Bar code choice

From: Jan Karrman <jan_at_it_dot_uu_dot_se>
Date: Fri Sep 05 2003 - 04:54:17 CDT

Hello all!

I have just joined the project since Alan found my bar code fonts
and asked me if I could help with some bar code issues. So here
follows my first contribution.

Of the one dimensional bar codes that I am aware of, and have made
fonts for, Code 128 is the one to use.

>From :

  It is designed to encode all 128 ASCII characters, and will use
  the least amount of space for data of 6 characters or more of
  any 1-D symbology.

Code 128 uses a checksum character that needs to be calculated
and added to the end of the string. A start and a stop character
is also required.

Although control characters (ASCII codes 0..31) are allowed, one
should probably avoid using them in the encoded string for two
reasons: Code 128 requires an extra shift character to be inserted
between certain printable characters and a control character. Also,
some bar code readers have problems reading control characters.
At least my DuraTrax fails to read certain control characters.

Since one should probably avoid the DEL character (ASCII 127) as
well, 95 characters remain. Another possibility is to encode the
string using digits only; Code 128 has a compact representation
of digits-only strings - each pair of digits is represented as a
single character. This gives 100 different characters per bar
code symbol.

A two dimensional bar code is of course better for representing
a lot of data. However, I don't have any such font, and I'm not
aware of any free product. Also, bar code readers for those are
probably much more expensive.

Jan Kärrman
Dept. of Information Technology
Uppsala University
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Received on Tue Sep 30 23:17:01 2003

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