CPIO to ARJ Converter

ARJ (Archived by Robert Jung) is a compressed archive format created by Robert K. Jung in 1991 for MS-DOS, which became one of the most popular archiving tools during the early 1990s. The format uses a proprietary compression algorithm based on LZ77 sliding window techniques combined with Huffman coding, offering competitive compression ratios that rivaled or exceeded other DOS-era archivers. ARJ archives support multi-volume spanning across floppy disks, a critical feature in an era when distributing software often meant shipping multiple 1.44 MB diskettes. The format also provides password protection, file attribute and timestamp preservation, archive integrity verification through CRC-32 checksums, and the ability to create self-extracting executables. ARJ saw widespread adoption on bulletin board systems and in corporate environments during the DOS and early Windows period, valued for its balance of compression ratio, speed, and feature set. One advantage was excellent multi-volume support — ARJ handled spanning across floppy disks more reliably than many competitors, making it a preferred choice for software distribution via physical media. The self-extracting archive capability provided another practical strength, enabling recipients to unpack files without needing the ARJ utility installed. While ARJ's usage declined sharply with the rise of ZIP, RAR, and 7Z as internet-based distribution replaced floppy disks, the format remains recognized by modern archivers like 7-Zip for extracting legacy archives.