Preface

VT100

This document accompanies the KTerm and Kom programs, which are mainly terminal emulations. Since material about the extend and precise semantics of the emulatation intended by these programs is hard to find on the internet today, it came out nessesary to include a more precise specification within their release. Hopefully, this helps to clearify the relation to the VT100, VT102, Linux, XTerm and ansi.sys (ANSI-BBS) terminals, which are the target of these programs. Further, it specifies which codes are interpreted by them, and what has been omitted. To begin with, all of the above call themselfes "ANSI" emulations, which makes this notion pretty vage. "ANSI" referes here to the American National Standards Institute's documents X3.41-1974 and X3.64-1977. DEC partially implemented this standart in their VT100 terminal, with some additions. The VT102 is a later extention of that. Both the Linux console and the XTerm emulation implement most of VT102, with some additions. MS stepped in later and produced another ANSI emulation, ansi.sys, for their OS, which became of some relevance in BBS style telecommunication programs. One can view this as a small subset of the VT100 emulation, with some additions, of cause. This situation is further confused by the fact, that often many versions of the above terminals and emulations are out, one able to do a little more or less then the other. Especially the later makes the production of a working emulation an impossible task. And this is the place where this document steps in:

Editor's notes & todos

• Include complete reference on keyboard material.
• Check for explaination of out-of-bound values.
• Include VT52, VT102, XTERM, LINUX-console codes
• Translate to codes to decimal
• Make the whole document more concept oriented
• See the section Method of description, below

Terminal Control Commands

The VT100 is compatible with both the previous Digital standard and ANSI standards. Customers may use existing Digital software designed around the VT52 or new VT100 software. The VT100 has a "VT52 compatible" mode in which the VT100 responds to control sequences like a VT52. In this mode, most of the new VT100 features cannot be used.

Throughout this document references will be made to "VT52 mode" or "ANSI mode". These two terms are used to indicate the VT100's software compatibility.

NOTE: The ANSI standards allow the manufacturer flexibility in implementing each function. This document describes how the VT100 will respond to the implemented ANSI central function.

Method of description

Parts of the terminal description

• State
  This is mainly the screen, the cursor (including it's graphical state) and some hidden mode variables. Note that the state cannot be investigated by the attached host.
• Interface
  That's what goes over the wire. Beside being related to objects, this appears so closely related to contemporal process communication, that it might be discussed in likely terms.
  We have information flowing in both directions. On could destinguist between:
• Commands
  These are "calls" of the terminals interface by the host which cause some change of the terminals state, but do not end in a response.
• Requests
  These are "calls" of the terminals interface by the host which do not cause any change of the terminals state, but end in a response of the terminal. Clearly, requests are somehow used to investigate the state of the terminal.
• Events
  These are signals from the terminal caused by the user affecting the mouse or keyboard to the host.
• Replys
  These are send by the terminal as a result of a Request from the hosts.
• Encoding/Decoding
  Since the

Control Characters

Control characters (codes 00 - 037 inclusive) are specifically excluded from the control sequence syntax, but may be embedded within a control sequence. Embedded control characters are executed as soon as they are encountered by the VT100. The processing of the control sequence then continues with the next character recieved. The exceptions are: if the <ESC> character occurs, the current control sequence is aborted, and a new one commences beginning with the <ESC> just recieved. If the character <CAN> (030) or the character <SUB> (032) occurs, the current control sequence is aborted. The ability to embed control characters allows the synchronization characters XON and XOFF to be interpreted properly without affecting the control sequence.

Control Character	Octal Code	Action Taken
<NUL>	000	Ignored on input; not stored in buffer
<EN>	005	Transmit the ANSWERBACK message. The answerback message can be loaded in SET-UP B (i.e. is a configurable string).
<BE>	007	Sound bell
<BS>	010	Move cursor to the left one position, unless it is at the left margin, in which case no action is taken.
<HT>	011	Move cursor to the next tab stop, or to the right margin if no further tabs are set.
<LF>	012	Causes either a line feed or new line operation (See new line mode.)
<VT>	013	Same as <LF>.
<FF>	014	Same as <LF>.
<CR>	015	Move the cursor to the left margin of the current line.
<SO>	016	Invoke the G1 character set, as designated by the SCS control sequence.
<SI>	017	Invoke the G0 character set, as selected by the <ESC>( sequence.
<DC1>	021	Causes terminal to resume transmission (XON).
<DC3>	023	Causes terminal to stop transmitting all codes except XOFF and XON (XOFF).
<CAN>	030	If sent during a control sequence, the sequence id immediately terminated and not executed. It also causes the error character (checkerboard) to be displayed.
<SUB>	032	Same as <CAN>.
<ESC>	033	Introduces a control sequence.
<DEL>	177	Ignored on input; not stored in buffer.

Control Sequences

Definitions

Control Sequence Introducer (CSI):

An escape sequence that provides supplementary controls and is itself a prefix affecting the interpretation of a limited number of contiguous characters. In the VT100, the CSI is: <ESC>[

Parameter:

1. A string of zero or more decimal characters which represent a single value. Leading zeros are ignored. The decimal characters have a range of 0 (060) to 9 (071).
2. The value so represented.

Numeric Parameter:

A parameter that represents a number, designated by Pn.

Selective Parameter:

A parameter that selects a subfunction from a specified set of subfunctions, designated by Ps. In general, a control sequence with more than one selective parameter causes the same effect as several control sequences, each with one selective parameter, e.g., CSI Psa; Psb; Psc F is identical to CSI Psa F CSI Psb F CSI Psc F.

Parameter String:

A string of parameters separated by a semicolon.

Default:

A function-dependent value that is assumed when no explicit value, or a value of 0, is specified.

Final character:

A character whose bit combination terminates an escape or control sequence.

                      Delimiters
                          / \       
                         /   \       
                         |   |
                        \ / \ /
Sequence:       <ESC>[ 0 ; 4 ; 5 m
                ^^^^^^ ^   ^   ^ ^
                |||||| |   |   | |
                \||||/  \  |  /  +------Final character
                 \||/    \ | /
                 CSI   Selective
                       Parameters

   033 0133 060 073 064 073 065 0155
  <ESC>   [   0   ;   4   ;   5    m

• <ESC>[;4;m
• <ESC>[m
<ESC>[4m
<ESC>[5m
• <ESC>[0;04;005m

The following text conforms to these formatting conventions:

• Control characters are designated by angle brackets (e.g. the Escape character is <ESC>).
• Parameters are indicated by curly braces.
• Parameter types usually are indicated as one of:

  {Pn}	A string of digits representing a numerical value.
  {Ps}	A character that selects an item from a list.
  {a-z}	Any lowercase sequence of one44 or more characters in braces represent a value to be entered (as in {Pn}), and the name in the braces will be referred to in explanatory text.

• Spaces in the control sequence are present for clarity and may be omitted. Spaces which are required will be surrounded by single quotes: ' '.
• All other characters are literals.

The following attributes below have the following meaning:

• VT100 - This code is known to VT100.
• ANSI - This code is defined by ANSI.
• DEC - This code is DEC private.
• Command - Sent from host to the terminal. FIXME:add Inquiery.
• Reply - Sent from terminal to the host (as response to an Inquiery).
• Event - Sent from terminal to the host (caused by a user activity).
• Mode - The entry is a mode.

Modes

ANSI Specified Modes

DEC Private Modes

The following modes, which are specified in the ANSI standard, may be considered to be permanently set, permanently reset, or not applicable, as noted.

Mnemonic	Function	State
CRM	Control Representation	Reset
EBM	Editing Boundary	Reset
ERM	Erasure	Set
FEAM	Format Effector Action	Reset
FETM	Format Effector Transfer	Reset
GATM	Guarded Area Transfer	NA
HEM	Horizontal Editing	NA
IRM	Insertion-replacement	Reset
KAM	Keyboard Action	Reset
MATM	Multiple area transfer	NA
PUM	Positioning Unit	Reset
SATM	Selected Area Transfer	NA
SRTM	Status Reporting Transfer	Reset
TSM	Tabulation Stop	Reset
TTM	Transfer Termination	NA
VEM	Vertical Editing	NA

Keyboard Codes

Special Graphics Characters

NOTE 2: Codes 0157-0163 give better vertical resolution than dashes and underlines when drawing graphs; using these segments, 120 x 132 resolution may be obtained in 132 column mode with the Advanced Video Option installed.

References

Other Material

Petri Virekoski has posted the following document to comp.terminals in 1993.
I have htmlized and edited the document 1998 to provide the KTerm program with proper reference material.

I'm mentioning the original author here only to honor his work, he has nothing to do with KTerm, so do not bother him with any questions. This information is largely derived from DEC document EK-VT100-UG-003, the original manual for the VT100.

Most so-called VT100 implementations (both stand-alone terminals and PC emulators) actually implement more controls than are given here. The minimal standard is really the slightly more advanced VT102 terminal.

...RSS

Path: cs.utk.edu!gatech!usenet.ins.cwru.edu!agate!doc.ic.ac.uk!pipex!sunic
      !trane.uninett.no!news.eunet.no!nuug!news.eunet.fi!funic!nntp.hut.fi
      !lk-hp-14.hut.fi!pev
From: pev@lk-hp-14.hut.fi (Petri Virekoski)
Newsgroups: comp.terminals
Subject: VT100 control info
Date: 11 Sep 1993 12:43:22 GMT
Organization: Helsinki University of Technology
Lines: 878
Distribution: world
Message-ID: <26sh5a@nntp.hut.fi>
NNTP-Posting-Host: lk-hp-14.hut.fi

This file describes information needed for controlling the VT100 terminal from a remote computer. All of the information was derived from the VT100 user's manual, Programmer's Information section. Full documentation can be obtain from DIGITAL'S Accessory and Supplies Group.

This text is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. If you want to have a reliable source of the topic concerned, you find the references to them listed in the reference section.

I've put this document together from several sources, htmlized and edited them to become a whole. All of the originals where postings on the comp.terminals. You can find them collected in http://www....

The original authors left the copyright open, but clearly intended to make their work public, so i feel free to make the above said use of it. They are namely:

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(_/  ( ! / )   Petri Virekoski ------ pev@vipu.hut.fi ------
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