Down loaded ARC files...

[fujidude]

Works great! Thanks a lot!

 

Glad I could help. The head scratcher for me is, why the hell otherwise top notch software like 7Zip etc., not properly handle the full ARC specification.

[+Nezgar]

Glad I could help. The head scratcher for me is, why the hell otherwise top notch software like 7Zip etc., not properly handle the full ARC specification.

The same reason everyone else dropped ARC like a hot potato i guess... the creator for ARC sued for using the freely available source code, the ARC filename, and the 'look and feel' of the program.

 

Good archive here: http://www.bbsdocumentary.com/library/CONTROVERSY/LAWSUITS/SEA/

 

Quoting one page from CompuServe 15-Sep-88:

PKARC has suddenly become a lot less attractive as it will not be supported  
after Jan. 1989.  We might not see any more updates at all considering that  
SEA has filed an obnoxious legal action against PKWARE when they came out  
with PK*** 3.61.

http://www.bbsdocumentary.com/library/CONTROVERSY/LAWSUITS/SEA/excerpt.cis

 

Seems another element was the .ARC files created by PKARC created compatibility issues since it added 'Squash' compression that was incompatible with SEA ARC... creating a mess of the ARC 'standard'

[fujidude]

The same reason everyone else dropped ARC like a hot potato i guess... the creator for ARC sued for using the freely available source code, the ARC filename, and the 'look and feel' of the program.

 

Good archive here: http://www.bbsdocumentary.com/library/CONTROVERSY/LAWSUITS/SEA/

 

Quoting one page from CompuServe 15-Sep-88:

PKARC has suddenly become a lot less attractive as it will not be supported  
after Jan. 1989.  We might not see any more updates at all considering that  
SEA has filed an obnoxious legal action against PKWARE when they came out  
with PK*** 3.61.

http://www.bbsdocumentary.com/library/CONTROVERSY/LAWSUITS/SEA/excerpt.cis

 

Seems another element was the .ARC files created by PKARC created compatibility issues since it added 'Squash' compression that was incompatible with SEA ARC... creating a mess of the ARC 'standard'

 

 

Certainly not everyone dropped it. As I said, there are utilities which claim to support the format, and almost completely do; just not quite. Your argument should mean that they offer no support for it. Could it be that they feel it is good enough because almost everyone only uses less antiquated revisions anyway? I don't claim to know the answer, but fear of SEA et al doesn't fit real well from where I sit; but maybe.

Edited November 10, 2018 by fujidude

[+MrFish]

Watch this: BBS Documentary - Compression

 

BTW, I recommend for anyone interested in BBS's (and even if you're not into BBS's) to watch the entire documentary.

It's a very comprehensive overview, and you'll be one happy nerd if you do watch it.

 

I have a copy of it on my machine, and I've watched it about 4 or 5 times, all the way through, over the years. It has great

info on FidoNet, which I find totally fascinating.

Edited November 10, 2018 by MrFish

[phaeron]

A simpler explanation is that the ARC file format is an obsolete format that is hard to find complete information on and Atari .ARC files use methods that were obsolete even back when ARC and PKARC were still maintained. It's the same with old PC formats. There are plenty of utilities that can generally extract DOS disk images, but give them a 160K MS-DOS 1.0 disk image and they barf.

 

Then there's the issue of readily available documentation being inadequate or just wrong, at least for Atari ARC. "Repeated running length encoding" doesn't even usably describe the simplest compression mode in the format, much less the more complex Huffman and LZW modes, the latter of which has a weird quirk compared to the commonly understood GIF variant. Also, method $08 is not adaptive Huffman, it is packed + LZW.

[fujidude]

A simpler explanation is that the ARC file format is an obsolete format that is hard to find complete information on and Atari .ARC files use methods that were obsolete even back when ARC and PKARC were still maintained. It's the same with old PC formats. There are plenty of utilities that can generally extract DOS disk images, but give them a 160K MS-DOS 1.0 disk image and they barf.

 

Then there's the issue of readily available documentation being inadequate or just wrong, at least for Atari ARC. "Repeated running length encoding" doesn't even usably describe the simplest compression mode in the format, much less the more complex Huffman and LZW modes, the latter of which has a weird quirk compared to the commonly understood GIF variant. Also, method $08 is not adaptive Huffman, it is packed + LZW.

 

And still you managed to pull it off! I'm very highly impressed with your programming knowledge and skill anyway, so maybe that isn't saying much. But Mr. Chu's ARC for Linux, Universal Extractor, and perhaps others somewhere also manage to handle the old ARCs despite documentation shortcomings. I figure Igor Pavlov (7Zip) and others just don't care enough to bother with the fringe obsolete variants of the format as you say, but I'll bet that like you, they could make it happen if they set to it.