Ian, Vincent, P1788
We haven't discussed Level 4 issues much up to now. But my view is that we should keep COMPLETELY above the level of endian-ness. The C standard, if I get it right, is phrased at a level of abstraction above this, and so should P1788 be. We should treat memory as a list of bits indexed by integers - a Turing machine tape (with direct addressing).
The order of things matters for interchange format, e.g. we may specify (lower bound, upper bound, decoration) in that order. For the rest, if a system chooses to store those 3 components in completely separate parts of physical memory, using some silly endian-ness that looks like an FFT butterfly transformation, it's none of our business.
John
On 7 May 2010, at 16:14, Ian McIntosh wrote:
Every halfway reasonable ordering has been done, including little endian bytes within 16 bit halfwords but big endian between halfwords and little endian bytes within 32 bit words but big endian between words.
...
Vincent Lefevre wrote:
On 2010-05-05 10:12:56 -0500, R. Baker Kearfott wrote:
That's an interesting stance since, I think (correct me if
I am wrong), that, except for "big-endian" and "small-endian",
754 does specify formats. Of course, an argument for
not specifying is: "it does not matter what's inside
if what is actually seen is as specified."
Actually, there's more than "big-endian" and "small-endian".
ARM FPA has a mixed-endian format for binary64 (little-endian
32-bit words stored as big endian). And any implementation is
free to store the bit string in any order it wishes.