windowing environment. This arrangement permits terminal-like interaction with the computer (for running a command-line interpreter, for example) without the need for a physical terminal device; it can even run multiple terminal emulators on the same device. Capabilities Character-oriented terminal A character-oriented terminal is a type of computer terminal that communicates with its host one character at a time, as opposed to a block-oriented terminal that communicates in blocks of data. It is the most common type of data terminal, because it's easy to implement and program. Connection to the mainframe computer or terminal server is achieved via RS-232 serial links, Ethernet or other proprietary protocols. Text terminals A text terminal, or often just terminal (sometimes text console) is a serial computer interface for text entry and display. Information is presented as an array of pre-selected formed characters. When such devices use a video display such as a cathode-ray tube, they are called a "video display unit" or "visual display unit" (VDU) or "video display terminal" (VDT). The system console is often a text terminal used to operate a computer. Modern computers have a built-in keyboard and display for the console. Some Unix-like operating systems such as Linux and FreeBSD have virtual consoles to provide several text terminals on a single computer. The fundamental type of application running on a text terminal is a command-line interpreter or shell, which prompts for commands from the user and executes each command after a press of . This includes Unix shells and some interactive programming environments. In a shell, most of the commands are small applications themselves. Another important application type is that of the text editor. A text editor typically occupies the full area of display, displays one or more text documents, and allows the user to edit the documents. The text editor has, for many uses, been replaced by the word processor, which usually provides rich formatting features that the text editor lacks. The first word processors used text to communicate the structure of the document, but later word processors operate in a graphical environment and provide a WYSIWYG simulation of the formatted output. However, text editors are still used for documents containing markup such as DocBook or LaTeX. Programs such as Telix and Minicom control a modem and the local terminal to let the user interact with remote servers. On the Internet, telnet and ssh work similarly. In the simplest form,