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Barcode Glossary

Our Glossary of Barcode Terms helps simplify the business of asset identification.

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Achieved Width

The calculated element width based on measurements.


A character set that contains letters, digits, and other characters such as punctuation marks. Note that in programming an alphanumeric cannot be used to do arithmetic.

Alphanumeric Bar Code

A mixture of bar configurations representing alphabetic and numeric symbols.


The opening in an optical system that establishes the field of view.

ASCII Character Set

128 characters including both control and printing characters.

Aspect Ratio

The ratio of height to width of a bar code symbol. A code twice as high as wide would have an aspect ratio of 2; a code twice as wide as high would have an aspect ratio of .5.


A Bar is the dark (reflective) element of a bar code, compared to the light space which is the light reflective element. The Bar’s reflectance is less than that of the global threshold.

Bar Code

Cyphers constructed from a series of dark and light bars organized into various patterns according to specific rules, which represent letters, numerals, and other human–readable symbols. Coding variables include the number of dark bars, the relative positions of dark bars within a code structure, the variable widths of the dark bars, the variable widths of the light bars, and their relative positions.

Bar Code Density

The number of characters that a code can represent, per linear inch.

Bar Height

The bar dimension perpendicular to the element width. The measurement of the dimension of a bar element, also known as the bar length.

Bar Length

Measurement of the long dimension of a bar.

Bar Width

The lateral dimension of a bar; bar thickness.

Bar Width Ratio

The ration of the widest bar or space to the narrowest.

Bar Reflectance (Rb)

The smallest reflectance value in a bar.

Bi-directional Code

A bar code that permits reading either from left to right or from right to left.

Binary Code

A code which makes use of two distinct characters, usually 0 and 1, a code using the binary number system ("powers of two"). In a broad sense all bar codes are binary, since they use only light and dark area.


A one or a zero.

Bit Mapping

A large area can be divided into a grid of smaller areas called pixels. When such a grid is placed over a graphic image, and the presence or absence of a portion of that graphic image is sensed in each pixel, the process is called bit mapping.


The smallest group of elements assigned by a symbology to uniquely represent one or more numbers, letters, punctuation marks or other information.

Character Set

The numbers and/or letters and other markings included in a bar code symbol.

Check Digit (Check-Sum)

A character included within a bar code symbol whose value is used for performing a mathematical check of the validity of the decoded data. Used for error detection.

Code 39

Discrete code, alphanumeric, flexible format, optional check digit, and 2 Bar/Space widths.

Code 128

Continuous code, alphanumeric, flexible format, mandatory check digit, and 4 bar/space widths.

Data Matrix

Two dimension symbology, (see InfoTech handbook for further information)

Data Set

A named collection of logically related data items having one of several prescribed arrangements - direct, random, or serial.


Can be graded as “A,” “B,” “C,” “D,” or “F.” The Decodability grade indicates the amount of error in the width of the most deviant element in the symbol. The less deviation in the symbology, the higher the grade. Decodability is a measure of print accuracy using the symbology reference decode algorithm.


Extracting the information which has been encoded in a bar code symbol.

Dimensional Deviation (DD)

The amount of deviation measured in the bars and/or spaces of a scanned symbol from the specification.

Discrete Code

A bar code or symbol in which the spaces between the characters are not part of the data stored in the symbol.

Edge Contrast (EC)

The difference between the space reflectance (Rs) and adjoining bar reflectance (Rb).



A general term used to specify a bar or space in a bar code symbol.

Element Width

The thickness or width of a bar as measured from its leading edge to its trailing edge.

Error Correction

Also referred to as Data Redundancy; symbol characters reserved for error detection or correction. These characters are calculated mathematically from the other symbol characters.

Error Detection

Also referred to as Data Security; keeps the symbol from being decoded as erroneous data. Error correction characters can be reserved for error detection, in which case they function as check characters.

First Read Rate

The percentage of successful “reads” of a bar code symbol during the first test.


The physical or geometrical arrangement specified for a particular bar code symbol.

Global Threshold (GT)

The global threshold is drawn through the middle of a profile to distinguish spaces above the line and bars below. The reflectance value is calculated by dividing the symbol contrast (SC) by 2 and adding the minimum reflectance, Rmin.

Guard Bar

The first and last bars of a bar code, usually with the pattern 101. A guard bar generally follows the leading quiet zone and precedes the trailing quiet zone. This term is used mostly for UPC/EAN symbologies.

Inter-character Gap

In discrete barcodes, the space that disconnects the two contiguous characters. When present, inter-character gaps are considered spaces (elements) for purposes of edge determination and reflectance parameter grades.


A bar code where characters are paired together using bars to represent the first character and spaces to represent the second.

Interleaved Bar Code

A combination in which both black and white bars are significant, but where the black bars relate to one cypher and the white bars to some other cypher.

Interleaved 2 of 5

A compact number-only bar code with two wide components out of five, per character. This symbology requires an even number of characters, is a continuous code, numeric-only, semi-flexible format, 2bar/space widths and optional check digit


One thousandth of an inch (0.001 inch) or approximately 0.0254mm.

Modulation (MOD)

The parameter is graded either “A,” “B,” “C,” “D,” or “F”. This grade is based on the relationship between minimum edge contrast (ECmin) and symbol contrast (SC).


The greater the difference between minimum edge contrast and symbol contrast, the lower the grade.

Scanners and verifiers perceive the narrower bars and spaces to have less intensity than wider bars and spaces; the comparison of the lesser intensity of narrow elements to the wide elements is called modulation. This condition is affected by aperture size.

N (wide to narrow ratio)

In symbologies with two element widths, the wide to narrow ratio of elements is calculated by finding the average wide bar width and average wide space width and dividing the sum by 2 times Z. Inter-character gaps, if applicable, are not included.

N= (avg. wide bar + avg. wide space)/ (2*Z)


Two-dimensional symbology, in which over 50% of symbol can be destroyed and still recover 100% of the information. (See InfoTech handbook for further information)


Picture element. When the area occupied by a graphic image is divided into a grid of smaller areas, each of the smaller areas is called a pixel.

Print Contrast Signal (PCS)

The comparison between the reflectance (brightness difference) of bars and spaces in a symbol.

Quiet Zone

The area immediately preceding the START cypher and following the STOP cypher, which contains no marking.


The measure of the amount of light reflected from an illuminated surface.

Reflectance Minimum

A measure of the amount of light reflected from an illuminated surface. The reflectance value of the “lightest” space in a symbol must be equal to or greater than twice the reflectance value of the “darkest” bar.


A barcode or symbol that uses an algorithm that can be applied to each character, to check and guard against undetected errors. Non-self-checked codes may use a check digit or other redundancy in addition to the data message.


The element of a bar code symbol whose reflectance is greater than the global threshold. A Space is the light reflective element (as opposed to the bar which is the dark reflective element).

Specular Reflection

The reflection of light from a surface at an angle both equal and opposite to the angle of incidence.

Start and Stop Characters

Characters typically used at the beginning and end of each bar code symbol.

Substitution Error

This error can be seen in a mis-encodation, mis-read, or human operator error where characters that were to be entered were substituted with erroneous information.


The material or medium on which bar codes are produced.

Symbol Contrast (SC)

Symbol Contrast is the difference in reflectance values of the “lightest” space (including the quiet zone) and the “darkest” bar of the symbol. The greater the difference, the higher the grade. The parameter is graded as either “A,” “B,” “C,” “D,” or “F.”

SC= Rmax-Rmin

Symbol Grade

The simple average of all the overall profile grades using the standard weighing

The symbol grade may be stated as a decimal or converted to a letter grade. The measuring aperture number and the nominal wavelength are also listed.


A set of rules for encoding the information into a bar code symbol.

Universal Product Code

(UPC) Primarily used in retail, price lookup concept

"x" dimension

Equals size of smallest Bar or Space. The smaller the x dimension the smaller the bar code.

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