TI Logo: TI-99/4A Sprites and Graphics Done Right

TI Logo has a lot to offer, as a platform for creating graphics and games on the TI-99/4A. Its sprite handling especially is top notch, and lets you do things with TI-99 game graphics that Extended BASIC on its own simply can't.
After watching this, you may want to check out:
My Logo Compilation, including all demos mentioned in this video: pixelpedant.co...
TI Logo (1981) Manual: pixelpedant.co...
TI Logo II (1983) Manual: pixelpedant.co...
TI Logo Sampler Manual: pixelpedant.co...
#ti994a #retrocomputing

[@paulurbanus3598]

We (Jim Dramis) and I used TI Logo's live tile editor to create the wire-frame tumbling asteroids in Parsec. It was really cool to have a simple Logo procedure flip through the various tumble 'views' of the asteroids while live editing the definitions. This made refining the asteroids' animation shapes easy and fun.

[@PixelPedant]

That's amazing, to hear that's where those little asteroids came from. That asteroid sequence - combining sprite animation, action gameplay, speech synthesis, and PSG sound effects all at once - that was the single most remarkable TI-99 experience of a lot of childhoods, including my own. Seems like you and Jim immediately saw the value in that Logo sprite/tile editor that a lot of folks later on missed. If you ever have more recollections or ephemera to share from those days when Urbites and Dramites and Munch Men were first making their way on to the scene, by all means contact me at [e-mail] or on Twitter at twitter.com/PixelPedant/. All those bits of TI-99 history are a delight, and I delight in sharing and preserving them.

[@mikelunsford2587]

And a very awesome game

[@larryaugsburger8452]

Parsec was my favorite thing to do on my TI99, and what I missed most when I moved on to the Commodore 64. I refused to consider any computer that didn’t have sprites.

[@efhard]

Thanks so much for sharing this! I wrote this program at MIT a long time ago, developing TI Logo was my first programming job. Really takes me back.

[@PixelPedant]

That's awesome! Anything you can tell me about your experience of the project? Did TI provide any specific design requirements? And was it developed on a TI minicomputer, as TI's internal projects tended to be? I'd be delighted to hear anything you can tell me about its creation and your experience with it. Here, or at [e-mail]

[@efhard]

They didn't really except it had to work on the 99/4, the memory expansion was required of course. Originally it was a big flat black box that sat under the 99/4, bigger than the computer itself. The project was a joint effort with TI, MIT and the Lamplighter School in Dallas. The Logo interpreter itself was first written in Pascal by Gary Drescher. I was an undergrad at MIT when I started on it at the AI Lab Logo Group, later a staff employee. The first part of my job was to rewrite the Pascal interpreter in assembly language. Yes this was done on a TI-990 mini-computer which had the same instruction set, and well before we got an actual 99/4. Mark Gross wrote the turtle graphics, I wrote the sprite stuff and the shape and text editors you showed off.

[@efhard]

I'm glad you mentioned how the base machine had 256 whole bytes of RAM! (that's bytes kids, not MB or even KB). Even with the expansion we had to swap in and out chunks of the program (like the editors or the disk io routines) from the cartridge EPROM. I understand BASIC stored it's programs in the video memory (read/write was arduous), which left it even less graphics to work with.

[@efhard]

For anyone who's interested there's a paper "History of Logo" written by some of the pioneers of Logo in the Proceedings of the ACM History of Programming Languages conference for 2020. It's easy to find and PDF is downloadable.

[@eternalcheesecake]

@@efhard Please, I'd love for you to be interviewed on this rare development process.

[@Duewester]

Well, I hope you're happy. I just dumped about $75 (all included) on E-Bay for the Logo II package.🤠 One MORE thing on my ToDo list. I still haven't installed my FA18, and TiPi . Sometimes I wonder if regaining my youth is worth it. Yea, well I don' wonder about it very often and, when I do I come to the same conclusion - "of course it is!" Thank you so much for being out there and finding these things. Keep up the good work, be safe, live long and prosper, and all the other signoffs you can think of. 🙂

[@The_Wandering_Nerd]

Back when I was in high school, in the early 90s, I was given a TI-99/4A from a family friend with a whole bunch of games, programs, and manuals. One of them was TI LOGO. I had learned LOGO on the Apple II so it was relatively easy to figure out how to make graphics and sprites. I used it, and TI Extended BASIC, to create animations and titles for my high school's video productions class as well as family video Christmas cards. I wish I still had that stuff or had even kept the programs I wrote on it... so back up your floppies, kids, you'll never know when you'll be a nostalgic elderly person pining for the "good old days..."

[@richardtwyning]

Wow, it's over 30 years since I've seen those TI Logo sampler programs! 👍🏻

[@klf6992]

Never played with logo, but certainly will now! Thanks as always

[@PeBoVision]

"hopeless completionist" sounds so much nicer than "TI collection addict". And now I can say I am looking for a Video Vegas cart (The last of the released Funware carts that I'm missing) not because it's a good game, but because I am a "hopeless completionist". (Donations gladly accepted) And I already have both Logo carts (and Early Logo Learning Fun), because of course I do. Thanks Monsieur Pedant. Arguing with myself over wasting money on 4A-nostalgia is no longer an issue, because I am a hopeless completionist! There are no wastes of money where the 4A is concerned.

[@TGUlricksen]

Th Completionist still in TI=99a looking for that last gem. Thank you.

[@robertlock5501]

Nice video covering little tread ground. Really like the bitmap examples at 14:30 -- though the crescent moon facing the wrong way gave me a giggle. Thanks for sharing B)

[@ash-cn2oh]

PixelPedant's TI videos, soothing like Bob Ross!

[@CarbonicHolyPally]

Good review and some features I did not know about.

[@JSRFFD2]

One of my memories of TI Logo was getting the "OUT OF INK" error message, I think because my turtle graphics used up too many shape tiles. I never figured out how to keep that under control, or if I just wasn't using memory expansion properly.

[@efhard]

Nah, it was a limitation of the graphics hardware, see reply to howard oberg below

[@edorola]

Totally agree with your words! LOGO was my first programming language when I was 9 years old. I was so impressed with the SPRITES capability and mathart of the TI-LOGO!!!! Now I understand it better why. Impressive what Paul Urbanus and Efhard tell in their comments. Pure history! Already made me want to go back to coding in LOGO. :)

[@boblangill6209]

Another aspect of Logo programming was its text handling. In either 99'er or its follow up Home Computer Magazine there was an article on writing a text based adventure game in Logo. My 99 was just the base console, so running Logo wasn't an option.

[@arcadeshopper]

Thanks I never used LOGO bitd as it seemed like just a simple thing for little kids..

[@CompleteAnimation]

It warms my heart that there are still people finding joy from tinkering and learning about computers that were largely considered obsolete by the time I was born.

[@PeBoVision]

And you will likely find joy from the machines of your youth when you reach our age. Nostalgia is funny that way. You'll need a spare room, so plan for that.

[@rickibaron4816]

You always do an excellent job of showing off the TI. I may even try LOGO now myself. I was not aware of what LOGO was capable of until now.

[@rogerphillips642]

Thank you!! I have been waiting for this.

[@robrobbins]

My first computer was a TI-99/4A. For modern computer graphics fun I recommend the Processing program language. Although it is mostly used for abstract and geometric art, I am using it for retro isometric grid art.

[@victorsteerup4582]

Your cheerfulness and enthusiasm is infectious. Thanks for mentioning The Missing Link. How about a demo of the new G.E.M. (Graphics Environment Manager)? It has TML, and the split screen: top 2/3 graphics, bottom 1/3 text. Plus 40 / 80 column text.

[@PixelPedant]

Thanks! :) I actually did do a video on XB GEM: kzbin.info/www/bejne/eXzMnJ-boLiLhtU

[@rob_milstein]

Wow, very interesting. I only remember using Logo for the turtle.. and then getting bored. May I recommend a future video on TI art programs like Paint N Print, or something on either the Geneve , or the "IBM Connection" heavily promoted by Triton in the late 80s :)

[@PixelPedant]

TI Art programs (TI Artist is the one I've used the most myself). Are definitely one of those ideas I'm keeping in my back pocket. Good idea, for sure!

[@dotcomDan]

GRAPHX always my choice

[@scottcegielski8237]

Great channel! I had no idea Logo existed in TI-99. I had a TI-99 and did some minimal sprite coding but then had Logo on Coleco Adam and that was a whole new world of graphics and sound! Both had excellent manuals which a ten year old me could almost understand, lol.

[@G.B...]

I wouldn't believe there is a Logo version out there, on any platform, that lets you implement a... spreadsheet. And I would be wrong. 😆

[@PixelPedant]

Our dear TI-99/4A (and its software library) often does not a great deal of sense make. And in the end, we sort of like it that way. ;)

[@malcolmw513]

My remembrance of Logo was always that it was a better teaching language than BASIC, so schools wanted to use it. But unlike BASIC, which was built into nearly every microcomputer’s rom, you had to buy Logo. Consequently only fancy pants schools had it. So if you used Logo, it was a sign that you were posh and not to be trusted.

[@efhard]

The original TI-Logo work was a joint project between MIT, TI and the Lamplighter School in Dallas. We used to refer to it as a "school for overprivileged children". But I did also visit classrooms using TI-Logo in the New York City public schools

[@klf6992]

How about a step by step instruction on TIPI and Nano PEB? Such as loading files/programs to SD or flash Card, etc. But dumb it WAY down for folks like me!!

[@cbmeeks]

Excellent video. Will you be covering any Forth implementations on the TI?

[@PixelPedant]

That's probably along way off. Especially given my next major probable target is a big one: UCSD Pascal and the p-System. Which is not just a programming language, but an entire operating system.

[@cbmeeks]

@@PixelPedant Makes sense. Either way, looking forward. :-)

[@tron3entertainment]

Not sure which version Of LOGO I have, but "Out of Ink." was a really weird error message to me at the time.

[@briantw99]

Having started out on Atari LOGO, I think they could have done a better job with the line rendering algorithms - they definitely didn't use Bresenham, with all the odd sharp edges. And, "OUT OF INK?" Like, WTF. Redefining characters on the fly?They shoulda used full bitmap mode with the text on bottom-third of the screen. They could only do that if it didn't have to be compatible with the TI-99/4, of course, which didn't have bitmap mode. But I forgot how cool that frog animation was, thanks!

[@PixelPedant]

Yeah, TI Logo was initially developed for the 99/4, so there was never any hope of bitmap mode compatibility without a total ground-up rewrite subsequently. And while TI Logo II added some important stuff, it retained broad compatibility with TI Logo, and didn't seek to throw out what had come before and start over.

[@howardoberg5847]

the sprite handling is very impressive. kinda dumb it just used tile graphics. I 'guess' they did that so it could still be usable with the TI-99/4 (no A)?

[@PixelPedant]

Yeah, as far as I can tell, the first TI Logo was released just *before* the 4A hit the market in 81, so its design in whatever time prior would have been completely predicated on 99/4 capabilities. It also lacks a lower case. And Logo II just adds features. It doesn't break any major existing ones. So it's the same approach there.

[@efhard]

Yes, the 99/4 did not have the TMS9918A display chip so did not have Graphics Mode 2 and could not implement a bitmap that covered the entire screen. We originally implemented a smaller area for turtle graphics, but decided it would be better to let you draw over the entire screen and just "run out of ink" when there were no more tiles.

[@paulurbanus3598]

There was only one difference between the 9918 (no A) video chip in the 99/4 and the 9918A used in the 99/4A. The 9918A had a 2nd bitmap mode, Graphics Mode II. Both chips had the same sprite capability. I believe that the TI Logo uses the native sprite capability, which has dedicated hardware support for pixel-level positioning, as well as layering of sprites. Graphics Mode II was a simple modification, which had a different set of 8x8 tiles for the top, middle, and bottom part of the screen. Of course, this takes 3x amount of video tile memory The screen layout consisted of 32(H) x 24(V) 8x8 tiles, dividing the screen into thirds yields 32(H) x 8(V) = 256 tiles per third of screen. Each tile position was addressed by a byte (8 bit) value in the screen table, allowing selection of 1 of 256 tiles per screen third. In Graphics Mode II, the tile definitions were different for each third of the screen (while Graphics Mode I used the same tile definitions for the whole screen). Thus, Graphics Mode II allowed all points addressable graphics on the 99/4A. There was the limit of only two colors in each row of 8 pixels in a tile. The reason for the 'out of ink' errors in TI Logo was, as you pointed out, it was written for the 99/4 with only 256 unique tiles. TI Logo had to reserve some number (64?) of the 256 tiles for the character set used for program entry and display. The remaining 192-ish tiles were available for Turtle graphics, but there are 768 tile positions on the screen - only enough unique tiles for about 1/4 (192/768) of the screen. When turtle graphics were used, an 8x8 tile from the pool of 192 tiles was allocated when the first pixel was plotted. The same tile was used for any successive pixels that were in same 8x8 screen area. As soon as a new turtle pixel needed to be plotted in a different 8x8 tile position, a new tile from the available pool was allocated and placed (if an allocated tile wasn't already there). 'Out of ink' would occur when a pixel needed to be plotted in an 8x8 screen area where there was no allocated turtle tile, and there were no more turtle tiles to allocate.

[@jecelassumpcaojr890]

I had a 9918A chip that I was trying to use on a Z80 based computer I was building in 1982, but I couldn't get any information on this chip. In 1983 I started a design of a Logo computer with a friend, and being aware of the "out of ink" problem on the TI99/4 Logo decided to use the Motorola chipset (like in the TRS-80 Color Computer) which didn't have this limitation even though its choice of colors was unfortunate. Around that time I did receive the datasheet for the 9918A but didn't check it and so didn't notice the new mode. A combination of a 6809 processor with 9918A graphics would have been very interesting for Logo.

[@AllGamingStarred]

the TI-994/A is a great computer except for one tiny problem? Where the hell is the backspace key? Would it have killed them to add one?

[@PixelPedant]

The design of the 99/4 keyboard is basically a 4x10 layout (a la Spectrum). So the 99/4A still does suffer in a few places from an attempt at 100% compatibility with that (extremely miserly) approach to the keyboard, where there was room for nothing but the essentials. The 99/4A sorted out basically all of the 99/4s truly critical keyboard flaws though.

[@AllGamingStarred]

@@PixelPedant does LOGO have a sprite editor? I really don't understand TI's logic behind the char command. Commodore and even Sinclair use data statements.

[@PixelPedant]

@@AllGamingStarred DATA statements would be a common place to put pattern data on the TI-99 likewise. But you can feed a value directly to the CALL CHAR command as a constant, if you like, otherwise. In TI LOGO, indeed, a graphical editor exists for patterns. Which can be handy, for the reasons I illustrate.

[@AllGamingStarred]

@@PixelPedant what command do I need to use?

[@PixelPedant]

@@AllGamingStarred MAKESHAPE is the TI LOGO 2 command to define patterns.

[@belstar1128]

4:48 Oh no Nintendo is going to dmca you now.

[@swettyspaghtti]

Is this guy on mushrooms??????????????