Scenario: I am reading a book using my Kindle app on my iPad. I advance a page, and there’s a break mid-way down the page: a new section with a heading.
As I read that page, I remember something I want to check. I hit the Back arrow a few pages and find the sentence I needed. I hit the Forward arrow to return to my current spot - and when I do, the new Section and Header is at the top of the page.
How and Why does this happen?
AFAIK, each chapter is saved as a separate file. By starting chapter with a new page, the previous chapter can be removed from memory.
A book is stored as all one file on the device, though I couldn’t tell you exactly how the device handles loading it into memory.
I have no experience with the Kindle app for iPad specifically, but I assume it works about the same as on other devices. There’s nothing in the ebook file itself that determines which part of the screen a particular bit of text should appear on (which you can see for yourself if you change something like the font size). I don’t know why the specific phenomenon described in the OP occurs, but I suspect it can be explained by the minor reformatting the device/app does to avoid things like widows and orphans.
I’ve also noticed this phenomenon on my Kindle. I think Thudlow Boink’s explanation concerning “widows and orphans” is on the right track.
As a guess I’d say that the algorithm keeps some kind of ongoing state that it uses to keep breaks in lines and paragraphs to a minimum. It starts with a “beginning of book state” that it updates with each advancing page.
This state isn’t reversible in that it doesn’t contain enough information to enable it to be “unwound” when you back up, so backing up necessitates a new “start state” that is more or less sufficient to minimize the widows and orphans problem but that doesn’t necessarily produce the exact same result going forward.
Without getting my Kindle and experimenting, I’d guess that when you page backward you’ll see widows and orphans that would be eliminated if you paged forward.
I can wrap my brain around that…