LHA (file format)

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LHA is a compression program and associated file format for file archiving. The methods are based among other things on the Lempel -Ziv - Storer - Szymanski algorithm ( LZSS ) and the LHA - source texts themselves are the basis for, inter alia, the Deflate algorithm. LHA is the successor of LHarc.

. File name extensions: lzh ( cross-platform ), lha (Amiga ). MIME Type: application / x- lzh -compressed

Compression methods

The file format allows the use of various methods to pack, usually different versions of the LH algorithm with differences in

  • Dictionary size (up to 4k at LARC, up to 64k at LHA )
  • Maximum word length ( LARC: 17, LHA: 60, 256),
  • The height of the limit value of the LZSS algorithm ( 2, 3) and
  • Static or dynamic Huffman:

LARC methods: - lzs -,- lz2 -,- LZ3 -,- ​​LZ4 -,- LZ5 -,- LZ7, - LZ8 -; LHA methods: - LH0 -,- lh1 -,- lh2 -,- LH3, LH4 -,- LH5 -,- LH6 -,- lh7 -,- lhd -; - LH8 -,- LH9 -,- lha, lhb, - lhc -,- LHe; - lhx -; PMarc methods: - pm0 -,- pm2 -

History

The format was (吉 崎 栄 泰, Yoshizaki Haruyasu ) with the help of Professor Haruhiko Okumura from Matsusaka University for his compression program LHarc designed in 1988 by Haruyasu Yoshizaki.

The starting point was the Pack program LARC of another author. Originally called the program LHarc. A completely rewritten version was provisionally called LHX and eventually published as LH. In order not to interfere with the then new same command "load high" of MS- DOS 5.0 in conflict, it has been renamed to LHA.

Getting greater popularity did not recover LHarc itself, but disseminated in mailbox networks, manipulated version called LHice. She was virtually identical to LHarc, but the ending of the created files was. " Ice", and in the progress bar has been issued " freezing" or "melting " instead of " packing" and " unpacking ". In the next version soon LHarc 2.0 such manipulations were hampered by encrypting the program internal text strings. Nevertheless, also emerged from LHarc 2.0 on a hacked version, which was called " FOOBAR " ( " Florian Orjanov 's and Olga 's Bachetzka archiver " ) and archives with the file extension ". Foo" generated.

The format used by id Software to compress the installation files of their early computer games such as Doom. LHA has been ported to many operating system environments on the Amiga and is the most widely used archive format, especially on Aminet.

The LHA format is indeed rarely used today in Europe and the U.S., but is still very popular in Japan. The company Microsoft has released an extension for compressed folders in LHA format for your operating system Windows XP in Japan.

Y2k11 bug

Timestamp since the year 2011 will be set to 1980, this error requires a patch of the Pack program.