*** ARC (compressed ARChive) *** Document revision: 1.4 *** Last updated: March 11, 2004 *** Compiler/Editor: Peter Schepers *** Contributors/sources: Chris Smeets (source code) The name is likely a shortened version of "ARChive". It is a direct relative of SDA, as SDA's are simply self-dissolving ARC files. ARC does not contain the dissolving code on the front of the file. Do not confuse these ARC files with C64 ARKive files (made with the ARKIVE program), or with PC .ARC files, as they are all completely different. Below is a dump of the first 48 bytes of an ARC file... 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII ----------------------------------------------- ---------------- 0000: 02 01 20 9D 47 01 00 01 00 50 01 41 FE 3A 21 FE ..G..P.A:! 0010: 00 01 FE 00 02 FE 03 02 A9 00 20 90 FF A9 02 A6 ..... 0020: BA A0 01 20 BA FF A9 04 A2 35 A0 02 20 BD FF A2 ..5. Byte: $00 - ARChive version $01 = original 02 = extended header 01 - Compression mode $00 - Stored 01 - Packed 02 - Squeezed 03 - Crunched (ARC version 2 only) 04 - Squeezed and packed (ARC version 2 only) 05 - Crunched in 1 pass (ARC version 2 only) 02-03 - Checksum (low/high format) 04-06 - Original file size in bytes (low/med/high format). This value is not valid if the compression mode (from above) is 5, a one pass crunch) 07-08 - Number of blocks compressed file takes (low/high, 254 bytes/block) 09 - Filetype ("P", "S", "U", "R", uppercase in ASCII, lowercase in PETASCII ) 0A - Filename length 0B-0B+length - Filename (in PETASCII, no longer than 16 characters) 0B+length+1 - Relative file record length (only for ARC version 2) 0B+length+2 - Date (2 bytes, in MSDOS format, only in ARC vers. 2) The header can also have some extra fields, depending on what version the archive is. Version 1 archives do not have the RECORD length and DATE fields, meaning they cannot contain REL files. The RECORD length is only used when the filetype is REL. Immediately following the filename (for version 1 archives) is the RLE control byte, and then follows the LZ table and compressed data. Watch out for "extra" data at the end of the file, typically many $00's. Some files which exist have this, and it makes reading the contained file list more difficult. 64COPY can unpack ARC files easily, and just hitting return on them will open the archive. Simply select what files you want to extract, and copy them out.