Understanding Bar Codes

UNDERSTANDING BAR CODES

TABLE OF CONTENTS UPC Bar Code

How They Are Commonly Used … 4

Anatomy of A UPC (A) Bar Code … 5

UPC (A) Bar Code Glossary … 6

How It All Works … 7

Testing The Algorithm … 8

2D Bar Code / Data Matrix


Anatomy Of A Data Matrix … 12

Data Matrix Bar Code Glossary … 13

Benefits of The Data Matrix … 14

QR Code


The Anatomy Of A QR Code … 17

QR Code Glossary … 18

How It All Works … 19

2

UPC BAR CODE The UPC ( A ) bar code symbol, is one of the most

common applications of bar code technology and is

seen on products everywhere.

3

HOW THEY ARE COMMONLY USED Bar codes are everywhere and they are used to identify

everything from auto parts to hospital patients. The

Universal Product Code is used to identify retail items in

virtually every store and market in the country.

4

95 MODULES WIDE!

THE ANATOMY OF A UPC (A) BAR CODE

MANUFACTURER ID CODE ITEM NUMBER

LEFT GUARD! RIGHT GUARD!CENTER GUARD!

CHECKSUM DIGIT

MANUFACTURER IDENTIFICATION

NUMBER

THE FIRST SIX FIGURES DEFINE THE MANUFACTURER’S

IDENTIFICATION NUMBER

THE NEXT FIVE DIGITS ARE THE ITEM NUMBER

5

UPC: Universal Product Code MODULES: The vertical bars that make up the bar code symbol. Numbers are created by patterns of filled

and unfilled modules. 84 modules are used for digits, and 11 are used for the guards that define the symbols

boundaries.

GUARDS: Left and right guards mark the beginning and end of the symbol and the center guard marks the

division between the manufacturer and product codes.

MANUFACTURER CODE: Is made up of the first six digits and is distributed and managed by the UCC

(Uniform Code Council).

MANUFACTURER IDENTIFICATION NUMBER: Used to identify the particular numbering system used by the

manufacturer.

ITEM NUMBER: Assigned to each product and is defined by the last five digits.

CHECKSUM: A single digit used for error checking.

UPC (A) BAR CODE GLOSSARY

6

First, the scanner flashes a laser across the code reading the lines and spaces across. !

In a fraction of a second the scanner makes several calculations to determine the orientation of the code and then error checks to make certain that the scan was valid. !!It does this by testing an algorithm against the checksum digit.!

HOW IT ALL WORKS

1+3+5+7+9=25

7

First the scanner sums the digits in the odd positions !

TESTING THE ALGORITHM

Then it multiplies that !result by three!

Next, it sums the even !place digits !

And adds the two sums! That result is divided by ten! The remainder is subtracted from ten to verify the checksum. If the

checksum doesn’t match, the scanner reports an error and the

code must be re-scanned.!

0+2+4+6+8=20 20x3=60 1+3+5+7+9=25

60+25=85 85/10=8R5 10-‐5=5

8

2D BAR CODE / DATA MATRIX Two dimensional bar codes are called so because the reader

scans both horizontally and vertically across the symbol,

unlike linear barcodes.

9

Along with the less popular PDF417 (actually stacked linear)

and Aztec symbologies, Data Matrix is commonly used in

healthcare. Because of its accuracy, efficiency and small

size, it works particularly well on patient wristbands and

medication labels, as it is less likely to distort around curves

and takes up less space, in addition to being highly

readable and accurate.

10

HOW THEY ARE COMMONLY USED

2D symbologies, like Data Matrix,

provide a consistent and reliable

means of labeling small objects. 11

THE ANATOMY OF A DATA MATRIX

QUIET ZONE MODULE

FINDER PATTERN

TIMING PATTERN

DATA REGION

12

DATA MATRIX BAR CODE GLOSSARY MODULES: Small square cells that make up the bar code symbol. Usually, dark modules

represent a digital 1 and light represent 0.

FINDER PATTERN: Two adjacent, solid borders are designated the finder pattern. These borders

are used by the scanner to locate and orient the symbol and to correct distortion.

TIMING PATTERN: Two opposite adjacent pair of borders are constructed with alternating dark

and light cells and are designated as the timing pattern. This component gives the scanner

information about the symbol’s size.

DATA REGION: The actual data and error correction information is divided into regions in the

symbol which contain a pattern of modules in a consistent array.

QUIET ZONE: A clear space around the symbol.

13

BENEFITS OF THE DATA MATRIX VERY EFFICIENT: Misread probability of 1/10.5 million (for the 3 of 9 symbol the probability

drops to 1/1.7 million).

SMALL: Almost 40X smaller than a 3 of 9 carrying the same data.

DEPENDABLE: Error correction capabilities (ECC200 method) allows accurate reads on symbols

with up to 60% damage.

FAXABLE: Data Matrix is also one of the few codes that are faxable. The outstanding capabilities

of ECC200 error correction allows even poorly resolved faxed images to be reliably scanned.

STORAGE CAPACITY: They are designed to encode up to 2335 alphanumeric characters,

though they have a recommended limit of 800 characters, actual best case is around 1200.

14

QR CODE The Quick Response or QR code is a trademarked two-dimensional

barcode first designed for the automotive industry in Japan in 1994

by Denso Wave, a Toyota subsidiary. Almost a decade ago, it was

introduced to enable high-speed component scanning during the

manufacturing process. 15

Since then QR codes have become ubiquitous, showing

up on product packaging, billboards and bumper

stickers, in magazines and just about any place where

a consumer with a smartphone is likely to seek more

information about any topic, item or idea.

16

HOW THEY ARE COMMONLY USED

THE ANATOMY OF A QR CODE

MODULES

FINDER PATTERN

TIMING PATTERN

ALIGNMENT PATTERN

ENCODING PORTION

17

QR CODE GLOSSARY MODULES: square modules arranged on a grid. These modules form the components of the

code. Within the code the modules fall into two categories: functional and encoding.

FUNCTIONAL MODULES: referring to those pieces that enable accessing the data

ENCODING MODULES: pieces used to store actual data

FINDER PATTERN: These are made up of alternating black and empty modules used to indicate

the position of the symbol’s internal components.

ALIGNMENT PATTERNS: looking much like smaller versions of the positional detection

indicators may occur in several places in the code depending on the code version.

ENCODING PORTION: consists of the information formatting areas and the data and error

correction space.

QUIET ZONE: A clear space around the symbol

18

Data is divided up into code blocks within the data

area, and each code block is sized so that it can

contain no more than 15 errors. This strategy

simplifies the algorithm, and interleaving the data in

the code blocks minimizes the possibility of an

unreadable code due to partial damage to symbol.

This also allows for some artistic license with adding

logos and other simple graphics to QR Codes.

HOW IT ALL WORKS

The key to the success of QR Codes lies in the

use of Reed-Solomon error correction.

QR Codes can contain four basic types of information:

numeric, alphanumeric, binary and Kanji.

19

The QR Code bridges the gap between

the physical and virtual worlds.

20

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Understanding Bar Codes