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Dave Liddle is a legend in Silicon Valley but what many don't know is he had an interesting role with Owens-Illinois in the late 60s, working on the plasma display, in cooperation with the PLATO plasma panel team at the University of Illinois.

Here's a recent oral history conducted at the Computer History Museum of Dave talking about his long illustrious career. The plasma project starts around the 17 minute mark, but the video below is set to around 15 minutes so you can get a little context of what led to his choice of going to Owens-Illinois. Better yet, start at the beginning of the interview and watch the whole 2.5 hour extravaganza!

Dr. Larry Weber, who worked on the PLATO plasma panel project at CERL back in the day, and who participated in the hardware session at the PLATO @ 50 conference (watch the video here), was one of thirteen individuals inducted into the Consumer Electronics Association's CE Hall of Fame 2010 class. Dr. Bitzer and Dr. Slottow, co-inventors of the plasma panel display, were already inducted into the CE Hall of Fame in 2006.

Congrats Larry!

For more on the story, here's a link to the CEA's own blog post.

The PLATO@50 conference panel on Hardware Innovations featured Dr. Donald Bitzer, Dr. Roger Johnson, and Dr. Larry Weber. The Moderator was Philip McKinney. It's about 86 minutes long.

Thanks to Aaron Woolfson's dedication, incredible effort, and dogged determination, attendees of the free PLATO @ 50 conference on June 2-3 will have hands-on access to fully-restored and operational PLATO terminals. They just arrived yesterday!

PLATO terminals arrive at CHM

One neat little detail about these terminals is they all have one little enhancement that didn't exist when they were originally manufactured: Aaron has added an Ethernet port to each. So they can simply be plugged into the Internet and connect to and you instantly see "Press NEXT to begin" on the screen. Amazing.

PLATO V terminal

These terminals arrived at the Computer History Museum yesterday, artifact donations and hopefully in time part of its permanent exhibit. For me, the arrival of these terminals marks a huge milestone for the Museum, as I've been gently pushing the Museum for years to embrace the significance and historical importance of PLATO and one major way I've always hoped that would come about was for the Museum to accept PLATO artifacts into their collection. And we've reached that day. (I love the fact that these terminals are in crates that say "Property of The Computer History Museum".) Another massive milestone of course is the conference itself: it's just enormously exciting that the Museum has further embraced PLATO by supporting and co-producing the upcoming two-day conference. Hope to see you at the conference!

The event's one PLATO history session, featuring Don Bitzer, Lippold Haken, and Peter Braunfeld, starts around then. The embedded video window below should activate around 8:45am Central Time on Thurs, April 15, 2010:

For more info on the conference please see

UPDATE 6/24/2010 --- I've updated the video to be the archived video since this is no longer streaming live obviously :-)

Aaron Woolfson is making great progress with the restoration of PLATO terminals for the conference. He posted some photos yesterday:

Aaron's PLATO Terminal Restorations

At the left is a PLATO IV terminal. Center is a PLATO V terminal. At right is a restored Control Data IST-II terminal. (Click on the links to go directly to Aaron's actual images.) With luck we'll have five, six, maybe seven restored terminals working at the PLATO @ 50 conference on June 2-3. Hope to see you there!

UIUC ECE396 PLATO IV Terminal Restoration Project Today I received an email from Donald Ziems, a student of Professor Lippold Haken. Turns out Haken's ECE 395 class at the University of Illinois Urbana-Champaign has a team of students restoring an ancient PLATO IV terminal as a class project (cool!). Donald pointed me to the class wiki where they're tracking the progress of the project, including a bunch of photos and a PDF of the "PLATO IV Operation Manual".

Aaron Woolfson has for the past five years undertaken an amazing project: to acquire and restore -- not just clean up, but restore to original factory specifications -- a variety of original PLATO terminals from the 1970s. He's traveled all over the country, picked up parts here and there, and has even had custom parts made.

On January 20, I finally got to meet Aaron. We converged on the Computer History Museum so the museum folks could see a real working PLATO V terminal. The plan is to have, on hand at the conference about half-a-dozen PLATO terminals up and running and connected to the service. Attendees will be able to try out the terminals and check out original PLATO applications including thousands of educational lessons ranging from anthropology to zoology, as well as the notesfiles, TERM-talk, and of course, PLATO's legendary multiplayer games.

Here are some photos of the terminal Aaron showed off at the museum:

PLATO V terminal restoration

What's especially cool is that Aaron has hacked together an interface such that the terminal thinks it's connected to a 1260-bps serial line, but in fact, is connected to the Internet which it then converts into the old 1260-bps serial signal. For the conference, he's building little interface boxes for each terminal such that all you have to do is plug the terminal into an ethernet cable connected to the service on the Internet and you're all done.

Recently I received an email from David Dennis, a former PLATO user from Illinois who over the years has shared with me numerous anecdotes. This one was one I'd not heard before, where he describes what he believes might have been the first instance of a "denial of service" (DoS) attack on a computer network.

If there is one thing I've learned over the years, never make an absolute claim of "first" when it comes to anything computer-related, because as soon as you do, someone somewhere will come out of the woodwork with proof of an even-earlier first. So, I eagerly await the onslaught of "no way, I saw a DOS attack years earlier!" comments. But in the meantime, here's a neat story from 1974.

Some quick explanation of terms before I quote the email. First, he's recalling an incident that took place at CERL, the Computer-based Education Research Laboratory, at the University of Illinois Urbana-Champaign. "TUTOR" is the name of the programming language on PLATO. "Author mode" refers to a level of system privileges on PLATO that all authors/developers had. "Went back over to uni" means he went back over to University High School, located across the street from CERL. (Old joke: Why did the Uni High student cross the road? To get to CERL.)

Okay, here goes. From David Dennis:

As far as I know, I'm the first person to have created a DoS of a room full of PLATO terminals deliberately. Systems people could of course kick anyone out they wanted, and "operator wars" had existed for years, but those tended to be consensual attacks on each other. What I did was I heard about a new command called the "external" command in TUTOR, or 'ext'. Specifically, one of the music kids was saying how if you didn't have a device attached, an ext command would cause your terminal to lock up and have to be powered off. Remember that powering off was discouraged, due to always-concern over flaky power to the plasma panels.

The other piece of this was they had rolled out the external command for everyone in the fall of 1974, after it having been only in use by the Music project. This meant that every user account on PLATO was set to defalt "can accept ext commands." Default on.

If you recognize default enabled from any firewall work you'll immediately recognize the trouble...

Anyway, I heard this and immediately thought of how a room full of annoying users could be locked up at once. My little 13 year old brain wanted to see a room full of users all be locked up at once.

So, I wrote a little program that sent exts to everyone within a range of site numbers, waited til I was over at CERL one morning, and let er rip.

It worked as advertised, 31 users all had to power off at once, great mayhem in the classroom, site monitors notified. No logging of course, I was never detected. Quietly left the room, went back over to uni.

Accessed the site displays I knew of from author mode, and looked up other sites around town or the country, and tried sending them some ext's too. Was delighted to see mass posting on notesfiles about a locking out they were experiencing.

Soon some systems guys figured it out, probably a combination of common sense and maybe looking in some sort of logs, though I was never prosecuted or even approached, so I have to think to this day it was undetected. A few weeks later the ext command was withdrawn from 'open all' and a while after that was redeployed, this time with the default set to OFF. As it should have been all along. :)

So was there ever a DoS on a networked system prior to 1974 ? Im sure there had to be, but at least for the moment I'm claiming it !

This is a classic example of how things typically go with software, only this is an example from 1974: release a system to the users, and they will find bugs and vulnerabilities the developers weren't aware of or assumed were harmless. Make changes, release a revised system, and so on. Over time, this is how the PLATO system became more robust and secure.

UPDATE 2/14/2010 -- Welcome, slashdot. Er, one moment while I put out the fire that you're causing with my web server. :-) Let me provide a little more detail on the TUTOR -ext- command, how it worked, etc. Here is the actual page from PLATO's online help system for the -ext- command:

ext command documentation

The -ext- command was relatively new in 1974, indeed, it may have been brand-new. It was intended so that you could have your PLATO IV terminal connected to an external peripheral device and control that device using a serial connection. Note how the manual says "only 1 -ext- per second may be sent to another station." Heh, in those days, one per second might be enough!

UPDATE #2 - 2/14/2010 Below is the note on =announce=, the System Announcements notesfile, from 1/2/74, announcing that a change had ben made to the -ext- command (perhaps, not sure, due to the exploit above):

-ext-         Note 1

1/2/74         12:32 am CST         andersen / s

The two argument -ext- command (ext data,station) now checks if the other station wishes to recieve -ext- commands... as with the talk option an author may specify that he wishes to recieve -ext-'s from anyone, from his course only, or not at all..

The -ext- command returns the system variable *error* = -1 if the data was sent or = 0 if not

The one-argument -ext- command is not affected


Learn more about the book:

The Friendly Orange Glow: The Story of the PLATO System and the Dawn of Cyberculture, by Brian Dear

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