How do bar codes work?

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The entire system is complete wizardry to me. The laser itself is witchcraft but the most amazing part is the database. I could imagine that stores somehow associate a code with a product when they add it to their inventory system but what prevents two manufacturers from using the same bar codes on different products. Is there a master database somewhere and who is responsible for managing it?

Edit: I really appreciate all the answers about the database aspect of this but I am still wondering how the actual laser works. Seems like it has to be fairly simple because the technology has been around for decades, long before ‘modern’ computers.

In: Technology

UPC – Universal Product Code. Don’t know the specifics but you have to apply and get a code for your product. Hence, “universal”.

When a manufacturer produces a product it has to pay for each of those number codes that are attached to the bar code scanned at checkout. Yes each product has a unique barcode for itself. From type and size (think different size boxes of the same cereal at the store) the manufacturer pays for them. It’s a long number too right? It can be broken down like a phone number with area code first…it is more specific than that though. Starting with the general product type, then country it was manufactured in, then the manufacturer’s company code, then that specific products code. The bars above the number are kind of like a number code for the laser to read. The size and spacing represent separate numbers. Pretty cool and a universally accepted way to track purchases, keep stock of an inventory, and maintain the extensive catalog of products out there. 😊

Barcodes don’t really need to be like a complex thing. Just helps identify a product. You can register UPC codes but I feel like that’s pointless. Maybe if you’re in an industry where your uploading huge catalogs of products from different vendors and such, it would matter more.

UPC has manufacturer ID prefixes. The first 6 digits of the number just identify the manufacturer. So lets say you are a new company wanting to make products. You register with the UPC database and your company gets assigned the value, let’s say, 999123. All your products must start with those digits. You can have a product called 9991230000000001, then your next product is called 9991230000000002, then your next one you call 9991230000000003, then maybe you make a jump and on a whim you call the next one 999123000050000. You can do whatever you want with the numbers 999123000000000 through 999123999999999, but must keep your products in that range, because 999122xxxxxxxxx and 999124xxxxxxxxx will be some other companys’ ranges.

(There are several versions of UPC, some are less digits and some are more, but for all of them, the FIRST 6 have to be your company’s ID so you don’t clash with anyone else.)

There are many universal ID number systems that have the same kind of problem: like the MAC hardware address of network interfaces (that 12 hexidecimal thing you see in your network config options some times). They solve them the same exact way – by assigning a range of numbers to a manfacturer and there’s penalties and fines for using a number outside your assigned range.

In addition to all this, one would think the large sellers, Kroger, H-E-B, Walmart can have their internal barcodes without paying anything or telling anyone, as long as they only sell in three own stores.