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Re: Terminal

On Mon, Apr 25, 2005 at 01:58:17PM +0100, Shahzad Chohan wrote:
> I'm a little confused, could someone please help me explain what is a
> terminal, what is it for and why do we need it. Why are there
> different types of terminals? Also where does the term vt100 or vt102
> fit in to this?

Traditionally, a terminal was an actual piece of hardware -- a CRT monitor
plus keyboard that connected to a computer via a serial port. The VT100 and
VT102 were two such products from Digital. See <http://vt100.net/vt_history>
for pictures and more history.

As you can see from that page, there's lots of terminals from DEC alone. And
there were many others from many different manufacturers. Each of these
spoke a slightly different protocol for rendering text on the screen, so
Unix computers have means of speaking these different protocols depending on
what's connected.

Of course, the personal computer revolution basically wiped out the use for
such terminals -- now, we just sit at an actual computer system directly.
But, for convenience, when a command prompt is wanted, rather than
completely reinventing the wheel, the command prompt windows we use actually
act quite like the terminals of old, from the operating system's point of

So, you can have a terminal program which acts to the OS as if it were a
VT100 or VT102 -- although connected over a virtual "pseudo terminal" device
(see "man pts" if you want more) rather than connected via a real serial

Usually these days it's more common to emulate "xterm" (actually a terminal
type *invented* for a "fake" terminal, the venerable xterm program itself)
or to emulate "linux", the console type linux uses for its own virtual text
terminals (what you get in runlevel 3, or when you hit ctrl-alt-f1).

Make sense?

Matthew Miller           mattdm mattdm org        <http://www.mattdm.org/>
Boston University Linux      ------>                <http://linux.bu.edu/>
Current office temperature: 71 degrees Fahrenheit.

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