W8SDZ@SIMTEL20.arpa (Keith Petersen) (11/09/86)
Some of the files in the SIMTEL20 MS/PCDOS software libraries have
been transformed by using one or another of the standard public domain
utilities that either SQueezes, LiBRaries, or ARChives files. This is
done to compress the files to minimize download time, and/or combine
several related files into a single easily-managed file.
These processed files are specially named with a filetype (the last 3
letters of a filename after the '.') that signifies the transformation.
These are:
.ARC for files archived with ARC.EXE,
.LBR for files libraried with LU.EXE, and
.?Q? for squeezed files (middle letter is a Q).
USQ.COM is used to unsqueeze, or expand files that have a "Q" as the
middle letter of the filetype. Such files have been squeezed, or
compressed with SQ.COM or something similar. These programs use
Huffman Encoding to reduce the size of the target file. Depending on
the distribution of data in a file it can be reduced in size by 5% to
60% by squeezing it. If you download a file with a filetype
indicating that it is squeezed, you will need USQ.COM to expand it
before you can use it.
ARC is used to create and maintain file archives. An archive is a
group of files collected together into one file in such a way that the
individual files may be recovered intact. ARC will automatically
compress member files when adding them to the archive, and will expand
them upon extraction. For files with the .ARC extension, you must
have a copy of ARC.EXE to extract the component files.
LU and its relatives (LUP, LUU, LUE, LUT, LU86, LAR etc.), maintain
libraries of files. Most LU-type programs do not perform any
compression. Because of this, most people will squeeze files before
adding them to a library if they want to save space. If you want to
remove the component files from an .LBR file, you should have a copy
of LUE.COM. This will break up the library into its component parts,
and optionally unsqueeze any .?Q? files at the same time. LUU.COM
will create a .LBR file.
For information on ARChives, see the documentation for ARC. The
various LU utilities will explain .LBR's and LUDEF5.DOC explains the
layout of these files in detail.
For SQ(ueeze) and USQ (unsqueeze) see SQUEEZE.TXT which provides a
background on squeezed files.
--Keith Petersen
Arpa: W8SDZ@SIMTEL20.ARPA
Uucp: {bellcore,decwrl,harvard,lll-crg,ucbvax,uw-beaver}!simtel20.arpa!w8sdz
GEnie Mail: W8SDZ
RCP/M Royal Oak: 313-759-6569 (300, 1200, 2400 bps)ddrex@gorgo.UUCP (11/10/86)
"What is a .ARC file" and its logical follow-up, "where can I get a copy" get asked - and answered - SO frequently that maybe the net needs a new news group, maybe call it 'net.micro.howto.arc' or 'comp.sys.arc'. :-) :-) There is another similar util called ZOO which is a very reasonable replacement for ARC. It is a good bit faster, and generally more efficient. Also truly pd, not shareware. Find *both* on your local IBM-PC bbs....