Nothing new. The version of 7-Zip ZS I have has the following for ZIP:

• Deflate
• Deflate64
• BZip2
• LZMA
• PPMd
• Zstandard

But you can limit your compression. RAR 2.50. ZIP deflate. 2.04g ecr... If you release a nice DOS retro game and provide archives in your homepage. But those archives are more or less unusable in your nice retro machine.

I believe PKZip would work on an old DOS machine and handle .zip files and the Deflate technique. I don't know where to get it, but try Googling "pkzip archiver."

We could just port 7-Zip to DOS. The Windows GUI is just a front-end for the CLI.

I'm not sure exactly what code would have to be made from scratch as I have never looked at the source or what libraries it uses.

By default, it works all the way back to Windows 2000.

I am always using the latest winrar of the time with it's zip option to compress archives and the zip files created can be unzipped with the old PKZIP official releases under DOS
If a DOS archive is using an incompatible method just repack it with the winrar trial ( that never ends...)

It's annoying but only a slight inconvenience.
Much better to unpack on your modern machine and repack to whichever standard you prefer

keropi wrote on 2025-12-04, 22:09:

I am always using the latest winrar of the time with it's zip option to compress archives and the zip files created can be unzipped with the old PKZIP official releases under DOS
If a DOS archive is using an incompatible method just repack it with the winrar trial ( that never ends...)

some ancient ZIP archives that uses old PKZIP methods (for example, Reduced4) can't be unpacked by 7-Zip/WinRAR/etc. and you may finally need old good PKUNZIP to do so.

I always use Info-ZIP.
It's open source, and available for all platforms - the only more portable piece of software is "Hello World" 🤣

cyclone3d wrote on 2025-12-04, 22:05:

We could just port 7-Zip to DOS. The Windows GUI is just a front-end for the CLI.

I'm not sure exactly what code would have to be made from scratch as I have never looked at the source or what libraries it uses.

By default, it works all the way back to Windows 2000.

It's already been ported. See here.

Yep. I tried DOS version of 7Z. Version 16.02 and it unpacks newer ZIP files.

roytam1 wrote on 2025-12-05, 07:10:

some ancient ZIP archives that uses old PKZIP methods (for example, Reduced4) can't be unpacked by 7-Zip/WinRAR/etc. and you may finally need old good PKUNZIP to do so.

never found one tbh - is there some example somewhere?

Have seen few old shrinked and imploded ZIP files. Never heard of Reduced4.

keropi wrote on 2025-12-05, 17:34:

roytam1 wrote on 2025-12-05, 07:10:

some ancient ZIP archives that uses old PKZIP methods (for example, Reduced4) can't be unpacked by 7-Zip/WinRAR/etc. and you may finally need old good PKUNZIP to do so.

never found one tbh - is there some example somewhere?

For my DOS stuff I release, I mainly use an original registered version of PKZIP, and I usually use -EXtra compression, and the option to "sign" the .ZIP file.

I have no trouble UPZIPping with older 7ZIP both the DOS versoon, and a couple winblows versions (32 & 64 bit)

But.. I've had reports of problems unzipping with more recent 7ZIP versions:

Re: DDLINK: Easily move files between/To/From DOS systems

keropi wrote on 2025-12-05, 17:34:

never found one tbh - is there some example somewhere?

I've created it with PKZIP 0.92...

1-e   Specifies the extra compression method.  This method is known as
2     Reducing.  If the -e option is not specified, the default method of
3     compression is Shrinking.

Info-ZIP needs special compile-time option to support that method...

1$ unzip -t OLDIE.ZIP 
2Archive:  OLDIE.ZIP
3   skipping: MANUAL.DOC              `reduce' method not supported
4Caution:  zero files tested in OLDIE.ZIP.
51 file skipped because of unsupported compression or encoding.

1$ unzip -v | grep unreducing
2        COPYRIGHT_CLEAN (PKZIP 0.9x unreducing method not supported)

heh , winrar opens it and you can view the file but cannot do anything more than that:

! OLDIE.ZIP: Unknown method in MANUAL.DOC
! OLDIE.ZIP: No files to extract

never had this before 🤣

Both RAR and ACE use PKUNZIP so they can be used to unpack OLDIE.ZIP.

Cyberdyne, can you show your file that you are unable to unpack in DOS?

keropi wrote on 2025-12-05, 17:34:

roytam1 wrote on 2025-12-05, 07:10:

some ancient ZIP archives that uses old PKZIP methods (for example, Reduced4) can't be unpacked by 7-Zip/WinRAR/etc. and you may finally need old good PKUNZIP to do so.

never found one tbh - is there some example somewhere?

sure. http://ftpmirror.your.org/pub/misc/dos/RbbsIn … 6Z/CHGCOLOR.ZIP

7Zip 9.2 can open OLDBIE.ZIP and see MANUAL.DOC but cannot decompress it "unsupported compression method"

I can open OLDBIE.ZIP in Windows explorer (Win7) and drag out MANUAL.DOC which looks like to normal text file.

I can also unzip it in DOS with PKUNZIP 2.04g and Info-ZIP UnZip 3.0 - also appears to work OK
(I don't know how/when the UnZip I have was compiled, but I've had it *many* years)

Who would have thought, Explorer unpacks something 7-Zip doesn't.

But if I haven't come across such ZIP in first 3 decades of being here...may be more likely for pensioners of VOGONS. 😜