OS - Terminal (Emulator) (Term|tty)

1 - About

A terminal is a media using a fixed-pitch character grid such as:

  • teletypes,
  • portable devices with limited display capabilities
  • bank terminal
The term terminal cover all terminals:

A terminal introduces the context of output where to draw and/or write data.

This article talks about text terminal.

A terminal emulator, terminal application, term, or tty (teletypewriter), is a program that emulates a terminal.

3 - features

Example:

  • Native Windows user interface with a simple options dialog.
  • Easy copy & paste.
  • Drag & drop of text, files and folders.
  • Ability to open files and URLs with Ctrl+click.
  • Comprehensive character encoding support, including UTF-8.
  • Wide character display and Windows IME support.
  • Window transparency, including glass effect on Vista and 7.
  • 256 colours.
  • Fullscreen mode.
  • Options stored in a text file. No registry entries.
  • Small program size and quick scrolling.

4 - Text

The role of a text terminal (emulate process or not) is to interact with the user:

  • to feed text input to the master pseudo-device for use by the shell (which is connected to the slave pseudo-device)
  • and to read text output from the master pseudo-device and show it to the user.

The terminal emulator must also handle terminal control commands, e.g., for resizing the screen.

A terminal window allows the user access to a text terminal and all its applications such as:

When user starts terminal, it runs generally by default a OS Shell or a console application (cli).

5 - Locality

The terminal may be running:

  • either on the same machine: local
  • or on a different one remote

5.1 - Local

A local terminal is also known as a console window.

On Unix-like operating systems, it is common to have one or more terminal windows connected to the local machine.

5.2 - Remote

Remote terminals connect to remote hosts to run applications remotely.

The terminal may run on a remote machine via:

6 - List

List_of_terminal_emulators

7 - Escape sequences

Terminals usually support a sequence of characters called an escape sequences for controlling color, cursor position, etc.

7.1 - Color

8 - Terminal emulator

8.1 - Local login

  • GNOME Terminal,
  • Konsole
  • and Mac OS X Terminal.

8.2 - Remote Login

Remote login handlers such as ssh and telnet servers play the same role but communicate with a remote user instead of a local one.

8.3 - With session context

Screen and Tmux are used to add a session context to a pseudo terminal. For example, it provides terminal persistence allowing to disconnect from one computer and connect later on from another computer on the net.

the Linux console behaves almost like a vt100 terminal

Pseudo-Terminal

PuTTY is an example of a virtual terminal.

Virtual Terminal (VT) series:

Many terminal emulators have been developed for terminals such as:

If not, screen implements a superset of vt100 and vt100 is universal

pseudo-terminal normal login session

if the current session has no tty

9 - Documentation / Reference


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