Date:	Thu, 18 Mar 1999 18:01:37 -0500
Message-Id:	<199903182301.SAA30669@envy.delorie.com>
From:	DJ Delorie <dj AT delorie DOT com>
To:	djgpp AT delorie DOT com
In-reply-to:	<36F17BC3.78B926E4@cableol.co.uk> (message from Allens on Thu, 18
	Mar 1999 22:18:43 +0000)
Subject:	Re: (fwd) Compression
References:	<Pine DOT LNX DOT 4 DOT 10 DOT 9903181622370 DOT 1074-100000 AT narnia DOT n DOT ml DOT org> <199903182135 DOT QAA30067 AT envy DOT delorie DOT com> <36F17BC3 DOT 78B926E4 AT cableol DOT co DOT uk>
Reply-To:	djgpp AT delorie DOT com
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> I'm sure I heard somewhere that tgz's are based around the same 
> algorithm as zips, so why the mega space saving?  (Perhaps because
> they use a different algorithm?)

zip compresses each file separately, then stores them in the zip file
with headers.  tgz stores the files with headers, then compresses it
all at once.  Thus, not only is tgz compressing the headers, but it
also doesn't restart the compression algorithm for each file, so it
can recognize patterns in one file it saw in the previous file, and
compress better.

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