Strange initial escape string

[Mario Signorino <mario.signorino@xxxxxxxxxxx>]

Hi all

I'm working on a new terminal emulator.
When I start the terminal with a bash shell, I read this string
"\033]0;Window title\007" followed by the prompt and the other stuff.
When I switch to zsh I read "\033[1m\033[7m%" and then the prompt.
What is that?
If I push the string manually into a gnome-terminal or an xterm
$ echo -e  "\033[1m\033[7m%" > /dev/pst/3
I get a % inversed and bold as expected... but starting the gnome-terminal
(or xterm..) does not show anything...

Is that some special stuff hidden by the terminals? I read it as "write %
bold and inversed".
Any hints?

Regards,
Mario