Q:

why doesn't byte flip involve a simple reversal of order

On the programming calculator I am using, the hex value 0x803F gets turned into 3F80 when I hit the "byte flip" button. However, I would have expected 0x803F to become 0xF308 i.e. a simple reversal of order. Why doesn't a byte flip involve a simple reversal of order?

A:

It seems like you are thinking that the bits should be reverse but endianness refers to the bytes not the bits. 0x803f represents two bytes, the first is 80 and the second is 3F. So reversing the endianness causes the value to become 0x3F80
https://en.wikipedia.org/wiki/Endianness#Big-endian

