A set of flags in a 16-bit range specifying the page flow direction. Empirically:

• 1 - left-to-right (like English, French, German, etc.)
• 16 - right-to-left (like Arabic, Hebrew, Japanese, etc.)

Comments

Is there a correspondence to the internal coding of the joystick key on the Sony Reader? That key has five positions: left, up, center, down, and right--perhaps they are coded 1, 2, 4, 8, and 16.

It seems odd to have bit-flags for binding direction. Since books are only bound on one edge (or not at all), there seems to be no validity in values that are not powers of two. A more compact coding would be possible.

The Sony Reader has only two positions on its page keys: forward and backward.

One might conceive of books bound on the top or even the bottom. These would not need more than the forward and backward keys, but there might be an optical distinction in where the book spine was drawn, or in the animation of page changes.

A deck of flash cards is an example of an unbound "book".