A "Quick Response" or QR code is an image that can be decoded into an text. It's like a two-dimensional barcode. Here's an example:
Scanning this picture resolves into the URL of this blog: http://castfortwo.blogspot.com .
This kind of pictures are typically used for tagging. Add the QR code picture to a thing, take a picture of the thing, decode the picture on the thing and there's the text. For example, a link to a website with product information.
You can make your QR code yourself here : http://qrcode.kaywa.com/
Using the Google Chart API, you can also generate QR codes. The URL
generates a QR code for "Hello World":
Changing the parameter chl to the URL of this blog:
Every BBC programme has also an QR code. Just add /qrcode to the URL.
For example, the URL of the Top Gear programme is:
Adding /qrcode gives:
which render to:
There are several free applications on the iphone that can decode QR codes:
Several other mobile phones have such application to.
The BBC has even succeeded in tampering the QR code for the bbb.co.uk/programes URL such that the BBC text is clearly readable: