[jerf]

Not only can you implement that with PTYs, it's how they operate by default. That's why you can telnet to an HTTP server and make a mistake and use backspace to fix it. The terminal will only send lines over. You have to use a command to put it into "raw" mode so the application gets every keystroke immediately. You have to ask for your PTY to not work that way.

[eichin]

That's not the same thing - with a pty in line mode, you get one line that you can edit, and when you hit enter, it gets sent. With Domain/OS, you still get to edit your last line until you hit enter... but if the process is otherwise blocked and doesn't consume it immediately, you can up-arrow and continue editing the earlier bits too. (Pretty sure it didn't work with telnet in particular, the common cases I remember were issuing a foo;bar;baz commandline and "working on" the input to baz while foo and bar were still running.)