Here is some interesting historical context on the TT2500 Logo Terminal (computer)
Seymour Papert: Yes, it does
Camera operator: Now I’m gonna zoom out, pan over. Okay. Focus on Marvin. Okay, focus on- And cut back the contrast. Well, we now should have… Marvin, can you look this way, please?
Seymour Papert: Okay, let
Camera operator: me try it.
Seymour Papert: Good.
Camera operator: We now have a small
Seymour Papert: picture. Exactly.
Camera operator: All right. Okay,
Seymour Papert: wait. You’re on
Marvin Minsky: Here is the 2500 machine displaying a number of moving spirals. These are very simple patterns, and we’re just showing a number of them to give you some idea of the kind of pictures that can be displayed on the screen at one time. This machine is called the 2500, and basically it’s a small, very powerful computer which has been built into it hardware to run two kinds of displays.
This is the central processor, which is the computer itself. This is a display which shows printed material, and it can use several kinds of fonts. In fact, you can design your own typeface. It can do a limited amount of picture-displaying ability. And this is called a vectorscope, which can show pictures made of lines and curves and points, and it can show pictures that move quite rapidly and, kind of animation that you can program The– I’ll say a few words about the computer.
Here’s a copy of the central processor unit It cost us about $2,000 to make this thing. It consists simply of a power supply to run the components and one large board that holds these integrated circuit components on it. It has about 250 chips, and you can see in sections, this section is the memory.
This is the computer itself. This processes the television display. This is the part that does arithmetic. And that’s all. A computer that can do those things can do more or less anything. Over here in the corner is the part that produces the vector display on that scope, and it’s capable of drawing line figures very rapidly.
You have to understand that this machine cannot make filled-in regions very well. It can fill in a few small regions, but basically it makes things out of line drawings, and that’s the reason for its speed and capability. So if you want shaded drawings, then
Camera operator: Yeah
Marvin Minsky: No, I’m off again
We developed this machine to make it possible to bring graphics to people who couldn’t afford a hundred thousand dollars or so for a graphics system. And in particular, we had in mind people in schools. The languages and computer facilities in schools really are very primitive. They’re they make the children learn to work with nineteen sixty-style equipment.
And one of the things that we discovered is that animation really turns kids on and lets them do serious projects instead of just toy problems and forms to fill out. So, one of the reasons why we think this machine makes animation practical for for people is that we’ve developed a language and a computer system to go with it that makes it easy for ordinary people who aren’t computer scientists or mathematicians or programmers to express themselves in moving graphic format.
We think the machine can be made to sell for five thousand dollars or less. The company right now consists of four or five people who are… have put together about twenty of these, and the cost of assembling and constructing each one is somewhere between two and three thousand dollars. The displays cost about three hundred dollars each, the board about a thousand, and so forth.
The components in mass production would presumably be quite a bit less, and the board quite a bit less and so forth. The machine is, can be loaded or any of the programs that you’ve developed can be stored on a simple audio cassette because the picture is not stored in video form. It’s stored in a form you’ll see shortly just as a list of where the lines and points and how fast they’re moving are.
And so, it’s not necessary to store the whole quarter million points that’s in a standard video picture on the tape. That way, we get an enormous amount of information for a very low cost, and that’s what makes having this sort of thing be usable in schools possible and presumably for lots of other applications where one isn’t using full video bandwidth.
Also, the pictures can be sent along ordinary telephone lines without any trouble because they appear on the telephone just in the same format as teletype characters. And you can get quite a lot of picture with quite a small number of words. ‘Cause when you describe a picture in words you really win on the communication bandwidth score.
Camera operator: Okay.
Marvin Minsky: Okay, so, I’d like to introduce Professor Seymour Papert of MIT who developed the programming language that we use for this kind of animation
Seymour Papert: That was Professor Marvin Minsky who designed and built this machine. I’m gonna show you how simple it is to write some very s- some pictures in the language that we’ve de- developed for children and other people. It might not be exactly the language that you would need, but it does show you how simple it is to make a computer draw a picture
Now to demonstrate our simple graphics language called Turtle Geometry. The reason for the name is that the language is based on an imaginary creature, which you’ll see on the screen in a moment, represented by a triangle. We can instruct the creature to move forward, and he’ll do that. Turn right, and he’ll do that.
Move forward again, and he’ll do that. And in this way, we can cause complicated figures to be drawn without having to worry about X and Y co- coordinates or other pseudo-mathematical complications. So let’s tell the turtle to go forward 100 units and see what he does
See, we get it by typing forward 100, and then when I press the Do It button, it’s going to do it The camera is ready
Marvin Minsky: Mm-hmm
Seymour Papert: I will press the do it button. Watch him. He went forward 100. Now if I say right 90, watch him change direction. If I say forward 100 again, he is going forward 100. Right 90 again, forward 100 again.
So I think go down forward 100 and right 90 and forward 100. Well-
Sorry
Are we still fil- filming? We’re still- Forward 100. There he went. Right 90. He’s turned again. Forward 100 should complete the square. Well, that’s a square. If I say clear screen, it’s gone. We can draw some more complicated things like I can draw a circle. So I’ve written a program to draw a circle. You see it draws it slowly like that.
I can draw it faster as well, but I’ll draw another circle, again, slowly so you can see what’s happening
show you something else. An interesting command is to tell it to spin. I’ll say spin 120, and now if you can see that turtle, you can see he’s turning. Now, while he’s turning, if I step forward 100, you’ll notice that any motion he’s given while he is, while he’s spinning, any instructions given inherits the turn.
So there he is going on that line set forward 100. Suppose I take him back home. I’m going to say home. Turtle goes back to the center if you notice. I’ll tell him to stop spinning Then maybe we’ll tell him to spin at a slower rate, maybe 10, and then go forward again a smaller amount and we could get something like a clock face.
Well, I gave him the wrong order. He’s spin- well, maybe that’s a better clock than a real one. We’ll rub it out and start again, and let’s see if we can fill in a circle around it. Let’s try that. There’s the minute hand, hour hand going the wrong way, and there’s the circle. Well, so there’s not much of a clock, but you get the idea of how easy it is to make things move and draw a picture
So maybe we’ll look at some of the more complicated things like those that you saw Marvin Minsky demonstrating at the very beginning of the, of this tape. Let’s do something just a little bit more complicated. What I’m gonna do, make it do now is draw forward, right, forward, right, 90, forward, right, 90, just like we did before.
Except you see it does forward, right, 90 except each time he’s taking a slightly bigger step. It’s making kind of a square spiral. It will go on for a while. We can stop at any time. Stop. So let’s play with that a little and make something similar to that except that this time we make it rotate. So tell it to go away.
Tell the turtle to spin maybe 30. And then I’ll tell it to draw one of those things again, go. But now this time because the table was spinning when it started drawing, it draws the thing in motion. And so notice the thing turning as it gets drawn, and it’ll go on turning as long as it exists. We can
gears and have it turning and goes on like that. We could send the turtle home, and then tell the thing to spin in the opposite direction and draw another round While spinning in the opposite direction, and now we’ve got the two superimposed spinning in opposite directions at somewhat different speeds So we can play various games with this one Without having to worry about any complicated mathematics and geometry.
If we were to stop there, it would have to go away. It’s gone. It’s back.
Camera operator: Oh, incidentally, I’m Russell Science. I’ve been operating this camera for the last, oh, few minutes or so. As I see Morris has been demonstrating too.
Seymour Papert: Okay, so he has another one here drawn
Today, you’ll see at a moment what the machine does if you ask it to put up even more line than it really can cope with in a straightforward way. See, up to now, we’ve got a perfectly stable picture, and it’s essentially putting up that picture as… It’s actually putting up a copy of the picture something like 60 times a second.
Now, watch what starts happening. It starts flickering.
Camera operator: Well, I’m the cameraman. I would admonish the audience not to despair, since the flicker emerges at roughly four times the frame rate required in video broadcast. 60 frames per second is the ordinary rate of display of this machine. It’s now trying to do roughly six times as much at 10 frames, and it’s flickering accordingly.
The line density, I’m told, is nominally capable of being run up to about 1,500 vectors of, Blades obviously we can’t see that bad on the screen. They overlap as you see now if they run off the edge. Now, this artifact is correctable in building the software
Seymour Papert: Is that artifact created by the software? Is there a limit to how much it can put out?
Camera operator: There certainly is.
Seymour Papert: Okay.
Camera operator: But that limit seems to me to be about three times video bandwidth. The machine ha-has better than the fifty nanosecond bit time and better than five megahertz bandwidth. So with a megahertz and a half in, in, in color transmission, there’s no problem in running a single channel of that information density on a broadcast quality tape.
Needless to say, this is not being taped on broadcast quality tape with an ordinary helical scan system. So, I suppose I should apologize in advance for any artifacts that may emerge from the untried interaction of this helical scan system and this parallel line raster display. This is a, I suppose you’d describe as a moderate precision display.
It’s a thousand
Seymour Papert: line- Oh, that’s a very s- very low persistence display. Yeah. A high persistence display- Well,
Camera operator: high precision, persistence is really low. It’s, it was a thousand lines too. And well, as I think we can go on to, to show you displays with higher apparent resolution and slower scan time are certainly possible.
And if one has ordinary studio equipment with variable frame rate and scan speed, a lot of these artifacts can be dispensed with in real time, and I have a book by Tribble
Seymour Papert: We’ll show you some other pictures.
Camera operator: Well, we have to Now, where she’s taking her pictures come from, This of course was just generated in real time by Professor Papert at the console here. One of the nicer properties of this machine, which I suppose the next thing we should demonstrate is that once you’ve done something once you can put it into memory of the processor and bring it back as multiple, and fill the screen with many replicas of the same thing, either in motion or at rest, either in, in regular arrays or pretty much at random or in any place you want.
So anything that you can do with vector addition, given the 1500 vectors, and given the bandwidth allowance we just described can be put up with fair resolution on display. The writing displays is something of a mystery to me, since most of the drawing I’ve seen done has been geometrical, and the system has not spent much time, to my knowledge, in the hands of people whose primary interest is sort of the graphic arts.
So given an artist of considerable skill and some patience I should hope that 1500 lines would add up to to aesthetically quite satisfactorily complex images instead of just
Geometrical figures and polygons, however elegant and psychedelic and interesting
Seymour Papert: Well, send me two
It would be very, would be interesting to have some people with, you know, dedication to graphic arts and knowing what they’re doing try and draw some interesting pictures. I don’t have any I can show you in that category. Perhaps I can show you some things that children have done.
Camera operator: Mm-hmm. And one hopes that the artist in question would not be deterred by language in a sense. It is literally a level of simplicity that allows it to be used