ARC to LHA Converter

LHA (originally LHarc) is a compressed archive format created by Haruyasu Yoshizaki (known online as Yoshi) in May 1988, combining Lempel-Ziv) sliding-window compression with Huffman coding for efficient data reduction. The format achieved enormous popularity in Japan, where it became the dominant archiving standard throughout the late 1980s and 1990s — virtually all Japanese software distribution, from commercial applications to BBS file sharing, relied on LHA archives. The format stores files with per-entry headers containing filename, timestamps, OS-specific attributes, and CRC-16 checksums, using various compression methods designated by two-character codes (lh0 through lh7, with lh5 being the most common general-purpose algorithm). LHA's compression algorithms were influential beyond the format itself: the lh5 method's approach to combining LZSS with static Huffman coding was adopted by the Deflate algorithm used in ZIP, gzip, and PNG. One advantage is the format's historical efficiency — LHA offered strong compression ratios with modest CPU requirements, critical on the relatively slow processors of its era. The format's deep cultural impact in Japanese computing is another notable aspect: LHA was freely distributed, contributing to its ubiquitous adoption across the Japanese software ecosystem. While modern formats have superseded LHA for new archives, it remains relevant for accessing Japanese software archives and retro computing collections, with extraction supported by 7-Zip and other contemporary tools.