QR code is one of the most popular types of two-dimensional barcodes. The QR code was designed to allow its contents to be decoded at high speed. QR codes are a great way to share information like website URL, text and contact info. They can be scanned using your camera equipped device and a proper QR code processing app which is available for android as Barcode Scanner which is free application, download it from here and for iphone there is another app for reading QR Code os QR Reader for iPhone, you can install it from here
Now just in case, if you want to read or decode a QR code printed on a paper with your computer, you can now do it after installing a adobe air based application on your windows, mac or linux computer. This application is called QRreader which allows you decode QR code and then displays the contact info, text or redirect you to the URL hidden inside the QR Code.
In order to decode the code, you will first need to print the QR Code and then hold the part of paper which has the code printed in front of your webcam while running the application to decode the qr code, follow the step by step procedure below.
How to use QRreader:
1: Make sure you have a working webcam and Adobe AIR installed.
2: Download and install QRreader.
3: Get a scan-able QR code (generated on a device, or printed on some object or paper)
4: Hold up the QR code to your webcam. Make sure your webcam can see the entire code, and that your code is evenly lit.
5: If your webcam sees the code, the white brackets will turn red. Then you will hear a *beep* sound once the code has been read properly
[ Source dansl ]