Hello. I'm doing DOS programming with the x86. I wish to fully understand how memory is segmented. I already understand that it operates under a segment:offset structure, but, there are still some things I don't understand. I know that segments overlap each other, but, I don't know how they do this. And, I know how to find the linear address (far pointer) by using the segment or offset:
E.G., I have the segment 0122h. To find the offset, I multiply 0122h by 16: 18ech is the offset of 0122h. If I just had the offset, I would've just divided it by 16.
To find the linear address (far pointer), I first add a zero to the segment: 0122h => 01220h. Then, I add it with the offset: 01220h + 18ech = 2b0ch.
This is where I get confused at. Now that I have the linear address 2b0ch, what can I do with it (or, what to do with it)?
How do I convert 2b0ch back to the segment? And offset?
How do Segments overlap each other?
How can I implement this information with FASM ( cs:[bx], using far pointers in 16-bit DOS )?
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30 Sep 2007, 05:57