what is QR code ?
QR code is a type of matrix barcode invented in 1994 by Japanese company Denso Wave. A barcode is a machine-readable optical label that can contain information about the item to which it is attached. In practice, QR codes often contain data for a locator, identifier, or tracker that points to a website or application. QR codes use four standardized encoding modes to store data efficiently; extensions may also be used .