We have already covered Code 128 and Code 39 barcodes so it seemed right to move onto Code 25 barcodes. Now these are generally a much simpler affair than many other 1d barcodes since they only encode numeric data. Now this is no bad thing if you only want to encode numeric data to link up with a database since simpler of course means there is less to go wrong. This has made it commercially quite popular and has been widely used on cartons/grocery products.
However although it is a simple barcode set it is worth remembering that there are still conventions which must be obeyed, which of course make it a safer read. There are only 2 widths of bar/space and each of the characters is made up of 2 wide and 3 narrow spaces. Importantly there is also a specific start sequence of narrow bar, narrow space, narrow bar, narrow space and an end sequence of wide bar, narrow space, narrow bar. There are various other specification which are worth knowing about if you are still having difficulties and these can be found well explained on our knowledge base.
There is also an optional checksum which is explained below:
- Identify odd/even character positions. The right hand most character is always even.
- Sum all the characters in odd positions.
- Sum all the characters in even positions and multiply by 3.
- Add the values from steps 2 and 3
- Determine the smallest value, which when added to result of step 4, gives a multiple of 10. This is the cheksum character.
This obviously decreases the chance of a misread, but remember as said in earlier posts, it only decreases the chance so if you are processing large volumes of barcodes and need highly reliable data there is no replacement for good quality barcodes and scanning!
Any questions? Just ask!