In article ,
Dave wrote:
I work on MacBook Pro and jump back and forth between XP and Leopard. I have CS loaded on BOTH sides. When I save a TIFF file CD gives me the option of saving it with the IBM PC Byte order OR Macintosh Byte order. I’m so confused?!?!
Which way should I save it and why?
The short answer: It doesn’t matter.
The long answer: "Mac byte order" is actually "all non-Intel-processor byte order." For various arcane technical reasons going all the way back to the Intel 8008 and 8080 processors invented back in the early 1970s, Intel processors have long worked with data in "little-endian" format, meaning that the "littlest" bytes come first in a word.
In non-technical jargon, think of it this way. Suppose you want to write a number like 1000. If you put the little part first, instead of writing 1 0 0 0, you would write 0 0 1 0. You would take each two digit pair of numbers and swap it with the two digits next to it.
So you would write the number 1,403 as 0314. You would write the number 18,549,023 as 54182390. (You’d take the 18 and the 54 and swap them, then take the 90 and the 23 and swap them.)[1]
This is how Intel processors work with numbers[2].
When you save a TIFF file in PC byte order, you take the stream of numbers and swap pairs before you record it to the disk. If you write it in Mac byte order, you simply write the numbers to the disk without swapping anything around.
Any program written in, oh, the last 15 years or so can read a TIFF written either way. So the practical answer is, it doesn’t matter which you choose.
[1] Most technically, the Intel processors swap bytes, so you’d actually translate decimal numbers into hexadecimal before doing this swap. But that’s not necessary to getting a basic understanding of what’s going on.
[2] Modern Intel processors can be set to work with numbers in little-endian or "normal" (big-endian) format. But Windows works in little-endian format.
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