PAR is an abbreviation for Parity ARchive. PAR and PAR2 files are used to repair and replaced damaged or missing files found on Usenet. Unlike the World Wide Web, files on Usenet do not travel in a straight line, instead files / messages are passed from Usenet server to Usenet server of varying file storage capacities (Retention). As a result of this travel and different server capacities, often parts of a Usenet message will go missing. These missing files in Usenet terminology are called incompletes.
Par2 files and Par (less common) come to the rescue here and help solve the problem of incomplete messages.
How To Use Par Files
Probably first you are interested, in how to use par2 files to repair or replace a missing or broken file.Â The good news is that it is pretty easy to do, if you install the right program.
Here is a chart of the best programs for working with Par2/ Par Files.
|QuickPar||http://www.quickpar.org.uk/||Windows||Excellent program to restore and make Par2/Par files. Available in many languages. Freeware.|
|MacPar Deluxe||http://www.xs4all.nl/||Mac OSX||Best Mac OSX program to work with PAR2 and PAR files. Freeware.|
|Parchive||http://parchive.sourceforge.net/||Linux, Mac OSX, Windows||Basic non GUI program to open PAR files. Freeware|
Here we use the example of the best windows program for opening par files – QuickPar. Be sure to associate PAR2 and PAR2 files , with QuickPar. Also if you download Usenet binaries often, then consider integrating QuickPar into the windows shell.
How To Open Par Files
In the case of QuickPar, we install and associate Par2/Par files with QuickPar then we double click on the Par2 file to initiate the process of file repair or restoration.
In this picture above, we see that we are missing three blocks. In this case we would want to download a few more PAR2 files and then double click once again until we see the text that says ready to recover.
One nice thing about QuickPar is that is available in many different languages – see here – http://www.quickpar.org.uk/Download.htm is that they are available in many different languages.Â So its easy to open par files.
PAR was the original standard for replacing reconstructing missing Usenet binary files. PAR, however, had several limitations and was shortly replaced by the improved PAR2 format.
The Par algortihm works by using checksums.
An example: Pretend you have the following numbers: 1 2 3 4. The checksum for these numbers would be 10. (1+2+3+4=10). If number 3 goes missing you can still figure out what is missing by knowing the checksum of 10. 10-1-2-4 = 3. The Par2/Par alogorithms are based on these principles.
If you are interested more technical details then check out the sourceforge project – http://parchive.sourceforge.net/ otherwise install and use the recommended PAR2 program after downloading binaries from Usenet to make sure that the file you have downloaded is not corrupt nor missing a file.
PAR2 and PAR differences
Listed below is a listing of key differences between PAR and PAR2 files.
|Damaged files can be repaired. A small error in a big file requires a small Par2 file to fix.||Damaged files can not be repaired. A small error in a big file requires a large PAR file to fix.|
|Can handle/repair up to 32768 files||Can handle/repair up to 255 files|
|More CPU required||Less CPU required|
A par file does this by virtually splitting the files you wish to protect. For more technical details on the differences see here: http://www.quickpar.org.uk/AboutPAR2.htm