TTY vs Terminal

[Smoot Carl-Mitchell]

On Tue, 2007-07-24 at 10:26 -0400, Jimmy Wu wrote:

>  the work (processing the commands and sending back a response).  One
> mainframe was usually connected to multiple terminals (TTY's), and
> many people could logon simultaneously, which is where the term
> timesharing came from.  Of course, all this became obsolete with the
> rise of personal computers.

Actual timesharing with TTYs is obsolete, but the technology which made
it possible is still a part of GNU/Linux systems, since all Unix like
systems are built on timesharing principals because the original Unix
operating system was a timesharing system. This is one reason GNU/Linux
systems are quite different than PC operating systems like Windows. The
key components of a timesharing system are:

1) Process scheduler
2) Protected memory
3) Robust file permissions system

All these components are necessary to keep multiple users from getting
in each others way on a shared system. The timesharing legacy is also
why GNU/Linux systems tend to be more secure than their Windows
counterparts.

While use of real TTYs is rare these days, the serial terminal interface
paradigm was adopted by various remote access services, such as SSH or
TELNET. If you look carefully, you will see there is a pseudo tty
allocated for each SSH session which behaves just like a real serial
port. This also happens every time you open a terminal command line.
>From the OS's perspective this all looks the same as if you were
connecting via a hardwired terminal.

-- 
Smoot Carl-Mitchell
System/Network Architect
email: smoot at tic.com
cell: +1 602 421 9005
home: +1 480 922 7313