teaching programming to kids - Re: Looking for 8080/Z80 BASIC

Richard wrote: I am very interested in this thread since I design computers for children, with one of the main goals being to get them to learn programming (more for the side effects of learning how to debug and how to incrementally arrive at working solutions). Back in 1983 I designed a 6809 based computer with Logo in ROM. One issue was the problem domain. Turtle graphics are great, but robotics and games are even more attractive. Robotics was already being worked on in the Lego Logo project, so I concentrated on games. Having multiple concurrent turtles like in Coco Logo would be a good start, and allowing the turtles to have any shape (in TI99/4A Logo you had sprites which could change shape, but those were not turtles) would really help. I also added object orientation, and this feature got used more and more so I ended up switching to Smalltalk in 1984. That is absolutely critical. But one limitation of Logo was that it wasn't self revealing. I have played with many implementations of the language and if I don't have written documentation I can't get very far (specially in implementations based not based on English). Unfortunately, the children didn't get that documentation. If it was available at all, the teacher normally kept it to him/herself. Contrast that with Basic on the Sinclair machines. Every possible command was printed right there on the keyboard. You could try random things and learn without a book. But you normally had a book and a few magazines. Back in the 8 bit era it was hard to do something about this, but in a modern system all the documentation you could want should be in the system itself. One interesting alternative, which I considered for that project, was the 1978 Super Basic for the Bally Astrocade (a Z80 machine, so we are back to the start of this thread) which claimed to be self revealing. It had GOSUB but also allowed you to define your own named functions (it called them macros). These functions used INPUT to read the values supplied as arguments at the call site, but if the argument was missing it would print the associated prompt text and read the value from the keyboard. And all the built in commands worked just like this, so typing in a parcial expression would make the computer print out what additional data it needed. This interpreter was not sold, so a repackaged version of it was developed and sold as the Datamax UV-1 high end machines for video artists and the language was renamed to Zgrass. A side effect of having one Basic command in each key on the Sinclair machines (to make typing in programs tolerable on the horrible keyboards) was that the beginner didn't have to worry about syntax errors. If you typed something and the computer interpreted it as something else you saw it right away and could fix it before going any further. By the time you hit ENTER the syntax was ok, though you might still have logical errors. The free form text entry in Logo made it easier to make syntax errors, though misspelled names were more likely to be a problem. A modern alternative for reducing syntax errors is the use of graphical blocks to represent code, like in Etoys or Scratch (two systems implemented in Squeak Smalltalk). It helps a lot in the beginning, though eventually this gets in the way of writing code. One problem that Logo in general had was that it was seen by everyone involved as a very limited tool. As you mentioned, the language itself certainly doesn't lack power. But most implementations were very weak due to the limited memories. A good interpreter will take up most of 64KB and leave little room for the user's programs. So Logo was used for small projects in elementary school while Basic and Pascal were used in high school. And children quickly tire of things they perceive as being uninteresting to adults or older children. So in my project I put in a lot of effort to have a professional quality interpreter. The hardware included a circuit to have a separate 64KB instruction address space in a 32KB EPROM and still have the full 64KB of RAM for user programs. -- Jecel