Re: Byte Addressability And Beyond

On Fri, 3 May 2024 22:26:04 -0000 (UTC), Lawrence D'Oliveiro
<ldo@nz.invalid> wrote:

On Thu, 02 May 2024 08:58:23 -0600, John Savard wrote:
>

To me, it just made sense that, since registers contain quantities, if
you load the value "8" into a reigster, it will contain the number 8.
 
So in a byte operation, the least significant bits of the register are
used.

>
Of course that makes sense.
>
Now, think of main memory as just a holding place for stuff that won’t fit
in registers: why shouldn’t it make sense there as well?

Because that isn't what main memory is. Even if one could think of
cache memory that way, main memory also interacts with input-output
devices.

Although that isn't really the problem.

After all, computational variables can be stored in memory in any
format. The only things in memory that are constrained in format are
character strings, because they get printed on paper for people to
see.

And, as I noted, that is the root of the problem.

Character strings are in big-endian order.

Packed decimal strings should be in the same order as character
strings, so that the relationship between the two is simple and
conversion between the two is quick.

Packed decimal strings of numbers should be in the same order as
binary numbers, because the can potentially share the same arithmetic
unit in some implementations.

John Savard