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4.0 - Compression Techniques


This article is from the Apple ][ Emulator Resources Guide, by Alex Maddison with numerous contributions by others.

4.0 - Compression Techniques

HINT: Want to decompress Apple II "*.shk" archives on a PC or Mac and don't have the software? Just import the archive into a disk-image (see in "ADDING/REMOVING FILES" in Chapter 7), run your favourite emulator and use ShrinkIt!

The list of extensions below will indicate what format the compression or translation is; from there refer to the "compression" document for cross- platform applications or executables. For Apple ][ compression formats (which are not covered here) check Section 5 in Part 3 of "The Apple II Frequently Asked Questions (FAQ)". ftp://ftp.cso.uiuc.edu/doc/pcnet/compression ( ftp://rtfm.mit.edu/pub/usenet/news.answers/apple2/faq/

  .arc       Arc (Amiga/Atari) - transfer as a binary file ['DArj'/'TEXT']
  .arj       Arj (PC) - transfer as a binary file ['arc@'/'TEXT']
* .bin       BinHex 5.0/MacBinary (Mac) - transfer as binary file['BnHq'/'TEXT']
* .bsc       Binscii (Apple ][) - transfer as a text file
  .cpt       Compact Pro (Mac) - transfer as a binary file ['CPCT'/'PACT']
# .dsz       GNU Zip (Unix) - rename to ".gz" before decompressing
# .gz        GNU Zip (Unix) - transfer as a binary file ['Gzip'/'Gzip']
* .hqx       BinHex 4.0 (Mac) - transfer as a text file ['BNHQ'/'TEXT']
  .lha       LHA (Amiga/PC) - transfer as a binary file ['LARC'/'LHA ']
  .lzh       LHA (Amiga/PC) - transfer as a binary file ['LARC'/'LARC']
$ .shk/sdk   ShrinkIt archive (Apple ][ format containing files or a disk-image)
  .sit       StuffIt Lite/Deluxe (Mac) - transfer as binary file ['SIT!'/'SITD']
  .tar       TAR/Tape ARchive (Unix) - transfer as a binary file ['TAR '/'TARF']
* .uue       Uuencode/Uudecode (PC/Unix) - transfer as text file ['JeFF'/'TEXT']
# .Z         Compress (Unix) - transfer as a binary file ['LZIV'/'ZIVU']
  .zip       PK Zip (PC) - transfer as a binary file ['ZIP '/'pZIP']
  .zoo       Zoo (Amiga/PC) - transfer as a binary file ['Booz'/'ZOO ']

[Square brackets] denote Macintosh file creator/type information .

These formats are translators; uuencoding (.uue) and binhexing (.hqx) are used to convert binary files into text files so that they can be posted to a binary newsgroup or e-mailed. Binscii (.bsc) is a similar process for the Apple ][; use "Shrink II" on the Macintosh (see below). The BinHex 5.0 format (*.bin) is Macintosh-specific; it is used to append the file/type creator information to the file in the first 128 bytes. Although emulators such as AppleWin can read disks with the MacBinary header, for compatibility with other emulators it is often better to remove the header. On the PC, use "bin2dsk" or "mactopc". ftp://ftp.apple.asimov.net/pub/apple_II/utility/Bin2dsk.zipftp://cassandra.ucr.edu/pub/apple2/incoming/Compress/bin2dsk.zipftp://wilbur.stanford.edu/pub/apple2/incoming/mactopc.exe

# These formats are single-file compressors - the other compressors on the list compress AND archive. Consequently, *.Z and .gz are often used in conjunction with other archivers, primarily Tar (.tar), resulting in the following: "filename.tar.gz" or "filename.tar.Z". Usually easier to remove on a Unix platform prior to download (use "uncompress" or "gzip" to extract).

$ Okay, so I said I wasn't going to cover Apple ][ formats... Use "Nulib" by Andy McFadden <fadden@uts.amdahl.com> for the PC or Unix to extract shrunk disk- images (usually shown by *.SDK rather than *.SHK) or files from this type of archive. For Macintosh users, EGO Systems provide a commercial product called "Shrink II" which can create/extract NuFX/ShrinkIt archives and other Apple ][ formats. Cost: US$39.95, from EGO Systems, 7918 Cove Ridge Rd., Hixson, TN 37343. Phone: 1-800-662-3634. Additionally, Matthew Russotto <russotto@pond.com> compiled "A2dearc", a Macintosh dearchiver for *.SHK, *.QQ and *.HQX files. http://www.jurai.org/~funaho/emulators/XGS/nulib324.zip (PC compile version 3.24) ftp://ftp.apple.asimov.net/pub/apple_II/utility/nulib.zip (PC compile version 3.03) ftp://apple2.caltech.edu/pub/apple2/ARCHIVERS/nulib324.tar.Z (Unix source) ftp://ftp.apple.asimov.net/pub/apple_II/utility/A2dearc.gzhttp://www.hypermall.com/ego (EGO Systems product information & ordering)

IMPORTANT NOTE: Where a filename possesses two or more extensions (eg. "filename.tar.gz" or "filename.sit.hqx") ALWAYS download the file according to the LAST extension (ie. if the last extension is .uue then it is safe to download it as text). If in doubt, download it as a BINARY file. When processing, start at the LAST extension and work inwards. Remember, if using a PC, it is only possible to have one extension visible in the filename at a time.

To find out more about compression in detail, try the "comp.compression.faq". ftp://rtfm.mit.edu/pub/usenet/news.answers/compression_faq/


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