What is a RAR file?

Russian born and a graduate of the Chelyabinsk Technical University, Eugene Roshal originally developed RAR compression and decompression software for the DOS command line. While not incredibly feature rich, these original versions of RAR had an exeptional level of compression, taking full advantage of the growing computing power of the modern personal computer. His software was so well regarded that it was soon ported to other platforms so that others could take advantage of his hard work. As Windows became a more popular operating system, Roshal created a version of the encoder with a GUI called WinRAR. While WinRAR was distributed with a shareware license, the decoder was released using an open source license, simply precluding the use of the source code to create a competing encoder.

What about ZIP?

ZIP is a much earlier compression algorithm than RAR. RAR supports much higher levels of compression, at the cost of a higher compression time. Both have their place. As most Windows users have noticed, ZIP can be uncompressed on the fly or natively with Windows XP and higher, while RAR requires a special download and by default is simply an unknown file type. RAR on the other hand, as already mentioned, has a much higher level of compression, and as explained in further detail below, supports a great array of features.

Some features to note

RAR can do what is called 'solid format'. Basically this means that instead of compressing each file in the archive separately, with a separate dictionary in a lot of cases, RAR will instead stick all these files together sequentially, and treat it as a big block of binary data. This can make a really big difference in the compression efficiency and overall effectiveness of the compression scheme.

Ever had a CRC error? This is actually a 'Cyclic Redundancy Check' error, which means basically that what you are dealing with is a corrupted data source. RAR archives can have a variable amount of redundancy information, which do inflate the RAR-ed file size somewhat, but make it possible to resist a large amount of corruption if this option is chosen.

Encryption abilities in RAR are quite impressive - the newest versions of WinRAR support a popular encryption algorithm called AES. This algorithm is currently known to only be compromised via brute force attacks, which with some careful passwords, be impossible to crack in a reasonable amount of time.

RAR can specialize based on the type of file that it is receiving. It has terrific audio compression which is only slightly bested by dedicated compression schemes like FLAC.

RAR can store security information on NTFS filesystems, which greatly enhances its usefulness to system administrators, power users, and security conscious users.

Finally, perhaps the most useful feature for the average user, and certainly something that the filesharing community takes full advantage of; out of the box RAR will handle split volumes. This is a process where the final archive is split into chunks to make transmission and storage of all the information much more convenient.

Bottom line: should I use it?

While RAR and its attendant application WinRAR are far more technically advanced than most other compression systems, one can never be sure if WinRAR will be on the target machine. In a Windows environment - that is, the environment most people work in - ZIP is a much more user friendly format. It is natively decompressed via Windows, making it a very simple compression algorithm to use.

If you plan to distribute large data sets, or are comfortable installing software and guiding others through this same software installation, feel free to go get it.

Thanks for reading, I hope you found this article useful.

Good luck!

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