system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How are bar codes regulated and standardized? How do they prevent two items having the same barcode?
gpt
Bar codes, conceptually, don't have any system to prevent duplication, but there are systems that use bar codes that enforce uniqueness.  The UPC codes you see on grocery store items are one of them.  In that system the first half of the digits are a manufacturer code (and some other data), unique to each manufacture.  The second half is up to the manufacture to control to assign to each of their products uniquely.