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ARC is a lossless data compression and archival format by System Enhancement Associates (SEA). It was very popular during the early days of networked dial-up BBS. The file format and the program were both called ARC. The ARC program made obsolete the previous use of a combination of the SQ program to compress files and the LU program to create .LBR archives, by combining both compression and archiving functions into a single program. Unlike ZIP, ARC is incapable of compressing entire directory trees. The format was subject to controversy in the 1980s—an important event in debates over what would later be known as open formats. The .arc file extension is often used for several file archive-like file types. For example, the Internet Archive uses its own ARC format to store multiple web resources into a single file. The FreeArc archiver also uses .arc extension, but uses a completely different file format. Nintendo uses an unrelated 'ARC' format for resources, such as MIDI, voice samples, or text, in GameCube and Wii games. Several unofficial extractors exist for this type of ARC file. ==History== In 1985, Thom Henderson of System Enhancement Associates wrote a program called ARC,〔(Phil Katz )〕 based on earlier programs such as ar, that not only grouped files into a single archive file but also compressed them to save disk space, a feature of great importance on early personal computers, where space was very limited and modem transmission speeds were very slow. The archive files produced by ARC had file names ending in ".ARC" and were sometimes called "arc files" as a result. The source code for ARC was released by SEA in 1986 and subsequently ported to Unix and the Atari ST in 1987 by (Howard Chu ). This more portable code base was subsequently ported to other platforms including VAX/VMS and IBM System/370 mainframes. Howard's work was also the first to disprove the prevalent belief that Lempel-Ziv encoded files could not be further compressed. Additional compression could be achieved by using Huffman coding on the LZW data, and Howard's version of ARC was the first program to demonstrate this property. This hybrid technique was later used in several other compression schemes by Phil Katz and others. Later, Phil Katz developed his own shareware utilities, PKARC and PKXARC, to create archive files and extract their contents. These files worked with the archive file format used by ARC, and were significantly faster than ARC on the IBM-PC platform due to selective assembly-language coding. Unlike SEA, which combined archive creation and archive file extraction in a single program, Katz divided these functions among two separate utilities, reducing the amount of memory needed to run them. PKARC also allowed the creation of self-extracting archives, which could unpack themselves without requiring an external file extraction utility. Following the ''System Enhancement Associates, Inc. vs PKWARE Inc. and Phillip W. Katz'' lawsuit, SEA withdrew from the shareware market and developed ARC+Plus.〔(Article: ARC+Plus 7.12. (Software Review) (one of seven evaluations of data compression utility programs in 'Space Savers: Data Compression Utilities') (Evaluation) )〕 This version included a full-screen user interface, with the last known version being 7.12.〔(Packing Test for Pak/PKArc/PKZip/Zoo/LHArc/Hyper/ARJ/ARC )〕 SEA was eventually sold to a Japanese company in 1992. The ARC format is no longer common on PC desktops, but most antivirus scanners can still uncompress any ARC archives found in order to detect viruses within the compressed files. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ARC (file format)」の詳細全文を読む スポンサード リンク
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