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Bar Codes 101

Get eBook: Barcoding 101
What are the benefits of using a Bar Code?
What is a Bar Code?
Elements of a Bar Code
Bar Code Symbology Types
Bar Code Symbologies
Applications for Bar Codes
How to obtain your own UPC # for your product
Industry Standard Organizations
Do you have a bar code question?

What are the benefits of using a Bar Code?

Barcodes provide faster and more accurate recording of information which:

  • Saves time
  • Reduces errors
  • Reduces costs

What is a Bar Code?

A bar code is a binary coding system consisting of varying widths of vertical black lines (called bars) and white spaces that when read by an optical scanner can be converted into machine language. Bars and spaces are just one of many "elements" that make up a bar code.

Elements of a Bar Code

Almost all bar codes contain the following elements:

Start and Stop Symbologies

At the beginning and end of some bar code symbols, there are "start" and "stop" characters. These characters identify the symbology and also enable the scanner to read the symbol bidirectionally, decoding the data in the correct order.   Bar codes also often include a check digit at the end that is determined according to an algorithm based upon the preceding characters.

start stop
Quiet Zones

In order for the scanner to recognize the bar code, there must be an 1/4" wide area next to the start and stop characters that contains no markings.  If the space is too short, the bar code symbol will not be read by the scanning device.

quiet zones


Interpretation Line

This is a line of human-readable characters that is located usually beneath the bar code.  An example is shown in the Code 128.

Code 128


Bar/Space Patterns

These are the wide and narrow black bars and whites spaces contained in the bar code.

bars and spaces


Inter-Character Gap

In some bar codes, like Code 39 (same as Code 3 of 9), each character is printed independently of other characters and is not part of the encoded character and is thus separated by what's called an inter-character gap.

Code 39 When exaggerated, you can see the elements for each character and the inter-gap that separates the characters. intergap


Code Density

Code density refers to the number of data or message characters which can be represented per unit length of space.   Four variables affect code density:  type of code, ratio of wide to narrow elements and the X dimension.

  • Type of Code

    UPC bar codes are used in the U.S. and Canada EAN and JAN symbols are used in Europe and Japan respectively.  All bar codes have different structures.  Some are able to encode more information per inch than others.  An example is shown in comparing the Interleaved 2of5 bar code with Code 3 of 9.  The Interleaved 2of5 can encode more numeric information than the Code 3 of 9 in the same amount of space.

    Code 39 and Interleave 2of5 comparison


  • Ratio of Wide to Narrow Elements

    Ratio is important in deciding on the type of scanning device to read the code.  Changing the code density of a particular bar code is accomplished by varying the ratio.

    bar code ratio


  • X Dimension

    The width of the narrowest bar or space is referred to as the X dimension, usually given in mils (thousandths of an inch). The X dimension dictates the width of all other bars and spaces, and ultimately the length of the bar code. The greater the X dimension, the more easily a bar code will scan. The smaller the width of the bar, the shorter the length of the symbol, the closer the tolerances are and the more difficult it is to print.  The larger the width of the elements, the more space it takes to print the bar code; therefore, the lower the bar code density.  The thinner the bar and spaces, the less space is required and the higher the bar code density.  Lower density bar codes are more reliably printed and more consistently read than higher density bar codes.

    bar code density

How is a bar code read?

When a bar code scanner is passed over the bar code, the light source from the scanner is absorbed by the dark bars and not reflected, but it is reflected by the light spaces. A photocell detector in the scanner receives the reflected light and converts the light into an electrical signal.

As the wand is passed over the bar code, the scanner creates a low electrical signal for the spaces (reflected light) and a high electrical signal for the bars (nothing is reflected); the duration of the electrical signal determines wide vs. narrow elements. This signal can be "decoded" by the bar code reader's decoder into the characters that the bar code represents. The decoded data is then passed to the computer in a traditional data format.

Bar Code Symbology Types

Some bar codes are numeric only (such as UPC, Interleaved 2of5, and EAN).  Others have a fixed length (i.e., UPC-A is 12 digits, UPC-E is 6 digits, EAN-13 is 13 digits and EAN-8 is 8 digits).  Some bar codes also have both numbers and alphabetic characters (i.e., Code 128, Code 39 and Code 93).  Code 128 enables you to encode all 128 characters.

Bar codes are also grouped into two types of symbologies:  linear or two-dimensional.

A linear (or one-dimensional or 1D) symbology bar code is made up of one single row of various widths and lengths of predefined black bars and white spaces. Ordinary bar codes are "vertically redundant,", meaning that the same information is repeated vertically. It is in fact a one-dimensional code. The heights of the bars can be truncated without any lose of information. However, the vertical redundancy allows a symbol with printing defects, such as spots or voids, to still be read. The higher the bar heights, the more probability that at least one path along the bar code will be readable. The height of the bars can be truncated without any lose of information. Examples of one-dimensional bar codes are shown below as Codabar, Code 39, and Interleave 2of5.

The most common 1D symbologies are Code 39, pioneered by the defense and automotive industries; the Universal Product Code (U.P.C.), first employed by the supermarket industry in 1973; Codabar, used early on by blood banks, Interleaved 2-of-5 (ITF), Code 128. Another is Code 93.

The need for ever increasing amounts of information in smaller spaces has lead to more compact and higher density symbologies found in two-dimensional or stacked symbologies.  A two-dimensional bar code is laid out as either a "stacked matrix"  or "multi-rowed" bar code.  Two dimensionalal bar codes store more information than linear barcodes and can be displayed in a smaller amount of space.

The first application for such symbols was unit-dose packages in the healthcare industry. These packages were small and had little room to place a bar code. The electronics industry also showed an early interest in very high density bar codes, and two-dimensional symbologies since free space on electronics assemblies was scarce.

More recently, the ability to encode a portable database has made two-dimensional symbologies attractive in applications where space is not at a premium. One example is storing name, address, and demographic information on direct mail business reply cards.

For examples of 2D symbologies, refer to the PDF417 bar code symbology listed below.

Matrix symbologies include: Datamatrix, Maxicode, Dot Code A, Code One, QR Code, and Aztec Code.

Multi-rowed symbologies include PDF417, Code 16K, Code 49, Codablock F, MicroPDF417 and SuperCode.

    Linear Symbologies Two-Dimensional Symbologies


Bar Code Symbologies

The following is a list of the most popular bar code symbologies in use today:


(also known as USD-4, NW-7, and 2 of 7 code) is used in libraries, blood banks, the overnight package delivery industry, and a variety of other information processing applications.

Code 39 bar code

Code 39
(also known as LOGMARS, Code 3 of 9 and the 3 of 9 Code) is an alpha-numeric barcode and is one of the most popular bar codes used in a variety of industries. Each Code 39 character is constructed of five bars and four spaces, for a total of nine elements. Three of these are always wider than the rest. LOGMARS (Logistics Applications of Automated Marking and Reading Symbols) is an application of Code 39 used by the United States Department of Defense.

Code 16K bar code

Code 16K
A multi row symbology, Code 16K offers high information density encoding of the full (128-character) ASCII set and double density encoding of numeric data strings

Code 128 bar code

Code 128
Code 128 is a very compact and versatile language which allows the encodation of the entire 128 ASCII character set. This symbology is self-checking and is designed with geometric features to improve scanner read performance.

Datamatrix bar code

Data Matrix is a 2-D matrix code designed for putting a lot of information in a very small space and can store between one and 500 characters. The symbol is also scalable between a 1-mil square to a 14-inch square. That means that a Data Matrix symbol has a maximum theoretical density of 500 million characters to the inch! The practical density will be limited by the resolution of the printing and reading technology used. Symbols between one-eight inch square to seven inches square can be read at distances ranging from contact to 36 inches away. Typical reading rates are 5 symbols per second.

The most popular applications for Datamatrix is the marking of small items such as integrated circuits and printed circuit boards.  The code is read by CCD video camera or CCD scanner.

EAN bar code

There are two different versions of EAN bar codes, EAN 8 and EAN 13, which can encode 8 and 13 digit numbers. All other countries aside from the United States utilize the EAN bar code for identification on retail goods. The symbol is identical to the UPC-A with one exception, the EAN bar code represents thirteen numeric characters instead of twelve.

Interleaved 2of5

Interleaved 2of5
is a numeric-only high density symbology that is very compact because information is encoded in both the bars and spaces. Only an even number of numeric data can be encoded within this symbol. This "double density" symbol encodes odd positioned data in the bars, and even positioned data in the spaces. Interleaved 2 of 5 bar codes are used on corrugated boxes, in the shipping industry, and in laboratories.

MSI Plessey

MSI Plessey
was designed in the 1970s by the Plessey Company in England and has been used primarily in libraries and retail applications.

Maxicode bar code

is a two-dimensional matrix symbology containing a fixed number of dark and light hexagonal modules. The symbol is specified to be a fixed size. MaxiCode has a bulls eye finder pattern in the center of the symbol. A two-dimensional device such as a CCD camera is necessary to scan the symbology. MaxiCode is designed with two selectable levels of error correction capability. It supports industry standard escape sequences to define international code pages and special encodation schemes. MaxiCode is used by the United Parcel Service to encode address and customer specified data on shipping packages which are scanned on high-speed conveyors.

PDF417 Bar code

is a two-dimensional bar code consists of a stack of vertically aligned rows with a minimum of 3 rows (maximum 90 rows). Each row includes a minimum of 1 symbol character (maximum 30 symbol characters), excluding start, stop and row indicator columns. A PDF417 symbol may contain up to 928 symbol characters or codewords. It is used whenever a large amount of information is required in a small space. The Gettysburg address can be put into a 1" x 1" PDF417 square.

POSTNET bar code

(POSTal Numeric Encoding Technique) bar code was developed by the US Post Office to encode zip code information. POSTNET bar codes printed on US mail improve the speed, accuracy and delivery of mail. Some US Post Offices even offer a discount for sending bulk mail when the POSTNET bar code is used.

UPC Codes
The Universal Product Code (UPC) was the first bar code symbology widely adopted. Its birth is usually set at April 3, 1973, when the grocery industry formally established UPC as the standard bar code symbology for product marking. Foreign interest in UPC led to the adoption of the EAN code format, similar to UPC, in December 1976.


There are now five versions of UPC and two versions of EAN. The Japanese Article Numbering (JAN) code has a single version identical to one of the EAN versions with the flag characters set to "49".


A variation of the Code 128 symbology was designed primarily for product/shipment identification applications. The UCC/EAN-128 specification uses the same code set as Code 128, however a special character (function 1) is used as part of the start code in the symbol. In addition, UCC/EAN-128 symbols utilize standardized application identifiers (AI’s). By 2005 all US retailers will have to be able to scan all EAN/UCC article numbers (8, 12, 13 and 14-digit).

Applications for Bar Codes

Bar codes are used in any applications where data needs to be automatically identified and captured efficiently and accurately in real-time for purposes of:

  • inventory control
  • asset tracking
  • product identification
  • patient information
  • warehouse picking and packing
  • and more…

Bar codes are used in many industries such as:

  • Healthcare
  • Packaging
  • Transport
  • Retail
  • apparel and textiles
  • automotive
  • government and defense,
  • and more…


How to obtain a UPC # for your product

Your company will need to obtain its own UPC number, called a UCC-12. This will identify your company. The UPC-A bar code symbol represents your UCC-12 (UPC) number.

  • The left half of a UPC code is called the UCC Company Prefix acts as your unique company number.
  • The right half of a UPC code is the product ID number assigned by your company.
  • Your company can obtain its own UPC # by contacting the GS1

Industry Standard Organizations

Standards for many industries are defined by Industry Standard Organizations. Some of the major organizations obtaining bar codes application, label and product standards are identified in the next section. The following industry standard organizations are a resource for AIDC application or industry standards.


Industry volunteers from automotive OEMs, parts suppliers and technology vendors all work together at AIAG on achieving consensus on common automotive industry rules for using bar codes, and two dimensional symbols, and other Automatic Identification technologies in applications such as shipping labels and parts identification/marking.


The American National Standards Institute facilitates development of American National Standards by establishing consensus among qualified groups.

EAN Intl

EAN International was started in 1974 when manufacturers and distributors of 12 European countries formed an ad-hoc council. Its brief was to examine the possibility of developing an uniform and standard numbering system for Europe, similar to the UPC system already in operation in the USA. As a result , a UPC compatible system called "European Article Numbering" was created.

GS1 Administers UPS Barcodes

The GS1 administers U.P.C. (Universal Product Code) bar codes. GS1 has Member Organisations in over 100 countries globally. Our Member Organisations handle all enquiries related to GS1 products, solutions and services. Contact GS1 for more information.


The Health Industry Business Communications sets the standards for the health industry.

Japan Auto Parts Industries Association

Japan Automobile Manufacturers Association, or JAMA, is a trade association with its headquarters in Tokyo, Japan. It was founded in April 1967  to promote the sound development of the automobile manufacturing industry, to contribute to social and economic welfare through research, information exchange, public service and international cooperation activities and to serve as a platform for the automakers of Japan to share technological developments and management practices.  There are currently 14 member companies, manufacturing not only cars, but trucks and motorcycles as well. The organization also deals with the manufacturing and distribution of vehicle parts around the world.


The Japanese Standards Association is responsible for establishing JAN (Japanese Article Numbering system) bar code standards.

Japan Autombile Manufacturers Association

The Japan Auto Parts Industries Association, or JAPIA, was established in August 1969 on the foundations of a predecessor organization created in 1938. Its chief aims are to promote the sound development of the auto parts manufacturing industry and contribute to social and economic welfare.  JAPIA members are helping to support the automobile industry on a global basis.

Organization for Data Exchange

The Organization for Data Exchange by Tele Transmission in Europe, Odette, is a non-profit making organization run by automotive people for automotive people. "Our mission in the global automotive industry, is to develop tools and recommendations that improve the flow of goods, services, product data and business information across the whole supply chain, throughout the entire product life-cycle."  The principal areas of activity are E-Business Communications and Supply Chain Management.

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