Disinfectant
No discussion could be complete without a small listing of useful utilities.
Disinfectant
Before I get to compression, lets' talk virus. There are many good virus protectors on the market. One of the best free utilities is Disinfectant. Disinfectant helps keep those nasty viruses off your disks. This program is especially recommended if you are downloading software from unknown sources.
<ftp://ftp.acns.nwu.edu/pub/disinfectant/>
When you download items from the Internet, they are often compressed to make the file smaller. A smaller file means that you spend less time downloading. This means that you have to "expand" the file when you get it to your machine. Also, many files are encoded so they contain only printable characters. This way they can be sent through email. You will need utilities that can decode the files back to their original state. Often a file is compressed and THEN encoded. You have to untangle this at your end. Don't worry. the utilities below make it easy. The files you receive almost always have a code in the file name that tells you how to untangle them and in what order.
Stuffit Expander
Stuffit Expander expands .zip, .arc, .Z (Unix Compress), .gz (gzip), .uu (UUencoded), .hqx (BinHex), .pkg (AppleLink packages), .cpt (Compact Pro), .bin (MacBinary), and SpaceSaver-compressed files. It will join files segmented with StuffIt. Of course StuffIt Expander will also unstuff StuffIt (.sit and .sea) archives. The only problem here is: How do I download this program without a decoder/unstuffer to interpret it? You can't. You will have to get this program from someone else either on a floppy or from a local file-server. This is the only catch-22 I can think of in this whole mess. Hopefully, your system manager or internet service provider can supply you with the program. If all you have is Netscape, you are in luck. It might be able to decode Stuffit from the source below:
<http://hyperarchive.lcs.mit.edu/HyperArchive/Archive/cmp/stuffit-expander-401.bin>
Disk Copy
Often "images" of complete floppies are found on the net (especially on Apple's archives. Disk Copy lets you make original, clean floppies from the images (and vice versa.)
ShrinkWrap
ShrinkWrap lets you use disk image files directly without making floppies from them. This program mounts image files right onto your desktop as if you had put the real floppy into a drive. This is really handy.
<http://www.halcyon.com/shrinkwrap/>
The table below tells you which program can decode which formats. Most of these programs (the Mac versions...) are available from the MIT InfoMac HyperArchive <http://hyperarchive.lcs.mit.edu/HyperArchive.html> or the Stanford InfoMac FTP site <ftp://sumex-aim.stanford.edu/info-mac/>
Macintosh programs
unix gzip .uu/ .b64/
.cpt .sit .hqx .bin .arc .zip .tar .Z .gz/.z .uue .mime*
Stuffit Expander** D D D D
w/ DSEE** D X X D D D D D D D
ShrinkWrap 2.1.0*^ D D D D D D D D D D
StuffIt Lite*** D X X X {see note below}
StuffIt Deluxe*** D X X X D D X X D X
ArcMac X
BinHex 5.0 D X
Compact Pro 1.5.1 X D/N X
Decoder D D
Extractor 1.2.1 D D/N D
HQXer 1.1 X
MacCompress X
MacGzip D X
MPack 1.5.1 D D X
SunTar 2.1.0 X X X X
UU Lite X
uucd 2.4.4 X D
UUTool X
YA-Base64 1.2.9 D D D
ZipIt 1.3.5 D D X
Other Computers
unix gzip .uu/ .b64/
computers .cpt .sit .hqx .bin .arc .zip .tar .Z .gz/.z .uue .mime*
binhex.exe X
binhex-pc-13 X
extrac.exe D
macutil (unix)
hexbin D D
macunpack D D/U D D
mcvert (unix) X X
MPack D D X
PKZIP X
SITEX10.EXE (win) D D D D D D D
unsitins.exe D
xferp110 (win) X X X
N = Cannot decode .sit dlx {Type SITD} files
D = Decode only
X = Encode and decode
U = Uncertain or Unknown
.sit refers to both 1.5 and dlx. Otherwise a '/' is used {1.5/dlx}.
.hqx = BinHex4; .bin = MacBinary (BinHex5)
Note: Almost every Mac communications program can decode .bin files.
* .b64/.mime (Base 64) refers to the encoding format used by the
Multipurpose Internet Mail Extension. For more information consult
the MIME FAQ.
<http://www.cis.ohio-state.edu/hypertext/faq/usenet/mail/mime-faq/top.html>
** DropStuff with Expander Enhancer is an $30 shareware addon for Stuffit
Expander. DSEE is also used by other programs {marked with a *^}
to expand files. Current versions are 4.0 and 4.0.2b2 respectively as
of this writing (1/1/97).
*** Stuffit Deluxe 3.5/4.0 translators can be used with Stuffit Lite.
Current versions are 4.0.0 and 3.5.0 respectively as of this writing (1/1/97).
Other Formats
.arj
PC format common to European sites. Decoded by unArjMac, DeArj, and
SITEX10.EXE (win).
.dd
Disk Doubler (Mac) format. Decoded by DDExpand and DiskDoubler.
.exe
DOS/Windows executable file (program); also used to create
self-extracting archives. An .exe file used as a self-extracting
archive can usually be decompressed with Stuffit Expander w/ DSEE.
.html (.htm)
WWW document. Used by WWW browsers such as Netscape and lynx.
.image
Mac disk image. Decoded and/or mounted by DiskCopy, Disk Image Mounter,
Disk Charmer, and ShrinkWrap (ImageMaster).
.img/.ima
Microsoft Disk Image Utility and Winimage formats, respectivly. Decoded
and/or mounted by ShrinkWrap. Note that .img is also used as an graphic
file extension and needs GraphicConverter to view.
.lzh
old PC/Amiga format, replaced by .arc and .zip; decoded by macunpack,
MacLHA, and Frensh KISS 2.1.0
.pit
old {~1989} Mac compression format created by PackIt programs, replaced
by .sit. In general, a program that handles .sit files can decode .pit
files as well.
.pkg
AppleLink package format, replaced by .sit. Decoded by all present Mac
StuffIt programs.
.sea
Mac format, decompresses itself and needs no external programs.
.shar
Unix shell archive. Decoded by Unshar.
.taz
another name for .tar.Z
.tgz
another name for .tar.z and .tar.gz {do not confuse with .tar.Z}.
.txt
ASCII text file. Other suffixes include .abs
.z
Early {~1993} suffix for Gzip files. Due to confusion with the UNIX
'compress' suffix {.Z} it was abandoned in favor of the .gz suffix.
.zoo
old {~1989} PC/Amiga format, replaced by .arc. Decoded by MacZoo and
MacBooz.
CAUTION: While Gzip is aimed at replacing the .Z format, they are _different_
unix compression formats, and the suffixes are NOT inchangable. Many sites
now support on-the-fly translation of these formats; just type in the file
name minus the .Z or .gz suffix.
WARNING: .hqx, .txt, and .uu files are the ONLY files that can be downloaded
in ASCII mode; all others must be downloaded in BINARY {IMAGE} mode for the
file to decompress properly. This is especially true of ".bin" and
"unstuffed" files. Otherwise you will get errors like "unreadable file" or
"file is corrupt" when you try to decompress them.
If you need further information please check out the comp.compression FAQ
<http://www.cis.ohio-state.edu/hypertext/faq/usenet/compression-faq/top.html>
or David Lemson's compression chart at
ftp://ftp.cso.uiuc.edu/pub/doc/pcnet/compression.