How to mirror a screem

[belahcene <belahcene@iap-cu.dz>]

Hi, thank you for reply, at last I could run my Xwindows in Two monitors 
( using the Xinerama extension),
with two monitor, it is nice and certainly usefull, 
but I need a mirroring of the first screen.
I mean same output in the 2 monitors. In fact when I use a datashow for 
seminary, I want see on my monitor where others see the on the big screen.
thank you
best regards
bela