The Number 666

in UPC bar-codes

To see the 666 sequence in a UPC bar-code, find a retail item with at least one 6 in the number below the bar-code. The more 6s the better. There are two types of UPC bar-codes. There is the longer 12 digit version and the shorter six digit version. Find a long version with at least one 6 in it first. We will come back to the short version in a bit. For demonstration purposes, I will use the bar-code from a box of General Mills Chex bars below because it has several sixes in it. (Please note that this is not implying anything negative concerning General Mills. All retail items have a similar bar-code.)  

UPC bar-code is made of varying widths of bars and spaces. Both bars and spaces have values that the scanning computer reads. There are four different widths of both bars and spaces. They can be valued as: 

1 for the narrowest bar and space
2 for the medium-narrow bars and spaces
3 for the medium-wide bars and spaces
4 for the widest bars and spaces 

Each number below the bar-code has four bars assigned to it, 2 black, and 2 white bars. Also notice that the bar-code is divided down the middle into two parts. The numbers on the left side have correlating bars in a white-black-white-black order, and the numbers on the right have correlating bars in the opposite black-white-black-white order. Each number is allotted bar space of 7 widths. So the total of each number's four corresponding bars will always add up to 7 widths. The bar width values for each number are:

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

The last bar for each number (as given in red) is a filler bar that makes up the difference for the necessary total 7 value for each number, and it is used by the scanner to establish direction of read. Its main purpose is to establish the direction in which the previous three bars are to be read. Only three bars make up the actual number. Without the fourth, the computer wouldn't know which direction to read the three. It wouldn't know the difference say between a 0 and a 5, or a 4 and a 9. But notice that if you read the sequences of each number's four bars backwards, starting with the red number, there is no other sequence like it. For instance, the backwards sequence of 0 is 1-1-2-3. That sequence cannot be found in the other nine sequences. The same can be said for every sequence.