Segment Addresses

[jolson88]

Howdy all. I'm in the middle of reading the "Assembly Language: Step by Step" and I think I've found some typos (either that, or I don't understand this stuff as well as I thought ).

When it comes to segment addresses, each successive segment address is 16 addressable units from the last one, is that right? So, segment address 0000h would refer to physical address 0000h, but segment address 0001h would refer to physical adress 0010h?

I ask this because at one point he said that video memory starts at 0b80h:0000h which is equivalent to 0000h:0b80h. Isn't real mode address 0b80h:0000h actually equivalent to physical address 0b800h, not 0b80h? Or am I way off?

This is just off the top of my head (which is probably a good thing as it'll show if I actually understood or not).

Thanks!

[Candy]

I ask this because at one point he said that video memory starts at 0b80h:0000h which is equivalent to 0000h:0b80h. Isn't real mode address 0b80h:0000h actually equivalent to physical address 0b800h, not 0b80h? Or am I way off?

You're right, he's wrong (if you recall correctly). However, that's not where video memory is.

Video memory (text, assuming VGA) is at 0b8000h, or 0b800h:0000h

[jolson88]

I ask this because at one point he said that video memory starts at 0b80h:0000h which is equivalent to 0000h:0b80h. Isn't real mode address 0b80h:0000h actually equivalent to physical address 0b800h, not 0b80h? Or am I way off?

You're right, he's wrong (if you recall correctly). However, that's not where video memory is.

Video memory (text, assuming VGA) is at 0b8000h, or 0b800h:0000h

Ah, I recalled it wrong off the top of my head. You're address sounds right. Since I'm reading an older copy of the book, I wouldn't be surprised if it was a "misprint" that's been corrected since.

Thanks for the confirmation!