> Simply... how I can copy some text in the buffer used by c-y? I use
> c-w but It also cuts the text....
> Or other ways to mantain a region in memory and paste it later...
look at M-y.
C-y yanks the most recent killed or yanked text.
If you type M-y just after C-y, the yanked text is replaced by the
previous entry in the kill-ring. It might not be very clear, so just
try it: Do some editing involving C-w/M-w/C-y, then do C-y M-y and
watch what happens.
There is also a package called `browse-kill-ring'. I never used it,
so I can't really tell you how it works.
> Also, I use line and column-numer-mode, but there's a way to show
> really the line numbers at the left of the buffer
I think the package setnu.el does just this.