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Date:      Sun, 30 Apr 95 17:37:47 MDT
From:      terry@cs.weber.edu (Terry Lambert)
To:        pvinci@ix.netcom.com (Paul Vinciguerra)
Cc:        questions@FreeBSD.org
Subject:   Re: [Q] NCONS vs. ptys
Message-ID:  <9504302337.AA04354@cs.weber.edu>
In-Reply-To: <199504300447.VAA11899@ix2.ix.netcom.com> from "Paul Vinciguerra" at Apr 29, 95 09:47:00 pm

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> What is the difference between virtual consoles and pty's?

A virtual consle is like a pty, but contains device state information
for the console hardware as well.  For instance, scan code mode,
memory containing screen contents, screen graphics mode, cursor
location, current attributes, etc., etc..

A pty is just a pipe with cannonical processing on one end (the slave end)
so that programs think they are using a tty.

> I also understand that the number of xterms is limited by the number of 
> pty's.

That's right.  Xterms use pty's to make the programs running in them
(like your shell) think they are talking to a physica device.

Telnet, rlogin, screen, and other programs all use pty's to fool programs into talking to them.

The 'p' in 'pty' stands for pseudo -- it's a pretend tty.


					Terry Lambert
					terry@cs.weber.edu
---
Any opinions in this posting are my own and not those of my present
or previous employers.



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