Tar relates to a file format widely used in UNIX environments, identified with the extent of tar. It also refers to the program for managing files that are standard in these environments. The format was designed to store files in a convenient form on magnetic tape and then comes its name, which stands for "tape archive". Due to this origin the format is ready to be processed linearly, without a way to remove a member without traversing the entire file to find it. Initially developed to write data to I / S sequential devices for purposes of backup tape, tar is used today to collect many files into one larger for distribution or archive file, while preserving the information system files, such as user permissions and group dates, and directory structures.
In computing, RAR is a proprietary file format, a lossless compression algorithm used for data compression and archiving, developed by the Russian software engineer Eugene Roshal. RAR uses a compression algorithm based on the LZSS which, in turn, is based on the LZ77, Thomas James Storer and Szymanski (1982). The dictionary size can vary between 64k and 4 Mb. The RAR is slower than ZIP, but has a higher compression ratio. RAR Another feature is that it has a better ZIP data redundancy. The format also allows what is known as a solid compression for compressing several files together, so that a single dictionary applies to all information, so that the compression is greater.