling some FAT28 and NTFS filesystems
- "Some bugs were fixed"

http://7-zip.org/download.html
http://sourceforge.net/projects/sevenzip/forums/forum/45797/topic/3382891

So 7-ZIP 9.xx can/could be used:

- As a DOSIMAGE : there is nothing else available with support beyond 1.4 MiB floppies, but it is read-only, no way to brew new or modify existing disk images

- As a NTSC4DOS : there are many such things around, but all closed source, and not "that free", but again read only (and I personally don't need it "that badly" )

- As a DOSNTLFN alternative, read only of course (but no "drop-in" replacement)

- To provide additional/alternative filesystem support (remember DRFAT32 ??? )

There is a severe flaw, though. 7-ZIP considers a physical disk image as an "uncompressed nested archive", like a TAR inside a TAR, and "extraction" of a physical disk image (AKA "MBR archive") results in a few partition images, in worst case just 1, instead of files stored on them. So to extract files from a 500 GiB physical disk with just 1 partition, one would have to store the partition image as a temporary file on another > 500 GiB disk having a filesystem supporting that bloated files. This problem doesn't exist in the Win32 FM, having the privilege to extract "directly" from nested uncompressed archives without need to extract the full outer archive.

Igor is aware of this flaw of the commandline version and might fix it, but nobody knows when. However, it could also be workarounded by "mounting" some "\\.\Z:\"-like thing somewhere outside of both DOS and 7-ZIP, so some HX enhancement or a placing a hepler TSR "below" HX providing "\\.\Z:\" to 7-ZIP redirected to a physical disk partition using INT $13 or into an image file would allow to extract files from both physical disks and image file of such.

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