[an error occurred while processing this directive]
BBC News
watch One-Minute World News
Last Updated: Wednesday, 20 September 2006, 11:44 GMT 12:44 UK
How do 2D barcodes work?
The Magazine answers...

Online post
The barcodes hold far more data
We can now buy postage online, instead of using stamps, but how do two dimensional barcodes work? And what's to stop you photocopying them?

No queuing at the Post Office for a stamp, it's a dream come true.

Customers can now pay for postage by credit card over the internet for first-class, second-class, recorded, special and international deliveries.

Each item of mail is given a two dimensional (2D) barcode, printed off onto an envelope and regular mail can then be posted in a post box. Recorded and special delivery items must still be taken to a Post Office.

And forget thoughts of photocopying - the barcodes cannot be used again as each is unique and is scanned when it reaches a sorting office.

Dots and lines

A single pack of chewing gum was the first retail product sold using a barcode and scanner, at a supermarket in Troy, Ohio, in June 1974. It had a conventional linear barcode, so how do the newer 2D ones work?

Question mark
A regular feature in the BBC News Magazine - aiming to answer some of the questions behind the headlines
These were first introduced by US firm Intermec Corporation in 1988 and hold far more data in a small space, typically 1,000 characters compared with 20 characters on a traditional barcode.

All barcodes encode a string of characters as a set of bars and spaces. Linear barcodes get wider as more data is encoded, but 2D ones encode data in both the horizontal and vertical dimensions.

Visually the barcodes look like lots of small black and white squares in an area similar to the size of a postage stamp.

Unlike standard barcodes, which depend on links to a larger database, they contain a sort of mini-database themselves, which includes information on the product and can be encrypted.

As more data is packed in, the size of the barcode can be increased in both the horizontal and vertical directions, which makes it much easier to manage the shape for scanning. Data can even be read if part of the barcode label is damaged.

Other ways 2D barcodes are being used include Smart Ovens, produced by Samsung. They read special 2D barcodes - known as SmartCodes - on food packaging which tell the oven how to cook the food, including the correct temperature, microwave power and time.

The BBC is not responsible for the content of external internet sites

Has China's housing bubble burst?
How the world's oldest clove tree defied an empire
Why Royal Ballet principal Sergei Polunin quit


Americas Africa Europe Middle East South Asia Asia Pacific