

As a synching method, it is made so that the file is
4k-aligned, i.e. no records (except those that are longer than 4k by themselves)
are allowed to cross a 4-k boundary. Zero padding is added to fill 
the gap. This of course requires that the first byte of a magic no is never
zero --- then a zero can be interpreted to mean ``jump to the next 4k limit''.

