This encoding can only represent an even number of digits (odd digits are represented
by bars, and even digits by the interleaving spaces). The name stresses the fact
that two of the five items (bars or spaces) allocated to each symbol are wide,
while the rest are narrow. The checksum digit is optional (can be disabled via
check the "Without checksum" option in "Options" dialog).
Since the number of digits, including the checksum, must be even, a leading zero
is inserted in the string being encoded if needed (this is specifically stated
in the specs Barcode Creator have access to).
