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:

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.