From: olounela@klaava.Helsinki.FI (Olli Lounela)
Subject: Re: Help me "self-extract" PCIGC44Z.EXE
Organization: University of Helsinki
Date: Thu, 31 Dec 1992 00:22:31 GMT

In article <1992Dec30.150540.15957@ll.mit.edu> nates@ll.mit.edu ( Nate Smith) writes:
>In article <92365.000051PEF2@psuvm.psu.edu> Per Fjelstad <PEF2@psuvm.psu.edu> writes:
>>
>>I introduced one possibly significant irregularity in transferring the file to
>>my home computer.  I needed to reduce the record length to get VM's command
>>"pctrans" to move the file.  I did this by running it through VM's simulations
>>of the Unix "Compress" _and_ "Decompress" commands. On the return "Decompress"
>>operation, I choose an option that reduced the length of the records in the
>>output file.  With this done, I was able to download the file to my PC.
>>
>>1.   Might I have distorted the file by sending it through that sequence?
>
>  yes.  you probably did.  the .exe file is already compressed, so it wont
>do to compress & uncompress it another time.  if there is a way to move it

Now this is only mostly true.  The problem with data integrity is real,
but while it is usually of no use to recompress a compressed file, it
usually does not do any real harm either.  It only results in an
unefficient recompress that usually outputs a longer result than the
source. 

Lots of other people have pointed out that the most likely source of an
incorrect decompress of a self-extracting archive is a problem with the
reliability of the data transfer.  With a compressed file, a single bit
incorrect usually causes a major problem.  With ftp, however, I myself
have had no problems whatsoever, unless I forget to set it to binary
transfer (and in that case it's my own fault anyway :-)

Always remeber to set things to binary transfer unless it is plainly
ASCII you are transferring (and even then it is not a really bad idea
unless the file is lengthy :-)

>>2.   Or was my original understanding wrong that I just needed to type the
>>     filename, once the file was on my PC, to get a working program?
>
>as adrian pointed out (new for me too!), the pkunzip program will unzip a
>self-extracting archive and try to inform you of errors.  the problem may
>be that by the time the file made it to your PC (i think) it is corrupted.

Your "original understanding" is correct.  Once you get the file into
your PC intact, you should but need to run it.  It should decompress
itself and result in several files. 

Adrian's advice is correct, however.  PKunZip works with a
self-extracting file as well as with any PKZip archive, up to and
including PK(un?)Zip's -t option, which tests archive integrity. 

Nevertheless, I think that the source of your problem is trying
uncompress the program with VM's (unstandard) decompress.  Please
remember that pcigc44z.exe has already been compressed and so it does
not really benefit from a recompress, and if it does, there is something
seriously wrong with your (un)recompress.  For example: I ran it through
Un*x compress, and it refused to do anything.  It reported a compression
of -32.62% -- yes, that's an increase of 1/3 in length!

'VM' makes me think you're using IBM mainframe. Somehow I cannot believe
they have that much better a compress than Un*x, and it's been dicussed
in News that PKZip actually has a very efficient comression algorithm.

I did, BTW, snurf the PCigc from Milton today, and it worked without
problems, self-extraction and all. 

>>Per Fjelstad (3k),
>
>this isnt any help - just speculation!

But I hope I'm of some help, even if only a little.
-- 
	Olli, 3 dan

E-mail: olounela@cc.helsinki.fi           ! .sig still under construction.
Blame me only for any opinions expressed. !  Never you mind, I don't either.
Newsgroups: rec.games.go