Terminal Emulators

The great thing about running emulators like VT100 or VT320 is that they do cursor addressing and other fun stuff.

SimH supports it, but not through the Console (which becomes Port zero in IRIS).
To make it work, you need to run a Telnet session on your computer and connect to SimH. That is actually an advantage anyway, because you get to have 2 interactive ports. Which is really handy for debugging: you can run a new program on 1 port and DSP or some monitor on the other.

Running a Telnet session is fairly simple. It just requires a few steps.


  • Within IRIS, you need $TERMS and $TERMVT100 (or other terminal) enabled.
  • A Telnet client that supports VT100 (example). The default on Windows will do (see below).

Once IRIS is booted, escape to the ‘sim>’ prompt (via CTL-E or CTL-F) and type.
ATTACH TTI1 <port>
replacing ‘<port>’ with a number that is a free TCP/IP port on your computer, say 1401. Press <return>.
Resume IRIS by typing ‘C’ for ‘continue’ and <return>. Make sure IRIS is running on the console.

Some versions of SimH Nova.exe (prior to 9/26/2016) may freeze up at this point. If that happens, get the most recent version.

Now get the Telnet session running and connected.
Every Telnet program is different, so we will try to document them all eventually. Misc. notes:

  • Any time the console is in ‘sim>’ mode, all execution in the Nova stops, which means the Telnet session appears frozen. Keep the console in IRIS in order to run.
  • Most Telnet programs will be unable to beep on errors. I think this has to do with how the sound system works in Windows. If anyone can solve this, let us know!
  • See Downloads Documentation on how to do Cursor Addressing and other features.

Windows built-in Telnet

  1. To get Telnet running on Windows, please Google it.
  2. Once you fire it up, it creates a cmd window and gives a ‘Telnet>‘ prompt.
  3. Stretch the window to full length.
  4. Typing ‘h’ will list out some help stuff.
  5. Typing ‘set ?‘ will show help for the set command.
  6. One option is ‘set term vt100′ — Type that.
  7. Another option is ‘open localhost <port>’. Type that with your port# (e,g, 1401).
  8. It should tell you its connected to NOVA.
  9. On the Telnet session, press ‘<esc>‘ and you are in!
  10. At the IRIS prompt, enter ‘PORT TYPE 8‘ to tell IRIS you are a VT100 (i.e. port type 8 is defined by $TERMVT100).

Several notes:

  • Typing ‘CTL+]‘ on Windows Telnet will drop the connection and revert to the Telnet prompt.
    Use ‘Q’ to quit the session.
  • You can make adjustments to the look of the Win Telnet window.
    Click on the icon in the upper left corner and check out properties.

Tera Term Pro

This is a free Telnet program. I like it better than the Windows Telnet because it has a lot more potential for fun. You can download it here:  http://ttssh2.osdn.jp/

Since a lot of Telnet clients (like this one) are distributed w/o any install program needed, my suggestion is to create sub-directories in /iris/ to handle them. Instructions that follow assume the directory /iris/teraterm/. Download the zip file there, unzip it, and if necessary move the files up one level and get rid of the distribution folder.

Locate /iris/teraterm/ttermpro.exe. Right-click and create a shortcut. Move the shortcut to your desktop for easy access. Edit /iris/teraterm/teraterm.ini, and be sure the ‘Language’ is set to ‘English’. Also feel free to set defaults for TermType, TCPPort, etc.

  1. Run Tera Term ( the executable noted above).
  2. It should produce both a cmd window and a dialog box.
  3. For Host: enter LOCALHOST
  4. For Service select “Telnet”
  5. For Port, enter whatever you told SimH (e.g. 1401).
  6. Click OK. It should connect. Stretch the window to full length.
  7. Play around with various settings to get it to look the way you like.

Setup >> Font  (for a good sample, run a #LIBR after each setting).
I like:  Terminal 9  //   Orator 11 // Courier New 10

Setup >> Window  (I prefer Horizontal line for cursor)

Dave’s Telnet

This is one of the best I’ve seen. Fairly intuitive and runs many emulations including VT320 which does various colors ( Google VT320 escape codes for info ).

Available here: https://sourceforge.net/projects/dtelnet/
( I have seen other download sites, but at least one had an unworkable program ).


Please let me know if you have another Telnet client you like. I know PuTTY is one of the most popular, but I have not had any luck with it at all.

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