If the "rewind on close" flag is false and the tape is opened for
read-only permissions, then there are two possibilities for behavior
from the tape driver.  The two modes are called "bell" and "berkeley"
compatibility, derived from the different behavior on the two
differing versions of UNIX.

Bell compatibility tells the driver to advance the tape past the next
logical end-of-file mark following the data just read.

Berkeley compatibility tells the driver to not reposition the tape drive
in any way whatsoever.
