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From: bzs@bu-cs.BU.EDU (Barry Shein)
Newsgroups: comp.unix.wizards
Subject: Filtering Everything
Message-ID: <6947@brl-adm.ARPA>
Date: Fri, 17-Apr-87 00:30:21 EST
Article-I.D.: brl-adm.6947
Posted: Fri Apr 17 00:30:21 1987
Date-Received: Sun, 19-Apr-87 10:12:52 EST
Sender: news@brl-adm.ARPA
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>Internal to IBM there is a terminal emulation program that does exactly
>what Stefan asks about, but for VM/CMS.  It uses a modification of the
>Lempel-Ziv compression algorithm which constantly updates the "tables"
>(actually a cache like algorithm).  On normal english text, this method
>commonly gets a factor of 2 compression.
>
>			Josh Knight

But Josh, doesn't this take advantage of the half-duplex nature of the
terminals involved? I assume this is aimed at IBM327x terminals where
you essentially do local formatting of an entire screen and then hit
ENTER to send the entire screen at once. I think what Jim was worrying
about was full-duplex, character at a time terminal I/O. How well does
this compression work if all you hit are Function keys? I thought so.

Anyhow, now *I'LL* throw my 3c in...you're both right.

Jim, it won't work well on input, but who cares? It will work well
on OUTPUT which tends to come in much more voluminous bursts, single
chars (eg. echos) may as well come plaintext, who cares? 1200b is
plenty fast enough. But if you hit ^L for a full screen redraw then
it should be advantageous, or MORE a file etc.

So (to the original poster) don't listen to any of us, we do this
all the time (prove that the sun does/doesn't rise in the east), just
go ahead and write your program and post it when it's working, thanks.

	-Barry Shein, Boston Univeroxib.