What is the exact difference between a terminal, a shell, a tty and a console?

http://unix.stackexchange.com/questions/4126/what-is-the-exact-difference-between-a-terminal-a-shell-a-tty-and-a-cons/4132#4132

by LiveTheDream • 15 years ago

203 29 15 years ago

unix.stackexchange.com

egiva• 15 years ago

This was a great write-up, especially if you like your ol' unix history. Aside: I love the stack exchange sites (i.e. stack overflow, etc) - they are probably one of my top companies based just on how much I interact with their sites.

burgerbrain9• 15 years ago

This should be taught in the first CS class at every school. It continues to stun me how many CS grads in the US don't understand the difference between these things.

mbreese2• 15 years ago

Why should they know the difference between these things? Unless they are trying to implement a new terminal, there isn't much of a reason to know this minutiae. The rationale for the differences between them are mainly historical and not really a good design.

Now, I'm all for a "History of Computing" class being required for CS, but that's another story. I also wish that I had time during undergrad for a "History of Biology/Chemistry/science/alchemy" class (I was a biochem major).

burgerbrain9• 15 years ago

They should know what they are because they use them every day. It's like a racecar driver not knowing the difference between an axle and a wheel, he doesn't have to know how to make them or even fix them, but he should damn well know what they're called. Understanding this issue is fundamental to understanding Unix, and is also a superb way of introducing some classical IPC methods. Last I checked most schools still devote a required class or two to the subjects but somehow it fails to work a good deal of the time.

"The rationale for the differences between them are mainly historical and not really a good design."

The separation of shell, a terminal emulator, and a psuedo-terminal is bad design? Really? I would love to see a rationalization for that. EDIT: Or downvotes will work fine as well I suppose.

samstokes• 15 years ago

Each time you have to answer "why does Ctrl-Left go back a word on my laptop, but when I ssh into my server, it just prints some weird characters?", it's useful to know the distinctions between terminals and shells.

kapilkale• 15 years ago

edit: SO back up, comment removed

schiptsov• 15 years ago

Terminal is a program of some kind, like xterm, (or a monochrome device with nice smooth scrolling), shell is a different kind of program, that interpret your input like bash. TTY is an interface to access a system over serial line, and console is an interface pre-configured for administrative access. ^_^

spc476• 15 years ago

A terminal can also be a hardware device with a keyboard and monitor that is hooked up to a computer through a serial port. I used to have a VT102 hooked up to my Linux system at one point (it's in storage now).

mbreese2• 15 years ago

I'm sure most people these days don't know that the VT102 was an actual physical device, not just a configuration option...

(I'm only 33 and having get those kids off my lawn moments...)

jff• 15 years ago

A terminal is a physical device for access to a computer. The VT-100 and Teletype ADM-33 are both examples. Xterm is a terminal emulator for X--it pretends to be something like a VT-220, so you can run your text mode programs.

TTY, of course, stands for Teletype, which was a common terminal used in the early days of Unix. In the old days, you'd talk about having a whole room full of TTYs. Now, it seems to refer to the emulated terminals provided by a Unix-like system.

A console would originally be a specific terminal (often hard-copy, like a Teletype) hooked directly to the computer for administrative tasks.

pyre• 15 years ago

I remember seeing a a tty at a pay phone at a rest stop in Maine a few years ago (maybe 2007). IIRC, it was for the deaf.

Adaptive2• 15 years ago

Let's be clear about this: a terminal is what you have to disinfect Friday nights in the computer lab after a week of disgusting freshmen.

Wikipedia is sorely lacking in this critical detail.

Adaptive2• 15 years ago

ouch, the downvotes! for posterity let me note here that, in fact, I really did have to clean vt220 keyboards with alchohol wipes every week when working in the comp. lab. I have very fond memories of the vt220 despite this ignoble responsibility. Not germane enough to the conversation but anyone that spent time on a real terminal will hopefully relate.

gurraman• 15 years ago

The second answer by andcoz ends with a great summary. I'd quote it here if copy on ipad worked on SE.

saurik• 15 years ago

"""So when you look to a "text window" on you linux system (under X11) you are looking to: a terminal emulator, connected to a virtual terminal, identified by a tty file, inside which runs a shell."""

burgerbrain9• 15 years ago

It should likely be noted that xterm connects to PTYs, not VTs. Otherwise correct.

hexley• 15 years ago

Can anyone tell me why I can't zoom or select the text on this site on my iPad? Isn't this the very sort of thing we hate in flash thoughtfully recreated in HTML5?

jonknee2• 15 years ago

I can zoom and select text just fine on an iPad... Odd.

jonknee2• 15 years ago

How does copy not work? I just opened the link on an iPad and was able to copy fine.

What is the exact difference between a terminal, a shell, a tty and a console?

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