RAR is a technique for compressing files and splitting them into multiple pieces. It is widely used for posting large files because they can be split into a set of reasonably sized segments. RAR files are similar to ZIP files in the sense that they are compressed archives that must be decompressed before you can access their contents. But RAR files are better suited for compressing large files for Usenet posting because they are designed to be split into multiple volumes.

Prior to RAR version 3.0, segments of RAR file sets had names ending with .rar, .r00, .r01, .r02, etc., so a full file posting might have file names like file.rar, file.r00, file.r01, etc. This format is still widely used.

Beginning with RAR version 3.0, a new naming convention was introduced that adds two extensions to the file name; the first indicates the part number, and the second is always ".rar". A typical file posting will have segments with names such as file.part01.rar, file.part02.rar, file.part03.rar, etc. RAR version 3.0 also introduced error recovery files with extensions of .rev, but they are rarely used because PAR files are preferred.

What are PAR files?

Often, a set of PAR files is posted accompanying an RAR file set. PAR files are parity recovery files that can be used to recovery missing or corrupted segments of an RAR file set. The PAR files usually have names such as file.part01.p01, file.part01.p02, etc.; you may also see file.part01.par, but generally PAR files begin with .p01.

If all of the segments of a RAR file set are present and valid, you do not need any of the PAR files. However, if any RAR segment is missing or corrupted, it can be recovered by using a PAR file. It takes one PAR file to recover each missing or damaged RAR segment. So if a file is posted with 10 PAR sections, up to 10 damaged or missing RAR segments can be recovered. The only exception to this is the PAR segment with the .par extension. The .par file is optional and contains only information about what files are part of the set; it does not contain recovery information. Usually, .par files are not used; they are never needed. The actual recovery PAR files begin with .p01.

PAR files are independent of each other, so a missing or damaged PAR segment will not affect the recovery as long as there are enough good PAR files to replace missing and damaged RAR files.

Version 2 PAR files have extended file names of the form "name.volnn+mm.par2". With PAR version 2, one PAR volume can be used to recover more than one missing/damaged RAR volume, and the valid portion of a damaged RAR volume can be used in the recovery process. News Rover supports both version 1 and version 2 PAR files.

News Rover support for and RAR and PAR files

News Rover is the ideal tool for downloading RAR and PAR files from Usenet newsgroups. News Rover "understands" RAR file sets so it can check and tell you if all of the segments are present or if there are enough PAR segments to replace missing RAR segments. News Rover also has a built-in decompressor for RAR files and a built-in PAR processor for recovering missing RAR files, so you don't have to buy or use any other programs to extract the contents of RAR archives. With News Rover, it is as easy to download RAR files as JPG files. News Rover can handle both version 1 and version 2 PAR files.

How to download and decompress RAR and PAR files

First, download the list of messages available in the group. You can get the list of messages using a subscribed newsgroup, an Autoscan Interest Group or using the File Attachment Locator features.

If the message list is downloaded from a subscribed newsgroup or a header-only Autoscan Interest Group, News Rover automatically "threads" the sections of the RAR/PAR file set. You will see one line in the message list that represents the entire set of RAR sections -- possibly representing throusands of individual messages. You can simply double-click the message entry to start the RAR download.

If News Rover does not thread the RAR sections into a single line, you can manually start the RAR download and decompression. To do this, right click on the entry for any of the segments to bring up a popup menu. Then left click on the entry in the popup menu "Download and decompress RAR archive". News Rover will then scan the message list and determine how many RAR and PAR segments are part of this file set.

If all of the RAR segments are complete, News Rover will display a screen that looks like this:

This screen tells you how many sections there are to the RAR archive and how many individual messages (generally, each segment is made up of several messages). It also tells you how many PAR sections are present. There are two option checkboxes that you can select:

"Download PAR sections as well as RAR sections" -- If PAR sections are available, this option will be enabled. If you check the box, News Rover will download the PAR sections as well as the RAR sections. This is recommended because News Rover can use the PAR sections to recover missing or damaged RAR sections.

"Combine and decompress when downloads finish" -- If you check this box, News Rover will begin automatically to combine and decompress the segments of the RAR file set as soon as the downloads finish. Note, if you stop News Rover and restart it, pending RAR decompressions are forgotten and you will have to use the manual method described below to combine and decompress the RAR files.

The screen has three buttons:

"Start downloading RAR archive now" -- Click this to cause News Rover to immediately begin downloading all of the segments of the RAR archive.

"Mark RAR files for later download" -- Click this to cause News Rover to "tag" the files that are part of the RAR archive for later download. A down-arrow icon will appear to the left of each file that has been marked for download. When you are ready to start the downloads, click the downward-pointing arrow icon on the News Rover toolbar.

"Delete all parts of this RAR archive" -- News Rover will delete all sections of the RAR archive from the message list.

"Cancel" -- Click to exit the screen without downloading any files.

If any of the sections of the RAR file set are missing, News Rover will display a screen like this:

This screen tells you how many RAR sections there are and how many are missing. It also tells you if there are enough PAR sections to recover the missing RAR sections. It has the same set of options and buttons as the screen shown when all of the sections are present.

If News Rover is able to successfully decompress the RAR archive, the segments are deleted and a message is added to the message list for the group with the full, decompressed file(s) from the archive attached to it. You can then launch that attachment or save it just as you would any other attachment that you downloaded. If the RAR archive cannot be decompressed, News Rover leaves the messages with the RAR segments.

Manually decompressing an RAR file set

The easiest way to decompress an RAR file set is to check the box labeled "Combine and decompress when downloads finish" on the screen where you start the download. However, if you have downloaded the RAR segments without combining them, you can manually invoke the News Rover RAR decompressor. To do this, right click on one of entries in the message list that has a downloaded RAR segment. Then click "Combine/Decompress..." on the popup menu followed by "Decompress RAR archive" on the secondary popup menu.

How to create RAR file sets and PAR files

News Rover is not able to produce RAR and PAR files. To do that you need two programs: WinRAR and QuickPAR. WinRAR is a commercial program for decompressing and creating RAR files. An excellent free program for using and creating PAR files is QuickPAR.

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