Index.
Basic terms	Symbology	Continous,Discrete	Module
Quiet zone	Check char	Add-on 2 or 5 digits	Element
Error correction	Start/Stop symbol	Reed Solomon error correction	Omni-directional,Bi-directional
Human readable text	Multirow symbology	Advantages	Problems
EAN countries table		Sample barcode-structure image

Basic terms about barcodes.

Bar codes are like a printed version of 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 UPC symbology was designed for identifying retail and grocery items and PostNET was designed to encode ZIP Codes for US Postal Service.

Barcode symbologies was created for easy using with computers as input device. Reduce human errors by input goods number to computer or money-chest. This linear barcode symbologies have one trouble : small capacity, because more chars is bigger width of barcode and scanner have some trouble. Capacity of linear barcodes is about 10-20 chars, than is better 2D or stacked barcode.
In last years was created barcode symbologies with more information, 2D barcodes with capacity about 2,000 - 7,000 chars.
First impulse was created with Automotive Industry Action Group (AIAG)in 1984 year, defined standard Code39 with Piece number,Quantity,Developer and Serial number.
First 2D barcode was created in year 1988 by Intermec Corporation, assigned as Code49.

What is Bar Code?

Bar code is a pattern of bars and spaces which represent numbers, letters or characters. Code 39, for instance, has a unique pattern. Code 3 of 9, as it is sometimes called, derives its name from the way in which the pattern is created. Each character has nine elements (five bars and four spaces) and three of them are fat.

Why Use Bar Code?

Bar codes are accurate. They eliminate manual data entry errors. Research has shown that the error rate due to bar code misreads is less than one thousandth of one percent. Tests have shown that bar coded information had a throughput accuracy rate of 1 error in 10,000,000 characters. Compare that to keyboard entry error rates of 1 error in 100 characters.

Bar codes speed data entry. Even with a simple wand, a bar code can be scanned in a fraction of the time it takes to enter the information manually. CCD and laser scanners are also available for even faster data entry.

Bar codes can be produced easily and cheaply. Bar codes can be printed on most computer printers, for the cost of ink and paper. Even a low cost dot matrix printer can produce bar codes of adequate quality.

Symbology standard must contain:

A definition of the width of the bars and the spaces
A method to define each character that is encodable (whether numeric only or full ASCII)
The start and stop characters
Any check character support built in
Any free space needed around the symbology to allow for a clean decode

Continous barcode, Discrete barcode.

Discrete symbologies consist of unique bar and space patterns for each character. Continuous codes cannot be separated into individual characters.

Continuos barcode is barcode, where last module is nearest to next char. Between coded chars isn't space, but this space is part of coded char. Last char ends with space and next char begin with bar.
Discrete barcode must have between two chars some space, because char start and end with bar, code must have between two chars one or more space.

Module.

Module is minimal size of barcode piece. For linear barcodes this is line or space with one pixel size (can be zoomed 2,3,4,5 x), for 2D barcodes is this rectangle with integer width and height. Normally is height of rectangle equal width, because rectangle :-) But some exeption are possible...

Quiet zone.

Quiet zone is free zone around barcode. Some barcodes needs this zone on left and right side, no in top and bottom (linear barcodes). This zone is needed for good reading by scanners, because all images, text, lines nearest barcode can make mistake. This zone is for each barcode symbology different, currently about 0.5-1 cm.
Some barcode types not need quiet zone (2D barcodes), this barcode symbologies have installed error correction algorithms, some bad part of barcode image, bad line across barcode, destroyed part of barcode is no problem :-)
2D barcodes can repair 5%-95% of destroyed part, if you have only one half barcode image, no problem, readable ...

Check char (checksum).

Check char is one or more chars (some symbologies use one, some two check char digits) added to end of coded string, before stop char. Barcode scanner after reading barcode use some algorithm, calculate data from string and compare with last char. Is equal, reading is good, if no, not read this barcode, because is destroyed.
Calculation algorithms is more:

Modulo 10 - used in all EAN,ISBN,ISSN,ISMN,UPC barcodes
Modulo 11 - used in Code 11
Modulo 107 - used in Telepen
Good is Reed Solomon error correction - used in 2D barcodes. Added some redundantion data to barcode for error correction. You can have only part of barcode, destroyed barcode and error correction solve your problem.
Error correction mode can be set from 5% to 95%, highest error correction level make of course smallest coded data size, but make this barcode very secure. 5% level is good, but you make barcode only with small damage, 95% is very good after damage, but more information is error correction as data :-(

In all our software products if is needed check digit and user cannot include this in barcode (some example EAN-8 only 7 digits, or 8th digit is bad) is check digit calculated automatically.

Add-on 2 or 5 digits

Barcode symbologies based on EAN code (EAN 8-, EAN-13, UPC-A, UPC-E, JAN, ISSN, ISMN, ISSN) can contain 2 of 5 additional digits after main barcode. In your software you must select this digits from main symbol using one space.
For example : EAN-8 symbol "1234567 12345" is Ean-8, 8th digit is chcecksum, calculated automatically, "12345" is add-on symbol. Printed barcode contain 13 digits, 8th is checksum.

Element.

For 1D barcodes (EAN,UPC,Code39,Code93,...) is one element one pixels. Bit "1" is black line, bit "0" is white space. If you need largest barcode (on laser printer is one pixel very small :-) ), you can increase all element, but good is all elements multiplicate with same coefficient. Barcodes have some printer tollerance, but some 30-40% is maximum. If single line is 10 pixels width, and simple space 11 pixels, this is good. But if simple space is in width 16 pixels, bad. Barcode unreadable.
For 2D barcodes is width and height of element equal. And all 2D barcodes contain error correction algorithm for remove errors.

Error correction.

See Check char. For 1D (linear) barcodes is used check char added after last coded char, before stop char. This char is compared with barcode scanner with all others characters, calculated and if not equal, barcode is bad. If yes, all is O.K. 1D barcodes have troubles with reading in 100.000-1.000.000 barcodes
Better is 2D code, because there is more amount of data, uses better algoritms. To barcode are added some additional data for repair damaged data. This algorithms can correct 5-95% of damaged data. Error correction level user can set, but if better error correction level, smaller data can you code, because barcode include more error correction information. In 95% error level you need only 1/5 barcode and no problem with reading.

Symbology	Worst Case	Best case
Datamatrix	10.5M	612.9M
PDF417	10.5M	612.4M
Code128	2.8M	37M
Code 39	1.7M	4.5M
UPC	394K	800K

Start/Stop symbol.

Start symbol is begin of barcode, only in 1D barcode. Before this symbol must be quiet zone. This indicate barcode symbology. After this symbol continues barcode text.
Stop symbol is last symbol in barcode. Before this symbol can be checksum. After stop symbol must be quiet zone for easy reading of barcode, no images, lines, text.

Reed Solomon alghorithm.

Reed-Solomon codes are block-based error correcting codes with a wide range of applications in digital communications and storage. Reed-Solomon codes are used to correct errors in many systems including:

Storage devices (including tape, Compact Disk, DVD, barcodes, etc)
Wireless or mobile communications (including cellular telephones, microwave links, etc)
Satellite communications
Digital television / DVB
High-speed modems such as ADSL, xDSL, etc.

Typical scheme: DATA -> REED-SOLOMON ENCODER -> TRANSMISSION (with errors, of course) -> REED SOLOMON DECODER-> DATA WITHOUT ERRORS (if possible), easy :-)
For barcode : Reed-Solomon error correction adds to barcode additional char. This chars is very good if barcode is damaged. Correct problems and barcode is good. Nice. But problem is in error correction level.
5% error correction is small, only small part of barcode can be damaged. 95% is very good, but additional informations is large as coded data :-(, 50% this gold road...
Further reading : In this paper we have deliberately avoided discussing the theory and implementation of Reed-Solomon codes in detail. For more detail please see the following books:

Wicker, "Error Control Systems for Digital Communication and Storage", Prentice-Hall 1995
Lin and Costello, "Error Control Coding: Fundamentals and Applications", Prentice-Hall 1983
Clark and Cain, "Error Correction Coding for Digital Communications", Plenum 1988
Wilson, "Digital Modulation and Coding", Prentice-Hall 1996

Omni-directional, Bi-directional reading

Easy - Omni-directional barcodes can be readed only from one side - from left to right. Barcode must begin with start character and ends with stop character.
Bi-directional can be readed from left to right or from right to left. Start and stop code reader recognize. User not must barcode turn as needed. Barcode can start with stop character and stop with start character. This is good.

Human readable text.

Human readable text is text under barcode. This is good, if barcode is damaged and user must write to computer barcode manually. Another meaning not have. Barcode reader read good without this impossible things, for reader is this not usable. But human read better digits than lines and spaces... Some barcode symbologies not have human readable text. 2D barcode is very good example : can you write to computer 7 kilobytes of text ? If human readable text is not printed, no problem with reading, but only cashier can have some troubles, if barcode is not readable, you can't read code value.

Multirow symbology.

Multirow symbology is space before 1D (linear) and 2D symbology. We need more chars coded, but space is small... No problem. We divide one long barcode to more small and place one under other. This barcode isn't 1D, because each line is different, but not 2D, because some lines are here ...

PDF417
- nice multirow barcode, very good error correction, 3 - 90 rows, all 128 ASCII codes, 8 bit binary data
- Bi-directional encoding : Yes
- error correction level 0 - 8
- Additional options : MacroPDF417,MicroPDF417,...
- Code16K - 2 - 16 rows, 5 chars per row, additionally up to 107 16-row symbols can be concatenated together to allow encoding of up to 8025 characters or 16050 digits.
- Contain complete 128 ASCII character set

Advantages

Easy input to computer or electronic cash register, reduce human errors and make input speed and easy.
Easy print - for simple 1D code is dot printer good, but for better print is needed inkjet or laser printer
1D barcodes is very good for small codes- 10-15 chars, in large size have scanner troubles with reading, because difference between code and scanner is large or not all code is placed to scanner place.
2D barcodes is very capable - on 1 square inch no problem 1.000-2.000 chars
Error correction - 1D barcodes includes checksum, indicate bad barcode. 2D barcodes uses error correction methods, eliminate destroyed or damaged barcodes, of course not in 100 %, but very good.
Capacity of coded tetx in 2D barcode is very high - 2.000 - 7.000 bytes per 2-3 square inch
2D barcodes are very small in size, you can read this barcode from any position, no Omni-directional
Multistacked symbols is good, because you can read from top to bottom, or from bottom to top, or random. Barcode is completed, because each row contain row number.
2D symbologies scan barcode as one entirety, no problem with rows and columns

Problems

Matrix printer - for barcode no. Very small DPI, best is laser printer.
2D barcodes - not easy for implementation - you need laser printer, dot printer is lost :-(
All barcodes 1D, Stacked,2D have some problem. InkJet printer is not good. If you ave hands on watter or if your document is on moisture, ink can be damaged, you have problem. On laser printer no.
Error correction methods - not easy and more data needs
1D barcodes have smaller reliability as 2D, Human make error 1:300 (very bad), speed : small.
1D barcode is readed bad in 1:1.000.000, 2D barcode around 1:100.000.000,speed is very good, try write 7.000 chars per 2-3 second :-)
1D barcodes must be readed using laser across all width barcode. If some line is not in laser, is problem
2D barcode isn't some world standard, you can code all info. Ean 13, Ean 8, UPC, ITF, RSS is standard, you have security, that two different goods on the world not have same barcode. This code allocate EAN, EAN Swerige EAN Slovakia

EAN COUNTRIES

First two or thee digits in the EAN8 or EAN13 assign country:

00..130	U.S.A. & Canada	640..649	Finland
200..290	In-store numbers	690..692	China
300..370	France	700..709	Norge
380	Bulgaria	729	Israel
383	Slovenia	730..739	Sweden
385	Croatia	740..745	Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, Panama
387	Bosnia-Herzegovina	746	Republica Dominica
400..440	Germany	750	Mexico
450..459	Japan	759	Venezuela
460..469	Russian Federation	760..769	Suisse
471	Taiwan	770	Colombia
474	Estonia	773	Uruguay
475	Latvia	775	Peru
477	Lithuania	777	Bolivia
479	Sri Lanka	779	Argentina
480	Philippines	780	Chile
482	Ukraine	784	Paraguay
484	Moldova	786	Ecuador
485	Armenia	789	Brazil
486	Georgia	800..830	Italy
487	Kazakhstan	840..849	Spain
489	Hong Kong	850	Cuba
490..491	Japan	858	Slovakia
500..509	U.K.	859	Chech
520	Greece	860	Yugoslavia
528	Lebanon	869	Turkey
529	Cyprus	870..879	Nederland
531	Macedonia	880	South Corea
535	Malta	885	Thailand
539	Ireland	888	Singapore
540..549	Belgium & Luxembourg	890	India
560	Portugal	893	Vietnam
569	Iceland	899	Indonesia
570..579	Denmark	900..919	Austria
590	Poland	930..939	Australia
594	Rumania	940..949	New Zealand
599	Hungary	955	Malaysia
600..601	South Africa	977	Periodicals
609	Mauritius	978,979	Books
611	Marocco	980	Refund receipts
613	Algeria	990..999	Coupons
619	Tunisia
622	Egypt
626	Iran

CRC- Cyclic redundance code.

For minimizing the numer of incorrect entries is needed detect any error in input.

Add one or two check digit to code
Problem : add regundad information into message - longer barcode, but barcode id "power", for example in code PDF417 can be destroyed 90% of barcode picture and no problem ... readable. But some data is 10% from image, 90% is restoring data :-(
But this CRC data is very usefull. Bad reading of barcode is about 1:100.000 in code 2/5,Code39.... to 100.000.000 with PDF417 barcode. This is very good.

2 DIMENSIONAL BARCODE

Not "line barcode", two dimensional barcode, printed as matrix of some square elements. This code can contain more data (for PDF417,QR Code, Matrix, Aztec code) is no problem 4.000-7.000 bytes with error correction. Here you can code digits,alpha chacctaers, bytes, music, photo ....
Error correction can be set from 5% to 95% of coded chars. Of course, if you set error correction to 95%, barcode can be destroyed, three from four corners bad, ... and barcode is readable. But problem is in one : 95% of data area is redundancy code :-( , you don't need, when barcode is OK, only if very destroyed.
5% error level is good, if ypur barcode is safe, no troubles with reading. You have more and more capacity for data and only small redundance code for solve troubles. But if troubles come, you need this data. If big troubles, you need more this data and can be big troubles. But 2D barcodes uses error correction systems, no problem with reading. Bad reading is 1:100.000.000, this is good.

Printing techniques

Thermo transpher printer :
- Very precise technology
- Small dot size, very good text and line quality
- Resolution : 200 DPI or more. Good.
Laser printer :
- DPI : very good, 200-300 DPI is no problem
- Problem is in small images or barcodes, because medium is damaged if you immediatelly merging out of the paper treated by head.
  Continuous quality is a problem.
Matrix printer :
- For barcode is this printer only good joke :-)
- Verty small DPI=problems
- not allow equal continuing quality
- Not recomented for good barcode printing, sorry
Ink Jet Printer :
- Depended on DPI ...
- Depended on print media, ink and process....
- Integration would need great experiences, problem one : moisture. Text, image or barcode is destroyed.

Sample barcode - explain structure of barcode

Sample of UPC code
UPC barcode = structure

Index.