The Museum of HP Calculators

HP Forum Archive 09

 HP-41 Bar-Code checksum algorithm.Message #1 Posted by Diego Diaz on 28 Nov 2002, 6:45 a.m. Hi again! Does anybody here know how is the HP-41 Bar-Code checksum calculated?... (And wants to share this info :-) Thanks in advance.

 Re: HP-41 Bar-Code checksum algorithm.Message #2 Posted by Vassilis Prevelakis on 28 Nov 2002, 7:53 a.m.,in response to message #1 by Diego Diaz The "Make You own HP41C Barcode" Manual is included in the MoHPC CDROM collection. The Basic programs are essentially unreadable (what a horrible language), but the algorithms and flowcharts are all there. The manual is in file packs/hpbc.pdf **vp

 Re: HP-41 Bar-Code checksum algorithm.Message #3 Posted by Tony Duell (UK) on 28 Nov 2002, 6:10 p.m.,in response to message #1 by Diego Diaz My 'LIF Utilities for Linux' package includes programs to produce HP41 program and data barcode, and of course they calculate the checksums. These programs come as (hopefully) commented C source code, so you might be able to figure out the algorithm from there. It'll make more sense if you have the 'Create your own HP41 barcode' book, though

 Re: HP-41 Bar-Code checksum algorithm.Message #4 Posted by Diego Diaz on 29 Nov 2002, 5:19 a.m.,in response to message #3 by Tony Duell (UK) Hi! Thank you both for your comments. Finally I've got the desired algorithm and... it was here at MoHPC!!: http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=42 An article posted by Dan McDonald (my gratitude for him), wich includes an Excell file "HP_ListA.xls" with an annotated macro for the barcode generation. The "real thing" is fairly easy: (sum of bytes 2-16 (or the last byte if less in row) + previous row checksum byte) MOD 255. Again, thanks and cheers from the middle of the Athlantic Ocean ;-)

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