On a barcode scanner

Years ago, I was crazy enough to take a job for an inventory taker. They go in as an independent company to a store after it's closed (usually), and go through all the merchandise to see what's there. By comparison to records, they can also see what isn't there. We used a shoulder carried barcode scanner to flash a red laser light onto the barcode. This detects and records the sku code. I supposed it's inefficient in a way, to pay lots of people (for big stores) to spend hours late at night doing this, but of course with shoplifting the problem it is, stores don't have all of the merchandise their sales records indicate they should have still in stock.