# General Information

### Applicable to most character-cell/remote-graphics terminals

(skip to links)

A Web essay by Tom Van Vleck gives us some perspective on how serial computer terminals have been used and improved since the 1960s. For glimpses of how computer hobbyists of the early 1980's used character-cell video terminals with the home computers of the day, you can visit a library and look up these articles ftom BYTE magazine.

Information on setting up a Unix or Linux system for use with terminals or terminals emulations is here, whereas, information on terminal emulations themselves is here.

When you are trying to use any dumb terminal (or even a smart terminal) with a remote host, it is helpful to remember that there are two sets of parameters in play:

- settings within the local terminal that determine exactly how it will behave
- information that the remote host computer has about what type of terminal it is talking to

The two sets of parameters interact: the host computer can sometimes discover how the local terminal is set, and the computer will likely adjust what control characters it sends according to its guess of how the video terminal may behave.

If you need beginner's help on how to login to a Unix system using a terminal, you can start by reading this introductory video-terminal tutorial for Unix by Anthony Lawrence. You can also read introductory Unix materials from here at the University of Tennessee, or you can read an equivalent introduction to Linux. A few common terminal-related questions are answered in the Boston University Unix User's Guide.

You can read this Introduction to Telnet, describing the Internet's original remote-terminal protocol. And it may be helpful to look at the "telnet" section of the TCP/IP Frequently-Asked Questions document. (And there is the "Mini-FAQ" on TCP/IP applications. On the other hand, if you just want some fun, you can sing The Telnet Song or just look at the currently lighted face of Earth in ASCII. Dmoz.org lists some Unix-shell-access providers, and the the Noise-Level Zero conferencing system a web-page telnet interface.)

To view the text parts of web pages using a character-cell terminal, you can use the Lynx web browser.

But, if you have some idea of using a character-cell terminal to connect to a remote computer running Microsoft's Windows NT, you'd better read this first, and then have a look at this.

(return to Video Terminal index page)

## User Issues

- General news about terminals.
- Miscellaneous terminal discussions.
- Discussion on prices of terminals and costs of using them.
- Commercial products for terminal emulation.
- Discussion of using and programming video terminals under UNIX and Linux.
- Controlling the flow of serial data is often important. (especially for users of Emacs....)
- "But why can't the computer do a command when I type Control-S?
- On using the simple "answerback" function.
- Considerations about the screen itself, be it CRT or LCD.
- On the other hand, who needs a CRT? Flat screens are k00l.
- Should you turn off your screen at night?
- Discussion of how to repair your video terminal when it breaks.
- Terminal servers connect serial terminals to computers via IP networks.
- Discussion of the "telnet" login-session protocols, some SSH info.
- Discussion of SSH/Secure Shell protocol and implementations.
- UNIX "csh" hack to reset VT100-type screens.
- Comments on setting up modems for terminal sessions and file transfer.
- You need a "null modem" to connect two RS-232 DTE devices.
- Information on safe and ergonomic user of terminals.
- Information on xterm.
- Information on keyboards and other input devices.

## Programmer/Administrative Issues

- Commentary on ANSI terminal controls, especially in DEC products.
- Summary of ANSI X3.64 Standard (basis for ISO 6429) control codes.
- A sample page from the ANSI X3.64 document. (GIF)
- ECMA-48 Standard (derived from X3.64) (PDF)
- ANSI X3.64/ECMA-48 Escape Sequence Concordance (Ben Harris)
  (or by FTP)
- How a program can tell what type of terminal it is talking to.
- General discussion of control sequences.
- How "private" control functions of a terminal may be used.
- Discussing how to translate codes between terminal types.
- What to think about when inventing terminal emulation on a PC.
- MIT's parser for DEC VT420 control sequences (C source code/zip)
- Some discussion about the GNU "screen" software package (or read a description of its functions).
- A very simplified discussion of RS-232-C serial wiring
- The experts on DECUServe had a discussion of serial data communication (and other things).
- Information on USB, the "Universal Serial Bus"
- USB Frequently Asked Questions (PDF, via Hewlett-Packard)
- On printing to a printer attached to the terminal.
  (Rasmussen Software has a FAQ page which mentions passthrough printing...link works in 2009) ::::.
- When the terminal sends and receives entire forms in block mode.
- News about NAPLPS, a remote graphics protocol (used by Prodigy).
- Technical specification for NAPLPS protocol (index)
- AlphaWindow character-cell windowing protocol.
- AT&T developed the "layers" terminal-control protocol, as used in the AT&T 5620 Terminal.
- A Guide to Telnet (Anzio.com)
- Character sets: ASCII, EBCDIC, Unicode, line-drawing, accented, & code pages
  (with new discussion of Euro currency symbol)
- New character sets for global and multilingual communication (Unicode and/or ISO 10646)
- Unicode 16-bit code space allocation.
- Musings about the history of the ASCII code.
- Korn shell script to show printable characters.
- DEC MCS Character Set Discussion
- Tom Jennings' Essay about the history of the ASCII code. (www.wps.com)
- Table of ASCII codes. (text)
- C include file for ASCII control codes.
- Victor Eijkhout's TeX ASCII chart.
- How to control the color of characters on a terminal screen.
- Color-Coded ASCII chart (Jim Conner)
- ASCII Chart with Key Scan Codes and Line-Drawing Info (Jim Price)
- Chinese typing via "wubi" input method. (wubizixing: wicentow)
- How to read Chinese text on Usenet. (faqs.org)
- Macintosh Character Encoding, including Oriental (Apple)
- Table of EBCDIC codes. (GIF)
- Information on setting up your operating system to support character-cell video terminals.
- Wikipedia entry on "text terminal".

- BitFontEdit: Soft font editor for Wyse and VT220 terminals (Lawyer)
- JPIG: display JPEG images on the Linux text console

Supporting different kinds of terminals...
Unix and Linux systems typically supply a function library and a database that permit applications programs to work with many different kinds of character-cell terminals. The library is "curses" (or "ncurses") and the database is either "terminfo" or "termcap".

Here you can read some archived discussion of the termcap and terminfo databases, and the curses library, and how the entries control the attributes of displayed data.

Also, Tony Lawrence has placed on his website some general principles of programming for terminals using terminfo and termcap.

O'Reilly & Associates published a book called termcap & terminfo by John Strang, Linda Mui, and Tim O'Reilly. From the same publisher, another helpful book is Programming with curses by John Strang, which describes the UNIX library of functions for controlling a terminal's display screen from a C program.

The original reference on curses is the BSD project documentation volume Screen Updating and Cursor Movement Optimization (here in PDF). Now, however, curses functions are part of the X/Open Unix Standard, as documented here.

Another book is UNIX Curses Explained by Berny Goodheart (Prentice Hall, ISBN 0-13-931957-3), which discusses programming both using the curses package and using low-level control codes obtained directly from terminfo. And there is Pradeep Padala's NCURSES Programming HowTo.

A book on a related topic is The Working Programmer's Guide to Serial Protocols by Tim Kientzle. This volume discusses Kermit, Zmodem, and other protocols, and provides sample code in C++. Although now out of print, you may possibly be able to locate a copy. Select this and that to find out more. Some source code described in the book is available here at the Dr. Dobbs site.

If you need a different termcap or terminfo entry for some particular terminal, you can get it from Eric Raymond's comprehensive master terminfo file.

Another way to cope is to repair the terminal-database entry yourself. Walter Zinz of Unix World wrote chronicles of how he repaired the termcap and terminfo entries for his AT&T 7300 screen.

Another possible reference book, this one readable directly from the Internet, is

         UNIX Hints and Hacks
         by Kirk Waingrow.
         Copyright 1999 MacMillan/Que.
         ISBN 0-7897-1927-4.

Here is the chapter describing character-cell terminal displays and emulations. (courtesy of umd.edu)

Some may wish to read about AIX's low-function terminal subsystem.

## Software elsewhere on the Internet

- qterm is a program originated by <jmg@dxcoms.cern.ch> (and now maintained in release 6.0 by <mcooper@usc.edu>) that helps a Unix computer identify which type of remote terminal it is talking to.
  (You can retrieve an older qterm from the archive here or from its original location.)
- Another Unix program for identifying the remote terminal type is termset.
- SimTel NAPLPS graphics-protocol utilities (MS-DOS index)
- GNU termcap man pages (or from Europe try T. U. Wein's copy)
- Text Terminal "How To" (Lawyer)
- Linux serial-port "How To"
- Linux "How To" Index (tldp.org)
- Linux utilities for terminal port settings (sunsite/unc)
- The Computer Journal had an "asynchronous serial data communications" page for MS-DOS and embedded systems. As of 2006, there is an online archive of David Baldwin's article.
- Curses Extension to Perl (perl.com/Setzer) :.
- spinner: anti-idle-disconnect utility, keep sessions alive (BSD, Linux) ::.
- The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets No Excuses! (Joel Spolsky)
- VT52VNC: AT&T Virtual Network Computing client for VT52 video terminals
- charva: character-cell-terminal implementation of Java AWT (Pitman)
- TUIpeer: Text User Interface for the Java AWT
- GNU screen software package
- slang display library (alternative to "curses")
- Perl telnet module (Jay Rogers)
- Robert de Bath's Utility Software (includes "filt" to remove ANSI Escape sequences)
- Advice on Telnet Character Sets for Arabic Speakers (Knut S. Vikør)
- Open SSL/TLS
- OpenSSH (secure shell)
- SSH FAQ (secure shell)
- SSH: The Definitive Guide (FAQ from Snailbook)
- Blast Software (data transfer, communication)
- Kermit Project's print utilities (HP4L, HP5L, etc.)
- DVItoVDU (terminal-screen previewer for TeX DVI files using PK fonts)
- pdcurses: "closest thing to ncurses (or Unix SysV curses) on MS-DOS or OS/2"

## Terminal-Related Information Elsewhere on the Internet

Usenet (inet) newsgroup: comp.terminals

Christian Blum wrote an excellent essay The_Serial_Port. For TP access to that and several other of his useful files, select this. (Here is the Web location at "repairfaq.org".)

> (As of April 2005, with excessive traffic to the "repairfaq.org" domain, Sam Goldwasser has provided mirror sites.)

You can read an interview with the president of Wyse Technology to learn his view of the future of thin clients. Another approach to the "thin client" is Sun's SunRay desktop appliance.

Several thin-client technologies are on display at the Thin Planet.

- Celeste's Unix Serial Port Resources (moved to Sunhelp.org)
- Terminal-capability databases (termcap/terminfo) (by Eric Raymond... or see local copies of terminfo and termcap files)
- Introduction to Using the Unix "termcap" library (fnal.gov)
- ncurses "new curses" Home Page (gnu.org)
- ncurses (Thomas E. Dickey's page)
- ncurses 3x manpage
- Zeyd M. Ben-Halim's ncurses FTP directory
- Curses Development Kit (Dickey/Glover: A library of widgets)
- Curses Development Kit (Vexus: a different CDK)
- dialog (Dickey/Lam: script-driven curses widgets)
- C. B. Browne's Text-User-Interface Tool Index
- The Minor Scroll of Console Knowledge documents many hardware aspects of serial communication. (David K. Z. Harris)
- Beyond Logic's Interfacing Resources (serial, parallel, USB, etc.)
- USB Frequently Asked Questions (usb.org) :::
- Hugo Villeneuve's Practical Notes on Serial Ports and RS-232
- Tutorial on RS-232 Serial Interface and Connectors
  (ARC Electronics--see also other technical references from ARC)
- Filip Gieszczykiewicz's Connector Pinout Data (2002 link)
- Chan's Pinouts Page (Annex, Cisco, SGI; link good in 2006) :::
- Keyboard, Monitor, Mouse Pinouts (incl. KVM, DFP, EVC, Firewire, USB) :::
- Portmon (utility to monitor serial and parallel port activity on a Windows system)
- Steve Walz Dispels RS-232-C Confusion.
- Hardware Book (cable/connector descriptions) :::
- Cisco 4000 IOS modem connectors (rolled RJ-45 cables)
- Build a Video Terminal with Teletext ICs (Åke Holm)
- Build a Simple Tiny Converter: TTL to RS-232
- Dawn Rorvik's Technical Notes (evergreen.edu)
- Tony Lawrence explains "Serial Wiring and Communications for the Confused".
- Kerberos meets Ali Baba and the 40 Thieves (web.isi.edu)
- Kerberos Security/Authentication Protocol (web.mit.edu)
- How to Kerberize Your Site for Security (ornl.gov)
- Kerberos and GSSAPI Support in OpenSSH (sxw.org.uk)
- Serial Programming Guide for POSIX Operating Systems
- SerProxy (redirect TCP/IP socket to serial connection)
- Ser2Net (serial to network proxy, via sourceforge.net)
- Remote Access Technology Summaries (by John Wobus, via system75.com)
- Yost Serial-Device Wiring scheme (now on Yost.com)
- USB Product Developer Resources (usb.org)
- Lantronix Ubox: (extend USB connections across the Internet)
- Keyspan, Inc. (USB/Serial/RS-232-C/Firewire/Remote adapters for Mac OS X, Linux, and Windows)
- AirCable (Bluetooth to RS-232-C serial adapter) :::::
- Sena Technologies (device servers, serial Ethernet, and now Bluetooth-to-serial adapters!)
- Macintosh Serial-Port Interfacing (Utah page) :::::
- Serial RS-232-C information from a Macintosh point of view (Webarchive link) :::::
- Add a Serial Port to Your Mac (planet-rcs.de page) :::::
- SCO/Caldera/Unixware Unix termcap and terminfo changes (UUnet)

## Standards and other Reference information elsewhere on the Internet

- Frequently Asked Questions about computer standards (from Usenet)
- Hal Jespersen's links to computer standards information
- ModemHelp.Net
- Everything you ever wanted to know about modems (C. Ostmo)
- Navas Group Dial-Up Modem FAQ (for 28.8k to 56k bps)
- Navas Group Cable-Modem/DSL Tuning Guide
- TCP/IP Resources (extensive list by Raz Uri)
- Kermit/Columbia warns about RPI and Winmodems....
- Free On-Line Dictionary of Computing (or try the InstantWeb mirror--the Princeton mirror seems to have died)
- People Helping One Another Know Stuff (about terminals) (PHOAKS)
- University of Nebraska--Lincoln/Engineering Electronics Shop (2006 link)
- Usenet sci.electronics Electronic Repair FAQs (new URL)
- This Old 486
  Display/CRT/Video Issues
- Monitor Buyer's Guide (graphically conducted by ViewSonic)
- The Fixed-Frequency PC Video FAQ (devo.com)
- Connecting a Fixed-Frequency Monitor to a Linux PC (uni-wuerzburg)
- Using a Fixed-Frequency Monitor on PC (Mike Frisch)
- Fundamentals of color video display on CRTs (Duff/Netlib)
- Essay on Monitor Resolution and Bandwidth (Butler)
- 13W3 Connector Pinout
- Videotronics (monitor repair information)
- World Wide Web Monitor Database (Hercules)
- Mirage Fixed-Scan Monitor Support
- Arcade VGA fixed-frequency 15-kHz display adapter (ultimarc.com)
- Software Integrators, Inc. (fixed-scan monitor support)
- Extron Electronic/RGB Systems (computer/TV scan converters, video accessories)
- Tandberg Display A.S. (Norwegian site)
- Hi-Tech Surplus Components (new link)
- Computercraft Hardware Support (updated link)
- Circuit Cellar, Inc. (Steve Ciarcia's versatile enterprise)
- Dave Tweed's Circuit Cellar index
- Here's Jerry's Website too, so he won't get jealous...
- And, for good measure, Don Lancaster's Guru's Lair.
- termcap entry for Rassmussen's "Anzio" terminal emulator (ftp) ::::.
- terminfo (tic) entry for Rassmussen's "Anzio" terminal emulator (ftp) ::::.
- Various terminal-type parameter files maintained by Stratus Computer
  Character Sets
- ECMA Standards include many character-set specifications
- The Unicode Home Page (with Unicode FAQ, part of which is a UTF-8 FAQ. New, improved! Now contains ZWNBSP!)
- Unicode Consortium FTP archive
- Microsoft article: Unicode support in Win 32 (self-extracting .exe)
- ISO 8859-1 National Character Set FAQ (tuwien.ac.at)
- ISO 8859 8-bit character sets for Western alphabets (Czyborra.com)
- ISO/IEC Joint Technical Committee-1/SC2/WG3: Character Sets (dkuug)
- Multilingual enhancement to GNU Emacs 19 (or a pointer)

## Organizations

- curses terminal/screen-handling functions in X/Open Unix Standard
- OpenGroup Full-Text Publications on the Web (Unix documents)
- International Committee for Information Technology Standards (INCITS)
  (formerly "ANSI Accredited Standards Committee X3 on Information Technology")
- American National Standards Institute (ANSI)
- NSSN: A Global Standards Network (project of ANSI)
- InterNational Committee for Information Technology Standards (INCITS, formerly X3) (2003)
- INCITS X3L2 Technical Committee on Codes and Character Sets (2003: formerly ANSI X3L2)
- ECMA: European association for standards
- International Organization for Standardisation (ISO)
- Order catalog of ISO JTC1/SC2 Standards for Coded character sets
- Order catalog of ISO JTC1/SC21 OSI (Open Systems Interconnection)
- IEEE Standards FAQs (ieee.org)
- Parent of POSIX (IEEE Portable Applications Standards Committee)
- Electronic Industries Association (EIA)
- International Telecommunications Union (ITU)
- Computer and Communication Standards Resources (cmpcmm.com)
- Indie Women on the Verge of Terminal Boredom :-)

## Internet RFCs (Request for Comment Documents)

- Telnet Terminal-Type Option (RFC-1091)
- Character Sets on the Network (RFC-1345)
- RFC Archive from faqs.org

## Vendor Information

- Bomara Associates (data and telecommunications products)
- Mod-Tap Cabling Systems (including residential... now the Premise Networks division of Molex)
- Mike Sandman's Serial-Port, PC, and Telephony Accessories
- Blue Hills Innovations (serial cables for GPS and PDA products)
- PN Technologies (Purple Data Cables for PDA and GPS products)
- Denkart, Inc. (Wingspan emulation software library, new link)
- Yahoo's Web Links for Computer Peripherals (2002)
- PC Webopaedia (Sandy Bay Software)
- Maven: Purchasing Advice (NTSL/McGraw-Hill)
- Tactical Software LLC (sharing modems and serial devices among Windows PCs)

A partial list of dealers who sell new and used video terminals is here.

Video Terminal index page
Information on DEC terminals.
Information on IBM terminals.
Information on Televideo terminals.
Information about "various" terminals: many types, including Wyse/Link, ADDS, ADM, HP, AT&T, Volker-Craig, Tektronix, etc.
Information on terminal emulation (on a PC or otherwise).
Information on terminal emulation in X Windows in Unix and Linux, especially xterm.
Information on keyboards, mice, and other user-input devices.
Advice on setting up an operating system to use terminals.
Tangental information on technologies for display of data.
Links to various computing technology.

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Introductory material copyright © 1995, 2005
and archive contents collection copyright © 1995, 1999, 2003, 2005, & 2008 Richard S. Shuford.

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