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Path: utzoo!mnetor!george
From: george@mnetor.UUCP (George Hart)
Newsgroups: comp.terminals
Subject: Re: A Question About the Infamous VT100 Line Wrap Bug
Message-ID: <3954@mnetor.UUCP>
Date: Tue, 27-Jan-87 08:36:24 EST
Article-I.D.: mnetor.3954
Posted: Tue Jan 27 08:36:24 1987
Date-Received: Tue, 27-Jan-87 21:08:59 EST
References: <1504@blia.BLI.COM> <105@tg.UUCP>
Reply-To: george@mnetor.UUCP (George Hart)
Organization: Computer X (CANADA) Ltd., Toronto, Ontario, Canada
Lines: 31
Keywords: vt100

>In article <1504@blia.BLI.COM> forrest@blia.BLI.COM (Jon Forrest) writes:
>Could someone summarize the bug with vt100 terminals having
>to do with line wrapping. I recall it has something to do with
>what happens when a certain character appears in column 79 (80?).

I ran into this a few years ago while porting an editor to a V6 (yes he
did say V6 :-) system.  The bug can be demonstrated in the following way:

	1. turn line wrapping on
	2. using direct cursor positioning, place the cursor in
	   the second to last column.
	3. type a character
	4. using direct cursor positioning, place the cursor in
	   the first column of the next (or any line).
	5. type a character

Instead of the character appearing in the first column of the line you
moved to in 4, it appears one line further down.  It appears that
earlier rev's of the VT100 firmware did not reset an internal flag used
to indicate "wrap at the next character".  I don't know if this bug
still exists.
-- 


Regards,

George Hart, Computer X Canada Ltd.
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