Barcodes in the Supermarket

Bar Codes

Bar codes are present on the products of all Eastern european countries, America Canada and Japan, In Britian two sorts of bar codes are commonly used they comply to EAN 13 and EAN 8 standards. EAN stands for European Article Number" This is a 13 figure number that appears thus:

The EAN is widely used in it The first two characters are called the flag characters, they identify the country of origin. The next ten characters are called the data characters, the first five of these identify the manufacturer of the item and the last five identify that manufacturers product. The last character is used as the check digit.

Calculating the check digit for the EAN-13 code The last character is used as a check digit. This is calculated from the previous twelve digits. The purpose of this is to prevent any reading errors. Sometimes there may be an error when reading in the code or maybe an error in the printing of the code. Check digit calculation method is as follows;

Calculating a Check digit for the EAN-13 code

• Multiply each character in an odd position by x1
• Multiply each character in an even position x3
• Add the 12 numbers obtained, getting a value known as products sum (PS)
• Divide the products sum by 10 (a constant), obtaining the remainder
• Deduct the remainder from 10, obtaining the check digit (CD)
• Place check digit in position 13

When the code is read a self check of the check digit character is performed. This is performed in a similar way to the method for calculating the check digit;

Self Checking

1. Multiply each character in an odd position by x1 (Including the check digit)
2. Multiply each character in an even position x3
3. Add the 13 numbers obtained, getting the products sum (PS)
4. Divide the products sum by 10, obtaining the remainder
5. If the remainder is zero the check digit is confirmed.

PLEASE NOTE YOU WILL NOT BE ASKED TO REPRODUCE THIS MATHS IN THE EXAM. Just to explain the process.

Smaller products can use the EAN-8 bar code This is shorter.

Summary EAN-Code: Character Set: 0 - 9 Encodation:

• Two bars and two spaces are required to encode a character Start/Stop Pattern: Always starts and stop with 3 elements: a narrow bar, narrow space, and narrow bar.
• Code Type: Modular, fixed length (thirteen digits with EAN-13; eight digits with EAN-8)
• Human Readable: EAN-13 all thirteen digits required; EAN-8 eight digits required (the Flag Character, Numbering System Character, and the Check Digit are implied).
• Check Digit: Required (Modulus 10 calculation).
• Encoded Information: Flag Character (Country Code) - Two to three digits Manufacturer Identification Number - Four to five digits Product Identification Number - Five digits Check Digit - One digit
• Allowable Sizes: Sizes for the EAN-13 are determined by a "magnification" factor which is based on the "X" dimension size. These magnifications range from 80% to 200% of the normal size (1.46 inches in width, 1.020 inches in height, "X" dimension - 13 mils).

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