bugProgramming from the Ground Up Book - Bugs: bug #24796, Page 15-16 - ver 1.0 booksize:...

 
 

bug #24796: Page 15-16 - ver 1.0 booksize: Indirect addressing

Submitted by:  dusty <decline0>
Submitted on:  Mon 10 Nov 2008 04:00:36 AM UTC  
 
Category:  None Severity:  3 - Normal
Item Group:  None Status:  None
Privacy:  Public Assigned to:  None
Open/Closed:  Open

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Mon 10 Nov 2008 04:00:36 AM UTC, original submission:  

On pages 15 and 16 while detailing what indirect addressing is, the book tries to compare direct and indirect addressing.  It is very confusing.  The book says:

"In the indirect addressing mode, the instruction contains a register that contains a pointer to where the data should be accessed. for example, if we used indirect addressing mode and specified the %eax register, and the %eax register contained the value 4, whatever value was at memory location 4 would be used. In direct addressing, we would just load the value 4, but in indirect addressing, we use 4 as the address to use to find the data we want".

When the book says "we would just load the value 4", it doesn't sound like direct addressing.  It sounds like immediate mode. And "we use 4 as the address to use to find the data we want" sounds more like what direct addressing is rather than indirect.
I think wording it like this is clearer:

"In direct addressing, we use an immediate mode number as the address to use to find the data we want. In indirect addressing, we use the number stored in a register as a pointer to the data we want."

This is my first book on assembly so either I don't have a clue as to what I'm talking about or I can see the text from a beginner's view point better than the experts who wrote it.  What do you think?

dusty <decline0>

 

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