Chinese name: RAR file mbth: Roshal ARchive introduction: a private file compression archiving format is used in: data compression archiving and packaging field: computer science application: file compression introduction, file format, opening tool, WINRAR, WinMount, 7-Zip, introduction RAR is a patented file format, used for file compression archiving and packaging. The full name of RAR is Rochard Archives (meaning "Rochelle Archives"), and its developer is Eugene Rochard. The first public version RAR 1.3 was published in 1993. Rochard originally wrote a Dos version of the RAR program to encode and decode files, and later the program was transplanted to other platforms, especially the transplanted version of Win RAR on the Windows platform. Eugene Rosa later published the source code of the decoder, but the encoder was still private. Because of its unique compression algorithm, RAR can basically achieve lossless compression, but also meet a high compression ratio and ensure a certain compression speed. However, RAR compression algorithm also has some defects. Because the RAR file header needs to occupy a part of space, the original data of the second file compression is smaller, and the compressed space is smaller, and the compressed file may be larger than the original file. RAR files have more redundant records, mainly because the compressed data is damaged during compression. In order to ensure lossless compression, there will be more recovery records and occupy a certain space. However, volume compression is a very prominent advantage of RAR, which divides the source file into several small files, thus facilitating the decompression of the source file. If all data are compressed into the same data area, the compression ratio can be greatly improved. However, when decompressing a single file, this compression method must decompress all files in the same data area before it, which is not conducive to independent decompression of files. RAR has a mature encryption algorithm. After version 2.0, AES algorithm is used for encryption. AES algorithm is difficult to crack, so it can only be cracked violently without password, which ensures the security of data to some extent. File format RAR file format is a proprietary compressed file format, and the specific design details are not completely disclosed. However, according to the published data, the RAR file is composed of a series of data blocks with variable length. In addition, there is no certain order between data blocks, but developers agree that each RAR file should start with a marked block and a compressed file block and end with an ending marked block. The beginning of each block starts with a public field, and the public field structure of each different block is the same. The types of these data blocks are different, and the information they carry and their functions in archives are also different. But all data blocks have a header with the same structure, which is called the basic block header. Different types of data blocks are formed by adding different fields after the basic block header. When calculating the file size, there are two different situations: when the first bit of the block mark "blockmark" is not set to 1, the value of the "Block Size" field is the total block size; When the block marker "block marker" is in the first position of 1 and the optional structure exists, the real block size is "block size+increase block size". The type and length of the fields in the tag block are fixed, and the value of each field is also fixed. The compressed file header is a data block, which is used to identify the related properties of the entire compressed file. Its structure is to add two reserved fields after the basic block header. The file header is a set of fields used to identify the related properties of compressed files in RAR. There are as many compressed files as there are blocks in the RAR. File format opening tool WINRAR RAR file is one of the most commonly used compressed files, which is opened and processed by WINRAR software. WinRAR is a 32-bit /64-bit version of RAR compressed file manager-a powerful tool that allows you to create, manage and control compressed files. There are a series of RAR versions, which are used in several operating systems, such as Windows, Linux, FreeBSD, DOS, OS/2 and MAC OS X. Introduction to WinMount: WinMount is a powerful Windows gadget with the functions of compressing, decompressing and browsing compression software, as well as mounting DVD, CD and virtual machine hard disk images. The biggest feature of WinMount is that it adopts a brand-new concept of compressed files-mount: directly mount compressed files on virtual disks without decompression, which breaks the tradition that compressed files can only be used after decompression. 7-Zip 7-Zip is an open source software. Most of the source code is distributed under the GNU LGPL license agreement. AES code is released under the license of BSD. The unRAR code is based on two licenses: GNU LGPL and UnRAR restricted license. You can use 7-Zip on any computer, including computers used for business purposes. If you don't donate or pay for 7-Zip, your use will not be affected. But you can support the future development of 7-Zip through donations. The latest stable version: 7-ZIP 4.65 (released on February 3, 2009) The main feature of 7-Zip is that the algorithm has been updated and the compression ratio of 7z format has been increased. Supported formats: compression and decompression: 7z, zip, GZIP, BZIP2 and TAR (RAR format is not supported because RAR is a commercial format). Only decompression: RAR, CAB, ISO, ARJ, LZH.