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#OS9 68K EMULATOR MAC MACOS SERIES#
There's a series of books, starting with Color BASIC Unravelled, that have a disassembly of the various versions of BASIC that run on the CoCo. tokenized BASICs of that era (almost all Microsoft-based, ultimately going back to Altair BASIC): the extreme memory constraints of Altair BASIC (by default the Altair came with 1K of RAM the first Altair BASIC version needed 4K) forced some design decisions that MS stayed with for a long time, at a catastrophic cost in runtime.
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(On the off chance that you have a Matchbox CoCo, an FPGA-based system that Roger Taylor has created, there's a version for it, too, thanks to the work of Bill Nobel, but for now, the CoCo 3 with CoCo SDCand those two emulators are the supported setups.)Ībout BASIC09 vs. Then if you have a CoCo 3 with 512K RAM and a CoCo SDC (which lets you keep disk images on an SD card), or have MAME or the VCC emulator set up to emulate a CoCo 3. The simplest way to get going with BASIC09 would be to get the NitrOS-9 "ease of use" edition. This makes the runtime faster, since it's much simpler. Whereas in a compiled form, it can be reduced to an RPN style where the evaluator doesn't have to worry about that any more. Having to do the multiplication and such before the additions, etc. In a normal tokenized system, the expression runtime has to account for the operator precedence AT runtime to properly evaluate this expression. But since the DEC BASICs WERE compiled, rather than just interpreted raw, the system was able to take statements like this and rewrite them internally to be more "normal".Īlso, consider: 10 A = 1 + 2 * 3 / 2 + 4 * SQR(2) Put in "invisible tokens" or whatever specifically to support this kind of construct, but in the "every byte counts" of vintage BASICs, that's a lot of work for not a lot of value. But you can easily see the runtime encountering the SUM10 = SUM10 + A(I) with out knowing that it should do so yet (due to the IF statement) or even that I is properly in range or not (since it's not even been initialized properly yet). Token based runtimes, much like i-code, simply take what they see and execute it in the context their in. While this could be represented in tokenized form (in order to regenerate the source line), it can not be easily interpreted executed from that tokenized form.
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They used "statement modifiers".Ĭonsider: 10 SUM10 = SUM10 + A(I) IF A(I) > 10 FOR I = 1 TO 10 With i-code, you can't do that.Īnother example is if you look at the DEC BASICs.
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Many BASICs, when you type LIST, simply parrot back out the tokenized data in long form. I can't speak to BASIC09 specifically, but there's quite a difference between an "i-code" and a tokenized form.Īt a minimum, the i-code, in the end, need not look at all like the source code, whereas the tokenized form effectively IS the source code.