Sam (UK), Interesting the way that you describe this trainer''s method of simulating a simple 4-bit microprocessor. I think this may be one of the simplest examples of what we call a bytecode interpreter. This is the technology that famous languages such as Smalltalk and Java are built on top of. $)

Sorry to double-post but... Duncan, that video of yours is certainly interesting! Kind of weird but I suppose instructive to have the user, some naive kid, have to wire up stuff like the display, that should be connected permanently.

Then again... there were only so many I/O pins available. Were there any experiments in the manual with connecting up to other circuits? Did it come with other components? Maybe a tie-in with the other Science Fair kits would''ve been good. So you could connect the computer to other circuits and have it do... stuff. Since it is a MCU trainer and that''s what they''re supposed to do. If you wanted to really learn programming you''d be better off with a BBC Micro or ZX Spectrum with an assembler and a decent book. "ZX Spectrum Machine Language For The Absolute Beginner" by William Tang was great. Started off explaining memory locations as cardboard boxes with numbers written on bits of paper in them. You know the drill! But pretty quickly moved to writing real programs and interfacing with the operating system.

This little box of tricks is a great curiosity but to be honest I think would have disappointed a lot of kids. For less money you could get a box that''d let you control relays and read switches from a computer in BASIC or machine code. The BBC and Commodore machines had built-in user ports for just that, the BBC even having an ADC!

You''d be able to get a lot more done, and learn more about the subject, like that. Of course you''d need the computer too but you''d want that anyway for the games!

Tor, I imagine the LEDs aren''t labelled in binary for two reasons. One is simplicity and user-friendliness. The other is that the TMS1000 didn''t expose it''s bus to the outside world. Only a few I/O ports, like an Arduino or other microcontroller, since it is a microcontroller.

Sounds like this thing ran a sort-of "emulator", interpreting a program written in a very terse binary format. Could a TMS1000 switch to running code from RAM? I don''t think it could since RAM is 4-bit and I think code was 8-bit. So that would leave storing the program in RAM and interpreting it.

It''s fair enough, it still gives an impression of machine code programming, and is probably less mind-bending than the TMS''s own ASM would be! 48 steps! Just enough for 1 or 2 loops to do a bit of beeping.

A user couldn''t program the TMS series. Instead your company, that was making an alarm clock or calculator or whatever, would write the program in a text editor on a minicomputer or mainframe. Stacks of cards are mentioned although hopefully that''s just as an abstraction!

Then your programmer and TI would work together to ensure it would work, and test it on a software emulator. Eventually, when it was ready, TI would make a mask and produce you a few prototype chips with your program in the ROM, real immutable ROM.

If that went well, it went on to production and off come your thousands of chips!

The chip was like many MCUs intended for calculators, etc, in that it had some support for LED or VFD displays built into the hardware. So you wouldn''t have to bit-bash as much as you might with a modern MCU. OTOH a modern MCU does very well at bit-bashing, with onboard timers, counters, and a high enough clock speed to be able to do all that.

I wonder about stuff like Astro Wars and the many other VFD home arcade games of the early ''80s. As well as the LED and LCD ones. But VFD mostly cos they were so interesting, and produced the best display for a game.

Were these 4-bit? Must''ve been hell to program! Or at least you''d need to be very methodical and keep everything organised on paper, doing actual coding in small blocks that fit to the plan. Or did they use 8-bit MCUs? Were PICs about then?

Some of the early LCD games I think would''ve worked as custom state machines. And there were dozens of cheap ones where the gameplay was identical, only the LCD was changed, from aliens to horses and cowboys.

The early Nintendo programmers, I think Gunpei Yokoi, RIP, talked about re-purposing calculator chips to produce Game And Watch. Each screen element was a unit that would otherwise have been a segment of a 7-segment number!

Anyway... interesting machine!