how come barcode scanner can scan barcode upside down with same results..?

Question

When you scan a barcode straight or upside down how come it still comes up with same results....
i thought scanning was identified by the space between stripes.....

Answer 1

Yes. Each barcode (whether it is UPC, EAN, Code 39, etc.) includes a start and stop character. Depending which is encountered first will tell the scanner what direction it is reading the barcode. With that information, the decoder can properly read the symbol.

There is a reference point as in ASCII 232 where as; (oo:oooo) the reference point is (:).

While there still is controversy over who invented barcode and when it was first used, it is generally accepted that Norman Joseph. Woodland and Bernard Silver invented what we know as barcode on October 20, 1949 by filing patent application serial number 122,416 which became Patent Number 2,612,994. In June 1974, one of the first UPC scanners, made by NCR Corp. (which was then called National Cash Register Co), was installed at Marsh's supermarket in Troy, Ohio. On June 26, 1974, the first product with a bar code was scanned at a check-out counter. It was a 10-pack of Wrigley's Juicy Fruit chewing gum.

Answer 2

The machine reads the thickness of the stripes. If they're read backwards, the number appears in the number-storage-register has some characteristic property that lets the computer know that it must be reversed to be valid.

It's important to remember that the action of any electronic device like this is exceedingly fast, and thus a rather complex series of operations can take place in what seems to be an instant. I imagine that before the look-up routine is launched, the scanned number is subjected to a series of tests to see if it is a valid UPC code (if that's the particular application) and if it's been entered backwards. I believe that several scans are entered in succession and compared with each other to make sure that they match. Only then is the inventory computer queried to find the item name and its price.

Answer 3

I think barcodes have special codes at the beginning and end of them that the scanner can identify, and by comparing the position of the start and end codes it finds it can tell if the barcode is upside down or not.

Answer 4

Most barcode symbology have "start" and "finish" characters, so the barcode reader knows which is which. Besides, more than one bar makes up a single character. :)

Answer 5

Its all in the coding, some stripes are coded to tell which way the object was scanned.

Answer 6

It can tell by the thickness of the first and last strip which way to read from.

Answer 7

hard matter. look on to bing and yahoo. it will help!