UNIX for Dummies Questions & Answers

Hi ,
I have searched wiki for pseudo tty devices but it was very complex for me to understand.
Can any one help me understanding concept behind pseudo-tty in layman language?
According to security manual of our org /etc/securetty files shouldn't have any pseudo tty devices.
i understand
ttyX
vc/X
are not tty devices but not sure about
console and xvc0 .
Please help.
I m posting the content of my /etc/securetty file.

Code:

]# cat /etc/securetty
console
vc/1
vc/2
vc/3
vc/4
vc/5
vc/6
vc/7
vc/8
vc/9
vc/10
vc/11
tty1
tty2
tty3
tty4
tty5
tty6
tty7
tty8
tty9
tty10
tty11
ttyS0
xvc0

This is Operating-System dependent. It doesn't look like a mainstream unix.

xvc0 is probably there to allow root login on a xen console. This a virtualized host?

A pseudo-TTY is it's a virtual device that acts like a terminal -- that is to say, acts like a serial port plus all the frills UNIX has added to them over the years with a keyboard and screen attached. You get features and side-effects like you'd expect of a real terminal: It can be configured to produce SIGINT when someone writes ctrl-C into it, you can configure it to echo its input or not, etc, etc. But it's not a real terminal -- it's a purely software thing. There's no real keyboard or screen involved anymore.

This is used for things like ssh, where you want to log into a real terminal but of course are too far away to do so. It opens a pseudo-terminal instead and just sends everything along.

Software can tell the difference between something that's a terminal and something that's not. Password inputs read only from a real TTY or a pseudo-tty for instance.

Yes .Is it a pseudo device?

yes it is a pseudo device.