15 Aug
2024
15 Aug
'24
1 p.m.
On Aug 15, 2024, at 12:46 PM, Peter Ekstrom via cctalk
<cctalk(a)classiccmp.org> wrote:
Hi to the group,
I am tinkering with some C-code where I am working on something that can
process some microcode. The microcode is from a DG MV/10000 machine and
while working on it, I noticed it is in little-endian. That's simple enough
to work around but that had me wondering, why do we have big and little
endianness? What is the benefit of storing the low-order byte first? Or is
that simply just an arbitrary decision made by some hardware manufacturers?
I am mostly just curious.
Thanks,
Peter / KG4OKG
The short answer is "it's historic and manufacturers have done it in different
ways".
You might read the original paper on the topic, "On holy wars and a plea for
peace" by Danny Cohen (IEN-137, 1 april 1980):
https://www.rfc-editor.org/ien/ien137.txt
And yes, different computers have used different ordering, not just characters-in-word
ordering but bit position numbering. For example, very confusingly there are computers
where the conventional numbering has the lowest bit number (0 or 1) assigned to the most
significant bit. The more common numbering of 0 for the LSB gives the property that
setting bit n in a word produces the value 2^n, which is more convenient than, say,
2^(59-n).
paul