LHarc

LHA

Filename extension	.lzh, .lha
Internet media type	application/x-lzh-compressed
Type code	"LHA " (L-H-A-SPACE)
Uniform Type Identifier (UTI)	public.archive.lha
Developed by	Haruyasu Yoshizaki (Yoshi)
Type of format	Data compression

LHA is a freeware compression utility and associated file format. It was created in 1988 by Haruyasu Yoshizaki (吉崎栄泰, Yoshizaki Haruyasu^?), and originally named LHarc. A complete rewrite of LHarc, tentatively named LHx, was eventually released as LH. It was then renamed to LHA to avoid conflicting with the then-new MS-DOS 5.0 LH ("load high") command. According to early documentation, LHA is pronounced like La.

Although no longer much used in the West, LHA remains popular in Japan. It was used by id Software to compress installation files for their earlier games, including Doom and Quake. LHA has been ported to many operating systems, and is still the main archiving format used on the Amiga computer, although it competed with LZX in the mid 1990s. This was due to Aminet, the world's largest archive of Amiga related software and files, standardising on Stefan Boberg's implementation of LHA for the Amiga. Microsoft has released a Windows XP add-on, Microsoft Compressed (LZH) Folder Add-on, designed for the Japanese version of the operating system. The Japanese version of Windows 7 ships with the LZH folder add-on built-in. Users of non-Japanese versions of Windows 7 Enterprise and Ultimate can also install the LZH folder add-on by installing the optional Japanese language pack from Windows Update.

In an LZH archive, the compression method is stored as a five-byte text string. These are the third through seventh bytes of the file.

LHarc compresses files using an algorithm from Yoshizaki's earlier LZHUF product, which was modified from LZARI developed by Haruhiko Okumura (奥村晴彦, Okumura Haruhiko^?), but uses Huffman coding instead of arithmetic coding. LZARI uses Lempel–Ziv–Storer–Szymanski with arithmetic coding.

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