The ARJ program by Robert K. Jung is a "newcomer" which compares well to PKZip and LhArc in both compression and speed. An ARJ archive contains two types of header blocks, one archive main header at the head of the archive and local file headers before each archived file. OFFSET Count TYPE Description 0000h 1 word ID=0EA60h 0002h 1 word Basic header size (0 if end of archive) 0004h 1 byte Size of header including extra data 0005h 1 byte Archiver version number 0006h 1 byte Minimum version needed to extract 0007h 1 byte Host OS (see table 0002) 0008h 1 byte Internal flags, bitmapped : 0 - no password / password 1 - reserved 2 - file continues on next disk 3 - file start position field is available 4 - path translation ( "\" to "/" ) 0009h 1 byte Compression method : 0 - stored 1 - compressed most 2 - compressed 3 - compressed faster 4 - compressed fastest Methods 1 to 3 use Lempel-Ziv 77 sliding window with static Huffman encoding, method 4 uses Lempel-Ziv 77 sliding window with pointer/ length unary encoding. 000Ah 1 byte File type : 0 - binary 1 - 7-bit text 2 - comment header 3 - directory 4 - volume label 000Bh 1 byte reserved 000Ch 1 dword Date/Time of original file in MS-DOS format 0010h 1 dword Compressed size of file 0014h 1 dword Original size of file 0018h 1 dword Original file's CRC-32 001Ah 1 word Filespec position in filename 001Ch 1 word File attributes 001Eh 1 word Host data (currently not used) ? 1 dword Extended file starting position when used (see above) ? char ASCIIZ file name ? char Comment ????h 1 dword Basic header CRC-32 ????h 1 word Size of first extended header (0 if none) ="SIZ" ????h+"SIZ"+2 1 dword Extended header CRC-32 ????h+"SIZ"+6 ? byte Compressed file (Table 0002) ARJ HOST-OS types 0 - MS-DOS 1 - PRIMOS 2 - UNIX 3 - AMIGA 4 - MAC-OS (System xx) 5 - OS/2 6 - APPLE GS 7 - ATARI ST 8 - NeXT 9 - VAX VMS EXTENSION:ARJ OCCURENCES:PC PROGRAMS:ARJ.EXE REFERENCE: SEE ALSO: VALIDATION:
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