Overview  |  Anatomy of a Bar Code  |  Bar Code Symbologies
How to read a Bar Code  |  Terms & Abbreviations

A bar code symbology is a system for representing data in the bars and spaces of a bar code. A bar code consists of a number of printed bars and intervening spaces. The width of the bars and spaces, as well as the number of each, is determined by the specification for that symbology.

The process to convert a computer message into a bar code symbol is a four-step process:

• Establish the type of data to be represented and the number of characters in the message.

• Translate the human-readable information into binary format. The number and value of the binary zeros and ones are determined by the bar code symbology selected.

• Create the bar/space pattern that represents the binary word used in step 2.

• Format the individual bar code characters into a symbol that represents the complete message. The complete symbol consists of quiet zones, start and stop character patterns, data characters, and optional check digit characters.

The most widely used symbologies are discussed and illustrated in the following pages.

Code 39 was the first alphanumeric symbology to be developed. In 1981 it was established as the official Department of Defense and the official government symbology standard. The Automotive Industry Action Group and the Health Industry Business Communications Council recommend Code 39 symbology. Also known as Code 3 of 9, it is the code for industrial, medical, electronics, telecommunications, corrugated shipping containers, commercial and government applications. Numbers, letters, symbols, and some punctuation can be encoded in Code 39 bar codes.

• Capital letters A to Z

• Numbers 0 to 9

• Space character

• -. $ / + % characters.

The name, Code 39, signifies each character is composed of nine elements--five bars and four spaces. Each character has three wide elements and six narrow, each separated by an intercharacter gap. The intercharacter gap contains no information and should be approximately the same size as the narrow element width.

 For a decoder to distinguish between the wide and narrow elements, a minimum wide to narrow ratio needs to be established. Depending on the resolution used for printing the bar code, the width of the wide element should be at least two times greater than the narrow element. The width of a narrow bar should be the same as a narrow space; and, the width of a wide bar should be the same as a wide space.

Code 39 is self-checking, discrete, and utilizes start/stop characters, intercharacter gaps and allows bi-directional scanning. Both the start and stop character for this symbology is an asterisk (*). Together, the wide elements (represented by "1") and narrow elements (represented by "0") create a pattern that is used to obtain its equivalent numeric value.

Full ASCII Code 39

The Full ASCII Code 39 expands standard Code 39 to include the full 128 ASCII character set using the existing Code 39 character set. This is achieved for certain ASCII characters by pairing two Code 39 characters to represent the single ASCII character.

As shown in the example, a carriage return (CR, ASCII 13) is encoded using the two Code 39 characters, $ and M.

Because Full ASCII Code 39 is derived using standard Code 39 characters, your bar code reader must be configured for Full ASCII Code 39 to properly decode the Full ASCII Code 39 character set.

UPC

Since 1973, the Universal Product Code (UPC) has been identified with various types of retail industry. However, it can be used in shipping and retail applications. UPC is a coding system as well as a symbology; it is designed to identify a product and its manufacturer. The Universal Product Code Council assigns all UPC codes. The number system character, as shown below, indicates the type of product the bar code is identifying.

UPC is a fixed length, numeric, continuous symbology consisting of two halves which can be read independently. Encodation differs for the left and right halves. Parity refers to whether the sum of the bar module widths in a given character is an even or odd number. The check digit is the last digit and is calculated from all of the other numbers encoded in the bar code.

There are four versions of UPC bar code. Two most commonly used types of UPC are Version A, which encodes twelve digits and Version E, which encodes six digits. However, the encodations of all versions are basically the same; the difference is primarily the configuration of the data field.

UPC Version A

UPC Version A is a numeric, fixed length, continuous bar code. Commonly used for grocery, drug or health-related items, UPC Version A encodes twelve digits; six digits in each half with left, center and right guard bars. Guard bars are usually printed with greater length than other bars in the symbol to maximize the allowable scanning tilt angle and to divide the symbol in half.

Each half is referred to as left parity and right parity and can be decoded separately. Bars and spaces can be one, two, three or four modules wide. Version A has two levels of checking; the first is a parity check of individual characters within the first half; the second is a modulus 10 check digit. The encodation patterns for UPC Version A are different for the left and right parities.

UPC Version E

UPC Version E is a zero-suppressed version of UPC A used on items often too small to include a bar code. UPC Version E allows manufacturers to encode a limited number of unique twelve digit product codes into eight digits.

UPC Version E is a numeric, continuous, fixed length bar code. The eight-digit code consists of a number system character (0), a three-digit manufacturer's code, a three-digit product code, and a check digit. UPC-E Version 0 automatically includes a zero in the number system position; UPC-E Version 1 includes a one.

The Universal Code Council as listed below establishes guidelines for manufacturers to properly code products.

EAN

European Article Numbering system also known as the World Product Code (WPC), and the International Article Numbering Association (IAN or EAN), is a symbology developed for international businesses.

EAN has two versions, EAN 8 and EAN 13, which are variations of the original UPC coding system developed in the United States. Both versions are fixed length, discrete and numeric bar codes. The first two digits of an EAN bar code are the country code. Country codes 00, 01, 03, 04, and 06-09 are assigned to the United States for compatibility with UPC. An EAN scanner can decode UPC; however, the reverse is not necessarily true.

The EAN 13 symbology contains the same number of digits as UPC Version A except it includes an additional digit representing a country code. Except "0", character set patterns for the left half of EAN 13 are the reverse of UPC Version E. When calculating the check digit, EAN 13 ignores the leftmost digit and calculates the check digit in the same manner as UPC-A.

The EAN 8 symbology is divided into left (odd parity) and right (even parity) halves. It has left and right guard bars and eight digits including a modulus 10 check digit and is structured like UPC Version A symbology except that four digits are encoded in each half.

Bookland EAN

Bookland EAN follows the same guidelines as an EAN 13 bar code and in addition, contains the ISBN (International Standard Book Number). Bookland EAN bar codes always begin with 978.

Interleaved 2 of 5

Interleaved 2 of 5 is a high density, continuous, numeric, self-checking, bi-directional symbology used in warehousing, product or container identification, airline ticketing, baggage and cargo handling, industrial and automotive applications.

The following figure details an Interleaved 2 of 5 bar code, for example, 0123. The adjacent characters are interlaced (interleaved) alternating the spaces from one character with the bars of the other. Interleaved 2 of 5 bar code encodes two digits; one in the bars and one in the spaces and requires an even number of digits to encode information. All of the even positioned data is encoded in the spaces; and, all of the odd positioned data is encoded in the bars. If the encoded data has an odd number of characters, you must add a leading zero (0).

There are two wide bars and three narrow--five spaces in each character, two are wide and three are narrow. A complete Interleaved 2 of 5 bar code consists of a start code (two narrow bars and two narrow spaces), data characters, and a stop code (a wide bar, a narrow space and a narrow bar). It may also contain an optional check digit

Code 128

Introduced in 1981 and widely used in general industrial, retail container labeling and inventory, Code 128 is a high density bar code and represents the Full 128 ASCII Character Set.

It is a variable length, continuous, bi-directional, alphanumeric symbology originally designed to encode multiple identification into a compact alphanumeric bar code. Each character consists of three bars and three spaces and an overall length of eleven modules (either black or white). Bars and spaces can either be one, two, three, or four modules wide.

The character set consists of 103 different characters, three start characters and one unique stop character. With use of a function code, (FNC 1, FNC 2, FNC 3, FNC 4), Code 128 offers a concatenation feature, and has the ability to decode and transmit several messages as one. The function code determines instructions for the bar code reader as follows:

UCC-128 Serial Shipping Container Code (Mod 10)

UCC-128 Mod 10 is a subset of Code 128 and is a twenty-two character, alphanumeric, continuous, fixed bar code, used primarily on shipping containers.

Every bar code starts with a Start C code followed by a function code (FNC1), pertinent data characters (19 digits), modulus 10 check digit, modulus 103 check digit and stop code.

Start C code, together with the function code, forms the overall UCC start code notifying the scanner that a specific UCC-128 bar code follows. The two-digit qualifier code distinguishes it from other UCC and EAN codes. The one digit code identifies the type of serialized shipping container package. UCC/EAN approved valid packaging values are listed below:

A six-digit UPC manufacturer number together with an additional zero completes the seven-digit manufacturer's identification number and is assigned by the UCC/EAN. The Shipping Container Serial Number Identifier individually identifies each shipping container packaged by a provider.

Codabar

Developed in 1972 and commonly used in libraries, blood banks, air parcel carriers, photofinishing envelopes and the medical industry, Codabar is a numeric, bi-directional, variable length, discrete, self-checking bar code symbology.

In 1977, the Committee for Commonality in Blood Banking Automation (CCBBA) formally adopted Codabar for marking blood bags. It is common for bar codes to be concatenated for use in the blood bank industry. When two adjacent symbols use a D stop character, and the second symbol begins with a D start character, both can be scanned simultaneously, producing a concatenated bar code.

Codabar consists of sixteen characters, zero through nine and the characters $, :, /, ., +, and -. Codabar characters are made up of four bars and three intervening spaces consisting of a quiet zone, start/stop character, data characters, start/stop character and an ending quiet zone. The code has variable intercharacter spacing and code density of up to ten characters per inch. Depending on the specific character, eighteen different values can be assigned to bar widths and spaces. A check digit is not required; however, if additional data security is needed, a recommended modulus 16 check digit calculation is available.

Twelve main characters (0 through 9, -, $) have one wide bar and one wide space. Special characters (: / . +) have three wide bars and no wide spaces. Four different start/stop characters (A, B, C, D) are encoded with one wide bar and two wide spaces.

MSI/Plessey

MSI/Plessey is commonly used in supermarket shelf labeling and formerly used in early library applications for scanning with various input devices to facilitate inventory reordering. Developed in England with formal specifications first dated in 1971, Plessey has several variants, MSI, Telxon and Anker Codes.

MSI/Plessey code is sometimes referred to as pulse width modulated, wherein each pair of bars and spaces contain one bit of information. However, pulse width modulated codes do not carry significant technical benefits over more up-to-date symbologies. MSI/Plessey is a variable length, numeric, continuous bar code, and is not self-checking.

A complete MSI/Plessey code consists of a start code, data characters, modulus 11 check digit, modulus 10 check digit (optional) and a reverse start character. Each character consists of four bars and four spaces. The zero bit consists of a narrow bar followed by a wide space; a one bit consists of a wide bar followed by a narrow space.

Code 93

Introduced in 1982, Code 93 is similar to Code 39 except that it encodes more characters per inch. It was designed as a competitive symbology to Code 128 and to provide an extended character set to Code 39. Code 93 can be integrated into a system using Code 39 without changing system software but, only when a decoded, autodiscriminating input device is used.

Code 93 is an alphanumeric, variable length, continuous bar code, and is not self-checking. As of this publication, no national or international industry organization has officially adopted Code 93.

The data characters of both Code 93 and Code 39 symbologies are the same; the start/stop codes and the check digits are not transmitted by the input device. Code 93, similar to Code 39, permits concatenation of consecutive bar codes containing a leading space character. The scanned leading space character is appended to a storage buffer. This process continues for all successive bar codes with a leading space and is added to previously stored ones. When a Code 93 bar code is scanned and does not contain a leading space, the entire buffer is transmitted and cleared.

A complete Code 93 bar code consists of a leading guard bar (quiet zone), start code, data characters, C check digit, K check digit, stop code, termination bar and end guard bar (quiet zone). Code 93 characters consist of three bars and three spaces, except the start/stop character, which is represented by the € symbol. Circle codes ($, %, / and +) are used as a preceding character of a two character sequence, and represent all 128 ASCII characters. Preceding characters are used to expand Code 93, similar to an extended ASCII character set for Code 39.

Overall length of a character is nine modules, black or white and can be one, two, three, or four modules wide. Each character begins with a bar and ends with a space. The Code 93 character assignments shown in the following table represent only forty-eight of the total fifty-six characters-forty-three are the same as the Code 39 character set, and four are control characters.

Every Code 93 bar code contains two check digits, C and K, which are variations of modulus 47 check digit. These check digits are not transmitted by input devices or printed in human-readable terms.

Code 11

Developed in 1977 for labeling telecommunications components and equipment, Code 11 is a high density, numeric, variable length, discrete bar code and is not self-checking.

A complete Code 11 bar code consists of a start code, data characters, a C check digit, and occasionally a K check digit. Ordinarily when data characters consist of ten digits or less, only the C check digit is used.

Three bars represent each data character with two intervening spaces for a total of five elements. Three different bar widths and two different space widths can represent each character: two wide, three narrow or one wide, four narrow. The character set consists of ten digits and a dash symbol (special character).