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| == Concept: Running BASIC code from OptROM ==
| | [[Running BASIC Code from OptROM]] |
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| Fm: Stan Wong 70346,1267
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| To: Denny Thomas 76701,40
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| Paul's on the right track about the Basic interpreter. The Basic code never
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| moves but there is a rom call that interprets each tokenized statement. Other
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| rom routines find the next statement to execute. It's been a while but my
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| memory is sort of dim on the subject but each Basic statement in storage is
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| prefixed with the line line followed by the statement tokens followed by a
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| null. Three nulls indicate the end of the program (end-of-statement null
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| followed by a line number of zero).
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| A small program could switch to the option rom, read a Basic line (tokenized)
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| into ram, switch back to system rom, and then feed it to the interpreter loop.
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| There is no housekeeping since Basic takes care of it. Oops, I forgot, as part
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| of each line I believe that there is also the address of the next statement.
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| That needs to be fixed up also. Anyway, it's a fairly starightforward
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| proposition. If there is any interest I can dive back into my notes and
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| re-figure out what's what (in any case I got all my info from Robert
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| Covington's ROM maps in the DLs).
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