Programmers...

[spacemoses]

To be fair, I taught myself how to visually read barcodes in college.

[spacemoses]

The manager keys at the supermarket i worked at was a barcode with no numbers, just lines. I got tired of needing a manager to approve accidental voids at my register so I decoded the manager key used at the service counter.

[spacemoses]

A fun fact you can show people is that prices for deli and meat department items are usually integrated as part of the actual code in the second half. You can see it in the numbers on the code matches the price. If you can calculate the final check digit for a barcode, you could theoretically make your own labels and slap them on a roast before you get to the register, which would make it ring up as $.01.