ttypäätteen

A ttypäätteen, often shortened to tty, is a text-based terminal interface used in Unix-like operating systems. It represents a character-oriented input/output device, typically a keyboard and a screen, or a console. Historically, tty terminals were physical devices, but in modern systems, they are often virtualized.

The term "tty" originates from Teletypewriters, which were electromechanical devices used for sending and receiving typed messages over telephone lines. In the context of computing, a tty device allows a user to interact with the operating system by typing commands and receiving text-based output. Each tty session is a separate environment where programs can be run and monitored.

When you log into a Unix-like system, you are usually presented with a login prompt on a tty. This could be a physical console attached to the machine or a virtual console accessed remotely via SSH. The system allocates a unique device file for each active tty, typically found in the /dev directory, such as /dev/tty1, /dev/tty2, and so on. These device files are used by the kernel to manage input and output for each terminal session.

Modern graphical user interfaces often run on top of a tty. The graphical environment itself is managed by a display server, but underneath it, the system still utilizes tty devices for underlying operations and for providing a fallback text-based console in case of graphical issues. Users can often switch between virtual tty consoles using keyboard shortcuts like Ctrl+Alt+F1 through Ctrl+Alt+F7, depending on the distribution.