If DEFINE WRITE_INT isn't in your manual, then you probably have an older version of PBP
or an old manual before this new define option was added.

Newer versions of PBP include a check for this in the WRITE library. If you have DEFINE
WRITE_INT 1 declared, it automatically disables interrupts before the write, and re-enables
interrupts immediately after the write is complete.

It just saves you from having to remember to do it yourself.