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Old 16th Jan 2017, 12:01 pm   #14
ionburn
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Join Date: Dec 2014
Location: Lincoln, Lincolnshire, UK.
Posts: 583
Default Re: They don't come much more Vintage than this

I must admit that I began by learning machine code (on 6500 series, Z80 and 6800 series) and except for hand assembly did not really use an assembler. As such when I first looked at progressing to what should have been an easier way I did not get on with it. I could remember the op codes without problem after a while so preferred to use machine code as I visualised the operation of registers etc which is something that tends to get more remote the higher the level of programming language. It made things easier when I came to build my, designed by me, development system for my college course project (6802 based).

With the fixed position in memory of code, as others have said, relative addressing will sort. It depends somewhat on the capability of the monitor(basic system) program. I think this is one of the reasons 'com' files got replaced by 'exe' as this enables the file header to be in a different place to the program itself, just containing a reference jump to the program.

I have not been too involved too much of late, although I notice from the manual of the Arduino controller chips that things have got somewhat more complex than the 6502 etc. That said, unless there is reference to a changed hardware function, things can be built up from basic instructions. With my system I spent many a hour contemplating virtual processors with my own machine language and even programmed the system up to work parallel processing although it was a little unstable (maybe all the pushing and pulling off the stack at each change of thread was the issue as it is easy to forget something - even these days when I do it in far higher level language)
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