VOGONS


First post, by Harry Potter

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Hi! I know PKZip and DOSRAR and am working on my own, much better 16-bit compression technique. However, my technique is currently nowhere near usable. 🙁 Until I get it ready, what other archivers should I try? I am willing to sacrifice slightly speed for compression ratio.

Joseph Rose, a.k.a. Harry Potter
Working magic in the computer community

Reply 1 of 9, by jesolo

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Perhaps try out ARJ & LHA

Reply 2 of 9, by Harry Potter

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Okay. Thank you. 😀 I'll Google it now.

Joseph Rose, a.k.a. Harry Potter
Working magic in the computer community

Reply 3 of 9, by mkarcher

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LHA, ARJ and PKZIP 2.x are based on the same ideas and perform similar (all are based on a huffman encoding of the output of a LZ77 compressor with a sliding window. The window size is around 32 kilobytes). It might be a good idea to look at all of them to experience the command line interface, or the effect of a central directory at the end of file (PKZIP has it, ARJ and LHA don't). RAR is a step upwards, implementing pre-processing of x86 code and uncompressed media contents (WAV, BMP, ...) to improve compression, supporting "solid archives", supporting error recovery data to counteract failing floppies just to name a few technological advantages that made RAR beat the established #1 PKZIP and it's #2 counterpart ARJ. I'm not implying that the technologies implemented in RAR were implemented nowhere before (in contrary: .tar.gz is way older than RAR, and also provides a "solid archive"), but RAR managed to bring these techniques to DOS users in a convenient and easy to use fashion.

If we are looking for something that beats RAR in terms of compression ratio at the expense of speed, and still is 16-bit DOS software, we would need to investigate niche applications. I remember having heard of a compression program called X00, which already is a 32-bit DOS extender based compressor and I am unable to quickly find any good references. This captures a common pattern: If you want better compression, using more memory is a good way to achieve it, and RAR is already at the limit of what you can do in 16 bit DOS software. You would need drastically better algorithms to beat RAR as 16-bit DOS software, and those algorithms turn out to be too slow for DOS machines.

On the other hand, if speed and simplificity of the algorithm would be the main focus, a look at the LZO algorithm and the UCL compression library in UPX.

Reply 4 of 9, by Harry Potter

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I can use DOSRAR. My compression technique is very slow, but that's mainly because I'm not doing so well with LZ77: I need desperately to implement hash tables. It does a lot of other work, so, when I'm finished, it must still be slower. I am also working on an 8-bit technique that is to be open-source and faster at a significant price in compressibility, but it's not good enough. 🙁

Joseph Rose, a.k.a. Harry Potter
Working magic in the computer community

Reply 5 of 9, by Jo22

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There also was ARC, which was superseded by LHA (LHarc; LZH), ARJ and finally, in the western hemisphere, ZIP.

https://en.wikipedia.org/wiki/ARJ

https://en.wikipedia.org/wiki/ARC_(file_format)

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Reply 6 of 9, by Azarien

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There was also JAR, not the Java one but one by ARJ Software.
I remember it having very good compression ratio.

http://www.arjsoftware.com/jar.htm

Reply 7 of 9, by Zup

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I remember other called AIN, almost as efficient as RAR.

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Reply 8 of 9, by elszgensa

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There's also ACE (bit of a shitty search term on its own, so use "WinACE" as a starting point instead when trying to find the DOS version). And Microsoft's CAB format - which wasn't intended to be used as a standalone compressor, so the experience might not be ideal; also, while I know there's a DOS decompressor I'm not 100% on whether we can create them outside of Windows. Have a look at the CAB SDK.

Reply 9 of 9, by BloodyCactus

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HA. 7zip has a dos port (pmode tho). ha is very good. Ive also used hap/pah (hap3/pah3) for some time too.

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