Re: [Pgubook-readers] immediate mode addressing vs address

[Brian Scott]

Tom Felb wrote:
> Hi group!
>
> I have a hardcopy version of "Programming from the Ground up" and I 
> don't understand what's the difference between immediate mode 
> addressing like movl $12, %eax (load eax with number 12) and 
> $variablename, %eax (load the address of variablename into eax)
>
> That's the same syntax with the dollar sign? I'm a little bit confused!??
>
> Thanks for any help!
>
> tfb
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variablename in this case is a label. When the program is assembled, all 
instances where that label is used is replaced with the memory address 
of the data under that label. Something like movl variablename, %eax 
would load the data at that memory address into eax, while using 
immediate mode moves the actual memory address itself. So movl 
$variablename, %eax is also immedite mode. Hope that helps.

Brian Scott