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Retrocomputing

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  • What's special about the range $6AE00 to $6B7FF? I've seen such behavior, but find myself bewildered as to what would cause it to yield wackiness? My guess would be that code that looks for line numbers to be below 65280 [$FF00] decides that the above values meet that criterion, but that the decimal-to-binary conversion somehow ends up yielding values in that range. Since the system tests for immediate mode by looking for the MSB of the line number being $FF, having the system inconsistently think a line is or isn't immediate mode could wreak havoc on things. Commented Dec 15, 2016 at 16:11
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    @supercat The range $AB00 to $ABFF, which is 43776 to 44031, when followed by an additional decimal digit (0-9), triggers the bug. Look at my answer for the details on the actual bug (it's much too long for a comment). Commented Dec 15, 2016 at 20:58
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    also 'PRINT 5+"A"+-5' (i.e. positive number+string+negative number) will crash Basic, but in a way that can be intercepted by placing a jump at $0001. Commented Feb 12, 2017 at 3:02