Terminal emulator

A terminal emulator, terminal application, term, or tty for short, is a affairs that emulates a video terminal aural some added affectation architecture. Though about alike with a command band carapace or argument terminal, the appellation terminal covers all limited terminals, including graphical interfaces. A terminal adversary central a graphical user interface is generally alleged a terminal window.

A terminal window allows the user admission to a argument terminal and all its applications such as command band interfaces (CLI) and argument user interface applications. These may be active either on the aforementioned apparatus or on a altered one via telnet, ssh, or dial-up. On Unix-like operating systems it is accepted to accept one or added terminal windows affiliated to the bounded machine.

Terminals usually abutment a set of escape sequences for authoritative color, cursor position, etc. Examples cover the ancestors of terminal ascendancy arrangement standards accepted as ECMA-48, ANSI X3.64 or ISO/IEC 6429.

Early adopters of computer technology, such as banks, allowance companies, and governments, still accomplish common use of terminal emulators. They about accept decades-old applications active on mainframe computers. The old "dumb" video terminals acclimated to admission the mainframe are continued back obsolete; however, applications on the mainframe are still in use. Quite often, terminal emulators are the alone way to admission applications active on these earlier machines.

Local echo

Terminal emulators may apparatus a bounded answer function, which they may afield name "half-duplex" (Half-duplex is altered altogether), or still hardly afield "echoplex" (which is formally an absurdity apprehension apparatus rather than an ascribe affectation option).1234 For data of the bounded answer ascendancy mechanisms of terminal emulators, see the capital article.

Line-at-a-time mode/Local editing

Terminal emulators may apparatus bounded editing, aswell accepted as "line-at-a-time mode". This is aswell afield referred to as "half-duplex". In this mode, the terminal adversary alone sends complete curve of ascribe to the host system. The user enters and edits a line, but it is captivated locally aural the terminal adversary as it is getting edited and not transmitted until the user signals (usually with the ↵ Enter key on the keyboard or a "send" button of some array on the user interface) the achievement of the line. At that point the absolute band is transmitted. Of course, line-at-a-time approach implies bounded echo, back contrarily the user will not be able to see the band as it is getting edited and constructed.15 However, line-at-a-time approach is absolute of answer approach and does not crave bounded echo. When entering a password, for example, line-at-a-time access with bounded alteration is possible, but bounded answer is angry off (otherwise the countersign would be displayed).6

The complexities of line-at-a-time approach are exemplified by the line-at-a-time approach advantage in the TELNET protocol. To apparatus it correctly, the Network Virtual Terminal accomplishing provided by the terminal adversary affairs have to be able of acquainted and appropriately ambidextrous with "interrupt" and "abort" contest that access in the average of locally alteration a line.7

Synchronous terminals

In asynchronous terminals abstracts can breeze in any administration at any time. In ancillary terminals a agreement controls who may forward abstracts when. IBM 3270-based terminals acclimated with IBM mainframe computers are an archetype of ancillary terminals. They accomplish in an about "screen-at-a-time" approach (also accepted as block mode). Users can accomplish abundant changes to a page, afore appointment the adapted awning to the limited apparatus as a individual action.

Terminal emulators that simulate the 3270 agreement are accessible for a lot of operating systems, for use both by those administering systems such as the z9, as able-bodied as those application the agnate applications such as CICS.

Other examples of ancillary terminals cover the IBM 5250, ICL 7561, Honeywell Bull VIP7800 and Hewlett-Packard 700/92.

Examples of terminals emulated

Many terminal emulators accept been developed for terminals such as VT100, VT220, VT320, IBM 3270/8/9/E, IBM 5250, IBM 3179G, Data General D211, Hewlett Packard HP700/92, Sperry/Unisys 2000-series UTS60, Burroughs/Unisys A-series T27/TD830/ET1100, ADDS ViewPoint, Sun console, QNX, AT386, SCO-ANSI, SNI 97801, Televideo, and Wyse 50/60. Additionally, programs accept been developed to challenge added terminal emulators such as xterm and different animate terminals (e.g., for Linux). Finally, some emulations artlessly accredit to a standard, such as ANSI. Such programs are accessible on abounding platforms alignment from DOS and Unix to GUI operating systems such as Windows and Macintosh, to anchored operating systems begin in cellphones and automated hardware.