b-<var>V</var>.tar.lz</code>,
where <code><var>V</var></code> is the version.
Since 1996, each version has been a four-digit year followed by
lower-case letter (<samp>a</samp> through <samp>z</samp>,
then <samp>za</samp> through <samp>zz</samp>, then <samp>zza</samp>
through <samp>zzz</samp>, and so on).
Since version 2022a, each release has been distributed in
<a href="https://pubs.opengroup.org/onlinepubs/9799919799/utilities/pax.html#tag_20_94_13_06">POSIX
ustar interchange format</a>, compressed as desc