RAR (file format)
RAR is a proprietary archive file format that supports data compression, error recovery and file spanning. It was developed in 1993 by Russian software engineer Eugene Roshal and the software is licensed by "win.rar GmbH". The name "RAR" stands for "Roshal Archive". File format. The filename extensions used by RAR are codice_1 for the data volume set and codice_2 for the recovery volume set. Previous versions of RAR split large archives into several smaller files, creating a "multi-volume archive". Numbers were used in the file extensions of the smaller files to keep them in the proper  sequence. The first file used the extension codice_1, then codice_4 for the second, and then codice_5, codice_6, etc. RAR compression applications and libraries (including GUI based WinRAR application for Windows, console rar utility for different OSes and others) are proprietary software, to which Alexander L. Roshal, the elder brother of Eugene Roshal, owns the copyright. Version 3 of RAR is based on Lempel-Ziv (LZSS) and prediction by partial matching (PPM) compression, specifically the PPMd implementation of PPMII by Dmitry Shkarin. The minimum size of a RAR file is 20 bytes. The maximum size of a RAR file is 9,223,372,036,854,775,807  (2−1) bytes, which is about 9,000 PB. Versions. The RAR file format revision history: Software. Operating system support. Software is available for Microsoft Windows (named WinRAR), Linux, FreeBSD, macOS, and Android; archive extraction is supported natively in Chrome OS. WinRAR supports the Windows graphical user interface (GUI); other versions named RAR run as console commands. Later versions are not compatible with some older operating systems previously supported: Creating RAR files. RAR files can be created only with commercial software WinRAR (Windows), RAR for Android, command-line RAR (Windows, MS-DOS, macOS, Linux, and FreeBSD), and other software that has written  permission from Alexander Roshal or uses copyrighted code under license from Roshal. The software license agreements forbid reverse engineering. Third-party software for extracting RAR files. Several programs can unpack the file format. Other uses of "rar". The filename extension "rar" is also used by the unrelated Resource Adapter Archive file format.