user111930: Simple question. Is each line in a blkxxxxx.dat file a block?

user13866: Simple answer: no.
The files are not text files and therefore don't have lines.

111930: <p>Simple question. Is each line in a blkxxxxx.dat file a block?</p>
 13866: <p>Simple answer: no.</p>
<p>The files are not text files and therefore don't have lines.</p>
