Barcode scanners turn a pattern of black and white stripes into product information that a computer can use. This matters because stores need a fast, reliable way to identify millions of items at checkout, in warehouses, and during inventory counts. A scanner does not read the printed price directly, it reads an identification number encoded in the barcode.
The register then uses that number to find the item name and price in a database.
A laser scanner shines light across the barcode and measures how much light reflects back from each stripe. White spaces reflect more light, while black bars absorb more light, creating an electrical signal that can be converted into 1s and 0s. Camera-based scanners take an image of the barcode and use software to locate the stripes and decode the pattern.
After decoding a UPC or EAN number, the checkout system sends a database request and displays the correct price on the register screen.
Key Facts
- Black bars absorb more light, while white spaces reflect more light.
- A scanner converts changes in reflected light into an electrical signal.
- Digital systems represent data using binary digits: 0 and 1.
- UPC-A barcodes usually encode 12 digits, including a check digit.
- EAN-13 barcodes usually encode 13 digits, including a check digit.
- Item lookup process: scan barcode, decode number, search database, return product name and price.
Vocabulary
- Barcode
- A printed pattern of bars and spaces that encodes a number or other data.
- Scanner
- A device that reads a barcode by detecting reflected light or analyzing a camera image.
- Binary
- A number system that represents information using only two symbols, 0 and 1.
- UPC
- A Universal Product Code used mainly in North America to identify retail products.
- Check digit
- A final digit calculated from the other digits to help detect scanning or typing errors.
Common Mistakes to Avoid
- Thinking the barcode stores the price, which is wrong because most barcodes store a product identification number and the price comes from the store database.
- Assuming the scanner reads only the black bars, which is wrong because it detects the pattern of both dark bars and light spaces.
- Covering part of the barcode and expecting a normal scan, which is wrong because missing stripes can change the decoded number or prevent decoding.
- Confusing laser scanners with camera scanners, which is wrong because lasers measure reflected light along a scan line while camera scanners analyze an image.
Practice Questions
- 1 A scanner samples 95 stripe positions across a barcode. If 38 positions are dark and the rest are light, how many positions are light?
- 2 A store scans 240 items in 30 minutes at self-checkout stations. What is the average scanning rate in items per minute?
- 3 A product scans correctly but the register shows the wrong price. Explain whether the likely problem is the barcode, the scanner, or the database, and justify your answer.