6 ms·

A History of the TTY

192 points by LorenDB 3y ago

russellbeattie 3y ago
Just for fun, here's the famous pic of Gates and Allen using what looks like a Teletype Model 33 [1], and of course Ritchie and Thompson in front of a PDP-11 [2]. For years (decades!) I never understood the purpose of line editors and why VI was such an improvement. Until one day I saw the pic of Gates and Allen and suddenly realized why, and how it worked. You already had a printout of your code (or text) in front of you. If you wanted to edit the text, you used a line editor to rewrite the line it was on. After a while you could print the whole thing again if you needed. And this is why my TRS-80's BASIC editor worked the same way. It was just like the original time-share version from Dartmouth ported to a microcomputer. 1. https://www.charterworld.com/news/wp-content/uploads/2018/10/Paul-Allen-with-Bill-Gates-in-front-of-a-teletype-machine-at-the-Lakeside-School-in-1970.-Courtesy-Lakeside-School.jpg https://www.charterworld.com/news/wp-content/uploads/2018/10... 2. http://www.columbia.edu/cu/computinghistory/teletype/ken-and-den.html http://www.columbia.edu/cu/computinghistory/teletype/ken-and...
- daveevad 3y ago
  That's the first time seeing that Gates photo for me. He would've been 14 or 15 years old.
  - russellbeattie 3y ago
    Gates actually wrote about the photo in a blog post he wrote after Allen passed away. [1] > The first time I saw how passionate Paul could get about something, I was in 8th grade. This picture might make you think he was my teacher, but he was actually a sophomore, just a little less than three years older than me. > This teletype is the thing that brought us together. Our school, Lakeside, held a rummage sale and used the proceeds to buy a teletype terminal. We were obsessed with it. The problem was, it was really expensive to use – 40 dollars an hour! The only way for us to get computer time was by exploiting a bug in the system. 1. https://www.gatesnotes.com/Forbes-Philanthropy-Summit-honors-Paul-Allen https://www.gatesnotes.com/Forbes-Philanthropy-Summit-honors...
- eru 3y ago
  > If you wanted to edit the text, you used a line editor to rewrite the line it was on. After a while you could print the whole thing again if you needed. That's probably also part of why when you used line numbers in early BASIC, you left plenty of numerical gaps, so you didn't have to re-print as often.
  - gattilorenz 3y ago
    I assume it’s also because reusing a line number means losing whatever code was previously there, and if you find a bug and need to add extra code you don’t want to rewrite part of what is correct just to add a few instructions in between, whether on a teletype or on a terminal with a screen.
    - kryptiskt 3y ago
      It wasn't that bad, you could renumber programs with a single command if you got stuck with no room to insert a line.
      - thristian 3y ago
        The BASIC I grew up with (Applesoft Basic) didn't have a built-in command to renumber a program, but it did have a helper tool you could run from disk. Unfortunately, it only updated the number of each line - it didn't update the line number references in commands like GOTO or GOSUB, so it was pretty much useless for any program large enough that you might want to automate renumbering.
- zokier 3y ago
  On line-editors, it is bit funny that even the most hard-core cli enthusiastics draw the line there and use some sort of visual editor despite line editors being more pure cli thing. Has anyone seen anyone do any non-trivial coding or other work with line-editors? I imagine that the code editing experience for blind people might be somewhat comparable to using line-editors? Although especially with hard copy terminals you don't need to keep everything in your head
  - varjag 3y ago
    If you programmed BASIC (or for that matter other languages) on micros in 1980s, line editors were prevalent.
    - quickthrower2 3y ago
      The bbcbasic list, ren, auto commands and copy key were very beginner friendly line editors. Super easy to grok.
  - anthk 3y ago
    Unix and ed for sure, before they wrote ex and vi.
  - mastax 3y ago
    I remember a post on here a while ago arguing for using ed. I think it was mostly about scripting contexts and batch processing, not interactive editing.
    - rwmj 3y ago
      I use 'sed' most days.
  - xorcist 3y ago
    I doubt many "hard-core cli enthusiasts" desire some sort of digital self flagellation, but instead strive for efficiency. Full screen editors are efficient, and was very quickly adopted when made available. Line editors prevailed for a long time, not because of user preferences but because they were tiny and was shipped by default. In PC-DOS/MS-DOS edlin.com/exe was what was available until the full screen editor edit.exe shipped some years into the 90s. Almost all home computers came with a variant of BASIC in ROM, which also used line editing (not even with a proper editor but by substitution of whole lines).
- iiooiiooikk 3y ago
  Note to anyone with HTTPS-only mode enabled in their browser: that second link won't work because it's only served over HTTP and not the HTTPS link it is replaced by. Here's an archive link instead: https://web.archive.org/web/20240226112837/http://www.columbia.edu/cu/computinghistory/teletype/ken-and-den.html https://web.archive.org/web/20240226112837/http://www.columb...
westurner 3y ago
https://en.wikipedia.org/wiki/TTY https://en.wikipedia.org/wiki/TTY disambiguates to Teleprinter, TDD, and Computer_terminal; but not Terminal_emulator, Virtual_terminal (VT), Pseudoterminal (PTY), or this article
- deleted 3y ago
  [deleted]
- bheadmaster 3y ago
  It does disambiguate to Virtual console, which arguably encompasses all three of those.
  - westurner 3y ago
    Good catch on the anchor text there. Trying to decide whether to add VT and PTY (and maybe RTTY) to the disambiguation page or just comment here
wenyuanyu 3y ago
The user interface of the current ChatGPT strikingly reminds me of the classic teleprinter interface. It's fascinating to think that, with a bit of ingenuity, one could potentially retrofit a 1960s teleprinter to interface with the ChatGPT API. This thought leads me to ponder whether there are ongoing projects aimed at evolving this user interface into something more dynamic and interactive with LLMs. Specifically, I'm curious about initiatives that not only automatically better visualize results beyond Markdown but also "generates" innovative UI components and layouts. These would ideally support richer user interactions, such as touch, clicks, scrolling, and zooming for the input requests. Enhancing the interface in such a manner could revolutionize the way we interact with AI, making it more intuitive and engaging.
- flir 3y ago
  Hmmmm. Anyone know what terminals were used in Colossus: The Forbin Project? You know. For verisimilitude.
  - teddyh 3y ago
    As I recall, that movie used exclusively CRT:s and running light displays. Teletypes were used in the background, but their output was never shown.
    - Animats 3y ago
      No Teletypes. The input device in the movie was an ordinary IBM Selectric typewriter. Not even one with a computer interface. That movie is worth watching today. It's the Singularity, happening.
  - euroderf 3y ago
    For verisimilitude there should be the big pixellated signboard up on a pedestal in the middle of the room, with the giant messages crawling across, and the clackety-clack that the film soundtrack played when the messages crawled. Messages like "I'm sorry, Dave. I can't recall the ICBMs. Maybe you would like to play today's Wordle?"
- 3y ago
ggm 3y ago
If you watch enough B&W films, you can see Baudot code passing by. It's often the visual metaphor of the 40s and 50s for "we are very high tech" -A dead give-away is the low hole count across the tape. 5 holes, not 7+1 (parity)
- Animats 3y ago
  One of the best examples of Teletypes and paper tape: "The House on 92nd Street".[1] They show a typing reperforator (not clear which model; it's not a Model 14) hammering out TAKE INTO CUSTODY IMMEDIATELY ALL JAPANESE CLASSIFIED AS DANGEROUS HOOVER <= ARREST ALL GERMAN NATIONALS KNOWN TO BE SUBERSIVE HOOVER <= The movie was made with the full approval of J. Edgar Hoover. (I used to restore old Teletype machines and had a working telegraph office at about ten steampunk conventions.) [1] https://youtu.be/Z-BwyzbF7E4?t=2192 https://youtu.be/Z-BwyzbF7E4?t=2192
  - ggm 3y ago
    Another one to one side, is a hollerith card sorting machine in the original Michael Caine film of "The Ipcress File" -Len Deighton used to refer to tech in the books, and wound up being gifted one of the first word processing systems by a contact somewhere like IBM, to write on: industry noticed he liked the tech. Nicholas Freeling did the same with CERN/DESY type places and the CAMAC crate in his book "Gadget" -he asked people what you call the kind(s) of tech they used, and they gave him something to use. Could have been "Unibus" and "pdp11"
cjs_ac 3y ago
> I will omit the many interesting details of the Linux terminal infrastructure here, as it could easily fill its own article. Linus Akesson has written that article here: http://www.linusakesson.net/programming/tty/index.php http://www.linusakesson.net/programming/tty/index.php
- teddyh 3y ago
  *Åkesson
- deleted 3y ago
  [deleted]
namaria 3y ago
Very interesting read, but the author has some peculiar notions about history. Why would is it intriguing that early experimentation with electricity would use clumsy measuring methods, or that the transcontinental telegraph preceded transcontinental telephone in the US by 50 years? It all sounds perfectly logical to me.
seoulbigchris 3y ago
Back in the early 80s, on an TTY connected to the campus CDC mainframe, I learned the hard way that the editor command "222d" does not delete line 222. Rather, it deletes the next 222 lines in the file!
mark-r 3y ago
It's a little off-putting that he says punched paper tape was used in the early days of computing. Mostly it was punched paper cards, a different thing entirely.
- HarHarVeryFunny 3y ago
  Well, there were both. Punched cards were used in computing centers for preparing batch mainframe jobs for submission. Punched tape was more a hobbyist thing, as form of program storage and sharing, used in the era of early machines such as the Altair 8800. You can still buy a copy of Microsoft BASIC on punched tape if you need it! https://www.ebay.com/itm/196212300301 https://www.ebay.com/itm/196212300301
  - mbreese 3y ago
    To add to your comment… I thought the use of paper tape was directly related to the teletypes (when used for I/O with a computer). Where the paper tape could operate as both an input and output mechanism, depending on if you wanted to input a program/text or save a program/text. Paper tape wasn’t a computer storage medium, as much as it was a teletype medium. In this way, the paper tape hijacked the interactive I/O mode on these early computers to supplant it with a stored format.
    - nomadluap 3y ago
      I guess you could look at paper tape as a physical manifestation of redirecting terminal I/O to text files using > and < in the shell.
    - HarHarVeryFunny 3y ago
      Interesting - I wasn't aware of that. When I first learnt to program (in PL/1) in the 70's it was on a punched card system, but I never used paper tape myself. So, was switching from keyboard to tape input, or from printer to tape output, done locally at the teletype, or could that be controlled by the computer it was attached to ? I guess this implies the paper tape format was basically just a dump/listing of sorts that might otherwise have been directed to the printer, and when used as an input this would then be read into a program (e.g. editor) that was really expecting keyboard (tty) input ?
HarHarVeryFunny 3y ago
I got my first home computer in 1978 (a NASCOM-1 Z80 kit) and remember that used Teletypes (basically a printer with a keyboard) were still available back then, and more affordable than video terminals such as the VT52. The famous VT100 terminal only came out in 1978 and cost $1500 or so, so wasn't the sort of thing you would use with a $200 home computer. https://en.wikipedia.org/wiki/Teletype_Model_33 https://en.wikipedia.org/wiki/Teletype_Model_33 I was recently thinking of playing with a VT102/220 emulator on a Raspberry Pi as an external 120 col display for a BBC micro. Cheap to do today, but not exactly retro-computing since it would have been prohibitive back in the day.
dboreham 3y ago
Decent article. I owned a 5-channel teleprinter for a while in my youth (they were junk at the time, while a real ASR-33 would be worth something). I had to generate baudot code by bit-banging an I/O pin in software because the UARTs even then didn't support 5-bit characters. It smelled of oil. No electronics, only lots of mechanical gubbins and a couple of electromagnets. The key point of the article is that teleprinters pre-date computers by decades; when people built the first computers they stole a teleprinter from down the hall to interact with it; then teleprinters further evolved to meet the computer use-case (transition from baudot to ASCII).
EvanAnderson 3y ago
I happened to notice a couple of eBay listings for Teletype Corporation machines on eBay over the weekend. Odd that this comes up today... https://www.ebay.com/itm/226019318024 https://www.ebay.com/itm/226019318024 https://www.ebay.com/itm/226019320272 https://www.ebay.com/itm/226019320272
sillywalk 3y ago
Interesting. I'll also add "The TTY De-Mystified"[0] as another good article, with some diagrams as well. [0] http://www.linusakesson.net/programming/tty/ http://www.linusakesson.net/programming/tty/
ranger207 3y ago
While reading this article I looked around for some more information on the model 15 teletype he mentioned, and I found this great playlist about how they work, including using it with an Altair 8800 running CP/M and BASIC https://www.youtube.com/playlist?list=PLB3mwSROoJ4JoPgcLzZ3kMKmQI5eN-4No https://www.youtube.com/playlist?list=PLB3mwSROoJ4JoPgcLzZ3k...

192 points by LorenDB 3y ago

Just for fun, here's the famous pic of Gates and Allen using what looks like a Teletype Model 33 [1], and of course Ritchie and Thompson in front of a PDP-11 [2]. For years (decades!) I never understood the purpose of line editors and why VI was such an improvement. Until one day I saw the pic of Gates and Allen and suddenly realized why, and how it worked. You already had a printout of your code (or text) in front of you. If you wanted to edit the text, you used a line editor to rewrite the line it was on. After a while you could print the whole thing again if you needed. And this is why my TRS-80's BASIC editor worked the same way. It was just like the original time-share version from Dartmouth ported to a microcomputer. 1. https://www.charterworld.com/news/wp-content/uploads/2018/10/Paul-Allen-with-Bill-Gates-in-front-of-a-teletype-machine-at-the-Lakeside-School-in-1970.-Courtesy-Lakeside-School.jpg https://www.charterworld.com/news/wp-content/uploads/2018/10... 2. http://www.columbia.edu/cu/computinghistory/teletype/ken-and-den.html http://www.columbia.edu/cu/computinghistory/teletype/ken-and...

daveevad 3y ago
That's the first time seeing that Gates photo for me. He would've been 14 or 15 years old.
- russellbeattie 3y ago
  Gates actually wrote about the photo in a blog post he wrote after Allen passed away. [1] > The first time I saw how passionate Paul could get about something, I was in 8th grade. This picture might make you think he was my teacher, but he was actually a sophomore, just a little less than three years older than me. > This teletype is the thing that brought us together. Our school, Lakeside, held a rummage sale and used the proceeds to buy a teletype terminal. We were obsessed with it. The problem was, it was really expensive to use – 40 dollars an hour! The only way for us to get computer time was by exploiting a bug in the system. 1. https://www.gatesnotes.com/Forbes-Philanthropy-Summit-honors-Paul-Allen https://www.gatesnotes.com/Forbes-Philanthropy-Summit-honors...
eru 3y ago
> If you wanted to edit the text, you used a line editor to rewrite the line it was on. After a while you could print the whole thing again if you needed. That's probably also part of why when you used line numbers in early BASIC, you left plenty of numerical gaps, so you didn't have to re-print as often.
- gattilorenz 3y ago
  I assume it’s also because reusing a line number means losing whatever code was previously there, and if you find a bug and need to add extra code you don’t want to rewrite part of what is correct just to add a few instructions in between, whether on a teletype or on a terminal with a screen.
  - kryptiskt 3y ago
    It wasn't that bad, you could renumber programs with a single command if you got stuck with no room to insert a line.
    - thristian 3y ago
      The BASIC I grew up with (Applesoft Basic) didn't have a built-in command to renumber a program, but it did have a helper tool you could run from disk. Unfortunately, it only updated the number of each line - it didn't update the line number references in commands like GOTO or GOSUB, so it was pretty much useless for any program large enough that you might want to automate renumbering.
zokier 3y ago
On line-editors, it is bit funny that even the most hard-core cli enthusiastics draw the line there and use some sort of visual editor despite line editors being more pure cli thing. Has anyone seen anyone do any non-trivial coding or other work with line-editors? I imagine that the code editing experience for blind people might be somewhat comparable to using line-editors? Although especially with hard copy terminals you don't need to keep everything in your head
- varjag 3y ago
  If you programmed BASIC (or for that matter other languages) on micros in 1980s, line editors were prevalent.
  - quickthrower2 3y ago
    The bbcbasic list, ren, auto commands and copy key were very beginner friendly line editors. Super easy to grok.
- anthk 3y ago
  Unix and ed for sure, before they wrote ex and vi.
- mastax 3y ago
  I remember a post on here a while ago arguing for using ed. I think it was mostly about scripting contexts and batch processing, not interactive editing.
  - rwmj 3y ago
    I use 'sed' most days.
- xorcist 3y ago
  I doubt many "hard-core cli enthusiasts" desire some sort of digital self flagellation, but instead strive for efficiency. Full screen editors are efficient, and was very quickly adopted when made available. Line editors prevailed for a long time, not because of user preferences but because they were tiny and was shipped by default. In PC-DOS/MS-DOS edlin.com/exe was what was available until the full screen editor edit.exe shipped some years into the 90s. Almost all home computers came with a variant of BASIC in ROM, which also used line editing (not even with a proper editor but by substitution of whole lines).
iiooiiooikk 3y ago
Note to anyone with HTTPS-only mode enabled in their browser: that second link won't work because it's only served over HTTP and not the HTTPS link it is replaced by. Here's an archive link instead: https://web.archive.org/web/20240226112837/http://www.columbia.edu/cu/computinghistory/teletype/ken-and-den.html https://web.archive.org/web/20240226112837/http://www.columb...

westurner 3y ago

https://en.wikipedia.org/wiki/TTY https://en.wikipedia.org/wiki/TTY disambiguates to Teleprinter, TDD, and Computer_terminal; but not Terminal_emulator, Virtual_terminal (VT), Pseudoterminal (PTY), or this article

deleted 3y ago
[deleted]
bheadmaster 3y ago
It does disambiguate to Virtual console, which arguably encompasses all three of those.
- westurner 3y ago
  Good catch on the anchor text there. Trying to decide whether to add VT and PTY (and maybe RTTY) to the disambiguation page or just comment here

wenyuanyu 3y ago

The user interface of the current ChatGPT strikingly reminds me of the classic teleprinter interface. It's fascinating to think that, with a bit of ingenuity, one could potentially retrofit a 1960s teleprinter to interface with the ChatGPT API. This thought leads me to ponder whether there are ongoing projects aimed at evolving this user interface into something more dynamic and interactive with LLMs. Specifically, I'm curious about initiatives that not only automatically better visualize results beyond Markdown but also "generates" innovative UI components and layouts. These would ideally support richer user interactions, such as touch, clicks, scrolling, and zooming for the input requests. Enhancing the interface in such a manner could revolutionize the way we interact with AI, making it more intuitive and engaging.

flir 3y ago
Hmmmm. Anyone know what terminals were used in Colossus: The Forbin Project? You know. For verisimilitude.
- teddyh 3y ago
  As I recall, that movie used exclusively CRT:s and running light displays. Teletypes were used in the background, but their output was never shown.
  - Animats 3y ago
    No Teletypes. The input device in the movie was an ordinary IBM Selectric typewriter. Not even one with a computer interface. That movie is worth watching today. It's the Singularity, happening.
- euroderf 3y ago
  For verisimilitude there should be the big pixellated signboard up on a pedestal in the middle of the room, with the giant messages crawling across, and the clackety-clack that the film soundtrack played when the messages crawled. Messages like "I'm sorry, Dave. I can't recall the ICBMs. Maybe you would like to play today's Wordle?"
3y ago

ggm 3y ago

If you watch enough B&W films, you can see Baudot code passing by. It's often the visual metaphor of the 40s and 50s for "we are very high tech" -A dead give-away is the low hole count across the tape. 5 holes, not 7+1 (parity)

Animats 3y ago
One of the best examples of Teletypes and paper tape: "The House on 92nd Street".[1] They show a typing reperforator (not clear which model; it's not a Model 14) hammering out TAKE INTO CUSTODY IMMEDIATELY ALL JAPANESE CLASSIFIED AS DANGEROUS HOOVER <= ARREST ALL GERMAN NATIONALS KNOWN TO BE SUBERSIVE HOOVER <= The movie was made with the full approval of J. Edgar Hoover. (I used to restore old Teletype machines and had a working telegraph office at about ten steampunk conventions.) [1] https://youtu.be/Z-BwyzbF7E4?t=2192 https://youtu.be/Z-BwyzbF7E4?t=2192
- ggm 3y ago
  Another one to one side, is a hollerith card sorting machine in the original Michael Caine film of "The Ipcress File" -Len Deighton used to refer to tech in the books, and wound up being gifted one of the first word processing systems by a contact somewhere like IBM, to write on: industry noticed he liked the tech. Nicholas Freeling did the same with CERN/DESY type places and the CAMAC crate in his book "Gadget" -he asked people what you call the kind(s) of tech they used, and they gave him something to use. Could have been "Unibus" and "pdp11"

cjs_ac 3y ago

> I will omit the many interesting details of the Linux terminal infrastructure here, as it could easily fill its own article. Linus Akesson has written that article here: http://www.linusakesson.net/programming/tty/index.php http://www.linusakesson.net/programming/tty/index.php

teddyh 3y ago
*Åkesson
deleted 3y ago
[deleted]

namaria 3y ago

Very interesting read, but the author has some peculiar notions about history. Why would is it intriguing that early experimentation with electricity would use clumsy measuring methods, or that the transcontinental telegraph preceded transcontinental telephone in the US by 50 years? It all sounds perfectly logical to me.

seoulbigchris 3y ago

Back in the early 80s, on an TTY connected to the campus CDC mainframe, I learned the hard way that the editor command "222d" does not delete line 222. Rather, it deletes the next 222 lines in the file!

mark-r 3y ago

It's a little off-putting that he says punched paper tape was used in the early days of computing. Mostly it was punched paper cards, a different thing entirely.

HarHarVeryFunny 3y ago
Well, there were both. Punched cards were used in computing centers for preparing batch mainframe jobs for submission. Punched tape was more a hobbyist thing, as form of program storage and sharing, used in the era of early machines such as the Altair 8800. You can still buy a copy of Microsoft BASIC on punched tape if you need it! https://www.ebay.com/itm/196212300301 https://www.ebay.com/itm/196212300301
- mbreese 3y ago
  To add to your comment… I thought the use of paper tape was directly related to the teletypes (when used for I/O with a computer). Where the paper tape could operate as both an input and output mechanism, depending on if you wanted to input a program/text or save a program/text. Paper tape wasn’t a computer storage medium, as much as it was a teletype medium. In this way, the paper tape hijacked the interactive I/O mode on these early computers to supplant it with a stored format.
  - nomadluap 3y ago
    I guess you could look at paper tape as a physical manifestation of redirecting terminal I/O to text files using > and < in the shell.
  - HarHarVeryFunny 3y ago
    Interesting - I wasn't aware of that. When I first learnt to program (in PL/1) in the 70's it was on a punched card system, but I never used paper tape myself. So, was switching from keyboard to tape input, or from printer to tape output, done locally at the teletype, or could that be controlled by the computer it was attached to ? I guess this implies the paper tape format was basically just a dump/listing of sorts that might otherwise have been directed to the printer, and when used as an input this would then be read into a program (e.g. editor) that was really expecting keyboard (tty) input ?

HarHarVeryFunny 3y ago

I got my first home computer in 1978 (a NASCOM-1 Z80 kit) and remember that used Teletypes (basically a printer with a keyboard) were still available back then, and more affordable than video terminals such as the VT52. The famous VT100 terminal only came out in 1978 and cost $1500 or so, so wasn't the sort of thing you would use with a $200 home computer. https://en.wikipedia.org/wiki/Teletype_Model_33 https://en.wikipedia.org/wiki/Teletype_Model_33 I was recently thinking of playing with a VT102/220 emulator on a Raspberry Pi as an external 120 col display for a BBC micro. Cheap to do today, but not exactly retro-computing since it would have been prohibitive back in the day.

dboreham 3y ago

Decent article. I owned a 5-channel teleprinter for a while in my youth (they were junk at the time, while a real ASR-33 would be worth something). I had to generate baudot code by bit-banging an I/O pin in software because the UARTs even then didn't support 5-bit characters. It smelled of oil. No electronics, only lots of mechanical gubbins and a couple of electromagnets. The key point of the article is that teleprinters pre-date computers by decades; when people built the first computers they stole a teleprinter from down the hall to interact with it; then teleprinters further evolved to meet the computer use-case (transition from baudot to ASCII).

EvanAnderson 3y ago

I happened to notice a couple of eBay listings for Teletype Corporation machines on eBay over the weekend. Odd that this comes up today... https://www.ebay.com/itm/226019318024 https://www.ebay.com/itm/226019318024 https://www.ebay.com/itm/226019320272 https://www.ebay.com/itm/226019320272

sillywalk 3y ago

Interesting. I'll also add "The TTY De-Mystified"[0] as another good article, with some diagrams as well. [0] http://www.linusakesson.net/programming/tty/ http://www.linusakesson.net/programming/tty/

ranger207 3y ago

While reading this article I looked around for some more information on the model 15 teletype he mentioned, and I found this great playlist about how they work, including using it with an Altair 8800 running CP/M and BASIC https://www.youtube.com/playlist?list=PLB3mwSROoJ4JoPgcLzZ3kMKmQI5eN-4No https://www.youtube.com/playlist?list=PLB3mwSROoJ4JoPgcLzZ3k...