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MEMORY ADDRESSING QUESTION

 
 
Rob
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      05-27-2004
(Please forgive any violations of netiquette; new to the list.)

What does it mean to " address" memory? I understand what a memory address
is - a location in which information is stored - but when used as a verb, I
don't understand the meaning. For example, why can a 32 bit OS only
"address" a maximum of 2 gig of RAM?

Thanks.


 
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Scott Gardner
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      05-27-2004
"Addressing" memory means to describe a location in memory by using an
address. Let's say that your operating system only uses four bits for
memory addresses, and let's assume further that each address refers to
one byte of memory.

You have sixteen possible memory addresses that you can refer to (0000
binary through 1111 binary). Each address refers to one byte of
memory, so this particular operating system would only be able to
"address" sixteen bytes of memory. If you allow the memory addresses
to be 32 bits long, you can specify a little over 4 billion different
addresses. If each address refers to one byte of RAM, then you can
address 4 GB of RAM.

While a 32-bit operating system might be able to address 4 GB of
memory, individual applications running under the operating system
might only be able to address 2GB of memory. As an example, I believe
Windows XP Home can recognize 4 GB of RAM, but I don't think
individual applications can access more than 2GB each.

In short, the amount of memory an operating system can "address" is
dependent on how many addresses are available, and how much memory is
located at each address.

Scott Gardner


On Thu, 27 May 2004 01:23:05 GMT, "Rob" <(E-Mail Removed)> wrote:

>(Please forgive any violations of netiquette; new to the list.)
>
>What does it mean to " address" memory? I understand what a memory address
>is - a location in which information is stored - but when used as a verb, I
>don't understand the meaning. For example, why can a 32 bit OS only
>"address" a maximum of 2 gig of RAM?
>
>Thanks.
>


 
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Rob
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      05-27-2004
Scott:

Thank you very much; I do appreciate it.

"Scott Gardner" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> "Addressing" memory means to describe a location in memory by using an
> address. Let's say that your operating system only uses four bits for
> memory addresses, and let's assume further that each address refers to
> one byte of memory.
>
> You have sixteen possible memory addresses that you can refer to (0000
> binary through 1111 binary). Each address refers to one byte of
> memory, so this particular operating system would only be able to
> "address" sixteen bytes of memory. If you allow the memory addresses
> to be 32 bits long, you can specify a little over 4 billion different
> addresses. If each address refers to one byte of RAM, then you can
> address 4 GB of RAM.
>
> While a 32-bit operating system might be able to address 4 GB of
> memory, individual applications running under the operating system
> might only be able to address 2GB of memory. As an example, I believe
> Windows XP Home can recognize 4 GB of RAM, but I don't think
> individual applications can access more than 2GB each.
>
> In short, the amount of memory an operating system can "address" is
> dependent on how many addresses are available, and how much memory is
> located at each address.
>
> Scott Gardner
>
>
> On Thu, 27 May 2004 01:23:05 GMT, "Rob" <(E-Mail Removed)> wrote:
>
> >(Please forgive any violations of netiquette; new to the list.)
> >
> >What does it mean to " address" memory? I understand what a memory

address
> >is - a location in which information is stored - but when used as a verb,

I
> >don't understand the meaning. For example, why can a 32 bit OS only
> >"address" a maximum of 2 gig of RAM?
> >
> >Thanks.
> >

>



 
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