Barcodes and scanners

[LeedsRhinos]

Why does a barcode scanner read the same info on a barcode regardless whether the scanner is upside or not, when the barcode isn't symetrical from both sides.
Hope this makes sense, I know what I mean !

TIA

[dzug]

Part of the barcode will indicate which way is 'up' so the reader will just invert what it sees if necessary.

[heathfield]

The scanner reads the label and does a number of check calculations, described here. If the calculations don't work out, the scanner tries again, with the beam moving backwards and forwards, until a proper checksum result is obtained. All this takes place very, very, quickly.

[pieman65]

dina