File Extension RAR
File extension RAR is used to denote a compressed archive using the proprietary RAR archiving format, which supports data compression, spanning and error recovery. Though less common, RAR files are also used to denote a Resource Adapter Archive, which is the specified format for the deployment of resource adapters, or connectors, on IBM's WebSphere Application Server.
The RAR compressed archive file format was originally developed by Russian Eugene Roshal, hence the file extension which was taken from Roshal ARchive. RAR files typically take longer to compress, though have a higher compression ratio than other popular archiving formats such as File extension ZIP or GZIP. The exact improvement in compression largely depends on the types of file being compressed. As well as data compression, RAR files support spanning, which means that archives can be split across multiple volumes. In this case, the first file in the archive will retain the RAR file extension, with subsequent volumes numbered in the form File extension R00 up to File extension R99. The entire archive can be browsed by opening the original RAR file. This was a particularly useful feature for compressing large volumes of data. Some RAR files may also contain a recovery volume, which allows the contents of an archive to be restored in the even of minor corruption. RAR archives also support password protection and strong 128-bit AES encryption algorithms.
Currently, RAR files can only be created using commercial software such as WinRAR or Squeeze, both of which are only available on Windows. The command-line version, RAR, can be used to create and extract archives on Windows, Mac, Linux and UNIX-based operating systems. However, RAR file can be opened and the contents extracted by several applications such as WinZIP, WinAce and Stuffit, courtesy of the freely available UnRAR source code from RARLAB which allows developers to incorporate RAR decompression into their applications.