Using the Ctrl key to generate control characters was introduced in the ``Getting Started'' chapter but, as was explained at the time, what most control characters do depend on what computer you are using, so now is a good time to explain what some of the more important ones do under UNIX.
Ctrl C kill child process and return to parent.
Ctrl D end terminal session (unless ignoreeof set).
Ctrl L refresh screen.
Ctrl Q resume output to the screen.
Ctrl S suspend output to the screen.
Ctrl Z suspend child process and return to parent.