// Understanding UPC Structure
//
// by bland_inquisitor
//
// http://www.oldskoolphreak.com

I don’t know if UPC’s have been done to death, but in case anyone doesn’t know
how they work, here’s the shiz.

Quick, go grab one of your 2600 mags so we’ll all have the same reference.

The small 7 in the left hand corner before the bar code is called the Number
System Character. The NSC serves to key the other numbers as to the meaning
and the category type. There are seven category types in all. 0, 6, and 7
represent groceries and all general merchandise, like magazines. 2 represents
random weight items like meat and produce. 3 represents health and drug
related items. 4 represents in-house use only, and 5 is used for vendor
coupons. The UPC code for coupons identifies the scanned symbol as a coupon,
identifies the issuer of the coupon, the product that is offering the
discount, and presents the value of the coupon.

The next five digits, in this case 25274, are assigned by the Uniform Code
Council, and represent the vendor. This set is called the Manufacturer’s ID.
78742 is owned by Wal-Mart, and is generally used for private label or import
use (like Sam’s Choice).

The next set of five numbers, in our example, 83158, are assigned and
controlled by the vendor, and is called the Item Code. The Item Code, well,
represents the item. This Item Code is unique for each item type.

The little 6 after the bar code is called the check digit. It is the 12th and
last digit of the code. It serves as a numeric check of the other 11 digits,
when the stores calibrate their UPC scanners.

I’ll close with my standard disclaimer. This is for educational purposes only.
I feel that everybody should know how things work, especially the things that
are so commonplace. I, and the rest of the white-hat community have an
obligation to teach people about technology, and how to use it responsibly.
If you somehow do something illegal with this or any information I provide,
FUCK YOU. It’s people like you that keep me from being able to hold my head
high as a hacker. It’s people like you scene-whoring around that make me have
to explain that hackers are into breaking into computers the same way TV
repairmen are into delivering babies. I’ll quit here, because if I don’t, the
disclaimer would be longer than the article.