Teletype (TTY) or teleprinter is the name for typewriters with an electromechanical system that was controlled through a serial port. It was connected to a computer that was capable of sending information to the device to print it. The data was made by a sequence of finite symbols such as ASCII characters, with a fixed font. These devices acted as user interfaces for early computers, so they were—in a sense—precursors to the modern screens.

When screens to replaced printers as output devices, their content was organized in a similar fashion: a two dimensional matrix of characters. In their early stages they were called glass TTY, and the character display was still part of the display itself, controlled by its own logic circuits. With the arrival of the first video display cards, computers were capable of having an interface that was not hardware-dependent.

Text-only consoles used as a main interface for operating systems inherit their name from TTY and are referred to as consoles. Even if the OS runs a graphical environment like on a modern OS, a user can always access a certain number of virtual consoles that work as a Command-Line Interface (CLI), often referred to as a shell.