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              Outbreak Magazine Issue #12 - Article 4 of 18
           '~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~'

Understanding UPC Structure
By: Bland Inquisitor


The UPC, or Universal Product Code, is itself a product of the Uniform
Code Council.  UPCs are designed to help simplify both the "checking-
in" of merchandise at a store, and the sale of a product at the cash
register.  There are 2 main parts of a UPC, the bars that the scanner
reads, and the 12 digits that the bars represent.  A UPC without the
readable numbers is called a "blind bar code."

The first digit of the UPC is called the number system character.  The
NSC serves to key the other numbers as to the meaning and the category
type.  There are 7 category types in all.  0, 6, and 7 represent
groceries and all general merchandise.  2 is for random-weight items,
like meat and veggies.  3 is for diet, health, and drug items.  4 is
reserved for in-house items, and 5 is for coupons.  The UPC for a
coupon identifies the scanned symbol as a coupon, identifies the issuer
of the coupon, makes sure the item to be discounted has been scanned,
and presents the coupon value.

The first groups of 5 digits, called the manufacturer code, are
assigned by the UCC, and represent the item vendor.  Companies have to
pay an annual fee to be included in the UPC vendor registry, and the
numbers are generated internally by the UCC. This means, I'm sorry to
say, that we can't pool our money and buy the vendor code "31337."
78742 is owned by the great Satan herself, Wal-Mart, and is used for
private label and import products, like Sam's Choice.

The second set of 5 numbers is called the item code.  Every
manufacturing company has an employee that assigns a unique item code
to every product the company he/she works for.  Item codes can be the
same between vendors, because the manufacturer codes will differ.  So
the item code for Trojan Magnums and Mickey's 40oz can both be 31337.

The last number is called the check digit.  What it does is to make
sure the scanner has correctly "read" the UPC.  When the scanner reads
the UPC, it adds up numbers that reside in the 1, 3, 5, 7, 9, and 11
positions.  It then multiplies that number by 3.  Then it adds the
numbers in the even positions, excluding the check digit, and adds that
total with the first number it got.  It then determines what number it
would take to make the final sum a multiple of 10.  That number is the
check digit.  On 2600 magazine, the UPC is 7-25274-83158-6, with 6
being the check digit.

So the numbers in the odd position, 7,5,7,8,1, and 8, add up to be 36.
36 x 3 is 78.  The numbers in the even positions, excluding the check
digit, are 2,2,4,3,and 5, and they add up to be 16.  16 + 78 is 94.
The number that need to be added to 94 to make it a multiple of 10 is
6.  Therefore, the check digit in the 2600 bar code is in fact 6.

Once the scanner determines it has a valid UPC, it sends it to the
store's point-of-sale (POS) database to look for the price assigned to
the UPC.  If the database returns a match, then you get charged.  If
the UPC does not match an item in the POS database, then a not-on-file
(NOF) error is returned.  Nothing can be done about a NOF at the
register, but if a store employee gets an NOF on his/her symbol,
telzon, intermec, whatever, they have the option to "70-type" the item.
A 70-type temporarily adds the rogue UPC to the store database.
Usually, a 70-typed item expires after 30 days.

"Hey Bland, is there a way I can learn to tell what numbers the bars
represent so I can impress the ladies with my mad h4x0r-vision?"  I'm
glad you asked.  It's pretty hard to do, but if you take as much pride
in being able to do weird stuff as I do, then the result will merit the
challenging work.

We all know that bar codes are made up of black bars of varying sizes.
The thinnest bars are 1 pica wide, and they range up to 4 in width.
UPC structure is a little like Morse code, in that the spaces between
the bars matter as well.  The handy part about this is that the first 3
lines in any UPC are always 1.  That is to say one black bar of 1 pica,
followed by one space of 1 unit of what we'll call a "space unit," (SU)
because it is not one pica, but it is the standard by which we will
measure spaces. And then is concluded with another bar of 1 pica.
After these 3 events, the manufacturer code can be deciphered by using
the following.

In all these formulas, the first number is the bar, the second number
is the space, and so on.  So 0 equals a bar of 3 pica, followed by a
space of 2 SU, followed by a bar of 1 pica, and concluded with a space
of 1 SU.

0 = 3 2 1 1
1 = 2 2 2 1
2 = 2 1 2 2
3 = 1 4 1 1
4 = 1 1 3 2
5 = 1 2 3 1
6 = 1 1 1 4
7 = 1 3 1 2
8 = 1 2 1 3
9 = 3 1 1 2

Then, after the manufacturer code, there is a 1 1 1 1 that signifies
the item code will be next.  The same chart should work for the item
number, but in some cases may not.  If the chart stops making sense for
the item number, then it has been optically reversed.  if that is the
case, use the following chart in a sort of "reverse-negative" style.
For the "reversed "item code, the numbers will be simply be reversed.

0 = 1 1 2 3
1 = 1 2 2 2
2 = 2 2 1 2
3 = 1 1 4 1
4 = 2 3 1 1
5 = 1 3 2 1
6 = 4 1 1 1
7 = 2 1 3 1
8 = 3 1 2 1
9 = 2 1 1 3

After the check digit, there is a 1 1 1 that acts as the "stop"
trigger.

Shouts:  StankDawg, Dual, and everyone at the DDP.