Bar Code Symbologies

Bar codes are like a printed version of the Morse code. Different bar and space patterns are used to represent different characters. Sets of these patterns are grouped together to form a “symbology”. There are many types of bar code symbologies each having their own special characteristics and features. Most symbologies were designed to meet the needs of a specific application or industry. For example the UPC symbology was designed for identifying retail and grocery items and PostNET was designed to encode Zip Codes for the US Postal Service.

The following is a detailed description of the most commonly used bar code symbologies. All of the following types of bar codes are fully supported by B-Coder Pro, the TAL Bar Code ActiveX control and the TAL Bar Code DLLs.

  CODE 39 (Normal and Full ASCII versions)

The Normal CODE 39 is a variable length symbology that can encode the following 44 characters: 1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ-. *$/+%. Code 39 is the most popular symbology in the non retail world and is used extensively in manufacturing, military, and health applications. Each Code 39 bar code is framed by a start/stop character represented by an asterisk (*). The Asterisk is reserved for this purpose and may not be used in the body of a message. B-Coder automatically adds the start and stop character to each bar code therefore you should not include them as part of your bar code message. If you select the NORMAL version of CODE 39 and your bar code text contains lower case characters, B-Coder will convert them to upper case. If your bar code message contains any invalid characters, B-Coder will prompt you with a warning message (if the Enable Invalid Warning Messages option is selected in the Preferences menu).

Code 39 optionally allows for a (modulo 43) check character in cases where data security is important. The health care industry has adopted the use of this check character for health care applications.

Another feature of Code 39 allows for concatenation of two or more bar codes. It is sometimes advantageous to break long messages into multiple, shorter, symbols. If the first data character of a Code 39 symbol is a space, some readers will store the remainder of the symbol in a buffer and not transmit the data. This operation continues for all successive Code 39 symbols with a leading space, with each message appended to the previous one.

When a message without a leading space is read, it is appended to the previously scanned data in the buffer and the entire buffer is transmitted as one long message.

The FULL ASCII version of Code 39 is a modification of the NORMAL (standard) version that can encode the complete 128 ASCII character set (including asterisks). The Full ASCII version is implemented by using the four characters: $/+%. as shift characters to change the meanings of the rest of the characters in the Normal Code 39 character set. Because the Full ASCII version uses shift characters in combination with other standard characters to represent data not in the Normal Code 39 character set, each non-standard character requires twice the width of a standard character in a printed symbol.

Note: Because all of the characters used to implement Full ASCII Code 39 are part of the Normal Code 39 character set, readers that do not support Full ASCII Code 39 will still read Full ASCII Code 39 symbols. The reader will output shifted characters as if they were normal Code 39 characters.

  UPC-A, UPC-E, and UPC Supplementals

UPC-A with Supplemental UPC-E

UPC-A is a 12 digit, numeric symbology used in retail applications. UPC-A symbols consist of 11 data digits and one check digit. The first digit is a number system digit that normally represents the type of product being identified. The following 5 digits are a manufacturers code and the next 5 digits are used to identify a specific product.

UPC numbers are assigned to specific products and manufacturers by the Uniform Code Council (UCC). To apply for a UPC number or for more information, you can contact the UCC at 8163 Old Yankee Road, Suite J, Dayton, OH 45458 Tel: 937-435-3870

When specifying UPC-A messages, you normally specify 11 digits and let your bar code printing software calculate the 12th check digit for you. (All TAL bar code software products automatically calculate check digits for you.)

UPC-E is a smaller seven digit UPC symbology for number system 0. It is often used for small retail items. For UPC-E bar codes, you normally specify 6 digits and let your bar code printing software calculate the seventh check digit for you.

Both UPC-A and UPC-E allow for a supplemental two or five digit number to be appended to the main bar code symbol. This supplemental message was designed for use on publications and periodicals. If you enter a supplemental message, it must consist of either two or five numeric digits. The supplemental is simply a small additional bar code that is added onto the right side of a standard UPC symbol.

Differences between Type A and Type E

UPC-E is also called “zero suppressed UPC” because UPC-E compresses a normal 12 digit UPC-A number into a six digit code by “suppressing” the number system digit, trailing zeros in the manufacturers code and leading zeros in the product identification part of the bar code message. A seventh check digit is encoded into a parity pattern for the six main digits. UPC-E can thus be uncompressed back into a standard UPC-A 12 digit number.

Note: Most bar code readers can be configured to automatically convert 6 digit UPC-E numbers to 12 digit UPC-A numbers before they are transmitted to a host computer.

The main difference between a UPC-A symbol and a UPC-E symbol is the size.  Below is a UPC-A bar code on the left and the same data encoded as a UPC-E symbol on the right.


These two bar codes are equivalent.


Converting between UPC-E and UPC-A

To convert UPC-E bar code numbers to UPC-A (or vice Versa) you can use our useful online converter program below.

UPC-E Data 

UPC-A Data   
Check digit  

Download Source Code: [Visual Basic]|[JavaScript]

Converting UPC-A to UPC-E

In the following, the number 0 and each of the letters a,b,c,d and e represent individual digits in the bar code message and the letter X represents the UPC check digit. All TAL Bar code software products can make the conversion for you, so you do not have to think about it.

UPC-A Number

Equivalent UPC-E




Manufacturer code must have 2 leading digits with 3 trailing zeros and the item number is limited to 3 digits (000 to 999).



Manufacturer code must have 3 leading digits ending with “1” and 2 trailing zeros. The item number is limited to 3 digits.



Manufacturer code must have 3 leading digits ending with “2” and 2 trailing zeros. The item number is limited to 3 digits.



Manufacturer code must have 3 leading digits and 2 trailing zeros. The item number is limited to 2 digits (00 to 99).



Manufacturer code must have 4 leading digits with 1 trailing zero and the item number is limited to 1 digit (0 to9).



Manufacturer code has all 5 digits.
The item number is limited to a single digit consisting of either 5,6,7,8 or 9.


  EAN-8 / EAN-13, BookLan and EAN Supplementals

EAN-8 EAN-13 with supplemental (ISBN Version)

EAN or European Article Numbering system (also called JAN in Japan) is a European version of UPC. It uses the same size requirements and a similar encoding scheme as for UPC codes.

EAN-8 encodes 8 numeric digits consisting of two country code digits, five data digits and one check digit. B-Coder will accept up to 7 numeric digits for EAN-8. B-Coder will automatically calculate the check digit for you. If you enter less than 7 digits or if you enter any digits other than 0 to 9, B-Coder will display a warning message. If the option “Enable Invalid Message Warnings” in the Preferences menu is not selected and you do not enter 7 digits, B-Coder will left pad short messages with zeros and truncate longer messages so that the total length is 7.

EAN-13 is the Euro version of UPC-A. The difference between EAN-13 and UPC-A is that EAN-13 encodes a 13th digit into the parity pattern of the left six digits of a UPC-A symbol. This 13th digit, combined with the 12th digit, usually represent a country code.

Both EAN-8 and EAN-13 support a supplemental two or five digit number to be appended to the main bar code symbol. The supplemental is designed for use on publications and periodicals. Supplemental messages must consist of either two or five numeric digits and will appear as a small additional bar code on the right side of a standard EAN symbol.

EAN bar code numbers are assigned to specific products and manufacturers by an organization called ICOF located in Brussels, Belgium. Tel: 011-32-2218-7674

EAN-13 has been adopted as the standard in the publishing industry for encoding ISBN numbers on books. An ISBN or BookLand bar code is simply an EAN-13 symbol consisting of the first 9 digits of the ISBN number preceded by the digits 978. The supplemental in an ISBN bar code is the retail price of the book preceded by the digit 5. For example, if your ISBN number is 1-56276-008-4 and the price of the book is $29.95 then you would enter 978156276008 as the bar code message and 52995 for the supplemental.



RSS was developed by the Uniform Code Council, Inc. to answer business needs of its 200,000 member companies in North America. The purpose of the code is to increase the amount of information that can be put into a bar code while decreasing the overall area of the code. The code will allow businesses to improve the stream of information and to match that information to the actual flow of product. This type of code is particularly useful for applications where space limitations are a concern. Industries such as pharmaceutical, healthcare, logistics and transportation, and supermarkets have recently begun utilizing this new symbology. RSS allows businesses to go beyond the typical manufacturer and product identification information embedded in a bar code. The healthcare industry views this symbology as a potential way to significantly reduce medication errors. The RSS technology also improves the labeling and tracking of food items. It gives supermarkets the opportunity to improve their labeling and tracking of meat and produce items. The code can be encoded to include manufacturers name, item identification number, weight, extended price, and the ability to place best if used by dates on items. Consumers also benefit by added consumer safety. If a bad batch of produce is placed on the shelves, a supermarket will have the ability to track down the produce immediately and remove it from the shelves.

More information on RSS 14 from the Uniform Code Council.



CodaBar is a variable length symbology that allows encoding of the following 20 characters: 0123456789-$:/.+ABCD. CodaBar is commonly used in libraries, blood banks, and the air parcel business. CodaBar uses the characters A B C and D only as start and stop characters. Thus, the first and last digits of a CodaBar message must be A B C or D and the body of the message should not contain these characters. B-Coder will allow any length of CodaBar message as long as it contains valid characters and starts and ends with a valid start/stop character. If you use lower case letters for A B C or D, B-Coder will convert to upper case.



Interleaved 2 of 5 is a high density variable length numeric only symbology that encodes digit pairs in an interleaved manner. The odd position digits are encoded in the bars and the even position digits are encoded in the spaces. Because of this, I 2 of 5 bar codes must consist of an even number of digits. Also, because partial scans of I 2 of 5 bar codes have a slight chance of being decoded as a valid (but shorter) bar code, readers are usually set to read a fixed (even) number of digits when reading I 2 of 5 symbols. The number of digits are usually pre-defined for a particular application and all readers used in the application are programmed to only accept I 2 of 5 bar codes of the chosen length. Shorter data can be left padded with zeros to fit the proper length.

Interleaved 2 of 5 optionally allows for a weighted modulo 10 check character for special situations where data security is important.



Discrete 2 of 5 is a variable length numeric symbology very similar to Interleaved 2 of 5 except that instead of encoding data in both the bars and the spaces, data is only encoded in the bars. Because of this, discrete 2 of 5 is not as compact as Interleaved 2 of 5 and also, odd numbers of digits may be encoded. Use of Discrete 2 of 5 is not very common and few bar code readers support this symbology.

  CODE 93

CODE 93 is a variable length symbology that can encode the complete 128 ASCII character set. Code 93 was developed as an enhancement to the CODE 39 symbology by providing a slightly higher character density than CODE 39. CODE 93 also incorporates two check digits as an added measure of security. Although CODE 93 is considered more robust than CODE 39, it has never achieved the same popularity as Code 39. CODE 93 bar codes are framed by a special start/stop character. B-Coder will automatically add the start and stop characters as well as the check digits to each Code 93 bar code therefore you should not attempt to include them as part of your bar code message.

  CODE 128


Code 128 is a variable length, high density, alphanumeric symbology. Code 128 has 106 different bar and space patterns and each pattern can have one of three different meanings, depending on which of three different character sets is employed. Special start characters tell the reader which of the character sets is initially being used and three special shift codes permit changing character sets inside a symbol. One character sets encodes all upper case and ASCII control characters, another encodes all upper and lower case characters and the third set encodes numeric digit pairs 00 through 99. This third character set effectively doubles the code density when printing numeric data. Code 128 also employs a check digit for data security. In addition to ASCII characters, Code 128 also allows encoding of four special function codes (FNC1 – FNC4). The meaning of function code FNC1 and FNC4 were originally left open for application specific purposes. Recently an agreement was made by the Automatic Identification Manufacturers Assoc. (AIM) and the European Article Numbering Assoc. (EAN) to reserve FNC1 for use in EAN applications. FNC4 remains available for use in closed system applications. FNC2 is used to instruct a bar code reader to concatenate the message in a bar code symbol with the message in the next symbol. FNC3 is used to instruct a bar code reader to perform a reset. When FNC3 is encoded anywhere in a symbol, any data also contained in the symbol is discarded.

Note: All TALtech bar code software products will automatically select the proper character sets and insert the necessary start character and shift codes so that the resulting bar code will be as short as possible. The check digit will also be calculated automatically.

  EAN/UCC 128

The EAN/UCC 128 symbology is a variation of the original Code 128 symbology designed primarily for use in product identification applications. The EAN/UCC 128 specification uses the same code set as Code 128 except that it does not allow function codes FNC2-FNC4 to be used in a symbol and FNC1 is used as part of the start code in the symbol. The check digit in EAN/UCC128 symbols is also calculated slightly differently than in Code 128.


POSTNET (POSTal Numeric Encoding Technique) is a 5, 9 or 11 digit numeric only bar code symbology used by the U.S. Postal Service to encode ZIP Code information for automatic mail sorting by zip code. The bar code may represent a five digit ZIP Code (32 bars), a nine digit ZIP + 4 code (52 bars) or an eleven digit Delivery Point code (62 bars).

POSTNET is unlike other bar codes because data is encoded in the height of the bars instead of in the widths of the bars and spaces. Most standard bar code readers cannot decode POSTNET. This symbology was chosen by the Postal Service mainly because it is extremely easy to print on almost any type of printer. POSTNET is a fixed dimension symbology meaning that the height, width and spacing of all bars must fit within exact tolerances.

Microsoft Access and Word have built in tools for generating PostNet bar codes. See our tutorial on how to use the tools in word to created PostNet bar codes in your mail merge documents.

Postal FIM Patterns

FIM or Facing Identification Mark patterns are another type of postal bar code used in automated mail processing by the U.S. Postal Service. FIM patterns are used for automatic facing and canceling of mail that does not contain a stamp or meter imprint (business reply mail, penalty mail, etc.). They also provide a means of separating business and courtesy reply mail from other letters. Three FIM patterns are currently in use. FIM-A is used on courtesy reply mail that has been preprinted with PostNET bar codes. FIM-B is used on business reply, penalty and franked (government) mail that is not preprinted with PostNET bar codes. FIM-C is used on business reply, penalty and franked mail that has been preprinted with PostNET bar codes. FIM patterns are placed in the upper right corner along the top edge and two inches in from the right edge of letters and cards. For more information about all postal bar codes contact your local post office.

  BPO 4 State Code (British Post Office, Royal Mail Code)

BPO (British Post Office) 4 State Code is a new postal bar code symbology that has been developed by the British Post office for encoding European postcode data similar to the way the U.S. PostNET symbology is used for encoding Zip Code data. At the time of this writing, the BPO 4 State Code has not been officially adopted as the standard for European postal applications however it is anticipated that it will be sanctioned sometime in 1995. The goal of BPO 4 State Code is to provide European countries with a simple and efficient postal bar coding scheme.

The U.S. PostNET symbology encodes numeric characters in a pattern of four bars per character with each bar being either tall or short (i.e. two possible “states” for each bar). The U.S. technique thus allows for up to 16 different possible bar patterns for each set of four bars and is adequate for encoding the ten digits zero through nine. Because European postcodes contain both alpha and numeric characters, (thus requiring a minimum of 36 different possible patterns for the characters A-Z and 0 to 9), each character in the BPO 4 State Code is encoded into four bars with each bar having four possible “states”. The four states are: tall bars, short bars, medium height bars extended up from the middle of the symbol and medium height bars extended down from the middle of the symbol. In theory,the BPO 4 State Code is capable of encoding up to 128 different characters however only the characters A through Z and 0 to 9 have been assigned unique bar patterns.

BPO 4 State Code is a fixed dimension symbology meaning that the height, width and spacing of all bars must fit within exact tolerances.


PDF417 is a high density 2 dimensional bar code symbology that essentially consists of a stacked set of smaller bar codes. The symbology is capable of encoding the entire (255 character) ASCII set. PDF stands for “Portable Data File” because it can encode as many as 2725 data characters in a single bar code. The complete specification for PDF417 provides many encoding options including data compaction options, error detection and correction options, and variable size and aspect ratio symbols. The symbology was published by Symbol Technologies, Inc. to fulfill the need for higher density bar codes. The low level structure of a PDF417 symbol consists of an array of code words (small bar and space patterns) that are grouped together and stacked on top of each other to produce the complete printed symbol. An individual code word consists of a bar and space pattern 17 modules wide. The user may specify the module width, the module height, and the overall aspect ratio (overall height to width ratio) for the complete symbol. A complete PDF417 symbol consists of at least 3 rows of up to 30 code words and may contain up to 90 code word rows per symbol with a maximum of 928 code words per symbol.

The code words in a PDF417 symbol are generated using one of three data compaction modes currently defined in the symbology specifications. This allows more than one character to be encoded into a single data code word. Because different data compaction algorithms may be used, it is possible for different printed symbols to be created from the same input data. The symbology also allows for varying degrees of data security or error correction and detection. Nine different error correction levels are available with each higher level adding additional overhead to the printed symbol.


Data Matrix is a high density 2 dimensional matrix style bar code symbology that can encode up to 3116 characters from the entire 256 byte ASCII character set. The symbol is built on a square grid arranged with a finder pattern around the perimeter of the bar code symbol.

There are two types of Data Matrix symbols each using a different error checking and correction scheme (ECC). The different types of Data Matrix symbols are identified using the terminology “ECC” followed by a number representing the type of error correction that is used by the encoding software. ECC 000 to ECC 140 are the original type of Data Matrix symbols and are now considered obsolete. The newest version of Data Matrix is called ECC 200 and is recommended for all new Data Matrix applications. The ECC 200 version of Data Matrix uses a much more efficient algorithm for encoding data in a symbol as well as an advanced error checking and correction scheme.


MaxiCode is a fixed size matrix style symbology which is made up of offset rows of hexagonal modules arranged around a unique bulls-eye finder pattern. Each MaxiCode symbol has 884 hexagonal modules arranged in 33 rows with each row containing up to 30 modules. The maximum data capacity for a MaxiCode symbol is 93 Alphanumeric characters or 138 Numeric characters. The symbology was designed by United Parcel Service for package tracking applications. The design of the MaxiCode symbology was chosen because it is well suited to high speed, orientation independent scanning. Although the capacity of a MaxiCode symbol is not as high as other matrix style bar code symbologies, it was primarily designed to encode address data which rarely requires more than about 80 characters. MaxiCode symbols actually encode two separate messages – a Primary message and a Secondary message. The Primary message normally encodes a postal code, a 3 digit country code and a 3 digit class of service number. The Secondary message normally encodes address data and any other required information.


Aztec Code is a high density 2 dimensional matrix style bar code symbology that can encode up to 3750 characters from the entire 256 byte ASCII character set. The symbol is built on a square grid with a bullseye pattern at its center. Data is encoded in a series of “layers” that circle around the bullseye pattern. Each additional layer completely surrounds the previous layer thus causing the symbol to grow in size as more data is encoded yet the symbol remains square. Aztec’s primary features include: a wide range of sizes allowing both small and large messages to be encoded, orientation independent scanning and a user selectable error correction mechanism.

The smallest element in an Aztec symbol is called a “module” (i.e. a square dot). The module size and the amount of error correction are the only “dimensions” that can be specified for an Aztec symbol and both are user selectable. It is recommended that the module size should range between 15 to 30 mils in order to be readable by most of the scanners that are currently available.

The overall size of an Aztec symbol is dependent on the module size, the total amount of encoded data and also on the level of error correction capacity chosen by the user. The smallest Aztec symbol is 15 modules square and can encode up to 14 digits with 40% error correction. The largest symbol is 151 modules square and can encode 3000 characters or 3750 numeric digits with 25% error correction.


MSI-PLESSEY is a variable length, numeric only, symbology. The symbology is one of the earliest bar code symbologies ever developed and is based on a four bit binary number scheme. Each symbol is framed by a start and a stop pattern and contains a check character that is calculated from the values of each of the encoded data digits. MSI-Plessey is rarely used in anything other than grocery store shelf marking applications. In fact most modern bar code readers do not provide support for reading MSI-Plessey symbols.

  Accuracy of Different Symbologies – How Accurate is Accurate?

It’s commonly known that the best-trained data entry operator will make a keystroke entry error once every 300 keystrokes. Each of these keystroke errors represents and error in your decision-making data. This leads to wasted time, misappropriated capital and ultimately, lost revenues. It is for this reason that most companies make the decision to adopt AIDC technologies.

In studies conducted by the University of Ohio, common bar code symbologies were tested to determine real life accuracy. The worst bar code for data accuracy in the test proved to be one of the most common – the UPC. The UPC had a worst-case error rate of 1 error in 394K characters. The best-tested symbologies were the DataMatrix and PDF417, with a worst case error rate of 1 error in 10.5M characters. All the results from the University of Ohio study are listed below.

Source: Lincoln’s Log Vol 1-00


Worst Case

Best Case

DataMatrix 1 error in 10.5M 1 error in 612.9M
PDF417 1 error in 10.5M 1 error in 612.4M
Code 128 1 error in 2.8M 1 error in 37M
Code 39 1 error in 1.7M 1 error in 4.5M
UPC 1 error in 394K 1 error in 800K

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