In the beginning, terminals and telecommunications equipment were always attached to serial ports; that's what they're there for. Quite a lot of features -- SIGINT on ctrl-C, EOF on ctrl-D, timeouts, line-based reading, simple translation, cleanup when the connection closes, etc etc etc -- were added to the serial port device driver to keep them simple to use. Modems and terminals had a fair amount in common, incidentally.

So, any interactive terminal program in UNIX talks to the terminal like a serial port. When you close an xterm or a PUTTY window, you expect things it was running to die with it, yes? Like a dialup teletype session would die when a modem hung up. It's the same thing.

But these days, they don't always have a serial port! Instead of rewriting everything imperfectly every time they created a new and special kind of terminal, they added a "virtual terminal" device to the UNIX standard. It's like a special kind of pipe where, if you write ctrl-C into one end, the other end dies... It has all the other usual features UNIX terminal programs have come to expect -- and should, since it's the same device driver.

Run 'stty' in an xterm -- it will tell you your terminal's "baud rate". Which doesn't matter for virtual terminals, but it's there for historical reasons.

The serial port driver handles things like
...and lots of other things. That's all in the device driver itself.

Using virtual terminals means you can run the exact same interactive program in a local terminal, remote terminal, GUI terminal, serial terminal, or whatever else and expect it to work the exact same way, right down to the weirdest bits of UNIX terminal history. (Try logging into a LINUX terminal as allcaps -- and watch the rest of the text become allcaps when it decides you're running a 6-bit terminal!)

ctrl-C is the only serial-like feature Windows has, and not even for serial ports. Windows actually put that feature inside each program -- but not all programs. Which means ctrl-C only works when it wants to.

When you type ctrl-C, the kernel sends SIGINT to whatever's attached to your terminal. It's not a feature of your shell.

When you type a line and hit enter, the kernel delivers the complete line to whatever program's reading. Programs don't have to assemble each individual keystroke themselves (unless they want to.)

These and much more are features of the serial port device driver, which all interactive terminal programs in UNIX depend on.

Serial ports in UNIX are a complicated topic. Sure, if you want.


Depends what you mean by that.

When you mount something atop of /home/, you see the contents of that partition in it and not what was there before. Sorry for the confusion. Perhaps that was poorly worded.