The terminal is the interface with which you enter the mysterious Linux commands, but is the terminal just a window with a command line on the Linux desktop? The fact is that the terminal you are currently using is probably not real. In this article I will talk about the true meaning of the Linux terminal and console. It is important to understand this basic concept if you want to master Linux.

Connection – Human Machine Interface

As a name, the terminal has many meanings. The Merriam-Webster dictionary gives us a good definition of a terminal in the computer field:

a combination of a keyboard and an output device (e.g. a video display device) that can be used to input or output data from a computer or an electronic communication system.

Man and the computer are two independent entities. A person needs an interface to enter information into a computer and read its output data. Today the input device of the PC contains a keyboard, mouse and microphone. The output device consists of a monitor and a loudspeaker. They are generally referred to as peripherals. But in the world of Unix and Linux the input and output devices are called terminals. The opposite of the terminal is the host, which includes devices such as the processor, the random access memory, the hard disk, etc. The host is a computer.

Okay, now we have two equations.

Computer = host + terminal

Connection = input device + output device

First terminal

At the end of the seventies the personal computer appeared in daily life. Previously, we could only use mainframes and expensive minicomputers in large companies or universities. The mini-computer PDP-7 used by Ken Thompson and Dennis Ritchie (the two makers of Unix) cost $72,000 in 1965, and the GE-45 mainframe cost $10 million.

Ken Thompson and Dennis Ritchie wanted Unix to be a multi-user operating system, which means that every user has a terminal to connect to his or her computer. Each user needs a monitor and a keyboard. However, every computer device, including the monitor, was very expensive at the time. And the keyboards were physically connected to the computers. In those days there were no removable keyboards.

So they found an alternative solution: using an inexpensive ASR33 teletypewriter as a terminal. Teletype (TTY) is mainly used to send and receive typed messages in telegraphy, but can also be used to enter information to and from a computer. You use the keyboard to enter and print information on paper.

Linux terminal and console explained to the dummies

Telex ASR33

Many teleprinters were connected to the same Unix computer. Every user can login under Unix with his own username and password for his teleprinters. Unix was the first multi-user operating system, and ASR33 was the first Unix terminal. Therefore, under Unix/Linux, the abbreviation TTY is generally used to indicate the terminal.

Over the years, the terminals have become increasingly sophisticated. In 1970 DEC (Dgital Equipment Corporation) introduced the VT05 video terminal. It has a monitor with an output video screen.

Linux terminal and console explained to the dummies

Video terminal VT05

Symbol terminal vs. graphics terminal

A symbolic terminal is also called a text terminal, which can only send text information. Telexes are symbolic terminals. The most famous personal terminal is the VT100, which was manufactured by DEC in 1978. It is so well designed that it has become the standard for later terminals.

The graphics terminal is better because it can also display images on the screen. The best-known graphics terminal is the X-Terminal, which provided the basic support for the X Windows system.

Linux Terminal Emulators

Now, you know the terminal is a device. In the 1970s and 1980s teams were recruited to sit in front of a real terminal. Nowadays we often enter commands into the software terminal, better known as a terminal emulator or terminal emulation application. They are sometimes called virtual terminals. They are not real terminals, but the operating system thinks so.

If you are using a Gnome terminal, you can use the following command to read the Gnome terminal manual

Gnome terminal for men

He says the dwarf terminal is an application to mimic the terminal. It mimics Xterm.

Linux terminal and console explained to the dummies

Xterm is also a terminal emulator. It emulates DEC’s VT102 terminal. Now you can still find Xterm in your Linux distribution.

What’s the console?

In the seventies and eighties of the last century there are often terminals connected to the host, but there is a special terminal that is connected to the host. This specific terminal is called a console. It is only used by the drivers. There’s only one console on each computer. There is not much difference in appearance between a standard terminal and a console, but the console can do what standard terminals cannot. For example, if the operating system hadn’t booted up, an error message would appear on the console, but not on the other terminals. And when the operating system boots up in single-user mode, only the console can be used to log in. The other terminals do not have single-user login authorization.

Linux terminal and console explained to the dummies

Mini computer console PDP-7

Console and terminal are often considered synonymous with personal computers. Your monitor and keyboard are both a console and a terminal. You can switch from a default user to an administrator at any time.

Virtual Console

There are actually two types of terminal emulators. The first type is the terminal window that you open in the desktop environment. The other type is the virtual console. In the 1970s and 1980s people could often only use one terminal. The heavyweights of a company or university can use multiple terminals because they have to do a lot with the operating system. So there would be several terminals on their desks.

At the moment we don’t have to put multiple terminals on the table, because Linux can create multiple virtual terminals. One is a graphical terminal, the other six are symbolic terminals. Seven virtual terminals are better known as virtual set-top boxes and use the same keyboard and screen. A physical console is a combination of your monitor and keyboard. When Linux boots up, 7 virtual consoles are created and by default you are directed to the graphical console, i.e. your workstation. You can run the Who command to check which virtual console you are using.

which

Linux terminal and console explained to the dummies

As you can see, I use the 7th virtual console (tty 7).  To switch to the virtual symbol console, simply press Ctrl+Alt+ F1 or Ctrl+Alt+F2 . Ctrl+Alt+F6. To return to the virtual graphics console, press Ctrl+Alt+F7.

When is a virtual console useful? If the desktop environment does not respond for any reason, or if the desktop/the taskbar icons suddenly disappear, you can switch to the virtual icon console and enter commands to diagnose the problem.

Pay attention: On Fedora, tty1 is the default virtual graphics console.

What is theenvelope?

The terminal is only a mechanism for transmitting information. The operating system requires a shell to understand the information. The shell under Linux is a program that interprets commands entered into a terminal window so that the operating system understands what you want to do.

There are many programs like Bash, Zsh, Csh, Ksh and others. Bash is the standard shell on most Linux distributions. When the terminal window opens, the bash shell starts automatically. To check which shell you are currently using, run the following command.

The echo of 0

Linux terminal and console explained to the dummies

Distance between terminal and host

Terminals can be connected directly to a host on a laptop. Terminals can also be connected to the host by cable, for example to a desktop computer. In fact, terminals can also connect to the host over the network. For example, if you have two computers on your local network. One of them runs on Linux. You can use another computer to connect to Linux using SSH or VNC. For example, the computer with Linux is the host and the other computer is the terminal.

The Virtual Private Server (VPS) in the data centre does not have its own terminal (keyboard or screen). Landlords without terminals are called headless systems. If you use a VPS in the data center, SSH allows you to connect to the VPS remotely so that your local computer becomes a VPS host terminal.

Packaging

I hope this article has helped you to understand Linux terminals, decoders and enclosures. As always, if you find this article useful, subscribe to our free newsletter for more tips and tricks.

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