Attachment_6_ISO-IEC_16388_2007_Code_39_bar_code.pdf

COPYRIGHT WARNING

This document may include materials that are protected under copyright.

Digital materials checked out from the Coast Guard Surface Forces Logistics Center

Library are not intended to be copied, transmitted, or disseminated in any way, and should not be permanently saved to the patron’s work station. Patrons are asked to remain in alignment with any copyright restrictions protecting library materials.

In order to remain in alignment with copyright restrictions, please do not print, copy, transmit or disseminate any of the copyrighted materials in this document.

Please delete this document once you have finished working with it.

USCG/SFLC/ESD/TIMB - SFLC Tech Library

707 E Ordnance Road

Baltimore, Maryland 21226

Reference number

ISO/IEC 16388:2007(E)

© ISO/IEC 2007

INTERNATIONAL

STANDARD

ISO/IEC

16388

Second edition 2007-05-15

Information technology � Automatic identification and data capture techniques � Code 39 bar code symbology specification

Technologies de l'information � Techniques d'identification automatique et de capture des données � Spécifications des symbologies des codes à barres, code 39

PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this area.

Adobe is a trademark of Adobe Systems Incorporated.

Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

COPYRIGHT PROTECTED DOCUMENT

© ISO/IEC 2007

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body in the country of the requester.

ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyright@iso.org Web www.iso.org

Published in Switzerland ii © ISO/IEC 2007 � All rights reserved

© ISO/IEC 2007 � All rights reserved iii

Contents Page

Foreword............................................................................................................................................................ iv

Introduction ........................................................................................................................................................ v

1 Scope

2 Normative references

3 Terms and definitions

4 Requirements

4.1 Symbology characteristics

4.2 Symbol structure

4.3 Character encodation

4.4 Dimensions

4.5 Reference decode algorithm

4.6 Symbol quality

4.7 Application-defined parameters

Annex A (informative) Additional features

Annex B (informative) Guidelines for the use of Code 39

Annex C (normative) Symbology identifier

Annex D (informative) Example of application-defined parameters

Bibliography iv © ISO/IEC 2007 � All rights reserved

Foreword

ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the development of International Standards through technical committees established by the respective organization to deal with particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of the joint technical committee is to prepare International Standards. Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International Standard requires approval by at least 75 % of the national bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.

ISO/IEC 16388 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 31, Automatic identification and data capture techniques.

This second edition cancels and replaces the first edition (ISO/IEC 16388:1999), which has been technically revised.

© ISO/IEC 2007 � All rights reserved v

Introduction

The technology of bar coding is based on the recognition of patterns encoded in bars and spaces of defined dimensions. There are numerous methods of encoding information in bar code form, known as symbologies.

Code 39 is one such symbology. The rules defining the translation of characters into bar and space patterns and other essential features are known as the symbology specification.

In the past, symbology specifications were developed and published by a number of organizations, resulting in certain instances in conflicting requirements for certain symbologies.

Manufacturers of bar code equipment and users of bar code technology require publicly available standard symbology specifications to which they can refer when developing equipment and application standards.

INTERNATIONAL STANDARD ISO/IEC 16388:2007(E)

© ISO/IEC 2007 � All rights reserved 1

Information technology � Automatic identification and data capture techniques � Code 39 bar code symbology specification

1 Scope

This International Standard specifies the requirements for the bar code symbology known as Code 39; it specifies Code 39 symbology characteristics, data character encodation, dimensions, tolerances, decoding algorithms and parameters to be defined by applications. It specifies the Symbology Identifier prefix strings for Code 39 symbols.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO/IEC 646, Information technology � ISO 7-bit coded character set for information interchange

ISO/IEC 15416, Information technology � Automatic identification and data capture techniques � Bar code print quality test specification � Linear symbols

ISO/IEC 15424, Information technology � Automatic identification and data capture techniques � Data Carrier Identifiers (including Symbology Identifiers)

ISO/IEC 19762-1, Information technology � Automatic identification and data capture (AIDC) techniques � Harmonized vocabulary � Part 1: General terms relating to AIDC

ISO/IEC 19762-2, Information technology � Automatic identification and data capture (AIDC) techniques � Harmonized vocabulary � Part 2: Optically readable media (ORM)

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/IEC 19762-1 and ISO/IEC 19762-2 apply.

4 Requirements

4.1 Symbology characteristics

The characteristics of Code 39 are as follows.

a) Encodable character set:

1) full alphanumeric A to Z and 0 to 9 (ASCII characters 65 to 90 and 48 to 57 inclusive, in accordance with ISO 646).

2 © ISO/IEC 2007 � All rights reserved

2) special characters: space $ % + - . / (ASCII characters 32, 36, 37, 43, 45, 46 and 47, respectively, in accordance with ISO 646).

3) start/stop character.

b) Code type: discrete.

c) Elements per symbol character: 9, of which 3 wide and 6 narrow, comprising 5 bars and 4 spaces.

d) Character self-checking: yes.

e) Data string length encodable: variable.

f) Bidirectionally decodable: yes.

g) Symbol check character: one, optional (see Annex A).

h) Symbol character density: 13 to 16 modules per symbol character, inclusive of minimum intercharacter gap, depending on wide/narrow ratio.

i) Non-data overhead: equivalent to 2 symbol characters.

4.2 Symbol structure

As illustrated in Figure 1, Code 39 symbols shall comprise

a) leading quiet zone;

b) start character;

c) one or more symbol characters representing data (including symbol check character, if present);

d) stop character;

e) trailing quiet zone.

A space, the intercharacter gap, shall separate characters within the symbol.

QUIET ZONE START CHARACTER "1" "A" STOP CHARACTER QUIET ZONE

1A

Figure 1 � Code 39 symbol

4.3 Character encodation

4.3.1 Symbol character structure

Each symbol character comprises nine elements (five bars and four spaces) of which six are always narrow (either three narrow bars and three narrow spaces, or five narrow bars and one narrow space) and three are always wide (one wide space and two wide bars when there are three narrow bars, or three wide spaces when there are five narrow bars). This parity feature enables character self-checking to be carried out.

© ISO/IEC 2007 � All rights reserved 3

4.3.2 Symbol character assignments

Table 1 defines all the Code 39 character assignments.

Table 1 � Code 39 character assignments

Char. Encodation Pattern B S B S B S B S B

ASCII

value

0 0 0 0 1 1 0 1 0 0 48

1 1 0 0 1 0 0 0 0 1 49

2 0 0 1 1 0 0 0 0 1 50

3 1 0 1 1 0 0 0 0 0 51

4 0 0 0 1 1 0 0 0 1 52

5 1 0 0 1 1 0 0 0 0 53

6 0 0 1 1 1 0 0 0 0 54

7 0 0 0 1 0 0 1 0 1 55

8 1 0 0 1 0 0 1 0 0 56

9 0 0 1 1 0 0 1 0 0 57

A 1 0 0 0 0 1 0 0 1 65

B 0 0 1 0 0 1 0 0 1 66

C 1 0 1 0 0 1 0 0 0 67

D 0 0 0 0 1 1 0 0 1 68

E 1 0 0 0 1 1 0 0 0 69

F 0 0 1 0 1 1 0 0 0 70

G 0 0 0 0 0 1 1 0 1 71

H 1 0 0 0 0 1 1 0 0 72

I 0 0 1 0 0 1 1 0 0 73

J 0 0 0 0 1 1 1 0 0 74

K 1 0 0 0 0 0 0 1 1 75

L 0 0 1 0 0 0 0 1 1 76

M 1 0 1 0 0 0 0 1 0 77

N 0 0 0 0 1 0 0 1 1 78

O 1 0 0 0 1 0 0 1 0 79

P 0 0 1 0 1 0 0 1 0 80

Q 0 0 0 0 0 0 1 1 1 81

R 1 0 0 0 0 0 1 1 0 82

S 0 0 1 0 0 0 1 1 0 83

4 © ISO/IEC 2007 � All rights reserved

Char. Encodation Pattern B S B S B S B S B

ASCII

value

T 0 0 0 0 1 0 1 1 0 84

U 1 1 0 0 0 0 0 0 1 85

V 0 1 1 0 0 0 0 0 1 86

W 1 1 1 0 0 0 0 0 0 87

X 0 1 0 0 1 0 0 0 1 88

Y 1 1 0 0 1 0 0 0 0 89

Z 0 1 1 0 1 0 0 0 0 90 hyphen 0 1 0 0 0 0 1 0 1 45 period 1 1 0 0 0 0 1 0 0 46 space 0 1 1 0 0 0 1 0 0 32

$ 0 1 0 1 0 1 0 0 0 36

/ 0 1 0 1 0 0 0 1 0 47

+ 0 1 0 0 0 1 0 1 0 43

% 0 0 0 1 0 1 0 1 0 37

S/S or

0 1 0 0 1 0 1 0 0 none

NOTE 1 S/S denotes the start and stop character, usually graphically represented as *

NOTE 2 In the columns headed B and S, 0 represents a narrow element and 1 a wide element.

4.3.3 Start and stop characters

The Code 39 start and stop character is usually depicted in human-readable form by a * (asterisk). This character shall not form part of the data encoded elsewhere in the symbol and shall not be transmitted by the decoder.

The start character shall be positioned at the normal left end of the data symbol characters, separated from the first bar of the leading data character by an intercharacter gap. The stop character shall be positioned at the normal right end of the data symbol characters (including symbol check character if present), separated from the final bar of the trailing data character by an intercharacter gap.

4.3.4 Optional symbol check character

Annex A defines the symbol check character position and calculation.

4.4 Dimensions

Code 39 symbology shall use the following nominal dimensions.

a) Width of narrow element (X): the X dimension of Code 39 symbols should be defined by the application specification having due regard to the availability of equipment for the production and reading of symbols and complying with the general requirements of the application. See 4.7.1.

b) Wide/narrow ratio (N): 2,0 : 1 to 3,0 : 1.

© ISO/IEC 2007 � All rights reserved 5

c) Width of intercharacter gap (I):

1) minimum: equal to X;

2) maximum:

for X < 0,287 mm: 5,3X;

for X 0,287 mm: 1,52 mm or 3X, whichever is greater.

d) Minimum width of quiet zone: 10X.

e) Recommended minimum bar code height for manual scanning: 5,0 mm or 15 % of symbol width excluding quiet zones, whichever is greater.

NOTE The width, W (in millimetres), of a Code 39 symbol, including quiet zones, can be calculated from the following expression:

2 3 6 1 2W C N X C I Q where

W is the symbol width;

C is the number of data characters (including symbol check character if used);

N is the wide/narrow ratio;

X is the width of a narrow element in millimetres;

l is the width of the intercharacter gap in millimetres;

Q is the width of the quiet zone in millimetres.

4.5 Reference decode algorithm

Bar code reading systems are designed to read imperfect symbols to the extent that practical algorithms permit. This section describes the reference decode algorithm used in the computation of the decodability value described in ISO/IEC 15416.

a) Confirm presence of a leading quiet zone.

b) For each symbol character (including start and stop characters):

1) Measure the total width of 5 bars and 4 spaces; call this S.

2) Compute a threshold value, T = S / 8.

3) Compare each element width for that character with the value T. If element width is greater than T, assume element is wide; if not, assume element is narrow.

4) Determine if pattern of wide and narrow elements matches a valid character from the allowable set.

c) The first symbol character read must be a start/stop character, from which the scan direction can be deduced.

d) Continue character reading until a valid start/stop character is encountered.

e) Confirm presence of a trailing quiet zone.

6 © ISO/IEC 2007 � All rights reserved

4.6 Symbol quality

4.6.1 Test specification

In order to verify whether a symbol meets the specifications in this International Standard it shall be tested using the test specification defined in ISO/IEC 15416, which defines a standardized methodology for measuring and grading bar code symbols, as supplemented in 4.6.2. ISO/IEC 15416 lays down conditions under which measurements should be made; and defines methods of determining an overall quality grade based on the attributes of the bar code symbol. The reference decode algorithm defined in 4.5 shall be used for the assessment of the "decode" and "decodability" parameters under ISO/IEC 15416.

The overall symbol grade shall be expressed in the form shown in the following example:

1,5 / 10 / 660 where

1,5 is the overall symbol quality grade;

10 is the measuring aperture reference number (in this example 0,25 mm diameter);

660 is the peak response wavelength in nanometres.

ISO/IEC 15416 allows for additional pass/fail criteria to be stipulated by a symbology specification. For Code 39, the additional criteria are given in 4.6.2. Any individual scan profile which does not meet these requirements shall receive a grade of 0.

4.6.2 Additional parameters

4.6.2.1 Wide/narrow ratio

Symbols shall be produced with a nominal N from 2,0 to 3,0 inclusive. The measured value of N in any scan profile shall be in the range 1,8 to 3,4 inclusive. The wide/narrow ratio in the scan reflectance profile under ISO/IEC 15416 shall be measured and graded as follows.

1,8 N 3,4: Grade 4.

N < 1,8 or N > 3,4: Grade 0.

4.6.2.2 Intercharacter gap

For symbols with a measured narrow element width (Z) less than 0,287 mm, the maximum allowed intercharacter gap is 5,3Z. For symbols with Z greater than or equal to 0,287 mm, the maximum intercharacter gap is the greater of 3Z or 1,52 mm. Each intercharacter gap in the scan reflectance profile under ISO/IEC 15416 shall be measured and graded as follows.

I Gmax: Grade 4.

I < Gmax: Grade 0.

where

Gmax = 5,3Z for Z < 0,287 mm or Gmax = MAX(1,52 mm, 3Z) for Z 0,287 mm

© ISO/IEC 2007 � All rights reserved 7

4.6.2.3 Quiet zone

The quiet zone at each end of the symbol shall be a minimum of 10Z. Both left and right quiet zones on each scan reflectance profile under ISO/IEC 15416 shall be measured and graded as follows.

Quiet Zone 10Z: Grade 4.

Quiet Zone < 10Z: Grade 0.

NOTE In 4.6.2.1 to 4.6.2.3, the requirements are based on the actual, rather than intended, measurements of the parameter; for this reason the Z dimension is appropriate rather than the X dimension.

4.7 Application-defined parameters

4.7.1 Symbology and dimensional characteristics

In order for a Code 39 symbol to be printed and to be scannable in a given application it is necessary for the following symbology and dimensional parameters to be specified by the application specification:

a) selection of subset of the encodable character set;

b) the number of data characters in the symbol, which may be fixed, variable or variable up to a defined maximum;

c) whether the modulo 43 symbol check character is to be used (see A.1) and whether it is to be transmitted by the decoder;

d) whether a data check character is to be used and if so the algorithm for its calculation;

e) range of X dimension;

f) range of wide/narrow ratio;

g) intercharacter gap;

h) minimum bar height.

NOTE 1 For applications wishing to take advantage of enhanced data security, a symbol check character should be used.

NOTE 2 The wide/narrow ratio should be as high as possible within the range specified in 4.4 to maximize reading performance.

An example is given in Annex D.

4.7.2 Optical specifications

In order for a bar code symbol to be scannable in a given application, it is necessary to specify certain optical parameters. The selection of the parameters shall be made in the application standard and shall include the specification of peak response wavelength;

spectral half power band width with which the symbol and the scanner should conform;

the spot size of the scanner;

the parameters for reflectance of the bars and spaces;

8 © ISO/IEC 2007 � All rights reserved the conditions under which optical measurements should be made;

the extent of permissible imperfections within the bar code symbol.

An example is provided in Annex D.

4.7.3 Test specifications

Application specifications should define the minimum overall symbol grade for acceptability (including minimum grade level, required measurement aperture and peak response wavelength) when symbols are measured in accordance with ISO/IEC 15416.

© ISO/IEC 2007 � All rights reserved 9

Annex A (informative)

Additional features

A.1 Check character

A.1.1 Symbol check character

For applications requiring enhanced data security, a symbol check character should be used, in which case the symbol check character should be positioned immediately following the final data character and before the stop character. The inclusion of the symbol check character should be determined by the application standard.

When included, the following symbol check character algorithm should be used.

a) Each data character is assigned a numerical value as shown in Table A.1 below.

b) Calculate the sum of the numerical values for all the data characters of a symbol.

c) Divide this sum by 43.

d) The character whose value (from Table A.1) is the remainder from the division in step c) is used as the check character.

Table A.1 � Numerical character values for modulo 43 check

Character Value Character Value Character Value

0 0 F 15 U 30

1 1 G 16 V 31

2 2 H 17 W 32

3 3 I 18 X 33

4 4 J 19 Y 34

5 5 K 20 Z 35

6 6 L 21 - 36

7 7 M 22 . 37

8 8 N 23 SPACE 38

9 9 O 24 $ 39

A 10 P 25 / 40

B 11 Q 26 + 41

C 12 R 27 % 42

D 13 S 28

E 14 T 29

The modulo 43 symbol check character may be transmitted by the decoder.

10 © ISO/IEC 2007 � All rights reserved

EXAMPLE For the data "CODE 39":

Data characters C O D E SPACE 3 9

Character values 12 24 13 14 38 3 9

Sum of values 113

Divide by 43 113/43 = 2 remainder 27

Character value 27 corresponds to R

Data with symbol check character C O D E SPACE 3 9 R

A.1.2 Data check character

When transmitted by the decoder, the modulo 43 check character may be used as a data check character.

Alternatively, an algorithm as described in ISO 7064, or another algorithm defined in the application specification, may be used to calculate a data check character, provided that suitable provision for its calculation and verification is included in the symbol generation and message processing software. Such a data check character should be the final character of the data string and shall be transmitted by the decoder.

A.2 Human-readable interpretation

A human-readable interpretation of the data characters (and data and symbol check character(s), if used) should normally be printed with the Code 39 symbol encoding them. Start/stop characters may be printed.

Character size and font are not specified, and the interpretation may be printed anywhere in the area surrounding the symbol, as long as quiet zones are not encroached upon.

A.3 Optional data transmission modes

Decoders may be programmed to respond to Code 39 symbols in non-standard ways to satisfy particular application requirements. Three such schemes are defined below: full ASCII (see A.3.1), message append (see A.3.2) and control functions (see A.3.3). Since the use of these features requires special decoder programming, they are not recommended for general applications, where there could be confusion with standard Code 39 symbols.

A.3.1 Full ASCII

The full 128 character ASCII character set in accordance with ISO 646 IRV (including the C0 set of control characters defined in ISO/IEC 6429 with values 28 � 31 modified to FS, GS, RS and US respectively) may be encoded using either one or combinations of two symbol characters, made up of one of the four characters ($ + % /) followed by one of the 26 alphabetic characters. These combinations are shown in Table A.2. When the full ASCII option is enabled in the decoder, only the ASCII equivalent of the symbol character combinations and not their literal translation should be transmitted.

A.3.2 Message append

It is sometimes advantageous to break up long messages into multiple shorter symbols. If the first data character of a Code 39 symbol is a 'space', the decoder may be programmed to append the information contained in the remainder of the symbol to a storage buffer (data not transmitted). This operation continues for all successive Code 39 symbols with a leading 'space', with messages being added to the end of previously stored ones. When a message is read which does not contain a leading 'space', the contents are appended to the buffer, the entire buffer is transmitted, and the buffer is cleared. Where the sequence of data is significant, the application should make provisions to ensure reading of the symbols in the correct sequence.

© ISO/IEC 2007 � All rights reserved 11

A.3.3 Control functions

An additional system-specific mode is also available, which may be used for closed systems but shall not be used in open systems. By using combinations of two symbol characters from the set ( $ % + - . / ) (ASCII characters 36, 37, 43, 45, 46, 47), 36 control functions may be programmed into a system. Decoders may be specially programmed to respond to these symbols and perform the defined functions. The literal translation of these character pairs shall not be transmitted and the symbology identifier (see Annex C) shall not be used.

Table A.2 � Encoding the Full ASCII character set in Code 39

ASCII CODE ASCII CODE ASCII CODE ASCII CODE

NUL %U SP SPACE @ %V ' %W

SOH $A ! /A A A a +A

STX $B " /B B B b +B

ETX $C # /C C C c +C

EOT $D $ /D D D d +D

ENQ $E % /E E E e +E

ACK $F & /F F F f +F

BEL $G ' /G G G g +G

BS $H ( /H H H h +H

HT $I ) /I I I i +I

LF $J * /J J J j +J

VT $K + /K K K k +K

FF $L , /L L L l +L

CR $M - - M M m +M

SO $N . . N N n +N

SI $O / /O O O o +O

DLE $P 0 0 P P p +P

DC1 $Q 1 1 Q Q q +Q

DC2 $R 2 2 R R r +R

DC3 $S 3 3 S S s +S

DC4 $T 4 4 T T t +T

NAK $U 5 5 U U u +U

SYN $V 6 6 V V v +V

ETB $W 7 7 W W w +W

CAN $X 8 8 X X x +X

EM $Y 9 9 Y Y y +Y

SUB $Z : /Z Z Z z +Z

ESC %A ; %F [ %K { %P

FS %B < %G \ %L | %Q

GS %C = %H ] %M } %R

RS %D > %I ^ %N ~ %S

US %E ? %J _ %O DEL %T or %X or %Y or %Z

12 © ISO/IEC 2007 � All rights reserved

Annex B (informative)

Guidelines for the use of Code 39

B.1 Autodiscrimination compatibility

Code 39 may be read by suitably programmed bar code decoders which have been designed to autodiscriminate it from other symbologies.

The decoder's valid set of symbologies should be limited to those needed by a given application to maximize reading security.

When Code 39 is used in an autodiscrimination environment with Interleaved 2 of 5 symbols, the following guidelines shall be followed:

a) The nominal intercharacter gaps in the Code 39 symbols shall be no wider than the narrow elements.

b) The reading system shall be constrained and the decoder programmed to ensure that the number of characters (including start and stop characters) in all Code 39 symbols is greater than one-half of the number of data characters in the Interleaved 2 of 5 symbols.

c) Interleaved 2 of 5 symbols shall have a minimum length of six characters in environments where they are autodiscriminated with Code 39.

The use of fixed length symbols, bearer bars and check characters with the Interleaved 2 of 5 symbols as recommended in ISO/IEC 16390 provides additional protection in an autodiscrimination environment.

B.2 System considerations

It is important that the various components (printers, labels, scanners) making up a bar code installation operate together as a system. A failure in any component, or a mismatch between them, can compromise the performance of the overall system. The characteristics of the printer, symbol and scanner should be matched to achieve the desired performance.

B.3 Printing considerations

B.3.1 Pixel-based printing

Graphics software used to create bar codes on pixel-based printers must scale each bar and space exactly to the pixel pitch of the printer being used, irrespective of the symbology. For two-width symbologies like Code 39 the number of pixels comprising narrow bar and space elements, before any compensation for bar width growth or loss, shall be a fixed and constant integer, and the number of pixels comprising wide elements, before any compensation for bar width growth or loss, shall be the integer product of the number of pixels in the narrow element multiplied by the wide:narrow ratio. The width of any required inter-character gap shall also be a fixed integer number of pixels. Therefore, a given printer can only print a certain set of X dimensions and wide:narrow ratios.

Compensation for uniform bar width growth (or loss) must be in equal offsetting amounts on all bars and spaces in the symbol. This may be accomplished by changing an integer number of pixels from dark to light or light to dark in the same manner for each bar-space pair in the symbol and for the last bar in the symbol. For

© ISO/IEC 2007 � All rights reserved 13 example, all pixels along the same edge of every bar in the symbol could be changed from dark to light, or pixels along both edges of every bar in the symbol could be changed from dark to light, provided that the printer resolution is sufficient to allow this to be performed satisfactorily. Any set of dark to light or light to dark pixel changes is acceptable provided the adjustment is performed consistently across the whole symbol and does not change the total symbol character width. Failure to follow these principles results in degraded symbol quality and often results in unreadable symbols.

General purpose printing software designed to support a wide range of printers should provide the user with the capability of adjusting the X dimension and bar width growth or loss.

Programmer�s Example

These principles can be reduced to the following rules for digital bar code design files:

a) Convert the desired magnification or X dimension to a narrow element width in pixels rounded down to the nearest integer and select a wide:narrow ratio that will result in an integer number of pixels in the wide elements.

b) Determine the number of pixels corresponding to the desired compensation for uniform bar width growth and round up to the next larger integer.

c) Apply the above results to determine the pixel count of every bar and space in the symbol.

EXAMPLE

Using digital bar code design files with a printing device with 24 dots per mm, create a 0,27 mm X dimension symbol with 2,5 : 1 wide:narrow ratio and with 0,06 mm of bar width reduction.

The narrow element size is 24 dots/mm 0,27 mm = 6,5 pixels, which is rounded down to 6 pixels per narrow element.

The wide element size is therefore 6 x 2,5 = 15 pixels.

The bar growth compensation is 0,06 mm 24 pixels/mm = 1,4 pixels, which is rounded up to 2 pixels.

This process results in the following pixel count for bars and spaces as illustrated in Table B.1.

Table B.1 � Correcting Pixels for Imaging Resolution and Bar Width Reduction

Pixel Count

Bars Spaces

Narrow elements 4 8

Wide elements 13 17

B.3.2 Guidance to users of pixel-based printing software

When printing a symbol for the first time on a printing system consisting of the bar code printing software and the printing device, a user should verify according to ISO/IEC 15416 that the printed symbol meets the required print quality grade and X dimension. If the resulting symbol does not achieve the required symbol quality grade the user may need to increase the X dimension or change the bar width growth or loss. If the X dimension is increased the user should verify that the minimum quiet zones are maintained. This process may need to be repeated until the required symbol grade is achieved. Not all printing systems are capable of producing acceptable symbols at small X dimensions.

14 © ISO/IEC 2007 � All rights reserved

B.3.3 Process control considerations

For process control purposes, the assessment of average bar width gain or loss, and the application of corrective action to reduce this, are appropriate. The "decodability" parameter measured in accordance with ISO/IEC 15416 is affected by systematic bar width gain or loss.

© ISO/IEC 2007 � All rights reserved 15

Annex C (normative)

Symbology identifier

The symbology identifier allocated to Code 39 in ISO/IEC 15424, which may be added as a preamble to the decoded data by a suitably programmed bar code decoder, is

]Am where

] represents ASCII character 93;

A is the code character for the "Code 39" symbology;

m is a modifier character the value of which from Table C.1 below represents the applicable, active options.

Permissible values of m are 0, 1, 3, 4, 5, and 7.

Table C.1 � Values of m for Code 39

Value of m Option

0 No check character validation nor full ASCII processing; all data transmitted as decoded

1 Modulo 43 symbol check character validated (as per A.1.1) and transmitted

3 Modulo 43 symbol check character validated (as per A.1.1) but not transmitted

4 Full ASCII conversion performed; no check character validation

5 Full ASCII conversion performed; modulo 43 check character validated and transmitted

7 Full ASCII conversion performed; modulo 43 check character validated but not transmitted

This information should not be encoded in the bar code symbol, but should be generated by the decoder after decoding and transmitted as a preamble to the data message.

16 © ISO/IEC 2007 � All rights reserved

Annex D (informative)

Example of application-defined parameters

D.1 Quality grade example

A minimum quality grade in accordance with ISO/IEC 15416, including the measurement aperture and light wavelength to be used, in the form

1,5 / 10 / 660 where

1,5 is the overall symbol quality grade;

10 is the measuring aperture reference number (in this example 10 thousandths of an inch or 0,25 mm diameter);

660 is the peak response wavelength in nanometres.

By reference to ISO/IEC 15416, the minimum values of measured symbol parameters associated with this overall grade can be determined.

D.2 Example of symbology characteristics

a) Encodable character set: the full alphanumeric character set, exclusive of the special characters.

NOTE This also excludes the full ASCII and control function options.

b) Number of data characters: variable, with a maximum of 16 characters.

c) Symbol check character: modulo 43 symbol check character shall be used and transmitted.

d) Data check character: no additional data check character is required.

D.3 Example of dimensional characteristics

D.3.1 Dimensions

As guidance to the user, the application specification may recommend a value or a range of values of X dimension, having regard to the general application needs and to the availability of suitable symbol production and reading equipment. Non-compliance with any minimum X dimension should not, by itself, be a reason for rejection of a symbol under these standards.

It is recommended for manual scanning that the minimum Y dimension should be 5 mm or 15 % of the symbol length, whichever is greater.

The wide/narrow ratio N (or range of values of N) should be specified.

EXAMPLE X = 0,330 mm (minimum), 0,660 mm (maximum), N = 3,0 : 1, Y = 15 mm.

© ISO/IEC 2007 � All rights reserved 17

D.3.2 Dimensional tolerance

Certain application standards have defined dimensionally-based criteria for symbol evaluation and need to specify a minimum and maximum X dimension. The tolerance, or maximum element width deviation (in millimetres) from nominal, shall be constant for any given symbol and is designated t. This tolerance is defined as:

4 2 27 3 t N X where t is the dimensional tolerance;

N is the wide/narrow ratio;

X is the width of the narrow element in millimetres.

The sum of the widths of elements within a character shall not deviate from the nominal by more than 2t.

18 © ISO/IEC 2007 � All rights reserved

Bibliography

[1] ISO 7064, Information technology � Security techniques � Check character systems

[2] ISO/IEC 16390, Information technology � Automatic identification and data capture techniques � Interleaved 2 of 5 bar code symbology specification

ICS 01.080.50; 35.040

Price based on 18 pages

© ISO/IEC 2007 � All rights reserved