RAR Archive

RAR is a proprietary archive file format that supports data compression, error correction 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 .rar for the data volume set and .rev 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 .rar, then .r00 for the second, and then .r01, .r02, 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 (2⁶³−1) bytes, which is about 9,000 PB.

Versions

The RAR file format revision history:
* 1.3 – the first public version, does not have the "Rar!" signature.
* 1.5 – changes are not known.
* 2.0 – released with WinRAR 2.0 and Rar for MS-DOS 2.0; features the following changes:
** Multimedia compression for true color bitmap images and uncompressed audio.
** Up to 1 MB compression dictionary.
** Introduces archives data recovery protection record.
* 2.9WinRAR 5.0 and RAR for Android refer to this format as RAR4. – released in WinRAR version 3.00. Feature changes in this version include:
** File extensions is changed from ''.rar, .r00, .r01, etc.'' to ''.part001.rar, .part002.rar, etc.''
** Encryption of both file data and file headers.
** Improves compression algorithm using 4 MB dictionary size, Dmitry Shkarin's PPMII algorithm for file data.
** Optional creation of "recovery volumes" (.rev files) for error correction, which can be used to reconstruct missing files in a volume set.
** Support for archive files larger than 9 GB.
** Support for Unicode file names stored in UTF-16 little endian format.
* 5.0 – supported by WinRAR 5.0 and later. Changes in this version:
** Maximum compression dictionary size increased to 1 GB (default for WinRAR 5.x is 32 MB and 4 MB for WinRAR 4.x).
** Maximum path length for files in RAR and ZIP archives is increased up to 2048 characters.
** Support for Unicode file names stored in UTF-8 format.
** Faster compression and decompression.
** Multicore decompression support.
** Greatly improves recovery.
** Optional AES encryption increased from 128-bit to 256-bit.
** Optional 256-bit BLAKE2 file hash instead of a default 32-bit CRC32 file checksum.
** Optional duplicate file detection.
** Optional NTFS hard and symbolic links.
** Optional Quick Open Record. Rar4 archives had to be parsed before opening as file names were spread throughout the archive, slowing operation particularly with slower devices such as optical drives, and reducing the integrity of damaged archives. Rar5 can optionally create a "quick open record", a special archive block at the end of the file that contains the names of files included, allowing archives to be opened faster.
** Removes specialized compression algorithms for Itanium executables, text, raw audio (WAV), and raw image (BMP) files; consequently some files of these types compress better in the older RAR (4) format with these options enabled than in RAR5.

;Notes

Software

Operating system support

Software is available for Microsoft Windows (named WinRAR), Linux, FreeBSD, macOS, and Android; archive extraction is supported natively in ChromeOS. 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:
* WinRAR v6.10 supports Windows Vista and later.
* WinRAR v6.02 is the last version that supports Windows XP.WinRAR Release History; RARsoft.
/ref>
* WinRAR v4.11 is the last version that supports Windows 2000.
* WinRAR v3.93 is the last version that supports Windows 95, 98, ME, and NT 4.0.
* WinRAR 2.06 is the last version to support Windows 3.1, Windows NT 3.1, Windows NT 3.5, Windows NT 3.51 and Win32s.
* RAR v3.93 is the last version that supports MS-DOS and OS/2 on 32-bit x86 CPUs such as 80386

HOME


Content is Copyleft
Website design, code, and AI is Copyrighted (c) 2014-2017 by Stephen Payne


Consider donating to Wikimedia



As an Amazon Associate I earn from qualifying purchases