Bar Codes

Bar codes come in many shapes and sizes. Common 1-Dimensional bar codes use lines of black on a white background to encode data. Postnet, which is used by the U.S. Postal Service, uses bar height to encode data instead. Most U.S. state drivers licenses use a 2-Dimensional bar code like PDF-417 to enable them to encode lots of data in limited space. Special 2-D bar code scanners are required to read 2-D bar codes.

The coding formats vary from simple to complex. Some bar code standards also print the encoded values above or below the bar codes.

Bar Code Standards

There are many competing standards for bar codes, including:

Bar Code	Size	Data Type	Usage
UPC-A	12	Numeric	Point of Sale in the United States
UPC-E	8	Numeric	Compressed form of UPC-A
EAN	13	Numeric	Point of Sale outside of the United States and books globally
EAN-8	8	Numeric	Compressed form of EAN
Code 11	12	0-9 and -	CLLI Codes for telecom equipment
Code 39 / Code 3 of 9	Variable	0-9, A-Z, <space>, -, +, ., $, /, %
Code 93	Variable	0-9, A-Z, <space> -, +, ., $, /, %	Compressed form of Code 39
Code 128	12	Alphanumeric
Standard 2 of 5	Variable	Numeric	Airline tickets and photo finishing
Industrial 2 of 5	Variable	Numeric
Interleaved 2 of 5 (I 2/5) & ITF-14	Variable	Numeric	Manufacturing, warehouse, air cargo
Code 128	Variable	128-bit ASCII characters
UCC/EAN-128	Variable	128-bit ASCII characters	Store coupons and EDI shipping labels
Codabar	Variable	0-9 and -, $, :, / , ., +	Libraries, blood banks, package delivery
Plessey	Variable	0-9 and A-F	Retail grocery shelf marking and libraries
Postnet	10	Zip Codes	Zip codes on letters
Pharmacode	Variable	Numbers from 1 to 8190	Packing control systems
DataMatrix	Variable	256-bit ASCII characters	Manufacturing
MaxiCode	93	256-bit ASCII characters	UPS (United Parcel Service)
QR Code	1520	Alphanumeric	Manufacturing
PDF-417	Variable	256-bit ASCII characters	Drivers Licenses

The "Size" column above is the raw numbers of characters of storage space. Checksums reduce the amount of usable space and compression increases the amount of effective space.

UPC-A Bar Codes

UPC-A is the most common bar code standard in the United States, because it is printed on almost everything we purchase. UPC-A encodes:

Digits Purpose

6 Manufacturer number

5 Product number

1 Check digit

EAN Bar Codes on Books

Books, even in the United States, are labeled with EAN bar codes. Books actually have two bar codes side-by-side.

The bar code on the left encodes the ISBN and the bar code on the right encodes the suggested retail price of the book:

Digits Purpose

3 EAN County Code -- Always "978" for "Bookland"

9 The first 9 digits of the ISBN

1 Check digit

Digits Purpose

1 The number 5

4 The suggested retail price

UPC and UCC/EAN 128 Bar Codes on Coupons

Coupons also contain two bar codes, the first encoded with UPC and the second encoded with UCC/EAN 128.

Digits Purpose

1 NSC (Number System Character), always 5

5 Manufacturer number

3 Product family code

2 Redemption value

1 Check digit

Digits Purpose

1 NSC (Number System Character)

5 Offer code

4 Expiration date (MMYY)

The Future of Bar Codes

Because of the significant difficulties associated with replacing a bar code system in any production environment, the number and variety of competing bar code systems is not likely to be reduced in the near future.

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