I think these terms almost refer to the same thing, when used loosely:

  • terminal
  • shell
  • tty
  • console

What exactly does each of these terms refer to?

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    [The TTY demystified](http://www.linusakesson.net/programming/tty/) – firo Mar 07 '13 at 07:54
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    I'd like to add 'command line' to that :-) – teeks99 Sep 07 '14 at 13:32
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    The command line is simply the language used to send commands to the command-line interpreter running in a shell from the terminal/terminal emulator. – Marty Fried Sep 07 '14 at 18:03
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    The **teletypewriter (TTY)** was first put in operation and exhibited at the Mechanics Institute in New York in **1844.** https://en.wikipedia.org/wiki/Teleprinter – Serge Stroobandt Dec 10 '15 at 20:28
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    [TTYs and X Windows](https://www.feyrer.de/NetBSD/ttys.html), [Linux terminals, tty, pty and shell](https://dev.to/napicella/linux-terminals-tty-pty-and-shell-192e). – Nishant May 09 '20 at 07:58

10 Answers10


A terminal is at the end of an electric wire, a shell is the home of a turtle, tty is a strange abbreviation and a console is a kind of cabinet.

Well, etymologically speaking, anyway.

In unix terminology, the short answer is that

  • terminal = tty = text input/output environment
  • console = physical terminal
  • shell = command line interpreter

Console, terminal and tty are closely related. Originally, they meant a piece of equipment through which you could interact with a computer: in the early days of unix, that meant a teleprinter-style device resembling a typewriter, sometimes called a teletypewriter, or “tty” in shorthand. The name “terminal” came from the electronic point of view, and the name “console” from the furniture point of view. Very early in unix history, electronic keyboards and displays became the norm for terminals.

In unix terminology, a tty is a particular kind of device file which implements a number of additional commands (ioctls) beyond read and write. In its most common meaning, terminal is synonymous with tty. Some ttys are provided by the kernel on behalf of a hardware device, for example with the input coming from the keyboard and the output going to a text mode screen, or with the input and output transmitted over a serial line. Other ttys, sometimes called pseudo-ttys, are provided (through a thin kernel layer) by programs called terminal emulators, such as Xterm (running in the X Window System), Screen (which provides a layer of isolation between a program and another terminal), Ssh (which connects a terminal on one machine with programs on another machine), Expect (for scripting terminal interactions), etc.

The word terminal can also have a more traditional meaning of a device through which one interacts with a computer, typically with a keyboard and display. For example an X terminal is a kind of thin client, a special-purpose computer whose only purpose is to drive a keyboard, display, mouse and occasionally other human interaction peripherals, with the actual applications running on another, more powerful computer.

A console is generally a terminal in the physical sense that is by some definition the primary terminal directly connected to a machine. The console appears to the operating system as a (kernel-implemented) tty. On some systems, such as Linux and FreeBSD, the console appears as several ttys (special key combinations switch between these ttys); just to confuse matters, the name given to each particular tty can be “console”, ”virtual console”, ”virtual terminal”, and other variations.

See also Why is a Virtual Terminal “virtual”, and what/why/where is the “real” Terminal?.

A shell is the primary interface that users see when they log in, whose primary purpose is to start other programs. (I don't know whether the original metaphor is that the shell is the home environment for the user, or that the shell is what other programs are running in.)

In unix circles, shell has specialized to mean a command-line shell, centered around entering the name of the application one wants to start, followed by the names of files or other objects that the application should act on, and pressing the Enter key. Other types of environments don't use the word “shell”; for example, window systems involve “window managers” and “desktop environments”, not a “shell”.

There are many different unix shells. Popular shells for interactive use include Bash (the default on most Linux installations), zsh (which emphasizes power and customizability) and fish (which emphasizes simplicity).

Command-line shells include flow control constructs to combine commands. In addition to typing commands at an interactive prompt, users can write scripts. The most common shells have a common syntax based on the Bourne_shell. When discussing “shell programming”, the shell is almost always implied to be a Bourne-style shell. Some shells that are often used for scripting but lack advanced interactive features include the Korn shell (ksh) and many ash variants. Pretty much any Unix-like system has a Bourne-style shell installed as /bin/sh, usually ash, ksh or bash.

In unix system administration, a user's shell is the program that is invoked when they log in. Normal user accounts have a command-line shell, but users with restricted access may have a restricted shell or some other specific command (e.g. for file-transfer-only accounts).

The division of labor between the terminal and the shell is not completely obvious. Here are their main tasks.

  • Input: the terminal converts keys into control sequences (e.g. Left\e[D). The shell converts control sequences into commands (e.g. \e[Dbackward-char).
  • Line editing, input history and completion are provided by the shell.
    • The terminal may provide its own line editing, history and completion instead, and only send a line to the shell when it's ready to be executed. The only common terminal that operates in this way is M-x shell in Emacs.
  • Output: the shell emits instructions such as “display foo”, “switch the foreground color to green”, “move the cursor to the next line”, etc. The terminal acts on these instructions.
  • The prompt is purely a shell concept.
  • The shell never sees the output of the commands it runs (unless redirected). Output history (scrollback) is purely a terminal concept.
  • Inter-application copy-paste is provided by the terminal (usually with the mouse or key sequences such as Ctrl+Shift+V or Shift+Insert). The shell may have its own internal copy-paste mechanism as well (e.g. Meta+W and Ctrl+Y).
  • Job control (launching programs in the background and managing them) is mostly performed by the shell. However, it's the terminal that handles key combinations like Ctrl+C to kill the foreground job and Ctrl+Z to suspend it.
Gilles 'SO- stop being evil'
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    Only quibble: I would say that both kinds of ttys are “provided by” the kernel. The difference I would emphasize is that hardware ttys (e.g. serial lines and the built-in, text-mode console) have one end connected to hardware and one end connected to software (e.g. login programs and/or shells) while pseudo-ttys have both ends connected to software (e.g. a terminal emulator on one end and shell on the other). – Chris Johnsen Nov 17 '10 at 04:04
  • I read in a book (forget the name, sorry), that the shell is supposed to protect the kernel: the user interacts with the shell, instead of directly with the kernel. – phunehehe Nov 17 '10 at 13:46
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    @phunehehe: Right, that's a different meaning of “shell”, in common use in operating system design: the shell is the outer part of the kernel. It's not unix terminology: Unix kernels don't tend to have a component that one could call a shell. – Gilles 'SO- stop being evil' Nov 17 '10 at 19:27
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    [This](http://osr507doc.sco.com/en/OSTut/graphics/kernel.gif) is the image in my mind for the shell metaphor. – ændrük Dec 07 '10 at 19:00
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    There is also another meaning of "console" under Linux. The console (there is only one) is where `printk` of sufficient priority goes (e.g., kernel panics). It is set by passing `console=DEVICE,...` on the kernel command line (e.g., `console=ttyS0,115200` for a the first serial port, at 115,200 bps). Normally it defaults to the virtual-terminal, but that can be changed when the kernel is compiled. – derobert Aug 29 '11 at 21:12
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    “…the terminal…handles key combinations like Ctrl+C to kill the foreground job and Ctrl+Z to suspend it” Not quite: the terminal still merely sends control characters, it’s the tty device that decides how to handle them, and it’s configurable. By default the tty device converts the control characters into signals sent to the shell (and other processes). – Chris Page Mar 10 '12 at 20:34
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    In addition to the comment above: Unix is, by design, a multi-user environment. Generally, people would interact with a unix environment using a thin client - a keyboard and monitor that would send commands over a wire to the unix server. TTY, if I remember correctly, used to stand for TeleTYpe - thus, every user using the system would have to interface through a tty. This is why multiple tty files exist in the filesystem; there's one for each teletype in use (and possibly not in use). – lunchmeat317 May 16 '12 at 22:58
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    The shell is indeed the outer shell of the kernel (protection or none), it deals with user<-->kernel interaction. The shell allows the user to perform kernel calls; primarily the focus here is on the ability to execute other programs interactively, because once you can execute programs you may run editors and compilers to produce programs to deal with the rest of the kernel calls. Generally file browsers like Nautilus are also shells, although perhaps not in **full** right, as they mostly don't support supplying custom arguments, but they **are** shells none the less. – Born2Smile Sep 02 '12 at 22:21
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    A quibble: The tty driver (through its cooked mode, more space for endless quips :) handles line editing (i.e., if I write something and erase it by backspacing, this is done by the tty. That is, unless `readline` or some such newfangled stuff handles it, with the tty in raw mode). The shell receives the line only after I press ENTER. – vonbrand Feb 13 '13 at 22:59
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    "The console" is actually the terminal (keyboard+screen-combo, though originally a teletypewriter) directly connected to the actual computer. It was usually in the (locked) computer-room, and only a few had access. It was also the only terminal working in single-user mode. All other users, used terminals connected by serial-lines. These days with PCs; "the console" is your PC's keyboard & screen, and you'll do most of your work on it directly. – Baard Kopperud Jun 13 '13 at 23:07
  • minor quibble with "Other types of environments don't use the word “shell”". Modern window systems do use the word "shell" and even have simplified "equivalents" of unix shells: e.g. powershell in Windows>=XP, and bash in Mac>=OSX – hobs Jul 01 '14 at 17:07
  • @hobs By “other types of environment”, I meant window-based GUIs as opposed to CLI. The whole paragraph is about unix. Windows does use the word “shell” for its GUI shell, which is Explorer by default (Windows also uses the word “shell” in the name “Powershell”, but not much as a type of program). – Gilles 'SO- stop being evil' Jul 01 '14 at 18:07
  • @Gilles the "shell" in "PowerShell" is indeed referring to a type of program, because that's what it is. And GUI window-managers for linux do use the word "shell" to describe a type of program that inhabits terminals within some windows... I must be missing something about the usage of the word "shell" that you're intending to inform us of in that quoted statement... If you're just saying that windows and GUIs aren't shells then I agree. That's like asserting that roads aren't the same as cars. If you're saying something more, like, metaphorically, roadsigns never mention cars, I don't agree. – hobs Jul 01 '14 at 20:46
  • @hobs In general, a shell can be any type of front-end program that allows users to run other programs. In the unix world, it's specialized to command line shells, but elsewhere, there are other types of programs that are called shells, such as GUI shells like Windows's task bar. – Gilles 'SO- stop being evil' Jul 01 '14 at 20:54
  • @Gilles, thanks. I didn't realize that **task bar**s were considered to be **shell**s on Windows/Mac and perhaps on Linux/Unix window managers. – hobs Jul 01 '14 at 21:01
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    @Gilles, I have way to look at shell. Long ago, we have master control program (MCP). MCP is responsible for loading program into memory and xferring control to program. MCP is big C prgm with mainloop that accepts keybrd input to call functions in MCP. The function called is first word entered and args are remaining words. MCP has lot of little functions to help with managing files and stuff. Funcs need fix/update. We already have .o files that we link together. Relinking MCP freqly, no good. Put file loader & path search funcs in MCP. Take other funcs out & put it path. Shell remains. – umeboshi Jan 25 '15 at 01:48
  • @Gilles: FYI, see [this](http://superuser.com/questions/795950/what-is-the-differences-of-these-conceptsshell-terminal-console-and-command-l#comment1299431_795959). – G-Man Says 'Reinstate Monica' Aug 07 '15 at 05:28
  • Great answer. But what is the difference between a virtual terminal and a pseudo-terminal? – labyrinth Sep 25 '15 at 18:27
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    Originally, a console (the piece of furniture) was placed near the computer with lots of buttons and lights and switches to control the computer. When terminals were introduced, (the only) one was logically placed on/built into the console. Then the other parts of the console became fewer and fewer, and in the end only the terminal was left. Hence the console terminal (the terminal in/on the console) became synonymous with the console. – Rhialto supports Monica Jan 21 '16 at 19:00
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    I think the term "shell" came from the metaphor that it is an outer layer or interface to the inner kernel. – Alex W Mar 15 '17 at 17:45
  • "The prompt is purely a shell concept." This confuses me a bit: is the terminal not responsible for displaying the prompt? – confused00 Mar 29 '17 at 15:11
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    @confused00 The prompt is of course displayed by the terminal, but all it does is interpret the order to display characters at a certain position in a certain color. The terminal doesn't know “this is a prompt”, “this is command output”, etc., it only knows “I've been asked to display this”. – Gilles 'SO- stop being evil' Mar 29 '17 at 17:24
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    I would argue that explorer.exe is a [shell for Windows](https://en.wikipedia.org/wiki/Windows_shell) as much as it's a window manager or a desktop environment. It is one of the three shells in Windows, the other two being cmd.exe (Command Prompt) and powershell.exe (Windows PowerShell) – PrashanD Nov 29 '17 at 08:44
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    @PrashanD Yes, Explorer is a graphical shell. But in the Unix world, “shell” usually means “command line shell”. There is a Unix graphical shell called Gnome Shell, but other than that the terminology hasn't really caught on. – Gilles 'SO- stop being evil' Nov 29 '17 at 12:25
  • Generally speaking tty is just a kind of terminal device, but in unix tty is the only terminal device, is that right? – darklord Jul 24 '19 at 10:15
  • Does the shell also emit an instruction to display command output? What do you mean by inter-application? – Shuzheng Jul 29 '19 at 20:31
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    @Shuzheng The shell is not involved in displaying the output of another command. Each program that displays on a terminal talks directly to the terminal. While this is happening, the shell sits there and waits for the command to finish. By inter-application copy-paste, I mean when you copy text in one application and it's visible to other applications, as opposed to copy-paste mechanisms that may exists inside one application. – Gilles 'SO- stop being evil' Jul 29 '19 at 20:37
  • @Gilles, so the shell just executed the command (program) and connects its stdin/stdout/stderr to the terminal? Is this accomplished using /dev/tty? – Shuzheng Jul 30 '19 at 05:33
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    while a **shell** is often CLI , it can be GUI also, as in KDE **plasmashell** and **liquidshell** . The above definitions are not 100% accurate. – dotbit Dec 11 '19 at 21:26
  • *the terminal converts keys into control sequences ... The shell converts control sequences into commands* Is not it all charge of the line discipline? In this regard (user's I/O), what's the separation of concerns btween line discipline and shell? – Ilya Loskutov Jul 23 '22 at 19:05
  • @IlyaLoskutov The line discipline is very very primitive (it only supports insert-character, enter, and deleting from the end of the line). Shells that people actually use interactively put the terminal in raw mode and have their own line editor. – Gilles 'SO- stop being evil' Jul 23 '22 at 22:11

A terminal or a console is a piece of hardware, using which a user can interact with a host. Basically a keyboard coupled with a text screen.
Nowadays nearly all terminals and consoles represent "virtual" ones.

The file that represents a terminal is, traditionally, called a tty file. If you look under the "/dev" directory of a UNIX system, you'll find a lot of tty files connected to virtual consoles (e.g. tty1 on linux), virtual terminals (e.g. pts/0) or physically connected hardware (e.g. ttyS0 is the physical serial terminal, if any, attached on first serial port of the host).

A console must be a piece of hardware physically connected to (or part of) the host. It has a special role in the system: it is the main point to access a system for maintenance and some special operation can be done only from a console (e.g. see single user mode). A terminal can be, and usually is, a remote piece of hardware.

Last, but not the least, a shell is a special program that interacts with a user through a controlling tty and offers, to the user, the way of launching other programs (e.g. bash, csh, tcsh).

A terminal emulator is a program that emulates a physical terminal (e.g. xterm, gnome-terminal, minicom).

So when you look to a "text window" on your 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.

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    Any desktop computer has system console (in my 2015 or poster’s 2010, don’t matter). As it was correctly stated, it’s a piece of hardware. But stating “Nowadays nearly all… consoles represent "virtual" ones” is nearly contradictory and obviously not good. – Incnis Mrsi Sep 06 '15 at 07:20
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    "A terminal or a console is a piece of hardware, using which a user can interact with a host. Basically a keyboard coupled with a text screen." awesome explication by its concrete aspect – Webwoman Sep 09 '18 at 11:45
  • @andcoz - What do you mean by "text window"? Isn't a terminal emulator a virtual terminal? If i run at the command `tty` in a terminal emulator such as KDE's Konsole, the output is /dev/pts/0. – Motivated Jan 16 '19 at 06:43
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    @IncnisMrsi - Isn't a desktop computer the _console_? If not, what do you mean by it has a system console? – Motivated Jan 16 '19 at 06:45
  • @anzcos - Do you also mean to say Xorg rather than X11? – Motivated Jan 16 '19 at 06:46
  • @Motivated `X11` is an alias for `X Windows System Protocol version 11`. XOrg is only one of many implementation of X11. – andcoz Jan 16 '19 at 11:20
  • @Motivated, in a desktop computer, the console is part of the desktop hardware. Usually, in non desktop computer, the console is a separate piece of hardware. – andcoz Jan 16 '19 at 11:25
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    @Motivated `/dev/pts/0` is a tty file, an handler to a programmatic interface exposed by the kernel. Through this handler, a program (e.g. the shell) can interact with a terminal (real or virtual). A terminal emulator is a software that emulates a terminal. The emulator asks the kernel to create an handler to let programs to interact with itself (see `man openpty`). So information flows from the terminal (emulator) to the kernel tty handler, to the program (and vice versa). Programs and terminals do not talk each other directly but only through the tty file (the handler). – andcoz Jan 16 '19 at 13:45
  • Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/88354/discussion-between-motivated-and-andcoz). – Motivated Jan 16 '19 at 16:44
  • @andcoz - My understanding is that X11 is a network protocol to enable communication between X Window System clients. – Motivated Jan 16 '19 at 16:50
  • @andcoz - Do you mean to say that when a terminal emulator is launched it utilizes one of tty files to communicate with the shell and other programs? – Motivated Jan 16 '19 at 16:50
  • @Motivated: unsure what did andcoz mean, but a terminal emulator uses the PTY interface not a tty – it’s [namely the distinguishing feature of *emulators*](https://unix.stackexchange.com/questions/117981/what-are-the-responsibilities-of-each-pseudo-terminal-pty-component-software). – Incnis Mrsi Feb 05 '19 at 13:47

SHORT explanation:

The console is a terminal. A system has got one console and potentially multiple terminals. The console is typically the primary interface for managing a computer, eg while it is still booting up.

A terminal is a session which can receive and send input and output for command-line programs. The console is a special case of these.

A TTY is essentially a pseudo device, call it a kernel resource, which is used by processes to access a specific terminal. TTYs can be tied to hardware such as a serial port, or can be virtual, eg created when a user logs in via a network

The shell is a program which is used for controlling and running programs. It is often used interactively, via a terminal. Several Shell programs exist, Bash being arguably the most commonly used shell today. Other shells, in no particular order, includes Bourne Shell, C-shell, Dash, Tsch, Ksh, and the increasingly popular zsh. There are many more.

When you have a GUI, you can use a terminal program to draw a nice resizeable border, add scroll bars, and format the text, and so on, for a terminal session. Often these are called terminal emulators, and sometimes they can handle multiple sessions via a TAB concept. A Terminal Emulator often starts a Shell to allow you to interactively work on a command line.

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A TTY (i.e. TeleTYpewriter) is a special device that lets people who are deaf, hard of hearing, or speech-impaired use the telephone to communicate, by allowing them to type text messages. A TTY is required at both ends of the conversation in order to communicate.
TTY is terminal which is used to type text message.

Shell :the outside protective covering part of a seed i.e. kernel.
framework or exterior structure to central or essential part of a system.
enter image description here

Console means the keyboard and monitor physically attachements to a computer.

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There are already two great answers, but I'd like to add information about the phrase “virtual terminal”. Generally, it means something that provides appearance/functionality of a terminal, i. e. a in a broad sense. But in the early days of Linux (1994–95) it was used synonymously with “virtual console” (several unrelated user interfaces), by some developers. This usage persists in documentation; two different terms were (and are) used to refer to tty1, tty2… thingies. Nowadays (since ≈ 1996) “virtual terminal” may also refer to -based terminal emulators.

Linux’s vt (the driver of text mode system console) was the first piece of its kernel. It was initially used for connection to mainframes and in this sense it’s a “virtual terminal”, hence the name. The code controlling virtual consoles resides in vt.c as well. Linux kernel engineers consistently use the word “consoles” to denote tty1, tty2… and used “vc_” prefix for them. For example, there is a vc_allocate function. On the other hand, developers of such user-space tools as kbd and console-tools used “virtual console” (VC) and “virtual terminal” (VT) interchangeably. I've contacted Andries E. Brouwer and asked him to clarify terminology used by early developers (1994–95). Andries kindly provided some answers. He states that VT and VC are synonymous and “indivisible” abbreviations.

In general, a virtual console is a virtual terminal, but the converse isn’t true. Those “virtual terminals” that are not virtual consoles are indeed pseudoterminals (as Andries states, these are not VT). Unlike virtual consoles, where the kernel provides terminal functionality for a console application, pseudoterminals use PTY “devices” to arrange communication between console applications and the terminal-making program that runs in userspace. Examples are X-based terminal emulators and sshd, that allocates a pseudotty for each login session. A pseudotty may not be called “console” – it’s a mistake.

Matthias Braun
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Incnis Mrsi
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  • Terminal = An interface that provides a display for output and a keyboard for input to a shell session.

  • Shell = Interpreter that executes commands typed as strings

  • Console: Actually two types of console we use:

    • Physical console =The hardware display and keyboard used to interact with a system
    • Virtual console = One of multiple logical consoles that can each support an independent login session.
  • tty (teletype i.e., terminal) = A terminal is a basically just a user interface device that uses text for input and output messages.

Matthias Braun
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Here is the short answer -

Kernel - the innermost part of any modern operating system which directly talks to actual hardware.

Shell - wrapper around the actual Kernel. Whenever we run command, we actually talk to shell which in turn invokes appropriate Kernel instructions. Apart from this, the shell is capable of performing some other stuffs like finding appropriate program while having commands, some file name short hand, piping commands etc.

Terminal - in the era of earlier computing, computers (known as Mainframe) were giant. So, it was easy to have a single processing unit and connect it from many places. Terminal is the actual hardware with keyboard and output devices connected to mainframe.

Console - Special type of terminal which is directly connected to Mainframe for the purpose of OS Administration.

tty - TeleTypewriter used to send and receive data to and from Mainframe. Used before Video Terminals were available. But conventionally it has been still named as tty. Even the coommand stty

The long detailed answer is here - Terminal, Console, Shell, Kernel, Commands - Different parts of a Computer

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  • thanks but basically if the terminal exist, why exist still tty also in ubuntu system for personal computers, accessible with alt + f-1/6 please, I can't figure out their utility above the fact they can be accessed without graphics system usage if I have well understood – Webwoman Sep 09 '18 at 11:59
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    @Webwoman - I have my system configured to only allow access to the `root` account through `sudo` or through a console login. Consoles often have a special place privilege-wise as someone who has access to them necessarily has physical access to the computer they communicate with. They are also the access method of last resort. If the OS is in a partially broken state (like the ethernet driver is broken) you can still access the console. It's the one human interface device that should ALWAYS be available, no matter what state the system is in. – Omnifarious Jul 12 '19 at 21:35
  • @Omnifarious thanks for your answer "Consoles often have a special place privilege-wise as someone who has access to them necessarily has physical access to the computer they communicate with" you meant TTY often have a special place privilege-wise ? – Webwoman Jul 13 '19 at 01:41
  • @Webwoman - Nope, console. A TTY is frequently not directly connected to a computer. And a console frequently isn't a TTY in the traditional sense. When I went to the U of MN in the late 80s, there was a campus-wide specialized network that I don't was running the Internet Protocol (aka IP) for connecting random TTYs to random computers. IBM mainframes have a similar thing going on and it was one the big reasons IBM created SNA. And a normal PC, even when it's only showing text, is very unlike a TTY in many ways, so a PC console isn't really a TTY exactly. – Omnifarious Jul 13 '19 at 03:21
  • @Webwoman - The defining feature of a console is that it has a direct connection to the hardware that's running the operating system. This idea is somewhat blurred with modern 'virtual machines', but that's the basic idea. – Omnifarious Jul 13 '19 at 03:23
  • @Webwoman - This was getting long and complicated enough that I just wrote it up in an answer: https://unix.stackexchange.com/a/529934/8068 – Omnifarious Jul 13 '19 at 03:55
  • @Omnifarious thanks for this very interesting answer and having taken the time to elaborate :). – Webwoman Jul 14 '19 at 05:39

You need to dive into history.

There were typewriter-like devices with paper and keyboard. They were called teletypes (which means "type remotely," since "tele" means "remote") or ttys for short. In the 70s they were obsoleted by devices with CRT monitor called glass ttys.

Any computer need some way to report its status and errors (and, probably, accept commands). It is done through console which is almost always connected directly to the computer. So, there are 2 meanings for console: something that is used to report status and something that is connected directly.

UNIX is an interactive system: several users may connect to it and start applications. First computers used teletypes (tty) for that: each user had teletype connected to machine with serial line connection. Such teletype is called terminal. UNIX also got special subsystem to handle "users sitting behind terminals" which is also called tty because first terminals were teletypes. Each process could be connected to tty in Unix. That means there is a user somewhere sitting near terminal. See http://www.linusakesson.net/programming/tty/ for more info.

Users need some way to tell kernel to run application. shell (sh, bash, csh, ksh, etc.) is used for that. shell runs on tty, accepts commands from user and asks kernel to run some app.

But terminals are not always physically connected to the machine. There may be some application that "emulates" terminal accepting keystrokes from user and sending them somewhere (xterm and ssh are good examples). There is an API in Kernel called pseudo terminal for that. So your tty may really be connected to some application instead of real terminal. Xterm uses X11 to display text and ssh uses network connection for it.

IBM PC has keyboard and video card (they are also called console sometimes). Linux can do different things with it:

  • Use it as "engine to report errors and status": Linux console. If you pass console=/dev/ttyS0 to kernel it will use something connected to COM1 as console, and if you do not it will use PC console.
  • Use it to emulate terminal, so called virtual terminal (vty).

It also may stop emulating terminal on console and give it to some app. App may switch its video mode and use it exclusively (X11 or svgalib may do that).

So, here are modern meanings:

  • terminal: Something with real user sitting behind it. Could be physical terminal (rare) or pseudo terminal (xterm, ssh) or virtual terminal (vty in Linux)
  • shell: application (bash, tcsh, etc) that helps user to interact with system.
  • tty: either terminal or kernel subsystem to support terminals.
  • console: something where status and errors are reported (/dev/console) or physical keyboard and video display connected to computer.
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Apart from the accepted answer and The TTY demystified article, I really loved reading these articles:

This one is based on NetBSD.

Back in the stone ages of Unix, computer systems consisted of a mainframe, a big box of blinking lights which had memory, mass storage and computing units, and that run processes started by users or operators. As the hardware was very expensive, the systems were used as true multiuser systems, with many people interacting with the system at the same time. What it usually didn't have - unlike today's Unix workstations - was a fixed monitor and keyboard. Instead, issuing commands to the machine and retrieving output was done over serial lines, using teletypers first, and CRT (cathode ray tube) terminals later. Teletypers - that's where the "ttys" in Unix come from - are electronic typewriters that send keys pressed over the serial line to the host, and replies were sent back to the teletyper char by char over the serial line, with the built-in printer putting the reply on paper, much like a typewriter.

This one is based on Linux.

Terminals are devices that provide enhanced input/output capabilities beyond what could be achieved with only regular files, pipes, and sockets. These features are designed to make it easier for humans to interact with computers, and are useless for programs trying to talk to each other.

This one is based on Linux.

Generally speaking a terminal is a relatively dumb electro-mechanical device with an input interface (like a keyboard) and an output interface (like a display or sheet of paper).

There is also an introductory playlist on terminals and shells by Brian Will on YouTube.

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I will use Unix and Linux more or less synonymously in this. If I'm referring to something historical that predates the existence of Linux, I will usually write "Unix", and if I'm talking about something more recent, or something specific to the Linux flavor of Unix, I will usually write "Linux".


The only thing in your list that is a discrete concept that has no overlap with the others is the 'shell'. The shell is a program whose purpose is to communicate with a user and carry out operating system operations on their behalf.

The most common shells use a technique called a 'command line', which consists of sending the user some sort of prompt, waiting for the user to type out a text command, and then carrying out that command. But there are menu-based shells and even graphical shells (like Windows File Explorer), though no self-respecting Unix person would ever call such a thing a 'shell'.

In Unix, if someone calls something a 'shell', they almost certainly mean some form of command line interface as I just described. And it is very odd in the Unix world to refer to anything as a 'shell' if it isn't communicating to a user using the tty model I describe further on.


This is a confusing one because it can refer to a few different kinds of things.

In Linux, there is a kind of device called a 'tty'. It is an abstract device that is expected to be used for bi-directional communication with something that either is a user, or is taking input from a user in some way. Sometimes that abstract device may correspond directly to some physical device. Sometimes it may be a program that is presenting someone with a window in which the communication appears and into which the user can type.

But the reason this abstract device exists and the reason it is called a 'tty' is that 'tty' is short for 'teletype', which was an actual physical device that had a printer that printed on paper, combined with a keyboard. The model that the abstract 'tty' device presents to programs that are using it is basically that there is a teletype on the other end. You send it characters and those characters appear on the teletype. When you read characters from it, those characters represent keys that were typed on a keyboard.

The old paper-printer based ttys were quickly supplanted with video ttys. On those, of course, there is no roll of paper. And, in fact, it is (almost always) possible to overwrite any character on the screen. But, rather than present some kind of abstract 'screen' interface to programs, programs are instead expected to send special streams of characters called escape sequences that accomplish a variety of tasks. Usually, there is an abstract thing called a 'cursor' that can be moved around the screen, and any character sent will replace whatever is at the cursor, and the cursor will move one character position further on (i.e., to the right, when using a left-to-right language).  Special characters like Tab, Backspace, Carriage Return and Line Feed can (fairly obviously) move the cursor in ways other than one-space-further; many devices support escape sequences that move the cursor in more complex ways.  Often you can change the color of a character that's about to be printed with escape sequences as well.

There are 'glass ttys' that do not follow this model and consequently are handled poorly in the Unix world.  The IBM 3270 family of video terminals falls into this category.

What Linux/Unix people typically call a 'shell window' is an emulation of a glass tty using a graphical user interface. Internally, programs running inside a shell window are talking to a virtual tty device that is sometimes called a pseudo-tty or pseudo-terminal (a.k.a. a 'pty').


A terminal is just a place where computer and human are supposed to interface. Terminals may be completely graphical and not follow the tty model in any way, even though a program may use their capabilities to emulate this. All actual physical ttys (glass or otherwise) are terminals.


A console is a special kind of terminal that is generally supposed to be attached in some direct secure way to the hardware the operating system is running on.

In Linux, the console is virtualized in a small way which allows you to use a special keystroke to switch between the virtual consoles. But this virtualization is done with a real piece of hardware by software in the kernel.

There are ways to use Linux through what's called a 'serial console', which is a console that's attached to the computer through a serial port like a USB port (or, on some very small and/or very old computers, an RS-232 port of some kind) and follows the old teletype model in a fairly strict way.

Again, the idea is that this console is connected in a direct physical way to the computer instead of through some sort of network that might allow anybody to connect.

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