Annexe : codes à barres

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- Left guard bars, or start sentinel, encoded as 101.
- The second character of the number system code, encoded as described below.
- The five characters of the Manufacturer Code, encoded as described below.
- Center guard pattern, encoded as 01010
- The five characters of the product code, encoded as right-hand characters, described below.
- Check digit, encoded as a right-hand character, described below.
- Right guard bars, or end sentinel, encoded as 101.

The first character of the EAN-13 number system code (i.e., the first digit of the EAN-13 value) is encoded in the parity of the characters of the left-hand side of the symbol. That is to say, the value of the first character of the EAN-13 value determines the parity with which each of the characters in the left-hand side of the barcode will be encoded from the following table.

Digit Left-Hand Encoding Right-Hand Encoding Odd Parity (Set A) Even Parity (Set B) Set C 0 0001101 0100111 1110010 1 0011001 0110011 1100110 2 0010011 0011011 1101100 3 0111101 0100001 1000010 4 0100011 0011101 1011100 5 0110001 0111001 1001110 6 0101111 0000101 1010000 7 0111011 0010001 1000100 8 0110111 0001001 1001000 9 0001011 0010111 1110100

NOTE: For "left-hand encoding", odd and even parity is often

referred to as "character set A" (odd) and "character set B" (even).

- An EAN-13 character is represented in 7
elements consisting of 2
bars and 2
spaces.

No bar or space may be longer than 4 elements. The only exception to this rule is the left and right guard bars (3 elements each) and the center guard bar (5 elements long).

- All characters in the left-hand side of the barcode always start with a 0
(space) while all characters in the right-hand side of the barcode
always start with a 1 (bar).

- The "right-hand" encoding pattern is exactly the same as the
"left-hand odd" encoding pattern, but with 1's changed to
0's, and 0's changed to 1's.

- The "left-hand even" encoding pattern is based on the "left-hand
odd" encoding pattern. To arrive at the even encoding, work from
the left encoding and do the following:

1) Change all the 1's to 0's and 0's to 1.;

2) Read the resulting encoding in reverse order (from right to left).

The result is the "left-hand even" encoding pattern.

The parity is based on the first digit of the EAN-13 value.

For example, our EAN-13 is 761234567890.

In this case, the first digit of the number system
code is the first digit 7
, so the parity would be based on
the number 7 in the following table:

1st Number

System DigitParity to encode with 2nd Number

System DigitManufacturer Code Characters 1 2 3 4 5 0 (UPC-A) Odd Odd Odd Odd Odd Odd 1 Odd Odd Even Odd Even Even 2 Odd Odd Even Even Odd Even 3 Odd Odd Even Even Even Odd 4 Odd Even Odd Odd Even Even 5 Odd Even Even Odd Odd Even 6 Odd Even Even Even Odd Odd 7 Odd Even Odd Even Odd Even 8 Odd Even Odd Even Even Odd 9 Odd Even Even Odd Even Odd

- The second number system digit is always encoded with odd parity.
- A UPC-A barcode always has a first number system digit of zero, and
therefore uses exclusively odd parity.

In fact, any EAN-13 symbol which has a first number system digit of 0 is actually an UPC-A symbol, not an EAN-13 symbol. - All EAN-13 symbols (that have a first number system digit that is non-zero) always have three left-hand characters that are encoded using even parity and two that are encoded using odd parity.

7612345678900

- Number System 76,
- Manufacturer Code 12345,
- Product Code 67890,
- Check Digit is 0.

The first digit of the number system is 7.

Consulting the parity encoding table for the digit 7, we find that the parity for the second number system digit and the manufacturer code should follow the pattern:

Odd Even Odd Even Odd Even.

That means:

- the second number system digit will be encoded from the left-hand odd parity table,
- the first digit of the manufacturer code will be encoded with left-hand even parity, etc.

We can now start encoding our barcode with the following steps:

Digit name Numeric Value Encoded with Binary Left Guard - - 101 2nd Number System 6 Odd 0101111 1st Manufacturer 1 Even 0110011 2nd Manufacturer 2 Odd 0010011 3rd Manufacturer 3 Even 0100001 4th Manufacturer 4 Odd 0100011 5th Manufacturer 5 Even 0111001 Central Guard - - 01010 1st Product Code 6 C 1010000 2nd Product Code 7 C 1000100 3rd Product Code 8 C 1001000 4th Product Code 9 C 1110100 5th Product Code 0 C 1110010 Check Digit 0 C 1110010 Right Guard - - 101

The barcode is then constructed by simply concatenating all the strings together.

10101011110110011001001101000010100011011100101010101000010001001001000111010011100101110010101

1 represents a bar and 0 represents a space.

Thus if we convert this string of numbers to their graphical representation we end up with the following barcode:

Informations Gomaro s.a.