A barcode reader works by directing a laser across the bar code and measuring the amount of light that is reflected back to its photosensors. A scanner, imager or reader will act just like any other...
Are you asking how many barcode types there are? This site gives a bunch of different types and shows the differences between them: http://www.barcodefaq.com/BarcodeMatch/index.html
Biometrics is an advance method over the traditionally used bar codes.Biometrics comprises methods for uniquely recognizing humans based upon one or more intrinsic physical or behavioral traits. In...