5. What's with the .rar, .r00, etc. files?

Archive Formats

What are .RAR, .R00, R01...Rnn AND part01.RAR...partnn.RAR files? (The RAR Archive Format) [Original Contributors, ed.]

RAR files are compressed/split archives. Nearly everything in the newsgroups is posted in this format. This is done to make successful download much more likely and it makes reposts much easier. The files in both ABA and ABMA usually run from 50 MB+, and if these files were posted in a single post and even one part doesn't make it to somebody's server, the file is useless. When the files are split up, the chances of the individual files arriving intact are greater. Also, even if some of the parts didn't make it, the poster only needs to repost one small part to fill it. Furthermore, RAR archive sets can be created with a recovery record which allows RAR parts, when damaged in certain ways, to be repaired by the RAR program itself.

To decompress (dearchive) these archive sets, one must have every single part of the set. Use a RAR program to "unrar" these files.

RAR programs can be found at: http://www.rarsoft.com for all major platforms, http://macrar.free.fr for Macs. StuffIt Expander is capable of simple dearchiving for Macs, as well.

Posting unarchived files, or files archived in a non-RAR format (especially an uncommon one) is rather seriously frowned upon due to the negative impact on the groups. Continuing to pursue this course after being warned could result in letters explaining the abuse to the poster's news provider.

Because multimedia files, especially those of newer formats such as MPEG-4, are already internally compressed, the compression of such files may give poorer results than one might hope. In those cases, the file should not be posted unarchived. Instead, archive the set with no compression. This causes the archiving and dearchiving process to go very quickly, because no compression is performed, but the other advantages of archiving, file splitting and file recovery, remain intact.

There are two principle kinds of error messages as you unrar a file:

1. Invalid or corrupt authenticity information. In this case, it merely means that the poster used an unregistered version of WinRAR with authenticity information enabled, so that the error recovery data is not saved. Usually this is not a problem and the file should extract just fine. Unless if the files fail the crc check when checking with SFV, in which case recovery method will not work and another repair method or replacement of the file is needed.
2. CRC error. In this case the files are actually damaged. Check the file size against the other files of the same archive. Sometimes it is possible to repair the file if the error recovery data is present. Other times, especially if the file is short by a few bytes, repair will not be possible.

With the release of WinRAR 3.0, the author of WinRAR decided to use a new naming scheme for RAR parts. Instead of naming them .rar, .r00, r01...rnn, version 3 and greater will default to naming them .part01.rar, .part02.rar...partnn.rar. This behavior can be turned off when the archive set is created. (Under the Advanced tab, in the group entitled Volumes, enable Old Style Volume Names.) Currently, it is preferred group behavior to use the old-style volume names, but this is, as always, at the discretion of the poster. The primary reason for this is that some OSes other than Windows reportedly have issues with the new names.

Yet another good reason to use RAR archiving is the recovery record that can be included in the RAR file. In WinRAR, highlight the affected R?? file, select the Commands menu and click Repair Archive. Then rename the resulting archive to the name of the corrupted archive (after first renaming or moving the corrupted archive). If the archiver did not include recovery information, then it will try to reconstruct the archive. This is not the same as recovery and has a much lower chance of success (actually 0% usually, in the case of split files).

As of version 3.10 of RAR, recovery records have been vastly improved. The RARSoft applications can now repair files that have missing data and other damage that was previously unrepairable. This significantly escalates the need for all posters to include at least 1% RAR Recovery Records.

There are some reports that the repair via recovery records no longer works in MacRAR.

When the recovery record is unable to repair the RAR part, there are further steps you can take to repair the file. T. Rieper's excellent article explaining multiple steps that can be taken to repair RAR files can be found at http://riepersnest.tripod.com/rar/index.htm.

Please note that RAR recovery records are not the same as RAR recovery volumes, which are described in the support section under recovery volumes.

What are .ACE, .C00, .C01...Cnn files? (The ACE Archive Format) [xo]

Files with extensions of the type .ace, .c00, .c01 are archive segments produced by WinACE, available at http://www.winace.com. A utility called unace is also available in source form for *nix operating systems at http://www.ibiblio.org/pub/Linux/utils/compress/unace-1.2b.tar.gz

WinACE is functionally equivalent to the RAR family of programs; however it uses it's own format, which is different and incompatible with the RAR format. Note that ACE-format archives can only be produced under Windows and can only be uncompressed under Windows and certain *nix operating systems.. Users of other platforms, most notably Macintosh (unless unace compiles under OS X), are unable to unarchive ACE formatted files. For compatibility's sake, the use of ACE is discouraged.

What are .000, ,001...nnn files? (Numeric extensions) [Keikai]

Unfortunately, files with three-digit numerical extensions do not belong to only one form of archiving. The two primary forms these files will take are:

• Split files
• RAR files

Split files are created using one of several splitting applications. These utilities simply break the file up into "chunks" of a specified size. No changes of any kind are made to the data. The slight advantage of these files are that they do not require any third-party application to recombine. Proper use of the copy command in the operating system can rejoin these files. However, split files should NOT be posted to AB(M)A. Split files offer no form of protection against corruption, and, because of the nature of usenet, this puts them at a significant disadvantage. If a poster for some reason must post material in split form, then they must also create a set of parchive files. There are several methods of rejoining a split file:

• (Windows Command Prompt) copy /b splitfile.000 + splitfile.001 + splitfile.002 + ... + splitfile.nnn
• (Linux/*NIX Prompt) to be added later
• MasterSplitter
• DecompressionChamber
• more to be added later

RAR files can be created using the standard rarring applications to use the three-digit numerical extension. These files are proper RAR files and are no different from RAR files with the more common extensions (.rar, .r01, part00.rar, etc.). Because of the ambiguity caused by this extension, however, RAR files that are named using simply a three-digit numeric extension should NOT be posted to AB(M)A.

The determine which of the two possible formats a file may be, one should open the first file (usually .000) in WinRAR or the appropriate RAR application for an operating system. If an error occurs, it is likely that the file is part of a set of split files. If it opens properly, treat it as any other RAR file for decompression. Unfortunately, if an error occurs when opening in the RAR utility, it may also indicate that the file is simply corrupt. If no form of data integrity checking is available with the post (.par, .sfv, .md5) then it will be necessary to request a repost from the original poster.

What about .ZIP files? (The ZIP Archive Format) [Keikai]

User Contributed Notes